Mirak   rockets

• Soon after the "Verein Fur Raumschiffahrt" (VFR: Society for Space travel) moved into the Raketenflugplatz in September 1930, they decided to build what Rudolf Nebel suggested be called a Minimum RAKete - MIRAK rocket series. Klaus Riedel designed the rocket, bearing in mind the materials he had to hand.
• The copper engine, "a few inches long", was based on Hermann Oberth's KEGELDUSE (Cone Engine), successfully fired in July and August 1930. The engine was placed in the bottom of the bullet-shaped Liquid Oxygen 5LOX) tank. A valve at the base of the LOX tank led into the side of the engine. The gasoline tank was a slender Magnesium alloy pipe fitted opposite the LOX valve. Somehow Nebel had managed to scrounge a whole load of Magnesium piping, by persuading a stockiest of future large orders when rocketry really took off.
• A Carbon Dioxide capsule was fitted to the bottom of the gasoline tank. The gasoline supply pipe extended from the bottom of the tank to the engine. The LOX tank was about 0,305 m long and 0,10 m in diameter, while the "stick" was about 1,0 m long and 0,03 m in diameter.
• MIRAK-1 was set up on a stand at the Raketenflugplatz for static test and fired late September 1930. Loading the gasoline was straight forward enough. After the LOX tank was charged, its pressure built up by its own expansion. At the appropriate moment, the gasoline was pressurized and started flowing into the engine, after which the LOX valve was opened and the little engine would have sprung into life. however at some point in the proceedings, the LOX pressure rose too high, bursting its tank and wrecking the rocket. Obviously the LOX tank was left pressurized too long.
• MIRAK-2 embodied considerable improvements over MIRK-1, most notably a LOX pressure release valve on the head, and also a larger capacity gasoline tank. The rocket was about 2,75 m long. Also the engine was cooled more efficiently by having larger area in contact with the LOX. A special static launching frame was built. In the spring of 1931, during a number of static tests, thrust of about 32 kg were developed during the 10 second burn time. Later the engine burned through, and the rocket exploded during a static test.
• MIRAK-3 was built while MIRAK-2 was still under test in the spring of 1931. It had the same size 0,1 m LOX tank head, but had four 0,03 m "sticks"; two for gasoline and two for compressed Nitrogen. The engine was in the base of the LOX tank now. It was between the "sticks" surrounded by a water jacket. Although this quickly boiled, it kept the engine around 100 degrees centigrade on the water side. Launch weight was 4,1 kg, and the engine had a thrust of between 9,1 and 8,2 kg, and could burn for 32 seconds. It made the VFRs first liquid propellant flight on May 10, 1931 and rose to 18,3 m altitude. It was subsequently repaired and launched as REPULSOR-1 on May 14, 1931.

The Mirak-II rocket.

Launch log:

 Nr        Vehicle              Date 		Notes
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 1           MIRAK-1       Sept. 1930   	Oxygen tank burst after loading, during static test
 2           MIRAK-2       spring 1931 	Exploded during a static test  
 3           MIRAK-3      10.05.1931   	Success launch, rose to 18,3 m altitude