Theparaffinactuatorprovideslinearstroketoshuttleacylindricalsampledrawerhorizontally througha dualsealinterface.Paraffinactuatorsarewellsuitedtothistaskbecausetheyprovideaslow,controlled yetpowerfulstrokeinarelativelycompactpackage.Aresistancefilmheaterontheoutsideofthe actuatorheatstheparaffintothemeltingpoint(70°C).Whenparaffin melts,itexpands approximately 15%.Thisexpansion isusedtodrivetheoutputshaft.Theactuator ishermetically sealedwithawelded bellows. Thedrawer hasasquarecavityforthesoilthatisopenatthetopandhasaspring-loaded trapdooror scooponthebottom. Thecavityvolume is1cc.Theparaffin actuator pushes thedrawerapproximately 1.9cm(0.75inch)through thesealinterface. Onceextended, theLander robotarmdumpsascoopof soilthrough asieve(notshown) intothedrawercavity. Duringthisprocess, alimitswitchcyclesthe actuator tokeepitintheextended position. Oncecomplete, powertotheactuator isdiscontinued anda returnspringpullsthedrawerbackthrough thesealinterface. Excess soilisremoved withabrushand scraper asthedrawer retracts through theseal.Thespring-loaded trapdooropensasthedrawer retracts through theseal,dumping thesoilintothebeaker. Designtradesinvestigated avarietyofdrawerandsealconfigurations including squareandround crossection drawers, looseandtighttolerance seals,staticversesdynamic typeseals,compliant verses morerigidsealmaterials, andvarious sealconfigurations andstyles. Inaddition, various methods were investigated toremove dustandgritparticles fromthesealing surfaces including brushes, scrapers and flushing. Overthecourseoftheprogram several prototype drawers weremanufactured andnumerous testswere conducted. Testing wasdoneusingavarietyofdifferent typesofsoil,sand,gravelandothermaterials. OfficialMarssimulant soil(volcanic material obtained fromHawaiithatismeanttosimulate Martian soil asclosely aspossible) wasusedformosttests.Sandandgravel,sievedtovarious particle sizesupto4 mm,wasalsoused.Coffeegrounds andflourweretriedtoseewhateffectparticle conglomeration had ontheperformance ofthedrawer. Thegreatest difficulty wasencountered withhardcrystalline materials oflargeparticle size.Theseparticles tendedtogetcaughtintheclearances ofthesealinterface jamming thedrawerasitwasbeingretracted. Earlyversions alsohaddifficulty withthescooportrap doorarrangement gettingcaughtandfailingtoswivel(againduetocrystalline particles gettingcaughtin theclearances). Improvements weremadetotheoriginal prototype andanalternate designwas manufactured andtested. Thefinaldesignsuccessfully overcame thedifficulties withjamming andwas abletoworkconsistently withparticle sizesupto2mm.Forsandparticles largerthan2mm,thefinal designalsoshowed theabilitytorecover fromajam(inmostcases)byrepeating theextension and retraction cycle. Frostturnedouttobelessofaproblem. Frostcouldbeformed ontheinsideofthemechanism from condensation ofthewaterpresent inthebeaker. Testswithamoderate layeroffrost(perhaps 1/2mm thick)bothinsideandoutside themechanism showed itwaseasilyscraped awaybytheforceofthe paraffin actuator asthedrawerextended. Thedrawer showed notendency tojamorfreezeuponthe retraction cycle.Thiswasencouraging. However, estimating theamount offrostbuildupwasdifficult anditwasnotpossible toruleoutamuchthickerlayerthanwhatwastested. Itwasassumed thatat somepoint,athickerlayerwouldcausethedrawertojam.Toeliminate theproblem, aKapton film heaterwasaddedtotheoutside ofthedrawer housing. Theheateristurnedonforashortperiodoftime beforethedraweristobeextended thusmelting mostifnotallthefrostonthedrawer. Initially, itwasthought thatthesealrequirement forlossofnomorethan0.1cc/dayfromthesystem wouldnotbedifficulttoachieve. Feltandlabyrinth sealswereseriously considered forthistask.This requirement, however, turnedouttobemuchmoredifficult thanoriginally thought. Operation inalowpressure environment meantthatapositive pressure wouldhavetobemaintained between the experiment beaker andtheoutside environment. Withapressure difference, leakage occursquickly through gapsorholesofanysize.Several varieties ofspringorelastomer energized polymer sealswere triedwithmarginal success. Thevarieties thatdidworkhadtoomuchfrictiontoallowthedrawerto 32