Saturday, June 18, 2011

Blowing up asteroids

When we've gotten ourselves established in space throughout the Earth-Moon system the next place I'd like to see us target for exploitation are the Near Earth Objects (NEO's), asteroids that orbit the sun at about the same distance that the Earth does.

Because they're close, and because of their small size and low gravity, these objects hold the promise of resources within relatively easy reach, resources that even if not richer than those of the Moon, will in many respects be different to those offered by the Moon, and different and richer can mean the same thing.

Lets imaging our prospectors arriving at what they hope will be a gold mine of rich rare earth elements, water and other volatiles, heavy metals and whatever else that has a market value. Question: how to use the asteroid to shelter yourselves from the radiation of space, How to find out what's inside, and how to get out any resources that are there?

Here's an idea that I haven't come across than might solve all three problems at once - blow it up! No, not with explosives.

Small asteroids are not held together too well gravitationally, if they're loose rubble piles even kilometers inside them, even at their core, the pressure from the weight of material will be very small, so in principle it would be possible to drill a single hole, shove a balloon down it, blow air in, and spread the entire mass of the asteroid out over the balloons inflated surface. Then you move inside, hell, move the whole family inside!

OK, you still want solar reflectors to warm the interior, and you'll probably want more than just the balloon used to inflate the asteroid for accommodation.

If we take an asteroid that's a Kilometer in diameter, and inflate a balloon that's a kilometer in diameter inside it, if the material of the asteroid were spread out evenly, it would form a layer about 125 meters thick.

1 comment:

  1. I'm writing this comment as a (now) heavily biased observer, since this is basically what my own blog is about.

    In principle, everything about your idea is fine. But the only benefit it buys you is radiation shielding, and there are several complications with practically doing it that haven't been addressed. It's certainly a matter of dispute whether the benefit of (nearly) perfect radiation shielding of 125 meters is a worthwhile prize for dealing with all those complications. But of course, this is what you get by limiting the discussion to near-Earth objects. There are several km-scale objects at our distance from the sun, but they are both highly inclined from the solar system's plane and highly elliptic - making the delta V cost of reaching them extremely prohibitive. We're left with an ideal NEA population of bodies that are roughly 100 meters or so, as you postulate. Exactly what these are made of is still an interesting field of research, but certainly a large fraction are the common C-type things, which are easily cut but probably cohesive to some significant degree.

    That cohesiveness is a problem when you try to inflate that balloon in extremeeeemly low microgravity fields. The material will prefer to stay solid, and only offer you some large fracture lines. You'll cut the object in half as opposed to rearranging it. The picture you paint is consistent with an asteroid made of sand, but those don't really exist. There are several dangers of managing the fracturing of the body, and it's possible you'll employ a system of explosives or something like that in order to have it move like you want. If not careful, the balloon could shake off the large chunks of asteroid in some region of the sphere, and expose itself to space. That will then exceed the strength of the balloon and you'll have to try again at great cost.