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How Long Would It REALLY Take Us To Reach Jupiter · Boring Science

• 0:00
  Speaker 1: Jupiter is about 365 million miles away at its closest
• 0:04
  Speaker 1: point to Earth. And if you ask how long it
• 0:07
  Speaker 1: would take to get there, the answer you'll find most
• 0:10
  Speaker 1: often is somewhere between two and six years. People read that, nod,
• 0:16
  Speaker 1: file it away, and move on. A number got stated.
• 0:21
  Speaker 1: The question feels answered. But that range, two to six years,
• 0:27
  Speaker 1: is one of the most misleading summaries in all of
• 0:29
  Speaker 1: popular science because every number inside it is technically correct
• 0:35
  Speaker 1: and almost completely useless without context. What spacecraft? Launched when?
• 0:43
  Speaker 1: Does it need to slow down when it gets there?
• 0:46
  Speaker 1: Or is it allowed to just blow past? Is the
• 0:50
  Speaker 1: crew biological? Or is it a machine that doesn't care
• 0:54
  Speaker 1: how long the trip takes? The answer changes dramatically depending
• 0:58
  Speaker 1: on every single one of those questions, and most people
• 1:02
  Speaker 1: have never been asked any of them. Here is what
• 1:05
  Speaker 1: makes this worth paying attention to. Jupiter is not just
• 1:10
  Speaker 1: a big planet sitting out there in the dark. It
• 1:13
  Speaker 1: is the largest object in the solar system after the
• 1:16
  Speaker 1: Sun itself. It has at least 95 known moons. Some
• 1:22
  Speaker 1: of those moons are bigger than the planet Mercury. One
• 1:26
  Speaker 1: of them, Europa, has a liquid ocean buried under its ice,
• 1:31
  Speaker 1: an ocean that contains more water than every ocean on
• 1:35
  Speaker 1: Earth combined. And the scientific community considers it one of
• 1:40
  Speaker 1: the most promising places in the entire solar system to
• 1:43
  Speaker 1: look for life. We have sent exactly a handful of
• 1:48
  Speaker 1: spacecraft to Jupiter in all of human history. A handful.
• 1:54
  Speaker 1: The first one arrived in 1973. Given what might be
• 1:59
  Speaker 1: waiting out there, the fact that we've barely looked is extraordinary.
• 2:04
  Speaker 1: If you find comfort in these gentle explorations of space
• 2:08
  Speaker 1: and science, I'd be grateful if you'd consider subscribing and
• 2:12
  Speaker 1: giving this video a like. And yet for all of that,
• 2:21
  Speaker 1: The travel time question still gets flattened into a single
• 2:24
  Speaker 1: shrug of a number. Two to six years. As if
• 2:29
  Speaker 1: the difference between two years and six years is a
• 2:32
  Speaker 1: rounding error. As if the reasons behind that difference don't
• 2:37
  Speaker 1: reveal something genuinely strange about how space travel actually works.
• 2:43
  Speaker 1: The real story is not a number. It is a
• 2:47
  Speaker 1: set of trade-offs that spacecraft engineers lose sleep over, and
• 2:52
  Speaker 1: those trade-offs explain why some missions race to Jupiter in
• 2:56
  Speaker 1: just over a year, while others take the long way
• 2:59
  Speaker 1: around and arrive half a decade later. The New Horizons
• 3:04
  Speaker 1: spacecraft reached Jupiter in 13 months. The Galileo spacecraft took
• 3:10
  Speaker 1: six years. Both of those statements are true. They describe
• 3:16
  Speaker 1: journeys to the same planet. The difference between them is
• 3:19
  Speaker 1: not luck or budget. It is physics, timing, orbital mechanics,
• 3:25
  Speaker 1: and one fundamental question. Did the spacecraft need to stop?
• 3:30
  Speaker 1: Because in space, slowing down is just as hard as
• 3:34
  Speaker 1: speeding up. And the fuel cost of breaking into orbit
• 3:38
  Speaker 1: around Jupiter is enormous. New horizons didn't break. It flew
• 3:43
  Speaker 1: through the Jovian system like a bullet through an open
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  Speaker 1: window and kept going. Galileo had to stop, and stopping
• 3:52
  Speaker 1: required a different kind of journey entirely. Slower, longer, stranger,
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  Speaker 1: looping back past Venus and Earth twice before it had
• 4:03
  Speaker 1: enough speed to make the trip work at all. None
• 4:06
  Speaker 1: of this gets explained when someone says two to six years.
• 4:11
  Speaker 1: None of it gets explained when a headline says, we
• 4:14
  Speaker 1: could reach Jupiter in under two years. Every one of
• 4:18
  Speaker 1: those claims is sitting on top of a set of
• 4:21
  Speaker 1: assumptions that the headline never mentions. The real answer depends
• 4:26
  Speaker 1: on a set of questions most people have never been asked.
• 4:30
  Speaker 1: And the moment you start asking them, the journey to
• 4:34
  Speaker 1: Jupiter gets a lot stranger. The first thing to understand
• 4:38
  Speaker 1: about traveling to Jupiter is that the distance between Earth
• 4:41
  Speaker 1: and Jupiter right now is not the same as it
• 4:44
  Speaker 1: was last year and it will not be the same
• 4:47
  Speaker 1: next year this is not a minor variation the difference
• 4:52
  Speaker 1: between Jupiter at its closest and Jupiter at its farthest
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  Speaker 1: is nearly 240 million miles that is more than twice
• 5:01
  Speaker 1: the distance from Earth to the Sun when people give
• 5:05
  Speaker 1: you a single number for how far away Jupiter is
• 5:09
  Speaker 1: they are averaging across a moving target. And that average
• 5:14
  Speaker 1: hides something that matters enormously the moment you try to
• 5:18
  Speaker 1: actually go there. Here is the picture. Earth orbits the
• 5:22
  Speaker 1: Sun once every 365 days. Jupiter orbits the Sun once
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  Speaker 1: every 11.86 Earth years. Both orbits are elliptical, which means
• 5:35
  Speaker 1: neither planet traces a perfect circle. They speed up when
• 5:40
  Speaker 1: they are closer to the Sun and slow down when
• 5:43
  Speaker 1: they are farther away. Earth moves much faster, completing nearly
• 5:48
  Speaker 1: 12 full orbits for every single orbit Jupiter completes. So
• 5:54
  Speaker 1: the gap between the two planets is constantly opening and closing,
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  Speaker 1: never steady, never fixed, running through its full range on
• 6:03
  Speaker 1: a cycle that repeats roughly every 13 months. At their
• 6:07
  Speaker 1: closest point, When Earth swings between the Sun and Jupiter
• 6:11
  Speaker 1: in what astronomers call an opposition, the two planets are
• 6:16
  Speaker 1: about 365 million miles apart. That is the number people
• 6:21
  Speaker 1: tend to reach for when they talk about the distance
• 6:24
  Speaker 1: to Jupiter, because it is the smallest number and it
• 6:28
  Speaker 1: sounds the most reachable. At their farthest point, when Jupiter
• 6:34
  Speaker 1: is on the opposite side of the Sun from Earth,
• 6:37
  Speaker 1: that gap stretches out to about 601 million miles. The
• 6:43
  Speaker 1: average across the full range of orbital positions works out
• 6:48
  Speaker 1: to roughly 444 million miles. Every one of those numbers
• 6:55
  Speaker 1: is technically correct. Every one of them tells a different
• 6:59
  Speaker 1: story about how long the journey takes. Think about the
• 7:03
  Speaker 1: Moon for a second. The Moon is not perfectly fixed
• 7:06
  Speaker 1: in distance either, but its variation is small enough that
• 7:10
  Speaker 1: when you are planning a mission, it barely registers as
• 7:14
  Speaker 1: a complication. Apollo crews launched, flew a predictable path, and arrived.
• 7:21
  Speaker 1: The geometry was never going to dramatically betray them. Jupiter
• 7:26
  Speaker 1: is nothing like that. Jupiter is a target sliding steadily
• 7:30
  Speaker 1: across the solar system. And whether you catch it close
• 7:34
  Speaker 1: or catch it far changes your travel time by years,
• 7:38
  Speaker 1: not days. Miss the optimal window and you are not
• 7:43
  Speaker 1: dealing with a minor inconvenience. You are dealing with a
• 7:47
  Speaker 1: fundamentally different mission. This is where the synodic period comes in.
• 7:53
  Speaker 1: The synodic period is the time it takes for Earth
• 7:56
  Speaker 1: and Jupiter to return to the same relative positions. And
• 8:00
  Speaker 1: for Jupiter, that number is 398.88 days, just a little
• 8:06
  Speaker 1: over 13 months. What this means practically is that the
• 8:11
  Speaker 1: favourable launch window for a mission to Jupiter opens roughly
• 8:16
  Speaker 1: once every 13 months. The geometry lines up, the distance
• 8:22
  Speaker 1: is manageable, and mission planners have a chance to send
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  Speaker 1: a spacecraft on an efficient path. then the window closes
• 8:31
  Speaker 1: then you wait not a few weeks not a month
• 8:36
  Speaker 1: more than a year before the next reasonable opportunity arrives
• 8:40
  Speaker 1: were you planning a mission and something went wrong on
• 8:43
  Speaker 1: the pad a faulty sensor a software problem an unexpected
• 8:49
  Speaker 1: weather delay if that delay pushes you past the launch
• 8:54
  Speaker 1: window by even a few weeks The orbital geometry has
• 8:58
  Speaker 1: already started working against you. The path that was efficient
• 9:02
  Speaker 1: becomes expensive. You either burn dramatically more fuel to compensate,
• 9:08
  Speaker 1: accept a much longer journey, or wait 13 months and
• 9:12
  Speaker 1: try again. Space agencies have faced this exact scenario. It
• 9:18
  Speaker 1: is not theoretical. The solar system does not hold the
• 9:22
  Speaker 1: window open while the paperwork catches up. jupiter's slow crawl
• 9:27
  Speaker 1: around the sun is part of why this matters so
• 9:31
  Speaker 1: much earth is quick we tear through one full orbit
• 9:35
  Speaker 1: in a year jupiter is almost stationary by comparison grinding
• 9:41
  Speaker 1: through its 11.86 year journey around the sun so slowly
• 9:45
  Speaker 1: that from our perspective it barely moves against the background
• 9:49
  Speaker 1: of distant stars each year Jupiter advances roughly 30 degrees
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  Speaker 1: along its orbital path. Earth laps it again and again.
• 10:01
  Speaker 1: From the surface of Earth, Jupiter appears to drift slowly
• 10:05
  Speaker 1: across the sky over months and years, rising earlier each night,
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  Speaker 1: eventually reaching opposition where it is closest and brightest, then
• 10:16
  Speaker 1: falling back toward the Sun in our sky. before emerging
• 10:20
  Speaker 1: again on the other side. What this means for mission
• 10:23
  Speaker 1: timing is that the geometry is always in motion and
• 10:27
  Speaker 1: the calculations for where Jupiter will be when a spacecraft
• 10:32
  Speaker 1: actually arrives are not simple. You are not aiming at
• 10:36
  Speaker 1: where Jupiter is today. You are aiming at where Jupiter
• 10:40
  Speaker 1: will be in two, three, five years depending on which
• 10:45
  Speaker 1: path you choose. Get the math wrong and you miss,
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  Speaker 1: not by a little, by hundreds of millions of miles.
• 10:54
  Speaker 1: There is another layer to this. At the closest approach
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  Speaker 1: distance of 365 million miles, a radio signal travelling at
• 11:04
  Speaker 1: the speed of light takes about 33 minutes to reach Jupiter.
• 11:09
  Speaker 1: At the farthest distance of 601 million miles, that same
• 11:12
  Speaker 1: signal takes about 53 minutes. Right now, depending on where
• 11:20
  Speaker 1: Jupiter sits in its orbit, those numbers are somewhere in between.
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  Speaker 1: The distance is not just a travel time problem, it
• 11:29
  Speaker 1: is a communication problem, a planning problem, and a fuel problem,
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  Speaker 1: all compressed into one number that changes every single day.
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  Speaker 1: Here is something worth holding in mind. When the Galileo
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  Speaker 1: spacecraft was launched in 1989, mission designers knew they were
• 11:49
  Speaker 1: dealing with a moving target. They didn't aim at Jupiter's
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  Speaker 1: position on launch day. They aimed at a point in
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  Speaker 1: space where Jupiter would be six years later, after Galileo
• 12:02
  Speaker 1: had looped through the inner solar system collecting speed from
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  Speaker 1: Venus and Earth. The spacecraft flew away from Jupiter at first.
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  Speaker 1: toward Venus, back past Earth, out again, all of it
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  Speaker 1: precisely calculated around the fact that Jupiter is never where
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  Speaker 1: you left it. The window problem compounds in a way
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  Speaker 1: that is almost cruel for anything involving a crew. A
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  Speaker 1: robotic spacecraft can launch, coast for years, and arrive without
• 12:34
  Speaker 1: anyone aboard suffering for the delay. Humans don't work that way.
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  Speaker 1: Every day added to the journey is a day of
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  Speaker 1: radiation exposure, food consumption, psychological strain, and bone density loss.
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  Speaker 1: So the launch window is not just a scheduling concern.
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  Speaker 1: For a crewed mission, the launch window is a hard
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  Speaker 1: constraint tied directly to crew survival. The difference between launching
• 13:03
  Speaker 1: at the optimal moment and launching a month late is
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  Speaker 1: not just a math problem. it is a human cost
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  Speaker 1: so when someone tells you Jupiter is 365 million miles
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  Speaker 1: away or 444 million miles or 601 million miles understand
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  Speaker 1: that they are not wrong they are just describing a
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  Speaker 1: single frame of a film that never stops running the
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  Speaker 1: planet is always somewhere in that range always moving and
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  Speaker 1: the distance on the day you launch is only one
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  Speaker 1: part of the calculation before you can calculate how long
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  Speaker 1: the trip takes you have to know when you're leaving
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  Speaker 1: and the answer to that question changes everything that comes
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  Speaker 1: after it the obvious way to reach jupiter would be
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  Speaker 1: to point a spacecraft at it and fire the engines
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  Speaker 1: until you get there and that approach would fail almost
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  Speaker 1: immediately here is the problem Jupiter is not sitting still
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  Speaker 1: waiting for you. It is moving at roughly 29,000 miles
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  Speaker 1: per hour around the Sun, tracing a path that takes
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  Speaker 1: nearly 12 Earth years to complete. Earth is moving too,
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  Speaker 1: at about 67,000 miles per hour, in its own tighter orbit.
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  Speaker 1: By the time any spacecraft you launch today has crossed
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  Speaker 1: hundreds of millions of miles of empty space, Jupiter will
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  Speaker 1: be somewhere completely different than where it was when you left.
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  Speaker 1: If you aim directly at Jupiter's position on launch day,
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  Speaker 1: your spacecraft would arrive at an empty patch of space
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  Speaker 1: roughly where Jupiter used to be. The planet would be
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  Speaker 1: long gone. This is not a small error. We are
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  Speaker 1: talking about a miss of tens of millions of miles,
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  Speaker 1: so the real calculation is not where is Jupiter now,
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  Speaker 1: It is where will Jupiter be in two years, or three,
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  Speaker 1: or five, depending on how fast your spacecraft is moving
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  Speaker 1: and what path it takes. You are not shooting at
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  Speaker 1: a target. You are leading a target, the way a
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  Speaker 1: hunter leads a moving animal, rather than firing where it stands.
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  Speaker 1: Except in this case, the animal is 89,000 miles wide,
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  Speaker 1: moving at 29,000 miles per hour, and your bullet takes
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  Speaker 1: years to arrive. Get the math slightly wrong, and you
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  Speaker 1: miss by a distance that dwarfs the entire inner solar system.
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  Speaker 1: Now here is where it gets stranger. Once you have
• 15:48
  Speaker 1: figured out the right direction, you cannot simply accelerate toward
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  Speaker 1: Jupiter and coast, because in space, there is no friction,
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  Speaker 1: no air resistance, nothing to push against. On Earth, if
• 16:03
  Speaker 1: you throw a ball, it eventually slows down and falls.
• 16:08
  Speaker 1: In the vacuum between planets, a spacecraft moving at 40,000
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  Speaker 1: miles per hour will keep moving at 40,000 miles per
• 16:16
  Speaker 1: hour essentially forever unless something acts on it. That sounds
• 16:21
  Speaker 1: like an advantage. In some ways, it is. But it
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  Speaker 1: also means that whatever velocity your spacecraft has when it
• 16:31
  Speaker 1: approaches Jupiter, is the velocity it will still be carrying.
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  Speaker 1: If you want to stop there, or enter orbit, you
• 16:40
  Speaker 1: have to kill that velocity yourself. There is no atmosphere
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  Speaker 1: to drag against, no runway to roll down. You have
• 16:49
  Speaker 1: to fur, E your engines in reverse and burn fuel
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  Speaker 1: to slow down, the same way you burned fuel to
• 16:56
  Speaker 1: speed up. Slowing down costs exactly as much energy as
• 16:59
  Speaker 1: speeding up. People don't think about this. They imagine getting
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  Speaker 1: to Jupiter as the hard part and arriving as the
• 17:07
  Speaker 1: easy part. It is the opposite of easy. Getting captured
• 17:11
  Speaker 1: by Jupiter's gravity in a controlled way, rather than swinging
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  Speaker 1: past it and flying off into the outer solar system,
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  Speaker 1: requires a massive engine burn at exactly the right moment.
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  Speaker 1: That burn costs fuel. That fuel has to be carried
• 17:29
  Speaker 1: the entire way from Earth. which brings us to the
• 17:33
  Speaker 1: most brutal constraint in all of rocketry. Fuel has mass.
• 17:38
  Speaker 1: Mass requires fuel to accelerate, which means the fuel you
• 17:43
  Speaker 1: need to carry also needs fuel to carry it, which
• 17:47
  Speaker 1: means that fuel needs even more fuel. It spirals. This
• 17:52
  Speaker 1: is the tyranny of the rocket equation, worked out by
• 17:55
  Speaker 1: a Russian schoolteacher named Konstantin Tsiolkovsky in the 19th century.
• 18:02
  Speaker 1: and it has not gotten any kinder since. The equation
• 18:06
  Speaker 1: tells you exactly how much fuel you need to change
• 18:09
  Speaker 1: your velocity by a given amount and the answer is
• 18:13
  Speaker 1: always more than you want it to be. Want to
• 18:17
  Speaker 1: go twice as fast? You don't need twice the fuel.
• 18:21
  Speaker 1: You need exponentially more because every extra pound of fuel
• 18:25
  Speaker 1: you load onto a spacecraft is a pound that itself
• 18:29
  Speaker 1: requires fuel to accelerate and that fuel requires fuel, and
• 18:34
  Speaker 1: the loop keeps tightening. Think about what this means practically.
• 18:40
  Speaker 1: A spacecraft designed to reach Jupiter and enter orbit needs
• 18:45
  Speaker 1: to carry fuel for the initial burnout of Earth orbit,
• 18:49
  Speaker 1: fuel for any course corrections along the way, fuel for
• 18:53
  Speaker 1: the breaking burn at Jupiter, and fuel for everything that
• 18:57
  Speaker 1: comes after. All of that fuel sits on the spacecraft
• 19:02
  Speaker 1: from the moment of launch. The rocket that lifts it
• 19:06
  Speaker 1: off the pad is not just carrying a spacecraft. It
• 19:10
  Speaker 1: is carrying a spacecraft plus years worth of propellant, and
• 19:14
  Speaker 1: the sheer mass of that propellant requires even more fuel
• 19:18
  Speaker 1: just to get off the ground. This is why interplanetary
• 19:23
  Speaker 1: spacecraft are mostly fuel. The science instruments, the computers, the
• 19:29
  Speaker 1: structure itself. Those are a small fraction of what actually launches.
• 19:34
  Speaker 1: The rest is propellant, sitting there, waiting to be burned.
• 19:39
  Speaker 1: What this means for speed is counterintuitive. Going faster requires
• 19:44
  Speaker 1: more fuel. More fuel means more mass. More mass means
• 19:49
  Speaker 1: your engines have to work harder. Your engines working harder
• 19:53
  Speaker 1: burns through that fuel faster, which changes your trajectory. Every
• 19:58
  Speaker 1: decision compounds. And because there is no margin for error
• 20:03
  Speaker 1: across hundreds of millions of miles, small mistakes in the
• 20:07
  Speaker 1: initial calculation do not stay small. They grow. A trajectory
• 20:14
  Speaker 1: error of a fraction of a degree on departure becomes
• 20:18
  Speaker 1: a miss of thousands of miles by arrival. A fuel
• 20:22
  Speaker 1: budget that runs thin before the breaking burn means the
• 20:26
  Speaker 1: spacecraft sails past Jupiter with nothing to stop it. The
• 20:32
  Speaker 1: distances involved punish imprecision in ways that have no equivalent
• 20:37
  Speaker 1: on Earth. This is why the engineers who design interplanetary
• 20:41
  Speaker 1: missions spend years on trajectories before a single component is built.
• 20:47
  Speaker 1: The path matters as much as the spacecraft. The timing
• 20:51
  Speaker 1: matters as much as the engine. And none of it
• 20:54
  Speaker 1: can be fixed once the vehicle leaves the pad. Everything
• 20:58
  Speaker 1: about getting to Jupiter comes back to this. Speed is
• 21:03
  Speaker 1: not free. Direction is not simple. and the math punishes
• 21:08
  Speaker 1: every mistake without warning. In 1925, a German engineer named
• 21:15
  Speaker 1: Walter Hohmann worked out the most fuel-efficient way to move
• 21:19
  Speaker 1: a spacecraft between two planetary orbits. The answer he arrived
• 21:24
  Speaker 1: at has governed interplanetary mission design ever since. Hohmann wasn't
• 21:30
  Speaker 1: working with computers. He was working with mathematics, pencil, paper,
• 21:36
  Speaker 1: And what he discovered was elegant in the way that
• 21:39
  Speaker 1: only genuinely correct things are elegant. His insight was this.
• 21:45
  Speaker 1: The cheapest way to move from one circular orbit to
• 21:48
  Speaker 1: another is not to fight the geometry. It's to use
• 21:52
  Speaker 1: the geometry. You give the spacecraft one single push to
• 21:57
  Speaker 1: stretch its orbit outward into an ellipse. Let it coast
• 22:02
  Speaker 1: all the way to the far end of that ellipse.
• 22:04
  Speaker 1: where the target planet's orbit is, then give it one
• 22:08
  Speaker 1: final push to circularize again. Two burns. Everything in between
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  Speaker 1: is free. The spacecraft is simply falling through space along
• 22:20
  Speaker 1: a path that the laws of gravity already laid out.
• 22:25
  Speaker 1: It costs nothing beyond those two moments of thrust. Picture
• 22:29
  Speaker 1: Earth's orbit as a circle sitting close to the Sun.
• 22:34
  Speaker 1: Jupiter's orbit as a much larger circle sitting far out.
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  Speaker 1: The Hohmann transfer is an ellipse that just barely kisses
• 22:43
  Speaker 1: Earth's orbit on one side and just barely kisses Jupiter's
• 22:47
  Speaker 1: orbit on the other. The spacecraft starts at the kiss
• 22:51
  Speaker 1: point near Earth, fires its engine once to leave Earth's
• 22:56
  Speaker 1: orbit and begin the long arc outward, then coasts for
• 23:00
  Speaker 1: the entire crossing until it reaches the kiss point near Jupiter.
• 23:06
  Speaker 1: If it wants to stop there rather than fly on past,
• 23:10
  Speaker 1: it fires again to slow down and match Jupiter's orbit.
• 23:15
  Speaker 1: If it doesn't need to stop, it can skip that
• 23:18
  Speaker 1: second burn entirely. The whole thing is almost mathematical poetry.
• 23:23
  Speaker 1: It is the minimum possible energy expenditure to bridge two orbits.
• 23:28
  Speaker 1: Nothing cheaper exists. But cheap energy has a price, and
• 23:33
  Speaker 1: the price is time. A Hohmann transfer from Earth to
• 23:38
  Speaker 1: Jupiter takes approximately 2.73 years. Nearly three years of coasting
• 23:44
  Speaker 1: through the dark, with the engines off. Carried along by
• 23:49
  Speaker 1: nothing except the orbital arc, Hohmann calculated a century ago.
• 23:54
  Speaker 1: For comparison, the Moon is a three-day trip. Mars, on
• 23:59
  Speaker 1: a Hohmann transfer, takes roughly nine months. Jupiter is in
• 24:05
  Speaker 1: a different category entirely. You're not talking about a long flight.
• 24:10
  Speaker 1: You're talking about years. This is why the Hohmann transfer
• 24:14
  Speaker 1: sets a floor, not a ceiling. It's the slowest fuel-efficient option,
• 24:20
  Speaker 1: and it's also the minimum energy option. And those two
• 24:23
  Speaker 1: things are connected. You cannot have one without the other.
• 24:27
  Speaker 1: If you want to go faster, you have to burn
• 24:30
  Speaker 1: more fuel. You have to push the spacecraft onto a
• 24:34
  Speaker 1: more aggressive trajectory, a steeper ellipse, one that cuts across
• 24:40
  Speaker 1: to Jupiter's orbit faster, but costs significantly more propellant to achieve.
• 24:47
  Speaker 1: That trade-off is always sitting in the background of every
• 24:50
  Speaker 1: interplanetary mission. Speed and fuel are in constant negotiation. The
• 24:57
  Speaker 1: Hohmann Transfer is the point on that curve where fuel
• 25:00
  Speaker 1: consumption is lowest and travel time is longest. Now, actual
• 25:06
  Speaker 1: missions rarely follow a pure Hohmann Transfer. There are several
• 25:11
  Speaker 1: reasons for this. One is timing. A true Hohmann Transfer
• 25:16
  Speaker 1: requires the planets to be positioned in a very specific
• 25:19
  Speaker 1: relationship when you launch. so that Jupiter will be at
• 25:23
  Speaker 1: the far kiss point of your ellipse exactly when your
• 25:27
  Speaker 1: spacecraft arrives there. If the planetary geometry isn't favourable for
• 25:32
  Speaker 1: a pure Hohmann path, mission designers have to modify the trajectory.
• 25:38
  Speaker 1: That usually means accepting either higher fuel costs or a
• 25:42
  Speaker 1: longer journey. Sometimes both. Another reason missions deviate is gravity assists.
• 25:50
  Speaker 1: If a spacecraft can swing past Venus or loop back
• 25:54
  Speaker 1: past Earth before heading out to Jupiter, it can pick
• 25:58
  Speaker 1: up extra velocity from those planetary flybys without burning a
• 26:02
  Speaker 1: drop of additional fuel. The route becomes longer in distance,
• 26:08
  Speaker 1: sometimes dramatically longer. But the spacecraft arrives with more speed
• 26:13
  Speaker 1: than a direct path would have given it. It used
• 26:17
  Speaker 1: less propellant to get there. That seems like a contradiction
• 26:22
  Speaker 1: until you understand what's happening. The spacecraft is stealing orbital
• 26:28
  Speaker 1: energy from the planets it passes. That is a trick
• 26:33
  Speaker 1: the Hohmann transfer doesn't use at all. We'll get into
• 26:37
  Speaker 1: how that works in detail later. For now, the important
• 26:42
  Speaker 1: thing is that gravity assists are one of the main
• 26:45
  Speaker 1: reasons real mission trajectories look nothing like the clean ellipse
• 26:49
  Speaker 1: Hohmann drew. There's also the question of what the mission
• 26:54
  Speaker 1: needs to do when it arrives. A spacecraft that only
• 26:58
  Speaker 1: needs to fly past Jupiter can skip the second engine
• 27:02
  Speaker 1: burn entirely and keep all that fuel as velocity. That
• 27:07
  Speaker 1: makes a significant difference. The burn required to actually enter
• 27:12
  Speaker 1: orbit around Jupiter is enormous. This was because Jupiter's gravity
• 27:17
  Speaker 1: is enormous. Canceling out enough speed to get captured by
• 27:22
  Speaker 1: that gravity demands a long powerful engine firing at exactly
• 27:26
  Speaker 1: the right moment. A flyby probe carries none of that burden.
• 27:32
  Speaker 1: It just keeps going. So when people ask why some
• 27:35
  Speaker 1: spacecraft reach Jupiter faster than others, part of the answer
• 27:40
  Speaker 1: is almost always that the faster ones didn't stop. What
• 27:43
  Speaker 1: Hohmann's transfer gives you then is a baseline to measure
• 27:47
  Speaker 1: everything against. It is the reference point that mission designers
• 27:52
  Speaker 1: start from before they start making trade-offs. Any spacecraft using
• 27:58
  Speaker 1: conventional chemical propulsion on a direct path, aiming to arrive
• 28:04
  Speaker 1: at Jupiter with any kind of control over what happens
• 28:07
  Speaker 1: when it gets there, is working within the constraints Hohmann describes.
• 28:13
  Speaker 1: The physics haven't changed in a hundred years. The rockets
• 28:17
  Speaker 1: are more powerful. The computers are vastly more sophisticated. The
• 28:23
  Speaker 1: trajectory analysis is extraordinarily refined. But the underlying math is
• 28:30
  Speaker 1: the same math Hohmann worked out by hand in 1925.
• 28:36
  Speaker 1: Every mission you'll hear about in the sections ahead from
• 28:39
  Speaker 1: the first clumsy fly-bys to the most sophisticated orbiters, was
• 28:44
  Speaker 1: designed with Hohmann's curve somewhere in the background of the calculations.
• 28:50
  Speaker 1: Sometimes the mission followed it closely. Sometimes it departed from
• 28:55
  Speaker 1: it dramatically. But it was always the starting point. Always
• 29:00
  Speaker 1: the thing being improved upon or deviated from. Always the
• 29:05
  Speaker 1: floor of what was possible. The Hohmann transfer gives you
• 29:10
  Speaker 1: the floor. No spacecraft using conventional chemical propulsion and a
• 29:15
  Speaker 1: direct efficient route can reach Jupiter faster than about two
• 29:20
  Speaker 1: and a half years. Most take considerably longer. Pioneer 10
• 29:25
  Speaker 1: launched in March of 1972 and became the first spacecraft
• 29:30
  Speaker 1: ever to cross the asteroid belt, which at the time
• 29:34
  Speaker 1: was considered one of the most uncertain parts of the
• 29:37
  Speaker 1: entire mission. Nobody had sent anything through it before. Nobody
• 29:43
  Speaker 1: actually knew what was on the other side. The asteroid
• 29:47
  Speaker 1: belt had a reputation that, it turns out, was somewhat undeserved.
• 29:53
  Speaker 1: Popular imagination pictured a dense, churning field of tumbling rock,
• 29:58
  Speaker 1: The kind of thing you see in a movie where
• 30:01
  Speaker 1: a pilot has to dodge and weave just to survive.
• 30:05
  Speaker 1: Scientists were more measured than that, but even they weren't sure.
• 30:09
  Speaker 1: Some estimated the debris density might be high enough to
• 30:13
  Speaker 1: puncture a spacecraft moving at tens of thousands of miles
• 30:16
  Speaker 1: per hour. There was genuine uncertainty about whether Pioneer 10
• 30:21
  Speaker 1: would make it through intact, or whether it would be
• 30:25
  Speaker 1: shredded before it ever got close to Jupiter. it made
• 30:29
  Speaker 1: it through without a scratch. The asteroid belt, as Pioneer
• 30:34
  Speaker 1: 10 revealed, is mostly empty. The rocks are real, but
• 30:39
  Speaker 1: they're spread across a band of space so vast that
• 30:42
  Speaker 1: running into one by chance is almost vanishingly unlikely. This
• 30:47
  Speaker 1: was not a small discovery. It was the thing that
• 30:51
  Speaker 1: opened the outer solar system to exploration. Before Pioneer 10,
• 30:57
  Speaker 1: The belt was a psychological barrier as much as a
• 31:00
  Speaker 1: physical one. After Pioneer 10, it was just a region
• 31:05
  Speaker 1: you crossed. That single data point changed the calculus of
• 31:10
  Speaker 1: every outer solar system mission that came after it. Now,
• 31:15
  Speaker 1: about the timeline. Pioneer 10 launched in March of 1972.
• 31:20
  Speaker 1: It reached Jupiter in December of 1973. That's roughly 21
• 31:28
  Speaker 1: months from launch to Jupiter. Pioneer 11 followed in April
• 31:34
  Speaker 1: of 1973 and arrived at Jupiter in December of 1974,
• 31:40
  Speaker 1: again about 21 months. What's striking about those numbers is
• 31:46
  Speaker 1: that they don't fit neatly into the Hohmann transfer picture.
• 31:51
  Speaker 1: The minimum energy path takes closer to two and a
• 31:54
  Speaker 1: half years, Pioneer was faster than that. How? The spacecraft
• 32:01
  Speaker 1: were moving quickly. Pioneer 10 hit a peak speed of
• 32:05
  Speaker 1: around 82,000 miles per hour. That kind of speed costs fuel,
• 32:11
  Speaker 1: and it means the spacecraft arrived before Jupiter had fully
• 32:15
  Speaker 1: travelled to the intercept point that a slow minimum energy
• 32:19
  Speaker 1: trajectory would have used. You pay for the extra speed
• 32:23
  Speaker 1: with propellant, But you bank it as time. Were these
• 32:27
  Speaker 1: missions perfect? No. The instruments were simple by modern standards.
• 32:34
  Speaker 1: The cameras were primitive. The telemetry was slow. But what
• 32:39
  Speaker 1: Pioneer returned was extraordinary for its era. Jupiter was enormous
• 32:44
  Speaker 1: in ways the numbers hadn't prepared anyone for. The Great
• 32:49
  Speaker 1: Red Spot was a real persistent structure in the cloud bands.
• 32:54
  Speaker 1: The radiation environment around Jupiter was punishing, far more intense
• 32:59
  Speaker 1: than engineers had expected, and it nearly overwhelmed Pioneer 10's
• 33:04
  Speaker 1: instruments during closest approach. That was a warning nobody had
• 33:10
  Speaker 1: been prepared for. The radiation belts of Jupiter turned out
• 33:15
  Speaker 1: to be among the most hostile environments in the entire
• 33:19
  Speaker 1: solar system. and Pioneer got the first real measurement of
• 33:24
  Speaker 1: just how hostile they were. Pioneer 11 used what Pioneer
• 33:29
  Speaker 1: 10 had learned. Engineers adjusted its closest approach trajectory so
• 33:34
  Speaker 1: it wouldn't take a severe irradiation hit. Pioneer 11 also
• 33:39
  Speaker 1: flew by Jupiter on a different path, which gave it
• 33:43
  Speaker 1: a gravitational kick that sent it on a trajectory towards Saturn.
• 33:48
  Speaker 1: the first spacecraft ever aimed at that planet. Jupiter wasn't
• 33:53
  Speaker 1: the destination. Jupiter was the fuel station. And that's the
• 33:58
  Speaker 1: part worth sitting with for a moment. Both pioneers arrived
• 34:03
  Speaker 1: at Jupiter after 21 months, which sounds like a success
• 34:07
  Speaker 1: story for fast travel. But neither one slowed down. Neither
• 34:13
  Speaker 1: one attempted to enter orbit. They came screaming in at
• 34:17
  Speaker 1: tens of thousands of miles per hour, made their closest pass,
• 34:22
  Speaker 1: collected what data their instruments could grab in the hours
• 34:26
  Speaker 1: around approach, and then Jupiter's gravity bent their paths and
• 34:30
  Speaker 1: flung them outward. Pioneer 10 was eventually aimed at the
• 34:34
  Speaker 1: star Aldebaran. Pioneer 11 headed toward the constellation Aquila. Both
• 34:41
  Speaker 1: of them are still out there. We lost contact with
• 34:45
  Speaker 1: Pioneer 10 in 2003, somewhere around 80 astronomical units from
• 34:51
  Speaker 1: the Sun. Pioneer 11 went silent in 1995. They're drifting now,
• 34:57
  Speaker 1: dark and cold, carrying a gold plaque etched with a
• 35:01
  Speaker 1: drawing of a man and a woman and a diagram
• 35:04
  Speaker 1: of where Earth is in the galaxy, just in case
• 35:07
  Speaker 1: someone finds them. Here is what the Pioneer missions actually
• 35:12
  Speaker 1: proved when you strip it down. Getting to Jupiter in
• 35:16
  Speaker 1: under two years is possible with mid-1970s technology. Crossing the
• 35:22
  Speaker 1: asteroid belt is survivable. Jupiter's radiation environment is brutal and
• 35:28
  Speaker 1: will kill your electronics if you're not careful. And flying
• 35:32
  Speaker 1: past a planet while using its gravity to redirect your
• 35:36
  Speaker 1: trajectory is a workable elegant solution to the problem of
• 35:40
  Speaker 1: not having enough fuel to do what you want to do.
• 35:44
  Speaker 1: What Pioneer did not prove is that you can get
• 35:47
  Speaker 1: to Jupiter and stay there. The 21-month timeline is real,
• 35:52
  Speaker 1: but it comes with an asterisk the size of the
• 35:55
  Speaker 1: spacecraft itself. That clock was running for a flyby, not
• 36:00
  Speaker 1: an orbital insertion. Slowing down enough to be captured by
• 36:05
  Speaker 1: Jupiter's gravity requires burning a massive amount of fuel at
• 36:10
  Speaker 1: precisely the right moment. And the spacecraft that did it
• 36:14
  Speaker 1: later had to carry all that extra propellant, which made
• 36:18
  Speaker 1: them heavier, which changed the math entirely. Neither pioneer stopped
• 36:23
  Speaker 1: at Jupiter. They used it as a slingshot and kept going,
• 36:27
  Speaker 1: which is a distinction that matters enormously when you're trying
• 36:31
  Speaker 1: to understand what reaching Jupiter actually requires. Voyager 1 and
• 36:37
  Speaker 1: Voyager 2 launched in the summer and fall of 1977,
• 36:42
  Speaker 1: and both were aimed at Jupiter, not because Jupiter was
• 36:46
  Speaker 1: the destination, but because Jupiter was the door. To understand why,
• 36:52
  Speaker 1: you have to go back to something that was figured
• 36:54
  Speaker 1: out in the late 1960s by a graduate student named
• 36:58
  Speaker 1: Gary Flandro, working at NASA's Jet Propulsion Laboratory. Flandreau was
• 37:04
  Speaker 1: running calculations on planetary positions when he noticed something remarkable.
• 37:10
  Speaker 1: In the late 1970s, Jupiter, Saturn, Uranus and Neptune were
• 37:17
  Speaker 1: going to line up in a configuration that only happens
• 37:21
  Speaker 1: once every 175 years. A spacecraft launched at exactly the
• 37:27
  Speaker 1: right time could use each planet's gravity to slingshot to
• 37:31
  Speaker 1: the next one. collecting speed at every stop. The whole
• 37:36
  Speaker 1: outer solar system, reachable in a single mission. NASA called
• 37:41
  Speaker 1: it the Grand Tour, and the window for it would
• 37:44
  Speaker 1: close and not reopen until the year 2153. If they
• 37:50
  Speaker 1: didn't go then, nobody alive today would ever get another chance.
• 37:55
  Speaker 1: Two spacecraft were built. Voyager 2 launched first on August
• 38:00
  Speaker 1: 20th 1977, on a trajectory designed to take full advantage
• 38:06
  Speaker 1: of the alignment. Jupiter, then Saturn, then Uranus, then Neptune,
• 38:12
  Speaker 1: each planet handing the spacecraft off to the next. Voyager
• 38:17
  Speaker 1: 1 launched about two weeks later, on September 5th, and
• 38:22
  Speaker 1: here is where the mission gets interesting. Voyager 1 was
• 38:26
  Speaker 1: not aimed at the Grand Tour, Engineers deliberately put it
• 38:31
  Speaker 1: on a faster, more aggressive path to Jupiter and Saturn,
• 38:35
  Speaker 1: one that would get it to the planet sooner, but
• 38:38
  Speaker 1: bend it away from Uranus and Neptune entirely. The trade-off
• 38:43
  Speaker 1: was speed. Voyager 1 reached Jupiter in March of 1979,
• 38:50
  Speaker 1: roughly 18 months after launch. Voyager 2 arrived the following July,
• 38:56
  Speaker 1: about 23 months out. Same solar system, two different clocks,
• 39:02
  Speaker 1: because trajectory is everything. What they found at Jupiter shook
• 39:07
  Speaker 1: the people reading the data. Jupiter was not what anyone expected.
• 39:13
  Speaker 1: The Great Red Spot, which astronomers had been watching through
• 39:17
  Speaker 1: telescopes for over three centuries, turned out to be a
• 39:21
  Speaker 1: storm so vast and so violent that two Earths could
• 39:26
  Speaker 1: fit inside it. It had been spinning for longer than
• 39:30
  Speaker 1: recorded history. The cloud bands that look like decorative stripes
• 39:35
  Speaker 1: from Earth were actually hurricane-force jet streams running in opposite
• 39:40
  Speaker 1: directions at hundreds of miles per hour. The whole planet
• 39:46
  Speaker 1: was churning, layered, and alive in ways that no telescope
• 39:51
  Speaker 1: had ever made clear. Then, there were the moons. The
• 39:56
  Speaker 1: four large Galilean moons, Io, Europa, Ganymede, and Callisto, had
• 40:03
  Speaker 1: always been known as points of light. Up close, they
• 40:07
  Speaker 1: were worlds. Europa showed a surface cracked like a broken eggshell,
• 40:13
  Speaker 1: smooth and young, which told scientists the ice was being
• 40:17
  Speaker 1: resurfaced continuously from below. That was a clue that took
• 40:21
  Speaker 1: years to fully interpret, but the implication was hard to ignore.
• 40:27
  Speaker 1: Something liquid might be moving under that ice. Ganymede turned
• 40:32
  Speaker 1: out to be the largest moon in the entire solar system,
• 40:36
  Speaker 1: bigger than the planet Mercury. Callisto was ancient and cratered,
• 40:41
  Speaker 1: a record of four billion years of impacts sitting perfectly preserved.
• 40:47
  Speaker 1: And then there was Io. Io was expected to be
• 40:51
  Speaker 1: a battered, dead rock. What Voyager found instead became one
• 40:56
  Speaker 1: of the most dramatic moments in the history of planetary science.
• 41:01
  Speaker 1: A navigation engineer named Linda Morabito was examining an image
• 41:05
  Speaker 1: of Io when she noticed something on the edge of
• 41:08
  Speaker 1: the moon. a faint umbrella-shaped plume rising off the surface.
• 41:14
  Speaker 1: She almost dismissed it. She didn't. It was a volcanic eruption,
• 41:20
  Speaker 1: actively happening, captured mid-blast by a camera travelling at tens
• 41:24
  Speaker 1: of thousands of miles per hour. Io was the most
• 41:28
  Speaker 1: volcanically active body in the solar system. Nobody had predicted it.
• 41:34
  Speaker 1: The data said otherwise, and the data won. Voyager 1
• 41:38
  Speaker 1: used Jupiter's gravity to bend towards Saturn, arriving there in
• 41:43
  Speaker 1: November of 1980. During the Saturn flyby, engineers aimed Voyager
• 41:49
  Speaker 1: 1 at Titan, Saturn's large moon, which required a specific
• 41:54
  Speaker 1: approach geometry. That geometry kicked Voyager 1 out of the
• 41:59
  Speaker 1: plane of the solar system entirely, ending any possibility of
• 42:04
  Speaker 1: further planetary encounters. it didn't matter. The Saturn data alone
• 42:10
  Speaker 1: was worth the sacrifice. Voyager 2 continued on its grand
• 42:15
  Speaker 1: tour path, reaching Saturn in 1981, Uranus in 1986, and
• 42:22
  Speaker 1: Neptune in 1989. No spacecraft has visited Uranus or Neptune since.
• 42:31
  Speaker 1: What the Voyager missions demonstrated, beyond all the science, was
• 42:35
  Speaker 1: a lesson in how to use the solar system itself
• 42:39
  Speaker 1: as infrastructure. Every gravity assist is a transaction. The spacecraft
• 42:45
  Speaker 1: arrives with a certain speed relative to the planet, swings
• 42:49
  Speaker 1: through the gravitational field in precisely the right geometry, and
• 42:54
  Speaker 1: leaves with more speed than it came in with. The
• 42:57
  Speaker 1: planet loses a nearly immeasurable fraction of its own orbital momentum.
• 43:03
  Speaker 1: the spacecraft gains thousands of miles per hour for free.
• 43:08
  Speaker 1: Without Jupiter's assist, neither Voyager would have reached the outer
• 43:13
  Speaker 1: solar system on any practical timeline. With it, Voyager 2
• 43:18
  Speaker 1: crossed the entire outer solar system in about 12 years,
• 43:23
  Speaker 1: a journey that would have taken decades on a direct
• 43:26
  Speaker 1: path using the rockets available at the time. Both spacecraft
• 43:30
  Speaker 1: crossed the heliopause, The boundary where the Sun's influence gives
• 43:35
  Speaker 1: way to interstellar space. Voyager 1 in 2012 and Voyager
• 43:41
  Speaker 1: 2 in 2018. They are the only human-made objects that
• 43:46
  Speaker 1: have ever left the solar system. They carry golden records
• 43:50
  Speaker 1: with sounds and images from Earth, encoded for any hypothetical
• 43:55
  Speaker 1: reader who might find them in the distant future. Their
• 44:00
  Speaker 1: nuclear power sources are fading. Transmissions are growing weaker, but
• 44:05
  Speaker 1: the motion never stops. Both spacecraft are still moving today,
• 44:11
  Speaker 1: carrying the momentum Jupiter gave them in 1979, traveling farther
• 44:17
  Speaker 1: from the Sun than any object humanity has ever sent
• 44:21
  Speaker 1: into space. Galileo launched from the space shuttle Atlantis in
• 44:25
  Speaker 1: October of 1989, and didn't reach Jupiter until December of 1995.
• 44:33
  Speaker 1: And the reason for that six year journey is one
• 44:36
  Speaker 1: of the clearest illustrations of how orbital mechanics actually work
• 44:41
  Speaker 1: in practice. The Voyagers had the luxury of speed because
• 44:45
  Speaker 1: speed was the point. Their payloads were relatively light, their
• 44:49
  Speaker 1: trajectories were optimized for a planetary grand tour, and neither
• 44:53
  Speaker 1: one was asked to stop. Galileo was asked to stop.
• 44:58
  Speaker 1: It was the first spacecraft ever designed to enter orbit
• 45:01
  Speaker 1: around Jupiter, and that single requirement changed everything about how
• 45:06
  Speaker 1: the mission had to be built. Entering orbit means carrying
• 45:11
  Speaker 1: enough fuel to break. Breaking fuel is mass. Mass requires
• 45:16
  Speaker 1: a more powerful launch. And here is where the problem started.
• 45:22
  Speaker 1: The Space Shuttle, paired with the upper stage available in 1989,
• 45:27
  Speaker 1: simply could not throw Galileo directly to Jupiter. The numbers
• 45:33
  Speaker 1: didn't work. The spacecraft was too heavy, and the rocket
• 45:37
  Speaker 1: wasn't strong enough to give it the velocity it needed
• 45:40
  Speaker 1: for a direct path. So the mission designers did something
• 45:44
  Speaker 1: that sounds almost absurd the first time you hear it.
• 45:48
  Speaker 1: They sent Galileo the long way around. The route went
• 45:52
  Speaker 1: like this. First, a flyby of Venus. then a swing
• 45:57
  Speaker 1: back past Earth, then another swing past Earth again. Three
• 46:02
  Speaker 1: planetary flybys in the inner solar system, each one stealing
• 46:06
  Speaker 1: a small piece of that planet's orbital momentum and transferring
• 46:11
  Speaker 1: it to Galileo, building up speed the launch vehicle couldn't provide.
• 46:17
  Speaker 1: This technique is called a Venus-Earth-Earth Gravity Assist, and it
• 46:22
  Speaker 1: is exactly as complicated as it sounds. The spacecraft looped
• 46:27
  Speaker 1: through the inner solar system for years before it had
• 46:31
  Speaker 1: accumulated enough velocity to head outward. By the time Galileo
• 46:37
  Speaker 1: finally broke free and pointed itself at Jupiter, it had
• 46:41
  Speaker 1: covered roughly 2.4 billion miles. Jupiter, at its farthest point
• 46:48
  Speaker 1: from Earth, is about 600 million miles away. Galileo traveled
• 46:55
  Speaker 1: four times the maximum possible straightly a distance to reach
• 47:00
  Speaker 1: its destination think about that a road trip where the
• 47:05
  Speaker 1: only route available requires looping through three other states twice
• 47:09
  Speaker 1: before the highway opens the journey took six years and
• 47:13
  Speaker 1: two months and nobody considered this a failure it was
• 47:17
  Speaker 1: the only way to get there don't lose sight of
• 47:21
  Speaker 1: this detail during that six-year cruise Galileo wasn't idle. It
• 47:26
  Speaker 1: made scientific observations on every flyby. When it swept past
• 47:31
  Speaker 1: the asteroid Gaspra in 1991, it became the first spacecraft
• 47:36
  Speaker 1: to photograph an asteroid up close. When it passed asteroid
• 47:41
  Speaker 1: Ida in 1993, it discovered that Ida had its own
• 47:46
  Speaker 1: small moon, a tiny rocky companion nobody had known existed.
• 47:52
  Speaker 1: These were bonus discoveries captured during a journey that was, itself,
• 47:57
  Speaker 1: a detour. The science had already begun before Galileo ever
• 48:02
  Speaker 1: reached its destination. Then, in July of 1994, something extraordinary
• 48:09
  Speaker 1: happened while Galileo was still in transit. Comet Shoemaker-Levy 9
• 48:14
  Speaker 1: broke apart and its fragments slammed into Jupiter one after
• 48:18
  Speaker 1: another over six days. Every telescope on Earth watched the
• 48:23
  Speaker 1: impacts from the front. Galileo watched from behind. It was
• 48:29
  Speaker 1: the only instrument in the solar system positioned to see
• 48:32
  Speaker 1: the actual collision side directly. The data it captured was irreplaceable.
• 48:39
  Speaker 1: A spacecraft not yet at its destination, already witnessing something
• 48:45
  Speaker 1: no other machine in history could observe. When Galileo finally
• 48:50
  Speaker 1: arrived at Jupiter in December of 1995, it did not
• 48:55
  Speaker 1: arrive alone. Five months earlier, mission controllers had released an
• 49:01
  Speaker 1: atmospheric probe, a separate, hardened capsule on a collision course
• 49:06
  Speaker 1: with Jupiter's cloud tops. That probe hit the atmosphere at
• 49:10
  Speaker 1: about 106,000 miles per hour. The deceleration was brutal. In
• 49:17
  Speaker 1: the first two minutes, it shed 99%. of its velocity.
• 49:22
  Speaker 1: Heat shields absorbed the energy of entry. Temperatures reached 15,500
• 49:28
  Speaker 1: degrees Celsius, hotter than the surface of the sun. And
• 49:33
  Speaker 1: then the probe survived. A parachute deployed. Instruments came online.
• 49:40
  Speaker 1: For 58 minutes, it transmitted data from inside Jupiter's atmosphere.
• 49:46
  Speaker 1: Pressure readings, temperature measurements, wind speeds, chemical composition, before the
• 49:53
  Speaker 1: pressure and heat finally crushed it. 58 minutes. The probe
• 50:00
  Speaker 1: we sent to Jupiter's atmosphere lasted less than an hour,
• 50:05
  Speaker 1: and in that time, it fundamentally changed what we knew
• 50:08
  Speaker 1: about the planet. Wind speeds were far higher than models predicted.
• 50:14
  Speaker 1: The chemical composition was different from what solar system formation
• 50:18
  Speaker 1: theories expected. Helium was scarcer than anticipated. The data raised
• 50:25
  Speaker 1: as many questions as it answered, which is usually how
• 50:29
  Speaker 1: the best science works. Meanwhile, the main spacecraft entered orbit.
• 50:36
  Speaker 1: What followed was nearly eight years of continuous Jupiter science.
• 50:41
  Speaker 1: Galileo completed 35 orbits around the Jovian system, making close
• 50:46
  Speaker 1: passes at each of the four large moons. Io showed
• 50:51
  Speaker 1: active volcanoes more powerful than anything on Earth, mountains taller
• 50:56
  Speaker 1: than Everest, lava lakes, a surface being continuously remade. Europa
• 51:02
  Speaker 1: revealed a cracked, icy crust floating above what appeared to
• 51:06
  Speaker 1: be a liquid ocean. And that single finding redirected decades
• 51:11
  Speaker 1: of planetary science toward a question that is still unanswered.
• 51:16
  Speaker 1: Is there something alive in there? Ganymede turned out to
• 51:21
  Speaker 1: have its own magnetic field, the only moon in the
• 51:25
  Speaker 1: solar system known to generate one. Callisto's ancient cratered surface
• 51:30
  Speaker 1: looked frozen in time, undisturbed for billions of years. None
• 51:36
  Speaker 1: of this would have been possible with a flyby. A
• 51:39
  Speaker 1: flyby gives you hours at most. A brief, brilliant snapshot
• 51:45
  Speaker 1: as the spacecraft hurtles past and keeps going. Galileo had years.
• 51:52
  Speaker 1: It could watch Io's volcanoes change between passes. It could
• 51:57
  Speaker 1: refine its measurements of Europa's ocean with each successive orbit.
• 52:02
  Speaker 1: It could notice things that only reveal themselves over time.
• 52:07
  Speaker 1: The difference between Galileo and everything that came before it
• 52:11
  Speaker 1: was the difference between a photograph and a documentary. In 2003,
• 52:17
  Speaker 1: mission controllers deliberately crashed Galileo into Jupiter. Its power was fading,
• 52:24
  Speaker 1: its instruments aging, and there was concern that an uncontrolled
• 52:29
  Speaker 1: end might eventually contaminate Europa. The moon scientists most wanted
• 52:35
  Speaker 1: to protect for future investigation. The spacecraft that had taken
• 52:40
  Speaker 1: six years to arrive met its end in seconds. Galileo
• 52:44
  Speaker 1: spent nearly eight years studying Jupiter from orbit and returned
• 52:49
  Speaker 1: more data about the Jovian system than everything before it combined.
• 52:54
  Speaker 1: But it took six years just to get there, and
• 52:57
  Speaker 1: that trade-off was not optional. New Horizons launched on January
• 53:04
  Speaker 1: 19th 2006 and reached Jupiter in just over 13 months
• 53:09
  Speaker 1: a record for any spacecraft to make that journey and
• 53:13
  Speaker 1: the reason it could move that fast comes down to
• 53:17
  Speaker 1: one specific decision that shaped everything about the mission that
• 53:22
  Speaker 1: decision was simple New Horizons was never going to stop
• 53:27
  Speaker 1: Galileo took six years to reach Jupiter because it needed
• 53:31
  Speaker 1: to slow down enough to be captured into orbit. Fuel
• 53:34
  Speaker 1: for braking. Mass from fuel. More fuel to move that mass.
• 53:40
  Speaker 1: That loop compounds brutally every time you add weight. New
• 53:45
  Speaker 1: Horizons was freed from all of it. It had one job.
• 53:49
  Speaker 1: Get to Pluto before Pluto's atmosphere froze out. Pluto drifts
• 53:54
  Speaker 1: on a long, strange orbit that carries it far enough
• 53:57
  Speaker 1: from the sun that its thin nitrogen atmosphere collapses and
• 54:02
  Speaker 1: freezes against the surface for decades at a time. There
• 54:07
  Speaker 1: was a window. Miss the window and the scientific mission
• 54:11
  Speaker 1: you designed the spacecraft around becomes a very expensive photograph
• 54:16
  Speaker 1: of a frozen rock. Speed was not optional for New Horizons.
• 54:21
  Speaker 1: It was the entire point. So engineers built the spacecraft
• 54:26
  Speaker 1: around velocity in a way nobody had done before for
• 54:30
  Speaker 1: a mission like this. New Horizons weighed about 1,054 pounds
• 54:36
  Speaker 1: fully loaded, which is light for a deep space probe.
• 54:41
  Speaker 1: Its science instruments were carefully selected. Nothing extra. Nothing that
• 54:47
  Speaker 1: added mass without a clear return. The spacecraft was essentially
• 54:52
  Speaker 1: an arrow, stripped down, balanced for distance, pointed outward, And
• 54:58
  Speaker 1: to launch it, NASA used the Atlas 5551, one of
• 55:03
  Speaker 1: the most powerful configurations available at the time. When New
• 55:08
  Speaker 1: Horizons cleared Earth's gravitational pull, it was moving at roughly 36,400
• 55:15
  Speaker 1: miles per hour. No human-made object had ever left Earth
• 55:20
  Speaker 1: that fast. Here is something that demands your attention. That
• 55:25
  Speaker 1: speed alone 36,400 miles per hour would not have been
• 55:31
  Speaker 1: enough to reach Jupiter in 13 months. That's where Jupiter
• 55:36
  Speaker 1: comes in, not as a destination, as a tool. New
• 55:42
  Speaker 1: Horizons was aimed at Jupiter with a very specific geometry
• 55:47
  Speaker 1: designed to thread the spacecraft close enough to the planet
• 55:50
  Speaker 1: to steal velocity from it. Jupiter's gravity grabbed the spacecraft
• 55:56
  Speaker 1: pulled it through a slingshot arc and flung it outward
• 56:00
  Speaker 1: with significantly more speed than it arrived with. At closest
• 56:05
  Speaker 1: approach to Jupiter, New Horizons was moving at roughly 52,000
• 56:11
  Speaker 1: miles per hour. The Jupiter flyby had added around 9,000
• 56:16
  Speaker 1: miles per hour to its speed without burning a single
• 56:20
  Speaker 1: drop of fuel. That extra velocity would carry it across
• 56:25
  Speaker 1: the remaining distance to Pluto, another 3 billion miles, in
• 56:30
  Speaker 1: a time frame that actually made the mission viable. Jupiter
• 56:35
  Speaker 1: was not a waypoint, it was the engine. The flyby
• 56:39
  Speaker 1: itself lasted only a matter of hours at closest approach,
• 56:43
  Speaker 1: but the science team had planned it carefully. New Horizons
• 56:47
  Speaker 1: wasn't just passing through, it collected measurements of Jupiter's atmosphere
• 56:52
  Speaker 1: observed the Great Red Spot, studied the plasma environment around
• 56:57
  Speaker 1: the planet, and got its first close look at some
• 57:01
  Speaker 1: of the Galilean moons. It watched Io and caught volcanic
• 57:06
  Speaker 1: activity in progress. Even at the speed it was moving,
• 57:11
  Speaker 1: even with only hours in the neighborhood, the spacecraft returned
• 57:16
  Speaker 1: useful data. But that data was secondary. What mattered was
• 57:22
  Speaker 1: the trajectory, and the trajectory worked exactly as designed. The
• 57:27
  Speaker 1: difference between New Horizons and every other spacecraft that had
• 57:30
  Speaker 1: visited Jupiter comes down to that stopping question. Pioneer crossed
• 57:36
  Speaker 1: the asteroid belt and kept going. Voyager used Jupiter as
• 57:41
  Speaker 1: a gravity slingshot and kept going. New Horizons did the same.
• 57:47
  Speaker 1: None of them stopped. Galileo stopped. Juno stopped. And stopping
• 57:54
  Speaker 1: is where the years pile up. Because physics doesn't give
• 57:58
  Speaker 1: you that deceleration for free. You have to earn it
• 58:01
  Speaker 1: with fuel. And fuel means mass. And mass means either
• 58:06
  Speaker 1: a heavier spacecraft or a longer, more looping route to
• 58:10
  Speaker 1: build up enough speed through gravity assists to compensate. New
• 58:15
  Speaker 1: Horizons carried none of that weight. It arrived at Jupiter
• 58:19
  Speaker 1: lighter than most spacecraft in the outer solar system, moving
• 58:24
  Speaker 1: faster than any of them had moved at that point
• 58:26
  Speaker 1: in their journeys, and it blew through the Jovian system
• 58:31
  Speaker 1: like something that had somewhere more important to be. Which
• 58:35
  Speaker 1: it did. When mission controllers confirmed the Jupiter flyby had
• 58:40
  Speaker 1: gone as planned, the celebration was real, but quick. The
• 58:45
  Speaker 1: Pluto encounter was still eight years away, New Horizons had
• 58:50
  Speaker 1: covered 365 million miles in 13 months, which sounds extraordinary.
• 58:57
  Speaker 1: And it is, but it was also just the beginning
• 59:00
  Speaker 1: of its actual mission. Jupiter was a milestone, not a
• 59:04
  Speaker 1: finish line. The spacecraft that broke the record for reaching
• 59:09
  Speaker 1: Jupiter treated Jupiter as a pit stop, and that inversion
• 59:14
  Speaker 1: tells you almost everything you need to understand about what
• 59:17
  Speaker 1: speed costs and what it requires. What it requires is
• 59:22
  Speaker 1: commitment to not stopping, not slowing, not capturing into orbit,
• 59:28
  Speaker 1: not deploying a probe, Not circling for months while your
• 59:32
  Speaker 1: instruments gather data in detail. You pick up speed. You
• 59:37
  Speaker 1: use the gravity of the largest planet in the solar
• 59:40
  Speaker 1: system to go even faster. And you keep moving until
• 59:45
  Speaker 1: your actual destination comes into view years later. That's the bargain.
• 59:52
  Speaker 1: That's what 13 months to Jupiter actually looks like. Were
• 59:56
  Speaker 1: you watching and wondering whether new horizons could have stayed? Technically,
• 1:00:02
  Speaker 1: a spacecraft could be designed to move fast and still
• 1:00:05
  Speaker 1: slow down, but the fuel required to break from 52,000
• 1:00:10
  Speaker 1: miles per hour into Jovian orbit would have made the
• 1:00:14
  Speaker 1: spacecraft so heavy that it never could have reached that
• 1:00:17
  Speaker 1: speed in the first place. The record and the mission
• 1:00:22
  Speaker 1: are inseparable. You cannot have the speed without the commitment
• 1:00:27
  Speaker 1: to keep it. Thirteen months is the fastest any human-made
• 1:00:33
  Speaker 1: object has ever travelled from Earth to Jupiter, and the
• 1:00:37
  Speaker 1: condition attached to that record is the same condition that
• 1:00:41
  Speaker 1: makes it almost irrelevant for any mission that actually needs
• 1:00:45
  Speaker 1: to be there. New Horizons never stopped. The Gravity Assist
• 1:00:51
  Speaker 1: is the closest thing to a free lunch that orbital
• 1:00:54
  Speaker 1: mechanics allows, and understanding it changes how you think about
• 1:00:59
  Speaker 1: every number you'll ever hear about spacecraft travel times. Here
• 1:01:04
  Speaker 1: is what is actually happening. A spacecraft coasting through the
• 1:01:08
  Speaker 1: solar system carries a fixed amount of energy. If you
• 1:01:11
  Speaker 1: want it to go faster, you need to add energy somehow,
• 1:01:15
  Speaker 1: and rockets burn fuel to do that. But there is
• 1:01:18
  Speaker 1: another way. If you can get close enough to a
• 1:01:22
  Speaker 1: planet that is already moving through space at high speed,
• 1:01:26
  Speaker 1: The planet's gravity will grab you and pull you through
• 1:01:29
  Speaker 1: a curved arc. And if the geometry is right, you
• 1:01:34
  Speaker 1: come out the other side going faster than you went in.
• 1:01:38
  Speaker 1: The planet's momentum bleeds over into yours, not through any
• 1:01:42
  Speaker 1: physical contact, just gravity, acting on both objects, doing the math.
• 1:01:48
  Speaker 1: The planet barely notices. Jupiter, for example. has a mass
• 1:01:54
  Speaker 1: of roughly 318 Earths. A spacecraft weighing a few tons
• 1:01:59
  Speaker 1: is stealing a sliver of momentum from something so massive
• 1:02:03
  Speaker 1: the effect is unmeasurable. But to the spacecraft, that stolen
• 1:02:08
  Speaker 1: speed can mean thousands of miles per hour added without
• 1:02:13
  Speaker 1: burning a single gram of propellant. You entered the encounter
• 1:02:18
  Speaker 1: going one speed. You left going a different one. The
• 1:02:23
  Speaker 1: orbit of the planet is functionally unchanged. Yours is not.
• 1:02:29
  Speaker 1: The geometry is everything, and this is where most people's
• 1:02:34
  Speaker 1: intuition breaks down. You cannot just fly close to a
• 1:02:38
  Speaker 1: planet and expect to gain speed. The direction of approach
• 1:02:42
  Speaker 1: determines whether you accelerate or slow down. If you approach
• 1:02:47
  Speaker 1: a planet roughly from behind, Swinging in on the trailing
• 1:02:51
  Speaker 1: side in the direction of the planet's orbital travel around
• 1:02:55
  Speaker 1: the Sun, you gain speed. The planet's gravity acts like
• 1:03:01
  Speaker 1: a sling, pulling you forward through its arc and releasing
• 1:03:05
  Speaker 1: you at higher velocity. Come in from the wrong angle,
• 1:03:09
  Speaker 1: from ahead of the planet in its orbital path, and
• 1:03:13
  Speaker 1: the effect runs in reverse. You lose speed. The planet
• 1:03:18
  Speaker 1: bleeds off your momentum instead of lending you some. Getting
• 1:03:22
  Speaker 1: this right requires calculating not just where the planet is,
• 1:03:26
  Speaker 1: but where it is going, how fast it is travelling,
• 1:03:30
  Speaker 1: and exactly what angle puts your trajectory on the correct
• 1:03:33
  Speaker 1: side of it. Think of a ball thrown against the
• 1:03:37
  Speaker 1: side of a moving train. If you throw it toward
• 1:03:40
  Speaker 1: the side of the train that is coming at you,
• 1:03:43
  Speaker 1: the ball bounces back faster than you threw it. The
• 1:03:47
  Speaker 1: train's motion transfers into the ball. Throw it against the
• 1:03:52
  Speaker 1: side moving away and the opposite happens. The spacecraft is
• 1:03:57
  Speaker 1: the ball. The planet is the train. The trick is
• 1:04:02
  Speaker 1: choosing your angle. Nobody sat down and derived this from
• 1:04:06
  Speaker 1: pure theory and then built a mission around it. The
• 1:04:10
  Speaker 1: practical realisation came gradually. Early mission planners focused almost entirely
• 1:04:17
  Speaker 1: on direct trajectories, how much fuel to burn, what angle
• 1:04:21
  Speaker 1: to launch, how long to coast. But as orbital mechanics
• 1:04:26
  Speaker 1: computing improved in the 1960s, engineers started looking at planetary
• 1:04:31
  Speaker 1: encounters differently. Michael Minovich, a UCLA graduate student, worked through
• 1:04:38
  Speaker 1: the mathematics of gravity assists in the early 1960s, and
• 1:04:44
  Speaker 1: demonstrated that flybys weren't just hazards to avoid or brief
• 1:04:49
  Speaker 1: data collection opportunities. They were velocity sources. Gary Flandro, working
• 1:04:56
  Speaker 1: at JPL in 1965, took that further and identified the
• 1:05:01
  Speaker 1: planetary alignment in the late 1970s that would allow a
• 1:05:05
  Speaker 1: spacecraft to hop from Jupiter to Saturn to Uranus to
• 1:05:10
  Speaker 1: Neptune on a single continuous chain of gravity assists. That
• 1:05:15
  Speaker 1: insight became the Voyager missions. Once the concept was established,
• 1:05:21
  Speaker 1: mission designers started using it aggressively. The question became how
• 1:05:27
  Speaker 1: many flybys you could chain together, and what combination of
• 1:05:31
  Speaker 1: planets would give you the most useful velocity change for
• 1:05:35
  Speaker 1: the least detour time. The Galileo mission is the extreme case.
• 1:05:42
  Speaker 1: Galileo was the first spacecraft designed to orbit Jupiter, launched
• 1:05:46
  Speaker 1: in 1989. The problem was weight. The spacecraft was heavy,
• 1:05:53
  Speaker 1: carrying a full orbital science package and a descent probe
• 1:05:58
  Speaker 1: intended to dive into Jupiter's atmosphere. The rocket that launched it,
• 1:06:04
  Speaker 1: the space shuttle plus an upper stage, simply did not
• 1:06:08
  Speaker 1: have the energy to send something that massive on a
• 1:06:11
  Speaker 1: direct path to Jupiter. A direct trajectory was not available
• 1:06:17
  Speaker 1: with the hardware on hand. So mission planners designed something unusual.
• 1:06:23
  Speaker 1: Galileo flew to Venus first. That flyby added velocity. Then
• 1:06:29
  Speaker 1: it swung back to Earth for a second boost. Then
• 1:06:32
  Speaker 1: it swung out toward the asteroid belt, turned around, and
• 1:06:36
  Speaker 1: came back to Earth again for a third flyby. Two
• 1:06:40
  Speaker 1: Earth flybys, one Venus flyby, and each one added speed,
• 1:06:45
  Speaker 1: bending Galileo's orbit outward toward Jupiter a little more each time.
• 1:06:51
  Speaker 1: The total path covered roughly 2.4 billion miles to reach
• 1:06:56
  Speaker 1: a planet that is, at closest approach, about 365 million
• 1:07:00
  Speaker 1: miles from Earth. The spacecraft looped through the inner solar
• 1:07:06
  Speaker 1: system twice before it had enough energy to make the
• 1:07:11
  Speaker 1: outer solar system crossing. It took just over six years.
• 1:07:17
  Speaker 1: That is not a failure of mission design. That is
• 1:07:21
  Speaker 1: mission design working exactly as intended, solving an otherwise impossible
• 1:07:26
  Speaker 1: energy problem with what was actually available. The detours were
• 1:07:31
  Speaker 1: the mission. Without the gravity assists from Venus and Earth,
• 1:07:36
  Speaker 1: Galileo simply could not have reached Jupiter at all on
• 1:07:40
  Speaker 1: that hardware. The choice was not between a direct fast
• 1:07:44
  Speaker 1: trip and a slow looping one. The choice was between
• 1:07:48
  Speaker 1: the looping path and no mission. Why can't every mission
• 1:07:53
  Speaker 1: just do what Galileo did? Because the planets have to
• 1:07:56
  Speaker 1: be there. A gravity assist requires a planet to be
• 1:08:01
  Speaker 1: in the right position at the right time when the
• 1:08:04
  Speaker 1: spacecraft arrives. You cannot schedule a Venus flyby if Venus
• 1:08:09
  Speaker 1: is on the wrong side of the Sun during your
• 1:08:11
  Speaker 1: transit window. The geometry has to work. And that geometry
• 1:08:18
  Speaker 1: is determined by orbital periods that operate on timescales of years,
• 1:08:23
  Speaker 1: completely indifferent to launch schedules or budget approvals. The Grand
• 1:08:28
  Speaker 1: Tour alignment that made the Voyager missions possible, that rare
• 1:08:33
  Speaker 1: configuration of Jupiter, Saturn, Uranus and Neptune lined up for
• 1:08:38
  Speaker 1: sequential flybys, occurs roughly once every 175 years. Miss it
• 1:08:43
  Speaker 1: and you wait 175 years. The Galileo route worked in
• 1:08:44
  Speaker 1: 1989 because Venus and Earth were positioned usefully in those years.
• 1:08:58
  Speaker 1: run the same mission in a different decade and the
• 1:09:02
  Speaker 1: geometry might not cooperate as well. Every gravity assist sequence
• 1:09:07
  Speaker 1: is a negotiation with the solar system's calendar. There is
• 1:09:11
  Speaker 1: also a time cost. Each flyby adds distance to the route.
• 1:09:16
  Speaker 1: Each additional loop through the inner solar system adds months
• 1:09:20
  Speaker 1: or years to the journey. The velocity gain has to
• 1:09:24
  Speaker 1: be weighed against the time lost making the detour. For Galileo,
• 1:09:29
  Speaker 1: the math said the six years was acceptable. For a
• 1:09:32
  Speaker 1: mission that needed to arrive quickly, a long gravity assist
• 1:09:36
  Speaker 1: chain would be counterproductive. New Horizons used Jupiter for a
• 1:09:41
  Speaker 1: gravity assist on the way to Pluto. One flyby, one boost,
• 1:09:46
  Speaker 1: no long detours 13 months to Jupiter that was the
• 1:09:51
  Speaker 1: right trade for that mission Galileo's route was the right
• 1:09:56
  Speaker 1: trade for its mission every mission to Jupiter has used
• 1:09:59
  Speaker 1: some form of gravity assist and the debate between mission
• 1:10:03
  Speaker 1: designers is never whether to use them but how many
• 1:10:07
  Speaker 1: detours are worth taking before the time savings become time
• 1:10:11
  Speaker 1: losses Juno launched in August of 2011 reached Jupiter in
• 1:10:17
  Speaker 1: July of 2016 and when it arrived it was moving
• 1:10:22
  Speaker 1: so fast that entering orbit required one of the most
• 1:10:26
  Speaker 1: precisely timed engine burns in the history of spaceflight. Five
• 1:10:30
  Speaker 1: years of travel and the hard part hadn't even started yet.
• 1:10:36
  Speaker 1: The thing people miss about Juno is what the arrival
• 1:10:39
  Speaker 1: actually looked like. The spacecraft had been falling toward Jupiter
• 1:10:44
  Speaker 1: for months pulled steadily inward by the planet's gravity well.
• 1:10:50
  Speaker 1: By the time it reached closest approach, it was moving
• 1:10:54
  Speaker 1: at roughly 130,000 miles per hour relative to Earth. No
• 1:11:00
  Speaker 1: spacecraft had ever entered orbit around another planet at that
• 1:11:04
  Speaker 1: kind of speed. That record didn't belong to a spacecraft
• 1:11:09
  Speaker 1: designed for speed. It belonged to a spacecraft that had
• 1:11:14
  Speaker 1: simply been falling toward the most massive planet in the
• 1:11:17
  Speaker 1: solar system for five years and couldn't avoid going fast.
• 1:11:22
  Speaker 1: To enter orbit rather than shoot straight past Jupiter, Juno
• 1:11:26
  Speaker 1: had to fire its main engine for exactly 35 minutes.
• 1:11:31
  Speaker 1: Not 30, not 40. 35 minutes of continuous burn to
• 1:11:37
  Speaker 1: bleed off enough velocity to be captured by Jupiter's gravity.
• 1:11:42
  Speaker 1: If the engine cut out early, Juno would have sailed
• 1:11:45
  Speaker 1: past the planet and kept going into deep space, mission over.
• 1:11:51
  Speaker 1: If it burned too long, the spacecraft would have fallen
• 1:11:55
  Speaker 1: too deep into Jupiter's gravity, which brings its own set
• 1:11:59
  Speaker 1: of catastrophic problems. The margin between those two outcomes was
• 1:12:05
  Speaker 1: the width of a very precise calculation. made by engineers
• 1:12:10
  Speaker 1: sitting in Pasadena, California, 48 minutes of light speed away.
• 1:12:16
  Speaker 1: By the time the signal confirming the burn had started
• 1:12:20
  Speaker 1: arrived at mission control, the burn was already finished. Whatever
• 1:12:26
  Speaker 1: happened during those 35 minutes happened without any possibility of
• 1:12:31
  Speaker 1: human intervention. The spacecraft made it. But it was not
• 1:12:37
  Speaker 1: a situation that invited much relaxation. Now here's the part
• 1:12:42
  Speaker 1: worth holding in your mind. Jupiter's radiation environment is not
• 1:12:47
  Speaker 1: a minor hazard. It is one of the most intense
• 1:12:50
  Speaker 1: radiation fields anywhere in the solar system. Jupiter's magnetic field
• 1:12:56
  Speaker 1: is roughly 20,000 times stronger than Earth's, and it does
• 1:13:00
  Speaker 1: what strong magnetic fields do. It traps charged particles and
• 1:13:05
  Speaker 1: whips them up to extreme energies. The radiation belts around
• 1:13:10
  Speaker 1: Jupiter make Earth's Van Allen belts look gentle by comparison.
• 1:13:16
  Speaker 1: Close to the planet, radiation levels are enough to destroy
• 1:13:20
  Speaker 1: unshielded electronics within hours, not months, hours. Engineers designing Juno
• 1:13:27
  Speaker 1: knew this going in, and they built a solution that
• 1:13:30
  Speaker 1: weighs about 400 pounds. and is made of titanium. The
• 1:13:35
  Speaker 1: radiation vault, a box, essentially, housing the spacecraft's most critical electronics,
• 1:13:43
  Speaker 1: shielded against the worst of what Jupiter can throw. It works,
• 1:13:48
  Speaker 1: but it doesn't work forever. Jupiter's radiation has been slowly
• 1:13:53
  Speaker 1: degrading Juno since the moment it entered orbit. Every pass
• 1:13:58
  Speaker 1: through the inner radiation belts takes a small toll on
• 1:14:02
  Speaker 1: the hardware, The spacecraft was not designed to last indefinitely
• 1:14:07
  Speaker 1: in that environment. The question was always how long it
• 1:14:11
  Speaker 1: could hold together. What has Juno actually found? Quite a bit,
• 1:14:17
  Speaker 1: it turns out. Before Juno, nobody had imaged Jupiter's poles
• 1:14:22
  Speaker 1: in detail. The Voyager flybys and Galileo's orbital geometry both
• 1:14:27
  Speaker 1: kept those regions mostly out of view. Juno's polar orbit
• 1:14:32
  Speaker 1: was specifically chosen to change that. What the cameras captured
• 1:14:37
  Speaker 1: looked almost nothing like the banded, orderly Jupiter most people picture.
• 1:14:43
  Speaker 1: The poles are covered in enormous cyclones, densely packed, some
• 1:14:48
  Speaker 1: of them thousands of miles across, churning in patterns that
• 1:14:52
  Speaker 1: don't match anything in existing models. The south pole has
• 1:14:57
  Speaker 1: a central cyclone ringed by five more. The North Pole
• 1:15:02
  Speaker 1: has a central cyclone ringed by eight. Why those specific numbers?
• 1:15:08
  Speaker 1: Nobody has a clean answer yet. Beyond the poles, Juno
• 1:15:13
  Speaker 1: measured Jupiter's magnetic field with a precision that hadn't been
• 1:15:17
  Speaker 1: possible from a distance. The field turned out to be
• 1:15:21
  Speaker 1: stronger than expected and stranger in its distribution, lopsided, concentrated
• 1:15:27
  Speaker 1: in ways that suggest the planet's interior is more complicated
• 1:15:32
  Speaker 1: than the relatively simple layered models that had been standard.
• 1:15:37
  Speaker 1: Juno's gravity measurements have added to that picture, hinting at
• 1:15:42
  Speaker 1: a fuzzy, diffuse core rather than the compact rocky centre
• 1:15:47
  Speaker 1: many models assumed. Jupiter, it turns out, is not nearly
• 1:15:52
  Speaker 1: as well understood as its centuries of observation might suggest.
• 1:15:58
  Speaker 1: Getting a spacecraft into orbit around it was what it
• 1:16:01
  Speaker 1: took to find that out. Juno's original mission was supposed
• 1:16:05
  Speaker 1: to end in February of 2018. The radiation accumulation had
• 1:16:11
  Speaker 1: been expected to degrade the spacecraft to a point where
• 1:16:14
  Speaker 1: science return would drop below acceptable levels. That deadline came
• 1:16:20
  Speaker 1: and went, and Juno was still functioning. NASA extended the mission.
• 1:16:26
  Speaker 1: then extended it again. As of now, the spacecraft is
• 1:16:30
  Speaker 1: still in operation. Its mission scope expanded to include close
• 1:16:35
  Speaker 1: flybys of several of Jupiter's moons, Ganymede, Europa, Io. Each
• 1:16:42
  Speaker 1: one is a target that future missions will study in
• 1:16:45
  Speaker 1: much more detail. Juno is, in some ways, doing advance
• 1:16:50
  Speaker 1: reconnaissance for whatever comes next. The story of Juno is
• 1:16:55
  Speaker 1: really the story of what it costs to actually stop
• 1:16:58
  Speaker 1: at Jupiter. New Horizons got to Jupiter faster. Pioneer got
• 1:17:03
  Speaker 1: there first. Voyager found the most dramatic things. But Juno
• 1:17:08
  Speaker 1: is the one that stayed. And staying required a five
• 1:17:12
  Speaker 1: year journey, a 35 minute engine burn with no margin
• 1:17:16
  Speaker 1: for error, and a spacecraft armoured against one of the
• 1:17:20
  Speaker 1: most hostile environments any human-built object has ever entered. Juno
• 1:17:26
  Speaker 1: is still operational as of this writing, slowly being degraded
• 1:17:30
  Speaker 1: by radiation that is unlike anything spacecraft experience anywhere else
• 1:17:36
  Speaker 1: in the solar system, still returning data from a world
• 1:17:40
  Speaker 1: that keeps revealing things nobody predicted. The Parker Solar Probe
• 1:17:45
  Speaker 1: has reached speeds of 430,000 miles per hour relative to
• 1:17:48
  Speaker 1: the which makes it the fastest object humanity has ever built.
• 1:17:57
  Speaker 1: And if you could apply that speed to a journey
• 1:17:59
  Speaker 1: to Jupiter, the trip would take about 43 hours. That
• 1:18:05
  Speaker 1: number deserves a second to land. 43 hours. Not years.
• 1:18:12
  Speaker 1: Not months. Less than two days to cross hundreds of
• 1:18:17
  Speaker 1: millions of miles. So why aren't we doing that? Why
• 1:18:22
  Speaker 1: is every mission we've talked about measured in years when
• 1:18:25
  Speaker 1: the fastest thing we've ever built could theoretically make the
• 1:18:29
  Speaker 1: trip before the week is out? Here's the part that
• 1:18:33
  Speaker 1: most people miss. Parker's speed is not the kind of
• 1:18:36
  Speaker 1: speed you can aim at something. That 430,000 miles per
• 1:18:41
  Speaker 1: hour is orbital velocity. The speed the spacecraft reaches when
• 1:18:47
  Speaker 1: it falls toward the sun on an extremely elongated orbit,
• 1:18:52
  Speaker 1: swinging close enough that the Sun's gravity is pulling it
• 1:18:56
  Speaker 1: like a stone in a slingshot. At the bottom of
• 1:19:00
  Speaker 1: that swing, near perihelion, Parker is moving faster than anything
• 1:19:05
  Speaker 1: we've ever built. but that speed is pointed sideways, tangent
• 1:19:11
  Speaker 1: to the orbit, not outward toward Jupiter. It's the same
• 1:19:16
  Speaker 1: reason a racing car going around a banked curve isn't
• 1:19:19
  Speaker 1: travelling in the direction it needs to go next. Speed
• 1:19:23
  Speaker 1: and direction are not the same thing. The distinction between
• 1:19:27
  Speaker 1: orbital speed and transfer speed is one of those things
• 1:19:31
  Speaker 1: that sounds technical until you picture it clearly. Parker isn't
• 1:19:36
  Speaker 1: rocketing away from the Sun at 430,000 miles per hour.
• 1:19:42
  Speaker 1: It's orbiting the Sun at that speed, sweeping around it
• 1:19:46
  Speaker 1: in an arc. Every time it reaches perihelion, it's screaming
• 1:19:51
  Speaker 1: through the inner solar system in a curved path. To
• 1:19:55
  Speaker 1: actually redirect that speed outward, toward Jupiter, you'd have to
• 1:20:00
  Speaker 1: fight the orbital geometry entirely. The Sun's gravity is what
• 1:20:06
  Speaker 1: gave Parker that speed, and the sun's gravity is also
• 1:20:10
  Speaker 1: what makes it nearly impossible to use that speed to
• 1:20:14
  Speaker 1: escape into the outer solar system. You'd have to burn
• 1:20:18
  Speaker 1: enormous amounts of fuel just to change the direction of
• 1:20:22
  Speaker 1: the momentum, which would cost more energy than the speed
• 1:20:26
  Speaker 1: gain was worth. Run the thought experiment anyway, though, because
• 1:20:31
  Speaker 1: it's worth running. Jupiter's average distance from Earth is roughly
• 1:20:36
  Speaker 1: 444 million miles. If a spacecraft could maintain 430,000 miles
• 1:20:43
  Speaker 1: per hour in a straight line, not an orbit, just
• 1:20:47
  Speaker 1: a straight burn, it would cover that distance in just
• 1:20:51
  Speaker 1: over 43 hours. That's a Wednesday to a Friday. You launch,
• 1:20:58
  Speaker 1: you watch a couple of movies, you do some reading.
• 1:21:02
  Speaker 1: and then Jupiter is filling the window. The physics of
• 1:21:06
  Speaker 1: that trip aren't violated by any law of nature. Nothing
• 1:21:11
  Speaker 1: in the universe says you cannot move a spacecraft at
• 1:21:14
  Speaker 1: that speed through that distance. Light takes about 43 minutes
• 1:21:19
  Speaker 1: to reach Jupiter from Earth, and light is the fastest
• 1:21:23
  Speaker 1: thing permitted by physics. A spacecraft at Parker's peak speed
• 1:21:29
  Speaker 1: would be about 60 times slower than light. That is,
• 1:21:33
  Speaker 1: in cosmic terms, still staggeringly fast. What stops us is energy.
• 1:21:40
  Speaker 1: The amount of energy required to accelerate a meaningful payload
• 1:21:46
  Speaker 1: to 430,000 miles per hour and sustain it there is
• 1:21:50
  Speaker 1: not slightly beyond current technology. It is orders of magnitude
• 1:21:55
  Speaker 1: beyond it. To understand what that means in concrete terms,
• 1:22:00
  Speaker 1: think about what it costs to get something off the ground.
• 1:22:05
  Speaker 1: A heavy lift rocket, like the Falcon Heavy, burns through
• 1:22:09
  Speaker 1: roughly 500 tonnes of propellant to lift maybe 60 tonnes
• 1:22:13
  Speaker 1: of spacecraft into low orbit. And that's just getting to orbit,
• 1:22:19
  Speaker 1: moving at about 17,500 miles per hour. To get to 430,000
• 1:22:27
  Speaker 1: miles per hour, you'd need to accelerate the spacecraft to
• 1:22:31
  Speaker 1: roughly 25 times that velocity. The fuel required using conventional
• 1:22:37
  Speaker 1: chemical propulsion would be so massive that no rocket we've
• 1:22:41
  Speaker 1: ever built, or are planning to build, comes anywhere close
• 1:22:45
  Speaker 1: to carrying it. The rocket equation turns against you fast.
• 1:22:50
  Speaker 1: Every pound of fuel you add to go faster requires
• 1:22:53
  Speaker 1: more fuel to accelerate that fuel, which requires more fuel
• 1:22:58
  Speaker 1: on top of that, in a compounding spiral that collapses
• 1:23:02
  Speaker 1: under its own weight before you get anywhere near Parker's
• 1:23:06
  Speaker 1: speed with a useful payload. New Horizons, the fastest spacecraft
• 1:23:13
  Speaker 1: we ever launched away from Earth, left at about 36,400
• 1:23:16
  Speaker 1: miles per hour. That's fast. But 430,000 miles per hour
• 1:23:25
  Speaker 1: is almost 12 times faster. The energy difference between those
• 1:23:30
  Speaker 1: two speeds isn't 12 times. Kinetic energy scales with the
• 1:23:35
  Speaker 1: square of velocity, which means the energy required grows much
• 1:23:39
  Speaker 1: faster than the speed itself. The gap is not a
• 1:23:43
  Speaker 1: linear climb. It's a wall. None of this means the
• 1:23:46
  Speaker 1: idea is dead. It means we haven't built the engine
• 1:23:50
  Speaker 1: that can get us there yet. Parker Solar Probe didn't
• 1:23:54
  Speaker 1: reach those speeds with chemical propulsion. It fell. The question
• 1:24:00
  Speaker 1: is whether we'll eventually develop propulsion that can generate that
• 1:24:05
  Speaker 1: kind of velocity without needing the Sun's gravity to do
• 1:24:09
  Speaker 1: the work for us. The speed is physically possible. The
• 1:24:14
  Speaker 1: problem is energy. And the gap between what current propulsion
• 1:24:18
  Speaker 1: can deliver and what that calculation requires is not a
• 1:24:23
  Speaker 1: small gap. Jupiter's position relative to Earth changes constantly and
• 1:24:29
  Speaker 1: every 13 months or so the geometry lines up in
• 1:24:32
  Speaker 1: a way that makes the journey reasonably efficient. Miss that
• 1:24:37
  Speaker 1: window and the options for getting to Jupiter without a
• 1:24:40
  Speaker 1: catastrophic fuel penalty become considerably worse. This is what engineers
• 1:24:47
  Speaker 1: call the synodic period. It's the time it takes for
• 1:24:52
  Speaker 1: Earth and Jupiter to return to roughly the same relative
• 1:24:55
  Speaker 1: positions after one cycle. Earth laps Jupiter about once every
• 1:25:01
  Speaker 1: 398 days. That's your window. Not every 365 days. Not
• 1:25:04
  Speaker 1: every year on the calendar. Every 398. And the window
• 1:25:07
  Speaker 1: itself isn't a wide open door. It's narrow. a few
• 1:25:20
  Speaker 1: weeks on either side of the optimal date, and the
• 1:25:23
  Speaker 1: geometry starts sliding away from you fast. Here's what that
• 1:25:27
  Speaker 1: actually means. When Earth and Jupiter are positioned just right,
• 1:25:32
  Speaker 1: a spacecraft can leave Earth on an efficient trajectory and
• 1:25:36
  Speaker 1: arrive at Jupiter in a reasonable amount of time without
• 1:25:40
  Speaker 1: burning through catastrophic quantities of fuel. The math lines up.
• 1:25:46
  Speaker 1: The orbit works. Slide that launch date by a month
• 1:25:50
  Speaker 1: in either direction, and the same trajectory now requires noticeably
• 1:25:55
  Speaker 1: more fuel to compensate, or you accept a longer coast
• 1:25:59
  Speaker 1: through the void, or both. Slide it by two months,
• 1:26:03
  Speaker 1: and the mission either becomes more expensive or slower in
• 1:26:08
  Speaker 1: ways that cascade through the entire mission design. The solar
• 1:26:13
  Speaker 1: system is not generous with these windows. Mission planners know
• 1:26:17
  Speaker 1: this better than anyone. In the months before a launch
• 1:26:21
  Speaker 1: window opens, the trajectory teams are running thousands of calculations.
• 1:26:27
  Speaker 1: They're modeling every variation. What if the rocket is delayed
• 1:26:31
  Speaker 1: three days? What if it's delayed 10 days? What if
• 1:26:36
  Speaker 1: a component fails and they lose the primary window entirely?
• 1:26:41
  Speaker 1: For every scenario, There's a backup, and the backup is
• 1:26:45
  Speaker 1: almost always worse. It's slower or more expensive, or it
• 1:26:50
  Speaker 1: requires a different gravity assist sequence that adds months to
• 1:26:54
  Speaker 1: the journey. The primary window is primary for a reason.
• 1:26:59
  Speaker 1: Everything downstream from the launch date is shaped by it.
• 1:27:03
  Speaker 1: Galileo is the clearest example of this. The spacecraft was
• 1:27:08
  Speaker 1: delayed multiple times before launch. and each delay forced engineers
• 1:27:13
  Speaker 1: to rethink the trajectory. Eventually, the mission ended up on
• 1:27:18
  Speaker 1: a path that used Venus, then Earth, then Earth again
• 1:27:23
  Speaker 1: as gravity-assist waypoints just to accumulate enough speed to reach Jupiter.
• 1:27:29
  Speaker 1: Six years. That wasn't the original plan. That was the
• 1:27:34
  Speaker 1: consequence of working around constraints that kept shifting the geometry.
• 1:27:39
  Speaker 1: The solar system doesn't hold the window open while the
• 1:27:42
  Speaker 1: paperwork clears. Now put a human crew on board and
• 1:27:47
  Speaker 1: the problem multiplies. A robotic spacecraft sitting on the pad
• 1:27:52
  Speaker 1: waiting out a delay is inconvenient. A crewed spacecraft sitting
• 1:27:58
  Speaker 1: in low earth orbit waiting for the window to come
• 1:28:01
  Speaker 1: back around is a different category of problem. Every extra
• 1:28:05
  Speaker 1: week in orbit before departure is a week of food consumed,
• 1:28:10
  Speaker 1: oxygen used, water recycled through systems that wear out. It's
• 1:28:16
  Speaker 1: a week of radiation exposure outside Earth's protective magnetic field.
• 1:28:22
  Speaker 1: The crew hasn't gone anywhere yet, and the mission is
• 1:28:26
  Speaker 1: already accumulating cost in the most direct biological sense. There's
• 1:28:31
  Speaker 1: no pause button. You can't freeze the consumables, and you
• 1:28:36
  Speaker 1: can't freeze the crew. The clock runs. whether you're moving
• 1:28:41
  Speaker 1: toward Jupiter or waiting for the chance to leave. This
• 1:28:45
  Speaker 1: is one reason why human Jupiter missions scare mission architects
• 1:28:51
  Speaker 1: in ways that human Mars missions don't, at least not
• 1:28:55
  Speaker 1: to the same degree. Mars windows are also constrained. They
• 1:29:01
  Speaker 1: open roughly every 26 months, but the journey is shorter.
• 1:29:06
  Speaker 1: Miss a Mars window and the extra weight hurts. Miss
• 1:29:11
  Speaker 1: a Jupiter window and you're looking at another 13 months
• 1:29:15
  Speaker 1: before a comparable opportunity returns, and you've spent those 13
• 1:29:20
  Speaker 1: months burning through resources without moving an inch toward the destination.
• 1:29:26
  Speaker 1: The return window compounds everything. Once a spacecraft reaches Jupiter,
• 1:29:32
  Speaker 1: getting home isn't as simple as pointing back at Earth
• 1:29:35
  Speaker 1: and firing the engines. Earth has moved. The favorable alignment
• 1:29:41
  Speaker 1: for a return trajectory is its own separate calculation, and
• 1:29:46
  Speaker 1: it doesn't necessarily fall whenever the mission team would prefer
• 1:29:50
  Speaker 1: it to. A crewed mission that arrives at Jupiter might
• 1:29:55
  Speaker 1: face a wait of several months before the return window
• 1:29:58
  Speaker 1: opens into something efficient. That's months near Jupiter, inside its
• 1:30:05
  Speaker 1: radiation environment, before the journey home even starts. The total
• 1:30:11
  Speaker 1: mission duration isn't just the travel time out and back,
• 1:30:16
  Speaker 1: it's travel time plus the residency period forced on you
• 1:30:20
  Speaker 1: by the geometry. This is the piece that most explanations
• 1:30:24
  Speaker 1: of Jupiter travel time leave out. The journey doesn't end
• 1:30:29
  Speaker 1: when you arrive. It restarts when the planets allow it.
• 1:30:34
  Speaker 1: And there's no negotiating with orbital mechanics. Engineers can optimize trajectories,
• 1:30:40
  Speaker 1: select the best launch dates, build in contingencies, and run
• 1:30:45
  Speaker 1: every simulation available. What they cannot do is move Jupiter.
• 1:30:51
  Speaker 1: What they cannot do is accelerate Earth around its orbit
• 1:30:55
  Speaker 1: to create a more favorable angle. The window is where
• 1:30:59
  Speaker 1: it is because the planets are where they are, and
• 1:31:02
  Speaker 1: that reality sits upstream of every schedule, every budget approval,
• 1:31:08
  Speaker 1: every technical delay, every mission review that has ever been
• 1:31:12
  Speaker 1: held about sending anything to Jupiter. The solar system runs
• 1:31:17
  Speaker 1: on its own schedule. and the most carefully planned mission
• 1:31:21
  Speaker 1: in history cannot open a favorable launch window a single
• 1:31:26
  Speaker 1: day before the orbital geometry allows it. When Juno's main
• 1:31:32
  Speaker 1: engine fired for the 35-minute burn that put it into
• 1:31:36
  Speaker 1: orbit around Jupiter, the signal confirming that the burn had
• 1:31:40
  Speaker 1: started arrived at Mission Control in California 48 minutes after
• 1:31:46
  Speaker 1: the engine lit by which point the burn was already finished.
• 1:31:52
  Speaker 1: The team in Pasadena could only wait. They had loaded
• 1:31:56
  Speaker 1: the commands, run the simulations, check the software and then
• 1:32:01
  Speaker 1: let go. What happened at Jupiter stayed at Jupiter for
• 1:32:06
  Speaker 1: nearly an hour before Earth found out. This is the
• 1:32:11
  Speaker 1: 45 minute problem. Radio signals travel at the speed of
• 1:32:15
  Speaker 1: light and nothing in the known universe moves faster. At
• 1:32:19
  Speaker 1: Jupiter's closest approach to Earth, a signal takes about 33
• 1:32:24
  Speaker 1: minutes one way. At the farthest point, 53 minutes. The
• 1:32:30
  Speaker 1: average works out to roughly 43 minutes. So a round
• 1:32:34
  Speaker 1: trip conversation, you send a message, you wait for a reply,
• 1:32:40
  Speaker 1: takes somewhere around 86 minutes under typical conditions. an hour
• 1:32:45
  Speaker 1: and a half. Not because of equipment limits or antenna strength.
• 1:32:51
  Speaker 1: Because of distance and because light is the speed limit.
• 1:32:56
  Speaker 1: Think about what that means for a spacecraft executing a
• 1:32:59
  Speaker 1: critical burn. Juno's orbital insertion was the single most dangerous
• 1:33:05
  Speaker 1: moment of a five-year mission. Fire too little and Juno
• 1:33:11
  Speaker 1: shoots past Jupiter and disappears into the outer solar system.
• 1:33:16
  Speaker 1: Fire too much, and the spacecraft plunges too deep. The
• 1:33:21
  Speaker 1: margin was narrow, and the people who built it, who
• 1:33:25
  Speaker 1: designed every circuit and wrote every line of code, were
• 1:33:29
  Speaker 1: sitting in a room on Earth watching a screen, completely
• 1:33:34
  Speaker 1: unable to help. By the time any signal telling them
• 1:33:38
  Speaker 1: something had gone wrong could have reached them, the outcome
• 1:33:41
  Speaker 1: would already be decided. That changes everything about how you
• 1:33:45
  Speaker 1: build a spacecraft. The computers aboard Juno had to be
• 1:33:49
  Speaker 1: capable of making decisions without anyone's permission. If a sensor
• 1:33:54
  Speaker 1: reads an anomaly mid-burn, the spacecraft handles it. It has to.
• 1:34:00
  Speaker 1: There is no other option. Engineers spend years writing fault
• 1:34:04
  Speaker 1: protection software, branching logic that anticipates failures and tells the
• 1:34:10
  Speaker 1: spacecraft what to do when things go sideways and Earth
• 1:34:15
  Speaker 1: is 43 minutes away and silent. You are not flying
• 1:34:20
  Speaker 1: the spacecraft from the ground. You are writing instructions for
• 1:34:24
  Speaker 1: a machine that will fly itself in a situation nobody
• 1:34:29
  Speaker 1: can fully predict around a planet that takes nearly an
• 1:34:33
  Speaker 1: hour to talk to. Here's a scenario worth sitting with.
• 1:34:37
  Speaker 1: Something goes wrong during a critical maneuver. Maybe a thruster misfires.
• 1:34:43
  Speaker 1: Maybe a sensor gives a bad reading. The spacecraft sends
• 1:34:47
  Speaker 1: an alert immediately. That signal leaves Jupiter at the speed
• 1:34:52
  Speaker 1: of light and travels for 43 minutes across the solar
• 1:34:55
  Speaker 1: system before it reaches Earth. Mission controllers read the alert.
• 1:35:01
  Speaker 1: They assess the situation. They write a response command and
• 1:35:06
  Speaker 1: send it back. that return signal takes another 43 minutes.
• 1:35:13
  Speaker 1: By the time any human instruction reaches the spacecraft, 86
• 1:35:18
  Speaker 1: minutes have passed. In those 86 minutes, the spacecraft has
• 1:35:23
  Speaker 1: been completely on its own, deciding what to do based
• 1:35:28
  Speaker 1: on whatever fault protection logic it was given before the
• 1:35:31
  Speaker 1: mission started. If the logic was good, the mission survives.
• 1:35:38
  Speaker 1: If it wasn't, there is nothing. Gee, anyone on Earth
• 1:35:42
  Speaker 1: can do about it. Galileo, Juno, New Horizons at closest approach.
• 1:35:48
  Speaker 1: Every critical event in the Jovian system has unfolded this way. Autonomously.
• 1:35:55
  Speaker 1: The spacecraft running through its instructions. The ground team watching
• 1:35:59
  Speaker 1: a signal delay that makes real intervention physically impossible. There's
• 1:36:05
  Speaker 1: something almost haunting about it. Hundreds of engineers who gave
• 1:36:10
  Speaker 1: years to building a machine. And when the most important
• 1:36:13
  Speaker 1: moment arrives, all they can do is wait and see
• 1:36:18
  Speaker 1: what the machine decided. Now put humans in that spacecraft.
• 1:36:23
  Speaker 1: The communication delay doesn't change. It's still 43 minutes each way.
• 1:36:29
  Speaker 1: Still 86 minutes round trip. An astronaut on a Jupiter
• 1:36:34
  Speaker 1: mission who runs into a medical emergency cannot call Earth
• 1:36:39
  Speaker 1: and get real-time guidance the way someone in low Earth
• 1:36:43
  Speaker 1: orbit can. Mission control cannot watch a problem develop and
• 1:36:49
  Speaker 1: talk the crew through a fix. By the time Earth
• 1:36:53
  Speaker 1: hears about an emergency, the crew has already been managing
• 1:36:57
  Speaker 1: it for the better part of an hour. Whatever training
• 1:37:01
  Speaker 1: they have, whatever equipment is aboard, whatever decisions need to
• 1:37:06
  Speaker 1: be made, Those are made by people who are genuinely,
• 1:37:10
  Speaker 1: completely alone. Not in the romantic sense. In the operational sense.
• 1:37:18
  Speaker 1: The communication structure that holds every human spaceflight together right now.
• 1:37:23
  Speaker 1: The constant contact with ground teams. The real-time troubleshooting. The
• 1:37:29
  Speaker 1: flight director's monito. Ring every system. None of that works
• 1:37:34
  Speaker 1: at Jupiter. The crew becomes its own mission control, its
• 1:37:39
  Speaker 1: own medical team, its own engineering support. Every spacecraft at
• 1:37:44
  Speaker 1: Jupiter operates alone, responding to a universe that is moving
• 1:37:49
  Speaker 1: faster than the speed of human conversation, and for a
• 1:37:53
  Speaker 1: human crew that gap between event and response would be
• 1:37:56
  Speaker 1: one of the most disorienting aspects of the entire journey.
• 1:38:00
  Speaker 1: Jupiter's magnetic field is roughly 20,000 times stronger than Earth's.
• 1:38:06
  Speaker 1: and that fact alone reshapes every calculation about what it
• 1:38:11
  Speaker 1: would actually take to operate there. Most people hear that
• 1:38:15
  Speaker 1: number and file it away as an interesting detail. It
• 1:38:20
  Speaker 1: is not a detail. It is the dominant physical reality
• 1:38:25
  Speaker 1: of the entire Jovian system, and it affects everything from
• 1:38:30
  Speaker 1: how a spacecraft is built to whether a human being
• 1:38:33
  Speaker 1: could survive anywhere near that planet. The field extends outward
• 1:38:38
  Speaker 1: from Jupiter for tens of millions of miles in every direction.
• 1:38:44
  Speaker 1: If you could see it with your eyes, it would
• 1:38:47
  Speaker 1: be the largest structure in the solar system, bigger than
• 1:38:51
  Speaker 1: the Sun itself. And inside that field, something dangerous is
• 1:38:57
  Speaker 1: always happening. Here is what a magnetic field does to
• 1:39:00
  Speaker 1: charged particles moving through space. It traps them. It bends
• 1:39:06
  Speaker 1: their paths. It forces them into tight spiraling loops. And
• 1:39:11
  Speaker 1: every time a particle spirals, it picks up energy. Electrons
• 1:39:16
  Speaker 1: and protons caught inside Jupiter's get accelerated to velocities that
• 1:39:22
  Speaker 1: would be considered extreme, even in a particle accelerator on Earth.
• 1:39:28
  Speaker 1: They do not just drift around passively. They move at
• 1:39:31
  Speaker 1: a significant fraction of the speed of light. And they
• 1:39:35
  Speaker 1: do not hit you like a wave. They hit you
• 1:39:38
  Speaker 1: like a continuous storm of invisible bullets, passing straight through metal,
• 1:39:44
  Speaker 1: straight through circuitry, straight through biological tissues. The radiation belts
• 1:39:51
  Speaker 1: around Earth, the Van Allen belts, are genuinely hazardous. Satellites
• 1:39:58
  Speaker 1: avoid them when possible. Astronauts on the International Space Station
• 1:40:03
  Speaker 1: stay below them. Jupiter's equivalent is roughly a thousand times
• 1:40:07
  Speaker 1: more intense at close range. A thousand times. What does
• 1:40:11
  Speaker 1: that actually mean for a spacecraft? Unshielded electronics near Jupiter
• 1:40:17
  Speaker 1: would not degrade slowly over months. They would start failing
• 1:40:22
  Speaker 1: within hours. The sensors, the computers, the memory systems, all
• 1:40:28
  Speaker 1: of it would accumulate damage faster than the hardware could compensate.
• 1:40:34
  Speaker 1: Early mission designers understood this. Every spacecraft sent to Jupiter
• 1:40:40
  Speaker 1: has had to reckon with it in some form. The
• 1:40:43
  Speaker 1: Pioneer probes were simple enough that radiation damage was manageable.
• 1:40:49
  Speaker 1: Voyager flew through the system quickly, minimizing exposure time. But Galileo,
• 1:40:55
  Speaker 1: which orbited Jupiter for nearly eight years, had no such luxury.
• 1:41:01
  Speaker 1: It was inside that radiation environment continuously, and the damage accumulated.
• 1:41:07
  Speaker 1: Instruments degraded. Tape recorders malfunctioned. by the time engineers deliberately
• 1:41:14
  Speaker 1: crashed Galileo into Jupiter's atmosphere in 2003, the spacecraft was
• 1:41:21
  Speaker 1: a shadow of what it had been when it arrived.
• 1:41:24
  Speaker 1: Eight years of Jupiter radiation did that. Juno took a
• 1:41:28
  Speaker 1: different approach. Its designers knew they could not stop radiation
• 1:41:33
  Speaker 1: from reaching the spacecraft entirely, so they built a vault,
• 1:41:38
  Speaker 1: an actual titanium box, roughly the size of a large
• 1:41:42
  Speaker 1: carry-on bag, housing the most sensitive electronics aboard. Titanium is dense.
• 1:41:49
  Speaker 1: Dense materials absorb radiation better than light ones. That vault
• 1:41:54
  Speaker 1: reduced the radiation dose to Juno's core computers by a
• 1:41:58
  Speaker 1: factor of roughly 800. That is the kind of engineering
• 1:42:03
  Speaker 1: that does not make headlines, but makes the entire mission possible.
• 1:42:08
  Speaker 1: and it still was not enough to protect Juno indefinitely.
• 1:42:12
  Speaker 1: The spacecraft was originally planned for a shorter mission. It
• 1:42:17
  Speaker 1: has been extended repeatedly because it keeps functioning, but Jupiter's
• 1:42:22
  Speaker 1: radiation is still slowly working through the shielding. Every orbit
• 1:42:28
  Speaker 1: takes a toll. Juno also uses a polar orbit specifically
• 1:42:33
  Speaker 1: designed to limit time in the worst radiation zones. Jupiter's
• 1:42:38
  Speaker 1: radiation belts are concentrated around the equatorial plane of the planet,
• 1:42:44
  Speaker 1: much like Earth's Van Allen belts, but vastly more intense.
• 1:42:49
  Speaker 1: By flying in long, looping orbits over the poles rather
• 1:42:52
  Speaker 1: than circling the equator, Juno spends most of its time
• 1:42:56
  Speaker 1: in regions where the radiation is less concentrated, dipping down
• 1:43:01
  Speaker 1: toward the planet only briefly during each close pass. The
• 1:43:06
  Speaker 1: orbit is not shaped by scientific preference, it is shaped
• 1:43:10
  Speaker 1: by survival. That is what radiation does to mission design
• 1:43:14
  Speaker 1: at Jupiter. It does not just influence the plan, it
• 1:43:19
  Speaker 1: dictates the geometry. Now think about what this means for
• 1:43:23
  Speaker 1: a human crew. The numbers stop being engineering problems and
• 1:43:28
  Speaker 1: start being medical ones. A dose of radiation is measured
• 1:43:33
  Speaker 1: in sieverts. A chest X-ray delivers roughly 0.1 millisieverts. An
• 1:43:40
  Speaker 1: astronaut on a six-month International Space Station mission receives around
• 1:43:45
  Speaker 1: 80 millisieverts from cosmic background radiation in low Earth orbit.
• 1:43:51
  Speaker 1: NASA's career limit for astronauts, the maximum total dose considered
• 1:43:56
  Speaker 1: acceptable over a lifetime, sits around 600 to 1,000 millisieverts,
• 1:44:03
  Speaker 1: depending on the individual. In close Jupiter orbit, unshielded, a
• 1:44:08
  Speaker 1: human being would receive a lethal dose in a matter
• 1:44:12
  Speaker 1: of hours. Even inside a heavily shielded spacecraft, estimates for
• 1:44:17
  Speaker 1: radiation exposure near Jupiter run into thousands of millisieverts per
• 1:44:23
  Speaker 1: day in the inner radiation belts. There is no shielding
• 1:44:27
  Speaker 1: solution that makes extended close operations survivable. not with any
• 1:44:33
  Speaker 1: material we currently build spacecraft from. This is why any
• 1:44:37
  Speaker 1: serious discussion of human missions to the Jovian system does
• 1:44:41
  Speaker 1: not involve humans orbiting Jupiter closely at all. The practical
• 1:44:47
  Speaker 1: scenarios place the crew much farther out. Callisto, the outermost
• 1:44:52
  Speaker 1: of the four large Galilean moons, sits beyond the worst
• 1:44:57
  Speaker 1: of Jupiter's radiation belts. Operations based from Callisto would receive
• 1:45:02
  Speaker 1: radiation doses that are dangerous, but far more manageable than
• 1:45:06
  Speaker 1: close Jovian orbit, somewhere in the range of what a
• 1:45:10
  Speaker 1: Mars mission would experience from deep space cosmic radiation during
• 1:45:15
  Speaker 1: the transit. Europa, which has the most compelling scientific case
• 1:45:20
  Speaker 1: for exploration, sits deep inside the radiation environment. A crewed
• 1:45:26
  Speaker 1: landing on Europa would be extraordinarily hazardous. The radiation dose
• 1:45:32
  Speaker 1: on Europa's surface is estimated at around 540 millisieverts per day.
• 1:45:38
  Speaker 1: A crew could not stay long. Were they to spend
• 1:45:43
  Speaker 1: even a week there, they would have absorbed a significant
• 1:45:47
  Speaker 1: fraction of a lifetime's acceptable dose in a single visit.
• 1:45:52
  Speaker 1: Something else worth holding in your mind. The journey to
• 1:45:57
  Speaker 1: Jupiter takes years. During those years, The crew is outside
• 1:46:01
  Speaker 1: Earth's protective magnetosphere, exposed to cosmic radiation streaming in from
• 1:46:07
  Speaker 1: every direction. That background dose accumulates the entire way out
• 1:46:13
  Speaker 1: and the entire way back. By the time a crew
• 1:46:17
  Speaker 1: arrived at Jupiter, they would have already spent years collecting
• 1:46:21
  Speaker 1: radiation before the Jovian environment added its own contribution on top.
• 1:46:28
  Speaker 1: The two problems do not exist in isolation. They stack.
• 1:46:33
  Speaker 1: A mission that begins with several years of deep space transit,
• 1:46:38
  Speaker 1: radiation ends with an arrival at one of the most
• 1:46:41
  Speaker 1: hostile radiation environments in the solar system. The exposure is
• 1:46:47
  Speaker 1: not sequential in the sense of being separate challenges with
• 1:46:51
  Speaker 1: a gap between them. It is continuous. from the moment
• 1:46:55
  Speaker 1: the spacecraft leaves Earth orbit to the moment it returns.
• 1:47:01
  Speaker 1: This is what makes Jupiter different from Mars in ways
• 1:47:04
  Speaker 1: that go beyond simple distance. Mars is deep space. Mars
• 1:47:09
  Speaker 1: is far. But Mars sits outside Earth's magnetosphere without adding
• 1:47:15
  Speaker 1: a planetary radiation belt of its own. Jupiter brings both
• 1:47:19
  Speaker 1: problems simultaneously. The multi-year journey gives the crew a radiation
• 1:47:25
  Speaker 1: burden before they even get there, and then the destination
• 1:47:29
  Speaker 1: itself demands that they never get too close to what
• 1:47:32
  Speaker 1: they came to study. Every instrument aboard has to be
• 1:47:37
  Speaker 1: rated for an environment that destroys unshielded hardware in hours.
• 1:47:43
  Speaker 1: Every orbit has to be designed around what the radiation
• 1:47:47
  Speaker 1: belts will allow, not just what the science team wants.
• 1:47:52
  Speaker 1: The radiation is not a detail in the margin of
• 1:47:55
  Speaker 1: a Jupiter mission. It is a central constraint that shapes
• 1:47:59
  Speaker 1: the spacecraft design, the orbital profile, and the question of
• 1:48:04
  Speaker 1: whether any human crew could ever safely approach the planet
• 1:48:08
  Speaker 1: at all. Every number about getting to Jupiter changes the
• 1:48:13
  Speaker 1: moment you put humans on the spacecraft, not by a
• 1:48:17
  Speaker 1: small amount. Everything covered so far the trajectories, the gravity assists,
• 1:48:23
  Speaker 1: the orbital insertion burns, the radiation volts, all of that
• 1:48:29
  Speaker 1: was built around machines, machines that don't need to eat,
• 1:48:33
  Speaker 1: machines that don't need air. Machines that can be powered
• 1:48:38
  Speaker 1: down to almost nothing for months at a stretch while
• 1:48:41
  Speaker 1: they coast through the dark between planets, waiting for a
• 1:48:45
  Speaker 1: rival day. A spacecraft's computer doesn't notice the emptiness. It
• 1:48:52
  Speaker 1: doesn't lose muscle mass. It doesn't develop blood clots or
• 1:48:57
  Speaker 1: depression or a craving for something other than recycled water.
• 1:49:02
  Speaker 1: The moment you put a human crew on that spacecraft,
• 1:49:05
  Speaker 1: Every assumption underneath every number changes simultaneously. The changes stack
• 1:49:12
  Speaker 1: on top of each other in ways that compound fast.
• 1:49:16
  Speaker 1: Start with the basics. A human crew needs roughly 1.8
• 1:49:20
  Speaker 1: kilograms of food per person per day. They need water.
• 1:49:25
  Speaker 1: Some can be recycled, but recycling systems are heavy and imperfect.
• 1:49:30
  Speaker 1: They need oxygen generation, carbon dioxide scrubbing, temperature control, pressure maintenance,
• 1:49:38
  Speaker 1: medical supplies for conditions you can't predict years in advance.
• 1:49:43
  Speaker 1: They need exercise equipment because microgravity begins stripping bone density
• 1:49:48
  Speaker 1: at roughly 1-2% per month. Without aggressive countermeasures, a crew
• 1:49:55
  Speaker 1: arriving at Jupiter after years in transit would be in
• 1:49:58
  Speaker 1: no condition to do useful work. They need lighting calibrated
• 1:50:04
  Speaker 1: to support circadian rhythms. This was because without proper light cycles,
• 1:50:10
  Speaker 1: sleep degrades and judgment degrades with it. They need psychological
• 1:50:15
  Speaker 1: support structures, real ones, not gestures toward the idea of them,
• 1:50:22
  Speaker 1: because six years in a confined space with the same
• 1:50:25
  Speaker 1: small group of people. With no possibility of emergency return,
• 1:50:31
  Speaker 1: and a 45-minute communication delay to Earth produces the kind
• 1:50:36
  Speaker 1: of stress that no standard astronaut selection process wall is
• 1:50:42
  Speaker 1: designed to evaluate. None of this is theoretical. We already
• 1:50:46
  Speaker 1: know what happens to human bodies on long missions. Astronauts
• 1:50:51
  Speaker 1: returning from six months on the International Space Station routinely
• 1:50:56
  Speaker 1: struggle to walk under their own weight. Their cardiovascular systems
• 1:51:01
  Speaker 1: have partly forgotten what gravity requires of them. Their eyes
• 1:51:06
  Speaker 1: have changed shape from fluid redistribution toward the head during
• 1:51:11
  Speaker 1: months of weightlessness. Their immune systems behave differently. Six months
• 1:51:18
  Speaker 1: produces effects serious enough that returning astronauts spend weeks in
• 1:51:23
  Speaker 1: rehabilitation before they're considered recovered. A Jupiter mission even under
• 1:51:29
  Speaker 1: the most optimistic trajectory assumptions, would last somewhere between 6
• 1:51:34
  Speaker 1: and 9 years round trip. That is not 6 months
• 1:51:38
  Speaker 1: times 12. The body doesn't scale that way. Nobody has
• 1:51:43
  Speaker 1: data on what 6 years of continuous microgravity does to
• 1:51:47
  Speaker 1: a human being. This was because nobody has ever done it.
• 1:51:52
  Speaker 1: The data we do have from shorter missions is not encouraging.
• 1:51:57
  Speaker 1: Then there is the radiation. This deserves to be said plainly.
• 1:52:02
  Speaker 1: Beyond Earth's magnetic field, space is not empty in the
• 1:52:07
  Speaker 1: benign sense the word implies. It is filled with high-energy particles,
• 1:52:13
  Speaker 1: galactic cosmic rays streaming in from outside the solar system.
• 1:52:19
  Speaker 1: Solar energetic particles that arrive without warning when the sun
• 1:52:23
  Speaker 1: has an active day. Earth's magnetosphere deflects most of this.
• 1:52:28
  Speaker 1: Once a spacecraft leaves that protection, the crew is exposed
• 1:52:32
  Speaker 1: to all of it, continuously, for the entire journey. A
• 1:52:37
  Speaker 1: multi-year trip to Jupiter and back would expose each crew
• 1:52:41
  Speaker 1: member to radiation doses that, by current estimates, significantly exceed
• 1:52:48
  Speaker 1: what NASA considers an acceptable career limit for astronauts. we
• 1:52:53
  Speaker 1: are not talking about a modest increase in risk we
• 1:52:57
  Speaker 1: are talking about doses that substantially elevate lifetime cancer probability
• 1:53:03
  Speaker 1: and may cause measurable cognitive degradation memory processing speed the
• 1:53:11
  Speaker 1: kinds of functions that a crew member would need to
• 1:53:14
  Speaker 1: perform complex tasks years into the mission there is no
• 1:53:19
  Speaker 1: complete engineering solution to this right now you can add
• 1:53:23
  Speaker 1: shielding But shielding is heavy. Heavy means more fuel. And
• 1:53:28
  Speaker 1: more fuel means more mass. And more mass means more
• 1:53:32
  Speaker 1: fuel still. At some point, the shielding itself becomes part
• 1:53:37
  Speaker 1: of the problem it was meant to solve. Which brings
• 1:53:40
  Speaker 1: us to the mass problem, because it sits underneath everything
• 1:53:44
  Speaker 1: else like a foundation. Every system you add to keep
• 1:53:49
  Speaker 1: the crew alive and functional adds kilograms. Food for six
• 1:53:53
  Speaker 1: people for six years Water recycling hardware robust enough to
• 1:53:59
  Speaker 1: last without replacement parts Medical equipment comprehensive enough to handle
• 1:54:05
  Speaker 1: a serious illness or injury with no hospital within 400
• 1:54:10
  Speaker 1: million miles Exercise machines that can sustain a workout load
• 1:54:15
  Speaker 1: intense enough to slow bone loss across years of use
• 1:54:20
  Speaker 1: Radiation shielding sufficient to reduce, not eliminate, reduce, the exposure
• 1:54:26
  Speaker 1: to something closer to acceptable levels. Communication equipment capable of
• 1:54:32
  Speaker 1: maintaining contact across the distances involved. Spare parts for all
• 1:54:38
  Speaker 1: of the above. This was because nothing in the history
• 1:54:42
  Speaker 1: of human SP, Ace Flight has ever operated for six
• 1:54:46
  Speaker 1: consecutive years without something breaking. Add all of that up,
• 1:54:51
  Speaker 1: and you have a spacecraft that is not comparable to
• 1:54:54
  Speaker 1: Juno or New Horizons or Galileo in any meaningful sense.
• 1:54:59
  Speaker 1: You have something that has to be built and launched
• 1:55:03
  Speaker 1: at a scale no rocket ever constructed has come close
• 1:55:07
  Speaker 1: to achieving. The Juno spacecraft weighed about 3,600 kilograms at launch,
• 1:55:13
  Speaker 1: most of which was fuel. A crewed Jupiter vehicle. carrying
• 1:55:18
  Speaker 1: everything that crew survival requires, would likely need to be
• 1:55:22
  Speaker 1: an order of magnitude heavier, and that estimate assumes recycling
• 1:55:27
  Speaker 1: systems that work at efficiencies we haven't demonstrated over multi-year durations.
• 1:55:33
  Speaker 1: Propulsion technology more capable than what currently exists. The Saturn V,
• 1:55:40
  Speaker 1: the most powerful rocket humanity, has ever successfully flown. could
• 1:55:45
  Speaker 1: lift about 130,000 kilograms to low Earth orbit. That sounds
• 1:55:51
  Speaker 1: like a lot. For a crewed Jupiter mission, it is
• 1:55:55
  Speaker 1: a starting point for a conversation about how many launches
• 1:55:59
  Speaker 1: it would take to assemble the actual vehicle in orbit
• 1:56:03
  Speaker 1: before the journey could begin. This is why no space
• 1:56:07
  Speaker 1: agency has a funded, active program for sending humans to Jupiter.
• 1:56:13
  Speaker 1: It is not a failure of imagination. The vision is there.
• 1:56:18
  Speaker 1: The physics is understood well enough to know what the
• 1:56:21
  Speaker 1: requirements are. The gap is between the requirements and what
• 1:56:26
  Speaker 1: any existing or near-term technology can meet. That gap is
• 1:56:31
  Speaker 1: not a narrow one you could close with a focused
• 1:56:34
  Speaker 1: decade of development. It is wide enough that serious mission
• 1:56:38
  Speaker 1: architects who study it professionally tend to frame a crude
• 1:56:42
  Speaker 1: Jupiter mission as a late 21st century possibility at the earliest,
• 1:56:47
  Speaker 1: contingent on propulsion advances, life support advances, radiation mitigation advances,
• 1:56:56
  Speaker 1: a level of sustained political and financial commitment that no
• 1:57:00
  Speaker 1: space program anywhere has maintained for that length of time.
• 1:57:05
  Speaker 1: No space agency currently has an active, funded program for
• 1:57:10
  Speaker 1: sending humans to Jupiter and the math of why that
• 1:57:14
  Speaker 1: is makes the gap between ambition and reality feel almost
• 1:57:18
  Speaker 1: geological in scale. The longest continuous space flight in history
• 1:57:24
  Speaker 1: was 437 days set by Russian cosmonaut Valery Polyakov aboard
• 1:57:31
  Speaker 1: the Mir space station in 1994 and 1995 and when
• 1:57:33
  Speaker 1: he landed He was carried off the spacecraft because his
• 1:57:41
  Speaker 1: legs couldn't support his weight. That is 437 days. One person.
• 1:57:49
  Speaker 1: One station orbiting just a few hundred miles above Earth.
• 1:57:53
  Speaker 1: Still inside the protective bubble of Earth's magnetic field. Still
• 1:57:58
  Speaker 1: close enough that a rescue mission was physically possible. Polyakov's
• 1:58:03
  Speaker 1: record is extraordinary. It is also, relative to a Jupiter mission,
• 1:58:09
  Speaker 1: a warm-up lap. A crew heading to Jupiter and back
• 1:58:13
  Speaker 1: under the best currently imaginable scenario would spend somewhere between
• 1:58:18
  Speaker 1: six and nine years in transit. Do the math on
• 1:58:22
  Speaker 1: what Polyakov's experience represents in that context. His 437 days
• 1:58:28
  Speaker 1: is less than a fifth of the low end of
• 1:58:31
  Speaker 1: that range, and he came home unable to walk. Here
• 1:58:36
  Speaker 1: is what happens to the human body in microgravity, and
• 1:58:40
  Speaker 1: it starts almost immediately. Bone density drops at roughly 1-2%
• 1:58:46
  Speaker 1: per month. That sounds modest until you realize that over
• 1:58:51
  Speaker 1: six years, the accumulated loss is staggering. the equivalent of
• 1:58:56
  Speaker 1: what someone might experience over multiple decades of normal aging
• 1:59:01
  Speaker 1: on Earth, compressed into a single mission. The skeleton is
• 1:59:05
  Speaker 1: a dynamic structure. It responds to load, take away gravity,
• 1:59:11
  Speaker 1: and the body reads that absence as a signal to
• 1:59:14
  Speaker 1: stop maintaining bone mass it no longer needs. The result
• 1:59:20
  Speaker 1: is something close to accelerated osteoporosis. and no current countermeasure
• 1:59:25
  Speaker 1: fully stops it. Muscle atrophy follows the same logic. Without
• 1:59:31
  Speaker 1: gravity to push against constantly, the muscles that hold the
• 1:59:35
  Speaker 1: body upright, move it through a room, keep it functional
• 1:59:39
  Speaker 1: under the weight of its own frame, those muscles shrink.
• 1:59:44
  Speaker 1: ISS astronauts exercise two hours a day specifically to slow
• 1:59:50
  Speaker 1: this process down. They return from six-month missions and still
• 1:59:55
  Speaker 1: struggle to stand. Their bodies have to relearn what gravity
• 2:00:00
  Speaker 1: feels like. Stretch that mission to nine years and you
• 2:00:04
  Speaker 1: are asking the body to maintain function in a regime
• 2:00:08
  Speaker 1: it was never designed for, for a duration that has
• 2:00:11
  Speaker 1: no precedent in the history of human spaceflight. Then there
• 2:00:16
  Speaker 1: is the fluid shift. In microgravity, bodily fluids redistribute upward
• 2:00:22
  Speaker 1: pulling toward the head. This creates pressure changes inside the
• 2:00:27
  Speaker 1: skull that affect the eyes. A significant fraction of long-duration
• 2:00:33
  Speaker 1: ISS astronauts have returned with measurable changes to the structure
• 2:00:38
  Speaker 1: of their optic nerves and the shape of their eyeballs.
• 2:00:43
  Speaker 1: Some experienced lasting vision problems. The condition has a name now.
• 2:00:50
  Speaker 1: spaceflight-associated neuro-ocular syndrome and researchers are still working out exactly
• 2:00:57
  Speaker 1: what causes it and how to prevent it. A crew
• 2:01:00
  Speaker 1: traveling to Jupiter for several years would be living inside
• 2:01:04
  Speaker 1: that problem for the entire journey. The cardiovascular system deconditions too.
• 2:01:11
  Speaker 1: The heart, like any muscle, adapts to the demands placed
• 2:01:15
  Speaker 1: on it. In microgravity, those demands change dramatically. The result
• 2:01:22
  Speaker 1: over time is a heart that is smaller, less efficient
• 2:01:26
  Speaker 1: under gravity and less capable of handling the sudden return
• 2:01:31
  Speaker 1: to a 1G environment. The immune system shifts in ways
• 2:01:36
  Speaker 1: that are not fully understood. Latent viruses that the body
• 2:01:40
  Speaker 1: normally suppresses can reactivate. The combination of radiation exposure, disrupted
• 2:01:47
  Speaker 1: sleep cycles, stress and altered immune function creates a health
• 2:01:52
  Speaker 1: environment that has no clean analog in any terrestrial setting
• 2:01:58
  Speaker 1: none of this even touches the psychological dimension yet six
• 2:02:02
  Speaker 1: years in a spacecraft the size of a large apartment
• 2:02:06
  Speaker 1: with the same small group of people no possibility of
• 2:02:09
  Speaker 1: leaving no possibility of emergency return once you're past a
• 2:02:14
  Speaker 1: certain point in the trajectory earth over the first few
• 2:02:19
  Speaker 1: months of the journey, shrinks from a visible disk to
• 2:02:23
  Speaker 1: a bright star to something indistinguishable from the background. Then
• 2:02:28
  Speaker 1: it disappears entirely into the glare. Communications have a 45-minute
• 2:02:34
  Speaker 1: one-way delay. If something goes wrong with the crew, with
• 2:02:40
  Speaker 1: a relationship, with someone's mental health, there is no therapist
• 2:02:45
  Speaker 1: to call. There is no home. there is a message
• 2:02:49
  Speaker 1: that takes 90 minutes round-trip to deliver a reply. What
• 2:02:54
  Speaker 1: behavioral research exists on long-duration isolation is not especially reassuring.
• 2:03:00
  Speaker 1: Antarctic winter over cruise, small teams isolated for months in
• 2:03:05
  Speaker 1: extreme conditions, show measurable cognitive changes, elevated tension, communication breakdowns,
• 2:03:14
  Speaker 1: and what researchers have called third-quarter phenomenon, a significant dip
• 2:03:20
  Speaker 1: in morale and function that occurs roughly three quarters of
• 2:03:24
  Speaker 1: the way through a long isolated deployment. These are people
• 2:03:29
  Speaker 1: who can see the sky. Submarine crews operate in confined
• 2:03:34
  Speaker 1: isolation for months at a time and their psychological management
• 2:03:38
  Speaker 1: protocols are extensive, carefully studied and still produce casualties. Those
• 2:03:46
  Speaker 1: missions are measured in months A Jupiter mission is measured
• 2:03:51
  Speaker 1: in years. The honest thing to say about all of
• 2:03:55
  Speaker 1: this is that some of these problems are engineering problems.
• 2:04:00
  Speaker 1: Better exercise equipment, smarter radiation shielding, improved nutrition. These are
• 2:04:06
  Speaker 1: things that can be built and refined. But some of
• 2:04:10
  Speaker 1: them are not engineering problems. Bone loss in microgravity at
• 2:04:15
  Speaker 1: its core Is biology responding to the absence of a
• 2:04:19
  Speaker 1: force that shaped the human body over millions of years
• 2:04:23
  Speaker 1: of evolution? The vision changes are structural. The psychological effects
• 2:04:30
  Speaker 1: of years of confinement with no exit option are not
• 2:04:34
  Speaker 1: a software problem waiting for a patch. They are what
• 2:04:38
  Speaker 1: happens to people in certain conditions, and the conditions of
• 2:04:42
  Speaker 1: a Jupiter mission are conditions no human has ever actually endured.
• 2:04:48
  Speaker 1: A Jupiter mission would ask a crew to endure something
• 2:04:51
  Speaker 1: that makes Polyakov's record look like a warm-up, in an
• 2:04:55
  Speaker 1: environment where the sun has shrunk to a very bright
• 2:04:58
  Speaker 1: star and Earth takes 45 minutes to answer your messages.
• 2:05:04
  Speaker 1: Every serious discussion about human missions to Jupiter eventually arrives
• 2:05:09
  Speaker 1: at the same problem. The journey is too long with
• 2:05:13
  Speaker 1: current propulsion technology, and changing that requires either accepting a
• 2:05:19
  Speaker 1: different kind of mission, or developing engines that do not
• 2:05:22
  Speaker 1: yet exist. So what does exist? What is actually being built, tested,
• 2:05:29
  Speaker 1: or seriously studied that could change the numbers? Because there
• 2:05:34
  Speaker 1: are answers, not science fiction answers, real ones. and they
• 2:05:39
  Speaker 1: range from technologies almost ready to fly to ideas that
• 2:05:43
  Speaker 1: are genuinely decades away from anything you could put on
• 2:05:47
  Speaker 1: a launch pad. Each one deserves an honest look, because
• 2:05:52
  Speaker 1: the difference between where these programs are today and where
• 2:05:56
  Speaker 1: they would need to be is not a small gap.
• 2:06:01
  Speaker 1: Start with nuclear thermal propulsion, because this is the most
• 2:06:05
  Speaker 1: mature option. and the most likely to actually fly within
• 2:06:09
  Speaker 1: most people's lifetimes. The basic idea is not complicated. Instead
• 2:06:15
  Speaker 1: of burning chemical fuel to generate hot exhaust and thrust,
• 2:06:19
  Speaker 1: you run propellant through a nuclear reactor. The reactor heats
• 2:06:24
  Speaker 1: the propellant to temperatures no chemical combustion can match, and
• 2:06:28
  Speaker 1: it exits the nozzle much faster. Faster exhaust means better efficiency.
• 2:06:35
  Speaker 1: The technical measure is specific impulse, which is roughly how
• 2:06:39
  Speaker 1: much thrust you get per unit of fuel. Chemical rockets
• 2:06:44
  Speaker 1: top out around 450 seconds of specific impulse. A nuclear
• 2:06:50
  Speaker 1: thermal engine could hit 900 seconds or better. That is
• 2:06:55
  Speaker 1: roughly double the efficiency. Double the efficiency means either you
• 2:07:00
  Speaker 1: need half the fuel for the same trip, or you
• 2:07:03
  Speaker 1: can go considerably faster on the same fuel load. For
• 2:07:07
  Speaker 1: a Jupiter mission, models suggest nuclear thermal propulsion could cut
• 2:07:11
  Speaker 1: transit time for an orbital mission down to somewhere between
• 2:07:15
  Speaker 1: two and three years. Still not fast. But compared to
• 2:07:20
  Speaker 1: Galileo's six years, it is a different conversation entirely. And
• 2:07:25
  Speaker 1: this is not theoretical. NASA and DARPA have a joint
• 2:07:30
  Speaker 1: program called Draco, demonstration rocket for agile cislunar operations, specifically
• 2:07:37
  Speaker 1: aimed at testing a nuclear thermal engine in space by
• 2:07:41
  Speaker 1: the late 2020s. That is a real program, with real funding,
• 2:07:47
  Speaker 1: and real contractors working on the reactor design right now.
• 2:07:52
  Speaker 1: Whether it stays on schedule is a different question, but
• 2:07:56
  Speaker 1: the direction of travel is clear. Nuclear thermal propulsion is
• 2:08:02
  Speaker 1: the most credible near-term path toward faster deep space missions,
• 2:08:07
  Speaker 1: and it has been on paper since the 1960s when
• 2:08:10
  Speaker 1: the original NERVA program ran successful ground tests. The technology works.
• 2:08:18
  Speaker 1: the question has always been political will and money, not physics.
• 2:08:23
  Speaker 1: Then there is nuclear pulse propulsion, which is the point
• 2:08:26
  Speaker 1: where this conversation gets genuinely strange. The idea here is
• 2:08:31
  Speaker 1: to detonate small nuclear bombs behind the spacecraft and ride
• 2:08:36
  Speaker 1: the shockwave. Sounds absurd, but the math, done seriously by
• 2:08:42
  Speaker 1: serious people in the 1950s and 60s, under a program
• 2:08:46
  Speaker 1: called Project Orion, is actually compelling. A spacecraft using pulse
• 2:08:52
  Speaker 1: propulsion could theoretically reach velocities that would put Jupiter within
• 2:08:58
  Speaker 1: reach in a matter of months, not years, months. The
• 2:09:03
  Speaker 1: specific impulse numbers are extraordinary, tens of thousands of seconds,
• 2:09:09
  Speaker 1: not hundreds. Freeman Dyson, One of the most respected physicists
• 2:09:14
  Speaker 1: of the 20th century worked on Orion and believed it
• 2:09:18
  Speaker 1: was the most practical path to rapid interplanetary travel. He
• 2:09:23
  Speaker 1: was not a crank. But Orion died for reasons that
• 2:09:28
  Speaker 1: had nothing to do with physics. The Partial Nuclear Test
• 2:09:33
  Speaker 1: Ban Treaty of 1963 prohibited nuclear detonations in space, which
• 2:09:39
  Speaker 1: is a reasonable policy concern. and also a complete showstopper
• 2:09:43
  Speaker 1: for a spacecraft that works by detonating nuclear bombs every
• 2:09:48
  Speaker 1: few seconds. No serious development program for pulse propulsion exists today.
• 2:09:55
  Speaker 1: It lives in the category of ideas that the physics permits,
• 2:09:59
  Speaker 1: but everything else currently prevents. Ion propulsion is the opposite
• 2:10:05
  Speaker 1: end of the spectrum, not extreme, but proven. An ion
• 2:10:10
  Speaker 1: thruster works by accelerating charged particles electrically and ejecting them
• 2:10:15
  Speaker 1: at very high exhaust velocities. The efficiency is remarkable. The
• 2:10:21
  Speaker 1: thrust is not. Ion engines produce roughly the force of
• 2:10:26
  Speaker 1: a piece of paper resting on your hand. Over weeks
• 2:10:30
  Speaker 1: and months, that whisper of thrust adds up, and because
• 2:10:34
  Speaker 1: the efficiency is so high, The spacecraft can keep accelerating
• 2:10:39
  Speaker 1: long after a chemical rocket would have run dry. The
• 2:10:43
  Speaker 1: Dawn spacecraft used ion propulsion to orbit both Vesta and
• 2:10:48
  Speaker 1: Ceres in the asteroid belt, something chemically propelled spacecraft could
• 2:10:54
  Speaker 1: not have done without prohibitive fuel mass. The Hayabusa missions
• 2:11:00
  Speaker 1: used ion propulsion to reach and return from asteroids. For
• 2:11:06
  Speaker 1: robotic science missions, ion propulsion is genuinely transformative. For human missions,
• 2:11:13
  Speaker 1: it is essentially useless. Nobody is waiting three years to
• 2:11:18
  Speaker 1: slowly accelerate to barely useful speeds while the crew ages
• 2:11:22
  Speaker 1: inside a tin can. Ion propulsion solves the wrong problem
• 2:11:27
  Speaker 1: for crewed deep space travel. Solar sails are worth mentioning
• 2:11:32
  Speaker 1: because the concept is genuinely elegant. and the physics is real.
• 2:11:37
  Speaker 1: Sunlight exerts pressure. It is a tiny pressure. But in space,
• 2:11:43
  Speaker 1: tiny forces over long periods accumulate into real velocity changes.
• 2:11:49
  Speaker 1: A large enough reflective sail could use that pressure to
• 2:11:52
  Speaker 1: accelerate a spacecraft without any propellant at all. The problem
• 2:11:57
  Speaker 1: for a Jupiter mission is geometry. the intensity of sunlight
• 2:12:02
  Speaker 1: drops with the square of distance from the Sun. At Earth,
• 2:12:07
  Speaker 1: solar pressure is already small. At Jupiter, which is about
• 2:12:12
  Speaker 1: five times farther from the Sun, the intensity drops to
• 2:12:16
  Speaker 1: roughly 4% of what it is here. The sail would
• 2:12:21
  Speaker 1: need to be enormous to generate meaningful thrust that far out,
• 2:12:26
  Speaker 1: and by the time you have built a sail large
• 2:12:28
  Speaker 1: enough to matter at Jupiter's distance, AVA structure so large
• 2:12:34
  Speaker 1: it becomes its own engineering nightmare. Solar sails are promising
• 2:12:38
  Speaker 1: for missions in the inner solar system and for very
• 2:12:41
  Speaker 1: small probes. As a path to Jupiter on any useful
• 2:12:45
  Speaker 1: time scale, they fall short. Laser sails take the solar
• 2:12:50
  Speaker 1: sail concept and replace sunlight with a ground-based laser array.
• 2:12:56
  Speaker 1: This is the idea behind Breakthrough Starshot. which proposed using
• 2:13:00
  Speaker 1: powerful lasers to accelerate gram-scale probes to a fraction of
• 2:13:05
  Speaker 1: the speed of light for an interstellar mission. For a
• 2:13:09
  Speaker 1: Jupiter probe, you would not need anywhere near that scale.
• 2:13:15
  Speaker 1: A laser sail mission to Jupiter could theoretically work for
• 2:13:19
  Speaker 1: very small payloads, probes the size of a chip, carrying
• 2:13:23
  Speaker 1: sensors and little else. The laser array would accelerate the
• 2:13:28
  Speaker 1: probe to high velocity quickly and it would reach Jupiter
• 2:13:32
  Speaker 1: in weeks. The catch is the same one that limits
• 2:13:36
  Speaker 1: solar sails, scaling up. A gram scale probe cannot carry
• 2:13:42
  Speaker 1: meaningful science instruments, cannot orbit, cannot return data over long
• 2:13:47
  Speaker 1: distances with any bandwidth and certainly cannot carry a crew.
• 2:13:53
  Speaker 1: As a concept for interstellar exploration, or for ultra-miniaturized scout probes,
• 2:13:59
  Speaker 1: laser sails are fascinating. As a practical path to crew
• 2:14:04
  Speaker 1: Jupiter missions, the gap between the concept and the requirement
• 2:14:08
  Speaker 1: is vast. Fusion propulsion is where the numbers become almost disorienting.
• 2:14:16
  Speaker 1: A spacecraft powered by fusion, the same process that powers
• 2:14:20
  Speaker 1: the Sun, could theoretically reach Jupiter in weeks, not months. weeks.
• 2:14:28
  Speaker 1: The energy density of fusion fuel makes chemical propulsion look
• 2:14:32
  Speaker 1: like burning wet wood. Theoretical designs have been drawn up,
• 2:14:37
  Speaker 1: specific impulse numbers have been calculated, trajectory analyses have been run.
• 2:14:44
  Speaker 1: The physics is coherent, the engineering is not yet real.
• 2:14:49
  Speaker 1: Controlled fusion has been decades away from practical application for
• 2:14:53
  Speaker 1: roughly 60 years. And that timeline has not compressed as
• 2:14:58
  Speaker 1: quickly as anyone hoped. Recent progress in fusion research is genuine.
• 2:15:05
  Speaker 1: There have been real milestones at facilities like the National
• 2:15:08
  Speaker 1: Ignition Facility. But the distance between igniting a fusion reaction
• 2:15:14
  Speaker 1: in a laboratory and building a fusion engine that can
• 2:15:18
  Speaker 1: safely power a spacecraft is enormous. Fusion propulsion belongs in
• 2:15:23
  Speaker 1: the honest category of things that would transform everything about
• 2:15:27
  Speaker 1: the timeline to Jupiter, and that may genuinely arrive someday,
• 2:15:32
  Speaker 1: but that no one should count on within any specific
• 2:15:35
  Speaker 1: planning horizon. What this survey reveals is a spectrum. Nuclear
• 2:15:41
  Speaker 1: thermal propulsion is close, years away, not decades, if the
• 2:15:46
  Speaker 1: funding holds. Ion propulsion is already flying, but solves the
• 2:15:51
  Speaker 1: wrong problem for crews. Pulse propulsion is physically compelling, but
• 2:15:55
  Speaker 1: politically frozen. Solar and laser sails have niches, but not
• 2:16:01
  Speaker 1: the one we most need. Fusion propulsion is the prize
• 2:16:05
  Speaker 1: at the end of the road, but the road is
• 2:16:08
  Speaker 1: long and the end is not in sight. Each of
• 2:16:11
  Speaker 1: these technologies is real, each has genuine advocates, and each
• 2:16:16
  Speaker 1: faces barriers between current laboratory status and a flying spacecraft
• 2:16:21
  Speaker 1: that are measured not in years but in decades, which
• 2:16:26
  Speaker 1: is itself part of the honest answer to how long
• 2:16:29
  Speaker 1: it would take us to reach Jupiter. Start with what
• 2:16:33
  Speaker 1: we already know actually happened. New Horizons left Earth in
• 2:16:37
  Speaker 1: January of 2006 and passed Jupiter 13 months later. That
• 2:16:44
  Speaker 1: is not a theoretical number. That is a real spacecraft,
• 2:16:48
  Speaker 1: a real trajectory. a real clock. But New Horizons weighed
• 2:16:52
  Speaker 1: about 1,000 pounds, carried no braking fuel, and had zero
• 2:16:57
  Speaker 1: intention of stopping. It used Jupiter the way a billiard
• 2:17:01
  Speaker 1: ball uses a bumper. Angle in, angle out, keep moving.
• 2:17:06
  Speaker 1: That is the version of the trip that takes 13 months.
• 2:17:10
  Speaker 1: Everything else is harder. Could something get there even faster
• 2:17:14
  Speaker 1: than New Horizons? Probably. If you stripped a probe down
• 2:17:19
  Speaker 1: to its absolute minimum and launched it on the most
• 2:17:27
  Speaker 1: powerful rocket currently available, aimed at a favourable orbital window
• 2:17:32
  Speaker 1: with an aggressive trajectory, nine or ten months to Jupiter
• 2:17:37
  Speaker 1: starts to look conceivable. The physics allows it. The engineering
• 2:17:42
  Speaker 1: is painful, but not impossible. The catch is that a
• 2:17:47
  Speaker 1: spacecraft like that would be small. Tiny, really. Not much
• 2:17:53
  Speaker 1: bigger than a shoebox. And it would scream straight through
• 2:17:56
  Speaker 1: the Jovian system like a bullet through a doorway, collecting
• 2:18:01
  Speaker 1: a few hours of data before disappearing into the outer
• 2:18:05
  Speaker 1: solar system forever. Now ask what happens when the spacecraft
• 2:18:10
  Speaker 1: needs to stop. This is where the math turns brutal.
• 2:18:14
  Speaker 1: To enter orbit around Jupiter, a spacecraft has to shed
• 2:18:18
  Speaker 1: an enormous amount of velocity. Jupiter's gravity will have accelerated
• 2:18:24
  Speaker 1: it to somewhere around 130,000 miles per hour by the
• 2:18:28
  Speaker 1: time it arrives, and the spacecraft has to fire engines
• 2:18:32
  Speaker 1: hard enough to cancel most of that speed. That requires fuel.
• 2:18:37
  Speaker 1: a lot of it. And fuel has mass. And mass
• 2:18:42
  Speaker 1: requires more fuel to accelerate from Earth. The rocket equation
• 2:18:46
  Speaker 1: compounds against you at every step. A spacecraft designed to
• 2:18:51
  Speaker 1: break into Jovian orbit needs to carry so much propellant
• 2:18:56
  Speaker 1: that the entire mission architecture changes. Suddenly, you're not talking
• 2:19:01
  Speaker 1: about nine months. You're back to five or six years
• 2:19:05
  Speaker 1: even with more capable propulsion than we currently have. For
• 2:19:10
  Speaker 1: a human crew, the problem gets worse in every direction
• 2:19:13
  Speaker 1: at once. Humans need food, water, air, and enough shielding
• 2:19:19
  Speaker 1: to survive years in deep space radiation. A crewed spacecraft
• 2:19:24
  Speaker 1: to Jupiter would be massive, orders of magnitude heavier than
• 2:19:29
  Speaker 1: New Horizons. The most optimistic estimates using current chemical propulsion
• 2:19:35
  Speaker 1: put a round trip human mission at six to nine years,
• 2:19:39
  Speaker 1: not six to nine months, years. And that assumes everything
• 2:19:45
  Speaker 1: goes correctly, which deep space missions famously do not guarantee.
• 2:19:51
  Speaker 1: Here is where nuclear thermal propulsion becomes genuinely relevant rather
• 2:19:56
  Speaker 1: than just conceptually interesting. NASA and DARPA are actively developing
• 2:20:02
  Speaker 1: a nuclear thermal engine under the Draco program, with a
• 2:20:06
  Speaker 1: test flight targeted for the late 2020s. The basic idea
• 2:20:12
  Speaker 1: is straightforward. Instead of burning chemical propellants to generate thrust,
• 2:20:18
  Speaker 1: a nuclear reactor heats hydrogen to extreme temperatures and expels
• 2:20:23
  Speaker 1: it at roughly twice the exhaust velocity of conventional engines.
• 2:20:29
  Speaker 1: More exhaust velocity means more efficiency. More efficiency means either
• 2:20:35
  Speaker 1: a shorter trip or a lighter spacecraft or both. Applied
• 2:20:40
  Speaker 1: to a Jupiter mission, nuclear thermal propulsion could realistically cut
• 2:20:45
  Speaker 1: the transit time for an orbital mission down to somewhere
• 2:20:49
  Speaker 1: around two to three years. For a crewed round trip,
• 2:20:54
  Speaker 1: under OPT, I mystic conditions, you might be looking at
• 2:20:58
  Speaker 1: 3 to 4 years each way, if the technology matures
• 2:21:02
  Speaker 1: to the level mission planners are hoping for, that is
• 2:21:05
  Speaker 1: still not months. But it is a different problem than
• 2:21:08
  Speaker 1: the one we have today. The gap between those concept
• 2:21:12
  Speaker 1: studies and an actual flying spacecraft matters. Draco is a
• 2:21:17
  Speaker 1: real program with real funding, but it is a test
• 2:21:21
  Speaker 1: of a small demonstrator engine. Scaling that up to something
• 2:21:25
  Speaker 1: capable of propelling a crude Jupiter spacecraft is a separate
• 2:21:30
  Speaker 1: program that does not yet exist, with a budget that
• 2:21:35
  Speaker 1: has not been approved, on a timeline that nobody has
• 2:21:39
  Speaker 1: officially committed to. This is the part that tends to
• 2:21:43
  Speaker 1: get lost when people talk about what future propulsion could do.
• 2:21:49
  Speaker 1: The physics is sound. The engineering roadmap is plausible. The
• 2:21:54
  Speaker 1: funded development program is not there yet. So what is
• 2:21:57
  Speaker 1: the honest answer? With current technology and a robotic spacecraft,
• 2:22:03
  Speaker 1: the fastest realistic one-way trip to Jupiter is about 13 months,
• 2:22:08
  Speaker 1: and only under the specific conditions that made New Horizons possible. Light. Fast.
• 2:22:16
  Speaker 1: Not stopping. A robotic orbiter takes five to six years minimum.
• 2:22:22
  Speaker 1: A crewed mission with current propulsion would take the better
• 2:22:25
  Speaker 1: part of a decade round trip. A crewed mission with
• 2:22:29
  Speaker 1: nuclear thermal propulsion, if the technology reaches the necessary maturity,
• 2:22:35
  Speaker 1: might come down to three or four years each way.
• 2:22:39
  Speaker 1: A crewed mission that could make the trip in months
• 2:22:43
  Speaker 1: requires propulsion that is still theoretical. Fusion drives, laser propulsion,
• 2:22:50
  Speaker 1: concepts that live in serious peer-reviewed papers, but not in
• 2:22:55
  Speaker 1: any funded hardware program, could we see a star perish
• 2:22:59
  Speaker 1: as it occurred? Was it something we could reach before
• 2:23:03
  Speaker 1: our technology caught up to our ambition? The distances involved
• 2:23:08
  Speaker 1: in space travel have a way of making humanity feel
• 2:23:11
  Speaker 1: very small, and very slow, and very early in the story.
• 2:23:17
  Speaker 1: Getting to Jupiter faster is a problem of energy, not
• 2:23:21
  Speaker 1: of physics. And the line between those two things is
• 2:23:26
  Speaker 1: the line between what we currently know how to build
• 2:23:29
  Speaker 1: and what we can currently only calculate. Nobody would spend
• 2:23:34
  Speaker 1: years in a spacecraft getting to Jupiter to study Jupiter.
• 2:23:38
  Speaker 1: The planet itself is a sphere of gas and storms
• 2:23:42
  Speaker 1: with no surface to stand on. and radiation belts that
• 2:23:45
  Speaker 1: would destroy any unshielded human in hours. So the question
• 2:23:50
  Speaker 1: of why we would ever go there, given everything we
• 2:23:54
  Speaker 1: now know about how hard getting there actually is, deserves
• 2:23:58
  Speaker 1: a real answer. And the real answer is not Jupiter.
• 2:24:03
  Speaker 1: It never was. The real answer is orbiting about 400,000
• 2:24:08
  Speaker 1: miles above it. Jupiter has 95 known moons, Most of
• 2:24:14
  Speaker 1: them are small, captured rocks spinning in distant orbits, nothing remarkable.
• 2:24:21
  Speaker 1: But four of them, the Galilean moons, spotted by Galileo
• 2:24:25
  Speaker 1: himself in 1610, are worlds in their own right. And
• 2:24:31
  Speaker 1: one of them may be the most important place in
• 2:24:33
  Speaker 1: the solar system, at least from the perspective of a
• 2:24:37
  Speaker 1: species asking whether it is alone. That moon is Europa.
• 2:24:43
  Speaker 1: it is roughly the size of our own moon it
• 2:24:46
  Speaker 1: is covered in a shell of water ice and underneath
• 2:24:50
  Speaker 1: that ice sits a liquid ocean not a frozen one
• 2:24:56
  Speaker 1: a liquid one kept warm by the tidal forces Jupiter
• 2:25:01
  Speaker 1: exerts on the moon's interior as it pulls and flexes
• 2:25:05
  Speaker 1: the rock like bread dough that ocean is estimated to
• 2:25:08
  Speaker 1: contain more liquid water than every ocean lake and river
• 2:25:13
  Speaker 1: on Earth combined, twice over. Some models put it at
• 2:25:18
  Speaker 1: three times. And liquid water is not the only ingredient
• 2:25:22
  Speaker 1: that makes astrobiologists go quiet and serious when Europa comes up.
• 2:25:28
  Speaker 1: The ice shell is fractured. Deep cracks run across the
• 2:25:32
  Speaker 1: surface where the ice has split and refrozen. And in
• 2:25:37
  Speaker 1: some of those fractures, there are traces of salts and
• 2:25:40
  Speaker 1: organic compounds that suggest chemistry happening at the seafloor. Hydrothermal vents, possibly.
• 2:25:49
  Speaker 1: The kind of environment where, on Earth, life turns up
• 2:25:53
  Speaker 1: in places nobody expected it. Were we watching chemistry that
• 2:25:58
  Speaker 1: could produce life? That question drives the Europa Clipper mission,
• 2:26:04
  Speaker 1: which launched in 2024. But a robotic spacecraft, however sophisticated,
• 2:26:10
  Speaker 1: can only do so much. Here is the thing a
• 2:26:14
  Speaker 1: human crew can do that no probe can. When something
• 2:26:18
  Speaker 1: unexpected turns up in a sample, a human scientist on
• 2:26:22
  Speaker 1: site can stop, look again, and change the plan. That
• 2:26:27
  Speaker 1: sounds simple. It is not. The 45 minute communication delay
• 2:26:33
  Speaker 1: means a robotic mission operates on instructions written hours before
• 2:26:38
  Speaker 1: any given moment. When Curiosity found something unexpected on Mars,
• 2:26:44
  Speaker 1: mission scientists had to wait until the next planning cycle
• 2:26:48
  Speaker 1: to redirect it. For something as delicate and time-sensitive as
• 2:26:53
  Speaker 1: collecting samples from a fracture zone on Europa's ice shelf,
• 2:26:58
  Speaker 1: that delay could mean the difference between a discovery and
• 2:27:02
  Speaker 1: a missed opportunity. A human crew operates in real time.
• 2:27:07
  Speaker 1: That gap matters enormously. There is Ganymede, larger than the
• 2:27:13
  Speaker 1: planet Mercury, with its own magnetic field, the only moon
• 2:27:18
  Speaker 1: in the solar system known to generate one, and its
• 2:27:21
  Speaker 1: own subsurface ocean beneath an ice crust. The European Space
• 2:27:27
  Speaker 1: Agency's JUICE mission is on its way there right now.
• 2:27:32
  Speaker 1: What Ganymede's magnetic field implies about its interior structure is
• 2:27:37
  Speaker 1: still being worked out. A human geologist standing on the surface, drilling,
• 2:27:44
  Speaker 1: sampling and responding to what the drill actually finds, rather
• 2:27:49
  Speaker 1: than what the models predicted it would find, changes the
• 2:27:52
  Speaker 1: quality of the science entirely. And Callisto, the outermost of
• 2:27:58
  Speaker 1: the four Galilean moons, sits almost entirely outside Jupiter's worst
• 2:28:03
  Speaker 1: radiation belts. It is geologically quiet. It has water ice
• 2:28:09
  Speaker 1: on the surface. Some researchers have pointed to Callisto as
• 2:28:13
  Speaker 1: the most practical staging point for human operations in the
• 2:28:17
  Speaker 1: Jovian system, close enough to Europa and Ganymede to mount
• 2:28:21
  Speaker 1: crude excursions, far enough from Jupiter to keep radiation exposure survivable.
• 2:28:28
  Speaker 1: Compare this to what is happening around Saturn. Titan has
• 2:28:32
  Speaker 1: a thick nitrogen atmosphere, lakes of liquid methane on its surface,
• 2:28:37
  Speaker 1: and chemistry happening there that resembles a very cold, very
• 2:28:41
  Speaker 1: slow version of what Earth's early atmosphere may have looked like.
• 2:28:46
  Speaker 1: Enceladus is shooting water vapor from cracks in its south
• 2:28:51
  Speaker 1: pole directly into space, material from its subsurface ocean. that
• 2:28:57
  Speaker 1: a spacecraft could fly through and sample without even landing
• 2:29:02
  Speaker 1: the outer solar system is not empty it is full
• 2:29:07
  Speaker 1: and the reason we have not been out there with
• 2:29:09
  Speaker 1: human crews yet is not lack of interest it is
• 2:29:14
  Speaker 1: the math we spent the last 18 sections of this
• 2:29:17
  Speaker 1: discussion walking through but here is the real weight of
• 2:29:21
  Speaker 1: the question there are two futures on offer in one
• 2:29:25
  Speaker 1: of them Humans stay in the neighborhood, the Moon, Mars,
• 2:29:31
  Speaker 1: maybe the asteroid belt, and robots go everywhere else. The
• 2:29:36
  Speaker 1: robots get better, the data gets richer, and we learn
• 2:29:40
  Speaker 1: everything there is to learn about Europa's ocean from a
• 2:29:44
  Speaker 1: distance of 400 million miles. In the other future, humans
• 2:29:49
  Speaker 1: eventually go themselves, not because robots have failed, but because
• 2:29:55
  Speaker 1: there is a difference between exploring a place and being
• 2:29:58
  Speaker 1: in it, between measuring a world and standing on one.
• 2:30:04
  Speaker 1: The decision to send humans to the Jovian system is
• 2:30:07
  Speaker 1: not a scientific decision. It is a civilizational one. It
• 2:30:13
  Speaker 1: is a statement about how far the definition of home
• 2:30:16
  Speaker 1: is allowed to extend. Every mission architecture we have ever
• 2:30:20
  Speaker 1: built for Jupiter has been a choice about what comes next.
• 2:30:25
  Speaker 1: Pioneer was a test. Voyager was a revelation. Galileo was
• 2:30:31
  Speaker 1: a commitment. What would a human mission be? The journey
• 2:30:36
  Speaker 1: to Jupiter is not really about Jupiter at all. It's
• 2:30:40
  Speaker 1: about what lies in orbit around it, and what the
• 2:30:43
  Speaker 1: decision to go there would say about what kind of
• 2:30:46
  Speaker 1: species we intend to be. The answer to how long
• 2:30:49
  Speaker 1: it would really take us to reach Jupiter is not
• 2:30:52
  Speaker 1: a single number, and the reason it isn't a single
• 2:30:56
  Speaker 1: number is the most interesting thing about the question. Here
• 2:31:00
  Speaker 1: is what the Honest Range looks like. A robotic spacecraft
• 2:31:05
  Speaker 1: built for speed and nothing else. No need to slow down,
• 2:31:09
  Speaker 1: no science instruments to protect, no orbit to enter. can
• 2:31:14
  Speaker 1: make the trip in about 13 months under ideal conditions.
• 2:31:19
  Speaker 1: That is what New Horizons did. It was the fastest
• 2:31:24
  Speaker 1: launch from Earth ever attempted at the time. It flew
• 2:31:28
  Speaker 1: past Jupiter without breaking at all, and it still took
• 2:31:32
  Speaker 1: over a year. That is the fastest end of the range.
• 2:31:37
  Speaker 1: The slow end is six years. That is what Galileo needed.
• 2:31:42
  Speaker 1: looping past Venus and Earth twice just to build up
• 2:31:46
  Speaker 1: enough speed to reach a planet that was, at its closest,
• 2:31:51
  Speaker 1: about 365 million miles away. Six years to cross a
• 2:31:57
  Speaker 1: distance that light covers in 43 minutes. Both of those
• 2:32:01
  Speaker 1: numbers are correct. Neither one answers the question. What actually
• 2:32:07
  Speaker 1: determines the number is a set of choices. Are you
• 2:32:11
  Speaker 1: stopping or flying past? Stopping costs an enormous amount of fuel.
• 2:32:17
  Speaker 1: That fuel adds mass. That mass requires more fuel to move.
• 2:32:22
  Speaker 1: The spiral compounds quickly, and by the time the math settles,
• 2:32:27
  Speaker 1: you are looking at a spacecraft that takes years longer
• 2:32:31
  Speaker 1: to arrive just because it needs to break at the end.
• 2:32:35
  Speaker 1: Are you launching at the right window? Jupiter's alignment with
• 2:32:39
  Speaker 1: Earth shifts constantly. Miss the optimal window and the trajectory
• 2:32:44
  Speaker 1: gets worse. More fuel, more time, or both. Are you
• 2:32:49
  Speaker 1: carrying humans? Then the math changes entirely, because humans need food,
• 2:32:55
  Speaker 1: and oxygen, and medicine, and exercise equipment, and radiation shielding.
• 2:33:01
  Speaker 1: And all of that mass adds up to a spacecraft.
• 2:33:05
  Speaker 1: that nothing we have ever built could actually launch in
• 2:33:08
  Speaker 1: its current form. For a human crew using the propulsion
• 2:33:12
  Speaker 1: technology that exists right now, the round trip to Jupiter
• 2:33:16
  Speaker 1: would take somewhere between six and nine years at minimum.
• 2:33:20
  Speaker 1: That assumes everything works. It assumes no mission extensions, no
• 2:33:26
  Speaker 1: navigational corrections that burn extra fuel, no delays waiting for
• 2:33:31
  Speaker 1: the return alignment window to open. six to nine years
• 2:33:35
  Speaker 1: in deep space, past the protection of Earth's magnetic field,
• 2:33:40
  Speaker 1: absorbing cosmic radiation the entire way, astronauts returning from six-month
• 2:33:46
  Speaker 1: stints on the International Space Station sometimes need help standing
• 2:33:50
  Speaker 1: up when they land. Now multiply that by a factor
• 2:33:54
  Speaker 1: of ten. Nuclear thermal propulsion could change this. If Draco,
• 2:34:01
  Speaker 1: The joint NASA and DARPA program working on nuclear thermal
• 2:34:05
  Speaker 1: engines reaches a flying spacecraft by the late 2020s as planned,
• 2:34:11
  Speaker 1: and if that technology matures enough to scale up for
• 2:34:14
  Speaker 1: a crewed mission, the travel time to Jupiter could potentially
• 2:34:18
  Speaker 1: drop to somewhere around three to four years each way.
• 2:34:23
  Speaker 1: That is still an enormous commitment, but it is a
• 2:34:27
  Speaker 1: different order of commitment than nine years And the difference
• 2:34:32
  Speaker 1: between those two numbers could be the difference between a
• 2:34:35
  Speaker 1: mission that humans can survive and one that they cannot.
• 2:34:40
  Speaker 1: More advanced concepts, fusion propulsion, laser sails, nuclear pulse, could
• 2:34:47
  Speaker 1: push the timeline into months for a crewed mission. The
• 2:34:51
  Speaker 1: physics allows it. The technology does not exist yet. and
• 2:34:55
  Speaker 1: none of the programs working toward it are funded at
• 2:34:58
  Speaker 1: the level that would produce a flying spacecraft within any
• 2:35:02
  Speaker 1: near-term window. This is worth sitting with. The speed is
• 2:35:08
  Speaker 1: not forbidden by any law of nature. It is forbidden
• 2:35:12
  Speaker 1: by the gap between what we have decided to build
• 2:35:15
  Speaker 1: and what the problem actually requires. Every number in this
• 2:35:20
  Speaker 1: entire conversation sits at the intersection of two things. On
• 2:35:24
  Speaker 1: one side, is the physics, orbital mechanics, rocket equations, radiation belts,
• 2:35:31
  Speaker 1: communication delays. That side does not negotiate. The distance to
• 2:35:37
  Speaker 1: Jupiter is what it is. The energy required to cross
• 2:35:41
  Speaker 1: it quickly is what it is. On the other side
• 2:35:45
  Speaker 1: is human ambition, which is the variable. How much are
• 2:35:49
  Speaker 1: we willing to invest How much time are we willing
• 2:35:53
  Speaker 1: to spend developing propulsion systems that don't yet exist? How
• 2:35:58
  Speaker 1: seriously do we take the moons of Jupiter, Europa's buried ocean,
• 2:36:03
  Speaker 1: the possibility of something living there, as reasons to go
• 2:36:08
  Speaker 1: rather than as interesting facts to collect from robotic data streams?
• 2:36:13
  Speaker 1: The real answer to this question is not 13 months.
• 2:36:17
  Speaker 1: It is not six years. It is a choice that
• 2:36:20
  Speaker 1: hasn't been made yet. Every timeline attached to a Jupiter
• 2:36:25
  Speaker 1: mission is a reflection of a decision about how much
• 2:36:28
  Speaker 1: that destination matters to us. And right now, the honest
• 2:36:33
  Speaker 1: answer is that we haven't decided it matters enough to
• 2:36:37
  Speaker 1: build the tools that would get us there in a
• 2:36:39
  Speaker 1: timeframe a human crew could endure. What we have done
• 2:36:44
  Speaker 1: is send robots. Pioneer made it in 21 months. The
• 2:36:50
  Speaker 1: Voyagers reshaped everything we knew about the outer solar system
• 2:36:54
  Speaker 1: in under two years. Galileo orbited Jupiter for nearly a
• 2:36:59
  Speaker 1: decade on a six-year cruise. Juno is still out there,
• 2:37:04
  Speaker 1: still returning data, slowly being eaten by radiation that has
• 2:37:09
  Speaker 1: no equivalent anywhere else our spacecraft have ever been. Each
• 2:37:14
  Speaker 1: of those missions arrived carrying questions nobody had thought to
• 2:37:18
  Speaker 1: ask yet, and left with answers that made the questions bigger.
• 2:37:23
  Speaker 1: On any clear night, if you know where to look,
• 2:37:27
  Speaker 1: Jupiter is one of the brightest objects in the sky,
• 2:37:31
  Speaker 1: close enough to see its moons with a pair of binoculars,
• 2:37:35
  Speaker 1: far enough away that we haven't figured out how to
• 2:37:38
  Speaker 1: get there in less than a year. And the distance
• 2:37:41
  Speaker 1: between those two facts is where the real story lives.
• 2:38:04
  Speaker 1: Thank you.