How to Colonize an Asteroid
Once the main shaft is cut all the way across what will one day be the entire axis of the interior sphere, we can begin to expand the shaft into the shape of a sphere.
We can approach this expansion in a number of different ways;
1. Start with shafts out along the equator, quartering the interior space. Work can progress, in different stages, on all four sections at the same time.
2. Simply expand the shaft into the shape of a sphere.
3. Start at one of the poles and begin cutting at the surface edge of the interior sphere
There are more methods too. The final decision might have to wait until we can analyze the interior structure of the asteroid. We might have to work around existing fractures (or use them to our advantage), or we might come across some really difficult material which we might decide to leave as "mountains". Interior terrain will have to be considered far in advance, and its effect on future rotational balance will have to be simulated on computer models. Once we get that much mass rotating, it will be mighty hard to fix a "wobble".