In 1973, the Ottobrunn team started development of the HM-7 thrust chamber for Ariane's upper stage rocket engine. Six years later, the HM-7 engine was successfully qualified with the first launch of Ariane 1 in December 1979. The HM-7 rocket engine featured Ottobrunn's unique regenerative cooling technology whereby hydrogen propellant was efficiently used to cool the combustion chamber before being injected for combustion.
|HM7-A SEP, Ottobrunn LOx/LH2 rocket engine. Development begun 1973. Out of production. Used on Ariane 1 launch vehicle. First flight 1979.|
|HM7-B SEP, Ottobrunn LOx/LH2 rocket engine. Increased performance version of the HM-7 engine for the Ariane 2 and 3. Combustion chamber pressure raised from 30 to 35 bar and nozzle extended. First flight 1984.|