Improved Rotor Tip Rocket System
The rotor tip rocket system for autogyros and helicopters developed and demonstrated the summer of 2004, worked very well. We made vertical take-offs with the gyro glider that the prototype system was installed on (The project is reported in earlier articles in the left bar of this side)
Even so I am now developing an improved system (January 2005). There are mainly two areas of change:
1. Atmospheric Hydrogen Peroxide Tank
A pressurized tank was used before. The pressure was created with carbon dioxide added directly to the fuel tank. This worked fine, but an atmospheric tank is still to prefer.
The idea is to make use of the centrifugal force. The rotor is working as a centrifugal pump at rotation. According to my calculations there should be a pressure of around 90 bars (1300 psi) at the rotor tips of my 25 feet rotor at 300 rpm!
To get it all started I have installed a hand air pump on the tank, so I can pump up a small pressure in the tank by hand, before start. Once the rotor starts to rotate, the liquid is sucked up to the blades without any help from the hand pump. The pressure at the tips increases when the rotor is rotating faster and the rocket thrust will therefore increase until there is a balance between the rotor drag and the rocket thrust. If the size of the nozzles are correct, this balance point will be at above 300 rpm, so the gyroplane can take off vertically.
Check valves are installed at the root of each blade pipe, to prevent air to be sucked in backwards from one blade to the other.
The inner diameter of the pipes in the blades were 6 mm before, but have now been increased to 10 mm.
The pressurized composite tank used on the first prototype system weighed 2.9 kg and held 7 liters of HP plus 1.5 liters of liquid CO2 . The new atmospheric PE tank holds 10 liters of HP and weighs only 0.7 kg including the hand pump.
2. Partly Blade Integrated Rockets
The new rockets have the catalyst chambers inside the rotor. The nozzles are flange connected to the catalyst chambers. Only the nozzles are sticking out from the rotor tips. This design gives less aerodynamic drag. The distribution of the fuel over the catalyst cross section is better when having an axial flow in the chamber.
The rockets are lighter than before; 0.45 kg (1 pound) each including the silver catalyst. Some rotor blades, like the Dragon Wings, have tip weights for improved performance. These tip weights weigh typically 1 pound each, so if these tip weights are replaced by the new tip rockets, there will be no net increase of the weight of the rotor!
The temperature of the cat chamber is about 630 oC at operation with 85 % hydrogen peroxide. Aluminium melts at 660 oC, but the actual blade temperature at operation has not been any higher than around 50 oC or so at the first tests because I could hold my hand on the blades without burning myself, right after a test. This is because there is a thin air gap between the aluminium blade and the catalyst chamber, working as insulation, and there is a good air cooling of the blades because of the high velocity.
Present status
The system has been tested successfully a couple of times with the rotor on the fixed test stand shown on the pictures. See movie below:
First test with improved system.
I was only running the rockets for a short time to see that the system was working at all –which it did!
The next step is to make a more systematic performance test program. I need to measure the rotor speed and possibly make adjustments of the nozzle size and other system details, if needed. The only problem is that we are in the middle of the winter season in Sweden. I will report as soon as I have more data.
I hope to be able to offer the rocket system components for sale on this site soon. It would be nice if someone would be interested in evaluating the system on an autogyro! Please send me a line if you would like to take part in this!
Next report.
This article was updated on November 30th, 2006