Author Topic: Composite Materials in Launch Vehicle and Space Vehicle Structures  (Read 11629 times)

Offline DaveJes1979

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Howdy, all.

I've been wondering what the technical reasons are behind the fact that you still see most space hardware being made out of metals such as aluminum and titanium.  I work for a company that makes really amazing airplanes with mostly (>90%) carbon fiber reinforced plastics, mostly from pre-preg cloth w/ epoxy matrix.  Even without the use of autoclave (heck, we used to make whole airplanes w/ wet layup only!) we end up with incredibly light, efficient structures using a 1 atm vacuum bag and oven cure.  It seems that the space industry is even MORE reluctant to make the switch from metals to carbon or Kevlar composites than even the commercial aviation industry (the Boeing 787 being the very first crack at a mostly-composite airplane).

As I review the proposals for the ARES LVs and Orion, I still see aluminum being used everywhere, even at this late date.  The Orion CM and SM use Al-Li, as do the main H2/O2 tank stages on the Ares I and V.  The solids on both Ares rockets remain steel, inherited from the Shuttle.

It seems that the space industry only considers composites good for making payload fairings and perhaps interstages.  I can only think of a few exceptions, such as the graphite-wrapped strap-on solid boosters used in some LVs (all unmanned at this point), and some of the structure of unmanned satellite buses.

I cannot, offhand, think of any technical justification for this, other than the difficulty of changing the infrastructure and tooling to do large-scale composite manufacture.  The problem of outgassing on components that spend significant time in space has already been solved, as can be seen on some satellite structures, by using different matrix materials.

Does anyone else have any more insight into this?  I'm very curious, seeing as how one would think that using more composite-dependent structures would help solve the extraordinarily pressing weight problems that space designers face (Orion/Ares being only one such example).

Offline meiza

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Well, there are lox, hydrogen and cryogenic temperature compatibility issues... X-33 tried composite tanks and it didn't work very well but the state of the art has advanced somewhat since.

But anyway, composite "wet structures" are an option with Ares V, if they get desperate...

Offline DaveJes1979

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That is quite true, Meiza.  But cryo-compatibility issues are currently being addressed, and may perhaps have workable solutions in the relatively near-term:

http://www.compositesworld.com/articles/an-update-on-composite-tanks-for-cryogens.aspx

Anyway, two things are still left unexplained:

1.  If you don't want to try a bleeding-edge all-composite linerless solution, why not a good old-fashioned composite-wrap aluminum liner pressure vessel?

2.  What about all the other structures that aren't in direct contact with cryogenic fluids?


Offline meiza

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1) Probably a composite wrap Al liner vessel doesn't save that much weight and is potentially unreliable.
2) I think the interstages and adapters are already carbon fiber in some launchers like Delta IV, probably Ares I and V too...

Offline Jim

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A.  That is quite true, Meiza.  But cryo-compatibility issues are currently being addressed, and may perhaps have workable solutions in the relatively near-term:

Anyway, two things are still left unexplained:

1.  If you don't want to try a bleeding-edge all-composite linerless solution, why not a good old-fashioned composite-wrap aluminum liner pressure vessel?

2.  What about all the other structures that aren't in direct contact with cryogenic fluids?


A.  Not near term enough

1.  They are pressure vessels and not structural tanks

2.  Delta-IV and Atlas-V use them as fairings, intertanks, interstages, aftbodies, engine heat shields, payload adapters, etc.  The only thing they don't use them for is propellant tanks

Online DaveS

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We're talking about cryo stuff here, liquids that must stay in their tanks for hours without leaking like there's no tommorow.

X-33 as meiza writes was cancelled because they couldn't get the composite LH2 tank to stop leaking!

LH2 is really really super-cold at -423.17F so the tank must be able to cope with that temperature for a long long time without cracking when it is in contact with the liquid.

Also an interesting fact from the Space Shuttle is that the External Tank actually shrinks with as much as 6 inches when it is filled with LOX and LH2.
"For Sardines, space is no problem!"
-1996 Astronaut class slogan

"We're rolling in the wrong direction but for the right reasons"
-USA engineer about the rollback of Discovery prior to the STS-114 Return To Flight mission

Offline DaveJes1979

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Jim,

It is not obvious to me why composite-wrapped tanks could not be engineered to take structural/flight loads, not just pressure loads, same as an Al-Li tank.  The fiber layup could be adjusted to accomodate additional loads.

Of, if you prefer, designing the outer structure of the stage to take flight loads exclusively, while the tanks strictly take pressure loads. 

Also - when have you ever seen a composite RP-1 tank? 

This still leaves the Orion CM and SM.  Why more aluminum?  If you are worried about the crew cabin, our buddies at Scaled Composites have made at least two vacuum or near-vacuum composite air/spacecrafts with crew cabins, and are working on a third.

And why aluminum in a service module?
« Last Edit: 07/15/2008 11:41 PM by DaveJes1979 »

Offline cozmicray

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The composite cryo tank problems were solved about two years after the
canceled X-33 program.  Delta Clipper flew composite LOX tanks.

The UARS and Terra spacecraft have a great deal of composite structure, Main structure, composite honeycomb panels because it stays in alignment.
So much Composite it had to wrapped in metal to form a good ground plane
to ground electronics and bleed off space charge.  GE developed many techniques
to glue Graphite epoxy tubes to titanium fittings to withstand STS and ELV launch loads.
Titanium prop tanks are wrapped with composite to meet safety standards and provide load paths for very heavy prop filled tanks.

Offline quickshot89

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once we have nano-tubes made from carbon, i can see things changing to allow for more composite use in spacecraft


Offline DaveJes1979

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The composite cryo tank problems were solved about two years after the
canceled X-33 program.  Delta Clipper flew composite LOX tanks.

And, if you recall, the X-33 tanks were MULTI-LOBED tanks!  It is a far simpler matter to construct standard, axi-symmetric surfaces of revolution (i.e. cylinders w/ spherical domes).

Offline DaveJes1979

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I should also have noted that the DC-XA program successfully tested and flew a composite HYDROGEN tank (not multi-lobed).  The oxygen tank, however, was a Russian-made Al-Li tank.
« Last Edit: 07/15/2008 11:40 PM by DaveJes1979 »

Offline edkyle99

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My understanding is that the Ares designs, especially the Ares V design which is still in its early stages of being defined, are adopting more composite elements as time progresses.  Pretty much all non-pressurized components are set to be composite at this juncture, for example, and consideration is being given to composite SRB casings and/or the use of much more composite content on the Earth Departure Stage, which would provide the biggest "bang" for the buck invested.

If Boeing 787 is the "plastic airplane", Ares V could turn out to be the "plastic rocket".

 - Ed Kyle   
« Last Edit: 07/16/2008 12:22 AM by edkyle99 »

Offline simonbp

WRT the Orion SM, wouldn't the issue be chemical compatibility with the corrosive/reactive hypergolic propellants?

Simon ;)

Offline Jim

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Jim,

1.  It is not obvious to me why composite-wrapped tanks could not be engineered to take structural/flight loads, not just pressure loads, same as an Al-Li tank.  The fiber layup could be adjusted to accomodate additional loads.

2.  Of, if you prefer, designing the outer structure of the stage to take flight loads exclusively, while the tanks strictly take pressure loads. 


1.  And who is going to pay for the development of said tanks and the infrastructure to manufacture them.

2. That would weigh more than the monocoque stage


Offline Kahuna

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Composite cryotanks have been successfully made and the DC-XA tank was flown 5 times at White Sands in 1996. It did a half loop at 20,000' on final flight.
Initial composite cryotank was made as part of NASP program in 1988 to demonstrate that graphite/epoxies could contain LH2 without leaking. Tank was multilobal and held 900 gal of LH2.
The DC-XA tank was cylindrical with hemi- domes and had monolithic wall. Interior insulation was the Douglas invented system of reinforced urethane foam bonded to wall, same as used on S-IVB on Apollo Program.
Primary concern with composite tanks is permeabilty of H2, however, we showed that leakage does not occur until 50 or more thermal fill/drain cycles produce enough microcracking in matrix to allow gas leakage. Wall thicknesses down to 30 mils did not leak and bonded joints didn't leak either. But major criteria is the number of cycles tank has to withstand. For expendable rockets, 50 cycles is usually sufficient.

It was too bad that NASA awarded Lockheed the X-33 contract after we had built and flown the DC-XA demonstrator which flew 12 times and on last 5 flights had the composite LH2 tank with 6000 gal of LH2 fuel.
I know all this because I built both tanks while at McDonnell Douglas.

Offline renclod

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This still leaves the Orion CM and SM. 

NASA Engineering and Safety Center (nesc.nasa.gov) is working on a Composite Crew Module (CCM).

http://www.nasa.gov/pdf/260362main_NESC%20TECH%20UP%202007.pdf
page 18




Offline Patchouli

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Composite cryotanks have been successfully made and the DC-XA tank was flown 5 times at White Sands in 1996. It did a half loop at 20,000' on final flight.
Initial composite cryotank was made as part of NASP program in 1988 to demonstrate that graphite/epoxies could contain LH2 without leaking. Tank was multilobal and held 900 gal of LH2.
The DC-XA tank was cylindrical with hemi- domes and had monolithic wall. Interior insulation was the Douglas invented system of reinforced urethane foam bonded to wall, same as used on S-IVB on Apollo Program.
Primary concern with composite tanks is permeabilty of H2, however, we showed that leakage does not occur until 50 or more thermal fill/drain cycles produce enough microcracking in matrix to allow gas leakage. Wall thicknesses down to 30 mils did not leak and bonded joints didn't leak either. But major criteria is the number of cycles tank has to withstand. For expendable rockets, 50 cycles is usually sufficient.

It was too bad that NASA awarded Lockheed the X-33 contract after we had built and flown the DC-XA demonstrator which flew 12 times and on last 5 flights had the composite LH2 tank with 6000 gal of LH2 fuel.
I know all this because I built both tanks while at McDonnell Douglas.

The delta clipper is a program that should never have been canceled.
I feel if the program was continued we'd have an orbital vehicle flying today either SSTO or at least TSTO and would not even be worried about a gap with the shuttle or trying to sell a retro vehicle and broken LVs to an uninterested public.

Outside NASA I feel use of composites in many structures is the future.
A great example would be Bigelow's space station modules.

BTW I'm still dumb founded LM won the CEV contract after they screwed up the X33.
« Last Edit: 08/17/2008 06:47 AM by Patchouli »

Offline Jim

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BTW I'm still dumb founded LM won the CEV contract after they screwed up the X33.


Because the first 4 words of your response is applicable.

1.  X-33 was a launch vehicle and not a spacecraft.  Two different things.

2.  Two different LMs.  CEV is run out of Denver (old Martin).   X-33 was run out of sunnyvale

Offline Kahuna

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The primary issue with reusable rockets is the mass fraction which requires weight of vehicle to be down around 15% of total launch weight. The majority of launch weight is fuel and then payload. To get mass fraction down to a practical value, you need to use composites in primary structure. It can save 20% over aluminum. Composites are not always a panacea, but where possible, can provide dramatic savings.
On DC-XA, LH2 tank was also primary structure of vehicle, acting as backbone for all the support hardware, including the Russian LOX tank ontop which initially was a piece of junk. (They were given the Al-Li tank as a gesture to keep their science guys from working for Saddam. Quality of resulting tank was poor and unflyable until our welding shops rewelded much of it and fixed a 16" long crack.)

Difference between launch rocket and spacecraft can get moot because a reusable does park in space with Station for days at a time, so it has to comply and survive the requirements for outgassing, contamination, life support, etc.

In my opinion, NASA has lost the willingness to take big risks and doesn't follow thru with programs that don't have immediate success. When beginning a new venture, you always have problems that don't have nicely packaged answers. If you had the answers beforehand, there would be no development required. So you jump into the technology with the understanding that stuff will happen and you need to accept that things may blowup and not look good to public. The real successes come from working thru those issues to a functioning solution and for management to have the guts to take the heat while engineers are finding the answers.

Offline Jim

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Difference between launch rocket and spacecraft can get moot because a reusable does park in space with Station for days at a time, so it has to comply and survive the requirements for outgassing, contamination, life support, etc.


X-33 was not to be an orbital vehicle. 
The comment that "was a launch vehicle and not a spacecraft" was in response to why LM got the CEV contract

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