Klaus Erhardt Riedel was born in Wilhelmshaven, Germany on August 2, 1907. His mother died when he was twelve years old, and his father, a naval officer, died two years later, leaving Klaus to be raised by his grandmother on the family farm in Bernstadt. In 1929, as a machinist trainee at the Technical College of Berlin, he attended a public lecture on rocketry by Rudolf Nebel, one of the leaders of Germany’s amateur rocket group, the Verein für Raumschiffahrt (VfR, or “Spaceflight Society”). Riedel immediately joined the group and became one of its key members in the drive to build a rocket, and eventually, he produced the Mirak and Repulsor rockets.

The first of these were tested at Riedel’s family farm in 1930, and he continued to develop the Mirak liquid-propelled rocket. Though some of the 100 flights of the Mirak rockets were out of control, Riedel succeeded in building a series of successful motors, and after many tests, achieved significant results until September, when the motor exploded, ending the test series.

Wernher Von Braun later remembered the early days of the VfR:

“Our equipment was elementary, and our ignition system was perilous. Klaus Riedel would toss a flaming gasoline-soaked rag over the gas-spitting motor, and then duck for cover before [Hermann] Oberth opened the fuel valves and it started with a roar. We were temporary guests on the proving grounds of the Chemical and Technical Institute, the German equivalent of the U.S. Bureau of Standards.

In August 1930, Professor Oberth’s little rocket engine succeeded in producing a thrust of 7 kilograms for 90 seconds, burning gasoline and liquid oxygen. An official of the Institute certified the demonstration. The liquid-fueled rocket motor was thus recognized for the first time in Germany as a respectable member of the family of internal-combustion engines.”

On May 10, 1931, Klaus Riedel created the Repulsor rocket, using the thrust chamber developed for the Mirak rocket. The rocket rose to over 60 feet on its first test, and in early June, the Mirak II/Repulsor 3 rocket reached 560 feet. In August 1931, Riedel and his cohorts launched the Mirak II/Repulsor 4, which reached an altitude of over 3000 feet, and another Repulsor would fly to 4800 feet in altitude.

By the summer of 1932, Riedel had helped develop the Mirak III rocket, which was over eleven feet high and three inches in diameter, with a thrust of 132 pounds per foot. The new design featured the engine forward of the stack, followed by the liquid oxygen tank, then the alcohol tank, then the manometers and other elements of propellant pressurization. Unfortunately, the rocket rose only 225 feet before veering off-course.

By the fall of 1932, private rocket development in Germany was nearing an end as the VfR began to disintegrate, primarily due to lack of funds. Despite turmoil in the VfR, Riedel continued to improve on the rocket fuel for his Mirak engine, eventually rejecting further use of gasoline in favor of alcohol.

On September 30, 1933, the VfR was officially disbanded. Klaus Riedel managed to find work for himself and several other VfR alumni with the Siemens Company. Soon all German rocket development was taken over by the Army, and private experimenters were ordered by the Gestapo to cease and desist.

Von Braun invited Klaus Riedel to help in the Nazis’ military development of rocketry. He accepted and was named Head of the Test Laboratory, responsible for ground support equipment at the German Army’s rocket center in Peenemünde. At first, Riedel was unsuccessful but von Braun had Riedel develop a mobile launch system for A-4 rocket. Riedel succeeded and was the first to design, develop, and perfect equipment for handling large rockets on the ground and getting them launched on their flights. This was a crucial advancement in the development of the A-4 rocket, soon renamed the V-2, during World War II.

While his involvement with the Nazi government and its terror weapons may make Riedel and his associates odious to modern sensibilities, his co-workers at Peenemunde remembered Klaus Riedel as being very sociable and likable. He was killed in an automobile accident near Karlshagen, Germany on August 4, 1944. Riedel Crater on the Moon is named in his memory.