Rocket Engines and
Thrust Chambers

LV Propulsion
Aestus
Vulcain
Vulcain 2
HM 7B
Vinci
RS 72
300 N cryo. Engine

HM-7 and HM-7B Rocket Engine - Thrust Chamber

A cryogenic propellant upper stage rocket engine used on all versions of Ariane.

Snecma's HM-7 cryogenic propellant rocket engine has been used as an upper stage engine on all versions of the Ariane launcher. The more powerful HM-7B version was used on Ariane's 2, 3 and 4. and is also used on the ESC-A cryogenic upper stage of Ariane 5.

Since 1973, the Ottobrunn facility of EADS Astrium has been responsible for the development and manufacture of all versions of the HM-7 and HM-7B thrust chamber comprising:

Regeneratively cooled combustion chamber.
Coaxial propellant mixing injectors.
Dump cooled nozzle extension.

The LOX and LH2 propellant valves for the Ariane 5 main stage are also manufactured and produced at the Ottobrunn Production Centre.

The HM-7 rocket engine feature Ottobrunn's unique regenerative cooling technology whereby hydrogen propellant is efficiently used to cool the combustion chamber before being injected for combustion.

Important principles used in the HM-7 combustion chamber were adopted by NASA under licence and it is this technology that formed the basis of today's US space shuttle main engines - the first reusable rocket engine in the world.

HM-7 Combustion Chamber

The HM7 engine was built upon the development work of the 40kN HM-4 engine. In 1973, the Ottobrunn team started development of the HM-7 thrust chamber for the third stage of Ariane 1. Six years later, the HM-7 engine was successfully qualified with the first launch of Ariane 1 in December 1979.

With the introduction of Ariane 2 and Ariane 3, it became necessary to increase the performance of the HM-7 engine. This was achieved by raising the combustion chamber pressure from 30 to 35 bar and extending the nozzle, thereby raising the specific impulse. The burn time was also increased from 570 to 735 seconds. The upgraded engine was thus designated HM-7B and was qualified in 1983. When subsequently used on Ariane 4, the burn time was increased to 780 seconds.

In February 2005, the HM-7B successfully powered the new cryogenic upper stage of Ariane 5, designate ESC-A (Etage Superieur Cryotechnique A). This flight was a tribute to the performance and flight proven reliability of an engine first developed 30 years ago. With the ESC-A upper stage, the payload performance of Ariane 5 is increased to 10 tonnes. In order to inherit the proven reliability of the HM-7B engine from over one hundred Ariane 4 flights, engine changes were kept to a minimum. The main change being a 20% increase in burn time from 780 seconds to 950 seconds on Ariane 5 ESC-A.

Use of HM-7B on Ariane 5 is a first step toward increasing the payload performance of Ariane 5. A second step will be the introduction of the new Vinci expander cycle engine to an ESC-B cryogenic upper stage, increasing the payload performance to 12 tonnes.

Contact Us
If you require more detailed information on any of our products or services, then please contact us, indicating your particular areas of interest or intended application. Your enquiry will receive our best attention.