Originally posted by zeeblebot
you're both right . i was thinking more of the materials tradeoff, like sonhouse.
The problem with solar flight is using solar energy just to stay in the air. A better system would be just using a helium dirigible paved with light PV panels and using that for propulsion only, not lift. It seems obvious to me a much more efficient use of solar energy, to say nothing of by design having a hundred times the surface area for energy collection. More lift power to have much more battery storage onboard to get through nightimes and storms, maybe even a tethered version to just collect energy to use on the ground. I can even see a system that uses H2 as a lift gas, for one thing it is more efficient then helium, much more readily available and if used as a tethered PV collection site, some of that energy can be used for electrolysis of water to regenerate H2 to make up for losses through the skin, something you cannot do with helium. If it is unmanned, who cares if the dam thing blows up other than the annoyance of replacement, no lives would be lost.
Another thought: How about a hybrid He/H2 system of lift, start out mostly with helium, then use hydrolysis or some catalyst system to generate H2 which would mix with the existing helium and slowly replace the helium with H2 which would greatly extend the useful life of the original helium without actually making new helium, the mixture would just go from 100% helium to 100% H2 over a period of years in unmanned flight. You could even have lightweight pumps on board to take out a portion of the gas, compress it in tanks to make the thing sink to the ground for maintenance.
I see I am not the only one to think of this, but I think I am the originator of the He/H2 hybrid idea:
The He/H2 idea would be much safer than pure H2 for manned flight because the mixture of He/H2 would never burn in the first place, making that technology a viable alternative to pure helium ships. Not sure what the minimum He needed to keep H2 from being explosive but whatever that limit is, you could then land for the purpose of refilling with He, which seems obvious to be a greatly reduced usage of precious helium for lifting bodies and as the mixture goes towards pure H2, the lifting power goes up so the cargo carrying capacity would go up also somewhat anyway.