Comment Re:Sterling Engine (Score 3, Informative) 98
While the efficiency of a heat engine is great, the power to weight ratio is awful. So much in fact that it is really hard to build one that can lift itself.
A laser that is matched to the bad gap of a pv cell can be over 50% efficient. So it is not too bad on that front and a lot less weight then a heat engine.
By the way, a Sterling Engine is an engine made of silver, a Stirling Engine is a heat engine.