No, not that kind of strap on. Get your minds out of the sewer.
A strap-on helicopter:
Tiny rockets at the tips of the helicopter's rotor blades take the place of a tail rotor, a component which couldn't be safely attached to a human body. According to the company, the Libelula would be the lightest helicopter in the world, so light that it could be strapped to a person's body with a carbon fiber corset.
"The best [part] of this technology is that [these] kinds of helicopters don't need a tail rotor because they don't have any torque, so with a simple vane they can turn - being the simplest form of an helicopter and the easiest and safer to fly," the company says on its Web site.
So, first question is: how do they prevent the pilot/passenger from rotating with the blades (there's bound to be non-zero friction in the bearing)? Seems like you'd get kinda dizzy, and it would be hard to steer.
There would also seem to be safety issues for bystanders--that thing could easily decapitate someone.
A helicopter in flight makes a down draft, the little vertical vane on the back tilts right and left working against this air flow column to control yaw. The only torque it needs to overcome is bearing friction. It also needs to be sized to allow enough hovering control authority.
Paul
Also, some of the torque comes from a reaction from the main shaft on the engine, and since the engine is in the body of an helicopter or airplane, the impulse to turn the blades cause a similar and contrary impulse on the main body (all civilian pilots know the sensation, when they accelerate the airplane it tends to rotate a little, especially ultralight airplanes of the 1st and 2nd generation). Since the impulse comes from the tip of the blades, this torque is diminished, I guess.
It seems to me that the propellant is in the backpack. So you might experience some torque as the propellant goes from the backpack to the rockets. I really don't know enough about this system to say.
Since the impulse comes from the tip of the blades, this torque is diminished, I guess.
It's not diminished--it's non-existent. There is no reaction on the shaft, because the shaft is not providing the torque--that comes from the tip jets. The only torque imparted to the body comes from bearing friction.
It looks like there is a small fin coming off his back to counter act any small friction induced rotation. However I see a few problems.
1. Sound! This design has been tried before, and I believe it would generate something like 150dB at 50 yards. When they cranked it up it would stop all work at Edwards AFB.
2. Gyroscopic effects. As the guys at Roton found out they can be a bitch to control when you start to rock back and forth like a pendulum attached to a top.
3. What happens when this guy accidentally leans to the right too much and the blade hits the ground?
It looks like there is a small fin coming off his back to counter act any small friction induced rotation. However I see a few problems.
1. Sound! This design has been tried before, and I believe it would generate something like 150dB at 50 yards. When they cranked it up it would stop all work at Edwards AFB.
2. Gyroscopic effects. As the guys at Roton found out they can be a bitch to control when you start to rock back and forth like a pendulum attached to a top.
3. What happens when this guy accidentally leans to the right too much and the blade hits the ground?
Roton was not the first helicopter using this design, it's nothing new really. See: http://en.wikipedia.org/wiki/Tip_jet
Mmm, carbon fiber corset.
(Sorry, I already had weekend reservations in the sewer.)
What do you mean? Manfred von Richthofen described it in 1917!
"I think things will come to this, that we shall be able to buy a flying suit for half-a-crown. One gets into it. On the one end there is a little engine and a little airscrew. One sticks one's arms into the planes and one's legs into the tail. Then one does a few leaps in order to start and one goes up into the air like a bird."
-- Der Rote Kampffleiger, 1917
by Manfred, Freiherr von Richthofen
And today's his birthday! Fröhlicher hundert sechzehnter Geburtstag!
Two blades, contra-rotating.
Rube Goldberg would be proud.
I remember seeing this in a PopSci or PopMech article in the 1970's. Exact design, right down the the H2O2 propellant.
One major issue (as the Germans found out in WWII) is that H2O2 of sufficient concentration tends to be a bit, shall we say, unstable.
I've seen the 150db minicopter in an aircraft museum in Florida (Flight of Fantasy). It was meant as an artillery observer. It sucked down fuel like a maniac, deafened the pilot, and was so loud it prevented radio communication.
The tip jets also lit up the sky, providing an excellent aiming point.
Ryan's point 2 - about the porpoising motion - was IIRC the serious, indeed frequently fatal, flaw in the last such attempt. I unfortunately can't remember the company name. A former cow-orker with a pilot's license told me that failure to successfully dampen that motion within the first two or three swings usually resulted in the entire mechanism, with attached human, flipping over completely, abruptly ending the flight.
Also concur that noise is going to be horrific unless/until there's a version with ducted-fan propellers.
But man, I want one. It's the 21st century! Where's my flying car?!
Google "magill pinwheel" It worked just fine. Here's a link to the old "flying contraptions" page.
http://web.archive.org/web/19981205110025/www.shreve.net/~jnuts/fly/old/
A later incarnation was the "intora firebird", derived from Magill's design.
http://www.youtube.com/watch?v=O9S_Qmn-CEM
It's a dramatic demonstration of the effect of increasing mass flow - a peroxide jet belt has a flight time of 30 seconds, the pinwheel flew for 30 minutes.
Also note that noise wasn't a problem.
This looks like a good way to get greater endurance, without building a jet belt. (except for the flipping over part, if that's the case)
Hmmmm.
What about building a seated framework and using an array of RC jet engines to power it? Wouldn't that work as well? Plus the redundancy of multiple engines
memomachine wrote:
Hmmmm.
What about building a seated framework and using an array of RC jet engines to power it? Wouldn't that work as well? Plus the redundancy of multiple engines
45 lb thrust seems to be available off the shelf in RC jet engines. I'm told larger ones have insurance issues.
90 lbs thrust at blade tips should give enough performance to match the peroxide rocket units at 1/10 propellant consumption. No idea if they will function in a high gee field.