AESTUS: Upper Stage Engine Space Transportation

All the space you need AESTUS: Upper Stage Engine

Bipropellant upper stage engine for the orbital insertion of heavy payloads The Aestus powers the Operation 5 ES and GS version The Aestus thrust chamber design is bipropellant upper stage for the based on the regenerative cooling insertion of payloads into LEO, SSO principle. Prior to combustion, and GTO. For the ES version, Aestus MMH fuel is pressurised into a usesits re-ignition capability to place distribution manifold causing the ESA's 21 tonne Automated Transfer fuel to flow through narrow, closely Vehicle(ATV)intoalowEarthorbit. arranged channels in the Aestus is a pressure fed engine that combustion chamber wall, consumes up to 10 tonnes of the configured to cause a highly efficient bipropellant combination cooling. The MMH then enters the MMH/N2O4. injector head which assures uniform Aestus was developed at the propellant flow rate distribution over Ottobrunn Space Propulsion Centre 132coaxialinjectionelements. during the period 1988 - 1995. The The unique design of the injection first operational flight of Aestus was element as well as the proper on flight 502, launched on element distribution along the 30thOctober1997. injector face cause swirl mixing and Aestus/Ariane 5 upper stage engine Together with the Aestus engine, atomisation of the propellants EADS is responsible for the enabling combustion efficiencies in complete Ariane 5/EPS upper stage, thechamber in excessof 98%during under contract with ESA, with the theremainingcombustionprocess. technicaladvice ofCNES. Upon leaving the injector elements Major Sub-Assemblies and entering the combustion chamber, the hypergolic propellants ? Injector with coaxial injection spontaneously ignite and are burned elements for the mixing of and accelerated up to sonic propellants. conditions at the throat. The ? Combustion chamber combustion temperature in the regenerativelycooledbyMMHfuel. combustion chamber reaches about 3000 K at a combustion pressure of ? Nozzle extension, radiatively 11bar. cooled. Controlling the hot gas wall and ? Propellant valves for fuel and MMH coolant temperature levels oxidiser, pneumatically operated by under the high operating pilotvalves. combustion chamber heat fluxes ? Gimbal joint mounted at the top of was one of the most challenging theinjectordome. tasks that had to be overcome during ? Electromechanical gimbal the development phase. A further actuators for pitch and yaw engine challenging task was the control. development of a new injector EPS/Ariane 5 Upper stage element for MMH /N2O4, using the with Aestus engine Some subassemblies have been same, highly efficient, coaxial subcontracted to partners including injection principle used on all of our the gimbal joint to NAMMO Raufoss cryogenicthrustchambers. (Norway), the nozzle extension to Franke AG (Switzerland), the After leaving the combustion propellant valves to MOOG chamber, the final acceleration of (Germany and USA), the flexible hot gases up to supersonic velocities propellant lines to Witzenmann is achieved by gas expansion in the (Germany) and the helium filter to radiatively cooled nozzle extension, Rellumix(France). therebydeveloping thrust. AESTUS: Upper Stage Engine

Proven Design and Performance flight 518, launched on 26 February Flexibility 2004. The Aestus rocket engine has proven During the period 2003 - 2007, the to be a robust and flexible design, Aestus engine underwent a re- evolving harmoniously with the ignition qualification programme in evolution of Ariane 5 and its various readiness for the first launch of the missions, as shown in the Aestus Automated Transfer Vehicle. The in- DevelopmentHistorybelow. orbit re-ignition capability of Aestus In addition, by varying the number of was subsequently demonstrated coaxial injector elements, the basic during the first launch of ATV Aestus design can be used for higher, aboard Ariane 5 flight 528, launched orlowerthrustapplications. on9March2008. A engine demonstrator During ATV mission, the first Aestus version, known as the RS 72/Aestus ignition occurs immediately after 2, was derived from the Aestus separation of the upper stage engine. This so called Pathfinder composite from the cryogenic main engine has been hot-fire tested in stage. At the end of the first burn, a cooperation with Boeing ballistic phase commences for about (Pratt&Whitney). 45 minutes. A second ignition then provides a short duration burn for Aestus Development History Assembled Thrust Chamber of the injecting the ATV into its target Low Aestus engine The Aestus rocket engine was Earth Orbit after separation from the developed at the Ottobrunn Space upper stage. A third and final Propulsion Centre during the period ignition is then used to de-orbit the 1988 - 1995. The first flight with depleted upper stage into a safe re- Aestus under operation was on entry trajectory for burn-up in the Ariane 5 flight 502, launched on 30th upperatmosphere. October1997. With its proven flexibility and In the frame of performance multiple re-ignition capabilities, the improvements to the complete upper Aestus engine enables a stage, a delta-qualification considerable range of mission programme was performed in 1999 - specific profiles for the Ariane 5 2002. Here, the propellant mixture launcher. Ariane 5 ES (with Aestus) ratio of Aestus was adjusted from is a suitable launcher also for low 2.05 to 1.9. Subsequently, the first earth operation missions, e.g. operational flight of the performance Galileo. enhanced Aestus was on Ariane 5

Propellants N24 O \MMH Specific impulse vacuum 324 s Thrust vacuum 29.6 kN Propellant mass flow rate 9.3 kg/s Mixture ratio (TC) 1.9 Engine feed pressure 17.7 bar Vacuum Test Platform P4.2 of Combustion chamber pressure 11 bar Aestus at DLR, Lampoldhausen Nozzle area ratio 84 Nozzle exit diameter 1.31 m Overall engine length 2.2 m Thrust chamber mass 111 kg Nominal single firing 1100 s Power 43,700 kW 59,400 hp Re-ignition capability Multiple ASTRIUM Space Transportation Propulsion & Equipment D 81663 Munich, Germany Phone: +49 89 607 32480 Fax: +49 89 607 85480 [email protected] www.space-propulsion.com www.astrium.eads.net

Thanks to DLR and ESA for their information and pictures