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.
Quote from: Jet Black on 08/27/2014 09:55 amWhy 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.
Delta's and Atlas' have had their fair share of helium trouble as well.
Quote from: woods170 on 08/27/2014 01:46 pmDelta's and Atlas' have had their fair share of helium trouble as well.when?
Quote from: Jim on 08/27/2014 01:50 pmQuote from: woods170 on 08/27/2014 01:46 pmDelta's and Atlas' have had their fair share of helium trouble as well.when?1980's, 1990's.
Quote from: woods170 on 08/27/2014 01:52 pmQuote from: Jim on 08/27/2014 01:50 pmQuote from: woods170 on 08/27/2014 01:46 pmDelta'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.
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.
I think Shuttle did this with both hydrogen and oxygen. Just need heat exhangers.
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).
Quote from: Jim on 08/27/2014 01:15 pmQuote from: Jet Black on 08/27/2014 09:55 amWhy 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.
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....