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Aeroscraft shows off its giant airship

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Could you use hydrogen for permanent-installation balloons? (Score: 1)

by wootery@pipedot.org on 2015-10-13 15:02 (#QBMZ)

As I understand it, the high price of helium is one of the major issues with airships. Could you use (yes, flammable) hydrogen instead, especially for unmanned floating-installation type applications?

If you want to bounce radio signals off something a mile up in the sky, would a hydrogen-filled balloon do the job? The safety issue is surely not a big one if it's not designed to regularly land: a Hindenburg situation seems unlikely if it's neither carrying people nor intended to land.

Re: Could you use hydrogen for permanent-installation balloons? (Score: 1)

by evilviper@pipedot.org on 2015-10-13 18:14 (#QC9W)

Actually, natural gas is cheap, highly buoyant, and not as escape prone as helium or hydrogen... Still highly flammable, and could be used to run the engines as well.

Re: Could you use hydrogen for permanent-installation balloons? (Score: 3, Informative)

by fnj@pipedot.org on 2015-10-13 23:09 (#QD37)

If Hindenburg were filled with natural gas instead of hydrogen, she couldn't have lifted her empty weight off the ground with zero payload and fuel. The following figures are based on very favorable conditions for static lift. More realistic conditions (say 15-25 C, and just 300 m MSL initial cruise altitude) would lower them significantly

Gas capacity = 202 000 m^3
Air density at 0 C, 101 325 Pa = 1.292 kg/m^3
Hydrogen density at 0 C, 101 325 Pa = 0.090 kg/m^3
Hydrogen lift at 0 C, 101 325 Pa = 1.292 - 0.090 = 1.202 kg/m^3
Gross lift 100% filled with hydrogen = 202 000 x 1.202 = 242 800 kg
Methane density at 0 C, 101 325 Pa = 0.716 kg/m^3
Methane lift at 0 C, 101 325 Pa = 1.292 - 0.716 = 0.559 kg
Gross lift 100% filled with methane = 202 000 x 0.559 = 112 900 kg
Weight empty = 118 000 kg

If she had been designed from the ground up for methane, restressed for the lower weights, de-engined for a slower speed (less aerodynamic stress) and carrying fewer passengers, it probably would have been possible to get a ship capable of lifting perhaps (optimistically) 1/4 as much useful lift. Still-air range would have been around 2000 km instead of 12 000 km (usable range with reserves considerably less).

Moderation

Time Reason Points Voter
2015-10-14 15:34 Informative +1 evilviper@pipedot.org
2015-10-14 21:38 Informative +1 bryan@pipedot.org

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