3310: Rejected Space Mission Profiles

Rejected Space Mission Profiles

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Title text: Although NASA agreed that Voyager 2 'seemed lonely' they decided against launching a companion orbiter mission after further measurements indicated that the spacecraft actually preferred the peace and quiet.

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Explanation

This is one of 64 incomplete explanations: This page was created by A WAYWARD SPACE PROBE. Mass required for Pluto mission needs improved explanation - mass of what? Don't remove this notice too soon. You can help by editing the explanation!

This comic depicts four space missions which were supposedly rejected, because each would be a bad idea.

The "Jupiter Rover" mission depicts a Mars rover-like vehicle on Jupiter. As the rover is a wheeled vehicle, it can only operate on a body with a solid surface such as Mars. Jupiter is a gas giant and it is unknown whether it has a solid surface, as none of our instruments could measure deep enough into its atmosphere. Even if it has a solid core, it would be under a layer of metallic hydrogen, which a rover would also struggle to survive in. In addition, Jupiter has winds in excess of 1,000 km/h, atmospheric pressures exceeding 1 million atm and temperatures exceeding 24,000 K; any rover made with current technology and materials would be destroyed upon deployment before even reaching the metallic hydrogen layer. The Galileo probe, specifically designed to penetrate the Jovian atmosphere, was destroyed when the atmospheric pressure was approximately 24 atm.

The "Voyager 2 Orbiter" mission would send a probe to orbit Voyager 2, which is itself a space probe. As Voyager 2 was built on Earth, its size, shape and features were already well known to NASA before it was launched into space, making this mission pointless; it would also interfere with some of Voyager’s own still-ongoing measurements of its current environment. Orbiting Voyager 2 would also be a non-trivial task. Voyager 2 has a mass of 722 kg and a minor axis of 2.5 m. Escape velocity for any unpowered orbit would be 0.68 meters per hour, and the relative mass of the ‘orbiter’ is likely to form a binary system between the two objects. Trivial fluctuations in velocity would lead the co-orbiting pair to be unstable; these are unavoidable due to the asymmetry of the Voyager probe. Powered orbits would require non-trivial mass for station keeping. In any case this mission would require somehow catching up with the second-furthest human made object there is, which would have five or more decades of head start on any mission yet to be launched. Randall has previously discussed sending a mission to Voyager 1 in the what if? article Voyager.

The "Crewed Pluto Flyby" mission would send astronauts to pass by Pluto (presumably in order to collect scientific data about the dwarf planet). However, the mission as depicted would have the astronauts pass Pluto and continue out of the solar system, apparently with no way of returning to Earth. In addition, current timeframes for a Pluto flyby, including gravitational assists with Jupiter and Saturn as shown, are on the order of a decade. Sustaining astronauts on such missions for years requires on the order of 1 kg/person/day additional payload for life support. The entire mass of the New Horizons probe, the only spacecraft thus far to perform a Pluto flyby, would be required each year for each astronaut. Due to the limits of the Tsiolkovsky rocket equation, this exceeds the combined payloads of all space missions to date. There are very immature concepts for human exploration into interstellar space, using a combination of advanced propulsion (possibly requiring novel developments in material science or even physics itself), hibernation and/or multiple generations of crew.

The "Neptune Core Return" mission would somehow extract the solid core deep beneath Neptune's gaseous atmosphere (possibly a pun about taking core samples), then tow it back to Earth. The core of Neptune is estimated to be on the order of the size of the Earth, so any such towing out of Neptune's gravity well would require impractical amounts of energy. The atmospheric pressure near the Neptunian core is estimated to exceed 100,000 atm, meaning it would require significant advances in technology for a probe to survive descent to Neptune's core. If Neptune's core were somehow returned to Earth, the collision would destroy all life on our planet. Space probes have returned material from solar system bodies beyond the Moon, but only in amounts less than 200 g. It is believed that there is a great deal of diamond surrounding Neptune's rocky core, but even if some of that could be retrieved, its value would not offset the expense of the mission very well. Diamond is valuable on Earth because monopolistic suppliers artificially create a relative scarcity of availability, and if it became available by the ton, its value by weight would plummet.

The title text claims that the Voyager 2 orbiter project was scrapped because the probe actually prefers to be alone. Voyager does not have any such preferences, as it is not sentient^{[citation needed]} (although a successor to it became so in the film Star Trek: The Motion Picture). This may be a reference to Al Worden's experience of enjoying being alone in the lunar orbiter during the Apollo 15 mission, which Randall has used as a closing remark of a What if? article.

Trivia

• Pioneer 9, Pioneer 10, and the Jupiter Icy Moons Explorer also became sentient in the fictional narrative 17776 aka What Football Will Look Like in the Future.

Transcript

[Caption above the panels:]

Rejected Space Mission Profiles

[Four panels in a 2x2 grid.]

[Upper left panel:]

Jupiter Rover

[A Mars rover-type vehicle tumbles through the gaseous clouds of Jupiter.]

Rover: AAAAA!

[Upper right panel:]

Voyager 2 Orbiter

[A cubesat is shown in an orbit around Voyager 2.]

[Lower left panel:]

Crewed Pluto Flyby

[A diagram depicting part of the solar system, with the sun and four planets, probably Earth, Jupiter, Saturn, and Pluto, each with curves indicating part of their orbits. A dotted line shows the path of a spacecraft getting gravity assists off Jupiter and Saturn and passing Pluto.]

Voice from spacecraft: Uh, bye, I guess.

[Lower right panel:]

Neptune Core Return

[A rocket is shown above the surface of Neptune. On two sides there are arms extending from the rocket. At the ends of the arms are cables connected to an enormous rock that's being pulled out of the planet, which is dragging the gas of the planet with it.]

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Discussion

Assuming the Voyager 2 orbiter is much lighter than the Voyager 2, and is orbiting at a distance of 10 meters, what would be the period? Hours? Days? Months? -- Dtgriscom (talk) 20:54, 12 October 2026 (UTC)

Simply use the quantitative version of Kepler’s 3^rd law, $\frac{a^3}{T^2}=\frac{GM}{4{\pi }^2}$: using $G=6.67\cdot 10^{-11}\mathrm{N}{\mathrm{m}}^{\mathrm{2}}\mathrm{k}{\mathrm{g}}^{\mathrm{-}\mathrm{2}}$, $M=825.5\mathrm{k}\mathrm{g}$, and the estimate $a=(10+1)\mathrm{m}$ (10 m distance from Voyager 2 plus about 1 m radius of Voyager 2 itself), and solving for $T$ yields $T\approx 976,894\mathrm{s}\approx 11.3\mathrm{d}$, so less than a fortnight. The orbital speed would be $v\approx 7\cdot 10^{-5}\mathrm{m}/\mathrm{s}$, or 1 millimetre per 14.13 seconds, or (for imperialists) 1 inch per 6 minutes. Feel free to provide better numbers. M. L. Juhos 134.60.67.135 08:39, 13 October 2026 (UTC)

I feel like the word 'simply' is doing some heavy lifting there. 86.22.132.121 09:04, 13 October 2026 (UTC)

They aren't wrong. It's pretty much what we used to call "plug and chug". So long as you have the equation and all the numbers but one, you can find the last one through simple algebraic manipulation. 130.76.187.47 11:52, 13 October 2026 (UTC)

So long as you have the equation and know what the terms mean - that's quite a large assumption. 86.22.132.121 13:38, 13 October 2026 (UTC)

The idea of future space missions for the specific purpose of studying past historical space missions makes for a fascinating concept. Space archeology. 2603:8001:9401:3B00:1941:3516:7199:CA6E 23:10, 12 October 2026 (UTC)

The text says about the payload of the Pluto flyby, "this exceeds the combined payloads of all space missions to date." Is that actually correct? I mean, assuming 10 years as in the text, 2 astronauts so they don't go insane, and the same delta-v as for New Horizons, it seems like you would need only 20 times more fuel that New Horizons used, or somewhat more because the spacecraft would be larger. Which is of course a lot, and beyond any current rocket, but I wouldn't think it's more than all space missions to date. As I understand it, the rocket equation blows up for larger delta-v, less so (i.e., only linearly) for a larger payload. But I'm no rocket scientist so maybe I've got it wrong. DKMell (talk) 00:41, 13 October 2026 (UTC)

Delta-v isn't a simple "this engine gives this amount of delta-v, regardless of what it's attached to". It's related to the thrust efficiency, the mass it is carrying and how long you thrust for. Somewhat simplifying, double the payload and you may need to either thrust twice as much (say double the engines) or twice as fast (engineer the engine power up) or twice as long (what may have been a minute of thrust is now two minutes) for any given phase of flight. Which means more fuel and fuel-carrying/conveying infrastructure. Which, as you can see from the rocket equation, means you now need even more fuel for the prior phase(s) of flight, and fuel for the phases before that. Repeat until you get back to the initial launch-mass.

I haven't done the maths, myself, but "only 20 times more fuel" is probably a gross understatement. If that's an assumption based entirely upon the habitable part of the fully-equipped manned-mission being 'only' 20 times the weight of the 'sharp end' of New Horizons (which, for ten years and two individuals... I also think is likely an understatement) then, yes, I think you're wrong. Couldn't tell you how wrong, but probably by a lot. 78.151.45.31 20:31, 13 October 2026 (UTC)

DkMell is correct. The rocket equation is linear in the payload mass. Consider the case of simultaneous launching 20 times 1000kg payloads and rendezvousing during the trip. If you launch in parallel the rendezvous required minimal maneuvering fuel. Considered another way if the rocket equation cared about distributed or monolithic payloads there would be some very interesting mission profiles and NASA et. al. would be far more interested in distributed launch.

As for total mass we have easily launched at least 20 times New Horizons mass (~1000kg). JUICE (6000kg), Europa Clipper (5800kg), Cassini (5600kg), and JUNO (3600kg) are sufficient. Alternatively, the rocket that launched New Horizons, Atlas V 551, has been launched 23 times. There is very little doubt we could launch 20tonne to Pluto if somebody was willing to pay for it. 76.180.39.133 02:28, 19 October 2026 (UTC)

If in the last panel, you replace "Neptun" with "Uranus"...OK, it would be distracting. 2A02:2455:1960:4000:8562:4865:FC8A:C735 11:42, 13 October 2026 (UTC)

The picture in the Neptune panel is actually quite correct. Wikipedia claims Neptune to have a mass of about 10²⁶ kg, and it's core is said to have 100% to 150% of the mass of Earth (which is about 6⋅10²⁴ kg). So, the core has only 6 to 9 percent of the total planetary weight, the rest is atmosphere. 195.49.224.20 12:02, 13 October 2026 (UTC)

The explanation talks about the pressures the probe would be subjected to, but I was wondering: assuming that we have solved the immense energy requirements to hoist Neptune's core, and the tensile strength to have a tow cable that could hoist it the way the image depicts, would it be "easier" to have several probes trawl a large net through Neptune and catch the core that way? I assume it's easier to make a cable that can withstand crushing atmospheric pressure than a probe that can hold up to the same, but I don't know whether the tidal effects on such a net would be worse than the strain of dragging something that has as much mass as the earth, if not slightly more, out of Neptune's gravity well (or well, 90%-95% of it after you take out the mass of the core itself) 57.140.32.42 12:56, 13 October 2026 (UTC)

One obvious problem is that if you somehow managed to drag the core around, then there'd be a significant amount of the non-core planet that would be pulled around with it. Do it slow enough, so that you don't let the atmosphere spill out of the Hill Sphere of the core-alone, and you're effectively moving the whole planet. With perhaps a bit of wobbling as it settles into its new core-based movement. You'd have to pluck the core out extremely fast to effectively do a 'tablecloth trick' and leave everything but the core (and maybe the atmosphere that ends up caught upon the core) where it was, to become a coreless cloud (initially, until it starts collapsing and/or dispersing in response to the missing core) staying in the original planetary track.

So you don't just need the energy to move the core (technically, you could just use a small continuous force and eventually you would have significantly moved it, in an otherwise free-floating situation and space having virtually no friction), you need a lot more energy to suddenly move the core out of the rest of the planet. 78.151.45.31 20:48, 13 October 2026 (UTC)

Why haven't we done some kind of gas giant rover? Not with wheels of course, but a blimp maybe? And maybe not Jupiter because of the intense magnetic fields and radiation, but possibly Saturn? 71.10.152.142 13:43, 13 October 2026 (UTC)

it would probably explode or fall in 107.1.219.44 14:25, 13 October 2026 (UTC)

There's no reason why you can't design a Saturnian Blimp that would settle nicely at some altitude/depth or other within the atmosphere of Saturn. Though you may have difficulty in resisting crushing in the extreme depths or (like weather balloons) pop at near-space heights, and you also need to be tough enough to deal with expected windshear/etc. And getting to the ideal working 'height', from space, before deployment in its final form (assuming it isn't a 'spaceproof' balloon that can somehow survive entering the atmosphere and then 'settle' at its effective working height) might well be tricky. But these are all considerations that people are probably already taking account of. 78.151.45.31 20:55, 13 October 2026 (UTC)

Blimps on gas giants are tricky, considering that their atmosphere is mostly hydrogen – good luck choosing a lifting gas lighter than that! That's the reason why blimps for Venus are a much more promising concept (you could use regular air as a lifting gas). --2001:A62:58A:801:1E74:A59A:D07E:537E 09:29, 17 October 2026 (UTC)

Third comic recently about space probes (after 3304: Jupiter Icy Moons Explorer and 3308: Juice), and ironically given the bottom text, the only of the three about one that doesn't become sentient. Chaotic Enby (talk) 22:51, 13 October 2026 (UTC)

When I think "core return", that makes me think of some of the more expensive auto parts that can be remanufactured. The "core" is the old part and returning that after replacing it with a new or remanufactured part will give you a little bit of money back. It keeps the parts out of the junk yard where they can be reused or properly recycled. That's what I thought the core return panel refers to. 130.76.25.47 13:02, 14 October 2026 (UTC)
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