– Goals –

Nowadays, chemical propulsion is based on solid (launch applications like first stage booster) or liquid technologies (primary stages, upper stage engines). Complementary, hybrid propulsion technology, as defined in ORPHEE (Operational Research Project on Hybrid Engine in Europe), appears as a new generation of advanced space transportation system. Engines based on this innovative propulsion concept can provide advantages like thrust performance, throttling (thrust modulation), versatility (easy adaptation to various configurations), simplicity, safety.

It will help to consolidate the long term sustainability and ensure a technology needed by the European propulsion space community to remain independent.

Hybrid propulsion principle is based on the injection of a liquid or gaseous oxidizer into the engine combustion chamber where it reacts with a solid fuel to generate hot gases providing the thrust. Enlarging the burning surface is the current proposed solution to reach the needed performance level. It dramatically increases the solid grain volume and the engine weight, limiting the applications. The regression rate is a key parameter controlling the solid fuel grain design. Its increase is a very attractive solution to reduce the grain volume.

The main objectives of ORPHEE are to increase versatility of space propulsion systems, to ensure a significant increase in the performance of a hybrid engine, to improve the solid fuel technological maturity from TRL 1 to 3, to gather the European skills on hybrid propulsion and to ensure European access to space.

In near future, the availability of new hybrid engines will allow the access to new space transportation missions. By consolidating the knowledge on this innovative technology and by implementing solutions in upcoming space agencies roadmaps, the European space propulsion community will strengthen its global competitiveness.