The 109-509 A-7 was a later variant of the engine for the World War II German Me 163B-1 Komet rocket fighter, the world's first operational military rocket aircraft. The 109-509 was the earliest "hot" variable thrust rocket engine to be installed in a service aircraft and used hydrazine hydrate and methanol as the fuel, with hydrogen peroxide and a phosphate catalyst as the oxidizer. The engine could produced a thrust variable from 200 to 1600 kg (660-3,500 lbs.) for durations of 8-10 minutes. The firm of Helmuth Walter in Kiel, Germany, developed the 109-509 and went into series production in August, 1944, for use in the Me 163 in attacks against U.S. bombers.

This engine was very likely captured by the U.S. Army Air Forces for evaluation at the end of the war and was later transferred to the Smithsonian Institution.