Low Ambient Pressure Injection and Consequences on Ignition of Liquid Rocket Engines

In the frame of a test campaign conducted to assess the feasibility of laser ignition for implementation on cryogenic RCS (Reaction and Control System) and OMS (Orbital and Manoeuvring System) engines, fluid flow structures and phenomena affecting ignition have been examined. This paper presents a qualitative analysis of the impact of pre-ignition pressures, of propellant injection conditions and injection phenomena such as flash evaporation, of the local chamber flow field, and of propellant mass flow stability on altitude ignition. The use of test sequences and encountered phenomena to control the ignition delay and energy deposition and ignition overpressure is addressed. A separate paper has been dedicated to the discussion of minimum laser energies measured and ignition probabilities in the here described flow fields