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Can helium be mixed with hydrogen to form a non-explosive mix? (2003)
21–30 of 119 posts
Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)
#22It got me wondering if the increase lift capacity would be added factor, but quick calculation shows that it would only gain an extra ~1% of lift. So it would really just be a cost question: https://en.wikipedia.org/wiki/Lifting_gas
Totally unrelated, but a fascinating tidbit from that wikipedia link: > Venus has a CO2 atmosphere. Because CO2 is about 50% denser than Earth air, ordinary Earth air could be a lifting gas on Venus. This has led to proposals for a human habitat that would float in the atmosphere of Venus at an altitude where both the pressure and the temperature are Earth-like.
Not just on Venus; Buckminister Fuller proposed to build floating cities on earth:
Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)
#23Until I got to the last line I assumed this was about safer transmission of hydrogen, not lift gas. Of course it would be uneconomic for pipelines to have 91.5% inert carrier gas but I wonder if you could use an inert refrigerant gas to make "non-flammable hydrogen mix" within piping that runs to consumers through non-zone-rated or even residential areas, and then refrigerate the gas at point of use, to leave a pure hydrogen stream? The refrigerant would just go around in a mostly-closed loop.
Incidentally, using 8.5% hydrogen as lift gas will make a gnat's fart of difference; the lift force is proportional to the difference in density between air and lift gas - both helium and hydrogen are way less dense than air.
Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)
#24Hydrogen is non-explosive. If you prevent oxygen from mixing in, then it's also not going to rapidly deflagrate.
It's not random detonation that is the problem, the issue is containment failures, or anything that causes one. A collision, or stress fracture for example will allow oxygen into the tank. In an atmosphere with enough oxygen in it like ours, that's always a risk.
Oxygen leaking in is not an explosion risk. As noted, it takes 25% O / 75% H before it can ignite. Above 75% H it cannot.
With positive airflow around possible leaks, sufficient H2 to sustain a flame can be prevented. In a collision, gas released goes up and out of trouble.
Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)
#25This article popped up on HN a few months ago advocating 100% hydrogen airships for 'crew-less' cargo shipping https://www.thecgo.org/benchmark/bring-back-hydrogen-lifting...
This is the winning strategy. There is no need for crew on cargo craft.
Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)
#26Earlier quoted context omitted.
It's not random detonation that is the problem, the issue is containment failures, or anything that causes one. A collision, or stress fracture for example will allow oxygen into the tank. In an atmosphere with enough oxygen in it like ours, that's always a risk.
Oxygen leaking in is not an explosion risk. As noted, it takes 25% O / 75% H before it can ignite. Above 75% H it cannot. With positive airflow around possible leaks, sufficient H2 to sustain a flame can be prevented. In a collision, gas released goes up and out of trouble.
> In a collision, gas released goes up and out of trouble
Except for the cases when there's an open flame nearby or sufficient heat, as is the case in a non-insignificant number of collisions. What if a hydrogen engine collides with a standard petrol engine? Or if the gas becomes exposed to hot surfaces during the oxygen mixing? The gas expansion is also a major cause of explosion. You essentially pull oxygen into the fuel, and rapid fuel-air mixing is a known cause of detonation.
Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)
#27This is making me curious about hot air balloons combined with hydrogen/helium. I don’t know whether the heat would affect the balloon lift in a meaningful way, but would be nice to have control.
Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)
#28Let us ignore the Helium shortage.
Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)
#29This is making me curious about hot air balloons combined with hydrogen/helium. I don’t know whether the heat would affect the balloon lift in a meaningful way, but would be nice to have control.
Cool, here is a kind of balloon that combines hot air and helium.
Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)
#30Until I got to the last line I assumed this was about safer transmission of hydrogen, not lift gas. Of course it would be uneconomic for pipelines to have 91.5% inert carrier gas but I wonder if you could use an inert refrigerant gas to make "non-flammable hydrogen mix" within piping that runs to consumers through non-zone-rated or even residential areas, and then refrigerate the gas at point of use, to leave a pure…
>Incidentally, using 8.5% hydrogen as lift gas will make a gnat's fart of difference; the lift force is proportional to the difference in density between air and lift gas - both helium and hydrogen are way less dense than air.
My understanding is that the intention is not to create a mixture with better lift, but which is cheaper - helium being significantly more expensive than hydrogen due to supply issues.
What few sources I can find online for elemental prices suggest helium is anywhere from 2x to 10x more expensive than hydrogen, by weight. Even an 8% substitution would be economically significant at those prices - although, as the submission says, you may lose those margins through the bad reputation of hydrogen as a lifting gas.