Evals wrote:

Forgive me for disagreeing in return. On a non soaring flight, sailplanes
are powered (mostly) by the internal combustion engine. Gravity just
reclaims the energy expended by the use of fossil fuels. Any gain in height
after launch is indeed "nuclear" powered.


Actually Bob K. had it right to begin with, even on a non-soaring flight.
Where do you think those fossil fuels came from? All life on Earth derives,
either directly or indirectly, sustenance from the Sun. Plants use
photosynthesis to convert the Sun's energy into food. Animals then eat the
plants or other animals that ate the plants. And so on.

Regards,

-Doug