Rocket Engines and
Thrust Chambers

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

Vulcain Rocket Engine - Thrust Chamber

The Ariane 5 cryogenic propellant core stage engine.

Snecma's Vulcain rocket engine powers the cryogenic core stage of Ariane 5. A more powerful engine, Vulcain 2 is currently in use after being validated on Ariane 5 ECA flight 521, launched on 12 February 2005.

Vulcain (also known as HM-60) was the first main engine of the Ariane 5 cryogenic first stage (EPC). The Ottobrunn facility of EADS Astrium is responsible for the development and production of the Thrust Chamber, comprising:

	Cardan (gimbal joint, connection to the stage; manufactured by MT Aerospace)
	Injector head with coaxial twin propellant injection elements
	Combustion Chamber (regenerative cooling circuit)
	Nozzle Extension (active cooled by dump flow; manufactured by Volvo Aero Corporation)

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

In total 56 Vulcain thrust chambers have been manufactured at the Ottobrunn Production Centre during the development and production period until mid 2009.

During 22 successful flights, Vulcain always performed flawlessly. The last flight of Ariane 5 using the Vulcain engine is currently foreseen for late 2009.

Vulcain has been used in the G, GS and G+ configurations of Ariane 5. Perhaps the most spectacular flights using a Vulcain engine have been the successful launches of the XMM-Newton Spacecraft (X-ray space observatory) on 10 December 1999 and the Rosetta spacecraft on 2 February 2004, which left Earth orbit for rendezvous with comet 67P/Churyumov-Gerasimenko).

Thrust Chamber Design
The thrust chamber design is based on the regenerative cooling concept that was developed at Ottobrunn and has since been continually refined.

Before combustion, LH2 is pumped into a distribution manifold and then flows through closely arranged small tubular cooling channels within the combustion chamber wall. The LH2 then enters an injector head where it is uniformly distributed to 516 coaxial injector elements.

The coaxial injector elements cause the LOX and LH2 propellants to be mixed together. LOX is injected at the centre of the injector, around which the LH2 is injected. These propellants are mainly atomised and mixed by shear forces generated by the velocity differences between LOX and LH2. Although the injector design is complex, it does assure consistent and reliable combustion efficiencies greater than 99 %, which are reached in the remaining process in the combustion chamber.

Vulcain Injector and Combustion Chamber Head

In the combustion chamber, the mixed propellants are burned and accelerated up to sonic conditions. The combustion temperatures in the chamber almost reach almost 3250 °C at pressures of 100 bar.

Combustion temperature control is achieved by the flow of LH2 in the cooling channels within the combustion chamber wall. This thin copper alloy wall, just 1 mm thick near the throat, separates the combustion temperatures from the - 239 to - 150 °C LH2 cooling flow.The final acceleration of hot gases, up to supersonic velocities, is achieved by gas expansion in the nozzle extension, thereby increasing the thrust.

Movies
The Vulcain thrust chamber operation can be viewed on this movie. (German language mpg file).
The Vulcain, together with other rocket engines on hot-fire testing at Lampoldshausen, can be seen on this movie (mpg)