'm posting here as we have the technology to do this, but perhaps not the will:
My suggestion follows which has details that need to be fixed. We can build a barely interplanetary shuttle at the ISS = international space station. It will compromise some of the science presently done at the ISS. A crew of two female colonists stand by in the ISS for launch on very short notice. When a possibly suitable asteroid or comet is detected approaching Earth, the shuttle leaves the ISS to land on the asteroid a day or two later. Hopefully the asteroid misses Earth. The shuttle has a rocket motor at both ends, so one motor can fuse a hole into the asteroid while the other keeps the shuttle from taking off. Depending on the composition of the asteroid, there will be enough fuel to bore down 3 to 30 meters into the asteroid. The shuttle will plug the opening of the hole. The colonists will caulk to make an air tight seal. Now the colonists can breath about 3 psi of 98% oxygen in the bottom of the hole. More would be better, but they can likely adapt. More pressure may blow the shuttle out of the hole and/or spilt the asteroid, which has almost no gravity and possibly very little cohesion and adhesion. The colony is in trouble, if the asteroid is a gravel pile. They can now enlarge their tiny habitat (which is supplemented by the shuttle that brought them there) Water, oxygen and other materials that may be useful later can be extracted from the asteroid material. A large reserve is desirable as it may be decades before this asteroid does another close approach to Earth. A years supply of food is minimum as it will be practical to produce very little of their own food. Unmanned supply rockets can likely reach the colony anywhere in the inner solar system, but there will always be reasonable doubt about successfully docking with the end of the shuttle sticking out of the hole. Walking the surface of the asteroid in a spacesuit is dangerous, so they will do this as rarely as practical. They may need to band the asteroid to prevent their atmosphere from expanding the asteroid slowly to disintegration. The asteroid may have a small dimension as small as 50 meters. Small asteroids are generally not spherical. 20 meters of most asteroid material does give good radiation protection, but the asteroid material it's self may be dangerously radio active. When and if the ladies decide their colony is reasonably safe, one of them will produce one or more children with the help of the sperm bank or embryo bank that they brought from Earth. The other lady will be the midwife. When the children reach teen age, they will want their own colony, and they can quite easily by retrofitting two of the supply rockets, nose to nose for the short trip to a different asteroid which will approach closely, but rarely. The asteroid dwellers will be able to post in forums like
www.space.com and
www.bautforum.com which will give them a notoriety to partially compensate for the disadvantages. The ideas that flow to Earth may be worth more than the total cost of the program. In a few centuries the human population of the solar system could reach thousands by launching only a few shuttle from the ISS.
The space elevator will be ideal for launching the supply rockets. This shuttle can be up graded to take humans to the moon or Mars as the technology improves. Neil
