Author Topic: Use of Helium  (Read 16471 times)

Offline Jet Black

Use of Helium
« on: 08/27/2014 09:55 am »
Why is helium used to provide pressure in rockets? Why not some other inert noble gas? It seems to be pretty problematic at the best of times.
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Online Jarnis

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Re: Use of Helium
« Reply #1 on: 08/27/2014 10:04 am »
Lightweight.

Inert.

Offline R7

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Re: Use of Helium
« Reply #2 on: 08/27/2014 10:07 am »
and the very low boiling point.
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Offline Jim

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Re: Use of Helium
« Reply #3 on: 08/27/2014 01:15 pm »
Why is helium used to provide pressure in rockets? Why not some other inert noble gas? It seems to be pretty problematic at the best of times.

Just because Spacex has problems doesn't mean it is problematic for others.

Doesn't condense when in contact with LH2. 
I believe not as soluble as other gases in storable propellants.
« Last Edit: 08/27/2014 01:16 pm by Jim »

Offline Rocket Science

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Re: Use of Helium
« Reply #4 on: 08/27/2014 01:43 pm »
Helium has the smallest atomic radius so the “little buggers” are able to get through materials and past some seals. It’s a diatom at anything but STP. If SpaceX has the continued “similar” problems they just need to track down the source, be it seal material, un-estimated contraction, manufacturing or installation procedures etc....
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Online woods170

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Re: Use of Helium
« Reply #5 on: 08/27/2014 01:46 pm »
Why is helium used to provide pressure in rockets? Why not some other inert noble gas? It seems to be pretty problematic at the best of times.

Just because Spacex has problems doesn't mean it is problematic for others.

Doesn't condense when in contact with LH2. 
I believe not as soluble as other gases in storable propellants.

Don't pretend Spacex is/was the only one with helium trouble.
Delta's and Atlas' have had their fair share of helium trouble as well, even on models that had been flying for quite some time.
« Last Edit: 08/27/2014 01:51 pm by woods170 »

Offline Jim

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Re: Use of Helium
« Reply #6 on: 08/27/2014 01:50 pm »

Delta's and Atlas' have had their fair share of helium trouble as well.

when?

Online woods170

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Re: Use of Helium
« Reply #7 on: 08/27/2014 01:52 pm »

Delta's and Atlas' have had their fair share of helium trouble as well.

when?
1980's, 1990's.

Offline cambrianera

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Re: Use of Helium
« Reply #8 on: 08/27/2014 02:14 pm »
He has also negative Joule Thompson coeff. at low temperatures, i.e. it heats expanding.
Cooling during expansion poses various kind of risks (materials temp. range, clogging, etc).
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Offline Jim

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Re: Use of Helium
« Reply #9 on: 08/27/2014 02:23 pm »

Delta's and Atlas' have had their fair share of helium trouble as well.

when?
1980's, 1990's.

I would say even earlier.  There were only 17 Atlas Centaur launches in the 80's.  I don't recall any Delta issues.  Shuttle had hydrogen leaks in the 90's

Offline SWGlassPit

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Re: Use of Helium
« Reply #10 on: 08/27/2014 02:30 pm »
Why is helium used to provide pressure in rockets? Why not some other inert noble gas? It seems to be pretty problematic at the best of times.

Just because Spacex has problems doesn't mean it is problematic for others.

Doesn't condense when in contact with LH2. 
I believe not as soluble as other gases in storable propellants.

Not just that, helium is the only gas with a freezing point lower than hydrogen's boiling point.  If you are using LH2 in your rocket, your only two choices for ullage pressure and purge gas are GH2 and He.

Online woods170

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Re: Use of Helium
« Reply #11 on: 08/27/2014 02:37 pm »

Delta's and Atlas' have had their fair share of helium trouble as well.

when?
1980's, 1990's.

I would say even earlier.  There were only 17 Atlas Centaur launches in the 80's.  I don't recall any Delta issues.  Shuttle had hydrogen leaks in the 90's

And then it had a mini string of GUPC H2 leaks in the 2000's. Just goes to show that even with 25 years of flight experience leaks will eventually occur, particularly with small atoms/molecules such as hydrogen and helium. Your earlier post pointing out spacex as the one with helium trouble is a bit unfair given that the 'others' that don't have current helium problems have had them in the past however.

Offline Jim

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Re: Use of Helium
« Reply #12 on: 08/27/2014 02:44 pm »

And then it had a mini string of GUPC H2 leaks in the 2000's. Just goes to show that even with 25 years of flight experience leaks will eventually occur, particularly with small atoms/molecules such as hydrogen and helium. Your earlier post pointing out spacex as the one with helium trouble is a bit unfair given that the 'others' that don't have current helium problems have had them in the past however.

My point was that Spacex doesn't reflect upon the whole industry.   Spacex problems are not industry problems.  The other vehicles learned their lessons long ago.   I would also categorize H2 separately from He.   

Offline Jet Black

Re: Use of Helium
« Reply #13 on: 08/27/2014 04:08 pm »
I didn't mean to imply the problems were unsolvable or still needed to be solved by everybody, but mainly why helium is used given the issues that it has (which need to be engineered around). There is also the issue that helium supply is particularly finite, and I also wonder what people will do when it runs out.

nice replies by the way! thanks.
« Last Edit: 08/27/2014 04:09 pm by Jet Black »
For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled. -- Richard Feynman

Offline Damon Hill

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Re: Use of Helium
« Reply #14 on: 08/27/2014 04:24 pm »
I didn't mean to imply the problems were unsolvable or still needed to be solved by everybody, but mainly why helium is used given the issues that it has (which need to be engineered around). There is also the issue that helium supply is particularly finite, and I also wonder what people will do when it runs out.

nice replies by the way! thanks.

Mandate the extraction from the better natural gas sources, as was done for quite a few decades when helium was deemed a strategic material.  Long shot: the 'waste' of p-B11 aneutronic fusion is helium.  Really, really long shot: atmospheric mining of gas giant planets (will that really ever be practical?).

If there's money to be made supplying it, some smart someone will figure out a way.  Might be expensive, though.

Might be moot if SpaceX goes to methane--autogenous pressurization.  I think Shuttle did this with both hydrogen and oxygen.  Just need heat exhangers.
« Last Edit: 08/27/2014 04:31 pm by Damon Hill »

Offline Jim

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Re: Use of Helium
« Reply #15 on: 08/27/2014 04:34 pm »

I think Shuttle did this with both hydrogen and oxygen.  Just need heat exhangers.

Still need it as a purge gas and initial pressurization.
« Last Edit: 08/27/2014 04:34 pm by Jim »

Offline Jim

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Re: Use of Helium
« Reply #16 on: 08/27/2014 04:35 pm »
I didn't mean to imply the problems were unsolvable or still needed to be solved by everybody, but mainly why helium is used given the issues that it has (which need to be engineered around).

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Online MP99

Re: Use of Helium
« Reply #17 on: 08/27/2014 04:38 pm »


Why is helium used to provide pressure in rockets? Why not some other inert noble gas? It seems to be pretty problematic at the best of times.

Just because Spacex has problems doesn't mean it is problematic for others.

Doesn't condense when in contact with LH2. 
I believe not as soluble as other gases in storable propellants.

Not just that, helium is the only gas with a freezing point lower than hydrogen's boiling point.  If you are using LH2 in your rocket, your only two choices for ullage pressure and purge gas are GH2 and He.

"Only other..."?

You've obviously covered the point with your second sentence, but H2 obviously has a freezing point below H2's boiling point.
Shuttle used autogenous pressurisation (just boil H2 & O2 and feed it back into the tank).

I was surprised when someone told me that even for the H2 this had a higher mass penalty than if it had used He. (In fact, I wonder if I may have mis-remebered that.)

Cheers, Martin

Online MP99

Re: Use of Helium
« Reply #18 on: 08/27/2014 04:40 pm »


Helium has the smallest atomic radius so the “little buggers” are able to get through materials and past some seals. It’s a diatom at anything but STP. If SpaceX has the continued “similar” problems they just need to track down the source, be it seal material, un-estimated contraction, manufacturing or installation procedures etc....

Just to be clear, are you saying it changes to a molecule? Presumably this is at low temperature & high pressure?

Cheers, Martin

Online MechE31

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Re: Use of Helium
« Reply #19 on: 08/27/2014 04:58 pm »
What makes you think the the failure modes that caused the helium leaks wouldn't be present if another gas were used?

While helium is a smaller molecule and is more prone to leaks, generally speaking, small leaks may be accepted, large leaks cannot. A large leak with helium will most likely (although not always) result in a large leak of nitrogen.

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