Distillation and Rocket Testing, April May -03
Distillation of Hydrogen Peroxide
The first thing needed for practical rocket development is high concentration rocket grade hydrogen peroxide.
Despite the fact that I have many personal contacts in the industry, it turned out to be very complicated and expensive for a small consumer like me to buy high concentrated HP on the market. For this reason I have erected my own distillation unit. I buy standard grade HP with 35 % conc. and concentrate it in the distillation equipment to 80 to 90 % conc.
So far (June 2003) I have produced 40 kg high concentrated rocket grade HP. The production capacity is 4 kg/day at this time, but can be increased considerably when there is a need for it. All equipment in contact with the product is made in glass. Other materials like aluminum or stainless steel would decompose the product and make it unstable. The distillation is made under vacuum. The absolute pressure at the top of the column is 30 mbar. This is necessary to keep a low temperature on the boiling product. If distilling at ambient atmospheric pressure the hot HP vapors would be explosive at these high concentrations.
Test Rocket System
To be able to test catalysts and different design solutions under realistic conditions, I have built a test system. It consists of the following parts.
1. Fuel Tank
The tank has a volume of 8,5 liters and a design pressure of 140 bar. It is a composite construction with an inner liner of aluminum and an outer layer of epoxy resin reinforced with a mixture of glass fibers and carbon fibers. The weight is 2,9 kg.
2. Rocket
The rocket is made in stainless steel. The inner diameter of the rocket body/catalyst chamber is 50 mm (2”) and the length is 325 mm (13”). The nozzle throat diameter is 6 mm and the nozzle exit diameter is 14 mm. These dimensions would give the rocket a thrust of about 17 kgf under ideal conditions. The nozzle and the opposite end of the rocket are threaded to the rocket body.
3. Pipes and valves
The piping system between the tank and the rocket consists of 3/8” pipe, a safety valve, a check valve, a flow control valve and a manometer.
4. Pressurized Tank System
In a rocket system, there is either a fuel pump or a pressurized fuel tank. I have chosen the later solution. The tank gets a pressure of 40 to 55 bar.
Test Bench
During tests the rocket is fixed in a bench with the nozzle pointing vertical and upwards, so that the rocket thrust is directed downwards. The test bench is connected to a scale to measure the thrust. The rocket is equipped with a temperature sensor between the catalyst pack and the nozzle. A manometer measures the pressure after the peroxide flow control valve.
At testing I record the readings on the instruments and other observations by talking into the microphone of a tape recorder. In this way I can check times and other parameters after the test.
Rocket Tests
So far (June 2003) four different tests have been run. They are all connected to a couple of own ideas around rocket propulsion that have evolved during a longer period of time. When finally set up to run rocket tests I was of course eager to evaluate these innovations right away! I will describe the tests in the following, but because I am considering the possibility to file patent applications all details can not be revealed at this time.
Tests 1 and 2: April 2003 - Test of a novel hybrid rocket concept
Hybrid rockets are interesting because they have lower fuel consumption than mono propellant rockets (almost half the consumption!). There is also a potential to use lower concentrated hydrogen peroxide as a fuel.
The first and second rocket tests aimed at testing a novel hybrid rocket idea. The concept worked in principle. The temperature before the nozzle reached 1400 oC. The thrust was easy to control by throttling the flow control valve. The capacity was however lower than expected in both tests, even if it improved in the second test. The capacity limitation showed up when the rocket “choked” before the control valve was fully opened. “Choking” means that cold and un-decomposed liquid hydrogen peroxide was leaving the nozzle as a visible “fog”.
In any case the tests were successful enough to still consider the possibility of filing a patent application.
Test 3: May 2003 - Test of decomposition catalyst
The test was run to get performance data for a mono propellant decomposition catalyst that I have prepared. The active catalyst material is MnO2, manganese oxide, deposed on aluminum oxide pellets, 3 to 5 mm in diameter.
Result:
The tank was filled with 7,5 liter HP 86% conc, pressurized to 39 bars. The rocket ignited instantly when the fuel valve was opened.
The valve was quickly opened fully (aka a ”Slam start”). The thrust was stable at 11 kgf. The pressure after the valve was 37 bars. Temperature after the catalyst chamber was 670 oC.
The valve was throttled for a few seconds and opened fully again to make sure that the rocket was easy to re-start and control.
The tank was emptied in slightly over two minutes.
Inspection of the catalysts after the test and conclusions:
The catalyst pellets had broken up into a fine powder in the inlet area.
When putting in the measured performance data into the calculation program, the results fit well when the pressure after the catalyst bed is set to 27 bars. It makes sense that the pressure drop could have been 10 bars, taking into account the breakage of the catalyst at the inlet.
The catalyst activity was calculated to be 11 kg HP/liter catalyst, minute. However the catalyst activity was not the limiting factor in this test. Instead it was the fuel flow, because the gases were still hot and invisible at fully opened valve. Therefore the maximum catalyst activity was higher than 11 kg/liter, minute.
Test 4: May 2003 - Test of a jet engine:
Jet engines have even lower fuel consumption than hybrid rockets, but can on the other hand not fly as fast. Normally this is not a problem, because there is no need for such a high speed at most civil applications.
I have invented a very simple jet engine, propelled with hydrogen peroxide and even built a prototype of it. Test 4 was for evaluation of this prototype. The catalyst from Test 3 was used for the decomposition of the peroxide fuel. Some of the expectations for the prototype were met – some were not. However, I still feel confident that this invention is worthwhile to continue working on as well.
The catalyst activity had dropped from > 11 kg/liter, minute in Test 3 to about 8 kg/liter, minute in this test. This shows that the lifetime is short for this catalyst, when using the high stability rocket grade peroxide that I make in the distillation unit. The reason is that the stabilizing agents and other trace elements poison the catalyst. However the catalyst is not expensive, so it make sense to load fresh catalyst before each start.
Conclusions so far
* I have learned a lot about practical hydrogen peroxide rocketry from these tests.
* The pressure holding system works fine.
* Hybrid rockets and jet engines are promising but will take time to develop.
* MnO2 catalyst is a feasible low cost alternative for mono propellant rockets.
Development Report, June
This article was updated on November 30th, 2006