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NanoRacks Plans To Turn Used Rocket Fuel Tanks Into Space Habitats (ieee.org)
An anonymous reader writes from a report via IEEE Spectrum: A couple of weeks ago NASA announced it has committed $65 million to six companies over the course of two years for the purpose of developing and testing deep-space habitats that could be used for future missions to Mars. One of the six companies, called NanoRacks, is attempting to take empty fuel tanks from the upper stages of rockets and turn them into space habitats on-orbit. IEEE Spectrum reports: "A rocket like the the Atlas V, which can deliver payloads of nearly 19,000 kg to low Earth orbit, consists of three primary pieces: on the bottom, you've got the first stage booster, which consists of a huge engine and some big tanks holding kerosene fuel and oxidizer. Above that, there's the second stage, which consists of one or two smaller engines, a big tank for storing liquid hydrogen fuel, and a smaller tank for oxidizer. The payload, which is what all of the fuss is about, sits on top. The first stage launches the rocket off of the pad and continues firing for about four minutes. Meanwhile, the second stage fires up its own engine (or engines) to boost the payload the rest of the way into orbit. On the Atlas V, the second stage is called Centaur. Once Centaur gets its payload where it needs to go, it separates, and then suicides down into Earth's atmosphere. Getting a payload into space is so expensive because you have to build up this huge and complicated rocket, with engines and guidance systems and fuel tanks and stuff, and then you basically use it for like 15 minutes and throw it all away. But what about the second stage? You've got a whole bunch of hardware that made it to orbit, and when getting stuff to orbit costs something like $2,500 per kilogram, you then tell it to go it burn itself up in the atmosphere, because otherwise it's just useless space junk." NanoRacks thinks this is wasteful, so they want to turn these tanks into deep space habitats. IEEE notes that the hydrogen fuel tank on a Centaur upper stage has a diameter of over 4 meters, and an interior volume of 54 cubic meters, while the inflatable BEAM module that arrived at the ISS earlier this year has an interior volume of 16 cubic meters. For more details, IEEE Spectrum spoke with Jeff Manber, CEO of NanoRacks, and Mike Johnson, NanoRacks' Chief Designer. You can read their responses here.
There's lots of research demonstrating that long periods of time spent near campfires cause serious health issues. Absent cleaning the air, such as with a complete air-conditioning and filtering setup, it is unhealthy for humans to be near a campfire for any significant length of time. ... so this isn't viable.
It's about risk. The risk of you cooking your food (thus exposing you to carcinogenics) compared to the risk of eating uncooked food (which we did for MILLIONS OF YEARS) is a trade-off.
Do you sacrifice those temporary, mostly reversible health issues (comparatively vanishingly small compared to the general risk of take-off and space travel in general, to be honest) for the opportunity to live and work in an entirely new environment?
To be honest, mining is an incredibly dangerous profession. Scouting the bottom of the oceans too. Diving near oil rigs. All of these things are MUCH HIGHER RISK than the health effects of prolonged space travel. And people do them every single day.
Even simulated gravity doesn't solve the problems of space travel, so even your solution is completely useless in terms of combating all - or even the significant - health risks. Radiation would be the killer, long-term.
To be honest, there are thousands of people, most of them sane, educated and intelligent, willing to sign up to a one-way mission to Mars.
In the same way that for centuries, people fought to get to the top of Everest or to the middle of the arctic poles. Of course it wasn't without risk. It can't be. But that's how you discover the risk, reduce them and compensate for what you can't reduce.
So re-using a fuel tank as a habitat in space is just one sensible method of reducing risk - of having to send up more junk to live in, so you don't have to live in cramped conditions, or needlessly spend money on more accommodation when you could spend it on safety gear or fire tests or whatever.
The article intro above actually explains this, if you read it. The fuel in this tank is BURNED, getting the payload into orbit. In the Apollo mission days, the payload was e.g. a third stage that went to the moon and back, as these are BIG rockets. In the past, the second stage tanks would be "thrown away" and allowed to reenter and burn up, but that's slightly insane given the roughly 32 MJ/kg direct energy cost (multiplied by a few orders of magnitude) of lifting anything at all into orbit.
The reasoning is then as follows: We've gotten this great big cylindrical chunk of pressure-tested metal -- remember, it held liquid hydrogen at HIGH pressure securely through a launch exerting many g's of acceleration -- into orbit. It already cost us millions of dollars to build, and tens of millions to get it into orbit as a SIDE EFFECT of lifting this other, really big payload. Let's not waste it!
So, what can we do with it? Well, given that it is roughly the size and even the shape of a good sized mobile home or the living volume of early submarines, making it into pressurized living space is an obvious choice. It is pressure tested at many times the 0.5-1.0 atm pressure differential needed to sustain human life in space. It is made of high quality, carefully x-rayed, stress-tested metal (because NASA would be insane to fire a rocket into space with humans on board with anything less holding in the fuel of the rocket). The metal has been carefully crafted and annealed to be able to handle liquid hydrogen temperatures without becoming brittle, so it is also proofed against your concerns with heat -- humans cannot tolerate any temperatures this metal is unlikely to be perfectly capable of withstanding, and besides, shielding it from sunlight is a matter of wrapping it in a reflective mylar blanket that weighs almost nothing and can easily be shipped up as part of the conversion kit.
As for radiation shielding -- that I don't know about, but I very much doubt that it is an issue. If the Earth gets hit dead on with a solar flare, I don't think there is anything we could reasonably put humans inside in orbit that would be "safe". It's not clear that being on the Earth's surface inside the atmosphere would be "safe". If the metal that the container was made of wasn't adequate as shielding during such an event -- I'm pretty sure it would be perfectly good most of the time -- and we had something better (but smaller and more expensive) then humans could retreat into the latter as a "shelter" to wait out the storm.
Life support machinery and furniture for the interior of the tank turned into habitat is a small fraction of the weight of the whole thing, and weight into orbit costs like gold.
Now let's compare costs. Suppose you used the Atlas to launch an Earth-built space habitat directly into space as to you suggest, and just wasted the second stage tank as usual. It costs you one launch to get the habitat into space, and the interior volume is almost certainly going to be smaller than the second stage tank volume. Now suppose that you take the empty tank and just hook it onto the habitat you just launched (which already has all of the life support machinery, radiation tolerance etc that you are worried about. Voila! You've more than doubled your available habitat volume in space at (almost) zero additional marginal cost! EVEN if it isn't AS safe as the primary habitat in the event of a solar storm, well, astronauts can always retreat into the primary habitat during such a storm and still use the tank as room for experiments, hydroponics, their ping pong table, room to spread out in to avoid going nuts.
The last question is: What do you have to do to the tank to FACILITATE this so that it isn't being done on an ad hoc basis? As you say, certain pieces of work are way cheaper on Earth than they will be in orbit. Should we build the tank out of slightly different metals so it IS a better radiation shield? Should we pre-install ductwork for ventilation and wiring and liquid
Even when the experts all agree, they may well be mistaken. --- Bertrand Russell.
Yes, it's totally that simple! The ISS has hundreds of thousands of parts, but only because congress insisted on adding thousands of Machines That Go Ping for no good reason. And random objects totally love being submerged in liquid oxygen and liquid hydrogen. And empty tanks are totally easy to haul all the way to orbit when pre-loaded with fittings and jackets and extra tanks. And building things in space (including bloody *welding*) is such a nothing job that totally costs nothing!
Meanwhile, in the real world...
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It is pressure tested at many times the 0.5-1.0 atm pressure differential needed to sustain human life in space.
It is pressure tested on earth before being subjected to the intense rigors of launch. All bets are off as to whether it retains long-term integrity, as it has not been designed to do that. It's easy to find situations where a vessel will will not leak at high pressure differentials, but will leak at low pressure differentials. That we don't know the answer as to what will happen to the current designs is a good reason to test, but it should not be put forth as incontrovertible evidence of future success.
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