Mechanical Design of the LMDE.pdf - Heroicrelics

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 -