NASA orders SpaceX to examine changing to Inconel tanks from carbon fiber

[ecarfan]

This was posted yesterday on forum.nasaspaceflight.com by user @gongora, claimed to be a (see below) Task Order from NASA to SpaceX for an “Inconel tank feasibility study...regarding full transition to Inconel tanks for crewed vehicles”. If you don’t know what Inconel is, see Inconel - Wikipedia .

My interpretation of this NASA directive is that NASA does not believe that carbon fiber tanks are sufficiently reliable for vehicles that transport humans. Recall that the AMOS-6 mission failed when the F9 exploded on the pad during fueling prior to a planned static fire because one of the second stage COPVs (carbon-fiber overwrapped pressure vessel) that hold helium failed (details at Amos-6 - Wikipedia ).

I hope I am interpreting this wrong and this does not mean what I think it means. If SpaceX has to redesign the F9 to use only Iconel tanks for NASA crewed missions (taking astronauts to the ISS) that will take years.

I am waiting for industry experts on sites like Spaceflight Now – The leading source for online space news to weigh in on this news so I can better understand it.

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• 80KSC018F0039
  Effective Date 12/15/2017, Completion Date 04/16/2018 $10,134,469.00
  
  Performance of this Task Order is in accordance with the terms&conditions of the base contract NNK14MA74C. The purpose of the Commercial Crew Program (CCP) is to facilitate the development of a U.S. commercial crew space transportation capability with the goal of achieving safe, reliable and cost effective access to and from low Earth orbit (LEO) including the International Space Station.
  
  In accordance with the Commercial Crew Transportation Capability (CCtCap) contract NNK14MA74C, the Contractor shall complete the design, development, test, evaluation, and certification of an integrated CTS capable of transporting NASA crew to and from the ISS, in accordance with the design reference missions and the certification standards and requirements specified in this contract.
  
  In accordance with Attachment J-03, Contract Performance Work Statement (PWS), the task ordering procedures and other terms and conditions in the contract, the Contractor shall perform special studies, test and analyses, as initiated by written direction from the Contracting Officer. IDIQ tasks may include performing technical, cost, schedule and risk assessments for potential new or changes to existing requirements, as identified by the Government, for their impact on the Contractor's design, schedule and cost/price as it relates to CCtCap or life cycle activities; performing additional analyses, modeling, and/or tests of hardware or software to provide further confidence and understanding of robustness of design and advance planning, feasibility or trade studies for development or certification activities.
  
  In accordance with this task order statement of work, the Contractor shall perform an Inconel tank feasibility study and submit a cost proposal to implement follow-on Inconel development and initial cost information regarding full transition to Inconel tanks for crewed vehicles. The feasibility report includes manufacturing R&D activities performed, results; and detailed information regarding the Spin-forming Process.
  
  The task order also includes Solid Oxygen (SOx) test stand development and build; ground fluid system and supporting infrastructure development in order to collect information regarding the pressurized tanks used in the CTS.

 

[ecarfan]

Here is the link to the post SpaceX CCtCAP Milestones

 

[scaesare]

Just a quick note that the title sounds like NASA is issuing a "thou shall" order, whereas it appears NASA is actually placing an order for a feasibility study.

Nonethless, thanks for the info.

 

[CalBlue 85D]

I'm involved in a construction project that required ultra high strength bolts for a marine enviornment and the engineers eventually settled on Inconel as the fabrication material. They are custom manufactured parts, but Inconel was very difficult to source since Tesla is buying so much of the supply for vehicle manufacturing. Evidently Inconel is used in some of the high voltage systems in a Tesla.

 

[ecarfan]

Just a quick note that the title sounds like NASA is issuing a "thou shall" order, whereas it appears NASA is actually placing an order for a feasibility study.

I understand, which is why in my post I quoted from the Task Order “Inconel tank feasibility study...regarding full transition to Inconel tanks for crewed vehicles”.

I didn’t know how to word the short thread title to make that clearer. Perhaps you could suggest something and the mod could change it.

Nevertheless, this required feasibility study strongly points toward NASA preparing to order SpaceX to change to a different tank material, in my opinion. Which has enormous implications.

Note: I posted about this in the Facebook SpaceX enthusiast group and my post appears to have been removed. I am wondering if this Task Order was not supposed to be made public. The admins of that FB group are very conscientious about not publicizing leaked or improperly disclosed information. I have not heard from them so I am only speculating.

 

[gg_got_a_tesla]

... They are custom manufactured parts, but inconel was very difficult to source since Tesla is buying so much of the supply for vehicle manufacturing. Evidently inconel is used in some of the high voltage systems in a Tesla.

Yes, this was needed to get the PxxDs from Insane to Ludicrous:

Elon Musk’s recent “Ludicrous” announcement hints at more synergy between Tesla and SpaceX

 

[AudubonB]

I think that a headline reading

NASA orders SpaceX to examine changing to Iconel tanks from carbon fiber

not only would remove the teeth-jarring "order....potentially change" but more likely reflects the situation.

 

[AudubonB]

...except that as of when I'm typing this, neither the OP, I, nor the Mod can spell "Inconel".....

 

[ecarfan]

Thanks for the thread title change. And by the way, I spelled “Inconel” correctly in the first paragraph of my post and then incorrectly in the third paragraph.

I still think that this NASA order to SpaceX is more significant than it may appear to some. It could result in a major delay in Crew Dragon certification if NASA decides that SpaceX must change to Inconel tanks. The fact that NASA has ordered such a study could indicate that it intends to require such a change.

 

[hockeythug]

SpaceX will play along with the feasibility study and say it's too cost prohibitive at this point to change the design. Given the findings of the Pentagon audit, they have some things to clean up though. There was a finding related to the inspection of the COPV's.

Pentagon Watchdog Cites Top U.S. Space Contractors for Quality-Control Lapses

 

[Cosmacelf]

Wouldn’t Inconel be both much heavier and possibly more expensive than carbon fiber overwrwp?

 

[Bobfitz1]

Wouldn’t Inconel be both much heavier and possibly more expensive than carbon fiber overwrwp?

Task Order from NASA to SpaceX for an “Inconel tank feasibility study..

Has it been confirmed this is a genuine Task Order from NASA? The idea of substituting inconel for carbon fiber in the largest structures in F9 seems ludicrous. Inconel's density is 8.5 g/cc, Different CF composites have slightly different densities, ranging from 1.4 - 2 g/cc.
So inconel is 4 to 5 times as dense as CF. But wait... has inconel EVER been used to construct a rocket fuel tank?

Given it's physical properties, strength, hardness, etc. could huge sheets of it (which aren't made to my knowledge) be formed into tanks with current means?

IMO, if this order is for real, someone in NASA has lost their mind and no one sane is supervising what they are doing.

 

[scaesare]

Task Order from NASA to SpaceX for an “Inconel tank feasibility study..

Has it been confirmed this is a genuine Task Order from NASA? The idea of substituting inconel for carbon fiber in the largest structures in F9 seems ludicrous. Inconel's density is 8.5 g/cc, Different CF composites have slightly different densities, ranging from 1.4 - 2 g/cc.
So inconel is 4 to 5 times as dense as CF. But wait... has inconel EVER been used to construct a rocket fuel tank?

Given it's physical properties, strength, hardness, etc. could huge sheets of it (which aren't made to my knowledge) be formed into tanks with current means?

IMO, if this order is for real, someone in NASA has lost their mind and no one sane is supervising what they are doing.

Firstly, I believe the CF tanks are the internals COPV's, and as such aren't the "largest" main tank structures, which I've seen video of them stir welding aluminum for.

Secondly those COPV tanks overwrap CF over an internal tank(hence their name)... which I believe is also aluminum. Hence a direct mass comparison to Inconel would have include the mass of the aluminum portion of the tank as well.

 

[mongo]

This seems sensible to me:

SpaceX had a failure attributed to solid oxygen formation in the carbon fiber overwrap.
NASA is saying, "hey SpaceX, here is 10 million space bucks, please spend 4 months to investigate:"

• would Inconel work for the tanks
• what would it cost time/ $$$ to develop new tanks
  
• what would it take to build a solid oxygen test stand to (my assumptions)
  • verify the root cause of previous RUD
  • verify the mitigation plan
  • evaluate Inconel susceptibility

Seems like a logical course of action, especially given the fuel loading with crew on board concern that NASA has.

 

[LargeHamCollider]

SpaceX COPVs are titanium wrapped in carbon, these are relatively small tanks but there are a lot of them, like more than a dozen. SpaceX manufactures them in house. Switching to inconel would add mass and require modification to a bunch of structural members.

 

[mongo]

SpaceX COPVs are titanium wrapped in carbon, these are relatively small tanks but there are a lot of them, like more than a dozen. SpaceX manufactures them in house. Switching to inconel would add mass and require modification to a bunch of structural members.

from SpaceX:

Each stage of Falcon 9 uses COPVs to store cold helium which is used to maintain tank pressure, and each COPV consists of an aluminum inner liner with a carbon overwrap.

OrbitalATK links to a paper (AIAA 2002-4349) discussing testing of titanium COPVs.

 

[Bobfitz1]

Firstly, I believe the CF tanks are the internals COPV's, and as such aren't the "largest" main tank structures, which I've seen video of them stir welding aluminum for.

Secondly those COPV tanks overwrap CF over an internal tank(hence their name)... which I believe is also aluminum. Hence a direct mass comparison to Inconel would have include the mass of the aluminum portion of the tank as well.

Thanks @scaesare. I missed that the tank in question is the much much smaller COPV tanks.
If solid oxygen can form around the COPV it can ignite and we know what happens next. Is the idea that an inconel tank would be so much stronger than aluminum, no outside overwrap would be required at all, thus the chance of solid oxygen forming is much, much less?

 

[ggr]

Thanks @scaesare. I missed that the tank in question is the much much smaller COPV tanks.
If solid oxygen can form around the COPV it can ignite and we know what happens next. Is the idea that an inconel tank would be so much stronger than aluminum, no outside overwrap would be required at all, thus the chance of solid oxygen forming is much, much less?

The F9 has no "tanks" for the fuel, the outer skin of the rocket is it. The problem with the solid oxygen forming was that it was between carbon fibre layers, and when compressed enough it auto-ignited. Not only is Inconel non-flammable at any reasonable temperature, but there won't be any layers of it, so there won't be any danger if some oxy-frost (I just made that up) forms on the outside.

 

[AudubonB]

A point to keep in mind with all this discussion of different materials' properties - just comparing densities is fruitless without also a comparison of the relevant strengths, coefficients of expansion and so forth.

 

[jkn]

Tank made of only inconel would be too heavy. Metal is needed to prevent helium leaking out through carbon fiber. Carbon fibers are needed for strength without too much mass. I don't see any need for replacing Al in helium tank. If material is touching LOX, inconel would be safe choice. Carbon is not. Solid O2 can ignite, if mixed with fuel (carbon). Could this be about inside of LOX tank of BFR?

Yes, coefficients of expansion of used metal and carbon fiber should mach.