HM-7

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HM-7B engine

The HM-7 rocket engine was developed for the high-energy hydrogen / oxygen third stage of the Ariane 1 and had 60 kN thrust. Like the current HM-7B, it was not re-ignitable.

The first flight took place on December 24, 1979. In further test flights, it was possible to confirm the experience already made on this flight that the engine had a higher specific impulse than calculated, which means that the payload capacity of the Ariane 1 was above plan.

HM-7B

The HM-7 has been further developed for use in the successor models Ariane 2 , Ariane 3 and Ariane 4 to the increased thrust HM-7B with 64.8 kN thrust. Its first flight was on August 4, 1984 with an Ariane 3.

During the long production period of the Ariane 4, the HM-7B engine was further developed, whereby the thrust was increased and the mixing ratio was changed from 5: 1 to 6: 1 in order to enable the third stage to transport more fuel. However, the name of the engine was not changed. Because of the comparatively demanding H 2 / O 2 technology, the HM-7B engine was the most unreliable engine in the Ariane 1-4 rockets. It was only after the 5th failure of an HM-7 / HM-7B series engine that the faults could be eliminated during a take-off break lasting several months. Since then, the HM-7B engines have been flying flawlessly.

Due to the now high reliability of this engine and the rapid availability, it was decided to take it over in the performance enhancement program of the Ariane 5 for the Ariane 5 ECA , for which it was again increased slightly in thrust to 70 kN and in specific impulse. In addition, it was now max. 970 sec. Long burning time adjusted (Ariane 4 only max. 780 sec.).

The Ariane 5 ECA, however, was originally only planned as a short-term interim solution until the even more powerful Ariane 5 ECB with the new Vinci engine is ready for use. Due to the lack of heavier satellites, the Ariane 5 ECB was initially postponed indefinitely. After the resumption of planning, the now called Ariane 5 ME (Midlife Evolution), also otherwise modernized Ariane 5 version 2016/2017, should take off for its maiden flight. However, it was canceled at the ESA Ministerial Council in favor of Ariane 6 . Until the Ariane goes into service around 2021, the Ariane 5 ECA and the HM-7B are expected to remain in service.

Web links

Individual evidence

  1. ↑ Bernd Leitenberger: History of Ariane 4
  2. ↑ Bernd Leitenberger: The upper levels H-8, H-10 and ESC-A