Mechanical Design of the LMDE.pdf - Heroicrelics

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Figure 23.Figure 24.Vibration Test ofHead End AssemblyLMDE Installed in HighAltitude Test Standqualification vibration tests ofthe complete engine.At this point, only thecombustion chamber and nozzle extensionhad not been subjected to thelaunch and boost vibration environment.They had however receivedmany thousands of seconds ofreactive firing during the developmenttests of the engine in theTRW Sea Level Vertical Engine TestStands (VETS) and High AltitudeTest Stand (HATS). As a lastmeasure before the start of thequalification series of tests, adevelopment engine was vibrationtested to the qualification environmentand then successfullyfired in HATS for a full missionduty cycle. The engine shown inFigure 24 installed in the HATSfacility is awaiting final checkoutprior to mission duty cyclefiring. The support structureto which the engine is attachedmeasures thrust and six componentsof thrust to determinethrust alignment.Analysis and Test for Dynamic LoadsA linear spring-massanalogy for the LM Descent Enginewas developed as a design tool tocompute the dynamic loads on theengine structure . Initially,this analysis consisted of asingle mass, five degree-offreedomsystem. Two componentmasses were added to the initialanalysis, increasing the number ofdegrees of freedom to eleven.Hand computation of the dynamicloads became very time consumingso the response equations were programedfor the digital computer.The first vibration testof the gimbal, described earlier,indicated that a strong enginetorsional mode existed (enginerotation about the thrust axis).The corresponding rotationalcoordinate,e, had been leftx- 17 -
out of the first two analyses on the assumption that the torsional mode wouldnot be strongly excited. Based on this experience, a third and final springmassmodel was developed. The primary purpose of this analysis was to includethe torsional coordinate. In addition, the gimbal was represented astwo support masses with a system of springs connecting them to the main enginemass. Each side of the gimbal is connected to the Lunar Module with a fourmembertruss . Modeling the gimbal in the above manner facilitated representationof the support trusses as a system of springs .The final model is basically a three mass, twelve degree-of-freedomsystem (Figure 25) . The motion of the main engine mass is described by sixcoordinates, three displacements and three rotations, in a rectangularcoordinate system with the origin at the center of the gimbal. The twogimbal/support mass motions are described by three displacement coordinateseach.'3FINAL SPRING - MASS MODEL OF ENGINETHRUST ENDSUPPORT MASS, '"3"SUPPORT MASS , m 2HEAO ENDKG,,' K ' K - GIMBAL SPRINGSCy GzK, - GIMBAL TORSIONAL SPRINGK,,2' K y2' 1
Page 1 and 2: MECHANICALDESIGNDFTHE LUNARMODULEDE
Page 3 and 4: Engine DescriptionCOMffNSAT1NGSPIti
Page 5 and 6: Engine GimbalThe gimbal assembly is
Page 7 and 8: Figure 6.Engine Mass SimulatorMount
Page 9 and 10: Figure 10.Combustion Chamber Assemb
Page 11 and 12: Nozzle ExtensionThe radiation coole
Page 13 and 14: Figure 15.Nozzle Extension in Crush
Page 15 and 16: (a)Cross BeamFlexure(b)Injector Dri
Page 17: Figure 21.Figure 22.Section of Two-
Page 21 and 22: Figure 26.Vibration Test of LMDEsys
Page 23: designers and builders of the Lunar

Mechanical Design of the LMDE.pdf - Heroicrelics

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