Opel RAK.1

The Opel RAK.1 (also known as the Opel RAK.3^[1]) was the world's first purpose-built rocket-powered aircraft. It was designed and built by Julius Hatry under commission from Fritz von Opel, who flew it on September 30, 1929 in front of a large crowd at Rebstock airport near Frankfurt am Main. The RAK.1 plane was part of a series of rocket-powered vehicles that were developed and demonstrated within the Opel RAK program, the world's first large-scale rocket program.

The idea to build and race a rocket-powered car as an intermediate step to realize rocket-powered aviation and even spaceflight was suggested to von Opel by Max Valier. After the World War I, Valier became highly interested in rocketry. Valier, in 1927, he was one of the co-founders of the German Verein für Raumschiffahrt, or "Spaceflight Society", a group of later highly influential scientists who would play a major role in making rocket spaceflight a reality. As an early spaceflight advocate, 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. Von Opel confirmed his interest in realizing Valier's proposal. On behalf of von Opel, Valier eventually contacted Friedrich Wilhelm Sander, a German pyrotechnical engineer who, in 1923, had purchased H.G. Cordes, a Bremerhaven firm famous for its manufacture of black-powder rockets used mainly for harpoons, signal devices and similar devices. Opel, Sander and Valier joined forces and combined into one entity the financing, the theoretical knowledge, and the practical capability necessary for success. Moreover, von Opel, Valier, and Sander said from the start that their experiments with cars were only a prelude to grander experiments with air- and spacecraft: They agreed on the final goal for Opel RAK of working on rocket-powered aircraft at the same time they were building their famous rocket cars, as pre-condition for the anticipated spaceflight application.^[2]