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.

Comments

I don't get it

[telchine]

I don't understand how this can possibly be cost effective. Can anyone explain?

Re:I don't get it

[johannesg]

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")

Re:I don't get it

[Rei]

And the US did launch a converted stage in the 70s with Skylab (albeit, Skylab was built on Earth and didn't contribute propellant / thrust... a rather different beast ;) ). That is, a dry workshop rather than a wet one.

To a rocket scientist, it's "obvious"; to a habitat designer, it's a nightmare. They're designed for dramatically different needs, and in-space construction is very difficult (and thus expensive). Orbital habitats are not just big shells, they're complex structures that take a lot of work to make. The original proponent of the wet workshop concept, George Mueller (who had worked with Von Braun on the idea), himself had switched to arguing for a dry workshop over a wet one by 1969 (this eventually became Skylab), telling congress that the wet concept had become just an inferior stopgap based on necessity rather that desirability.

There's this concept that launch costs are everything. They're not. A lot of times, it really is just cheaper to spend more in launch costs than to do more engineering, assembly, and/or in-orbit work.

Re:I don't get it

[rgbatduke]

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

Re:I don't get it

[Whatanut]

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!"

Re:I don't get it

[pz]

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.

Re:I don't get it

[johannesg]

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.

Re:I don't get it

[Mike Van Pelt]

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.

NanoRacks

[Gravis Zero]

I guess tinytits.com must have already been taken. ;)

Too bad they can't use the SS ext. tanks

[wisebabo]

Too bad it's too late for them to be able to use the Space Shuttle external tanks.

There were around 135 launches (so I guess the number of tanks that made it almost to orbit would be 134). Of course many (most?) of these missions were not in the correct orbital plane for use as space habitats (I guess they would not be easily reachable by subsequent manned flights). Still when one considers the sheer volume (about 2 million liters!) you'd think they'd be very useful. Also because they didn't have much heavy external hardware (like engines) they'd be easier to move around and keep in orbit.

What could they have been used for? I'm not sure but a whole bunch of interesting applications come to mind. If they could hold a full atmosphere's worth of pressure they'd make huge living spaces. If only a low pressure environment could be maintained, perhaps plants could survive in a mostly CO2 atmosphere; with a slow rotation about the long axis and a central light column running down the length of it, it could be a huge hydroponic garden for waste recycling and food. If they turned out to be pretty durable then perhaps propellent storage or even reuse as fuel tanks for interplanetary expeditions could be envisioned. Since they are light, perhaps they could be sent, empty, to a passing comet to refill with water and then sent back to earth orbit using some of the collected mass as fuel. If nothing else, they could have been cut up and used as raw materials for use in providing shielding against micrometeorites.

Anyway, there were well over a hundred of these giant things that, with just a little more delta-V (and admittedly, long term boosting to counteract atmospheric drag) could have been a valuable orbital resource. I guess it wasn't done because some infrastructure wasn't available (cheap orbital "tugs" perhaps using ion drives for low fuel consumption) and the vision and political will wasn't there. Too bad because this could've been like Skylab but hundredfold.

Re:Too bad they can't use the SS ext. tanks

[Rei]

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.

Nonsense

[DerekLyons]

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.

Re:Stupid

[ledow]

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.

"Tank Farm Dyname"

[dpilot]

Story by David Brin, using Shuttle external tanks. Whaddya know, the whole story is on the web: http://www.davidbrin.com/tankf...