[gurps] vehicle challenge

[Onno Meyer]

Hal wrote: 
> http://gas2.org/2008/11/23/michigan-students-set-world-record-for-longest-flight-by-fuel-cell-powered-plane/

GURPS Vehicles underestimates peak fuel consumption for internal combustion 
engines, see VXi23, to reach a workable average. VXi23 does not mention fuel
cells, so unlike ICE they use the listed values.

A fuel cell with hydrogen for 10 hours is 21.62 lbs. per kW at TL7 and 11.079 
lbs. per kW at TL8, for a total power below 5 kW. The fuel cell itself is much
heavier than the fuel. 

A flyer with 6 cf fuselage, 0.6 cf STOL wings, fair streamlining and 50 lbs. total 
weight would have a stall speed of 17.5 mph. 1 kW powering a 4-lb. ducted fan 
give an air speed of 40 mph. 

The main problem will be volume - hydrogen fuel is bulky, bulk means volume
means area means drag, to overcome drag more power is needed, which then
requires more fuel ...

Onno