http://www.damninteresting.com/?p=359

Interesting indeed, although I question the claim that the process can be done as many times as needed to get somewhere. There'd be losses in each cycle, so you'd go a little less high and a little less far each time.

heh... this wouldn't work at all.
In order for the GravityPlane to become airborne, gas bags inside a pair of rigid, zeppelin-like structures are filled with helium from storage tanks inside the vehicle. This causes the aircraft to become lighter-than-air, and it rises from the ground. Compressed-air jets on the sides of the craft add further propulsion, pushing the vehicle skyward and decreasing the craft's overall weight by releasing the stored air which acts as ballast.
Energy is required to gather helium in the first place. Energy is required to compress air. Air compression is a couple magnitudes less effective than gas in terms of energy spend and energy gained.
It uses a cycle of climbing and descending to maintain its lift and forward speed
As Lionlel stated, it would lose energy with each cycle

air turbines mounted on the top of the craft capture some of the forward momentum and use it to drive air pumps which can refill the on-board compressed air storage tanks
This part is just precious. :)
They use air turbines, which use the forward momentum to compress more air. The air is then used to lift the aircraft. If the air turbines worked 100% effectively and turned the momentum into potential energy (compressing the air), without losing any energy to friction or heat, then it would put an equal amount of the forward energy into raising the aircraft.

A couple stupid mistakes here;

1. There is no gain in overall energy as the article makes it out to be. You could just tilt the wings to change forward momentum into vertial momentum, and a lot more effectively too.

2. Energy IS lost due to friction, heat, and simply the imperfect effectiveness of the compressor. Theoretically if there was no energy lost, a glider filled with helium would fly just as far as this thing would.

I'm going to write to the author on this one.

I see quite a few problems with this theory.
The very first being the weight of the helium cylinder(combined with the compressors) containing the required cubic ft of lift.

I think you could accomplish the same thing more effectively by using a balloon to lift a glider into the air. Without the weight of the gas bags and associated equipment and the drag of the turbines you'd glide a lot farther.

You know it's stupid when they even look like idiots
http://www.damninteresting.net/content/hunt_aviation.jpg

I used to think that the more stupid they looked, the smarter they were, I mean look at Einstein. He looked pretty retarded. Ben Franklin looked like he was the kid who didn't have a date for prom and Bill Gates... well his picture speaks for him.
http://blogzinet.free.fr/images/tsr-afp-bill-gates-ie.jpg

I think there's a difference between looking like a lunatic and a complete idiot.
Anyways. We're still waiting for a feasible alternative.
http://img314.imageshack.us/img314/4558/tsrafpbillgatesie9aq.jpg (http://imageshack.us)

Explorer isn't all that bad. Well... actually. I take that back, but at least it was good when it came out.

Im a hardcore Firefox fan now :)