Comment on 'Windmill': China tests world’s first megawatt-level airship to capture high winds
5too@lemmy.world 3 days agoAlso for unmanned aircraft, using helium instead of hydrogen is just crazy
Is it? Hydrogen is about half the mass of helium, but the trick is what you’re displacing to generate lift.
1 cubic meter of air is around 1.2 kilograms, depending on a variety of factors.
1 cubic meter of helium is around 0.18 kilograms, displacing the atmosphere to generate about 1.02 kilograms of lift.
1 cubic meter of hydrogen is around 0.08 kilograms, displacing the atmosphere to generate about 1.12 kilograms of lift, a shade under a 10% increase over helium.
That can be significant, depending on other engineering constraints; but is it “crazy” different?
(Numbers will vary with temperature and pressure, back of envelope calculations, etc. etc.)
0.18 to 0.08 is a gigantic difference, less than half the weight per cubic meter of displacement !!
Not only is cost an issue, but the larger the volume of displaced air, the bigger the dirigible, the harder it becomes to move through the atmosphere, more friction, more air resistance etc…
Fair points, I hadn’t considered the economic side of it; or even the mass beyond how it affects lift.
humanspiral@lemmy.ca 3 days ago
H2 being 10% more lift while 500% cheaper still makes it the choice. A H2 economy is the path to 100% renewable energy, with a transportable fuel that in a fuel cell is also much more efficient than combustion engines/turbines. Lifting gas, chemicals, agriculture, rocket fuel, all of the existing uses for H2 is just icing on the cake.
5too@lemmy.world 1 day ago
True, I hadn’t considered the economic angle at all!