The Walter HWK 109-509 was a German liquid-fuel bipropellant rocket engine that powered the Messerschmitt Me 163 Komet and Bachem Ba 349 aircraft.
It was produced by Hellmuth Walter Kommanditgesellschaft (HWK) commencing in 1943, with licensed production by the Heinkel firm's facilities in Jenbach, Austria.
Worse, however, was the fact that the engine could not be throttled, and when the aircraft leveled off after its climb to altitude it quickly accelerated to speeds that caused serious compressibility issues.
The pumps were driven by a single turbine, powered by steam created by decomposing the T-Stoff with a wire mesh catalyst.
In practice it was found that throttling the engine dramatically decreased its fuel economy to the point that it did not extend the endurance of the aircraft as expected.