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Vulcain 2 Rocket Engine - Thrust ChamberThe latest version of the Ariane 5 cryogenic propellant core stage engine.Snecma's Vulcain 2 is a new gas generator cycle rocket engine that currently powers the Ariane 5 ESC core stage. As with Vulcain 1, the Ottobrunn facility of EADS Astrium is responsible for the development and production of the Vulcain 2 thrust chamber comprising:
The LOX and LH2 propellant valves for the Ariane 5 main stage are also manufactured and produced at the Ottobrunn Production Centre. Developed as part of ESA's Ariane 5 Evolution Programme, Vulcain 2 introduces an improved Injector design, increased combustion chamber pressure and a modified nozzle extension design. These improvements enable Vulcain 2 to provide Ariane 5 with 30% more power compared to its predecessor. This performance increase, together with the use of the HM-7 engine on the upper stage, enables a payload gain from 6 tonnes on the generic version of Ariane 5, to 10 tonnes on the Ariane 5 ECA. Today, Vulcain 2 is used in the ECA and ES ATV versions of Ariane 5. In the future Vulcain 2 is also planned for use with Ariane 5 ECB, which will introduce the new upper stage Vinci engine (currently under development). Vulcan 2 was first qualified of Ariane 5 ECA flight 164, launched on 12 February 2005. By the end of 2008, 38 Vulcain 2 engines had been produced and delivered by the Ottobrunn Production Centre. One of the most spectacular flights using a Vulcain 2 engine was the successful launch of the Automated Transfer Vehicle, Jules Verne, on 9 March 2008.
New Thrust Chamber Design Firstly, a new injector head was designed with a flow optimised LOX dome predistributor plate and 566 high performance coaxial injector elements. Each injector element features body brazed LOX post, multi hole hydrogen sleeve incorporating over 80,000 individual inlet orifices, as well as 75 wall adjacent slots enabling 1.7% of the hydrogen propellant to enter the combustion chamber as film coolant. a second feature is a new Vulcain 2 thrust chamber liner design which features 468 individual high aspect ratio cooling channels, precision milled with a wall thickness of 0.7 mm at the chamber throat. The cylindrical section of the combustion chamber has been elongated by a factor of almost three to provide for complete gasification and burning of the increased amount of liquid oxygen. To protect the copper liner against oxygen degradation effects, such as blanching, wall film cooling has been employed from the injector face plate down to the nozzle throat section. The overall dump cooled nozzle extension used on Vulcain 1 has been replaced by a completely new nozzle design that provides for dump coolant injection at an area ratio of 29.2 and turbine gas injection at an area ratio of 32. This new nozzle design enables Vulcain 2 to deliver a specific impulse of 429 sec. 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 during the remaining process in the combustion chamber. In the combustion chamber, the mixed propellants are burned and accelerated up to sonic conditions. The combustion temperatures in the chamber reach almost 3250 °C at pressures greater than 100 bar. Combustion temperature control is achieved by a flow of LH2 in the cooling channels within the combustion chamber wall. This thin copper alloy wall, just 1.5 mm thick 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.
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