Rotarymotionisproducedbythegeometryofthedevice.Thefootprintoftherotorisbestdescribedasa bowtie.Thereareraisedportionsofthestatorsthatmatchtheprofileoftherotorexactly,thoughthe footprintofthebaseofthestatorsiscirculartomatewiththecloseout.Thestatorsfaceeachotherwhen theactuatorisfullyassembled. Thereisjustenoughseparationofthestatorfacestoallowtherotorto passbetweenthemwith0.33-mm(0.013-in)clearanceonbothsides.Therotationalpositionoftherotor intheopenstateissuchthatitsfootprintisoutofphasewiththoseofthefacingstatorsexceptforan approximately 30degreesofoverlapatoneside.Inthisposition,therotorisatastateofhighreluctance inthemagneticcircuit.Whencurrentisapplied, therotorwantstoachieve astateofminimum reluctance. Thus,therotorisdrawnbetween thestatorfaces.Thismotionproduces atorqueandrotates theshaftandmirrortotheclosedposition. Afinalcomponent totheactuator designisparamount toachieving the5-mWrequirement. That component isamagnetic latchthatextends vertically fromeachofthestatorfaces.These"tabs"are positioned andsizedsuchthattherotorcontacts thetaboneachofthetwostatorswhenitisfullyrotated totheclosed-position. Withtherotoragainst thesetabs,themagnetic fluxcantraveldirectly fromstator tostatorthrough thecontacting rotorandontothemagnetic closeout. Therotoreffectively completes the magnetic circuit,reducing allairgapstonearlyzero,producing alargedropinmagnetic reluctance. This dropinreluctance meansthattheshuttercanbeheldclosed, fighting therestoring torqueofthetorsion flexure, withamuchlowermagnetic field.Sincethefieldiselectromagnetic inorigin,thereduction infield meansareduction incurrentandlesspowerdissipation inthecoil.Theresultisashutterthatrequires 55mAtocloseandlessthan1mAtoholdclosed. Offurtherbenefittoachieving lowpowerdissipation isthefactthismechanism operates atliquidHelium temperatures. Theresultisareduction ofresistance oftheelectromagnetic coilsfrom2700ohmsat roomtemperature to20ohmsat4.2Kelvin,afactorof135change. Thischange hasbeenverified during liquidHeliumtesting. Sincetheshutter closesinapproximately 0.5second, thecontrolelectronics sends ahighcurrent pulse,thenquickly dropsthemagnitude toaholdcurrentvalue.Byincluding aposition sensor(described later)toresolve theposition oftheshuttermirror,theshutter electronics immediately knowwhentheshutter isclosedandtimespentatthehigherpull-incurrent isminimized. Timeaveraged powerdissipation canthenbecalculated usingEquation 1.Assuming atypicalshutter closure duration of 500seconds andincluding marginonthecurrent levels,theinputstotheequation areasfollows: Pull-inCurrent -Ipull=60mAI[PaHoldCurrent -Ihold=3mA Pull-inCurrent Duration -tpuH=0.5s ve-- HoldCurrent Duration -thold=499.5S Totalresistance- -I_ot=20DJpull2•Rtot•tpull+Jhold2•Rtot•thold tpull-t-thold Equation 1-TimeAveraged Power Theresultisashutter mechanism thatdissipates 252pW,afactorof20lessthantherequirement. Structural andStressLimitina Components Thehousing isacontinuous pieceofAluminum 6061-T651. Pockets aremachined intoeachendalong themainaxistohousetheactuators. Agapinthestructure, between thetwoactuator pockets, allows therotation ofthemirrorattached atthecentralhuboftheshaft.Endcapsoneitherendoftheshutter housing contain theactuators withinthepockets andprovide support structure forseveral components on eitherendoftheflexure. Theactuators arepreloaded against theseendcapsbyawavespringinthe bottomofeachactuator pocket. Thispreload maintains theposition oftheactuator components during launchandprovides axialcompliance necessary forCTEmismatched partswhengoingcold. Aholeinthecenteroftheendcapprovides abearing surface forthesteelbushings ontheendsofthe shaft.TheendcapisplatedwithaTeflon-impregnated anodize toprovide somelubricity during actuation. Precision concentricity ismaintained intheposition oftheseholesintheendcaps,the interface oftheendcapstothehousing pockets, andtherelationship ofthecenters ofeachofthe pockets toensurethattheaxisofrotation oftheshaftiscentered.