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Can helium be mixed with hydrogen to form a non-explosive mix? (2003)
- 015a 5y agoITS NON-FLAMMABLE HELIUM https://www.youtube.com/watch?v=KsjQZ2eXTxE https://www.youtube.com/watch?v=KsjQZ2eXTxE
- daniel-cussen 5y agoReal economies are made by saving even 8.5% of the cost of an airship's gas. That's real money. Plus, that hydrogen won't escape the vessel over time, so that's a percentage you don't have to keep refilling.
- jonnycomputer 5y agoIts about your customer's perceptions of risk. Key line: "Are the cost savings by using a 8.5% mixture of hydrogen worth all the trouble and effort it will take to convince your customers that the mixture is safe, as opposed to avoiding the safety questions altogether by using 100% helium?"
- bernulli 5y agoWhy would the hydrogen not escape?
- beervirus 5y agoDiatomic hydrogen is bigger than helium, less prone to diffusing through a membrane.
- Sporktacular 5y agoLeading to an increasing percentage of hydrogen that will exceed the danger threshold. Helium level will need to be monitored and replenished.
- Dylan16807 5y agoYou have to monitor and replenish no matter what. That's part of why the comment said "a percentage" you don't have to refill.
- bernulli 5y agoHave you worked with hydrogen? Being less prone to leaving than He is an extremely low bar and very far away from the claim that it doesn’t ever diffuse through anything.
- IntrepidWorm 5y agoDiffusion works both ways, too. Oxygen outside of the membrane will also slowly diffuse into the hydrogen and helium mix, further complicating any attmpts to remain non-combustible.
- bernulli 5y agoSure. And none of this prevents hydrogen from escaping.
- beervirus 5y agoThat’s true, but it isn’t a claim I made.
- bernulli 5y agoNo, but the post I replied to, and apparently you felt the urge to reply to my comment. But I now understand that you did not intend to contribute to the discussion, thanks for the clarification!
- beervirus 5y agoHelium diffusion is a good point though. If you’re right at the edge of non-flammability and you lose some helium over time…
- h0l0cube 5y agoThis 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-gas/ https://www.thecgo.org/benchmark/bring-back-hydrogen-lifting...
- ncmncm 5y agoThis is the winning strategy. There is no need for crew on cargo craft.
- nwah1 5y agoBut they are still flying bombs, even without crew.
- ncmncm 5y agoExcept, they are not flying bombs. Notably, the only people killed when the Hindenberg blew were on board. And, fewer than half of them. The flames in the film were the (very flammable!) gas bag itself and the kerosene fuel. The escaping gas went up and away. A modern craft would not be made of readily flammable material.
- trutannus 5y agoYour comments are filled with misinformation: The gas-bag and paint theory is debunked: https://www.airships.net/hindenburg-paint/ https://www.airships.net/hindenburg-paint/ The "nobody died from the hydrogen" line is debunked: https://www.airships.net/hindenburg/disaster/myths/#advocates https://www.airships.net/hindenburg/disaster/myths/#advocate... That the craft is made out of flammable material is debunked: https://www.airships.net/hindenburg/disaster/myths/#flammable-cover https://www.airships.net/hindenburg/disaster/myths/#flammabl...
- Dylan16807 5y ago> The "nobody died from the hydrogen" line is debunked I don't see that claim in the comments you're replying to.
- deleted 5y ago[deleted]
- egberts1 5y agoLet us ignore the Helium shortage.
- ravenstine 5y agoAlthough it's a resource we should avoid using as much as possible, since it's difficult to renew, the crisis is somewhat averted. https://phys.org/news/2021-10-helium-south-africa-gold.html https://phys.org/news/2021-10-helium-south-africa-gold.html https://us.eitidc.com/new-helium-reserve-discovered/ https://us.eitidc.com/new-helium-reserve-discovered/ It seems the situation isn't nearly as bad as was purported back when the helium crisis was the hot new story.
- dr_dshiv 5y agoThis 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.
- dr_dshiv 5y agoCool, here is a kind of balloon that combines hot air and helium. https://en.wikipedia.org/wiki/Rozi%C3%A8re_balloon https://en.wikipedia.org/wiki/Rozi%C3%A8re_balloon
- FlyMoreRockets 5y agoIt has been one before. https://en.wikipedia.org/wiki/Rozi%C3%A8re_balloon https://en.wikipedia.org/wiki/Rozi%C3%A8re_balloon
- aaron695 5y agoThe original question was wrong, airships have never used this mixture. You will get a ~8% reduction of cost, but you get other large costs like dealing with hydrogen onsite and dealing with contaminated helium. How does that re-compress? How do you make sure your mixture stays at the right percentage. What is the purpose here? Venting helium is expensive, but venting hydrogen is not. You can't do this with a mix but you could vent hydrogen if it's in separate internal bags. That's a possible use, but again you'd need to look at total costs. Read up properly here for this mixing idea, but there seems little purpose - Flammability limits of hydrogen-diluent mixtures in air https://prism.ucalgary.ca/bitstream/handle/11023/164/ucalgary_2012_terpstra_mark.pdf https://prism.ucalgary.ca/bitstream/handle/11023/164/ucalgar... (2012) "Hydrogen-helium mixtures fail to propagate a flame at 92% helium in the fuel mixture under atmospheric pressure (Calgary, 89k Pa) and ambient temperature. Therefore, only a small percentage of the helium in dirigibles can be safely offset with hydrogen. This is in agreement with previously reported data. The lean flammability limits of hydrogen binary mixtures with argon, carbon dioxide, and nitrogen diluents in air for upward flame propagation appear to be very close to the limits predicted using the adiabatic flame temperature concept"
- gremloni 5y agoI did t read the article. Are hydrogen and helium miscible or do they separate out. I definitely think they would because of the difference in density.
- eesmith 5y agoKey line: "Are the cost savings by using a 8.5% mixture of hydrogen worth all the trouble and effort it will take to convince your customers that the mixture is safe, as opposed to avoiding the safety questions altogether by using 100% helium?"
- jonnycomputer 5y agoI guess that might depend on the cost of Helium.
- KMnO4 5y agoI understand the author poses this as a rhetorical question, but obviously the answer is more complicated than “just use 100% helium”. It’s much more likely that someone has already done the cost and risk analysis and determined that 8.5% hydrogen is worth the trouble. Sorry it’s not the answer [the author] is looking for.
- Kelteseth 5y agoInteresting! Living in Friedrichshafen (Germany) the birthplace of the Zeppelin, I'm wondering if this would be a valid option, because the Zeppelin NT that is used here in the summer uses only Helium AFAIK. The Zeppelin NT has an emergency drain that would essentially mean releasing 7.400 m³ worth of helium. I will definitely ask a family member that works at Zeppelin what he thinks of this research!
- rendall 5y agoAwesome! Could you do us HN readers a favor and tell us here what he says?
- Kelteseth 5y agoSo I had a brief conversation with Arthur Brauchle (Head of electrics and avionics)and we talked about some problems with the idea: - Laws: You are currently not allowed to use anything besides pure helium - Osmosis: Natural separation would occur, so you would need to make sure to mix helium and hydrogen constantly. - Cleaning: They have to constantly monitoring the humidity of the helium and have to remove it with a specialized machine on a humid day. This would not work with a mixed gas (with the current design). - (Speculation) Do not mix it in the first place: Create a sealed off hydrogen balloon in a helium balloon. This would have other problem like different expansion based on temperature. The devil is in the details here...
- b112 5y agoThus began the squeakiest death cries of all caught in the horror.
- giantg2 5y agoHydrogen is non-explosive. If you prevent oxygen from mixing in, then it's also not going to rapidly deflagrate.
- trutannus 5y agoIt'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.
- treeman79 5y agoHad my house once fill up with natural gas for many weeks. Much to the surprise of the gas company it did not explode. Of course everyone has severe long term effects from that.
- ncmncm 5y agoOxygen 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.
- FlyMoreRockets 5y agoAs noted, the lower explosive limit for hydrogen in air is 4%. Significantly lower with pure oxygen. https://www.safeopedia.com/definition/2205/explosive-flammable-limits https://www.safeopedia.com/definition/2205/explosive-flammab... The problem is that hydrogen is a very small molecule and readily escapes containment. It can even travel along grain boundaries through solid metal.
- ncmncm 5y agoExactly, the lower limit, when hydrogen has escaped into the air, not when air has leaked into the contained hydrogen. The article makes clear that above 75% H2, ignition is impossible (but only if you read it). "Traveling along grain boundaries" can only leak trace amounts. With, as I said, positive airflow, trace leaks can be constantly diluted below the concentration where ignition is possible.
- jrexilius 5y agoIt 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 https://en.wikipedia.org/wiki/Lifting_gas
- ryandvm 5y agoTotally 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.
- zokier 5y agoNot just on Venus; Buckminister Fuller proposed to build floating cities on earth: https://en.wikipedia.org/wiki/Cloud_Nine_(sphere) https://en.wikipedia.org/wiki/Cloud_Nine_(sphere)
- JumpCrisscross 5y agoHow much would a mile-wide geodesic sphere cost to build?
- jiggawatts 5y agoThat’s an interesting What If? question! One cost-reduction approach would be that the beams could be mass-produced for efficiencies of scale. The top panels could be simply plastic sheeting.
- Gravityloss 5y agoYou could make it out of UHMWPE, the best current strength to weight material available. It's a plastic with density slightly under 1 kg/L. And it's UV resistant. Joining the parts is the real problem though. You could make it out of continuous thread in single piece with 3d knitting to avoid glue or fasteners. But all kinds of problems would arise. Also repairability would be bad. So probably you would use some sections and glue.
- rini17 5y agoAnyone thought about using aerogel infused by pure hydrogen, wrapped in plastic? In case the wrap is breached it should make mixing with air slow, preventing explosion. (I am aware that aerogel is absurdly expensive in needed quantity. Just a thought experiment.)
- dreamcompiler 5y agoOr you could skip the aerogel entirely and use a hard, incompressible shell and pull a partial vacuum inside. Of course we don't currently have any materials both strong and light enough to do that. Neal Stephenson proposed such vehicles made from thin shells of diamond in The Diamond Age.
- rini17 5y agoRight and when one shell breaks, the shrapnel breaks the other ones and everything around:)
- dreamcompiler 5y agoWell, they'd implode (the gas inside is at a partial vacuum) so most of the shrapnel would travel inward. But yeah, diamonds are hard but not tough. It's possible that a kid with a BB gun could shatter such a craft with one shot. But they'd certainly look cool.
- dTal 5y agoAerogel is too heavy. The resulting infusion will achieve neutral buoyancy at best.
- ravenstine 5y agoHow could hydrogen be a feasible approach to lifting any amount of cargo if aerogel of all things is too heavy? I just find it hard to believe that even the volume of aerogel required to support enough hydrogen to lift a useful amount of cargo would approach even a tiny fraction of the weight of the cargo itself, but perhaps I'm not imagining things correctly.
- iamthemonster 5y agoUntil 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.
- ivanbakel 5y ago>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.
- blippage 5y agoBut if you lower the temperature, the hydrogen increases in density. I haven't read the article, but I presume that the use of hydrogen is a non-starter. No-one wants a flaming fireball raining down on them.
- bryant 5y ago> I haven't read the article, lol. tl;dr (apropos in this case): "So, 8.5% hydrogen in helium appears to be non-flammable, whereas anything above 8.7% is flammable. Eight percent hydrogen really doesn't provide much in the way of cost savings. You probably ought to consider another question concerning your airship business. Are the cost savings by using a 8.5% mixture of hydrogen worth all the trouble and effort it will take to convince your customers that the mixture is safe, as opposed to avoiding the safety questions altogether by using 100% helium?" [implied: probably not] > but I presume that the use of hydrogen is a non-starter. No-one wants a flaming fireball raining down on them. it'll probably work just fine on coastal or oceanic automated shipping routes. And oceanic routes would slightly mitigate the risk of someone catastrophically holepunching one with a Class IV laser.
- Haga 5y agoCharge the hull, ionize the gas, minimize loss by forcefield. Needs current carrying hull though. Graphene?
- Pxtl 5y agoThat MSDS sheet saying 8.5% is, I assume, for pressurized hydrogen. I wonder if the non-pressurized lifting gas (roughly atmospheric pressure) would allow higher concentration with it still considered inert?
- lmilcin 5y agoStoichiometric mixture is only loosely connected to flamability. You can have a stoichiometric mixture that will not be flammable because both reagents would be in right proportions but very diluted in the inert gas. And a mixture that is very non-stoichiometric can still be very flammable, no problem. The extra gas most of the time performs the same role as inert gas -- dilutes the reagents and takes away energy from the reaction. There are exceptions, though, where you can have different results depending on the mix (for example your burning producing CO rather than CO2 because of abundance of carbon relative to oxygen in the mix).
- dandotway 5y agoHydrogen Embrittlement[1] is not discussed in the link, an effect where hydrogen diffuses into metals and causes them to become brittle and crack. Many aerospace materials are especially vulnerable: high strength steels, nickel and titanium alloys, etc. Fueling a disposable balloon or rocket with hydrogen is one thing, but a vehicle that can safely be refilled with hydrogen over and over for decades is quite another. (Recall how the rust red Space Shuttle External Tank was not recycled like the white SRBs were and was the only large expendable component each launch.) [1] https://en.wikipedia.org/wiki/Hydrogen_embrittlement https://en.wikipedia.org/wiki/Hydrogen_embrittlement