Also a rocket-powered RAK-Motoclub motorbike, based on a conventional Opel Motoclub 500 SS and presented at the Berlin Motorshow 1928, did not receive a formal RAK number.

Valier was more interested in publicizing rocketry than marketing Opel automobiles but came to the conclusion that building a successful rocket-powered car would achieve both goals.

On behalf of Von Opel, Valier eventually contacted Friedrich Wilhelm Sander, a German pyrotechnical engineer who, in 1923, had purchased H.G.

Opel, Sander and Valier joined forces and combined into one entity with the financing, the theoretical knowledge, and the practical capability necessary for success.

March 12, 1928, was selected as the date for the car's first trial run, applying only two rockets, which were to be ignited by conventional string fuses, for low-speed testing.

Nevertheless, it was clear to the RAK program leadership, they had no plans to commercially produce rocket cars for end customers, the aim was the development and demonstration of a rocket-powered aircraft.

After these introductory remarks, mechanics August Becker and Karl Treber then took the tarpaulin off the Opel RAK 2 and carefully pushed it to the start.

Police cleared the AVUS track and von Opel drove the RAK 2 car to a record-setting speed of 238 km/h, successfully mastering the challenge of insufficient downforce from the wings for these velocities.

The RAK 2 rockets were operational for a ride of circa three minutes, watched by 3000 spectators and world media, among them Fritz Lang, director of Metropolis and Woman in the Moon, world boxing champion Max Schmeling and many more sports and show business celebrities:[21] … Nevertheless, few, if any, among the many thousands of onlookers who witnessed the demonstration on the AVUS track could help but feel that we are poised at the beginning of a new era.

Otto Willi Gail, Illustrierte Zeitung, Leipzig, 1928 A world record for rail vehicles was reached with RAK3 on June 23, 1928, with the car attaining a top speed of 256 km/h over a 5-km stretch of straight track near Hanover.

After testing at Wasserkuppe, in June 1928, Fritz von Opel had purchased an Alexander Lippisch-designed sailplane, the Ente, and fitted it with rockets.

Before a large crowd assembled outside of Frankfurt, the intrepid von Opel made a successful flight of almost 3.5 km in 75 seconds, reaching an estimated top speed of around 150 km/h.

According to Frank H. Winter, curator at National Air and Space Museum in Washington, DC, the Opel group was also working on liquid-fuel rockets (SPACEFLIGHT, Vol.

21,2, Feb. 1979):[25] In a cabled exclusive to The New York Times on 30 September 1929, von Opel is quoted as saying: "Sander and I now want to transfer the liquid rocket from the laboratory to practical use.

[26] "He belonged," von Opel said, "with the same enthusiasm as Sander to our small secret group, one of the tasks of which was to hide all the preparations from my father, because his paternal apprehensions led him to believe that I was cut out for something better than being a rocket researchist.

After 2000 m of rope had been unwound, the line broke and this rocket also disappeared in the area, probably near the Opel proving ground and racetrack in Rüsselsheim, the "Rennbahn".

He lived long enough to see the fulfillment of his dreams with the successful Apollo missions which can be traced back to Opel RAK.

Sander was eventually engaged in the 1930s in German military projects under General Walter R. Dornberger but was imprisoned for treason by the Nazis and forced to sell his business, he died in custody 1938.

Hatry was drawn into theater and fiction, finally his mother convinced him after his father's death to take over the family's real-estate business.

Opel, Sander, Valier and Hatry had engaged in a program that led directly to use of jet-assisted takeoff for heavily laden aircraft.

The German Reich was first to test the approach in August 1929 when a battery of solid rocket propellants supported a Junkers Ju-33 seaplane to get airborne.

The Opel RAK experiments excited also the interest of the German military, which provided funding for further development of rockets as a replacement for artillery.

Walter J. Boyne, Director of the National Air and Space Museum in Washington, DC, concluded "Working together, von Opel, Valier, and Sander had thrown a big rock of publicity into the mill pond of science.