thepercentcontribution thateachofthethreemainelementsmakestotheoperationoftheSN9400and SN9500seriesseparationnuts. Development Testing Togainabetterunderstanding ofthethreemainsourcesthatcontributetotheoutputshock, development testingwasperformedontheSN9400andthreeiterationsoftheSN9500ULS.Various experimental techniques wereemployedtoisolatethethreemainsourcesthatcontributeshockoutput. Thedatacollectedfromtestingeachsourceofshockoutputwasusedinoptimizingthefinaldesignofthe ULS.Allocatingapercentcontribution thateachofthethreesourcesshouldmakeduringactuationset theoptimizeddesigncriteria.Thepercentage valueslistedinTableIfortheSN9500ULSwerefoundto betheoptimalarrangement thatcouldbecontrolledformaximumshockoutputreductionwithout compromising thefasteneraspectoftheseparationnut. Validation Testing Theoptimized designoftheSN9500 ULSisshowninFigure2.Validation testingoftheshockoutputwas performed andcompared tothatoftheSN9400. Testing wasperformed usingaM12-1.75 (0.50020UNJF-3B) separation nutofthe9400and9500series,bothseparation nutswerepreloaded to89kN (20,000 Ibf).Intheabsence ofanystandardized shockoutputtestfixtureforseparation nuts,aworstcase approach wastakenbyperforming thetestona61-cmx61-cmx1.9-cm(24inchx24inchx0.75inch) aluminum plate.Theworstcaseapproach wouldbestserveindustry sincesatellite structures consist of various typesofcomposite structures thatwouldcontribute toanattenuation oftheseparation device shockoutput. Byestablishing aworstcasebenchmark foreachseparation nut,designengineers willbe abletoselecttheappropriate sizeandtypeofseparation nutforevaluation onparticular structural applications. Thetestsetfixturing andsetupusedformeasuring shockoutputisshowninFigure3.The testarticleismounted toatestblockandthenmounted tothecenterofthealuminum testplate.The aluminum testplateissuspended withfourelasticcordsattached toeachcorneroftheplate.Theshock outputwasmeasured foreachofthethreeorthogonal axisviaa2.54-cm x2.54-cm x2.54-cm (1.0inchx 1.0inchx1.0inch)aluminum accelerometer blockmounted 15.24cmfromthecenteroftheseparation nut.Theshockresponse fortheSN9400 separation nutisshowninFigure4withtheresponse inthetime domain showninFigure5.Thereduced shockoutputoftheSN9500 separation canbeseeninFigure6 withtheresponse inthetimedomain shown inFigure7.Acomparison ofthetestresults showsa significant reduction of75-85% reduction inthefrequency rangeof1kHzto4kHz.Ithaslongbeen accepted that1kHzto4kHzrangeisthemostvulnerable forelectronic andopticalpayloads. Summary TheSN9400 seriesseparation nutshaveperformed asaworkhorse fortheaerospace industry formore thantwentyyears.Theonlyprudent approach tomeeting thechanging demands forsatellite platform separation nutswastoapproach theexisting heritage technology withtheaimofidentifying alldesign parameters thatcouldbeoptimized andproduce thehighest gainsinperformance. Hi-Shear's product enhancement effortsbrought aboutanewgeneration ofanexisting product linewhileutilizing standard initiators, non-exotic materials andtraditional fabrication methods. Results exceeded theoriginal goalof reducing outputshockby50%andaccomplished reduction levelsasmuchas75-85%. Continued efforts toincrease performance attheseparation device levelwillyieldthegreatest benefit totheaerospace industry. TableI.ShockOutput Contribution fromThreeMainSources Source ofShock SN9400 PyroShock 10% BoltStrainEnergy 60% Mechanical Impact 30% Total 1O0%ShockOutput SN9400 @2kHz 2,747m/s2(280g) 16,480m/s2(1680g) 8,240m/s2(840g) 27,468 m/s2(2800g)SN9500 30% 20% 5O% 100%ShockOutput SN9500 @2kHz 736m/s2(75g) 491m/s2(50g) 1,226m/s2(125g) 2,453m/s2(250g)Relative Reduction @2kHz -73% -97% -85% -91% NASA/CP--2002-211506 133