Suppose there is a comet of radius 500m made of mostly ice, with the rest being rock, dust, and other frozen gases. The comet is being hollowed out in order to use the water as reaction mass (giving it a few miligees of acceleration). How could the comet be strengthened such that it does not collapse onto itself/from the forces of acceleration? This should preferably be done with materials on the comet itself.

  • $\begingroup$ That's out of pure curiosity : Why do you take out what is inside the comet instead of nibbling the outside slowly? $\endgroup$
    – Tortliena
    Nov 9 at 15:03
  • $\begingroup$ Comets are largely already brittle enough without any hollowing to break up in case of sudden acceleration. But in this case I say compress it with a squeezer, anyway you don't need to retain its form. $\endgroup$
    – Vesper
    Nov 9 at 15:14
  • $\begingroup$ You're using the comet's mass to move the comet and want to preserve what's left? I very rarely ask about the backstory of a question as, 99% of the time, it shouldn't matter, but what's the point of doing this? Every pass around a sun (I'm assuming we're talking about comets orbiting suns... could be wrong about that...) diminishes the comet and, eventually, it is destroyed anyway. If the comet's being moved to protect (e.g.) a planet, why bother preserving it? This Q feels an awful lot like it's not the real problem and there's a better way to deal with the real problem. $\endgroup$
    – JBH
    Nov 9 at 17:55
  • $\begingroup$ Maybe they want to use it as a weapon, or for terraforming, or to deflect a bigger comet, or... $\endgroup$
    – K. Morgan
    Nov 14 at 10:42

2 Answers 2

  • Thaw and re-freeze in more uniform, solid building blocks. Water ice on the outside to increase albedo, gases and gravel on the inside.
  • Bag it in a big plastic sheet. Carbon dust and soot plus hydrogen from water are the raw material for polyethylenes (or polystyrenes).
  • If you can manufacture them, ropes of carbon nanotubes both as nets around the surface and as anchors inside.
  • $\begingroup$ Thawing a comet would cause resultant water to sublime away in all directions, losing you available mass. Gases would just vent away as well. $\endgroup$
    – Vesper
    Nov 9 at 15:16
  • 2
    $\begingroup$ @Vesper That's why the first thing you manufacture is a plastic bag which you put around the comet. All further industry is done inside. $\endgroup$ Nov 9 at 15:39
  • $\begingroup$ @TheDyingOfLight, my idea was to shovel the slush into the oven/separator. Some clever contraption with heat exchangers so that one stage of cooling is the pre-heater for a previous stage. $\endgroup$
    – o.m.
    Nov 9 at 16:58

Ice at the temperatures at the edge of the solar system is hard enough although a bit brittle. If you blow the gases generated in the centre through a long pipe to reduce the contact with the outer surface the external shell should remain strong enough. The pipe would be also useful to bypass the gravity of the comet itself and prevent the ejecta from falling back. If the wall remain thick enough it would act as a thermal insulator keeping the outer layer cold and strong. Furthermore the small pressure would let the water sublimate immediately keeping no liquid water with latent heat around.

The only problem is that you don't have just ice, but a mix of ice and rocks. You would have to find a way to blow away also some rocks.


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