The Vulcain rocket engine powered the cryogenic core stage of Ariane 5. The Ottobrunn facility was responsible for the development and manufacture of the Vulcain thrust chamber comprising the regeneratively cooled combustion chamber, coaxial propellant mixing injectors, dump cooled nozzle extension, and gimbal joint. The LOX and LH2 propellant valves were also manufactured and produced at the Ottobrunn Production Centre.

The thrust chamber design was based on the regenerative cooling concept that was developed at Ottobrunn, since continually refined. Before combustion, LH2 was pumped into a distribution manifold and then flowed through closely arranged small tubular cooling channels within the combustion chamber wall. The LH2 then entered an injector head where it was uniformly distributed to 516 coaxial injector elements.

The coaxial injector elements caused the LOX and LH2 propellants to be mixed together. LOX was injected at the centre of the injector, around which the LH2 was injected. These propellants were mainly atomized and mixed by shear forces generated by the velocity differences between LOX and LH2. Althought the injector design was complex, it assured consistent and reliable combustion eficiencies greater than 99 %, which were reached in the remaining process in the combustion chamber.

At the combustion chamber, the mixed propellants were burned and accelerated up to sonic conditions. The combustion temperatures in the chamber almost reached 3250 degrees Celcius at pressures greater than 100 bar.

Combustion temperature control was achieved by the flow of LH2 in the cooling channels within the combustion chamber wall. This thin copper alloy wall, just 1.5 mm thick separated the combustion temperatures from the - 239 to - 120 degree Celcius LH2 cooling flow.

The final acceleration of hot gases, up to supersonic velocities, was achieved by gas expansion in the nozzle extension, thereby increasing the thrust.

Vulcain 2 was the new generator cycle rocket engine for an Ariane 5 core stage upgrade. By making design enhancements to the Vulcain 1 engine and introducing innovative production technologies, the thrust of Vulcain 2 was increased to 135 tonnes - an increase of more than 30% compared to its predecessor. Vulcain 2 would increase the payload capacity of Ariane 5 to 6.8 tonnes and increase the engine's specific impulse by 3 seconds over the basic model. This was achieved by increasing the O:F ratio to 6.3, increasing the expansion ratio by 30%, and exhausting turbine gases into the exit cone of the engine. Seven Vulcan-2 were built for running at test stand P5 in Lampoldshausen and PF50 at Vernon between April 30, 1999 and the end of 2001.

As with Vulcain 1, the Ottobrunn facility was responsible for the development and manufacture of the Vulcain 2 thrust chamber comprising the regeneratively cooled combustion chamber, coaxial propellant mixing injectors, dump cooled nozzle extension, and gimbal joint.