Quote from: A_M_Swallow on 01/29/2012 06:18 amThe tunnel and asteroid will also have to take the force of the train passing.Not really. "Train" is an analogy.. we're talking about a ring of steel with a carriage rolling around the inside. The track is transported in parts and put together. It would work fine on the way to the asteroid too, but I think there's more value in a fast transit in zero-g to get to the asteroid than artificial gravity in transit because you can send the track and the train on a slow electric propulsion cargo flight, reducing the mass required on the high impulse crew flight. There's a tradeoff.
The tunnel and asteroid will also have to take the force of the train passing.
Taking the long view, there will always be something that it's better to get from Earth than it is to produce locally.. so what can asteroid colonists produce better than people on Earth? Nothing, right? I disagree. They can make stuff in space. So long as launch from Earth remains costly, and people on Earth remain interested in manufactured items in space, those colonists already in space will always have valuable goods.Maybe that's not so clear. So here's an example: spoons. Even today, people use spoons in space. Sometime in the future there's a need for 1 kg of spoons in Earth orbit. We could launch it from Earth and pay, let's say, $500/kg in launch costs (what an amazing achievement!) or we can put it on the slow boat from the asteroid colony. It's not hard to imagine the marginal cost of transporting those spoons from an asteroid colony to Earth being a lot cheaper, because the energy requirements are so much lower.
Vast amounts of literature on the subject: http://en.wikipedia.org/wiki/Colonization_of_the_asteroidsAsteroids provide two advantages over colonizing "free space" such as the Lagrange points: * Materials to build that don't need to be sourced from elsewhere * Radiation protectionSpinning the asteroid has been the traditional way to obtain artificial gravity. More recently a number of people have recognized that spinning a structure inside a hollowed out cavity of the asteroid is a lot easier and maintains the low gravity environment of the asteroid on the surface, which has manufacturing advantages.I wrote about one of the simplest ways to generate artificial gravity - a train track inside an asteroid back in July 2010, http://quantumg.blogspot.com/2010/07/living-inside-asteroid.html
I've often thought along these lines - the main challenge I've thought of is heat rejection from inside the asteroid. Reflecting sunlight in without empty space around to radiate the heat will warm up pretty quickly, won't it?
The easiest way might be to find a fast spinning asteroid and build conning towers along its axis of spin to provide artificial gravity environments.