Reminds me of Moller and his flying car.[1] Moller has been announcing a flying car Real Soon Now since 1974.[2] It still doesn't work, although he's spent lots of money over four decades, and been in trouble with the SEC. This may be a record for the longest running scam. It's outlived Madoff and the Keely Motor.
Technically, the problem is that Moller is trying to do it with Wankel engines, rather than jet turbines. He has some very high power to weight Wankel engines, and at least briefly, he's been able to get the thing a few meters off the ground. But the Wankels can't maintain that power level for long. Jet turbines can, but they cost too much.
(Want a hard problem to work on? Build a small, cheap, reliable jet engine. Many people have tried. Willams got the furthest.[3] The general result is that, below 6-passenger bizjet size, smaller jet engines don't get much cheaper. Small jet engines have been built, but the price doesn't come down much if you want the reliability and life of an aircraft engine.)
The challenge is [small, cheap, reliable, not deafeningly loud, possible to hook an axle to]. Pulse jets win at the first three, and utterly fail at the last two.
Technically, the problem is that Moller is trying to do it with Wankel engines, rather than jet turbines. He has some very high power to weight Wankel engines, and at least briefly, he's been able to get the thing a few meters off the ground. But the Wankels can't maintain that power level for long. Jet turbines can, but they cost too much.
(Want a hard problem to work on? Build a small, cheap, reliable jet engine. Many people have tried. Willams got the furthest.[3] The general result is that, below 6-passenger bizjet size, smaller jet engines don't get much cheaper. Small jet engines have been built, but the price doesn't come down much if you want the reliability and life of an aircraft engine.)
[1] http://www.moller.com [2] http://www.downside.com/scams/moller/ [3] http://www.williams-int.com/