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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.
So an empty metal container made for storing fuel is also a great place to live? It has precisely the right properties in terms of structural integrity, heat and radiation shielding, etc.? Putting all the required machinery to sustain life inside is cost-free?
Or, if it is none of those things, changing all that stuff in orbit is actually cheaper and easier than launching a complete habitat from earth?
(hint: the answer to all these questions is "no")
From the interview: "The reason that Skylab wasn't build like this is kind of a strange story: [NASA] had fewer Saturn IBs than they had Saturn Vs, so von Braun just decided to use a Saturn V and fly up a "dry" lab, with all of the equipment aboard it already."
Um, not quite. When a 'spare' Saturn V became available (because a lunar mission was cancelled), they swapped from a IB 'wet' lab to a V 'dry' lab because the 'wet' labs were very expensive for their very low capability. The expense came from needing to have considerable amounts of structure and infrastructure designed to survive inside the cryogenic conditions inside the tank, from redesigning the tanks to serve a dual role, and then re-certifying the whole deal for flight. The low capability came from the requirement that everything that couldn't survive a bath in deep cryogens having to be manhandled into place via the very narrow docking hatch. While a dry lab was more expensive than a wet one - the leap in capability was far greater than the leap in cost.
That's also why NASA built their ISS modules with the large CBM hatches - manhandling large amount of stuff through tiny hatches (like those the Ixion will use) simply isn't very efficient. (And that's without considering the headaches that splitting all your equipment down into tiny chunks brings. Not just handling - but installation and integration too.) All of the ISS cargo craft that NASA is responsible for uses CBM, as does the Japanese HTV.
"In the commercial sector, it's getting interesting, because people are taking more risks. Not unnecessary risks, but acceptable risks to reduce costs."
Moving your man hours (outfitting the module) from expensive ones on the ground to hellishly expensive ones on orbit is not a recipe for cutting costs. Especially since you still have to pay for the launch of the module (Centaur) *and* the launch of the stuff to go inside it. (You can't piggyback because no Centaurs are headed anywhere near the ISS.) Even in lower inclination orbits, the mission module, the rendezvous systems, and outfitting the Centaur to survive years on orbit are all going to cost money and cut into it's payload - which will make piggybacking unattractive to Centaur's usual customers.
"We want to keep hardware costs as low as possible: it's not about building something on the ground that could cost hundreds of millions of dollars. Why do that when you have perfectly good hardware going to space, paid for already?"
You don't have perfectly good hardware going to space already. You have a vehicle designed for a completely different purpose and completely lacking the "stuff" customers will pay you for going to orbit.
Or, in short, nothing in the article or interview leaves me with a warm fuzzy that they've solved any of the well known problems with 'wet' systems.
Shuttle ETs never got up to a stable orbit. It would have been possible to use the OMS to take them up there, but then the Shuttle would have had basically no payload capacity on that mission.
Of course, that's one of the lesser problems with the concept. Often proposed, often investigated, but never considered worth throwing serious money into.
"99 dead duelists of Dios on the wall. 99 dead duelists of Dios! Take one's ring, pass it around..."
I don't think anyone would argue that it costs nothing to do this. Nor would they argue that it's easy. The argument would simply be whether or not it's cost effective. Can it be done for less than the costs of launching a fully developed habitat from the ground.
That's the job of the company providing the work. If they can make it work, more power to them. If they can't, failed business model. If they can't and it gets funded through tax dollars as a huge boondoggle, then it becomes a problem for the masses.
Prove that it can't be done cost effectively. Not random "Oh sure!! That'll work great!!! No costs at all!"
yvan eht nioj
Dude, my job is doing thermal testing on spacecraft. I can tell you thermal design involves just slightly more than "wrapping a mylar blanket around it".
Also, the fact that rocket stages and habitats are both in some sense metal boxes does not in any way imply they are therefore interchangeable. Both are highly specialized parts that have very different goals. Rocket stages simply cannot afford all the extra weight necessary for them to function as a habitat (life support equipment, solar cells, meteorite shielding, access hatches, equipment for the astronauts to do useful work with, etc.). Besides, the biggest (lower) stages never make it into orbit anyway (only the top stage does, and why do you think that is?). The top stage is typically quite small. It's also not just a hollow shell; inside are multiple tanks (for fuel and oxidiser), the engine itself, pumps, electronics, etc. You'd have to remove all that.
So let's say you want to add all the necessary equipment later. How is it going to get into orbit? For that you need _another_ launch! And then you need to do a hell of a lot of precision engineering in one of the most hostile environments known to mankind, just to remove the old contents of the stage, and replace it by new contents which you might as well have launched ready to use from Earth (the weight is going to be the same, whether you pack it up tightly or not, after all).
You also have to come up with a plan to get rid of any remaining fuel. If it's hydrazine (not uncommon on upper stages), that's pretty toxic, and no, you cannot just open the hatch and hope it disappears into space.
It's a damn shame they didn't do it with the shuttle external fuel tanks. Those things were huge. How many would we have in use now if that was part of the design?
A lot of people lobbied hard for that. My understanding is that the biggest barrier standing in the way was that the spray-on foam insulation on the external tanks would likely "popcorn" in vacuum, filling LEO with more little bits of debris. (I'm not sure where I read that; it was ages ago.) Junk in LEO is already a big enough problem.