KnowLimits

On the topic of crazy ISS expansion, do you have any thoughts on moving an asteroid to ISS (or more likely a newer space station), or any of the other crazy stuff that happened in the book Seveneves?

Personally I always figured moving a big chunk of metal into LEO would be politically infeasible, if nothing else - but once you got it there, it would certainly be cheaper to study or use.

Depends on state law, stupidly enough.

If all those things fail, could the ISS itself be moved to intercept the wayward astronaut?

It's all just a big numerical simulation. Essentially, for every interacting body, compute the force (due to all the other bodies at their current positions). Then, you choose a time step, compute the new velocity (old velocity + force/mass * timestep), and compute the new position (old position + velocity * timestep). Just do that a few bazillion times. And it's already been done and pre-computed for the planets, so for an asteroid so small that it won't significantly affect planets, you only have to do all that math on the asteroid itself.

Wait, so just for marketing purposes?