New generation of low thrust bi-propellant engines in qualification process

Abstract

On the basis of more than 200 successfully operating bi-propellant engines of the fust generation in orbit DASA is now in qualification process on ground of the second generation This new family of satellitelspaceprobe and orbit insertiodcorrection engines offers several advantages like performance improvement, pulse mode improvement and enlarged operation range. Three different thrust levels are represented by this new family: -4 N thruster for attitude control with main interest on high accuracy minimum impulse bit 10 N thruster for orbit correction and/or insertion support with concentration on high specific performance and very long burning time for injection backup capability 400 N engine for orbit injection and/or correction with rather large thrust level hut low enough not to create too strong constraints to the spacecraft. The presentation will mainly concentrate on the qualification status of these new engines. This qualification demonstration will cover the whole hot f r h g specrmm as well as the environmental testing. This new generation differs from the first one in principle by two main characteristics:replacement of normal standard material by high temperature resistant material (without the need of surface coaelimination of regenerative cooling in the hottest area (nozzle throat).--ting)AU the other principles like swirl atomizing injector, film cooled combustion chamber, radiative cooled expansion nozzle as well as monostable thruster valve will remain nearly unchan-The 10 N thruster was the first item submitted to the introduction of this new generation of engines.During qualification under extreme conditions the regeneratively cooled 10 N thrusters showed limits in operation reaching high mixture ratio at high mass flow with the risk to reach thermal instability endangering the thruster life.The new generation allowed to increase the operation range into higher areas of mixture ratio and mass as well as down to lower values. At the same time the specific impulse and the minimum impulse hit could be improved as well The presentation will show the qualification test results with respect to long burning time (more than 50 hours), high number of duty cycles (more than 700.000 pulses) and comfonable resistance against environmental vibration loads.ged Following high accuracy requirements for attitude fine pointing DASA decided to decrease the thrust level for its bi-propellant thrusters as far as possible. This attempt ended up in the development of a 4 N thruster. For this thruster the presentation will also demonstrate the feasibility for long burning time (more than 40 hours), high number of duty cycles (more than 750.000 pulses), exeemely low minimum impulse bits (C 13 mNs) with very high reproduceability, high specific impulse during pulse mode operation and also comfortable resistance against environmental loads.The third member of the new bi-propellant thruster family of DASA is the 400 N engine mainly applied for apogee injection manoeuvres. Due to the much higher through-put of propellants ...