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Comment by gamegoblin | Hacker News Reader

Something that is sometimes pointed out about holes in spacecraft is that you don't lose air as fast as movies would imply. After all, the pressure difference between inside and outside is only 1 atmosphere.

For instance, if a micro-meteor created a bullet-sized hole in the International Space Station, it would take 5-10 minutes for the air pressure to drop to 0.5 atmospheres. The kilometers-scale space colonies described here would take much longer. More than enough time for some drone to patch it, or for the inhabitants to get to "life boats" or some sort of shelter.

I think the important part, then, would be to design the shell such that damage in one part can't spread too far.

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Exactly - these thing as designed by ONeil are HUGE - 30 km long on the "default" island three type.

The solid walls would be meters thick, so the projectile would have to be very masive and/or very fast. And even then it would take a long time for pressure to reach dangerously low levels.

I would expect lots of double and triple hulls. Especially on the glassy parts. Micrometorite smashes through a pane and it only opens up the compartmentalized space between the walls. It doesn't even depressurize anything because the secondary hull can be left unpressurized. These can then be repaired by technicians.

A big emergency plug can be designed for large impacts, and as a last resort everybody can be trained in the use of emergency depressurization shelters. It's not without its risks, but at the same time it's not like the Earth is totally safe either. O'Neill colonies don't have to worry about natural disasters.

There are already proposals for resin-filled self-healing polymers and epoxies. This would provide a high amount of resilience to small impacts.

I've seen a clever concept with special has filled baloons covered with a sticky resin layer from the inside.

If there is a hull breach the baloons are automatically released, get sucked into the hole, break apart and seal it with the resin.

You cold definitely do a Whipple shield - basically a stand-of plate that vaporizws and fractures any projectiles, making it impact the next plate/hull on much bigger area but with much less localized force. This is basically the main defense ISS has agains micro meteorites and orbital debris.

On the ISS, they plugged a hole with a finger + tape: https://www.telegraph.co.uk/science/2018/08/30/international...

And that was a manufacturing defect, not a meteorite impact.

Not very vulnerable to small random space debris, but a terrorist explosive would be a different matter.

I can't see habitats like this existing except in the presence of an extremely peaceful and unstrained humanity-wide society.

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