7/28/2019 STRATOS Weather Balloon Information Display for The Big Bang Fair 2013, National Science and Engineering Competition

1/1

2mmNylonCord

v=verticaldescentvelocity,inm/s-1w=weightoftheparachute+payload,inNrho=airdensityatsealevel(1.225Kg/m3)dc=parachutedragcoefficient(0.75)s=totalsurfaceareaoftheparachute(*0.3

2

)

=2

Theparachutewechosewasoriginallydesignedforusewithmodelrockets.Its

lightweightnylonfabriciswoveninacrosshatchpatterntopreventtearing,whichis

essentialforourpurpose,sincethepayloadcoulddoconsiderabledamageifitdescended

atterminalvelocity!Weu

sedthefollowingequationtocalculatethedescentspeedofthepayloadwithour

24"parachuteattached.Wethentestedthisfigurebytiminghowlongittooktofall

fromthetopofourschoolbuilding.

Althoughthin,thisbraidednyloncordisverystrong-ithasabreakingstrainof22.5kg.Weused10mofitbetweentheballoonandthepayload.

Theteamwasconcernedthattheparachutewouldgettangledduringitsascent,soweusedaninnovativesolution:securingawashertothecordjustunderwherethestretchedoutparachutewouldrest,asshowninthescanofouroriginalsketch:

Washer

24"RipstopParachute

where,

1.81m3helium(V-SizedCylinder)

600gMeteorologicalWeatherBalloon

ByusingInternetdataforourballoon,wefoundthatthevolumeofgasneededto

filltheballoonatlaunchwas1.81m3ofhelium-thesizeofastandardV-sizedBOCgas

cylinder-toachieveourtargetaltitudeof30km.Ifwefilledmorethanthisvolumeofgas,

theballoonwouldexpandtoitsburstingpointataloweraltitude-thevolumeatburstbeing

over120m3at6mdiameter-thesizeofahouse.Thevolumeofheliumfilledwasalsousedin

theflight-pathprediction-toomuchgas,andtheballoonwouldrisefasterthanpredicted,too

littleandtheballoonandpayloadwoulddriftfurtherthanpredicted.

Thereareseveraldifferenttypesofweatherballoons.Weusedanatural

latex"sounding"balloon,whichisusedinhighaltitudescience

experimentsbyweatherstations.Weatherballoonsaremeasured

accordingtotheirweight,withheavieronescostingmorebutreachinga

higheraltitude.Weuseda600gballoon,asitcouldachieveourtarget

altitudeof100,000ft,withlessheliumneededthanalargerballoon.We

usedheliumgasasopposedtohydrogensinceheliumissafertohandle.

Anotherinnovationofourswastoattachthemultiple

cordsrunningfromthepayloadtoacurtainringattached

tothemainsinglecorduptotheballoon.Thisway,we

couldindividuallygaffertapeeachknottoensurethey

weresecure,and thatthelineswouldnottangle.

CurtainRing

PolystyreneContainer

Ourpayloadwasoriginallygoingtobeawintertapcover,thoughwecouldn'tfindonewhilstpurchasingequipmentsoinsteadchosetorecycleanolddry-icecontainerfromtheschool'ssciencedepartment,whichhadpreviouslybeenusedasastageprop.Thehollowpolystyreneboxmeasures27cmwx24cmlx25cmh.

AttachingcordtopayloadAsshownintheoriginalsketchtotheleft,wegaffertapedthecordsfromthecurtainringtoeachsideofSTRATOS'spayloa

d,toensureitsst

abilityduringflight.Thegaffertapealsohelpedtowater-sealthepayloadarounditsopening-importanttoprotecttheelectronicsifitwasrainingwhereitlanded.

GPSTrackerTheGPSTrackerinthepayloadenablesustotrackthepayload'slocationonceithaslanded.Toreceivethecoordinates,wephonethedevice,andittextsbackitslocationandinformationsuchasbattery

lifeandalinktoamobileversionofamap.

WeusedasmallCanonpoint-and-shootcamera,theA550,"borrowed"fromtheGraphicsdepartmentatschool(inexchangeforanewcamera).Wehadtousethisoldcamerabecauseithastherareabilitytobe"hacked",thatis,tobeprogrammedtotakephotographsatregulartimed

intervalsautomatically,

essentialforourSTRATOSproject.

Camera

Insulation

HandWarmers

Tokeeptheelectronicsinsidethepayloadfunctioningdespitethefreezingtemperaturesoutside,thepolystyrenepayloadactedasagoodinsulator,andasanaddedmeasure,wetightlypackednewspaperinsidetotraplayersofair.Thenewspaperalsohelpedtokeepthecontentsinplaceinthehighwinds.

Regularhand-warmersonlystayhotforhalfanhour-tooshortforSTRATOS's4hourflight. After

someresearch,welearntaboutironoxidisinghandwarmerswhichremainwarmforupto7hoursata70C,icturedontheright.

Wesetthecameratotakeaphotoevery10secondsatitsbestquality,witha2GBmemorycardinside.Byusingthefactthecameratook1,486photos,wecalculatedtheexactflighttimewas4.13hours.