German rocket car. Opel RAK 2 rocket car in 1928. Fritz von Opel is in the car, with Max Valier holding the car with his right hand. Opel's first rocket car was the RAK 1, tested on 15 March 1928, reaching a top speed of 75 kilometres per hour. Less than 2 months later, the RAK 2 was reaching speeds of 230 kilometres per hour using 24 solid fuel rockets. This early work on rocket cars and aircraft led to the development of liquid-fuelled rockets and the beginnings of space rocketry.