Details On Inflatable Space Modules

Decibel writes "Although it's been mentioned on Slashdot twice now, this article contains more details about Robert T. Bigelow's plan to orbit massive inflatable space habitats, with the first test modules to be launched next year. It also details the $50 million "America's Space Prize", with the objective to "spur development of a low-cost commercial manned orbital vehicle capable of launching 5-7 astronauts at a time to Bigelow inflatable modules by the end of the decade.""

Xanadu

It's kind of cool to see this idea come to fruition. I'm sure that every child has gone through one of those inflatable castles and wondered what it would be like to have an inflatable house. I myself have often wondered if houses on other planets could be constructed in a manner similar to the late Xanadu [blogs.com]. Just inflate the basic structure with just high enough PSI to make it rigid, then spray foam all over it. Allow the structure to cure, and you've got yourself air-tight, super-strong walls that can be repaired from pretty much any damage just by spraying more foam!

Something to think about, anyway.

Re:Xanadu

There's this [zdomes.com], too. The guy does pretty much what you describe but adds some kind of metal infrastructure as well. The structure of this type that was up in the panhandle of Florida through a hurricane fared remarkably well. [csmonitor.com]

BTW...

...the exact opposite of an inflatable space station, is a skin tight space-suit [wikipedia.org]! If we could develop that technology, space walks could become as easy as diving! (If not a smidge easier.)

Re:Xanadu

Allow the structure to cure, and you've got yourself air-tight, super-strong walls that can be repaired from pretty much any damage just by spraying more foam!

You can start to get respect for these inflatable structures when you realise that normal atmospheric pressure is just about 10 *tonnes* per square meter.

These structures seem to be made from a woven kevlar material.

They also have to be able to survive impact from debris in LEO and micrometeors without simply popping.

Damn...

I'd love to see the "Trojan Condom" logo on that thing. Talk about great product placement.

Fools!

Inflatable space modules are all well and good--until The Terrorists(tm) develop a gigantic space pin!

Re:Fools!

US officials believe terrorist WMD programs have already developed a more advanced version of the gigantic space pin, called the gigantic space needle and that it is hidden in a giantic haystack somewhere in Iraq.

Re:Fools!

terrorist WMD programs have already developed a more advanced version of the gigantic space pin, called the gigantic space needle

Oh No, they already got it into Seattle!! We're all doomed!! [spaceneedle.com]

No terrorists needed

All it will take is "Someone Like Larry." They will have to put up signs everywhere: "No playing darts in inflatable space habitat" "Soccer cleats will be confiscated" "DO NOT RUN WITH SCISSORS"

The biggest challenge

I would love to see someone take on the biggest challenge, articulated nicely here in the article:

The new contest also presents challenges far greater than the X Prize by requiring development of a vehicle that could maneuver to dock at well over 100 mi. altitude and survive a 17,500-mph. reentry.

The big problem, in addition to getting enough thrust to get up to that speed (and into a stable orbit), is how to get down! Ever climb a tree so high that you couldn't figure out how to get down? The analogy is much worse in outer space. The whole idea is, you have an atmosphere that you'll be blasting through at that speed, 17,500 mph or so, and you need some way to decelerate and deal with the heat... good luck to those going ahead with this...

Re:The biggest challenge

We discussed a possible solution [slashdot.org] just a few days ago. The only thing I didn't mention is that the Falcon V would be a good alternative choice for launch vehicle. Especially given how much Boeings prices tend to fluctuate upward for newcomers.

Re:The biggest challenge

Did you read my response [slashdot.org]? A Big Gemini capsule could easily meet the requirements. Especially on the reentry part. All that's needed is a classic epoxy/silicon heat shield, then the parawing for landing. On the ground the heat shield would be peeled off and replaced, the parawing repacked, and the capsule would be ready for relaunch.

Re:The biggest challenge

Now, why can't you use thrusters to decelerate to 0mph and then just get 'pulled in' by gravity?

Well, what are you going to be pushing out of those thrusters? The really basic problem with space travel is that we like to think of it like terrestrial travel: we want to be able to make big changes in velocity over short periods of time. The problem is that in space, there's not a lot of stuff to grab onto and throw around. About the only thing you've got lots of is light, but photons aren't very massive, so solar sails take a long time to effect a large delta-vee.

So, there's not a lot of stuff lying around. So, bring some with you! Except, for each ton of stuff you bring up the gravity well, you have to throw away several tons in the process (check out the relative size of the space shuttle and the liquid fuel tank and solid rocket boosters it uses to get up into orbit). Those extra tons of propellant translate directly into dollars, and that's what makes it expensive to get up there and then come back.

This is why people are constantly looking for a way to get stuff up into LEO without burning up lots and lots of propellant. Space elevators, balloons, high-altitude airplane launches...

Physical Concerns?

Can anybody explain what, if any, physical concerns exist with the use of an inflatable bladder in space? I can't quite envision how an inflatable object would behave in zero-G (perhaps just like any other object?), but in a vacuum, presumably explosion would be quite a difficult problem. Obviously, they've thought this through, but if somebody could explain the challenge of the proposition, I'd love to hear it.

I only know enough about this to know that I don't know enough about it.

-Waldo Jaquith

Re:Physical Concerns?

If (big if) you inflate to sea level air pressure you need to contain 15 psi. Not a big deal. A bike tire can take up to 100 psi, a plastic 2l coke bottle can take over 150 psi. Make the habitat B I G and it will hold a lot of air. If something pops a hole in it, it will take a long time (many minutes) to deflate. Somebody will have to put down their beer, float over to the hole and slap on a peel-n-stick patch.

Re:Physical Concerns?

The only reason why a balloon goes bang when you pop it with a pin is because the rubber rips and the air is violently released. If you put a piece of scotch tape over an inflated balloon and insert a pin you'll see that the balloon didn't pop but there's a hole. The tape reinforced the balloon and kept the rubber from tearing apart.
These inflatable habitats would simply leak air. There wouldn't be any Hollywood gratifying explosions.

These are not fragile

With all the needle jokes and condom comparisons one could get the impression that these inflatable modules are less rugged than the aluminium modules now used for the ISS.

This is not the case. They are made out of multiple layers of kevlar (the same stuff that bulletproof vests are made of). In tests with the NASA-designed transhab inflatable module they have proven to be much more resistant to space debris than aluminium hulls.

Also even if a particulary large piece of space debris should punch a hole in one of these modules, they are so big that there would be plenty of time to evacuate them before the pressure drops too much. A long-time station will probably also have a repair kit on board.

Third, the problem of space debris is particulary severe in low earth orbit. But in a higher earth orbit there is much less space debris, and the stuff that is there moves with much lower relative velocities. So from a space debris point of view low earth orbit is the absolute worst case. A station at an Earth/Moon lagrange point or in deep space would need little or no space debris protection.

Re:These are not fragile

Wrong. Here are two examples:

http://liftoff.msfc.nasa.gov/academy/rocket_sci/ or bmech/vel_calc.html

http://www.solarsystem.org.uk/datatext.html

Baloonish

I just can't picture one of these space balloons without thinking about one end coming loose, and the whole thing blasting crazily about in space while making a ridiculously load farting noise.

Not just for space stations

This could also be used for interplanetary craft.

Imagine launching to Mars. Even if you launch in a tuna can ala Zubrin, it's still pretty confined. If you launch in an un -nflated balloon, accelerate and get pointed at Mars, you can inflate and have twice or three times the living space. As long are you're willing to be confined for a few hours at first, the place could be quite roomy and more people could be sent per trip as long as provisions are increased.

Just a thought.

Nuclear Rockets!

Check out this fascinating detailed design [nuclearspace.com] for a completely reusable Saturn-V size rocket, powered by a Gas Core Nuclear Reactor engine. The engine emits non-radioactive hydrogen propellant. The rocket described would be able to lift 1000 tons of cargo into orbit and return to a powered landing, for only 5% of today's cost per pound.

I know "nuclear" is still a dirty word, but the gas core reactor design is a completely different approach than a big pile of plutonium. Very promising in terms of power, safety and cost.

It's a long article, 14 parts, but well worth reading. Skip the first 5 or 6 sections if you just want to know how the thing works.

Re:Space Junk

You are thinking that the walls will be like a rubber ballon.

The walls will be thick enough to provide the same level of orbital debris protection as existing space station modules. Remember, the Atlas booster had aluminum ballon fuel tanks -- it would actually collapse if the tanks were empty. When other engineers were suggesting it would never fly, they presurized it and gave them a sledgehammer to try to break the booster.

It rebounded and almost hurt the engineer swinging the hammer.

The instant-fill holes are harder than you'd think. Instant-fill tire stuff is designed to work in an atmosphere that you aren't breathing.

Re:Safe Space?

It's not plastic.

It's Kevlar fiber, generally, along with a variety of other materials, all of which have been tested in space or are currently on the space station. Just because a cheap injection-molded plastic toy breaks easily doesn't mean that all non-metallic materials are easily broken.

They've already worked the water supply angle out there. It depends on the project. The Transhab had the water supply going down the center, so you could stay in the shadow of it during radiation events.

Leakproofing is one of the problems they solve to make it all work. Just because a cheap rubber balloon can't hold pressure for years on end doesn't mean that all non-metallic materials have leaks.

Re:Micrometeoroids Much?

Those micrometeoroids piercing the skin isn't too bad for the bubble. Just a small hole. It's the people and equipment inside that will hate getting sprayed with debris. The way they take care of it on space stations is to create bumpers. An outer shell takes the initial impact. The meteoroid punches through, but shatters and vaporizes, spreading in a plume. The second layer then gets to absorb a reduced impact over a greater area. There's more to it, but that's the basics. To protect an inflatable habitate, it might require a double-bubble, like the Zorb http://www.zorb.com/ [zorb.com]. Inflate the outer bubble at far less than 1 atm and let it take the punctures. Still have to fix the leaks, but they will be far slower. The inner bubble will be unpunctured.

Re:The next logical step

The enemy's door is down! Duh!

-jcr