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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)

#101

Post by Gravityloss »

thechao wrote: post #84
jrexilius wrote: post #10

It 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

I tried to convince a group that: 1. Hot air balloons get their lift from hot air; and, 2. Dirigibles can get their lift from hydrogen; thus, 3. Hot hydrogen dirigible? Blah blah blah ... exploding dirigibles ... blah blah blah. The lifting efficiency is outrageous .

Even if you used weightless atoms to fill your balloon, the lift is only the weight of the air it displaces. So you don't really get much better since hydrogen already weighs so little.

Air is about 30 grams per mole and hydrogen is two grams per mole. So going entirely weightless you could go from 28 grams of lift per mole to 30 grams of lift per mole, a 7% increase.

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

#102

Post by Gravityloss »

jiggawatts wrote: post #96
JumpCrisscross wrote: post #81

Earlier quoted context omitted.

How much would a mile-wide geodesic sphere cost to build?

That’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.

You 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.

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

#103

Post by goohle »

dTal wrote: post #74
goohle wrote: post #59

Earlier quoted context omitted.

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 =)

Never heard about 10cm thick mylar or nylon fabric envelope.

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

#104

Post by beervirus »

bernulli wrote: post #63
beervirus wrote: post #19

Earlier quoted context omitted.

Diatomic hydrogen is bigger than helium, less prone to diffusing through a membrane.

Have 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.

That’s true, but it isn’t a claim I made.

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

#105

Post by bernulli »

beervirus wrote: post #104
bernulli wrote: post #63

Earlier quoted context omitted.

Have 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.

That’s true, but it isn’t a claim I made.

No, 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!

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

#106

Post by m4rtink »

jodrellblank wrote: post #87
m4rtink wrote: post #71

Earlier quoted context omitted.

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 ? :)

You could build a giant space pyramid out of anything in principle, according to Isaac Arthur on YouTube[1]. The limiting factor quickly becomes the size of "giant" needed for most materials and the limited size of Earth to have a wide enough base. Maybe being Hydrogen-infused would mean less pressure on the lower levels and able to build it higher. Really though, doesn't AeroGel work by being mostly nothing? The mor…

Yeah, in principle you could make the whole thing inflatable as well, with some compartmentalization here and there to avoid catastrophic single point failure.

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

#107

Post by beervirus »

bernulli wrote: post #105
beervirus wrote: post #104

Earlier quoted context omitted.

That’s true, but it isn’t a claim I made.

No, 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!

The comment you replied to was mine though…

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

#108

Post by thechao »

Gravityloss wrote: post #101
thechao wrote: post #84

Earlier quoted context omitted.

I tried to convince a group that: 1. Hot air balloons get their lift from hot air; and, 2. Dirigibles can get their lift from hydrogen; thus, 3. Hot hydrogen dirigible? Blah blah blah ... exploding dirigibles ... blah blah blah. The lifting efficiency is outrageous .

Even if you used weightless atoms to fill your balloon, the lift is only the weight of the air it displaces. So you don't really get much better since hydrogen already weighs so little. Air is about 30 grams per mole and hydrogen is two grams per mole. So going entirely weightless you could go from 28 grams of lift per mole to 30 grams of lift per mole, a 7% increase.

But 100% more firing a flamethrower into your hydrogen filled envelope while looking your customers in the eye.

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

#109

Post by jodrellblank »

Hypx_ wrote: post #83
jodrellblank wrote: post #47

Earlier quoted context omitted.

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…

You have to be careful with the calculation here: The airship must also include the weight of the structure, and aerographene could potentially need much less structure than giant gas balloons.

I don't know how strong AeroGraphene might be, but is it a reasonable approximation to say that these are like a sponge and the way they get less dense is to have more larger voids and less solid matter; that is, the lighter they are, the weaker they are?

AeroGel.org says: "Aerogels can usually hold a gently applied load of up to 2,000 times their weight and sometimes more. But since aerogels are so low in density, it doesn’t take much force to achieve a pressure concentration equivalent to 2,000 times the material’s weight at a given point. The amount of pressure required to crush most aerogels with your fingers is about what it would take to crush a piece of Cap’n Crunch® cereal." - https://www.aerogel.org/?p=3 (it goes on to say Aerogels differ in strength, but most can be made stronger by making them denser and heavier).

I have seen a suggestion, probably in a HN submission, that remaking classic Zeppelin design but replacing the duralumin structure, metal tensioning wires, coated cloth outer shell, and animal guts lift bags with modern carbon fibre, kevlar, and foils could knock 80-90% off their mass. What is all the structure in a Zeppelin doing, why can't they be shaped like hot-air balloons?

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

#110

Post by ncmncm »

trutannus wrote: post #79
ncmncm wrote: post #78

Earlier quoted context omitted.

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.

Not fooling any of us.
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