numberofwaystoaddressthisproblemincludingpumpingthewaterout,punchingaholeinthetopof thecontainertobreakthevacuumorfindinganothermeanstopressurizethecontainer.Themethod chosenwasonethatdidnotrequireadditionalcomponents orspace.Bycrackingthedrawersealbriefly toreducethepressureinthebeakerimmediately priortopuncturingthetank,itispossibletoobtaina significantpressuredifferentialbetweentheheadgaspressureinthetankandthepressureinthe beaker.Asthewaterflowsout,theheadgaspressureisreduceddependingonhowmuchgasthereisin thetanktostartwith.Ifthetankisonly90%fullofliquidtostartwithandtherestisnon-condensable air ornitrogenatEarthambientpressure,thisisenoughpressuretopushalloftheliquidout.Testing showedthatthismethodwasindeedeffectiveenoughtodispensetheentirechargeofwaterintothe beaker. Asabackup,itispossibletoincreasethepressureinsidethetankbyheatingit.Therearefilmheaters onthesidesofthetankanywaytomelttheice.Ifyouputenoughadditionalheatin,itispossibleto simplyboilthewaterinthetanktocreateenoughinternalpressuretoforcetheliquidout.Thisworks quitewellwhenthepressureisrelativelylow.Ifitisaslowastheatmospheric pressureonMars,thetask isrelativelyeasybecausetheboilingpointofwaterislessthan10°Catthispressure.Ofcourseone doesn'twanttolosethewaterfromthebeakersothewholesystemneedstoberesealedwhilethefluid isbeingtransferred. Systems Trades Earlystageplanning fortheexperiment considered awiderangeofsample andwaterhandling capabilities. Inaddition tothosepreviously mentioned, multiple reagent addition, pumped/metered solution dispensing, vaporinterlock, stirringandmultiple usecapability wereconsidered. Toreduce complexity, costandmassonlythemostessential functions necessary toachieve valuable scientific data wereincluded intheinitialdesignconcepts. Watermustbereliably transported fromEarthand dispensed intothebeaker. Asoilsample mustbegathered measured anddelivered. Sensors musttake data. Duringthecourseoftheprogram, however, itbecame evident totheleadscientists thatreagent addition andstirringmustalsobeaddedinordertoachieve anacceptable levelofconfidence inthedata. Reagent addition wasnecessary torecalibrate thesensors onMars.Thesensors werefoundtobe sensitive toavarietyoffactors including pressure andtemperature fluctuations andpresence ofmoisture. Afterexposure tolaunch, cruiseandlanding environments, itwasexpected thatsensorcalibration would shiftsignificantly. Itwastherefore highlydesirable torecalibrate thesensors onMars.Stirring wasalso foundtobenecessary toadequately mixtheconstituents inareasonable periodoftime.Sincethe envelope fortheexperiment wasalready set,itwasnecessary toattempt tosqueeze theseadditional capabilities intothelimitedspacethatwasalready available. Reagent Delivery Thereagent dispenser (Figure 5)delivers asinglereagent pellettotheexperiment beaker. Thepellet hastobesealedthrough launch, cruiseandlanding toprevent moisture fromsoftening anddegrading the pellet.Thedesignissimpleandverycompact. Thetopendofthedispenser isaparaffin actuator. The reagent pelletiscontained inahollowcylindrical shearpistoninthelowersection. Theparaffin actuator drivestheshearpistoninordertopunchthrough aKapton sealdiscallowing thereagent pellettodrop intothebeaker. Againaparaffin actuator iswellsuitedtothetask,providing ampleforceinavery compact package. Disadvantages tothisdesigninclude thesinglepelletcapability andtheneedto manually resetthedevice. Stirring Avarietyofmethods wereconsidered toaccomplish stirringincluding paraffin actuator drivenpaddles, clocksprings, motors, solenoids, andboiling. Although anyofthesemethods couldpotentially 35