3294: Asteroid Mission

Asteroid Mission

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Title text: Lander, this is Houston. There's been a request that you turn clipping back on and instead set the mass to 1kg. The theorists believe that will be pretty funny.

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Explanation

This is one of 50 incomplete explanations: This page was created by a bot with a mass of 0.000001 kg. Don't remove this notice too soon. You can help by editing the explanation!

The comic shows the scenario of an asteroid on a collision course with the Earth, and the crewed space mission sent to prevent this (similar to the films Armageddon, Deep Impact and various other stories not dating from 1998). Typically, such fictional missions are sent to blow the offending objects up or, more realistically, redirect them, but here they are attempting to gain access to the asteroid electronically and change the way physics applies to it in order to avert the collision.

In video games, "noclip mode" is a common cheat code where the player can move their character through normally impenetrable objects — usually walls and obstacles, as well as ceilings and floors if the cheat code also allows the character to fly. The etymology of the term "clipping" in this context is a little complicated, as it originally referred to the graphics, not to the collisions between objects, although the code used to decide whether something in the game environment is visible within a given display/viewport shares many features with typical 'hitbox' calculations and so may be treated as separate aspects of the same principle. In general, cheat codes like this are used to shortcut some aspects of gameplay testing, and are then left in either as an Easter Egg or just because they have been forgotten. The term "no clipping mode" as a cheat code goes as far back as Doom from 1993.

By enabling noclip on an asteroid headed for Earth, the crew eliminate interaction between the asteroid and Earth, thus theoretically saving the planet. However, due to them both being free-floating the astronauts may now be unable to walk back across the asteroid to return to the ship. This problem could be trivial to solve if they were tethered to the ship or possessed personal propulsion units, but the mission does not seem to have had enough foresight to include either of these (unless there are propulsion units left un-drawn due to the stick figure art style), leaving open the question of what other preparations the full mission involved beyond just getting into the position of hacking into the asteroid.

The title text is a transmission from Mission Control to the astronauts. Mission Control for manned NASA space missions since 1965 (the Christopher C. Kraft Jr. Mission Control Center) is located in Houston, Texas, and famously uses the city’s name as its callsign, which means the mission in the comic is probably a NASA mission too. Mission Control suggests that rather than enabling noclip, the astronauts should instead just reduce the asteroid's mass to 1 kg. If the asteroid is assumed to have a volume of about 1000 km³, this would reduce its density to 10^-15 g/cm³ and its energy to a few MJ. This relatively small amount of energy would be rapidly dissipated by friction with the outer atmosphere. The asteroid would then float at an altitude where the density of the atmosphere matches that of the asteroid, probably until solar wind blew it away. During this event, the asteroid would rapidly approach the Earth, looming large in the sky, presumably terrifying much of the world's population. Their claim that this would be "pretty funny" would depend significantly on your sense of humor.

Transcript

This is one of 34 incomplete transcripts: Don't remove this notice too soon. You can help by, editing the transcript!

[Miss Lenhart, as a news anchor, sits at a desk, with an image of a rocket behind her.]

Miss Lenhart: The asteroid is headed for Earth, but a mission has been launched to intercept it.

[Cueball and Megan, wearing space helmets, are walking from a lander on a rocky asteroid, carrying some equipment.]

[A laptop is on the ground, and Megan plugs a cable from the laptop into the asteroid.]

[Cueball types into the laptop.]

Console: >noclip on

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Discussion

First time I've ever gotten the first comment 128.119.202.28 17:15, 4 September 2026 (UTC)

Breaking News: The XKCD Store IS BACK 144.121.25.46 17:18, 4 September 2026 (UTC)

How did I do with the transcript? Majordesmosnerd (talk) 17:35, 4 September 2026 (UTC)

I don't think the "Roshe limit" part is right. Whatever mass the asteroid has. The Roshe limit depends on distance, and any asteroid will be below the Roshe limit at some point. But so what? It will still hit the Earth. Roshe limit is relevant to orbiting bodies, not impactors. Instead, reducing the mass to 1kg will also reduce the Kinetic energy of the impact. The kinetic energy would be quickly lost in friction with the outer atmosphere, and the asteroid (which would be much less dense than helium) would then float with neutral boyancy: something that would be pretty funny! I've edited - hope it makes sense.92.238.26.192 17:46, 4 September 2026 (UTC)

I don't think the "Roshe limit" part is right. You're right: Roche limit . 158.173.67.243 18:10, 4 September 2026 (UTC)

If it stayed the same strength and stiffness but was 1kg, no Roche limit nor atmospheric impact would damage it. But it wouldn't have a chance to collide in the first place! Sunlight would eject it at about one g per km^2 of cross sectional area. Too bad, as the material would make an excellent superluminal communication medium. Speed of sound scales as 1/sqrt(density). A 1km^3 regional threat (still way too little gravity to walk on so it may be much bigger) would be made a trillion times less dense, or a million times faster speed of sound (assuming an average density of water, asteroids are porous). Silicates have about 5e3 m/s speed of sound. It would become 5e9m/s, about 16 times lightspeed! 2607:FB90:8E00:DF30:A858:41FF:FE1D:4A01 21:58, 5 September 2026 (UTC)

The SoS relies upon the stiffness, as well as the density, of course. But also only really applies to solids, that way. Water transmits sound 4x or more that of (sea-level) air, with water being far more dense than air (comparison between different phases also matters). Vastly less-dense water (in whatever hand-wavy manner) probably wouldn't improve upon that, if higher pressure also does that, in water. Though of course density-in-solids is what you're probably talking of here, assuming that it's a rigid body and not a loose collection of rubble that could effectively be considered a kind of fluid nominally at rest.

Regardless of this, there's still no obvious way for sound to go faster than light. The oscillation of a particle even impossibly tightly bound to a neighbouring particle by some ultimate super-stiff bond still cannot induce its relative motion to the partner-particle at speeds greater than c, producing an upper-limit to how fast sound can get that's just as limited as any of the fundamental forces that might be currently bind those particles. 81.179.200.82 22:25, 5 September 2026 (UTC)

Stiffness here means resistance to compression. Water is far less compressible than air which more than makes up for its higher density. Solids also resist shear, which gives a separate speed of sound for shear waves.

You are right that physics prevents superluminal sound speed. But the cheat code cheats! It doesn't just reduce the mass of all elementary particles in the asteroid. Doing so would make it explode because the atoms would become much bigger, that's no good! Instead, the cheat, presumably, preserves all bulk properties besides mass. Even though this means an impossible material. 2601:644:8101:8DA0:55A5:AC66:3EA6:7767 07:05, 6 September 2026 (UTC)

Wasn't that the plot of a Stargate episode? Angel (talk) 17:55, 4 September 2026 (UTC)

Exactly my thinking. (Looked it up, Season 5 "Fail Safe".) Though not sure it can be linked to this comic in the Explanation, might as well mention it here. 81.179.200.82 19:26, 4 September 2026 (UTC)

If I'm not mistaken, the people on the asteroid would fall through it, along with the rocket, when they activated noclip, and most likely would die. SomebodyElse (talk) 18:00, 4 September 2026 (UTC)

If the asteroid retains it mass, and everything non-asteroid found itself no longer on a solid surface, then they'd fall towards the centre (the same centre, at the same rate of motion, so might be the way that the crew get back to the craft, as they converge?) and then ballistically travel to the same 'surface level' on the other side of the now-intangible mass. They'd oscillate back again, etc. As they're being noclipped (not noclipping themselves, but nothing tangible to clip with except themselves), I don't see why they'd then die just from doing this, although whether or not it'd be 'fun' to do I don't know. Might depend upon the people. - Assuming they took the opportunity to get back with their lander, I suspect they'd have enough ascent-power to get away from the asteroid, whether from when they're at its surface or starting at any other point of their 'straight through orbit', so if the mission isn't entirely designed as a one-way trip then I suspect they get back.

If the noclip also renders its mass moot (not implied, if any possible change in mass is a completely different cheat-code as suggested, but it might be a secondary effect) then they and their lander are now back on the way to Earth in the same impacting trajectory, but that's an even easier way to get back to Earth, assuming they ever had any additional means/intention of getting back to Earth safely. (Perhaps, with enough time, the masses of the lander and the expedition might draw them back together in lieu of any other traditional way of deliberately floating back together. Or they could certainly throw the equipment away from the lander to themselves get pushed back towards it as a reciprocal motion.

(And now I'm having deja vu of some 'what if'-like thing, that may not actually be xkcd at all, about how well drifting astronauts might need to do this under a similar time-constraint. And the vague recollection that that scenario was explained as unlikely to work in time. But cannot right now recall the circumstances or context of the scenario very much at all.)

Anyway, long story short, they're not going to die from the noclipping. Which is not to say that they also have a way to survive the post-mission situation and return home. 81.179.200.82 19:26, 4 September 2026 (UTC)

I meant that they would be unable to return to their ship, and suffocate due to a limited supply of oxygen, or being shot into space unable to return, etc. SomebodyElse (talk) 20:25, 4 September 2026 (UTC)

Also, recall gravity is the one fundamental force we don't understand SomebodyElse (talk) 20:51, 4 September 2026 (UTC)

Would the noclip setting affect the ship and astronauts too? If yes, how would they get home? (Wait until asteroid flew through Earth, then turn noclip back off before leaving?) If no, they'd have quite a time getting back to the ship, not being able to push against the asteroid! 162.10.127.42 18:07, 4 September 2026 (UTC)

In contrast to the above lengthy response, if noclipping 'groups' everything and sends everything asteroid connected, then, yes, they can effectively do as with the Stargate example (except in reverse... in which they extended the ship's 'noclip' to the asteroid).

The other possibility is that every subsystem that is sufficiently mechanically attached is grouped in separate noclipping entities, in which case (with mass still applying) loose boulders on the surface may fall through the 'asteroid mass' (and lander/expedition members), but not interact with anything else falling through, like a lot of point-masses that never actually accumulate together. Could be some weird activity as N-body issues eject some of these entities entirely with extra gravitational energy gained from others that 'orbit' much lower than they started to 'orbit'. Might be a tricky situation that cannot be ever 'de-noclipped' to leave the astronauts neither deep within the asteroid or floating way out in space (nowhere near the lander that they also need to have 'reclipped', at least w.r.t. them). And this is probably the most chaotic and least helpful way to have implemented this 'cheat', and yet still wish to survive the mission.

The comic doesn't really show which scenario it is, though. Apart from getting the updated suggestion in the title text, we don't see the aftermath. But we don't see anyone disappearing into the now intangible asteroid, so feasibly they are at least 'mutually tangible' with it. 81.179.200.82 19:38, 4 September 2026 (UTC)

My first thought on reading this one was IDSPISPOPD :D 2a02:a468:b8cb:0:d4b3:6f10:eed6:5307 (talk) 18:16, 4 September 2026 (please sign your comments with ~~~~)

First comment I've seen with an IPv8 address!SomebodyElse (talk) 21:03, 4 September 2026 (UTC)

Please don't tell my ISP, I'm not supposed to use it outside Local Area Networks ;) 2A02:A468:B8CB:0:D4B3:6F10:EED6:5307 01:24, 5 September 2026 (UTC)

'sv_cheats 1' ahh solution Black Hat's Hat (talk) 20:06, 4 September 2026 (UTC)

I like this comic! Got a feel like the 1300 era of XKCD. Yippee Radish ^{[citation needed]} 20:19, 4 September 2026 (UTC)

Do we know if a particular launch vehicle is depicted in panel 1? It looks a bit like SLS, Ariane 6 or LVM3 (formerly GSLV Mk III), (though something is a bit off with each option). Does anyone have any other candidate for which rocket it could be? --Anmhuirmhaorga (talk) 20:45, 4 September 2026 (UTC)

Randall rather likes the "two-booster" rocket-stack design, but I've never been able to tie it down to any particular IRL example, maybe the best bet would be to closely peruse the chine/external-runner and matching it to something in actual use.

The top looks like an Apollo/Orion style of capsule, presumably the lander we later (which has a Blue Moon-like 'lower crew compartment' base, though a more novel upper structure) was contained in the fairing behind the capsule (which has no obvious escape-tower) just like the LEM was in the respective Saturn V stacks. Though whether that means that there's a Command And Service Module (or Orion+'cargo trunk') floating out there in near-asteroid-orbit is another question.

Anyway, this maybe leaves the rest as a 2-stage(+boosters) design to reach orbit, if we can trust the lines/lack of lines in the drawing as depicting the component elements of the whole stack, unless it's only the way to get to the crew to the orbital site of the construction/accumulation of hardware then destined to do the full Deep Impact/Armageddon trip onward.

So very much a bit of a mish-mash, I think. And probably intentionally so. 81.179.200.82 21:36, 4 September 2026 (UTC)

I think that no-clipping yourself is a bad idea. It would create a perfect vacuum where you were. what if? 2 shows that that will collapse, and possibly turn briefly to plasma in the center. If you can see while no-clipping, then energy still interacts with you, and plasma has a lot of energy. All that energy is being dumped into your abdomen. Xkdvd (talk) 21:24, 4 September 2026 (UTC)

I think we’re missing something here. If energy is held constant, then wouldn’t velocity increase as mass reduces? Given the speed of astronomical objects, would we be approaching relativistic territory here if that were the case? 76.216.164.118

I think I just got the same comic in a row twice with the Random Comic button. What are the chances of that happening? Xkdvd (talk) 02:35, 5 September 2026 (UTC)

one in three thousand two hundred ninety-four. 76.180.39.133 19:02, 5 September 2026 (UTC)

Nope! You're forgetting that webpages can also show up. Xkdvd (talk) 00:11, 7 September 2026 (UTC)

Pardon me if while I was setting up my account or figuring out how this works this was already covered, but the terror that would be “pretty funny” if the mass of the asteroid were reduced to harmlessness would also occur with the noclip option. People would see the asteroid approaching, and then, if they’re right under it, it would go right through them. How is this a better experience than a very-low-mass asteroid approaching? Clevername (talk) 11:52, 5 September 2026 (UTC)Clevername

It has enough gravity to *walk around and leave footprints*? That would make the sauropod-killer asteroid look like a pebble in comparison! Even at 500km across walking without launching yourself all over the place would be hard. Setting aside that nothing this large gets anywhere near our orbit, an impact would result in lava oceans and incinerate any trace of life. Making it's mass 1kg would eject it from the solar system at an incredible acceleration, 1g for every km^2 or so, due to radiation pressure. This is what the Three Body got wrong about u folding a proton. 2607:fb90:8e00:df30:a858:41ff:fe1d:4a01 (talk) 21:32, 5 September 2026 (please sign your comments with ~~~~)

Really needed the explanation. All that gameplaying stuff went right over my head.--2A00:23CC:D248:8901:196B:3CA8:BFC0:FF54 08:56, 6 September 2026 (UTC)

Energy calculation:

Mission Control suggests that rather than enabling noclip, the astronauts should instead just reduce the asteroid's mass to 1 kg. If the asteroid is assumed to have a volume of about 1000 km³, this would reduce its density to 10^-15 g/cm³ and its energy to a few kJ.

How do you figure it's "a few kJ"? Speed at impact (of meteorites that have clipping enabled, which is most of them^{[citation needed]}) is 11 km/s or more, and kinetic energy is $\frac{1}{2}m{v}^2$, so an object with a mass of of 1 kg should have at least 61 MJ of energy, i.e., three orders of magnitude more energy than stated. 2A0D:6FC2:6A90:4D00:0:0:0:C3E 04:13, 7 September 2026 (UTC)
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