Author Topic: Asteroids as habitats  (Read 24703 times)

Offline Andrew_W

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Re: Asteroids as habitats
« Reply #20 on: 01/29/2012 06:56 AM »
You drill down to the center of the asteroid, insert a ~1 km diameter spherical liner and inflate, then you just bring your habitation modules inside the liner, tie them together and rotate.

For a small asteroid the gas pressure inside the liner is going to be well under 1 psi.

You still need the liner, even if the expanded asteroid was self supporting, to keep dust and other debris out of the environment.

you'll probably want to use mirrors and a transparent panel to let sunlight into the habitation volume.
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Offline A_M_Swallow

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Re: Asteroids as habitats
« Reply #21 on: 01/29/2012 07:31 AM »
The 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.


Unless you have 2 trains, preferably 3, the entire tunnel system will move from side to side as the train passes.

Online douglas100

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Re: Asteroids as habitats
« Reply #22 on: 01/29/2012 08:11 AM »
I would avoid rubble piles and go for monolithic asteroids. (This requires some close up survey work, of course.) I'm not convinced the gravity of even a small asteroid would not cause a slow motion cave in of the cavity dug out. I don't think we know enough about this to be sure. Nature has nasty ways of surprising us.
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Offline QuantumG

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Re: Asteroids as habitats
« Reply #23 on: 01/29/2012 11:58 AM »
A "slow motion cave in" eh? Maybe you should rethink that.
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Online douglas100

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Re: Asteroids as habitats
« Reply #24 on: 01/29/2012 12:09 PM »
Please explain.
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Offline revprez

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Re: Asteroids as habitats
« Reply #25 on: 01/29/2012 12:48 PM »
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.

Let's say you can get down to $500/kg lift to LEO.  If in-space transit costs are negligible and you can deorbit for about a thousandth of a percent of that, space-based transport competes with terrestrial (which is on the order of $0.01 per ton-km).  This is first order guesswork, but it does neatly separate the problem of competing origination costs from transport ones.
« Last Edit: 01/29/2012 12:50 PM by revprez »
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Offline Andrew_W

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Re: Asteroids as habitats
« Reply #26 on: 01/29/2012 09:02 PM »
Another approach would be to build a torus shell from blocks of asteroidal material made using solar sintering, a spin your small habitat modules inside the torus shell as it orbits the asteroid while the proper colony is constructed.
« Last Edit: 01/29/2012 09:03 PM by Andrew_W »
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Offline manboy

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Re: Asteroids as habitats
« Reply #27 on: 01/29/2012 09:45 PM »
I always wondered if a centrifuge would unintentionally change the natural rotation of an asteroid.
« Last Edit: 01/29/2012 09:46 PM by manboy »
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Offline ArbitraryConstant

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Re: Asteroids as habitats
« Reply #28 on: 02/12/2012 01:33 AM »
Vast amounts of literature on the subject: http://en.wikipedia.org/wiki/Colonization_of_the_asteroids

Asteroids 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 protection

Spinning 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?

Offline alexterrell

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Re: Asteroids as habitats
« Reply #29 on: 02/13/2012 08:57 PM »
I put something in here, including a sketch
http://forum.nasaspaceflight.com/index.php?topic=18759.msg730853#msg730853

A lot of asteroids are rubble piles with zero tensile strength. You bury an inflatable habitat and then inflate. The habitat can then be primarily assembled on Earth.

As for the train idea, you can extend this into a torus with a very small inner radius (c 5m) so you still have access, and a large enough outer radius (25m) to give useful artificial gravity.

Offline alexterrell

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Re: Asteroids as habitats
« Reply #30 on: 02/13/2012 09:05 PM »

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?

If your using sunlight, filter out the IR first.

If you have some way of transferring liquids in and out, you can remove stale air, clean it, and reintroduce clean chilled air or even liquid air.

Offline neviden

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Re: Asteroids as habitats
« Reply #31 on: 02/14/2012 04:27 PM »
I don't see why it would be impossible to make.

First, you find nice (preferably ruble pile) asteroid that is made of iron. Use magnets to separate iron from the rest of things. Melt the iron with concentrated solar energy. Make a thick iron plate. Weld plates together to form a large tube. Rotate the tube. Fill the tube with air. If you would need protection from radiation, dump few meters of soil on the inside (preferably in some form of concrete). If you need sunlight, use mirrors and windows.

After that you can walk inside of this large space station and do whatever you would do in a large empty building on Earth that has 24/7 light. Nice house, garden, workshop, factory, shop, hospital,...

Offline AlanSE

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Re: Asteroids as habitats
« Reply #32 on: 11/25/2013 07:16 PM »
I've spent some time on related concepts, and I find a lot of strange statements in this thread.

Saying that asteroids are like "gravel" is a helpful analogy, certainly.  However, the talk about cave-ins looks pretty thoroughly incorrect up to this point.  If we assume that asteroids are made of rocks roughly the size of gravel, then yes, digging tunnels will be difficult.

But there's no reason to think this.  Asteroid macroporosity is a fascinating topic.  If you ask how large the pores are, however, we don't really know.  We still have good theoretical arguments in different directions.  As instructive example are binaries that were tidally locked, and then got close enough to make contact - what I think of as "kissing" asteroids.  This formation is probably very common, and it's not unexpected.

As we categorize more and more asteroids, we find a huge fraction are highly irregular.  These have ratios of length to width of 2-to-1 or so very frequently.  It's about as likely to find a highly irregular asteroid as it is to find a regular one, unless you look at the huge ones like Vesta or Ceres.

A collapsed binary pair is important for two reasons:

 - it gives a lower limit on the rock strength (due to resistance against its own gravity)
 - it tells us how fragments might have clumped together

In other words, the fact that we have lots of highly irregular and lots of binary asteroids gives us a picture of their evolution, where they're kind of two sides of the same coin.  That's important, because it indicates that larger bodies are likely made of parts roughly the size other asteroids.  Or at least some of its parts will be that size, and the entire rubble pile might be made of a continuous distribution of sizes.  For the technically inclined, I will note that the majority of the mass of the asteroid belt is contained in larger bodies.  There are more smaller bodies, but there is more mass from larger bodies.  So if you clumped together random bodies from the asteroid belt into a rubble pile, large fragments would dominate, QED.

What I'm trying to say is that there may be no tunnel to build.  In other words, you can float through the spaces between the rubble straight to the center of the body.  There are no concerns about cave-ins, because these caves have been there for millions or billions of years.  At some locations in it, I don't doubt we will find gravel-like rubble, but nature is much more messy than to make the entire thing out of this.

Talk about the "liner" is meaningful, however.  If there are spaces in-between the rocks that allowed you access to the center, then obviously you have to close off those spaces to hold any kind of gas inside.  You probably don't have to worry about the gas permeating large monoliths, but they could be fractured anyway.  That's what you'd cover with a liner.  I've recently been arguing that this makes sense to hold air, and there are almost certainly km-scale cavities where this would work:

http://gravitationalballoon.blogspot.com/2013/11/why-not-live-in-empty-spaces-inside.html

QuantumG made some good points, but regarding artificial gravity, I don't think it needs to be that complicated.  If you've sealed off a pressure boundary then you can put a rotating structure inside that boundary.  There's some human limit of tolerance for Coriolis forces, so you'd prefer to make them large, but you're limited by air resistance.  But that can be engineered around.

Offline cordwainer

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Re: Asteroids as habitats
« Reply #33 on: 11/26/2013 06:19 AM »
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. Then slowly build a ring or torus between the towers to create a larger habitat. Though I like Larry Nivens idea of inflating an iron-nickel asteroid into a hollow ball, I don't think it would be very practical or easy to engineer such a feat.

Offline AlanSE

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Re: Asteroids as habitats
« Reply #34 on: 11/26/2013 12:24 PM »
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.

The structural needs scale with the radius of the circle that you travel in artificial gravity rotation.  In other words, you picked about the worst possible point available.  Now, maybe you thought that starting from GEO gives some kind of benefit.  I wondered the same thing, and I assure you, it doesn't.  Having a gravitational body in the middle of a tethered rotating system doesn't help.  It makes the material needs more, not less, because the material constraints still scale with radius, because that is purely geometric, because the acceleration is a set constraint to be Earth gravity (or close to it).  You could claim that the scheme reduces Coriolis forces.  This is because it spins with a slower speed than without the asteroid in the center.  But the asteroid's gravity is small to begin with compared to Earth gravity.

Not only do the structural needs balloon, but you trashed all the radiation shielding benefits from the asteroid.  It's true that you get rotation from the spin of the asteroid itself, and these commonly have day-lengths of 4 to 8 hours.  An asteroid's rotation can certainly be used as a catapult or to impart angular momentum to other things.  But rotating a space station is not the hard part.  You can do that with a simple electric motor, a wheel, and some tensioners.  I can't identify a problem that your proposal solves.

Long Term Living in low G environment
« Reply #35 on: 01/03/2015 08:53 AM »
Long Term Living in low G environment
So here's My Idea. I've never heard of anyone else suggesting it so maybe I'm the first?

  As for long term living in a low g environment like an asteroid, space station or moon: You need 1 G gravity to stay healthy and have children. So, we don't need a train going round in circles, because, lets be honest here, that's Really impractical. Especially for a space station or any colony of significant size. It also makes a free floating wholly artificial space station much more expensive to spin the whole thing up (LOTS more reinforcement needed) than it would if only the residences and workplaces were individually spun for gravity.
  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.
  This way, the only time you would actually experience micro or low gravity would be going to and from your home and the office or where ever else you were going. You would live, work and sleep (1/3 of our lives) in a 1 gravity environment. It's a LOT cheaper and faster to build, and a WHOLE lot safer than spinning up a large structure like an entire space station or asteroid.
  A spinning space station has the extremely difficult problem of not becoming unbalanced and literally tearing itself apart. Think about what happens when a spinning top becomes unbalanced and starts jumping all over the table.
  This probably wont be needed on Mars, but may be needed on Earths Moon if Lunar gravity is not enough to keep humans healthy or able to have children.
  It would certainly make it easier to do something like start using the international space station as a starting point and just keep adding modules for work, manufacturing and living spaces, As opposed to the Massively, Staggeringly large amounts of money needed to build something like a Stanford torus that cant be used until it is completed. Adding/creating 1 g living/working spaces one at a time, as needed, is much cheaper, safer and more practical than a single mono-structural station that would require Huge budget approval by the ever changing, multiple administrations and congresses.
  Any one of which could kill the whole project at any time during the years and possibly decades it would take to build one.
  My way, it grows as needed and as we can get the funding for it on a case by case basis. By making it cheaper, it brings space habitats into the range of private corporations and individuals.
I hope someone who is involved in these sorts of things considers my ideas.
Cheers!
« Last Edit: 01/03/2015 08:55 AM by DavidEarlAgoura »

Online zodiacchris

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Re: Asteroids as habitats
« Reply #36 on: 01/03/2015 10:19 AM »
Hi David,
Welcome to the forum with you first interesting post. Without going into too much detail, just two things to ponder regarding your concept of small, house sized individual spun habitats.
-I would recommend you read up on Coriolis force and the associated side effects in small structures. If to small, you'll have a very miserable time in your small habitat and your inner ear will not be impressed...
-We don't know if we need 1g to live and procreate, we might well be okay in 0.5 or 0.3 g, like we have on Mars.

Cheers,
Chris

Re: Asteroids as habitats
« Reply #37 on: 01/03/2015 10:23 AM »
So here's my ideas on living IN an asteroid.
  The last thing we want to do is damage the structural integrity of the asteroid by melting it. and we wouldn't need a liner, or at least not a very thick or expensive one.

  If we used a large, nickel/iron or crystal iron asteroid, one that was probably part of a planet that got smashed up during the early days of the solar system when the inner solar system was something like a demolition derby and there were a LOT more planets/planetoids/dwarf planets than there are now.

Every time someone finds a nickel iron or crystal iron meteorite, their holding what used to be a part of the crystal iron core at the center of a planet that got smashed apart soon after the birth of the solar system.
 The benefits to using a solid crystal iron asteroid is that since it formed under the intense heat and pressure at the center of a planet, it's likely to be one giant iron crystal, and VERY strong and NOT porous.
We could choose a large asteroid, miles or even tens of miles (hundreds of miles?) wide and long, and then, using giant solar mirrors spun for rigidity, focus sunlight on the asteroid and ablate the surface until it is cylinder shaped with dimensions something like a can of soda.
  Then, still using the mirrors, core it out, down its horizontal center. If the asteroid was, say, 50 miles wide and 100 miles long, and the cored hollow section was 5 miles wide, that would leave 22 and 1/2 miles of solid iron crystal on all sides to protect the interior settlement from small ( and even large) asteroids and radiation.
And if we left, say, 5 miles of iron on each end as a buffer between the inside habitat and the asteroids and radiation of the outside universe, that would leave us with a living space with a radius of  15.7 miles and Ninety Miles Long. Thatís an interior living space of more than FOURTEEN HUNDRED SQUARE MILES! Comparatively, the city of Los Angeles with a population of 3.8 million people,  is only 469 square miles.
Thatís enough room for a LOT of people.
Once cored, the mirrors could be used to ablate/etch a varied landscape (hills, rivers, lakes, etc) on the interior. Then, a layer of carbon, easily obtainable from comets and carbonaceous chondrite asteroids, refined using focused sunlight from mirrors, could be put down on the inner surface to insulate the habitat against the cold of the interior of the asteroid.
  Once cored, landscaped and insulated, and with one end left open, large chunks of stony asteroids already carved/landscaped themselves (by the mirrors again) could be maneuvered in and attached to the interior,  with some ground up to make soil for plants to grow in (plants LOVE ground up stony meteorites).  Comets, which are rich in organic molecules and would help build living soil, could be brought in for air and water.
  Once everything is in place, the end chunk of the section that was removed from the core could be cut off and put back as a plug and (using mirrors again) welded back into place to seal the interior.
  Then, the asteroid could be spun up so the interior surface of the habitat would have 1 G. Various methods could be used to spin it up.  Perhaps using mirrors again, to drill holes at an angle into the asteroid. As the iron is vaporized it would expand outward and act like a rockets exhaust and spin up the asteroid.
Fixed onto the outside of the asteroid,  mirrors with lenses that connect to fiber-optic lines routed into the interior, could be used to gather sunlight and transfer it to the habitat providing light and heat. And a look at the outside world.
The same process could be used with the core that was removed to make a smaller version, and perhaps even one more from that ones core to make an even smaller version of it.
  I sincerely hope I live long enough to witness something like this happen.

Best!

Offline momerathe

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Re: Asteroids as habitats
« Reply #38 on: 01/03/2015 11:24 AM »
Depending how far in the future we're talking, it may be easier for us to adjust ourselves the the habitat, than the habitat to ourselves; to genetically engineer traits for radiation protection and zero-g living.
thermodynamics will get you in the end

Online Nilof

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Re: Asteroids as habitats
« Reply #39 on: 01/03/2015 11:45 AM »
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.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.