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Launch Vehicle and Spacecraft System Design

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AmericanInstituteofAeronauticsandAstronautics1LaunchVehicleandSpacecraftSystemDesignUsingthePistonlessPumpSteveHarrington,Ph.D.*SanDiegoStateUniversityFlometrics,Inc.SolanaBeach,CA,92075Theapplicationofapistonlesspumptoalaunchvehicleorspacecraftcanprovidecostand reliability improvements over standard pressure-fed or turbopump-fed designs.Calculationsshowthatinafirststagelaunchvehicleapplication,asystemwhichusesthepistonless pump has comparable performance to gas generator turbopump designs. Theperformancecanbeimprovedbyusinglow-pressureliquidheliumwhichispumpedusingapistonless pump to high pressure and then heated at the engine. This allows for lowerpressuranttankageweight.Thissystemuseslessthan1%ofthefuelmassinliquidhelium,whichoffersaperformanceadvantageovercomparablegasgeneratorturbopumppoweredrockets.Acompleteoverallvehicledesignispresentedwhichshowshowthevarioussystemsareintegratedandhowmucheachcomponentweighs.ThevehicleusesLOX/hydrocarbonpropellantsatmoderatetohighpressurestoachievehighperformanceatlowweightandlowcost.Thepumpisalsoshowntohavesignificantperformanceandflexibilityincreasesforspacecraftwhencombinedwithhigh-pressurestorablepropellantengines.Thepistonlesspumpisalsoapplicabletopumpinggelledpropellants.Nomenclaturea = factorforportionofvehiclemassproportionaltopayloadb = factorforportionofvehiclemassproportionaltopropellantmassc = factorforportionofvehiclemassproportionaltopropellantmasstimechamberpressureg = accelerationofgravityIsp= specificimpulseK = pumpdesignefficiency(Currently.5)M = averagemolecularweightofcombustionproductsP0= ChamberPressurePe= ExternalambientpressureRu= universalgasconstantf= averagepropellantdensityc= pumpchambermaterialdensityc= pumpchambermaterialacceptabledesignstressT = ThrustTcycle= cycletimeofpumpVe= IdealexhaustvelocityW = WeightofvehicleI. IntroductionThispaperdescribesapistonlesspump1asanalternativetoturbopumpsandpressurefedsystemsinbothboostandupper stage applicationsand alsofor spacevehicles. The pistonlesspumpoffers significantcost, reliability and*CEO,Flometrics,Inc.AdjunctProfessorSanDiegoStateUniversity406NCedrosAveSolanaBeachCA92075MemberAIAA.Space 2004 Conference and Exhibit28 - 30 September 2004, San Diego, CaliforniaAIAA 2004-6130Copyright © 2004 by Steve Harrington. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.AmericanInstituteofAeronauticsandAstronautics2performance advantages. Theseadvantages arerelated tothesimplicityof thedesign.  Adiscussionon how tooptimizeavehiclewhichusesthepistonlesspumpispresentedintermsofchamberpressure.Acomparisonusingthisoptimizationprocedureisalsopresentedforpressurefedandturbopumpsystems.Anypressurizedgaswhichiscompatiblewiththepropellantmaypowerthepump,butthispaperwillfocusontwopossibilities:gaseousheliumwhichisstoredincompositetanksorLiquidhelium(Lhe)whichisstoredinalowpressureDewar.Theliquidhelium,pressurizedbyapistonlesspumpandvaporizedattherocketengine.Thepumpmayalsobeusedforspacepropulsion,whereitoffersanumberofadvantagesinperformance,safetyandflexibilityforspacevehicledesigners.II. PumpdescriptionThepistonlesspumpissimilarto apressurefedsystem,butinsteadofhavingthe a maintankat highpressure(typically500-1000psi)(3-7Mpa)thepistonlesspumpsystemhasalowpressuretank(35-70psi)(.2-.5Mpa)whichdeliverspropellantatlowpressureintoapumpchamber,whereitisthenpressurizedtohighpressureanddeliveredtotheengine.Twopumpingchambersareusedineachpump,eachonebeingalternatelyrefilledandpressurized.Thepumpcontrolsaresetupsothatwhenthelevelinonesidegetslow,theothersideispressurized;andthenafterflowisestablishedfrombothsides,thelowsideisventedandrefilled.Thisresultsinsteadyflowandpressure.Thepumpispoweredbypressurizedgaswhichactsdirectlyonthefluid.Initialtestsshowedpressurespikesasthepump transitioned from one chamber to the other, but these have since been eliminated by adjusting the valvetiming. For more details on the pump and a discussion of the second-generation design see reference 1.  Thisreferenceincludesaderivationofanequationtodeterminepumpmass.Themassisbasedprimarilyonthemassofthepumpchamber,apressurevessel.Thethrusttoweightratioofagivenpumpusedwithaparticularfuelatagivencanbecalculatedby:cccyclefspfTPIgKWT


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