Friday, March 15, 2002

OK, I’ve had it for now with writing about the police state. Don’t think that I didn’t notice the fact that the feds are too concerned with exerting their authority over us to bother pulling the visas of foreigners who (1) are dead and (2) have flown planes into the WTC. That story has been covered to death; I really don’t have anything to add.

So, today’s blog is about a cool aircraft concept: the zero-roll gyrocopter. There are two companies that have been working on this concept: CarterCopters and the Groen Brothers. The CarterCopter achieves zero-roll liftoff by (1) spinning up the main rotor on the ground, while cancelling out the tortsional forces with the landing gear of the grounded aircraft, (2) storing the rotational energy in the rotor with the aid of rotor weights which turn the rotor into a gyroscopic energy storage device and (3) lifting off and achieving autorotation before the energy stored in the rotor dissipates. The Groen Brothers plan to achieve zero-roll takeoff by (1) turning the rotor with ramjets at takeoff then (2) lifting off and achieving autorotation before turning off the ramjets.

From what I can tell, the CarterCopter seems like a much more elegant design. No ramjets on the rotor means no fuel supply to pump into the spinning rotor, no need for ramjet maintenance, and no ramjet noise. Further, the CarterCopter team has already achieved reproducible zero-roll takeoff.

The other cool concept of the CarterCopter team, which the Groen Brothers don’t seem to be replicating, is the concept of slowing rotor speed in flight and generating lift with fixed wings. Current rotor wing aircraft have a limit on forward speed because the spinning rotor tip travels through the air faster on one side (the advancing edge) than on the other side (the retreating edge). At relatively low speeds, this leads to asymmetrical lift; the faster part of the rotor generates more lift than the slower part of the rotor, and steps must be taken to prevent the craft from tipping over. At high speeds, the advancing tip speed relative to the fuselage, plus the airspeed of the entire craft relative to the air, add up to a rotor tip speed that is much faster than the craft is traveling through the air. This exposes the advancing tip to more turbulence, even, in the extreme case, to mach buffeting. If the CarterCopter team can slow the rotor rotational speed enough, then this problem shouldn’t show up until much higher speeds, and so the aircraft can travel faster.

So all this adds up to a zero-roll, fast, efficient aircraft. Think you’d want one of those? I know I would. And I bet a lot of other people would too. I therefore nominate the improved gyrocopter, from whatever source, as my pick for the technology most likely to get us the Jetson’s-style flying car.

Next (probably tomorrow): the cheap, high-capacity AN2. Costs $50,000 to buy and $160/hour to run, holds up to 14 passengers and 2 crew, needs 492 feet to take off, and is barred by the FAA from any useful task in the US (damn, my hatred of the feds slips in again).

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