Thelatchvalves(located ontheaxialstruts)aredirect-acting andsensevehicle liftofffromtheaxialstrut piston. Eachvalveisdedicated toalatchassembly inordertoprevent avalvefailurefromcausing a premature disconnect oftheumbilical orafailureoftheumbilical toretractintothetunnelfollowing liftoff. Thevalve-to-latch connections werearranged tominimize actuating timeintheeventthatthevehicle pitches oryawssignificantly duringliftoff.Asmentioned previously, 30msoperating timewasallotted to thelatchitselfforoperation. Theremaining 120msdelayarisesfromvalveactuation andpneumatic system "fill"time.Thesystem driverswerethelatcheslocated ontheumbilical tunnel. Thelatcheson thetranslating framearelocated within1.5mofthevalves. Thelinelengths tothetunnellatches were nearly10mandaccounted formostofthetotaldelay.Whenoperating normally, thelatches onthe translating framewillactuate wellbeforethetunnellatches, resulting infastersystemoperation. Quick-Release LockMechanisms Thequick-release lockmechanisms resisttheseparation forcesbetween theumbilical panelsgenerated byfluidpressures andvibration. Themechanisms remainlockeduntiltheyarereleased bylanyards following liftoff.Thequick-release locksystem consists offourcolletlockslocated atthecorners ofthe ground panelandfourmatingreceptacles ontheflightpanel. Quick-Release LockMechanisms Requirements Someofthesignificant designrequirements forthequickrelease lockmechanisms were: •Resistpanelseparation force71kN(17.75kNperlock) •Support axialloadonly,shearforcesresisted byshearpins •Provide automatic lockingandpreload generation •Provide singlefailuretolerance forrelease •Minimize loadstransferred tovehicle •Prevent iceformation inmechanism Quick-Release LockMechanisms Description Thequick-release lockmechanisms useapin-expanded colletontheground paneltoengage aconical receptacle ontheflightpanel.Adisconnect lanyard, connected tothetranslating frame,pullsthepinto release thelock.Ifthecolletdoesnotrelease, acammechanism onthegroundmechanism shearsthe flightreceptacle fromitsmounttorelease thepanels. Anassembly viewanddetailsofthegroundmechanism (colletlock)areshowninFigure11.An aluminum housing interfaces withtheground panelthrough aboltedflangeconnection. Theexpanding colletisfabricated fromberyllium copper. Threads inthehousing andontheexterior ofthecolletallow foradjustment ofjointpreload byrotating thecolleteitherpriortoorafterlocking. The15-5PHstainless expansion pinhasanintegrally machined pistontoallowthecollettobelockedpneumatically. Akeyon thepinengages thecollet.Thiskeyallowsthecollettoberotated andlockedfromtheexterior ofthe mechanism usingthepin.Thehousing isboredforthepistonsealsandanaluminum endcapandrod sealclosethecylinder. Abiasspringinthecylinder maintains thecolletinthelockedposition. Asliding aluminum sleeveislocated onthefrontofthehousing. Thesleeveseatsagainst theflightpaneland resiststhecompression inthejoint.Tworollerassemblies aremounted tothebackofthesleeve. An adjustable trunnion isattached totheexpansion pin.TwoA286stainless steelrelease camspivotonthe trunnion andrideonthesleeverollers. Alanyard bracket attached tothecamscompletes the mechanism. Anambient temperature heliumpurgethrough thejointprevents iceformation. Theflightreceptacle (Figure 11)iscomprised ofanattachment boltwithatapered head,athreaded housing withatapered bore,aconical matingsleeveforinterfacing withthecollet,andashearpinfor 353