I was reading some various things lately when the topic of vehicles powered by the wind has been brought up as a subject of discussion in the news.
Basically these vehicles can go any direction (up-wind, down wind, etc) as long as there's a difference in speed between
wind and ground or
wind and water.
Getting the principle down to the basics, all these vehicles use the idea that a difference in velocity exists between two media which the vehicle is
in contact with. So if a fluid-solid (air-ground) version works and a fluid-fluid (air-water) works, then there shouldn't be anything keeping yet
another fluid-fluid (air-air) version from working.
The concept isn't that hard once you get the gist of it. Applying what is known already, it should be possible to propel an aircraft kept across a
wind-shear by nothing more than the wind-shear itself. Now before ruling it out as too difficult, consider that I was thinking along the lines of a
glider pulled along in the lower atmosphere by tractor kites somewhere in the jet-stream. (The kite counts as a part of the aircraft btw.) As long as
you can keep the tractor kite "hooked" and given that the velocity difference in air masses is large enough, your flight endurance could be
indefinite. (I also don't see why you couldn't do a variation utilizing electric motors on the main aircraft and a generator carrying gyro-kite
sending power down the line. That seems like an easier solution for going up-wind without requiring too crazy a flight profile and stress on the tow
line.)
Now imagine this principle applied to a military UAV. Initially it would get up to high altitude on battery or engine power. Then it deploys the
tractor kite and does shear gliding. Now you recharge your batteries with solar, and as long as you keep shear gliding all the energy resources can go
to the onboard packages instead of propulsion. That means you could optimize payload without dedicating the majority to fuel or batteries.
Of course if the principle is simple enough in execution, it creates the military implication that practically any country could produce a drone
aircraft capable of around the world reach. (You no longer need the most efficient engine or fancy batteries, and guidance and automation are already
cheap.) Which makes me wonder what countermeasures may exist.
I've heard of no manned flights using this principle yet. I think it would also make for an interesting and unusual around the world manned flight
challenge. Balloons and normal powered flight have all been done before, and I believe this one would be more interesting as it takes a bit more skill
to pull off.
Oh, and I just found this:
oai.dtic.mil...
There really might be something to the idea since it's not that new. The difference is that now have the technology (cheap computers and control
systems) to seriously consider exploiting it.
