Description TheLockRingAssembly consists ofa7075-T73 aluminum ring(81.28cm(32in)indiameter) with twenty-four ½-inch-diameter trackrollerpairsequally spaced around theringperimeter. TheentireLock RingAssembly isseeninFigures 3and4butamoredetailed viewisavailable inFigures 5aand5band thesection viewsinFigures 6aand6b.Thisbasicconfiguration wasinspired bytheShuttle Get-Away Special (GAS)design. Theupperrowoftrackrollersismounted ontwenty-four bending beamflexures thatcreateaclamping forceonthejointbyrollinguprampstothelockedposition. Theclamping force compresses thesealandpreloads thejointagainst launch#eentry forcessothatmetal-to-metal contact is maintained. Thetwobending beamflexures located nearest theArrayLatchMechanism arestifferin ordertoreacttheadditional inertialloadsofthearrays. Radialbearings attwelvelocations aroundthe ringprovide bothradialalignment capability andradialloadcapacity. Thetrackrollersintheupperrow aretilteddownward intheirunloaded state,1°fortheregularflexures and2_forthestiffflexures. Asload isapplied tothetrackrollers,thebending beamflexures bothdeflectandrotatebecause thetrackrollers arecantilevered fromtheseflexures. Tiltingthetrackrollersintheirunloaded stateensures thatinthe fullyloadedstate,thetrackrollersareloadedinthecenteroftheirouterbearing race. Obtaining andmaintaining themetal-to-metal contact duringlaunchandreentry wasthebiggest challenge forthecanister structure andlockringsystem. Thisfeature isadistinct difference between the Genesis payload designandtheShuttle GASanditisanimportant difference because oftheGenesis needforextreme contamination control. Theinitialdesignforthecoverandthebaseconsisted ofsimple cylinders withflanges attheseparable interface. Afirstorderloadanalysis thatsimplified thebaseasa rigidstructure wasusedtoestimate theclamping forcerequired fromtheLockRing.Inthissimplified analysis, massacceleration ofthecoverinthedirection normaltotheinterface wasreacted bytheLock Ringclamping forcewhilein-plane massaccelerations werereacted withtheshearpinsinstalled inthe baseflange. Theunderlying assumption inthissimplified analysis isthatminimal coupling exists between theloaddirections. Theinadequacy ofthisassumption quicklybecame apparent inamore detailed loadanalysis. Loadsaretransferred fromtheSRCtothecanister basethrough asetofthree bipods, whicharepartially visibleinFigure3.Because ofthisconfiguration, loadsreacted intothebase fromtheSRCcreatein-plane deflections ofthebase.Inturn,therelatively stiffcoverdeflects inthe samewayasthebase,absorbing quiteabitoftheloadandcausing thetensileloadattheseparable interface toincrease dramatically. Thecoverandthebasewereredesigned tobringthetensileloadsat theinterface backtoanacceptable range. Akickringwasaddedtothebaseantiacov_erflexurewas addedtothecover(Figures 6aand6b).Thekickringstiffens thebase,whichreduces thein-plane deflections whilethecoverflexuresoftens thecover,whichreduces thetransfer ofloadfromthebaseto thecover.Thebending beamflexures inthelockringwereredesigned toaccommodate asmallincrease inload. Twopush-off blocksareattached tothecoveroneachsideoftheLockRingDriveMechanism. Together thepush-off blocksprovide aseparation force,ifneeded, atthesealinterface whentheringunlocks. Push-off reaction pads,mounted onthekickring,capture theLockRingAssembly whenunlocked and actinconjunction withthepush-off andshorting blockstocreatethesealseparation. TheCanister Seal consists ofsilicone inaGask-O-Seal configuration incorporated inanaluminum retainer. Thetopsurface ofthesealretainer ishardanodized andthebottomsurface ofthematingcoverflangeiscovered with Magnaplate, anickel-based coating, toformtheseparable interface. AthinlayerofBraycote grease coverstheseal.Testswereperformed usingsealsamples underprolonged clamping andexposed to representative temperature, vacuum andradiation environments. Therehasbeennosignofstiction with thesematerial combinations. Inaddition, therewasnoevidence ofstiction atthisinterface duringthe functional testingoftheEngineering Modelcanister. Figure7depicts theoperation oftheLockRingAssembly. Intheunlocked position, thereisnoloadon thetrackrollerpair.Theuppertrackrolleristilteddownward andthelowertrackrolleriscaptured between thelowerbearing padandthepush-off reaction pad.Thepush-off reaction padsoccuronlyin fourplacesandtheykeeptheLockRinginplacewhenthemechanism isunlocked. Duringlocking, the firsttrackrollercontact withtherampoccursaboutathirdofthewaythrough thetravel.Atthispointthe 200