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Buy Your Very Own Exoskeleton Flying Vehicle
dks writes "Yahoo! News is running a story about a personal flying machine originally developed for the military that straps on an individual's back and allows her to fly around for over two hours at a time. The prototype is now up for auction on eBay. The only catch--you have to agree not to operate the vehicle if you purchase it. Uh...yeah...I'm just buying it for display. Yeah, that's it."
The reason they are selling the proto-type is that it got tangled up in the tether during a test hop and crashed. Its damaged and they don't have the funds to fix it. The DOD/DARPA folks that were supporting the development declined to extend the deadline(s) for demonstration of the technology after the crash.
The whole story as told from the SoloTrek perspective is on their web site. http://www.solotrek.com/
The eBay article features a link to the company designing this stuff and they have a very cool concept for a two seater: duotrek. I WANT one of these. No more fucking parking problems, that is if the roof of my appartment is strong enough...
giel.y contains 2 shift/reduce conflicts
Ground effect does not apply to this type of aircraft.
For an airplane, "ground effect" is the term applied to the tendency of a wing to exhibit increased aerodynamic efficiency (basically more lift and less drag) when it's within roughly a half-wingspan of the ground. It's caused, at least in layman's terms, by a cushion of air forming beneath the wing and the ground, and by the reduction of a drag-inducing wingtip vortex.
This vehicle has no horizontal wing flying thru the air. So we can eliminate the obvious cushion of air.
Now, a helicopter demonstrates ground effect for the same basic reason as an airplane, within half a rotor-disc-diameter or so of the ground, and also because for a hovering vehicle, the downwash tends to bounce back up again to provide a additional cushion. Here's a primer on helo ground effect. As you can see, the ground effect is largely produced by the ground limiting development of a tip vortex.
Just for completeness, we can also address ground effect for a hovering jet, like the Harrier Jump Jet. In that case, the downwash bouncing up certainly provides a cushion, and the Harrier has strakes under the fuselage designed exclusively to capture that cushion of air and enhance it - kind of like a hovercraft. But for a hovering jet, you have an additional problem - the exhaust gases also tend to get reingested by the engine, lowering the engine efficiency. One of the most vexing problems for the Harrier, and also for the newer Joint Strike Fighter designs, is "hot gas reingestion". In fact, if you hover these aircraft pointing downwind, you can snuff out the engine due to lack of oxygen. (This issue is probably not a big problem for the high-bypass arrangement of the SoloTrek, where very little exhaust gas is produced.)
Now to address this vehicle. The lift is provided by ducted fans. Therefore there is no tip vortex, because the duct prevents one from forming. In fact, the duct itself provides the same effect as ground effect, by eliminating the efficiency loss due to the vortex. The only relevant part of the "ground effect" here is therefore the bouncing cushion of air. But the fans on this vehicle are mounted so high above the ground (about 7 feet), and the total thrust is so low, that a fairly minimal ground effect cushion can be developed. In fact, in the pictures on Ebay, at least one of the photos shows the thing high enough up (the fans are at least 12 feet off the ground) that any ground effect that might exist would be almost totally eliminated.
So it's extremely unlikely that this vehicle's performance would change significantly with climbing away from the ground.
--Brandon / Split Infinity Music