schroder said:
Thank you for your response, which is correct. Now can you please explain how a cart which is powered (through wheels and drive belt and propeller) running on a treadmill, can possibly reverse direction and move against the movement of the tread?
schroder, I appreciate the frank exchange and I'll do my honest best but I fear that this explanation won't be any more productive than the others. Forgive my lack of ability to explain it.
In as simple as terms as I know: When it comes to the treadmill as compared the aircraft, you're forgetting that in the former there are two operating mediums moving relative to each other (air and a solid surface). In your 'glide copter' example, there is only one medium and that is still air.
Where two objects are moving relative to each other, there is energy to be extracted and utilized. This principle is well established -- rivers move and we extract energy, wind blows and we extract energy, even something as simple as a bicycle tire moving past the fork provided the opportunity to mount a headlight generator .
The copter only has it's own kinetic/potential energy upon which to capitalize. The cart on the treadmill (and sailboat and ice-boat and land yacht and wind turbine, and, and, ...) has the opportunity to extract energy from the motion of the two relative surfaces and use it however it sees fit.
In the case of the wind turbine, the energy extracted from the wind/tower interface is used to power the grid. In the case of the cart, it uses the energy extracted from the treadmill/air interface to move itself forward on the belt -- useless I know, but still entertaining since folks say it can't be done.
That's my best. I'll answer any question you wish regarding the above as best I can.
Thanks for listening schroder.
JB