Mechanical Design of the LMDE.pdf - Heroicrelics

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Figure 17 shows the test specimen after the test. The tests performedearly in the program gave assurance that the analytical methods were correct ,therefore the risk taken by leaving the qualification crushing test tilllate in the program was small.Figure 17 .Columbium Nozzle ExtensionAfter Crushing TestThrottle Control LinkageWe have reviewed the structural design of the larger componentsof the LMDE. Now , we shall look at some of the small details which are ofmajor importance in the function of this engine. The linkage between thethrottle actuator, the flow control valves and the variable area injectordrive mechanism requires high precision. The ratio between the motion ofthe flow control valves and the injector is 5:1. Total motion of theinjector sleeve is 0.15 inch. A ten per cent increment in throttle settingis therefore a motion of only 0.003 inch. In order to maintain the positionrelationship between the injector sleeve and the flow control valves,looseness in the pivot bearings of the linkage had to be virtually eliminated.Another constraint on the design was that the joints of themechanism be capable of motion in a complete vacuum.Where possible, moving elements are connected by flexures. SeeFigure 3. Photographs of these flexures are shown in Figure 18. Tensionand compression loads are transmitted through these flexures while theypermit relative rotation of the connected members. In order to insureagainst a structural failure of these critical components, they were designedwith redundant load paths . Either side of the flexure is capableof full load and life should one side fail.- 13 -
(a)Cross BeamFlexure(b)Injector DriveFlexureFigure 18.ThrottleLinkageFlexuresIn those places where a flexural element was not practical, pivotbearings were used. The first concept was to use a non-metallic bearingfabricated of fiberglass and phenolic. Initial tests showed that the wearrate of the bearing and the compliance of the material exceeded the requirements.An all metal configuration was selected. The extremely simpledesign consists of a steel bushing with a steel pin - both coated withmolybdenum disulfide in an inorganic binder. This configuration also providesredundancy. The primary motion occurs between the pin and the innerdiameter of the bushing. Should this not function, the bushing wouldrotate in the bore of the link of the mechanism. To substantiate thereliability of the design, an assembly of the throttle linkage was subjectedto a cycling test in a vacuum chamber at 8 x 10- 10 Torr. Criteriafor success was completion of 10,000 cycles (33 mission duty cycles) withno significant change in load.Proof that the complete assembly met the requirements for ruggedness,rigidity and repeatability was obtained in the deflection test shownin Figure 19. In this test motions of the two flow control valve pintles,- 14 -
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: Figure 15.Nozzle Extension in Crush
Page 17 and 18: Figure 21.Figure 22.Section of Two-
Page 19 and 20: out of the first two analyses on th
Page 21 and 22: Figure 26.Vibration Test of LMDEsys
Page 23: designers and builders of the Lunar

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