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Timeline for Balloons and lifting gases

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Jul 31, 2014 at 12:53 comment added Floris If you use a closed loop (heat exchanger) system, there is no reason why you could not warm your hydrogen with a propane burner - as long as there is no oxygen in the hydrogen. If there were some low concentration of oxygen, it would soon react, leaving water and pure hydrogen. Not saying it'd be a great idea (the marginal gain is small because it's already so light and it's not without danger), but it is certainly feasible. Really hot hydrogen is used industrially (for example hydrogen firing of Xray targets to drive off carbon contamination) - you just have to be careful of leaks and oxygen.
Oct 16, 2011 at 20:05 vote accept Jonathan.
Dec 15, 2010 at 16:41 comment added Frédéric Grosshans @Noldorin: Just read the following paragraph on wikipedia to have the story of hydrogen vs helium in the Hindenburg: en.wikipedia.org/wiki/…
Dec 15, 2010 at 16:39 comment added Frédéric Grosshans @Noldorin: It was not a mistake*by scientist/engineers, it was a deliberate action by US gov. forbidding the sell of helium to Nazi Germany. The German engineers wanted to use helium but they could not. To make things clear: I am not accusing the US of any wrongdoing here, because the potential military use of airships at that time was clear, and the belligerent nature of Nazi Germany was obviously to be taken into account. I just want to say that the reason for the lack of helium in the Hindenburg is not because the danger was unknown/neglected by engineers, but because geopolitics of the 30s
Dec 15, 2010 at 0:13 comment added Noldorin Sure, but it was still a horrendous mistake by the scientists/engineers!
Dec 15, 2010 at 0:04 comment added dmckee --- ex-moderator kitten @Noldorin: While I have no numbers, you could--for instance--look at the number of people who traveled across the Atlantic Ocean safely in Dirigibles and compare their risk inclusive of the Hindenburg disaster with that they would have faced on the ships of the time. Risk is always relative, and perfect safety is an illusion. Opportunity costs are everywhere. 35 people died on the Hindenburg (about of third of those on board); compare to en.wikipedia.org/wiki/….
Dec 14, 2010 at 13:42 comment added Noldorin @Frédéric: Sure it was a mistake! It killed many people in a horrible disaster? How can you call it anything else!
Dec 14, 2010 at 11:44 comment added Frédéric Grosshans @Noldorin : the use of hydrogen in the Hindenburg was not a mistake. Helium, mined in the US, was basically too strategic to be sold to Nazi Germany at that time, because of potential military use of airships...
Dec 14, 2010 at 0:10 comment added Noldorin Worth pointing out regarding hydrogen is that it was the gas used initially. Unfortunately people underestimated the danger of its volatility. The German designers made this unfortunate mistake in the 1930s that resulted in the Hindenburg disaster.
Dec 13, 2010 at 23:57 comment added dmckee --- ex-moderator kitten @Marek: Er...well, I'm not an expert in this business. But...$\rho = \rho(T,P)$ and $P = P(h)$, $T_{atm} = T_{atm}(h)$ where $P$ is pressure, $T$ is temperature and $h$ is height. Those functional relationships may be complicated. In a large balloon I suppose that $\rho$ may vary over the volume necessitating a integration over V. As for control: heat the gas and it expands (i.e. gets less dense), or vent some and V drop proportionately, so you can adjust the lift in either direction.
Dec 13, 2010 at 23:41 comment added Marek Is this really all there is to balloons' physics? I mean, I don't know anything about this stuff, but I think people are able to adjust the buoyant force by warming the gas or letting it out. So how does pressure and temperature fall into this picture? Also atmosphere's density is not constant with height, right? I guess that must also play some role. I'd be glad if you could elaborate on these topics.
Dec 13, 2010 at 22:30 history answered dmckee --- ex-moderator kitten CC BY-SA 2.5