DEVELOPMENT OF P4.1 ALTITUDE SIMULATION FOR VINCI® ENGINE K. Schäfer, C. Böhm, H. Kronmüller, H. Zimmermann, German Aerospace Centre (DLR), Institute of Space Propulsion, Lampoldshausen, 74172 Hardthausen, Germany 1 ABSTRACT pean launcher programs and one of its main tasks has always been high altitude testing of To test rocket propulsion systems as much as rocket engines. possible under operational conditions are one of The P4 test facility with two test positions P4.1 the main drivers for flight qualification. For up- and P4.2 was build in the mid-sixties for the per stage engines the tests in vacuum conditions ELDO program. In 1973 when the ARIANE with fully expanded nozzle defines the essential launcher program started the P4 was equipped criteria for altitude simulation test facilities. for altitude simulation tests of the VIKING en- SNECMA is developing a new upper stage en- gine with 80 t vacuum thrust. ® gine called VINCI . For the engine tests the ex- With the development of the ARIANE 5 the isting test bench P4.1 at the DLR test centre P4.2 was adapted in 1992 to the altitude simula- Lampoldshausen was adapted to high altitude tion of the AESTUS upper stage engine. conditions. To maintain the experience of the test facility ® VINCI is an Expander cycle-type engine with engineering and to improve the altitude simula- up to 180 kN thrust. An extendable nozzle will tion especially the development of rocket steam ® give VINCI a specific impulse of 465 s in vac- generators the department of engineering was uum. founded in 1996 within the institute of space The task of altitude simulation consists of creat- propulsion. ing the test condition within a vacuum cell. This In 1998 the decision was taken to modify the is primarily low ambient pressure of just few existing test position P4.1 for the VINCI® de- mbar. Special operational conditions are linked velopment tests. Since February 2005 the test to the transients during Start-Up and Shut-Down bench is operational (FIG. 1). of the engine with respect to the nozzle loads. Maintenance of the vacuum with running engine is achieved by recompression of the supersonic exhaust jet in a diffuser and the extraction of the exhaust gas by steam jet ejectors. To provide the large quantities of steam, rocket steam generators with liquid Oxygen and Alco- hol are used. The maximum flexibility is reached by adapta- tion of the test bench to the different engine configurations and the test conditions. This con- tents modular systems. FIG. 1: P4.1 ALTITUDE SIMULATION 2 INTRODUCTION P4.1 is now the larges altitude simulation test From the very beginning in the 1960s, DLR facility in Europe. Lampoldshausen has been involved in all Euro- − Ballistic phase and reignition in vacuum 3 TEST REQUIREMENTS conditions. ® The VINCI engine (FIG. 2) will be tested in 3 4 DEVELOPMENT OF P4.1 ALTITUDE configurations (Table.1). SIMULATION Configuration The development of the altitude simulation was done in different phases: I Combustion Phase 1: Basic studies and general lay out. Chamber Phase 2: Development of basic components II Combustion − Centre Body Diffuser Chamber and − Rocket Steam Generators Fix Nozzle − Ejector System − Modular system to different test configura- III Complete tions. Engine with Phase 3: Final lay out of the test bench. Extendable Nozzle 5 STUDIES AND GENERAL LAY OUT (PHASE 1) FIG. 2: VINCI ENGINE The basic studies are performed to define the VINCI Test Expansion Ratio ε principal conditions and dimensions of the Configuration Length l [m] Exit Diameter Ø [m] components, particularly the super sonic dif- fuser and the dimensioning of the suction sys- Configuration Combustion chamber I ε = 22,3, l ∼ 1,4 m, Ø∼ 0,7 m tem with adapters for the different test configu- rations. Configuration Chamber with the fix nozzle II ε =93, l ∼ 2,2 m, Ø∼ 1,4 m Centre Body Diffuser: Due to the limited high Configuration Complete engine with the extendable of the existing P4.1 building a centre body dif- III nozzle fuser was chosen with reduced length. ε = 243, l ∼ 4,2 m, Ø∼ 2,3 m ® The centre body diffuser has the same behaviour TABLE 1: VINCI TEST CONFIGURATIONS like a second throat diffuser. The supersonic flow is stable down to lower pressures ratios The P4.1 test conditions are: (Hysteresis). The length L to diameter D ratio − Vertical test position with maximum test should be 6 < L/D < 8 for reduced pressure time of 770 s. losses. The second throat is realised by a ring − Pressure at engine interface during chill channel around a centre body. The overall down p < 200 mbar. length of the diffuser is short because of the re- − Ignition at ambient pressure p < 60 mbar duced hydraulically diameter of a ring channel. The centre body has to be cooled intensively. − Start up phase with simulation of in-flight engine start up conditions The main parameters for the centre body dif- fuser design were linked to the characteristics of − Steady state phase with the operational enve- the combustion chamber pressure Pc, the ex- lope in vacuum conditions pandable nozzle with the expansion ratio ε = − Shut down phase with transient conditions 243, the heat loads and the given dimensions of considering the maximum nozzle loads P4.1. Suction system: The main parameters for the suction system were linked to the transient pres- Phase 1 Procedure sure conditions during Start-Up and Shut-Down Studies and General Layout of the engine. The trade-off was between pow- P4.1 Altitude Simulation erful ejectors with high steam consumption for fast transients and a big condenser with high Basic Studies cooling water flow. Adapters: The adapter for combustion chamber tests is designed as a short diffuser and for Gim- balling. The adapter for the fix nozzle replaces Step 1 Geometrical Data the extendable nozzle and guides the exhaust to the centre body diffuser. Main drivers were: Design of Interface Components Adjustments − Consumption of steam for the sizing of the rocket steam generator plant. − Ignition and reignition conditions. Step 2 − Consumption of cooling water for the sizing Cross Check of the cooling water plant, the underground storage and the condenser. First Lay Out Check of − The transient behaviour of the engine re- Altitude Simulation Characteristics quires the supersonic Start and Un-Start of the diffuser at low combustion chamber pres- sures to prevent the back flow of hot gases. Step 3 Check Reliability − Flexibility to adapt the altitude simulation to the test configurations by short notice. − Reliability of the altitude simulation Design Check of Altitude Simulation Sensitivity/Margins The altitude simulation has been achieved by an experienced calculation process. The general General Design way of calculation (FIG. 3) consists of three Altitude Simulation steps. FIG 3: CALCULATION PROCESS Step 1: A forward calculation, to determine geometric parameters from input parameters, Test Phase Combustion Vacuum represents the first step. pressure [bar] chamber [mbar] Step 2: The second step is like a cross-check Chill down - < 40 procedure by a backward calculation, receiving (< 200 at chill down the characteristic curve from geometric parame- Interface) ters. Ignition - 25 - 40 Step 3: Finally in a third step, the sensitivity to Start 10 – 15 < 60 parameter-variations is evaluated to check the Diffuser reliability of the prediction. Steady 25 – 80 2,5 - 7 To get the required accuracy, the steps are ad- State justed by experienced loss- and gain- UN Start 10 – 20 < 80 parameters, which depends on type and basic Diffuser configuration. The result arises iteratively by TABLE 2: PARAMETERS ε = 243 CONFIGURATION this way. LOX buffer LH2 buffer LOX runtank vacuum chamber P4.1 ejectors N2 / He panels VINCI engine P4.1 condenser center body diffuser P4.2 condenser deflector chill down ejectors sea level configuration vacuum flap first ejector stage steam lines underground 0 1 5 10 m water reservoir FIG 4: GENERAL DESIGN P4.1 The general design (FIG. 4) is: down against higher pressure of the con- − Feed System with run tanks for LH2 and denser. LOX designed for chill down and 770 s hot − A big condenser reduces the mass flows to be run. sucked by the end stage ejector to ambient − Buffer tanks for LH2 and LOX to simulate pressure conditions. The water is routed the dynamical transient feeding conditions of barometrically to an underground water res- the stage during Start up and Shut Down ervoir maintaining the vacuum pressure in- side the condenser. − The VINCI engine is vertically mounted in- side a vacuum chamber within a thrust meas- − The “chill down” ejectors maintain the vac- urement device. uum simulation during the cool down phase of the engine before ignition. − The supersonic exhaust jet will be recom- pressed inside the centre body diffuser to subsonic conditions. 6 DIFFUSER SUBSCALE TESTING − The heat loads of the hot gases will be re- (PHASE 2) duced by water injection after the diffuser. All parts up to the vacuum flap are double CFD calculations and model tests under cold wall water cooled. The exhaust gases are and hot conditions were performed to verify the guided to the first ejector stage by the deflec- heat loads and functional behaviour of the cen- tor. tre body diffuser. − The first ejector stage maintains the pressure conditions during Ignition, Start up and Shut 6.1 SUBSCALE DIFFUSER COLD GAS Different diffusers were tested for basic investi- TESTS gations (fig. 8). The results show a supersonic Start and Un-Start of the centre body diffuser at The test position P6.2 (fig. 5) has been devel- low ratios of chamber pressure to vacuum pres- oped and erected to investigate components for sure.