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Can helium be mixed with hydrogen to form a non-explosive mix? (2003)

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Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)

#71

Post by m4rtink »

jodrellblank wrote: post #47
ravenstine wrote: post #31

Earlier quoted context omitted.

How 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.

Airship Hindenburg had 200,000 cubic meters of lift gas[1]. Air masses 1.2 Kg per cubic meter, so 240,000Kg of air in that volume normally. Helium masses 0.18Kg per cubic meter[2], so replacing that volume with Helium gets it down to 36,000Kg. Hydrogen masses 0.08Kg per cubic meter[2], so replacing that volume with Hydrogen gets it down to 16,000Kg. Huge balloons containing almost-nothing, as soon as you replace the…

It would still have some compressible strength, right ? While not really being crushed under its own weight by default.

So couldn't you build, say a giant pyramid reaching out into the stratosphere using hydrogwn infused aerogel ? :)

Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)

#72

Post by m4rtink »

giantg2 wrote: post #5

Hydrogen is non-explosive. If you prevent oxygen from mixing in, then it's also not going to rapidly deflagrate.

Still apparently hydrogen fires in daylight are basically invisible (the produce mostly infrared radiation). NASA engineers used to walk with a broom in front of them so as not to accidentally walk into a thousand+ degree invisible fire when testing hydrogen equipment.

Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)

#73

Post by freemint »

goohle wrote: post #59
nousermane wrote: post #51

Earlier quoted context omitted.

This. Also, even if aerogel tech improves drastically, there is another, more insidious problem. Small-molecule gases diffuse through solid matter (search for "helium leak iphone" if you haven't read that fascinating story), so hydrogen will be slowly leaking out of aerogel, much like it does leak from a normal balloon. Air diffuse back inside at a much, much slower rate - with net effect that pressure inside drops.…

But we just need a thick but lightweight shell, which is hard to puncture, not a whole volume made with aerogel.

You are aware that aerogel is porpous?

Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)

#74

Post by dTal »

goohle wrote: post #59
nousermane wrote: post #51

Earlier quoted context omitted.

This. Also, even if aerogel tech improves drastically, there is another, more insidious problem. Small-molecule gases diffuse through solid matter (search for "helium leak iphone" if you haven't read that fascinating story), so hydrogen will be slowly leaking out of aerogel, much like it does leak from a normal balloon. Air diffuse back inside at a much, much slower rate - with net effect that pressure inside drops.…

But we just need a thick but lightweight shell, which is hard to puncture, not a whole volume made with aerogel.

Indeed. Popular materials for this "envelope" are nylon fabric or mylar =)

Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)

#75

Post by ncmncm »

trutannus wrote: post #67
ncmncm wrote: post #48

Earlier quoted context omitted.

What leads you to think that anything would "pull oxygen into the fuel"? H2 under pressure moves outward, and in a containment breach tends to, instead, increase the H2 fraction above the 75% that can sustain a flame until most of the gas has escaped and leapt skyward. H2 explosions are a concern in enclosed, unventilated spaces.

> H2 explosions are a concern in enclosed, unventilated spaces Well, ignoring one of the largest hydrogen explosions in History which occurred in the open air under the exact circumstances you say are impossible: https://en.wikipedia.org/wiki/Hindenburg_disaster . You mention earlier that this is not the hydrogen, and instead just the fabric. That's been debunked repeatedly: https://www.airships.net/hindenburg/disast…

You are contradicting statements I did not make.

The Hindenberg disaster, in fact, involved no exploding hydrogen. It was a big fire. Fire can be very destructive. There is no need to invent imaginary explosions to explain destruction from fire.

It is a fact that fewer than half who were aboard died. Those who did die obviously could have been burned, and, despite your absurd and repeated accusation, I never claimed otherwise. Nobody who was not aboard died.

Burning hydrogen moves upward the same as non-burning hydrogen. Gas in contact with flame does not magically become non-buoyant.

We are not, in fact, discussing "hydrogen cars", so whatever "sealed environment" you picture in them is wholly irrelevant.

Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)

#76

Post by trutannus »

ncmncm wrote: post #75
trutannus wrote: post #67

Earlier quoted context omitted.

> H2 explosions are a concern in enclosed, unventilated spaces Well, ignoring one of the largest hydrogen explosions in History which occurred in the open air under the exact circumstances you say are impossible: https://en.wikipedia.org/wiki/Hindenburg_disaster . You mention earlier that this is not the hydrogen, and instead just the fabric. That's been debunked repeatedly: https://www.airships.net/hindenburg/disast…

You are contradicting statements I did not make. The Hindenberg disaster, in fact, involved no exploding hydrogen. It was a big fire. Fire can be very destructive. There is no need to invent imaginary explosions to explain destruction from fire. It is a fact that fewer than half who were aboard died. Those who did die obviously could have been burned, and, despite your absurd and repeated accusation, I never claimed…

You didn't make the points here, you made them elsewhere.

> Burning hydrogen moves upward the same as non-burning hydrogen. Gas in contact with flame does not magically become non-buoyant.

Correct, it burns. Like it did in the Hindenburg. I have no idea what your point is.

> We are not, in fact, discussing "hydrogen cars", so whatever "sealed environment" you picture in them is wholly irrelevant.

This is a counter-argument for your previous points that leaks are irrelevant. My point is simple: No, they're not. You're trying to side-step this point by saying "well, I'm not talking about that" when you did right here:

> H2 under pressure moves outward, and in a containment breach tends to, instead, increase the H2 fraction above the 75% that can sustain a flame until most of the gas has escaped and leapt skyward.

Which is complete nonsense if you look into what's around a containment system. Which is my point -- containment is never not in a confined environment. You talk about some positive airflow system, sure, that's fine. What if the failure affects that? Well now you have to consider the risks all over again.

> involved no exploding hydrogen

This is a pedantic nitpick. In day to day usage, people say explosion to mean "rapid, uncontrolled fire". That does not negate my point -- that was one of the largest hydrogen fires in history.

You sound like you have tunnel vision on the advantages of hydrogen for industrial uses. There's a reason we don't use it. It's dangerous, and engineering solutions to mitigate the danger are prone to failure. If you want more: https://www.airships.net/hydrogen-airship-accidents/

Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)

#78

Post by ncmncm »

trutannus wrote: post #76
ncmncm wrote: post #75

Earlier quoted context omitted.

You are contradicting statements I did not make. The Hindenberg disaster, in fact, involved no exploding hydrogen. It was a big fire. Fire can be very destructive. There is no need to invent imaginary explosions to explain destruction from fire. It is a fact that fewer than half who were aboard died. Those who did die obviously could have been burned, and, despite your absurd and repeated accusation, I never claimed…

You didn't make the points here, you made them elsewhere. > Burning hydrogen moves upward the same as non-burning hydrogen. Gas in contact with flame does not magically become non-buoyant. Correct, it burns. Like it did in the Hindenburg. I have no idea what your point is. > We are not, in fact, discussing "hydrogen cars", so whatever "sealed environment" you picture in them is wholly irrelevant. This is a counter-ar…

Talking about "pedantic nitpicking" does not favor your argument. Inventing claims from whole-cloth to debunk does not favor your argument.

The world uses literally millions of tons of hydrogen every year, industrially. That the only event of any note that you can get any traction with was over 80 years ago should give you a clue. Noisy scaremongering does not improve anybody's life. Give it a rest.

Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)

#79

Post by trutannus »

ncmncm wrote: post #78
trutannus wrote: post #76

Earlier quoted context omitted.

You didn't make the points here, you made them elsewhere. > Burning hydrogen moves upward the same as non-burning hydrogen. Gas in contact with flame does not magically become non-buoyant. Correct, it burns. Like it did in the Hindenburg. I have no idea what your point is. > We are not, in fact, discussing "hydrogen cars", so whatever "sealed environment" you picture in them is wholly irrelevant. This is a counter-ar…

Talking about "pedantic nitpicking" does not favor your argument. Inventing claims from whole-cloth to debunk does not favor your argument. The world uses literally millions of tons of hydrogen every year, industrially. That the only event of any note that you can get any traction with was over 80 years ago should give you a clue. Noisy scaremongering does not improve anybody's life. Give it a rest.

You've given me a good laugh here. It's clear to pretty much anyone what I mean about industrial uses, so you're just responding to what you mistake as pedantry with pedantry. Anyway, I won't spend any more time here. Have fun, you've picked a strange hill to die on.

Re: Can helium be mixed with hydrogen to form a non-explosive mix? (2003)

#80

Post by lmilcin »

Stoichiometric 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).

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