Yes yes, we know hydrogen is flammable and stuff. However I think there'd be nothing wrong with a weather balloon that used the hydrogen keeping it aloft to power fuel cell and give it a controlled descent.
After all, helium prices are expected to rise.-- Madai, Apr 29 2013 my original blather......... Your_20own_20Vulcan_20bomber [not_morrison_rm, May 01 2013] [+] Helium is an unreplaceable commodity on Earth so I don't see why we're using it up in the first place.
Anyways brilliant idea. I think Honda's FC tech has fuel cell weight down to 1lb/kW, so added to an EM (also'ish at 1hp/lb) the weight is equivalent to an IC engine of the same power, at 2-3x's the efficiency; plus better weight distribution.-- FlyingToaster, Apr 29 2013 Er, I have bored everyone already with hydrogen balloon/fuel cell, but I was blathering on about BiefeldBrown drive, as it's the lightest.-- not_morrison_rm, Apr 29 2013 random, halfbakery