Swisscopter’s Dragonfly is a small helicopter that has rocket engines on the ends of its rotors blades to propel them:
The copter makes use of tiny hydrogen-peroxide-powered rocket motors on the tips of the blades, which replaces the traditional engine-powered rotor. Large fuel tanks surrounding the pilot allow the Dragonfly to travel at up to 40 mph for 50 minutes.
Anonymous Backstabber
Hmmm. Color me an idiot, but I thought that if the power was coming from thrust at the tips of the rotors (instead of from a powered axle), there was no need for a tail fan for counter rotation…
strayxray
The tail rotor would be needed for yaw (turning left and right). A normal helicopter needs a tail rotor to constantly fight the counter-rotation from the main rotor; this helicopter would need a tail rotor to make it turn left or right.
It appears to be geared with the main rotor, but is likely pitched such that it doesn’t provide any thrust to the left or right during flight. When the pilot wants to turn, he pitches the tail rotor blades to provide thrust.
If the tail rotor failed, the helicopter would be just fine, although it would have no ability to turn on its emergency descent.
Homer Jay
@ strayxray
actually it would start to spin uncontrollably with out the tail rotor, just because there is no powered axle between the main rotor and the main body of the helicopter doesn’t mean that the friction from the rotor and where it is connected to the body isn’t enough to cause it to start spinning. We don’t live in a world with frictionless bearings. Also the fuel delivery system to the rockets probably add’s a lot more friction to the main rotors axle.
It might not happen as quickly and violently as a normal heli would if it lost it’s rotor, but if he were high enough, by the time he got the heli to the ground he could be spinning like a tea cup.
Foreigner1
Every action gives re-action. So the main body of the chopper will rotate in the oppsite direction of the main rotor. Don’t forget that there is a fuelline-coupling from the main body to the rotorblades that gives added friction. So the tailfan is needed.
I like the noise of that thing- While most chopperbuilders work frantically on reducing or even cancelling the noise of their rotorblades as best as they can to make their choppers more useable in crowded areas, these guys come up with a system that wakes up the whole valley when they start up their machine. 
Rob
This concept is not exactly new. In the 1950s a Dutch company built 11 Kolibri’s (Hummingbirds):
http://www.youtube.com/watch?v=8jhpUJLhQfs
http://en.wikipedia.org/wiki/Nederlandse_Helikopter_Industrie_(NHI)
And an American prototype:
http://en.wikipedia.org/wiki/YH-32_Hornet
All designs failed…
zeytoun
With torque the entire force generated by the engine gets split between the rotor and the body of the helicopter.
The difference with friction as a force is two fold. First, obviously, is that it would be in the direction of the rotors, not the opposite direction. Second, we’re talking an incredibly small amount of the output of the engine being transferred via friction (easily as low as .01%). Third, it takes much more energy to spin the heavier body of the helicopter than the rotors.
So it would take very, very little to cancel it out.
Ilan Ben Menachem
this is right on it…Every action gives re-action. So the main body of the chopper will rotate in the oppsite direction of the main rotor. Don’t forget that there is a fuelline-coupling from the main body to the rotorblades that gives added friction. So the tailfan is needed.
Skipweasel
I’d have to be really convinced of the durability of those tanks in a crash before sitting amid gallons of high-test peroxide.
tight turns
hey guys….stop thinking like a regular heli…the trust created by the jets is the prim factor of this equation….the blades move in an opposit direction to the exiting energy from the jet….the body of the vehicle, thru drag, will tend to follow the directions the blades are rotating in…the speed at witch the vehicle travels depends on the friction present at the rotor bearins and the vehicle mass that is presented to the air around it..ie…if there is a lot of friction the heli will turn quicker but if the was a huge flat panel sitting flush to the direction it is rotating in then it would tend to act as an air brake and slow down the action of rotation in proportion to its size…..space travel is marvelous…time travel is quicker….zorro
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