I'm not convinced that we will be digging ourselves into asteroids. It gives some extra shielding potential, but it really makes artificial gravity a PITA, and frequent activity around an asteroid that you can dig down into will create a very dirty environment with asteroid dirt flying around everywhere.My general opinion is that one is better off avoiding schemes like this and just use the asteroid for resources. For early habitats, bring inflatable habitats from Earth, surround them with properly sealed bags of gravel from the asteroid for shielding, and use a tether and counterweight system for artificial gravity in free space near the asteroid. The marginal benefit of digging yourself down early just does not outweigh the benefits of a pristine vacuum, easy access to sunlight, and the ability to plan ahead easily.By digging yourself into an asteroid, you can run into unexpected problems, such as metallic dust from the asteroid cold welding itself into critical parts, sharp-grained dust getting on your solar panels and inside your habitats, unpredictable thermal changes, ect ect. I expect free space habitats with asteroid material as shielding is likely to become the superior option much like buildings above ground are generally both cheaper and more practical than buildings below ground on Earth.
All we need to do is build peoples homes/workplaces/wherever in the shape of a toroid (donut) shape and put a spin on them so it creates a pull of 1 gravity inside. Surround the building with several concentric circles of metal or another sturdy material and float them on magnets. Put them at an ever increasing angle and speed, towards the house, and the resident can match speeds with the house or his/her workplace by simply stepping from one to the next till they get to the innermost ring that has a matching speed to their home/office/wherever. It would be like walking up or down steps.
I think what it comes down to is the size of the cavity inside the asteroid. If you're tempted to rotate your habitat mere meters away then it will have the same failure mode as Lewis One - crashing into the shielding - but I think that temptation is driven by a lack of shielding material. If you have an abundance of material, which obviously is the goal of co-locating your habitat with an asteroid, then a static shield with some stand-off distance is more desirable than packing the shielding into the hull as your habitat doesn't have to carry all that weight, you don't have to expend power spinning it up, etc.
...Shielding is fairly easy. Grind up regolith/rocks to gravel and put it into sacks.
Apart from a few asteroids whose densities have been investigated, one has to resort to enlightened guesswork. See Carry for a summary.For many asteroids a value of ρ~2 g/cm3 has been assumed.However, density depends on the asteroid's spectral type. Krasinsky et al. gives calculations for the mean densities of C, S, and M class asteroids as 1.38, 2.71, and 5.32 g/cm3. (Here "C" included Tholen classes C, D, P, T, B, G, and F, while "S" included Tholen classes S, K, Q, V, R, A, and E). Assuming these values (rather than the present ~2 g/cm3) is a better guess. - source
Actually, an O'neil tube or Stanford Torus built inside of an asteroid makes a considerable amount of senseso long as you line the cavity with a structure that can handle shifting masses. If you physically attach the Torus or O'Neil Tube to the inside of the asteroid, regardless of how effecient the coupling joint is, some precession will occure with the asteroid itself.If we're talking a rubble pile asteroid, unless the precession rate creates a centripedal force greater tyhan the Asteroid's gravity, then it should gradually reshape that part of itself that the rotating structure is in, to conform to the protective structure around the rotational mass. The same is true of any mass beyond the location of the rotating mass. mass will be lost by a spin higher than the forces holding the asteroid together, or will migrate to the centerline of the spin.
The observed fact that light changes of the asteroids exhibit no beat periods is interpreted as an indication that they do not wobble in space like spinning tops, but spin about only one axis (possibly — but not necessarily — inclined but little to the plane of their orbits). Since, moreover, the damping of three-dimensional rotation by jovi-solar attraction would require a time which is long in comparison with the age of the solar system, it is concluded that the present uni-axial rotation must represent a property preserved from the time when the asteroids were formed.
I have a question regarding using rotation for gravity. Would it not only work for things in contact with the floor?I wonder if you jumped would you come down or would you just sail up to the ceiling. Or if you were to throw something up what would happen. If you were in a hollowed out asteroid and tossed up a baseball I am thinking the ball would end up on the other side of the asteroid.
I have a question regarding using rotation for gravity. Would it not only work for things in contact with the floor? I wonder if you jumped would you come down or would you just sail up to the ceiling. Or if you were to throw something up what would happen. If you were in a hollowed out asteroid and tossed up a baseball I am thinking the ball would end up on the other side of the asteroid.