Hacker News Reader

Comment by lukev | Hacker News Reader

Can we set helium supply aside, though?

I really hope we can make airships work, but it seems like the volumes of helium required will be prohibitive for wide-scale deployment.

Hydrogen works well but remains dangerous... perhaps modern tech can make it "safe enough"?

View on HN

Hydrogen is "safe enough" if we want to use it, compared to gasoline and other routine hazards.

The Hindenburg provided a recognizable meme but even with that, there were things that could have been done differently (with technology of the time) to make even those disasters more survivable.

With modern materials, it could be quite safe, indeed.

> The Hindenburg provided a recognizable meme but even with that, there were things that could have been done differently (with technology of the time) to make even those disasters more survivable.

It’s also worth noting that 64% of the crew and passengers survived. I’m not sure how that compares to the average plane crash, but it was certainly not as severe a disaster as it’s usually thought of.

Maybe also worth noting that it was close to the ground, which it would not be in normal operation.

> I’m not sure how that compares to the average plane crash

Average plane crash survival rate is about 95%. I'm guessing it's a somewhat bimodal distribution, however.

> It’s also worth noting that 64% of the crew and passengers survived. I’m not sure how that compares to the average plane crash, but it was certainly not as severe a disaster as it’s usually thought of.

64% survival would be great for VC investments (depending on the returns); it would be awful for a round of layoffs; for human lives on transportation infrastructure ... maybe we are losing sight of a big picture here! :)

> Hydrogen is "safe enough" if we want to use it, compared to gasoline

While I'm inclined to agree with your overall point, intuitively, it seems much more dangerous than gasoline. Gasoline is very difficult to ignite unless if it's vaporized. On the other hand, hydrogen is already a gas so it's significantly easier to ignite and more explosive when it does.

It's easier to light, but it's pretty non-explosive if not mixed with air: https://www.youtube.com/shorts/_RKdWYqgu3Y (mixing with air is a problem).

The big advantage (and what could be designed for) is that hydrogen goes up and so (by default) the flammable stuff escapes.

It only ignites in the presence of oxygen and a source of ignition so as long as you keep those things away from the hydrogen it should be quite safe. It's a solvable engineering problem. Use only materials that cannot burn for the gas envelope and structures immediately adjacent to it. Locate the engines as far out as possible on pylons. Divide the gas envelope as much as possible to limit the fuel supply for any fire that does start. The major complication is not adding too much weight but there's no reason airships couldn't be as safe as airplanes.

> It's a solvable engineering problem.

While that might be true, it's been said before. I'd be interested in an engineering study about the costs and risks.

hopefully the goal of modern technology would be "don't catch fire" more than "survive the fireballs!"

1. Don't burn.

2. If you must burn, do it politely.

I thought that the Hindenburg was more about the materials the airship skin was made of than the Hydrogen itself. If the skin hadn't caught fire, the hydrogen wouldn't have. Also the fuel tanks caught fire, and they could have been better protected. Normally the hydrogen can only catch fire if it leaks out and there is an ignition source near the leak.

Even if this happens, if the skin is flame retardant, the hole probably won't grow very fast. You will lose buoyancy, but you'll probably have time to make an emergency soft-ish landing. Helium wouldn't really make any difference because it can leak out and cause loss of buoyancy just as easily.

Realistically, all the other fundamental problems of blimps will limit before the helium supply does — remember that it was artificially crippled by the selloff of the US's strategic helium reserve; it was sold under market value and so all the natural gas producers who could have trapped and sold off their helium production just gave up on doing so. Supply will stabilize again after the last of the reserve is sold off this month.

Hydrogen fusion creates helium as a byproduct. But I don't see why they can't use hydrogen for cargo. We have the tech to make it safer than long haul driving.

This is a pet peeve of mine when people talk about the advantages of fusion, if you did all of the US power budget with DT fusion that would generate very close to 10 million moles of helium, or 4E7 grams of helium, or 2E8 liters at stp. This is a big number! but it's 2E5 cubic meters and annual US consumption of helium is 40E6 cubic meters, less than 1% of consumption.

I found the last sentence confusing

If you produced all the USA's electricity in a year with fusion and collected all the resulting helium with 100% efficiency, you'd have collected less than 1% of the amount of helium we go through in that year.

A naive translation (not checking facts in any way):

Converting 100% of power generation in the US to (deuterium-tritium) fusion would result in 200,000 cubic meters of helium generated per year. But the US currently consumes 40,000,000 cubic meters per year.

Simplified: If you magically switched every power plant in the USA to fusion, they would make about 200,000 cubic meters of helium per year.

But the USA currently consumes 40,000,000 cubic meters of helium per year.

The helium-3 market makes an interesting comparison: it's sole-sourced from nuclear fission reactors.

https://cen.acs.org/materials/3-availability-increase-new-su... ("³He availability to increase with new supply deal")

It'd cost $30 billion to fill one of OP's blimps with synthetic helium-3 (which—to be fair—is a superior lifting gas to helium-4).

Reply on news.ycombinator.com