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
Quote from: QuantumG on 01/28/2012 11:14 PMI 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.htmlWhat happens when the train breaks down?
What happens when the train breaks down?
Yes - This is exactly how most sci-fy goes, jumping straight to what has been made and how it is used, totally ignoring the challange or impossibility of making it in the first place. I was hoping for this thread to focus on how the hollow asteroid became a hollow asteroid, not so much on how it was used after it became hollow. Might it be feasible to guide two modest sized asteroids, each with a similar size crater together so that one crater capped the other and the weak gravity held them together? If not, how much super glue is needed? Would one cratered asteroid, capped with a moderately flat asteroid be a suitable start to a habitat? How about a larger asteroid with a crater capped by a small nickel-iron asteroid that had been heated and spun into a disk?
Gah! What do you imagine these things are made out of?Consider 25143 Itokawa, visited by Hayabusa. It has a mean density of 1.95 g/cm^3. This is about the same as the density of natural gravel.. which makes perfect sense when you look at it.You don't need nuclear bombs to dig a hole in this stuff.
Quote from: QuantumG on 01/29/2012 03:23 AMGah! What do you imagine these things are made out of?Consider 25143 Itokawa, visited by Hayabusa. It has a mean density of 1.95 g/cm^3. This is about the same as the density of natural gravel.. which makes perfect sense when you look at it.You don't need nuclear bombs to dig a hole in this stuff.If they're like gravel, how will the tunnels hold together after you've tunneled through them?
Agreed a Tunnel Boring Machine is a far more practical approach. But AERO wants to hollow the entire asteroid and possibly reshape it and spin it in the processes. When you consider the amount of material you need to move to complete his vision - nuclear may be the way to go.
If they're like gravel, how will the tunnels hold together after you've tunneled through them?
If you wanted to pressurize (with air) the tunnels you'd need a liner.
The tunnel and asteroid will also have to take the force of the train passing.
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.
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.
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.
because a tunnel-boring machine for a 1-km wide hole would probably have a mass of 10^6 tons by order of magnitude.
I wrote about one of the simplest ways to generate artificial gravity - a train track inside an asteroid