Frank van der Hulst wrote:
wrote:
And hydrogen is a lightweight fuel too, for lower fuel load.
But suppose you want some extra juice sometimes, for more
maneuvering/lifting power.
Hydrogen is only a lightweight fuel in its uncompressed, gaseous form.
In fact, in terms of energy per Kg, hydrogen is not a good fuel. Storing
hydrogen in sufficient density to be useful requires strong (read heavy)
tanks.
Unless you are driving an anti-static engineered lifting body shaped
dirigible, in which case, compressing or decompressing a little of
the surplus fuel / bouyancy medium using a "bouyancy bladder" device
allows ascent and descent without actual fuel expenditure, except
that required to compress the gas when descending. Quite the
inverse of a normal flying vehicle, where energy is expended to ascend.
Has anybody analyzed that in terms of fuel efficincy?
Terry K