Encyclopedia Astronautica
HM7-B


SEP, Ottobrunn lox/lh2 rocket engine. 70 kN. Isp=447s. 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.

With the introduction of Ariane 2 and Ariane 3, it became necessary to increase the performance of the HM-7 engine. This was achievd 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 designated HM-7B and was qualified in 1983. The HM-7 engine versions have reliably powered the third stages of Ariane's 1 through 4 from 1979 to 2003.

The HM-7B engine, was also ntegrated from the third stage of Ariane 4 into the new Ariane 5 cryogenic upper stage - a tribute to the performance and flight proven reliability of an engine first developed 30 years earlier. The resulting upper stage was designated ESC-A (Etage Superieur Cryotechnique A) and increased the performance of Ariane 5 to 10 tonnes.

Use of HM-7B on Ariane 5 was a first step toward increasing the launcher's payload performance. A second step was the introduction of the new Vinci expander cycle engine to a new cryogenic upper stage, increasing the payload performance to 12 tonnes.

The Ottobrunn facility was responsible for the development and manufacture of the HM-7B thrust chamber comprising the regeneratively cooled combustion chamber, coaxial propellant mixing injectors, dump cooled nozzle etension, gimbal joint, and the LOX and LH2 propellant valves.

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

Thrust (sl): 43.600 kN (9,802 lbf). Thrust (sl): 4,444 kgf. Engine: 155 kg (341 lb). Chamber Pressure: 35.00 bar. Area Ratio: 83.1. Thrust to Weight Ratio: 41.2516129032258. Oxidizer to Fuel Ratio: 5.14. Coefficient of Thrust vacuum: 1.89575424141004.

Unfuelled mass: 155 kg (341 lb).
Height: 1.80 m (5.90 ft).
Diameter: 1.00 m (3.20 ft).
Thrust: 70.00 kN (15,736 lbf).
Specific impulse: 447 s.
Specific impulse sea level: 310 s.
Burn time: 731 s.
Number: 142 .

More... - Chronology...


Associated Countries
See also
Associated Launch Vehicles
  • Ariane 2/3 French orbital launch vehicle. Improved version of the Ariane 1. It featured increased thrust first and second stage engines, a 25% stretched third stage, 4 seconds specific impulse improvement in the third stage, a larger internal payload fairing volume, and introduced the Sylda payload carrier for dual payloads. The Ariane 3 version added two solid rocket motor strap-ons. Development was authorised in July 1980 and had a total cost of 144 million 1986 Euros. More...
  • Ariane 4 French orbital launch vehicle. The ultimate Ariane development. Compared with the Ariane 2/3, the Ariane 4 featured stretched first (61%) and third stages, a strengthened structure, new propulsion bay layouts, new avionics, and the Spelda dual-payload carrier. The basic 40 version used no strap-on motors, while the Ariane 42L, 44L, 42P, 44P, and 44LP versions used varous combinations of solid and liquid propellant strap-on motors). Development was authorised in January 1982, with the objective of increasing payload by 90%. Total development cost 476 million 1986 ECU's. More...
  • Ariane 44LP French orbital launch vehicle. Ariane 4 with 2 liquid rocket + 2 solid rocket strap-ons. More...
  • Ariane 44L French orbital launch vehicle. Ariane 4 with 4 liquid rocket strap-ons. More...
  • Ariane 42P French orbital launch vehicle. Ariane 4 with 2 solid rocket strap-ons. More...
  • Ariane 44P French orbital launch vehicle. Ariane 4 with 4 solid rocket strap-ons. More...
  • Ariane 42L French orbital launch vehicle. Ariane 4 with 2 liquid rocket strap-ons. More...

Associated Manufacturers and Agencies
Associated Propellants
  • Lox/LH2 Liquid oxygen was the earliest, cheapest, safest, and eventually the preferred oxidiser for large space launchers. Its main drawback is that it is moderately cryogenic, and therefore not suitable for military uses where storage of the fuelled missile and quick launch are required. Liquid hydrogen was identified by all the leading rocket visionaries as the theoretically ideal rocket fuel. It had big drawbacks, however - it was highly cryogenic, and it had a very low density, making for large tanks. The United States mastered hydrogen technology for the highly classified Lockheed CL-400 Suntan reconnaissance aircraft in the mid-1950's. The technology was transferred to the Centaur rocket stage program, and by the mid-1960's the United States was flying the Centaur and Saturn upper stages using the fuel. It was adopted for the core of the space shuttle, and Centaur stages still fly today. More...

Associated Stages
  • Ariane H10 Lox/LH2 propellant rocket stage. Loaded/empty mass 12,000/1,600 kg. Thrust 62.70 kN. Vacuum specific impulse 446 seconds. More...
  • Ariane H10-3 Lox/LH2 propellant rocket stage. Loaded/empty mass 12,310/1,570 kg. Thrust 62.70 kN. Vacuum specific impulse 446 seconds. More...
  • Ariane 5 ESC A Lox/LH2 propellant rocket stage. Loaded/empty mass 16,500/2,100 kg. Thrust 64.70 kN. Vacuum specific impulse 446 seconds. Uses engine and oxygen tank from Ariane 4 + new liquid hydrogen tank. More...
  • Ariane H10plus Lox/LH2 propellant rocket stage. Loaded/empty mass 12,800/1,740 kg. Thrust 62.70 kN. Vacuum specific impulse 446 seconds. More...

Home - Browse - Contact
© / Conditions for Use