A liquid-fuel rocket-assisted take-off engine. It allowed for a shorter take-off run and also enabled easier take-off of an aircraft with a heavy load. A parachute was mounted at the front of the nacelle, allowing for a soft landing after the engine finished working and was jettisoned from the departing aircraft. This made it possible to reuse the booster engine multiple times.
The HWK 109-501 engine was designed based on the concept of Prof. Hellmuth Walter, who from 1935 had been working on the practical application of hydrogen peroxide, initially for submarine propulsion and later for aircraft as well. The HWK 109-501 was a development of the earlier HWK 109-500 rocket-assisted take-off engine from 1937. Using HWK 109-500 type engines, approximately 3,000 take-offs were performed during World War II. The HWK 109-500 used a so-called “cold system”. The exhaust gases were produced through a chemical reaction rather than combustion.
The metal nacelle housed tanks for propellants and compressed air, as well as a combustion chamber. The propellant consisted of three components: 220 kg of hydrogen peroxide at approximately 80% concentration (T-Stoff), 12 kg of calcium or potassium permanganate (Z-Stoff) and 20 kg of kerosene mixed with hydrazine hydrate (Br-Stoff + B-Stoff). Compressed air forced these materials into the combustion chamber. The combustion chamber was cooled by hydrogen peroxide during operation.
Further work on improving this engine focused on increasing thrust and operating time. The result was a new take-off booster engine HWK 109-501, operating on the so-called “hot” principle with a more complex propellant composition and considerably more complicated construction. This was the reason for the engine’s limited popularity. It was used in 1944 during take-offs of the experimental turbojet-powered aircraft Junkers Ju 287 (forward-swept wing trials).
| Weight | 250 kg |
| Combustion chamber temperature | 2000 ̊C |
| Operating time | 30 s |
| Thrust | 1500 kG |
