quote: Diesel engines are higher torque than gasoline engines. So, for the same horsepower a gasoline engine will have higher RPMs, and would make a plane faster than if it used diesel. Hence why diesel engines are rarer for aircraft (though used more on airships, which are lumbering and slow, with a lot of mass that needs to be moved).
quote: Also, if you look just above in this thread you see our talk about Rutan; the only known plan to go over four days. But it was also very specially constructed and one of a kind (and very weak, it could not even weather storms). This UAV is far more standard in design despite its "bomb" shape, and to be mass produced. Can't really compare it to Rutan. Design has a critically important role as you point out, but the engines and fuel are -all part of the design-. Otherwise, why don't we design all our craft like Rutan to have 9 day longevity? Think about it a little more.