My visions of how tip rockets can be used on an autgyro
Picture: Igor Bensen is testing rotor tip RAM jets in the 1950's. I believe they were too big and heavy to allow for proper autorotation performance
You can read about the development of my hydrogen peroxide rotor tip rocket system if you want a background to this article,. You find the reports in the navigation bar to the left.
The demonstrations of the system made this summer of 2004 show that the system can be used for pre-rotation and for making a vertical take-off with an autogyro. I would say this is nothing less than a revolution for the autogyro sport, as it makes the low-cost autogyro almost as useful as the much more expensive and complicated helicopter. There is no need for a prepared airfield, for take-off! Landings with an autogyro have always been possible to make on a short field. (As short as 100 feet).
My vision is that there are still more benefits with the rotor tip rocket system! I will discuss these possibilities in the following.
Propeller Powered Autogyros
An UL autogyro with a total weight of 254 pounds, typically needs a 45 hp motor for driving the propeller. Such a motor weighs nearly 100 pounds and costs around $ 3500.
The maximum power output is needed at take-off and at certain flight situations like when climbing or making turns. The rotor tip rockets can be used during flight and I believe they can be used in all these situations in order to reduce the maximum need of propeller power. Only 15 to 20 hp is needed for cruising with a light autogyro. Such a small motor is as light as 20 pounds and the cost is as low as $ 650. These are significant savings in weight and cost!
There are several such engines on the market. One example is the DINO 505 25 hp for go-carts. List price DKK 4000 (~US$650). An other attractive alternative is the Radne Raket 120 Aero ,even if the power output from this engine may be on the low side. Hirth has one 28 hp engine for UL airplanes.
For calculating the flight characteristics of an autogyro and the need of engine power, I recommend the calculation program made by Jukka Tervamaki. You find it here.
Let us say you are cruising with your autogyro at horizontal flight and at constant speed. What happen if you squeeze open the flow to the rotor tip rockets? Well, this has never been done so far, as far as I know. It remains to be tested, but I believe you will ether start climbing or you will start travelling faster, depending on the angle of the rotor disc. This is because the rockets will overcome part of the rotor drag. I believe you can make a turn without loosing height despite of your “under powered” propeller engine, because you are able to compensate with some rocket power at the rotor tips.
Let us say you are coming in for landing. Your propeller engine is just idling. You are descending and have the stick in a slightly forward position. If you than give the rockets some peroxide flow and move the stick back, I believe the forward speed would decrease a lot and you would descent more or less vertically to the ground. This is what gyro pilots call a flare out landing. My vision is that it would be a shorter and more vertical landing when adding some rocket power to the rotor.
To summarize my vision: Rotor tip rockets can be used for making a vertical take-off and a shorter landing. Lighter and cheaper propeller engines than today can be used.
Gyro Gliders
The pioneer testing of the rotor tip rockets we made this summer was made on a gyro glider without a propeller.
We found that the gyro became unstable when trying to hover or when descending, if not being chained to a stretched rope in the nose similar to having a stabilizing pushing power from a propeller or from the towing car. My impression and my belief is that one can make a steady and stable climb though.
My vision is therefor that one could use rotor tip rockets on an autogyro glider to climb to a high altitude and than glide back to the ground. Quite an experience I would imagine! I believe it could be done without hurting yourself, because a light gyro glider will descend with a constant velocity of only around 4 to 5 m/s at autorotation.
I would expect the gliding ratio (length/descent) to be around 5. There are good chances it will be a smooth landing. I mean, after all, gyro pilots are training engine failure landings all the time! The engine is just idling even at normal landings with a powered autogyro.
Strap On Gyro Glider
The ultimate vision is a strap on gyro glider with rotor tip rockets! You lift yourself with the rotor tip rockets and than glide with autorotation back to ground. The landing can be quite smooth I believe, because the rotor will continue to rotate after taking ground so you will not feel the weight of your back pack rotor. On the opposite it will try to lift you, until the rotation has slowed down. This effect would help you to stay on your feet, so that you don’t fall and smash the rotor blades. If giving the rotor tip rockets some power before taking ground the landing could be even smoother. You have to agree it would be spectacular! It would be a real thrilling alternative to paragliding and other similar sports, with the important benefit that you lift yourself from flat ground, without the need of a steep hillside or an aeroplane.
Baumgartls Strap-On Helicopter from the 1940's was the closest example I could find for illustrating my strap-on autogyro glider idea. There are important differences though. An autogyro descends slowly and safely at autorotation. I do not think you need an over head stick with a pivoting rotor. I believe it would be better to control the gliding direction by changing the center of gravity of the body by bending the legs back or forth or to the sides.
Next report here.
This article was updated on August 6th, 2007