NASA tests composite cryogenic fuel tank

Mark Friedenbach · 2013-07-02 15:54:04

Title says it all:

http://www.spaceref.com/news/viewpr.html?pid=41131

Can we have our X-33/VentureStar back, please?

JoshNH4H · 2013-07-02 20:36:27

I don't think composite tanks would have been enough to save X-33/VentureStar. Those were doomed from the start for the same reason as Ares I, Ares V, and SLS are.

GW Johnson · 2013-07-03 09:46:44

20 cycles isn't reusable. This is essentially one-shot technology. But it is a dramatic weight-saver. That's good.

GW

RGClark · 2013-07-03 15:50:47

JoshNH4H wrote:

I don't think composite tanks would have been enough to save X-33/VentureStar. Those were doomed from the start for the same reason as Ares I, Ares V, and SLS are.

I don't see that connection.

Bob Clark

Mark Friedenbach · 2013-07-03 16:39:47

I don't think there is one, although it is true that X-33/VentureStar would not have resulted in an operational SSTO, which was the hoped-for end goal of the program. Rather it was a rocket-powered intercontinental aircraft (Mach-12 cruise above the atmosphere, ~1.5hrs to anywhere on Earth). IIRC one and only thing which really killed it was the failure in creating a composite LH2 tank.

More interesting, I think, is that the X-33 could have been the basis of a Martian SSTO, and probably *would* have worked have worked on Earth or Venus with air-breathing NTR. More likely, an external tank could have enabled orbital velocity, similar to shuttle but without the SRBs.

Rockets aren't my thing though, so I should probably shut up and let Bob Clark or GW take over. My interest in X-33/VentureStar was that it cut out most of the operational costs of shuttle.

RobertDyck · 2013-07-03 17:44:16

X-33/VentureStar was cancelled due to corporate greed. Nothing else.

It was designed to use leading-edge/state-of-the-art technology in everything. But nothing radically new. Aerospike engines were examined/evaluated in the 1970s for the original Shuttle. Lifting bodies were developed in the late 1960s and early 1970s, specifically for the Shuttle. Heat shield tiles were developed for the Shuttle. And composite cryogenic propellant tanks were demonstrated by DC-XA. It used an aluminum/lithium alloy LOX tank, similar to the Shuttle's ET, but from a different manufacturer. And a carbon-fibre/epoxy LH2 tank. So every component of X-33 was demonstrated, it only required putting the pieces together.

However, NASA also wrote into the contract that any cost overruns had to be shared between contractor and NASA. Then Lockheed-Martin made a last minute change: from solid wall composite propellant tanks, to hollow wall / honeycomb structure. They built a tank for X-33, and tested with liquid nitrogen. It held, appeared to work, then when they warmed it to room temperature it disintegrated. There were details, but the only thing that matters is the thin walls of the honeycomb cells developed thin cracks, liquid seeped into the cells, when they drained it much of the liquid in wall cells remained. When it warmed, expansion sealed the cells shut. Then the liquid nitrogen boiled, producing gas and pressure. The cells burst. This demonstrates a hollow wall honeycomb structure is not compatible with cryogenic propellant.

X-33 was supposed to be a scale model test vehicle. It cost millions of dollars, yet would fly a sub-orbital trajectory only. It would never achieve orbit, or carry any cargo. If everything worked perfectly, then X-33 was a multi-million dollar waste of money. But if something went wrong then it could be fixed on this 1/4 scale model, much cheaper than trying to fix full size VentureStar. Call it insurance: only worthwhile if something does go wrong. Well something did, the last minute tank change. The obvious conclusion was to go back to the original solid wall tank.

But no, Lockheed-Martin then demanded NASA pay for replacing the tank. But NASA activated the clause that said the contractor has to share the cost of any cost overrun. But Lockheed-Martin had not intention to share any costs. They had no intention to honour that clause in the contract. All work stopped while the lawyers argued. This stand-off went on for 2 years. There was a presidential election, George W. saw VentureStar as the pet project of his Democrat rival, so cancelled the whole thing.

Did Lockheed-Martin learn? Did NASA gain any backbone? No. Contractor overruns continue.

During the years of lawyers arguing, there was a proposal to replace the propellant tanks with aluminum. But engineering calculations showed it would be too heavy to get off the ground. VentureStar required composite tanks.

But the linked article talks about composite tanks as if they're new. But the last flight of DC-XA was 7 July 1996. That's 17 years ago. Hardly new.

Last edited by RobertDyck (2013-07-03 17:47:42)

RobertDyck · 2013-07-03 17:45:55

GW Johnson wrote:

20 cycles isn't reusable.

The article says they tested through 20 cycles. It doesn't say the limit is 20 cycles. If it could only withstand 20 cycles, that wouldn't be reusable. I can only hope their tank can do better.

RGClark · 2013-07-03 22:53:41

Further discussion of this on Aviation Week:

NASA Sees Potential In Composite Cryotank.
By Frank Morring, Jr.
http://www.aviationweek.com/Article.asp … 592975.xml

A key factor in the failure of the composite tanks on the X-33 was their conformal shape. This meant they followed the unusual, non-cylindrical shape of the lifting body itself. As RobertDyck noted, composite LH2 tanks had already been demonstrated with the DC-X program. These however were cylindrical tanks. Lockheed found it difficult to make the conformal tanks composite while maintaining their lightweight.
In regards to the reusable SSTO question though it doesn't have to be a lifting body. It could be cylindrically shaped using powered descent as SpaceX is planning with the separate stages of a reusable Falcon 9, or by adding wings to the cylindrical rocket body, a la the X-37b.
To this last, it is notable Boeing makes the X-37b, and is doing this research on composite tanks. Also notable is that about the X-37b, Boeing said it is investigating using it as a model for a SSTO:

Boeing proposes SSTO system for AF RBS program.
11 Jun 2011, 15:47 UTC
http://www.portaltotheuniverse.org/blog … ew/121527/

Bob Clark

GW Johnson · 2013-07-04 12:11:46

Aside from the money-driven politics, there is another problem they had on X-33. Whether metal or composite, a conformal-shaped tank makes sense only if it is unpressurized.

No sane engineer would propose even a moderate-pressure pressurized vessel of any kind that wasn't cylindrical or spherical. When you store cryogenics, some pressure is usually involved, or else boiloff losses are very high. But apparently a lot of bureaucrats and managers were willing to propose it.

It's really hard to get such a tank to survive realistic loads, especially conformal ones. Further, why they tried that honeycomb thing beats me. Especially as easy as hydrogen penetrates right through so many materials. That was a disaster waiting to happen.

There is a limited class of conformal geometries you can approximate with cylindrical components. The structural soundness looks good, but the manufacture is very difficult. I once worked out a solid rocket motor case that resembled an air mattress, for a conformal situation. That's a very high-pressure vessel, by the way. It would have worked, and was only a mild nightmare to build. Though, once they saw it, nobody wanted to risk it anymore.

GW

RobertDyck · 2013-07-04 13:59:46

GW Johnson wrote:

why they tried that honeycomb thing beats me.

I think they wanted it to fail. They deliberately caused a cost overrun. Were shocked when NASA was serious about them paying.

SpaceNut · 2016-04-09 21:20:43

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#1 2013-07-02 15:54:04

NASA tests composite cryogenic fuel tank

#2 2013-07-02 20:36:27

Re: NASA tests composite cryogenic fuel tank

#3 2013-07-03 09:46:44

Re: NASA tests composite cryogenic fuel tank

#4 2013-07-03 15:50:47

Re: NASA tests composite cryogenic fuel tank

#5 2013-07-03 16:39:47

Re: NASA tests composite cryogenic fuel tank

#6 2013-07-03 17:44:16

Re: NASA tests composite cryogenic fuel tank

#7 2013-07-03 17:45:55

Re: NASA tests composite cryogenic fuel tank

#8 2013-07-03 22:53:41

Re: NASA tests composite cryogenic fuel tank

#9 2013-07-04 12:11:46

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#10 2013-07-04 13:59:46

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#11 2016-04-09 21:20:43

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