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Rocket Propulsion OverviewSeitzman Rocket Overview-1Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.AE6450 Rocket PropulsionRocket DefinitionRocket Device that provides thrust to avehicle by accelerating some matter (thepropellant) and exhausting it from therocket– Most significant difference betweenrocket and air-breathing engines isthe rocket carries all its ownpropellantSeitzman Rocket Overview-2Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.AE6450 Rocket Propulsion1

Rocket: Performance Issues Thrust– Impulse– important when there are minimum allowableacceleration requirements, e.g., launch ingravity field F((t)t )dtmeasure of rocket performance – usuallynormalized by mass of propellant required(specific impulse, Isp)Other issues–structural weight, size, complexity, reliability, AE6450 Rocket PropulsionSeitzman Rocket Overview-3Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.Rocket Propulsion ElementsPropellantEnergy Sourcegas, liquid, solidchemical, pressure,nuclear, radiation (solar)StorageStoragesame in chemicalrocketsConversionFeed Systemto press., temp.,electricity, radiationfor gases/liquidsAcceleratorThermodynamic (pressurenozzle), electromagnetic(static, dynamic fields)Seitzman Rocket Overview-4Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.AE6450 Rocket Propulsion2

Examples: Pressure Rocket Cold Gas Thruster Cold gas (N2, hydrazine, )stored at high pressure withthrust provided by acceleration through nozzle– Propellant Energy source (storagepressure)– Feed system: piping from storage to nozzle– Accelerator: nozzle (thermal to kineticenergy)Seitzman Rocket Overview-5Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.AE6450 Rocket PropulsionExamples: Chemical Rocket Bipropellant: LH2-LOX (H2/O2) Combust pressurized H2and O2 in combustionchamber, nozzle exhaust– Propellant Energy source(chemical)– Storage: liquid (cryogenic)tanks– Feed system: liquid pumps and piping– Energy conversion: chemical to thermalenergy (combustion)– Accelerator: nozzleSeitzman Rocket Overview-6Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.SSMEAE6450 Rocket Propulsion3

Examples: Electrical Rocket Ion Engine Ionize neutral gas (Xe); ionsaccelerated by E field;ions recombined with e– Propellant: neutral gas– Energy source: e.g., nuclear– Energy conversion: nuclear tothermal to electrical– Accelerator: high voltageelectrostatic field acrosselectrodesAE6450 Rocket PropulsionSeitzman Rocket Overview-7Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.Applications Space Propulsion–––– Launch: from “planetary” body to orbitOrbit Insertion: from launch orbit to missionorbitManeuvering: maintain or change orbit ortrajectoryAttitude Control: orientation of vehicleAircraft Propulsion––High thrust/acceleration (sustained orboosters)High speed flight ( ramjet/scramjet capability)Seitzman Rocket Overview-8Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.AE6450 Rocket Propulsion4

Chemical Rockets Thrust produced by conversion of– chemical energy to thermal energy– thermal energy to kinetic energy Common Applications––Usual choice for high thrust rockets, e.g,launch, orbit change, aircraft propulsionAlso used for maneuvering and attitudecontrolSeitzman Rocket Overview-9Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.AE6450 Rocket PropulsionChemical Rockets – Types Gas rockets– fuel/oxidizer stored as gases large storagevolumesLiquid rockets– stored as liquids, more complex but high impulseSolid rockets– propellant is solid, lower impulse but simplerHybrid rockets– usually solid fuel liquid/gas oxidizerMotors vs. Engines––Motor propellant stored inside comb. chamberEngine storage outside combustion chamberSeitzman Rocket Overview-10Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.AE6450 Rocket Propulsion5

Chemical Rockets – Liquid System Primary subsystems– storage– feed system– thrust chamberassembly (TCA) IGNITERTCAStorageFeedSystemadapted from grc.nasa.govSeitzman Rocket Overview-11Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.from history.nasa.govAE6450 Rocket PropulsionChemical Rockets – Liquid Propellants Monopropellants– exothermic decomposition hydrogen peroxide H2O2 hydrazine N2H4 Bi-propellants– fuel/oxidizer combustion H2 / O 2 RP-1 (kerosene) / O2 MMH (CH3NH-NH2) / N2O4– hypergolic: self-igniting on contactSeitzman Rocket Overview-12Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.AE6450 Rocket Propulsion6

Chemical Rockets - Solidigniter Nothing but TCA Casing– coolingthroatgrainnot required,casinginsert nozzleprotected by propellant Grain– geometry (surface area/shape) of solid propellant– no feed system to control propellant flow rate,grain design to “program” burning rate – can bevery high Nozzle– no coolant available, higher T material requiredSeitzman Rocket Overview-13Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.AE6450 Rocket PropulsionChemical Rockets- Solid Propellants Homogeneous– fuel/oxidizer mixed at near molecular level Heterogeneous10 m– separate “fuel”and “oxidizer”– usually oxid.particles insolid binder AP/rubber AP/rubber/AlFine Particles Binder Coarse ParticlesSeitzman Rocket Overview-14Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.AE6450 Rocket Propulsion7

Other Rockets: Applications Pressure (cold gas)– Electrical–– attitude control maneuvering: reduced thrust aspressure used up, rendevousArcjet thrusters - maneuvering attitude controlIon engines - space propulsionAdvanced systems––––Nuclear thermal: like chemical rockets with nuclearbased heat addition, high thrustSolar thermalMagnetoplasmadynamic and other electrodynamicdevices, high impulseCombined Cycles: typically combine air-breathing withrocket cycles for single-stage to orbit (SSTO)Seitzman Rocket Overview-15Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.AE6450 Rocket Propulsion“Propellantless” Space Propulsion Solar sails: use momentum from solar wind, outbound trajectories onlyMagnetic sails: use magnetic fields instead of solidmaterial to capture “wind”Tethers:– rotating (momentum exchange, “catch and throw”)– electrodynamic: conducting material movingthrough (Earth’s) magnetic fields can producecurrents/voltages or passing current through tether produce forcesWarp drive .(space-time/ gravity manipulation)Seitzman Rocket Overview-16Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.AE6450 Rocket Propulsion8

Rocket vs. Air-Breathing Propulsion Air-breathing– doesn’t have tocarry most ofthe propellant(higher Isp)– limited to lowerMach nos. m Rocket– can operate withoutatmosphere– higher M operation(no “ram drag”)– usually higherinternal itzman Rocket Overview-17Copyright 2003,2006,2010 by Jerry M. Seitzman. All rights reserved.AE6450 Rocket Propulsion9

AE6450 Rocket Propulsion Examples: Pressure Rocket Cold Gas Thruster Cold gas (N 2, hydrazine, ) stored at high pressure with thrust provided by accel-eration through nozzle –Propellant Energy source (storage pressure) –Feed system: piping from storage to nozzle –Accelerator: nozzle (thermal to kinetic energy) Seitzman Rocket Overview-6