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The European ARIANE 5 launcher is designed to put a payload mass of about 6.0 t into geostationary transfer orbit. It consists of a lower central stage with two solid propellant strap-on boosters and a single-engined storable propellant upper stage. The ARIANE 5 was successfully launched on October 30th, 1997. This paper deals with the thermal protection of the ARIANE 5 upper stage. The tanks, the actuators, the instrumentation and electronic equipment have to be protected from the heat input of the hot engine nozzle during the 1100 second thrust phase and maintained operational for a further time period for passivation or re-ignition of the engine. The paper provides a short history of the upper stage development and the thermal design for the configuration of the qualification flights. For the production phase the optimization potential with regard to mass saving and simplified integration has been investigated.

The new European ARIANE 5 launcher being designed to put a payload mass of 6.8 t into geostationary transfer orbit is scheduled to be operational in 1995. It consists of a lower central stage with two solid propellant strap-on boosters and a single-engined storable propellant upper stage. The ARIANE 5 upper stage tank section has to be protected from the heat input of the hot engine nozzle during the 800 second firing period. Furthermore, the tank section and its components have to be thermally controlled for up to 3 hours after upper stage firing in order to maintain all equipment in an operational condition for possible passivation of the stage or re-ignition of the engine. This paper describes the thermal protection system development program with emphasis on the heat shield. The optimization process is shown starting with material selection combined with analysis and is followed by test verification. The foreseen manufacturing and integration approach is outlined as well.