2 Pressure Fed Cycle Advantages Simple, reliable design No turbo pump DisadvantagesLimited to small tb, low thrustOnly limited throttlingTanks must withstand high pressureTank bladders might be requiredUsed in space vehicle attitude control, apogee enginesFuelOxid.He, N2High Pressure Gas Source
3 Gas Generator Cycle (GG) Open Cycle – Turbine exhaust doesn’t go thru main chamberGG burns non-stoichiometric to eliminate turbine coolingAdvantagesFairly simpleWide thrust operating rangeDisadvantagesTurbine exhaust gives low Isp – and effective loss in performanceGas generator requiredRS-27, MA-5, STME, Titan
4 Gas Generator Cycle Rocket Engine Fuel TurbineOx. Turbine
8 Combustion Tap-Off Cycle Open cycle similar to GG, but uses chamber gases instead, to drive turbine.AdvantagesNo gas generator requiredDisadvantagesDifficult to start and throttleNarrow thrust operating rangeHot gas valves requiredJ-2, Saturn V
10 Coolant Bleed CycleOpen cycle similar to combustion tap-off, but this time we use coolant bleed (vaporized) to run the turbines.AdvantagesNo gas generator neededDisadvantagesLimited to cryogenic fuelsPressure and thrust limited by fuel thermal properties
11 Expander CycleClosed cycle; most of coolant is fed to the low pressure ratio turbines.AdvantagesGood performance (i.e., closed cycle efficiency)Simple design, low weight, wide thrust operating rangeDisadvantagesLimited to low chamber pressure (< 1100 psi)Limited to cryogenic fluidUsed in RL-10
13 Staged Combustion Cycle Closed cycle with high flow pre-burner replacing gas generatorAdvantagesHigh performanceHigh chamber pressure and thrust capabilityDisadvantagesVery complex, with lower reliabilityAdvanced turbine, and pumps required for high Pc (boost pumps)Used in SSME, LE-7
14 Dual Preburner Fuel Rich SC Cycle Rocket Engine SSME Type Good MR and thrust level throttling characteristics
15 Single Preburner Fuel Rich SC Cycle Rocket Engine Better reliability than dual PBs.
16 Full Flow SC Cycle Rocket Engine Dual preburner with like on like MR eliminates key failure modes in turbomachinery and repress systems.
17 Single Preburner Oxidizer Rich SC Cycle Rocket Engine Ox rich preburner eliminates sooting issue in turbopump drive turbine. Significant advantage for reusable application.
20 SSME With Identified Components OxidizerPreburnerHigh-PressureOxidizer TurbopumpLow-PressureFuel TurbopumpControllerPropellantValvesHydraulicActuatorsNozzleMain CombustionChamberHot GasManifoldFuel PreburnerSSME Main InjectorAssembly
21 Liquid Main Engine Cycle Options A number of thermodynamic cycle options existWhich one used depends on applicationOne cycle is not RIGHT for every applicationTable below shows comparison of cycle complexities
23 Example ExerciseApplication: Expendable launch vehicle using LOX/ RP-1 for the booster engine. Vehicle needs relatively high performance (Isp > 310 sec vacuum). Using the trade tree below, select the appropriate engine cycle and provide your rationale. Use the data provided earlier in this presentation to justify your rationale.Engine Cycle TradeGG cycleExpanderTapoffStaged CombustionFuel Rich Single PBOx Rich Single PBOx Rich GGFuel Rich GGRP-1 CoolingLox CoolingFull Flow Dual PBFuel Rich Dual PB