Asaresult,wewereabletoprecisely locatetherotorsbetween thestators. Withthisknowledge, we wereabletomoveawayfromthephilosophy oflimitingtheaxialmotionduetomisalignment forcesand towardthephilosophy oflimiting theaxialforcesbyprecisely locating therotors. Inaddition, wemodified theactuator designtodoublethegapsto3.81E-04 m(0.015in)between therotorsandthestators. This increased gapalsoreduces thesensitivity ofthemechanism totheforcesgenerated bythemagnetic circuit. Consequently, wewereabletolowerthetension ontheflexureto111.2N(25Ib)atroomtemperature. Sinceweimproved thebearing design, beganprecisely measuring components, andreevaluated thecold motion, wehavebeen100%successful withourassemblies andcoldtests. Launch andOperational Loads Theinitialdesignoftheflexurewasaparametric tradestudyoftorsion, stress,andgeometry. Wealso decided tolimittherotational loadstheshutterwouldexperience withanunbalanced cantilevered mirror inavibration environment. Therefore, wecounterbalanced themirrorwithamassofTantalum. The resultwasashaftthatweighed 2.22N(0.5Ib).However, thedesignwascompleted beforeourlaunch loadenvironment wasfullydefined. Acoupled loadanalysis identified thattheshaftcouldexperience loadsof100Gs.Thiswasnotanticipated andwebecame concerned aboutthevibration loadtheflexure wouldexperience duetotheincreased massofthebalanced shaft.TheFEAontheshutter confirmed thattheflexurewouldyieldundertheseloads. Welookedintoincreasing thesizeoftheflexure, butduetoschedule restrictions wedecided notto change theflexuredesign. Next,welookedatremoving thecounterweight toreducetheaxialloadson theflexure. However, without thecounterweight, themirrorwouldrotatewildlyinthevibration environment. Although theaxialloadswouldbeless,thecombined loading oftherotational stresswith theaxialwasstillenough toyieldtheflexure. Thevalueofthecounterweight wasworththeaddedmass. Wehadtolimittheloadsanother way. Weimplemented alaunch-load stoptocapture themirrorarmthroughout itsfullrangeofmotion. Ithad tocapture themirrorarmnearitsbaseduetohighloads.Thedesignresembles agoalpostinfootball andwasaddedasacomponent ofthehardstop.WechoseAluminum 7075asthematerial duetothe highloads.Finally, thepartwasplatedwithTeflon-impregnated anodize tominimize wearandfriction. Thegapsbetween theuprights andthemirrorarmwereprecision controlled tobe2.03E-04 m(0.008in). Thisgapwouldsufficiently limittheaxialmotionoftheshaftwhilenotallowing therotorstoimpactthe statorsintheactuators. Thecomponent hasworked finetodateandhassurvived coldvibration testing andsupports thefailssafeopenrequirement. Position Sensor Thedevelopment oftheposition sensorprovedmoredifficultthanexpected. Theinitialdesignwasa simple"C"shaped magnetic circuitwithonelargecoilbetween thetwopoles(Figure 12).Asstatedinthe description, therampwassimplytopassthrough thegapbetween thetwopolesthatwereslightly tapered tofocusthefluxandfitwithintheshutterdesign. Thechange inthereluctance ofthecircuitas theramppassed between thepoleswouldbemeasured electronically. Theoretically, thedesignwas sound. However, whenwetestedtheprototype, weonlygotaresponse of30mVfullrange. Infact,it wasdifficult tomeasure anyresponse atalloverthenoiseintheelectronic circuit. Uponconducting arigorous analysis usingtheAmperes modeling software, itbecame clearthatthere werelargelossesandfringeeffectswithinthemagnetic circuitduetothegeometry. Thefringeeffectsin thecircuitactasmagnetic shortsandreducetheeffectiveness ofthesensor. Sinceweonlyhadonecoil withamagnetic poleattached ateitherend,wegenerated relatively largesurface areasofopposite potential facingeachother.Asaresult,themagnetic fluxsimplyjumped thegapbetween thepolesall alongthemratherthanonlyjumping thegapbetween thepolefaces.Sincetherewaslessfluxfocused totheactiveareaofthesensor, theresponse wentdownappreciably.