[jodrellblank]

The Graf Zeppelin burnt Blaugas[1] because it's about the same density as air, so as the fuel tanks emptied the buoyancy didn't change. See [2] for other things the Zeppelins did, which says "The LZ 127 Graf Zeppelin had bi-fuel engines, and could use gasoline and Blau gas as a propellant. Twelve of the vessel's gas cells were filled with a propellant gas instead of lifting gas with a total volume of 30,000 cubic metres, enough for approximately 100 flight hours. The fuel tank had a gasoline volume of 67 flight hours. Using both gasoline and Blau gas, one could achieve 118 hours of cruise time."

That article mentions that the Zeppelins experimented with burning Hydrogen lift gas as fuel "without much success" but doesn't add detail.

[1] https://en.wikipedia.org/wiki/Blau_gas

[2] https://en.wikipedia.org/wiki/Buoyancy_compensator_(aviation...

[jordanb]

My understanding was blau-gass was unpressurized propane, which is a little more dense than air. But I guess according to that article it's slightly less.

I'd expect that, like a lot of problems zeppelins had in the 1920s, burning hydrogen would be more feasible with modern technology.

I'd also point out that the thing that made hydrogen dangerous in those airships was that the skin was two layers. The inner skin was the gas bags, which were very fragile, and then the rigid structure and the outer skin to protect the fragile bags. This was a problem because hydrogen could accumulate and mix with air between the inner and outer skins. The outer skin also was quite flammable. Nowadays, we can make materials that are both strong enough to serve as an outer skin and impervious enough to serve as a gas bag for lifting gas, so modern airships have only one skin and nowhere for the lifting gas to mix with air inside the structure.

[usrusr]

Uncompressed propane would have simply been called Propangas I think. That term had been established well enough in the second half of the century and while the Zeppelin-era was before that, I doubt that the term changed much.

But if you aim for a buoyancy-neutral fuel, you can just add hydrogen to the mix, as little or much as you need. That custom blend then would be precisely the thing you don't invent a creative name for but just use a color code ("the blue one").

[knowaveragejoe]

The way the cutaway images on their site look, the bouyant members would be nestled in the actual structure in large tanks.

https://www.shipbyairship.com/

[jordanb]

This actually makes me think these people are unserious. This is an obsolescent airship design. ZeppelinNT, Airlander 10, and Lockheed P-719 all use the semi-rigid design with integral gas bags.