Hasn't technology advanced sufficiently since the R101 and Hindenburg era to allow safe usage of hydrogen with it's greater lifting power?
Don't think so.
Furthermore, it's not only a question of safety. The need to refill, at least partially refill the gasbags with helium or hydrogen before each takeoff is a big drawback.
In regard to the helium problem: the only airship proposals I can take seriously are ones which don't require helium to be dumped in order to descend and land.
There have been proposals -- Russian, I think-- for airships that would chill and compress their helium to descend, so as to -reuse the helium.
Also, Lockheed and others have mooted hybrid large aircraft/airships which would not dump any helium and would remain somewhat heavier than air even when empty of cargo.
The “hybrid” principle utilizes both aerodynamics and lighter-than-air technology to generate lift - about 60% of the lift is aerostatic (from helium buoyancy) and the remaining 40% is aerodynamic, generated from the vehicle’s shape.
Make that about 65%-70% aerodynamic lift and 30%-35% aerostatic, and the proposal might be viable.
Last edited by Modern Elmo; 10th Sep 2011 at 15:44.