I’ve heard that the Hindenburg disaster was caused because the US has all the world’s helium and refused to sell it to Hitler’s Germany, fearing he would use it for spy balloons. So they had to use hydrogen.
I’m not sure that makes any sense, because hydrogen is available everywhere and nobody cares if a spy balloon should catch fire once in a while.
But, since helium is heavier than hydrogen, wouldn’t it have required even larger airships, and exhausted the amount then being produced?
Could the US of the day provided enough helium for a fleet of those airships?
Helium provides about 93% of the lift provided by hydrogen, so the difference isn’t that significant, and probably worth making the sacrifice for the added safety.
(hydrogen - molecular weight 2 (forms H2 molecules, remember), helium molecular weight 4. The molecular weight of the atmosphere is approximately 29. Using the perfect gas law, their densities are proportional to their molecular weights. (25/29)/(27/29) = 0.926, which agrees with that 93% figure you can find quoted several places)
The question is of the abundance of helium. Wikipedia says that modern helium production in 2005 totaled 160 million cubic meters. The volume of the Hindenburg seems to be about 200,000 cubic meters. At least today, there’s enough helium to go around to fill a rather large fleet of zeppelins. However, I don’t know how much helium was available back in WW2 – probably much less.
In fact, we are beginning to face a global helium shortage because there are an increasing number of industrial uses for it. Prices have been rising steadily, and your party balloons now cost more than they used to.
I’d WAG that US supplies were not particularly tight in the 1930s, since use of natural gas was already widespread, and helium was captured as a byproduct of gas wells. There were simply political reasons for not giving any to Germany.
One thing about helium is that you can almost say it’s a self-replenishing resource, although I don’t know how fast that happens compared to the amount we extract. IIRC the gas is formed from alpha particles given off by various radioactive elements in the earth’s crust, and when the alpha particle manages to pick up a couple of electrons to neutralize its 2+ charge, it has become a helium atom.
We are also losing helium to space from the atmosphere. Some of the helium released from radioactive decay goes into replenishing that.
I don’t think the replenishment rate is significant. From webelements, uranium occurs in the Earth’s crustal rocks in the amount of 1800 ppb by weight. Thorium occurs in the amount of 6000 ppb. The amounts of other radioactive elements are probably not significant. For U238 (which is almost all of the naturally occurring uranium), we are talking about a 4.46 * 10^9 year half life. For Th232, a half life of 1.4 * 10^10 years. Both are alpha emitters. Even allowing release of 5 alpha particles from the uranium, and 4 from the thorium on the grounds that their decay products have shorter half lives, generally decaying comparatively rapidly to lead, I don’t think that represents all that much created helium in comparison to the quantities in our reserves.
Attempting to obtain figures for helium generation tends to lead you into a morass of “young Earth” creationist arguments. If you don’t believe helium escapes from the atmosphere, you can then argue that there isn’t 4 billion years worth of helium in it.
Well, strictly speaking the US didn’t refuse, because Germany didn’t ask for it. However the US almost certainly would have turned them down, and Germany knew it, which is why they didn’t even try to buy Helium from us.
The Hindenburg was initially designed with the intention of using helium, and they only switched to hydrogen when they realized that they couldn’t count on getting the helium. However, it’s not like they were building a vast armada of airships, they only had one other operating airship, the Graf Zeppelin. So they wouldn’t have come close to using the world’s helium supply had they been using it.
Because of the decision to use hydrogen, they were able to take advantage of the extra lifting capacity and added some additional passenger cabins. The original design had 25 two berth cabins, and they added nine more two berth cabins and one four berth family cabin.
Also, it was hardly unusual for them to be using hydrogen. Germany had built more than one hundred airships since 1900, all of them using hydrogen for lift. The Graf Zeppelin flew for nearly a decade, flew more than a million miles and made 144 ocean crossings with a perfect passenger safety record.
Which, to put things into perspective, compared very favourably indeed with the commercial flying boats of the time. Wikipedia’s article on the Short Empire-class flying boat doesn’t list how many of them crashed in service, but I know from a magazine article that a number of them did. Also, they carried only 19 passengers each, so I shouldn’t wonder if the airships came out some way ahead on passenger-miles per crash.
Footnote: The Wikipedia article on the Hindenburg makes reference to the loss of an American dirigible, though helium-filled, and with a much greater loss of life. Barely a third of passengers and crew perished on the Hindenburg, and some of these by jumping from the airship - those who rode it down mostly survived.
At current production rates <1000 hindenburgs a year? Helium is now in high demand and supply has trouble keeping up?
Wow, it sounds like the answer to the question might be ‘no.’ They really might have had logistical problems filling up a fleet of airships, especially a commercial fleet. Good thing airplanes came along, haha. I wonder if the helium manufacturers were placing big bets that never made good, especially in the wake of the Hindenburg?
Actually, by that time Helium was being controlled, and stored, by the Federal gov’t as a strategic reserve. It was being reserved, among other things, for the US Navy’s own fleet of rigid hulled airships, and later for ASW blimps both for convoy duty and shore stations. So, even had Germany asked to purchase enough helium to supply thier airships - the US had military reasons, not just political ones, to keep the supply themselves.
On preview: Malacandra, I suspect that the wiki article is talking about the loss of the USS Akron. She went down off the Jersey coast, and as a weight saving measure had no personal floatation devices. So, between the cold waters, and the lack of floatation devices, most of the survivors were lost before rescuers could reach the wreck. When the USS Macon crashed two years later, in nearly identical conditions off the California coast, there were only a few men lost - because the Navy had figured out that if they’re running these airships over water it might be a good idea to have PFDs aboard.
It sounds like the article you’re referencing is making a comparison about relative dangers that just isn’t valid. The huge loss of life with the Akron was a result of poor planning, the loss of life with the Hindenberg was a result of having to compromise on the lifting gas. Put the Hindenberg’s ignition over water - and the loss of life there would have been much greater.
ETA: For those that might be interested - the wreck of the USS Macon was recently located within a nature reserve off the California coast. There are some pretty cool pics and information available via this site.
Yes, OtakuLoki. The point was that it’s perfectly possible to survive a hydrogen-airship crash - most of the Hindenburg’s victims did not burn - and there were worse disasters, in terms of loss of life, than this one. Granted that hydrogen presents an added danger over helium, the wreck of the Hindenburg was not necessarily a rational reason for giving up on hydrogen-filled airships.
True enough. The problem is that for all the general safety record of the German passenger airship lines, there had been a lot of spectacular failures with rigid hulled airships, even before the Hindenberg loss. The loss of the R-101, the loss of four of the five US Navy dirigibles, and the loss of the Airship Italia all had put rigid hulled airships into the into poor favor with the public, even before the Hindenberg’s loss. The UK had gotten out of the production and use of rigid hulled airships shortly after the crash of the R-101, and the US shortly after the loss of the USS Macon.
The Hindenberg is one of the first disasters to have been almost completely recorded by modern media. I’m not sure that it’s possible to over-estimate that effect: It was vivid, immediate, and shocking. But having it happen to a technology that was, rightly or wrongly, already being considered as “iffy” did a lot to magnify the perceived risk. The modern person, when they think of airships will usually think only of the Hindenberg. But to the people of 1937, the Hindenberg was the latest, and most spectacular, of the losses that dirigibles had suffered in the public eye over the previous ten years.
For a more modern comparison - the Concorde SST had a flawless passenger safety record, while other reasons to ground the fleet: environmental, economic, and mechanical, were all mounting. Once that perfect safety record was tarnished by the crash of just one of those planes, the other reasons for grounding the fleet were no longer being counter-balanced by a perfect safety record. And so the fleet was grounded, and never flew again for regular passenger service.
