Saturn helium usage

[ka9q]

One thing that strikes me when I look at the Saturn launch vehicle designs is the enormous amount of helium they used for purging and pressurization, particularly of fuel tanks (gaseous oxygen seems to have been used for pressurizing the LOX tanks).

Besides its light weight, helium does have the unique property of remaining gaseous even at liquid hydrogen temperatures, allowing it to be stored in spheres inside the LH₂ tank in the S-IVB, for example.

But anybody who has tried to get helium lately for saturation diving, welding, filling balloons, etc, knows just how bloody scarce and expensive the stuff has become. This is not actually a big surprise since it's a limited, non-renewable resource (on human timescales, anyway) and we've been using the stuff pretty indiscriminately.

I suppose helium is still acceptable in smaller pressure-fed hypergolic engines on spacecraft, but using huge amounts in launch vehicles seems like a real sustainability problem. Does anybody know if modern space launch vehicles still use it to the degree that the Saturns did?

[Luke Pemberton]

One thing that strikes me when I look at the Saturn launch vehicle designs is the enormous amount of helium they used for purging and pressurization, particularly of fuel tanks (gaseous oxygen seems to have been used for pressurizing the LOX tanks).

Besides its light weight, helium does have the unique property of remaining gaseous even at liquid hydrogen temperatures, allowing it to be stored in spheres inside the LH₂ tank in the S-IVB, for example.

But anybody who has tried to get helium lately for saturation diving, welding, filling balloons, etc, knows just how bloody scarce and expensive the stuff has become. This is not actually a big surprise since it's a limited, non-renewable resource (on human timescales, anyway) and we've been using the stuff pretty indiscriminately.

I suppose helium is still acceptable in smaller pressure-fed hypergolic engines on spacecraft, but using huge amounts in launch vehicles seems like a real sustainability problem. Does anybody know if modern space launch vehicles still use it to the degree that the Saturns did?

I have to admit that I've never thought about this problem in the wider context of helium in science and engineering. I found an interesting BBC article that asks about the use of helium in party balloons.

[ka9q]

I'm familiar with the helium problem because I help mentor a local high school ham group that builds and flies payloads under weather balloons. We only use a few cubic meters of helium per flight, but even that has gotten hard to find and outrageously expensive -- on the order of hundreds of dollars.

So we're doing what many other groups are doing: we're switching to hydrogen. Everybody fears the stuff, but nobody can point to an actual accident to justify their fear. I did find a Youtube video of a university group deliberately igniting a hydrogen-filled weather balloon as a safety test. The results were actually rather underwhelming as the hydrogen rose above the balloon before burning in an orange-ish "whumph". The only likely hazard to people on the ground seemed to be the falling bits of flaming latex.

Seems to me that handling hydrogen is at least as safe as handling gasoline, probably more so as long as you work outdoors and take reasonable precautions. There's an inexhaustible supply, so switching to it does seem like an ethical imperative. And it's an even better lifting gas than helium.
 

[Glom]

It's only a quarter of the visible matter in the universe. It's like talking about hose pipe bans while Wiltshire is flooded.

[Allan F]

Yes, it is common in the universe, but hard to get hold of in our corner.

[ka9q]

Yes, it is common in the universe, but hard to get hold of in our corner.

Exactly. Just like hydrogen in its elemental state. If it were easy, our energy problems would be over.

[Glom]

What bad luck.

[ka9q]

What bad luck.

We're actually lucky that hydrogen is so reactive, and that virtually all of it on earth is chemically combined in some way. Otherwise it would be as scarce as helium. Or more, since I don't know of any nuclear decay processes that produce it.

[Obviousman]

It has been suggested that shortly helium will be vastly more expensive, due to the dwindling supply. The remaining supplies will be dedicated to scientific and strategic uses.

Helium balloons and the accompanying "Mickey Mouse" voices may very soon be a thing of the past..

[Luke Pemberton]

Helium balloons and the accompanying "Mickey Mouse" voices may very soon be a thing of the past..

In years to come we will show our grandchildren YouTube videos of people on helium and say 'in my day we did that at parties.'

[Glom]

There is only one option. We need to seriously start making fusion happen. For the sake of children parties.

[cjameshuff]

It has been suggested that shortly helium will be vastly more expensive, due to the dwindling supply. The remaining supplies will be dedicated to scientific and strategic uses.

Helium balloons and the accompanying "Mickey Mouse" voices may very soon be a thing of the past..

Hydrogen would work even better for the squeaky voices, if you're okay with the possibility of exploding.

[Allan F]

Smoking and hydrogen usage is not recommended.

[ka9q]

Hydrogen would work even better for the squeaky voices, if you're okay with the possibility of exploding.

Correct.

Interestingly enough, breathing mixtures of hydrogen and oxygen are sometimes used in very deep diving. It's actually safe because the high pressure allows the oxygen percentage to be below the flammability limit (about 4%, IIRC) while still providing a sufficient ppO₂ for breathing. In fact there's an important physiological reason to keep the O₂ percentage down at high pressures: too much oxygen is quite toxic.

At shallower depths the O₂ fraction would have to be higher, making the mixture quite explosive. So the more familiar helium/oxygen mixtures must be used instead.

[Chew]

Google's Project Loon is sucking up the helium.

Their balloons have transponders on them so they show up on Flightradar24 as screencapped below. Google launched 10 balloons in mid-Dec, 7 from New Zealand and 3 from California. The California launches traversed across the entire contiguous US. One flew 5 miles north of my house. I stuck my iPhone camera up to my binoculars to get a pick (second pic link below). Google assigns them callsigns starting with "HBAL". In Flightradar24 you can add that as a callsign filter so the website will only display Project Loon balloons (if they are in flight). They sometimes generate UFO reports.

Project Loon - Wikipedia, the free encyclopedia

http://www.flightradar24.com/-0.85,-109.3/2

http://i.imgur.com/7E9toHO.jpg

http://i.imgur.com/wtJnX4h.jpg