Sagita Displays Hot Air Powered Helicopter

rcastro0 writes "Gizmag reports on the Sherpa, an interesting helicopter design at this year's Paris Air Show. As the article explains 'Rather than driving the rotors directly, the Sherpa's engine instead powers a compressor with an air intake at the rear of the helicopter.' There's no tail rotor. This approach is supposed to be more efficient, more reliable and more affordable than the traditional. A one-fifth scale model was shown to fly. Sagita, the 2008 startup behind the project, has yet to build a full scale prototype. They plan to sell a Sherpa two-seater for around US$ 200k in 3 years."

Something isn't adding up...

[wagnerrp]

According to the article, the air is compressed, then heated by the engine's cooling system, then mixed with exhaust gasses, and the resultant flow into the turbine is only 100C? Something doesn't seem right here. That temperature difference implies such a low boost that it won't even operate effectively as a supercharger, much less provide anything like enough power to those turbines. There's a reason gasoline engines with worthwhile turbochargers and superchargers all have intercoolers, and that's because compressing air makes it really damn hot.

Re:this word power seems to have been lost

[Anonymous Coward]

I research and teach physics, and even I think you're being kind of stupid here. Yes, that is a stab at the physics definition of power, but it should be pretty obvious to anyone with some basic understanding of English that there is a non-jargon meaning to the word, and usually it is quite clear from context which is meant. Many words have more than one meaning, get used to it, unless equivocation is a hobby of yours.

Re:What are they up to?

[modecx]

As far as I can see, their innovation can be accurately summed up thus:

They've decoupled the power turbine (the one which provides power to the rotors via a gears and such) from the engine, and mix cooler air into the exhaust stream. They've done away with the transmission and drive train by forcing this much cooler exhaust stream through a power turbine directly coupled to the main rotors, and they have also eliminated all of the complexity of a tail rotor and associated drive train by going with co-axial counter-roating rotors to provide necessary anti-torque.

It's the laws of thermodynamics I'm most concerned about, since most thermodynamic cycles suffer when cold fluids are introduced. Maybe eliminating the losses in mechanical transmission and weight offset that? Who knows, but if it works like they claim, that's pretty cool.