"Erik Max Francis" wrote in message
t...
Troy wrote:

The concept I was thinking of is Niven's asteroid balloon. Take an
iron asteroid, place water tanks at the centre, spin asteroid on its
axis and bathe with concentrated sunlight from a solar mirror. Tank
explodes, inflates molten steel asteroid into a large habitat. Most
asteroids are just soft rubble piles anyway; they'd fly apart if you
spun them any faster than once every 2 hours. Some sort of melting has
to be done on the outer shell to stop one disintegrating;
additionally, internal structural bracing such as steel cables are
required to hold it together, especially if you want nice amenities
like dirt and artificial gravity.

This has always struck me as implausible. It's hard to see how most, or
even a few, nickel-iron asteroids would be uniform enough to make this
work without just fracturing during the process, wrecking the whole
enterprise.

There is another way to do an asteroid balloon that doesn't require the
asteroid to be anywhere near uniform, nor for you to drill into it (although
doing so would probably help).
Put a balloon (mylar, perhaps) around the asteroid, and fill it with carbon
monoxide. Get it warm and circulating. Then heat the balloon surface to
deposit nickel and iron from carbonyl vapor.

-l.
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