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Glossary of Common Model and High Power Rocketry Terms With thanks to Randy Culp for his initial 2008 publication. This is an updated compilation of a number of on-line glossaries of model and high power rocketry terms. 3FNC: Three Fins and a Nose Cone, the description of a generic rocket. 4FNC: Four Fins and a Nose Cone. Another generic rocket description. 1010: A 1.0" x 1.0" T-slotted aluminum rail produced by 80/20. 1515: A 1.5" x 1.5" T-slotted aluminum rail produced by 80/20. 80/20: A company that makes aluminum extrusions that can be used as launch rails. The 80/20 1010 Extrusion is compatible with standard rail buttons (such as those from railbuttons.com). The company's 1515 Extrusion is compatible with larger rail buttons. Ablative: To wear away under stresses of heat, oxidation, and high velocity gas erosion as during supersonic flight. Acceleration: Increasing velocity with time. Accelerometer: An electronic device for detecting the presence of acceleration. An accelerometer can be used for flight data gathering or for controlling flight events. For example, an accelerometer with a memory chip can record the strength and duration of a rocket's acceleration. This information can be used to calculate the rocket's approximate altitude. An accelerometer can be used to determine the proper time for a deployment charge or sustainer motor to be activated). Advanced Rocket: see “High Power Rocket” AERO-PAC: The Association of Experimental ROcketry of the PACific, a prefecture of Tripoli in Northern California. Despite the name, this is an HPR club and does not fly liquid fueled or other amateur rocketry vehicles. Its main purpose is education through experimentation with rocketry while following the NAR and Tripoli safety codes. Aft: The rearward end of something on a rocket. Ship terminology is often used because "top" and "bottom" are confusing as orientation changes. AGL: Above Ground Level. This is FAA-speak which, when talking about an altitude waiver, refers to the maximum altitude you can legally fly under that waiver. It is usually added to the MSL (Mean Sea Level) altitude of the launch site to give an altimeter reading that pilots must avoid. Aerodynamic Heating: The heating of a solid object in an airflow caused by the friction of the air against the object. Airframe: The rocket structure. This usually refers to just the cylindrical body tube, but may also refer to the entire body of the rocket. Air Start: Any motor that is started after first motion of the vehicle. Upper stage ignition of a multi-stage rocket is a special case of air starting. Usually it is outboard boosters started after a central motor has lifted the vehicle, or visa

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Page 1: Glossary of Common Model and High Power Rocketry Termsnorthernohiotra.com/documents/MR and HPR Terms v.3.pdf · Advanced Rocket: see “High Power Rocket” AERO-PAC: The Association

GlossaryofCommonModelandHighPowerRocketryTermsWiththankstoRandyCulpforhisinitial2008publication.Thisisanupdatedcompilationofanumberofon-line

glossariesofmodelandhighpowerrocketryterms.

3FNC:ThreeFinsandaNoseCone,thedescriptionofagenericrocket.

4FNC:FourFinsandaNoseCone.Anothergenericrocketdescription.

1010:A1.0"x1.0"T-slottedaluminumrailproducedby80/20.

1515:A1.5"x1.5"T-slottedaluminumrailproducedby80/20.

80/20:Acompanythatmakesaluminumextrusionsthatcanbeusedaslaunchrails.The80/201010Extrusioniscompatiblewithstandardrailbuttons(suchasthosefromrailbuttons.com).Thecompany's1515Extrusioniscompatiblewithlargerrailbuttons.

Ablative:Towearawayunderstressesofheat,oxidation,andhighvelocitygaserosionasduringsupersonicflight.

Acceleration:Increasingvelocitywithtime.

Accelerometer:Anelectronicdevicefordetectingthepresenceofacceleration.Anaccelerometercanbeusedforflightdatagatheringorforcontrollingflightevents.Forexample,anaccelerometerwithamemorychipcanrecordthestrengthanddurationofarocket'sacceleration.Thisinformationcanbeusedtocalculatetherocket'sapproximatealtitude.Anaccelerometercanbeusedtodeterminethepropertimeforadeploymentchargeorsustainermotortobeactivated).

AdvancedRocket:see“HighPowerRocket”

AERO-PAC:TheAssociationofExperimentalROcketryofthePACific,aprefectureofTripoliinNorthernCalifornia.Despitethename,thisisanHPRclubanddoesnotflyliquidfueledorotheramateurrocketryvehicles.ItsmainpurposeiseducationthroughexperimentationwithrocketrywhilefollowingtheNARandTripolisafetycodes.

Aft:Therearwardendofsomethingonarocket.Shipterminologyisoftenusedbecause"top"and"bottom"areconfusingasorientationchanges.

AGL:AboveGroundLevel.ThisisFAA-speakwhich,whentalkingaboutanaltitudewaiver,referstothemaximumaltitudeyoucanlegallyflyunderthatwaiver.ItisusuallyaddedtotheMSL(MeanSeaLevel)altitudeofthelaunchsitetogiveanaltimeterreadingthatpilotsmustavoid.

AerodynamicHeating:Theheatingofasolidobjectinanairflowcausedbythefrictionoftheairagainsttheobject.

Airframe:Therocketstructure.Thisusuallyreferstojustthecylindricalbodytube,butmayalsorefertotheentirebodyoftherocket.

AirStart:Anymotorthatisstartedafterfirstmotionofthevehicle.Upperstageignitionofamulti-stagerocketisaspecialcaseofairstarting.Usuallyitisoutboardboostersstartedafteracentralmotorhasliftedthevehicle,orvisa

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versa.Afirstmotionsensor,g-switch,timerorbarometricpressuresensorcandothis.Manymodernaltimetershavethecapabilitytodothis.

Altimeter:Adevice,whichmeasuresatleastthemaximumheightarocketinflightreaches.Theseareoftencombinedwithcircuitrytoseparatetherocketatapogeeand/orfordualdeploymentoftherecoverysystem.Somehavecircuitrythatcanalsobeusedtoair-startadditionalmotorsinaclusterorattachedoutboardpods.

AmSpam:Deprecatingbutaffectionateabbreviationsfor“AmericanSpacemodeling”(q.v.)

AmericanSpacemodeling:ThejournaloftheNationalAssociationofRocketry.Previouslyknownas“TheModelRocketeer”(q.v.),itunderwentyetanothernamechangeandbecame“SportRocketry”(q.v.)startingwiththeSept/Oct1993issue.

AmateurRocketorExperimentalRocket:Theclassofnon-professionalrocketbeyondHPR.Amateurrocketsusestructuralmetalpartsandveryoftenthemotorcasingdoublesastheairframe(aswithprofessionalrockets).Theserocketscanbeverylargeandpowerful,capableofplacingpayloadsmanymilesup.Activitiesinthisfield(onecanscarcelycallitahobby)includeformulationandmanufactureofpropellantsandthuscanbeEXTREMELYhazardous.Thisisthemainreasonthatamateurrocketryisnottobeattemptedalone.Anotherisexpenseasthesevehiclescanrunmanyhundredsorthousandsofdollarsandtakemonthstobuild.Theequipmentnecessarytosafelypursueamateurrocketry(sandbaggedbunkers,loadingpits,standbyfiretruck,etc.)isquitebeyondtheresourcesofmostindividuals.Notallamateurrocketsaresolarge.Manyofthe"beginner"vehicleswouldqualifyasHPRorevenmodelrocketsintermsofliftoffweightandtotalimpulse,butfailtheNAR/Tripolicodesduetotheirmetalairframesanduser-compoundedpropellants.Note:Thereisafine,butsignificant,differencebetweenusingametalcasedreloadablemotorwithpre-manufacturedfuelslugsandpackingapipewithzinc/sulfur(acommonamateurbeginnerfuel).Liquidfueledvehiclesarebecomingmorepopularamongamateurgroups.Thesecanproduceupto1,000lbs.ofthrustforuptoaminutefromaLOX/Keroseneengine,whichcanpropelthevehicletoaltitudesofover40miles.NeitherTripolinortheNARsanctionamateurrocketactivities.Seealso:

BlackRockSocietyExperimentalSpacecraftSocietyPacificRocketSocietyReactionResearchSocietyRocketandSpaceFoundation

AN:AmmoniumNitrate,anoxidizersometimesusedinexperimentalmotors.

Anti-Zipper:Anynumberoftechniquesusedtoprevent“zippering”ofairframetubesbytherecoverysystem.See“ZipperMotorEffect”.

AP:AmmoniumPerchlorate,theoxidizerusedinmostcompositerocketmotors.OftenreferredtoasAP90,AP200orAP400asadesignationofthesizeoftheAPparticlesmeasuredinmicrons.

APCP:AmmoniumPerchlorateCompositePropellant.Thetypeofpropellantusedinthemajorityofhighpowerrocketmotors.APCPhas3-4timesthedeliveredimpulseofconventionalblackpowderrocketpropellant.

Apogee:Thehighestpointofarocket'sflightpath.(Moreliterally,thepointfarthestontheflightpathfromEarth.)

ApogeeDeployment:Ejectionoftherocketsrecoverysystematpeakaltitude,usuallyinlowandmid-powerrocketsusingtherocketmotor(andnoelectronics)forcoastdelayandpyroejectionofthemainrecoverysystem.Inrocketsusingaltimeter-baseddeployment,therocketwillseparateatapogee,deployingasmalldrogueparachutetoslowitsdecenttoaloweraltitudewherethemainparachutewilldeploy.

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AR:AmericanRocketeer-Centuri'sattempttoproduceanMRN(q.v.)cloneinthelate'60s.Whilethecontentswerefairlytypical(productannouncements,clubnews,rocketplans,reportson"real"aerospaceevents,etc.)ithadacuriouslyover-producedlooktoitandranveryheavyontheadvertising.Someonelookingbeneaththesurfacewouldnoticethattherewasnoreaderinput(e.g.rocketdesignsor"IdeaBox"styletips);thatalltherocketplanscamefromtheCenturidesigndepartmentandthe"tips"wereforproblemsthatcouldbesolvedbyitemsstraightfromthecatalog!Whileeachissuecarriedavolume/numberidentification,therewasonlyone"Number"foreach"Volume."V1,N1wasin1966andcontinuedforatleastfouryears.

ARA:AustralianRocketryAssociation,Inc.AlsoARAPress,apublicationhouseforrocketryandsciencefictionsubjects.

BATFE:BureauofAlcohol,Tobacco,FirearmsandExplosives;afederalregulatoryagency.SometimescalledATF,BATF(olderacronyms).

B/G:BoostGlider:Aglider,whichisboostedtoaltitudebyarocketmotor.Thepodcontainingtheexpendedmotormayseparatefromtheglideratejectiontobereturnedbystreamerorparachute(thisistypicalbutisnotrequired).Themoreaerodynamicallycleanglidersectionisthenfreetoglidemoreslowly.

Baffle:(See“EjectionBaffle”)

BALLS:TheNationalExperimentalRocketLaunch.AnannuallaunchsponsoredbyTripoliandhostedbyTripoliGerlachforthepurposesoflaunchingverylarge(Kandabove)HPRrockets.Anoutgrowthoftheone-dayExperimentallaunchtraditionallyheldthedayafterLDRS,Tripoli"adopted"theconcepttoprovideinsuranceandcontinuityonanannualbasis.TheideaoriginatedwithSteveBuck,andBillLewis,ofAERO-PAC,sponsoredthefirstlaunch.Thenamecamefromjokessurroundingtheevent(e.g."IttakesBALLStolauncharocketthatbig").Steveclaimsthatitwasneverintendedtomean"BigAssLoadLiftingSuckers"asimpliedinearlyadvertisements.ThemaindifferencebetweenBALLSandotherTripolilaunches(e.g.LDRS)arethatnorocketsbelowKpowerarepermitted(nomodelrocketlaunchpads)andthatResearchorEXmotorsareallowedaslongastheyconformtotheTripoliResearchSafetyCode.Thisisalsotheonlylaunchwheremetalvehiclescanbeflown.

BallisticCoefficient:Ameasureofaprojectile'sabilitytocoast.ItisdefinedasCb=M/CdAwhereMistheprojectile'smassandCdAistheDragFormFactor(q.v.).Atanygivenvelocityandairdensity,thedecelerationofarocketfromdragisinverselyproportionaltothisvalue.Intuitively,itistheprinciplebehindwhyatightlycrumpledpieceofpapercanbethrownfartherthanalooselycrumpledone.

BAR:BornAgainRocketeer.Aformerrocketeerwhohasre-discoveredthehobbyafteranabsenceofseveralyearsorevendecades.AmarketingtermcoinedbyNorthCoastRocketryinthe1980’stocharacterizetheaimoftheiradvertisingandproductline.(Contrast"BOR")

BaseDrag:Acomponentofaerodynamicdragcausedbyapartialvacuumintherocket'stailarea.Thevacuumistheholecreatedbyyourrocket'spassagethroughtheair.Basedragchangesduringflight.Whilethemotorisfiring,thedragisminimalsincethetremendousvolumeofgasgeneratedbythemotorfillsthisvoid.Thedragtakesasharpjumpatburnoutwhenthisgasdisappears(note:trackingsmokehasverylittleeffectonbasedragduetoitslowdensity).Basedragcanbereducedbytheuseofaboattailtotransitionthemainbodydiameterdowntothemotordiameter,whichhelpsdirectairintotheevacuatedarea.Whenproperlydesigned,aboattailcanreducebasedragbelowzero(i.e.actuallygenerateasmallamountofforwardthrust)bymakinguseofthe"pumpkinseed"effect.

BatesGrain:Tubulargrainuninhibitedontheends,whichcanprovideanearlyneutralburningcharacteristic(BATCHTESTmotor).

BernoulliEffect:Aphenomenonfirstdescribedbythe18thcenturySwissscientistDanielBernoulliwhostudiedthepressuresinmovingfluidstreams.Theeffectstatesthatmovingairwillhavealowerpressurethanthestillairaroundit.Thisistheprinciplebehindhowairplanewingsgenerateliftandwhybeachballsstay"balanced"ontopoffansinthosehardwarestoredisplays.Theeffectissignificantinrocketrywhenusingaltimetersoranyotherkindofpayloadthat

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sensestheambientpressurearoundtherocket.Theairmovingbythepayloadsectioncouldcausethepayloadtoindicatealowerpressurethantheambientstillair,thusgivingafalsealtitudereading.Theeffectdropstozeroatapogeewhenyourrocketstopsmoving,butthealtitudevs.timecurvewillbewrong.

BernoulliLock:Aphenomenonsimilartothe"KrushnicEffect"(q.v.)wheretherocketseemstobe"glued"tothepadatliftoff.Thisafflictslarger,flat-bottomedrocketslaunchedtooclosetopadswithflatblastdeflectors.Theexhaustgassesescapeatgreatspeedthroughthesmallannularspacebetweentherocketandthepadcreatingaventure,whichgeneratesalow-pressureregionatthebase.Thispressuredeficitcanbesignificant,andifitisgreaterthanthethrustbeinggeneratedbythemotor,therocketwon'tgoanywhere!Thisisquitepossibleasa2"diameterrockethas,potentially,over45lbs.(200N)of"suction"availabletoholditback,whilea3"rockethasover100lbs.(460N)!TheoldCenturi"Point"wasaninfamousBernoullilockerwhenlaunchedfromanEstesPorta-Padwithitsperfectlymatchingroundblastdeflector.

Binder(propellant):Atwo-partmaterial,whichbindstheconstituentelementsofacompositepropellantintoasolid(usuallyrubbery);providesthefuelforthecompositepropellant;(See“HTPB”and“PBAN”)

BlackPowder:Basically,gunpowder.The'traditional'modelrocketmotorfuel.UsedbyEstesandmostothermodelrocketcompaniestoproduceAthroughFmotors.(Seealso"AP",“APCP”and"CompositeMotor")

BlackRockSociety(BRS):AnamateurrocketryorganizationfoundedbyTomBlazanintocatertothosewhofindHPRconfining.Itisaseriousorganizationforthosededicatedindividualswhowishtoexplorerocketryinasemiprofessionalvein.Itisopentoallformsofreactivepropulsion:solid,liquidandhybrid.Themailingaddressis:Route1,Box100Loving,TX76460Phone:817-378-2590FAX:817-378-2593

BlastDeflector:Anangledorflatplateorotherdevicethatpreventstherocketmotorexhaustfromdirectlyimpingingonthegroundandprotectsflammablematerialslikegrass;surroundingalaunchpad,frombeingignitedbytherocketexhaust.RequiredbytheSafetyCode.

Blow-By:Amotormalfunctionwherethehotmotorgassesescapepastthedelaygrainandigniteamotorejectionchargeprematurely,manytimes,causingdamagetotherocket.Oftenhappensatmotorstart-up.

Blow-Out:Failureofoneormoreparachutecanopypanelscausedbyexcessiveloading,eitherbytheopeningshock;i.e.,rockettooheavyforthatsizeparachuteorrocketistravelingtoofastwhenparachuteopens;“Therocketblewoutitsparachute!”(Seealso“Strip”and“Shred”)

Blow-Through:Thephysicalejectionofpropellant,manytimesburningthroughthefrontoftherocketbodycausedbyaforwardclosurefailure.Usuallyhappensatmotorstart-up.Usuallyverydamagingtotherocket.

BoatTail:Atransitionsectionatthetailoftherocket,whichgraduallynarrowsthebodydowntothemotordiameter.Usedtoreducebasedrag(q.v.).Alsoknownasatailcone.

BonusDelay:Slangforanunexpectedlylongdelay,sometimesresultingincrashing,airframedamageorparachutestripping.See“Zipper”

BoostedDart:Amethodofmaximizingaltitudeforanygivenimpulsemotor.Asub-minimumdiameter,unpowered"dart"sectionweightedforOptimumMass(q.v.)isplacedontopofthepoweredsection.Atburnout(maximumvelocity)thedartisreleasedandcoastshigherthanevenaminimumdiameterrocketcouldduetoitssmallcrosssectionalarea.Thistechniqueisusedinprofessionalsoundingrockets(e.g.SuperLoki)aswellashobbyrocketry.

Booster:Onamulti-stagerocketthisreferstothesections(stages),whichdropoffinmid-flight.Onsinglestagerockets,thetermisusedforthelowerpoweredportiontodistinguishitfromtherecoverysystemand/orpayloadsection.(Seealso"AirStart")

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BOR:BurnedOutRocketeer(facetious).CounterpointtoBAR(q.v.).Someonewhohasbeengoingatthehobbytoointensely,suchasinpreparationforamajorlaunch.

BridgewireIgniter:Atypeofigniterforcompositerocketmotors,whichusesathinnichromewire,solderedtoheavierleadwire(oftencalled“shooterwire”)andcoatedwithapyrogen,whichigniteswhenvoltageisputacrosstheleadscausingmotorignition.

Bulkhead:Asolidpartitionintherocket,especiallyonesetperpendiculartotherocket'slongaxis,designedtonotallowgasestopass.

Burn:Descriptivetermusedinconjunctiontotheoperationofarocketmotor.AlsousedinaphrasebyResearchrocketeers;“hemakesandburnspropellant”orjust“heburnspropellant”.

BurnArea:Theactivelyburningsurfaceofarocketmotorgrain,eithersolidorhybrid.

BurnRate:Therateatwhichasubstanceisconsumedbyburning,suchaspropellant.Insolidrocketmotors,therateatwhichtheburningsurfacerecedesasitcombusts.Affectedbypressure,temperatureandthescrubbingofthepropellantsurfacebyhotgases.

BurnRateCoefficient-BRCoef(a):Apropellantcharacterizationvalueandisdefinedasthe“rateconstant.”Thevalueofadependsofparticlesizeoftheoxidizerandsolidfuelandgenerallyindicateshowtemperatureaffectstheburnrate.

BurnRateExponent-BRExp(n):Apropellantcharacterizationvalue,representsthe“molecularity”anddescribestheburnrateofthepropellantatagivenchamberpressure.

BurnRateCatalyst:Anadditiveusedtoincreasetheburnrateofapropellant(suchasironoxide).

BurnRateModifier:Anadditiveusedtoincreaseorreducetheburnrateofapropellant.

BurnRateSuppressant:Anadditiveusedtoslowtheburnrateofapropellant(oxamideisanexample).

BurnTime:Theactualoperatingtime,orthetimethatittakesforarocketmotortofullyexpenditsfuelinseconds.

Burnout:Thepointatwhichpropellantisexhaustedinarocketmotorandthethrustdropstozero.

BurnOutVelocity:Thevelocitytherocketistravelingwhenthemotorrunsoutoffuel.Usuallythehighestspeedachievedbytherocket.Seealso"HyperterminalVelocity"

CA:Cyanoacrylate('superglue').Averystrongadhesivepopularforuseinhighpowerrockets,aswellas'onthefield'repairs.ThethreemostcommonformsofCAareoftenreferredtoas'hot','gapfilling'and'slow'.HotCAisverythinandhasstrongwickingproperties.Itdriesinonlyafewseconds.GapfillingCAisalittlethickerandgenerallycomesin15-30secondbondtimes.SlowCAformsthestrongestbondbutitsbondtimesarealsomuchlonger.Hotorgap-fillingCAisoftenusedtotackpartsintoplacepriortoapplyingastrongeradhesivewithamuchlongerbondingtime(suchasanepoxy).

CAR:TheCanadianAssociationofRocketryandit'sessentiallytheCanadianversionoftheNARandTripoliRocketryAssociationallrolledintoone.

C-Slot:Afuelgraingeometrywherethegrainhasaradialslotcutonitsedge;theburnisrelativelyneutraluntiltheend.

Caliber:Inrocketry,thediameterofthemainbodytube.Usuallyusedwhenreferringtosomefunctionoflength,e.g."TheCPshouldbebehindtheCGbyatleastonecaliber."Thetermisborrowedfromthesmallarmsindustrywhereitreferstotheboreofarifleorpistolbarrel,e.g.a.38caliberpistolhasabarrelwitha.38"bore.Notethatinlarge

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artillery,caliberreferstotheratioofbarrellengthtobore.Forexample,a3inch40calibergunwouldhaveabarrel120incheslong.

CandyFuel:(See“SugarMotor”)

Canopy:Thefabricofthetopofaparachute,whichcatchesair,slowingthedecentoftherocket.Canbemadeofrip-stopnylonorinthecaseofmanysurplusparachutes,silk.

CapacitiveDischarge:Atypeoflaunchcontroller,whichusesalargecapacitortostoreelectricalenergyfromabattery.Whencommandedbythelaunchcontroller,thecapacitordischargesalargecurrentintotheigniter.Thesecontrollersareoftenusedwithlargeclusterrocketstoensureallmotorsignitesimultaneously.

CaseBonded:Propellantwhichiscastdirectlyintochamberandmadetobondsecurelytothechamberwallinamonolithic(onepiece)grain.

CastingCap:AcastplasticormachinedmetalcapofdifferentmotordiametersusedforthecastingofpropellantbyResearchrocketeers.Manytimeswithholescorrespondingtothedifferentmotorcorediameters.

CastingTube:Atubeinwhichcompositepropellantiscast,typicallycardboard,phenolicorfiberglass.

CATO:Amotorfailure,generallyexplosive,whereallthepropellantisburnedinamuchshortertimethanplanned.Thiscanbeanozzleblow-out(loud,butbasicallyharmless),anend-capblow-out(whereallofthepyrotechnicforceblowsFORWARDwhichusuallydoesaprettygoodjobofremovinganyinternalstructureincludingtherecoverysystem)oracasingrupturewhichhasunpredictable,butusuallydevastating,effects.AnotherformofCATOisanejectionfailurecausedbyeitherthedelaytrainfailingtoburnortheejectionchargenotfiring,buttheresultisthesame:themodelprangs.ACATOdoesnotnecessarilyburnallofthefuelinarocketmotor(especiallytrueforcompositefuels,whichdonotburnwellwhennotunderpressure).ForthisreasonyoushouldbeespeciallycarefulwhenapproachingaCATO.

Origin:Opinionsonthemeaningoftheacronymrangewidely.Somesayit'snotanacronymatall,butsimplyacontractionof'catastrophic'andshouldbepronounced'Cat-o'(whichsoundsbetterthan'cata'overPAsystems.Othersmaintainthatitisanacronymbutdisagreeonthemeaning,offeringabroadspectrumof'CAtastrophicTakeOff,''CatastrophicallyAbortedTakeOff,''CatastropheAtTakeOff'andtheselfreferential'CATOAtTakeOff.'Theacronymcrowdpronouncesit'Kay-Tow',liketheGreenHornet'ssidekick.Ithasbeenpointedout,though,thatalloftheaboveare'post-hoc'definitionssinceLCO'swereusingthetermoverrangePAsystemslongbeforeanyformalacronymwasestablished.

OpinionsontheoriginssaythatitiseitherfromthemilitaryrocketprogramsofWWII,thepostwardevelopmentera,orevenamodroc-onlyterm,whichoriginatedwiththeMESS(MalfunctioningEngineStatisticalSurvey)performedbyNAR'sStandardsandTestingcommittee.ThereisalsoaclaimthatitstartedwiththeBostonRocketClubandthatthespellinghasevolvedovertheyears.Itsupposedlystartedoutas‘KATO’,which,ofcourse,stoodforKABOOMAtTakeOff!

CenturiEngineeringCo:Estes'IndustriesmaincompetitorinthemodelrocketbusinessuntilDamonpurchasedboththemandEstesinthemid-70’s.Centuricontinuedtooperateuntil1980.CenturiwasnotableastheyproducedlargeblackpowderD,EandFmotorsandahighpowerkitline.In1970theypurchasedtherightsandtechnologytomakecompositeEandFmotorsfromRocketDevelopmentCorp.,whichlaterbecameknownas“Enerjets”.

CHAD:AcronymforCHeapAndDirty.Usedtorefertoaquickandinexpensive(butusuallyinelegant)waytosolveaparticularproblemorproducesomeendresult.

CHADStaging:Asimpletechniqueusedtomakeamulti-stagerocketoutofasinglestagevehicle.Aboostermotoristapedtotheendofthestandard,singlestagemotorintherocket.Theboosteristotallyexternaltotherocket.Theboosteristhenignitedintheusualmanner.Thistechniqueonlyworkswithblackpowdermotors.Itwillonlyworkwith

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modelsthatareVERYover-stabletobeginwith.WhenCHADstagingdoeswork,however,itisthemostefficientstagingmethodbecauseitminimizesincreaseddragandmassassociatedwithanaddedstage.(See“OptimumMass”)

ChamberPressure:Thepressuregeneratedwithinamotorbythecombustionoftherocketpropellant(s).

CharacteristicSpecificImpulse(Isp*)Char.ISP:Theexpectedpropellantperformanceinsecondsnotincludingnozzlecontribution.ThisisnotthesameasDeliveredISP.

CharacteristicVelocity(C*):lsocalledc-starorsimplyc*,isafigureofthermochemicalmeritforaparticularpropellantandmaybeconsideredtobeindicativeofthecombustionefficiency.

Chuff:Aformofunstablecombustionmarkedbybriefburstsofthrustseparatedbyperiodsofnothrust.Typically,theburstscomefasterandbecomelongerasburningproceeds,untilstableburningresults.Thesoundofchuffingissimilartothatofasteamlocomotivestartingup.Itgenerallyoccursinacompositemotorthatisignitedtoolowinthegrain.Chuffingcanbedangerous,sinceashortburstofthrustcanlaunchtherocketoffthelaunchrod,andalullimmediatelyfollowingtheburstcanputtherocketontheground.Whenstableburningensues,sucharocketwillbeflyinghorizontally.(See"LandShark")

CG:CenterofGravity.Thepointaboutwhichafreebodywillrotatewhendisturbedbyanoutsideforce.Foramodelrocket,thisisthepointwheretheeffectsthemassesoftheindividualcomponentscanceloutandthemodelwillbalanceonaknifeedge.Aswithasee-saw,amassfurtherfromtheCGwillhaveagreatereffectthanthesamemasscloserin.

ClassBMotor:Rocketmotorscontainingmorethan62.5gramsofpropellantormotorsthatimpartmorethan120newton-secondsofthrust.

ClassCMotor:Rocketmotorscontainlessthan62.5gramsofpropellantorimpart120newton-secondsofthrustorless.

ClipWhip:Anumberofmicroclipsonshortwires(usuallythree)allconnectedattheirfreeend.Usedtoaidintheignitionofclusters(q.v)whereeachmotorusesaseparateigniter.

Closure:Foreoraft.Referstotheendsofareloadablerocketmotor.Aftbeingthenozzleendandforebeingthetoppartofthemotor,eitherasolidbulkhead(plugged)orwithapyrodelayelementandblackpowderejectioncharge.

Cluster:Arocketthatfiresmorethanonemotorsimultaneously.Atechniqueoncewidelyusedbeforetheadventoflargercompositemotors.(Seealso"ClipWhip"and"DavisDouche")

CoastPhase:Thatpartoftherocket'sflightbetweenburnoutandtheairstartofthenextstageorbetweenburnoutandactivationoftherecoverysystem.

CombustionChamber:Thepartofthemotorwheretheactualcombustionoccurs.Compositefuelsrequireasetpressureinthecombustionchambertocontinueburningattheproperrate.Failuretomaintainthepressureresultsinchuffing.

CompositeMaterial:Hi-techmaterials,otherthanpaper,woodormetal,suchasfiberglassorcarbonfiber,usedintheconstructionofrockets.(See"Phenolic")

CompositeMotor:Thetermusedbroadlytocoversolidfuelrocketmotorsusingpropellantsotherthanblackpowder.CanincludemotorsusingAP,KNorANasoxidizers.Compositemotorsrequiredifferentignitersandignitionsystemsfromblackpowdermotors.

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CompositePropellant:InHobbyRocketry,anypropellantotherthanblackpowder.Inmilitaryparlance(wherethetermoriginated)thetermisusedtodenotepropellantsthataremixturesofoxidizersandfuelsandtodistinguishthemfromSingle,Double,andTriplebasepropellants(whichareeithermonopropellantsormixturesofmonopropellants).Notethatbythemilitarydefinition,blackpowderisitselfacompositepropellantbecauseitconsistsofseparateoxidizers(KNO3andsulfur)andfuel(charcoal).Furthernotethatbythehobbydefinition,single/double/triplebasepropellantsarecompositesbecausetheyarenotblackpowder.Noambiguityarises,however,sincethemilitarydoesn'tuseblackpowder(inrockets,anyway),andnohobbyrocketmotorsusesingle,doubleortriplebasepropellants.(Seealso“APCP”,"SingleBasePropellants","DoubleBasePropellants"and"TripleBasePropellants")

ConfirmationCertification:TheprocesswherebyamemberofTripoliortheNARbecomescertifiedaseligibletopurchasehighpower(Handup)motors.

Coning:Anunstableflightconditioninwhicharocket'sspincausestherearportionoftherockettodescribeacircle.Coninggreatlyincreasesaerodynamicdragandreducespeakaltitude.

ContinuityCheck:Agroupofelectricaltechniquesforcheckingthefiringcircuitthroughtheignitertoensurethatthecircuitisfunctional.Thisusuallyinvolvessometypeoflightoraudiotoneactivatedbyapush-button.Thetechniquesrangefromasimplecurrentlimitinglightbulborbuzzerplacedinserieswithnichromeigniters,tosophisticatedbridgecircuitsforsensitive,lowcurrentflashbulbsandelectricmatches.

CopperheadTM:ThetrademarknameforanigniterproducedbyAeroTech,Inc.Itisalaminatedassemblyconsistingofatwocopperfoilstripsseparatedbyaninsulator,withaquantityofpyrogeniccompoundononeend.Itnormallyrequiresaspecialclipforelectricalconnections,butsomerocketeershavemasteredthe"Z-Fold"whichallowsuseofnormalalligatorclips.Notoriouslyunreliable,particularlyin24mmmotors.

Core:Thecavitywithinasolidorhybridpropellantgrain,mostoftencylindricalbutoftenstarorwagonwheelshapedtoofferhigherburningsurfaceoraconstantsurfacewithregression.(See“coreburner”and“moonburner”)

CoreBurner:Arocketmotor,whichhasanopencore,oftencylindrical,inthecenterofthepropellant.Thisallowsforignitionatthetopofthepropellantstackandburningofagreaterpropellantsurfaceareaallowinghigherthrustlevelsthanan“endburner”.

CoreSample:Synonymsdescribingafailuremodewherethemodelcomesdownfastandhard(nosefirst)andendsuptail-highintheground(thisiswherelarge,colorfulfinscomeinhandy.Oftenthenoseconehasseparated(takingtherecoverydevicewithit)andthebodytubeendsupcontaininganice'coresample'ofmud/dirtwhenpulledoutoftheground.Alsoknownas:AugerIn,cameinBallistic,LawnDart,TentPeg,YardDart.

CP:Centerof(Aerodynamic)Pressure.Thepointonarocketwherestability-restoringforcesduetoairflowagainstthebackpartoftherocket(fins,etc.)exactlyequalthedisturbingforcesagainstthepartoftherocketaheadofthatpoint.Agoodruleofthumbforsportmodels(bothhighandlowpower)istodesigntherocketwiththeCPoneortwobodydiametersbehindtheCG.

CPSC:ConsumerProductSafetyCommission.Thegovernmentagency,whichhasthetaskofdecidingwhetherornot,agivenproductissafefor'generalconsumer'use.

CruiseMissile:Arocketflightthathasfailedinsuchawaythatitendsupflyinghorizontallywhilestillunderpower.Acommonexamplewouldbeaclusterrocketthatdidn’thaveallmotorsignitingoramulti-stagerocketwhichstages"dirty"(duetostabilityorstructuralproblems)causingtheupperstagetobendtonearhorizontalatignition.Severelaunchrodtipofforhighwindshavealsobeenknowntocauseacruisemissileattitude.

Curative:Thechemicalcompoundusedto“cure”orhardenepoxycompoundssuchasfiberglassorpolyesterresins,whichuseMEKperoxideorthepropellantbindersHTPBorPBAN,whichuseisocyanatecompounds.Thecurativeforpropellantbinderscancauseallergicsensitizationwithrepeatedexposures,orlungdamagean/ordeathwithingestion

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orinhalationsocautionmustbetakenwithuse.Certaintwo-partpaintsandexpandingpolyurethanefoamsalsouseisocyanatesforacurative.

DavisDouche:Amethodofignitingclusteredmotorsbyusingapieceoffuseineachmotorwithallfusesdroppingintoapieplatethathasbeendustedwithblackpowderandtapedtothebottomofthemodel.Asingleigniterintheblackpowder"flashesthepan"ignitingallthefusesatonce.Developedintheearly'60sbyJoelDavisanddetailedinanearlyModelRocketryMagazineinlate1968orearly1969.Alsocalled“flash-in-the-pan”ignition.Thismethodwasusedfortherecord169motorclusterignitionatLDRS-3.

Degassing:Theprocesswheregasbubblesareeliminatedfromapropellantmixtureafterthecurativeisaddedbutbeforethepropellantiscast.Thisisdonetoeliminatevoidsinthecuredpropellant,whichcanaffecttheburnrate.Themixedpropellantissubjectedtoahardvacuum,whichcausesmuchofthesuspendedgasandevengasheldinsolutiontobeeliminatedfromthemixture.Professionalpropellantmanufacturerswillmixandcastthepropellantundervacuum.

DelayTrainorDelayCharge:Pyrotechnicmaterialintherocketmotorwhichburnsslowlybetweenthepropellantchargeandthefiringoftheejectioncharge.Thisallowstherockettocoasttowardsapogeeandslowdowntodeploytherecoverysystematlowspeed.Italsogeneratessmokethatallowstheflyertotrackhisrocketataltitude.

Density:Themeasuredpropellantweightinpoundspercubicinch(lb/in3).

DeploymentBag:AbagconstructedofsomefireproofmaterialsuchasNomex,inwhicharocket'sparachuteispacked.Thebagservestoprotecttheparachutefromhotdeploymentchargegasses,andassistsintheorderlydeploymentoftheparachutetopreventshroudlineandshockcordtangling.

DogBarf:Slangforflameretardantcelluloseinsulation,asusedasrecoverywaddinginlowandmid-powerrockets.Replacedfiberglassinsulationaswaddingbecauseofenvironmentalconcerns.(See“Wadding”)

DOT:USDepartmentofTransportation.TheFederalagencyresponsibleforregulatingallgroundandairmaterialtransportationintheUS.Allcompositerocketpropellantneedstobe“DOTCertified”beforeitcanbesoldandshipped.

DoubleBasePropellant:Asolidpropellantconsistingoftwomonopropellants(usuallynitroglycerinandnitrocellulose)andvariousadditives.Doublebasepropellantsareusedassmokelesspowdersinammunition.Theyarealsousedinsmallermilitaryrocketsbuthavebeenlargelyreplacedbycompositesinlargervehicles.Doublebasepropellantsarenotusedinhobbyrocketry.Seealso"CompositePropellant"

DQ:Disqualifiedflight.(Seealso‘MidwestQualified’)

DragCoefficient(Cd):Adimensionlessnumberusedinaerodynamicstodescribethedragofashape.Thisnumberisindependentofthesizeoftheobjectandisusuallydeterminedinawindtunnel.ItispartofthebasicdragequationF=.5*rho*V^2*Cd*AwhereFisthedragforce,rhoistheairdensity,VistheairvelocityandAisthecrosssectionalarea.Allofthese,exceptCd,aredirectlymeasurableinawindtunnelsoCdcanbethoughtofthe"fudgefactor"thataccountsforalloftheaerodynamicpeculiaritiesofashape.TheCdformostsporttypehobbyrocketsisintherangeof.4to.5.(Seealso"ReynoldsNumber")

DragFormFactor(CdA):TheDragCoefficient(q.v.)ofanobjectmultipliedbyitscrosssectionalarea.ThisisusedtoscalethedragvalueforaparticularobjectfromthedimensionlessCd.Theoretically,everyobjectofasimilarshapewillhavethesameCdregardlessofitssize,meaningthatbothagrainofriceandaZeppelinwouldbethesame.Multiplyingbytheareaallowscomparisonsofthetruedragbetweendissimilarobjects.(Seealso"OptimumMass")

DragRace:Anevent,usuallyinformal,inwhichmultiplerocketsarelaunchedsimultaneously,usuallythesamerocketkitwiththesamesizeandtypeofmotor.Thiscanbespectaculariflargeand/orsparkymotorsareused.

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DragRecovery:Recoverymethodusingtheshapeofthemodeltoslowthemodeldownenoughforsaferecovery.Usedonlyinsmallmodelrockets.AlsocalledTumbleRecovery.Lowerstagesofmulti-stagemodelrocketsusetumblerecovery.

DragSeparation:(See“LovelaceEffect”)

DrogueParachute:Small,heavilyreinforcedparachutedesignedtoslowtherocketsosafereleaseofthelargermainchute(s)ispossibleatloweraltitudes.(See“DualDeploy”)

DropStaging:Inamulti-stagerocket,thedroppingofairframe/finsectionswithexpendedrocketmotorsduringflight.Two,threeandfourstagerocketsarenotuncommon.Onlow-powerrockets,thestagesareusuallylightenoughasnottowarrantarecoverysystemforeachstage,butthisismandatoryforhigh-powerrockets.Alsooncereferredtopoweredsidepodswhichwouldseparatefromthemainairframeuponburnoutbyaerodynamicdrag.ThistechniqueisnotlongerallowedbytheTRA.(See“CHADStaging”)

Dual-Deploy:Amethodofrecoveryforhighpowerrocketwithemploysanelectronictimeroraltimetertodetectapogeewhereasmallblackpowderchargewillseparatetherocketandasmallparachutewillslowitsdecenttoaloweraltitudewherethemainparachutewilldeploy.Thiseliminateslongwalkstorecoverrocketsinhighwinds.

EffectiveExhaustVelocity:(See“Impulse(Relative)”)

Ejection:Referstotheactualseparationoftwopiecesoftherocketairframeatapogeecausedbyapyrotechnicchargeormechanicalsystemandthedeploymentofarecoverydevicefromarocket.The“ejectiondelay”istheamountoftimebetweenmotorburnoutandthedeploymentoftherecoverysystem.Alsoreferredtoasan“ejectionevent”.

EjectionBaffle:Adeviceusedinsomerocketstoeliminatetheneedtousewaddingtoprotecttherecoverysystem.Usuallycomposedofsometypeofmetalwoolormeshtoabsorbtheheatandburningparticlesoftheejectiongasesbeforetheyreachtherecoverycompartment.Withextendeduseitcanclogandbecomeafirehazard.Orcanberestrictiveifdesignedpoorly,preventingeasyorfullrecoverysystemdeployment.Usuallyonlyusedinmid-powercommerciallyproducedrocketkits.

EjectionCharge:Asmallquantityofblackpowderusedtogeneratepositivegaspressurewithintherocketairframetodeploytherecoverysystem.Thisisactivatedwhenthedelaytrain(q.v.)burnsthrough.Onrocketswithelectronicejectiontimers,thismaybeaseparatesmallcontainerofblackpowder,whichistriggeredbyasignalfromaradiocontroldevice,timeroraltimeter.

ElectricMatchorE-Match:Atypeofigniteroriginallydesignedtosetofffuse-typeblastingcaps(i.e.amatchthatcanbesetofffromagreatdistanceelectrically).Itrequiresaverylowelectricalcurrent(~50mArange)toactivate.PurchaseandstorageofelectricmatchesrequiresaLEUP.(See“Squib”)

End-Burner/End-Burning:A"cigaretteburning"graininhibitedorcasebondedontheexternalsurfaceburningonlyonitsface.Mostblackpowdermotorsareend-burners,or“coredend-burners”.Compositeend-burnersdidn’texistuntilCompositeDynamicsreleasedtheE9motorin1980.Compositeend-burnersarecommontoday.Alsousedtodescribeacertaintypeofcompositemotorignitionmalfunction;thatisignitingthemotoratthebottomofthecoreinsteadofthetop.

Enerjet:AdivisionofCenturiEngineeringCompanythatproducedcompositerocketmotorsandhighpowerkitsfrom1970to1975.Atthetimeallrocketkitswerelimitedtoaone-poundtakeoffweight,sothemodelswouldhaveseemedverysmallandfragilecomparedtomodernhighpowerrockets.EnerjetkitsandmotorsareverycollectabletodayandhavebeenclonedbyNorthCoastRocketry,Semrocandothers.

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Engine:Amachinethatconvertsenergyintomechanicalmotion.Suchamachineisdistinguishedfromanelectric,spring-drivenorhydraulicmotorbyitsconsumptionofafuel(from*AmericanHeritageDictionary*).Atermoftenusedincorrectlyinplaceofrocket“motor”.

ErosiveBurning:Increasedburningrateinsolidandhybridrocketmotorscreatedbytheactionofhighvelocitygasesoverthesurfaceofthecombustingpropellant.

EstesIndustries:Oneofthefirstcompaniesthatstarteditallin1959whentheyintroducedtheScout,atumblerecoveryrocketwhichwasthiscompany'sfirstmodelrocket.TheygottheirstartbyfirstproducingtheblackpowdermodelrocketmotorsforHarryStine’scompany,ModelMissiles,Inc.,whotheylaterboughtout.Estesiscurrentlythelargestmanufacturerofmodelrocketsintheworldatthistime.

EstesDent:Asemicirculardeformationoftheleadingedgeofthebodytubecausebythenoseconesnappingbackandstrikingthebodyatejection.Theproblemisintensifiedbyshortshockcords,whichdon'tabsorbasmuchenergybeforereversingandgivethenoseaclosertargetwithbetteraim.Sonamedduetothatcompany'spolicyofprovidingveryshortshockcordsintheirkits.

Event:Somethingthathappenstotherocketduringflight,suchasairstartingofmotors,staging,apogeeseparationormainparachutedeployment.Notalwaysagoodthing.(See“Shred”)

ExpansionRatio:Theratiooftheareaoftheexitdiameteroftheexhaustportionofanozzletotheareaofthethroat-determinesCf(thrustcoefficient).

ExperimentalRocket:(See"AmateurRocket")

ExperimentalRocketry:(See“ResearchRockety”)

ExperimentalSpacecraftSociety:Anamateurgroupwhosepurposeistoorbitasmall(10"to16")telescopeforusebyamateurastronomers.Whilenotdirectlyinthepropulsionendofexperimentalrocketry,itisverymuchinthesamephilosophicalvein.DirectorisLindaKenny-Sloanwhocanbereachedat:

ExperimentalSpacecraftSociety17701SouthAvalonBlvd.Carson,CA90746Internet:[email protected]

FAA:FederalAviationAdministration.ThisistheorganizationthatgovernsairspaceintheU.S.

FAR101:TheFederalAviationRegulationbywhichtheFAAdeterminestheprocedurestobefollowedforlaunchingnon-professionalrockets.Theruleisquiteinvolvedandbeyondthescopeofthisdocumentbutbriefly,itdividesthehobbyintothreecategoriesforthepurposeofregulation:

1)Modelrocketswithagrosslaunchweightoflessthan1poundorcontainingmotorswithlessthanatotalof113gramsoffuelareexemptfromFAAinvolvementiflaunchedmorethan5milesfromanFAAcontrolledairport.

2)LargemodelrocketswhichexceedtheFAAdefinitionofamodelrocketbutotherwisefallwithintheNFPA1122definitionof"model"(i.e.,between1and3.3poundsliftoffweightandbetween113and125gramsoftotalfuel)mustnotifythenearestAirTrafficControlcenter(ATC)between24and48hourspriortothelaunch.TherearefurtherrestrictionswhenlaunchingwithinfivemilesofanFAAcontrolledairport.

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3)Highpowerrockets(weighingmorethan3.3pounds,containingmotorswithatotalofmorethan125gramsoffuel)requireaformalwaiverbeapprovedbytheFAAandactivatedpriortothelaunch.TherearefurtherrestrictionswhenlaunchingwithinfivemilesofanFAAcontrolledairport.

FAI:TheFederationAeronautiqueInternationale.AninternationalorganizationlocatedinParis,Francethattracksworldrecordsforaeronauticsandaeromodeling.

Fiberglass:Aman-madematerialconsistingofglassfibersspunandwovenintoamat-likeclothadheredtoarocketwithepoxyresins.Itisusedtoaddstrengthtohighpowerrockets,sothattheycanwithstandhigher-poweredmotorsthantheyotherwisecould.Althoughfiberglassisacommonlyusedword,itisactuallyatrademarkofOwen-CorningInc.

Fillet:Areinforcementofthejointbetweenthefinandthebodytubeoftherockettoimprovetherocket'saerodynamicsandtostrengthenthefinmount.White(Elmer’s)glueisoftenusedinmodelrocketsbutinhighpowerrocketsepoxyistheglueofchoice,oftenmixedwithmicro-balloonsoranotherfiller.(Seealso"TTW")

Fins:Areusuallyplanarsurfacesplacedatrightanglestothebodytubeandprovidestableflight.Canbemadeofbalsa,plywood,fiberglass,carbonfiberoraluminum.Withoutfins(orotherspecialarrangements),therocketwillnotflyinastraightline.

FIREBALLS:Alsocalledjust“BALLS”.Anexperimentalrocketry/HPRlaunchhostedbyAERO-PAC(q.v.).Againstthewishesofitsfounder,"Fire"wasplacedinfrontof"BALLS"from1993-95toplacatethosefewwhohadaproblemwiththename.The1993FIREBALLSwassponsoredbyTripoliforthepurposesofinsurancecoverage,andafterthattheydecidedto"adopt"theeventwithanamechange.

FlameBucket:Anopeningatthebaseofalaunchpadtoallowtheexhausttovent.Onesideisangledtoformablastdeflectortopreventtherocketexhaustfromdirectlyhittingtheground.

FlameproofRecoveryWadding:MostoftenreferstothechemicallytreatedtoiletpapersoldbyEstesIndustriesforprotectionoftheplasticparachutesfromejectiongasesintheirmodelrocketkits.Notusedinlargeorhighpowerrockets.

Flashbulb:Amagnesiumandoxygenfilledglassbulb,oncecommonlyusedinfilmphotography.Inrocketry,flashbulbsareusedtoignitethermalitefusesorblackpowderchargesforsecondstageignitionorrecoverydevicedeployment.Theyhavetheadvantageofrequiringverylowvoltageandcurrenttofirethem(usuallyonly3v).However,thisattributealsomakesthemsusceptibletoaccidentalactivationbystaticelectricity.Manypreferusingflashbulbsinsteadofelectricmatchesforrecoverysystembecauseoftheoccasionaldifficultyinobtainingelectricmatches.

Flash-in-the-PanIgnition:(See“DavisDouche”)

Free-fall:Thefallofanobjectwithoutguidanceorretardationotherthanthroughdrag.Usuallynotagoodthing.

FrictionFit:Thejoiningoftwoobjects,relyingnotonadhesivebutontheinterferencefitcausedbyoneobjectbeinginsertedintoanother,suchasthenoseconeinsertedintoabodytube.FSI-FlightSystemsInc.:A1960’srocketcompanynotedfortheirlargeEandFblackpowdermotors,called“Loadlifters”.Alltheirmotorsdidn’tfollowthestandardsizeform-factor,withtheirA-Dmotorsbeing21mm(asopposedto18or24mm).TheirE60andF100motorswereoftenusedinclustersinearlyhighpowerrockets.TheyalsomaderocketmotorsforHollywoodspecialeffectscompanies.Thecompanyshutdownin1994.Restartedwithanewownerin2014buthavenoproductsavailabletodate.G-10:Agradeoffiberglasscommonlyusedforfinsonhighpowerrockets.G10designatesalaminatemadeoffiberglassclothlaidinepoxyresin.

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G-Switch:Amechanicaldevice,whichdetectsthepresenceofaccelerationthroughthemovementofaweightedelectricalcontact.G-switchesarenormallyusedincombinationwithotherelectronicdevicessuchasaltimetersandtimers.Glassing:Theprocessoflaminatingrocketcomponents,suchasfinsandbodytubes,infiberglasscloth,whichissoakedinepoxyresin.Thisprocessgreatlyincreasesthestrengthoftheitembeing“glassed”.GPS(GlobalPositioningSystem):Aposition/locationserviceprovidedbytheUSGovernmentviaaconstellationofLEOsatellites;goodforidentifyingtheexactlocationofyourlaunchsite;somenewerflightcomputersareprovidingaGPSinterface.Grain:Anysizeofmonolithicpropellantstructuredesignedtobecombustedasrocketpropellant.(See“BatesGrain”)

GSE:GroundSupportEquipment.Anythingyoubringtothelaunchsite,whichisnecessarytoflyyourrocket,butdoesn'tactuallyflywithit.Obviousexamplesarethelaunchpadandlaunchcontroller.ThetermwaspopularizedbyHyperTektodescribetheirhybridmotorlaunchsupportsystem.

HangFire/Misfire:Terms,whichrefertoabnormalignition.Withhangfire,themotorusuallyignitesafteraconsiderabledelay.Misfiresneverignite.Hangfiresoftenappearsasamisfireuntilthemotorignitessometimelater.Thisisthemainreasonthesafetycodeadvisesnottoapproachamisfiredrocketforoneminute.

HeadEndIgniter:Anigniterthatisinstalledonthetopofamotorinplaceoftheforwardendclosure;thistypeofigniteriscurrentlynon-standardbutisbeingusedexperimentally.Thisarrangementisnotuncommononprofessionalrockets.

HighPowerRocket(ry)(HPR):Hobbyrocketsthatexceedthetotalweight,totalpropellantorsinglemotortotalimpulserestrictionsofmodelrocketsasdefinedinNFPA1122(q.v.)butotherwiseconformtothesameguidelinesforconstructionmaterialsandpre-manufactured,solidpropellantmotors.Highpowerrocketshavenototalweightlimits,butdohaveasinglemotorlimitofnomorethanOpower(40,960NStotalimpulse)andhavealimitationof81,920NStotalimpulse.

HMR:TheHandbookofModelRocketry.TheofficialNARhandbookforthehobby.OriginallywrittenbyG.HarryStine(NAR#002)thefirsteditioncameoutin1965andcurrentlyinit'sseventhedition.IthasexpandeditsscopewiththehobbybyaddingcomputerprogramsinthefourtheditionandgivinganodtowardstheexistenceofHPRinthesixthedition.CurrentlybeingeditedbyBillStine(Harry’sson)afterHarry’sdeathin1997.

HobbyRocket:Ageneral,collectivetermusedtodescribebothmodelandHPRrocketstodifferentiatethemfromamateur/experimentalrockets.Alsocalled:HobbyRocketry,orinthecaseofmotors,HobbyRocketMotors.

HPRLite:Atermonceusedtodescriberocketsusingmotorsinthe'E','F',and'G'powerclasses.Nowcalled“Mid-PowerRocketry”.Itdescribesrockets,whichfallbetweentheoldNFPA1122weightlimitof1lb(454grams)andthecurrentmodelrocketweightlimitof1500grams.Rocketsinthe'E'through'G'classaren'tnormallyconsideredhighpowerrocketsbut,tobesuccessful,mustbebuiltusingmanyofthesameconstructiontechniquesasthelargerrockets.Also,anyrocketover3.3lbrequiresanFAAwaivertoflylegally.

HPRM:HighPowerRocketryMagazine-formerly“Tripolitan”(q.v.).Anolongerpublishedindependentmagazinedealingwithallaspectsofconsumerrocketry,butwithadefiniteemphasisonhighpower,advancedandexperimentalconsumerrocketry.Publishedsixtimesayear.AsubscriptionwasincludedwithmembershipinTripoli,butcouldbehadseparately.Alsoavailableonmagazineracksinlargerhobbystores.ReplacedastheofficialTripolijournalby“Rockets”magazine.PriortoHPRM,anotherhighpowerrocketrymagazinecalledsimply“HPR”waspublishedinOhiointheearly80’s.Moreakintoaclubnewsletterthananactualmagazine,ithadlimitedcirculation,similarinsizeandscopetoCaliforniaRocketrymagazine.

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HTPB:Hydroxyl-terminatedpolybutadiene;acommonbinderusedincompositerocketfuels.ThetwomaintypesofR45usedinAPCPareR45MandR45HTLO.(See“Binder”)

Hybrid:Referstotheuseofmixedstatesofmatterinabi-propellantsystem-solid-liquid,gas-solid,etc.Eitheroxidizerorfuelmaybetheliquidorgascomponent.

HyperterminalVelocity:Asituationwherearocketistravelingfasterthanterminalvelocity(q.v.)foragivenmotor.Thisispossible,forexample,withastagedmodelwithgrosslymismatchedmotorcombinationssuchasanFmotorstagedtoaBmotor.Atstaging,theupperstagewillalreadybebeyonditsterminalvelocityforthe"B"motor.Inthiscase,theupperstagewillactuallydecelerateduringthrustingandapproachesterminalvelocityfromabove.

Igniter:Anexpendableelectricallyinitiatedpyrotechnicdeviceusedtoigniteasolidrocketmotor.Compositemotorsrequireadifferenttypeofigniterthanblackpowderrocketmotors.

Impulse(Relative):Ameasureoftheefficiencyofarocketengine.SimilartoSpecificImpulse,itisdefinedastheTotalImpulse(q.v.)dividedbythemassofthepropellants.Alittledimensionaljugglingshowsthatthisgivesthesameunitsasvelocity(ft/secorm/sec)henceissometimescalled"EffectiveExhaustVelocity."Howquicklythereactionmassleavesthenozzleisagoodmeasureofefficiency.

Impulse(Specific):Ameasureoftheefficiencyofamotor/propellantsystem.ItisdeterminedbytakingtheTotalImpulse(q.v.)anddividingbytheweightofpropellants.Thiscarriesthepotentiallyconfusingunitsof"seconds"(asifithadsomethingtodowiththeburnduration)butisduetoweightandthrustbothbeingforceparametershencecancelingout(e.g.lb-sec/lborN-sec/N).Thisisactuallyveryhandysinceitmakesthetermindependentoftheunitssystem(metricorEnglish)sincetheybothuse"seconds"fortime.

Impulse(Total):Ameasureofthetotalmomentumimpartedtotherocketbythemotor.Itisdefined(forthosewhoknowcalculus)astheintegratedareaunderthethrust-timecurve.Fortherestofus,itcanbethoughtofasthemotor'saveragethrusttimesthedurationoftheburn.MeasuredinN-secorLb-sec.

Kato:NotoneofOJ’sfans.(See“Cato”)

Kevlar:Asyntheticfiber,originallywovenintomatsforuseinbullet-resistantbodyarmor.Kevlarishighlyresistanttotearingorburning.Kevlarthreadisusedinsomemodelrocketsasashockcord.Inmodelrockets,thisprovidestheadvantageofallowingthecordtobeanchoredtothemotormountratherthantotheopenendoftheairframe.Thisdesignislesssusceptibletozipperingandburning.Larger-diameterKevlarcordisincreasinglybeingusedasshockcordsonhigh-powerrocketsforthesamereason,andbecauseKevlarisstrongerthanbungeeorelasticstraps.Kevlarisalsowovenintosheathsorbags,andusedtoprotectelasticshockcordsandparachutesinlargerrockets.(See“DeploymentBag”)

Kicked:Atermusedtodescribeamotor,whichisejectedfromtherocketwhileinflightinsteadofejectingtherecoverysystem.Thisoftenresultsina“Prang”(q.v).Itisusuallycausedbynotfittingthemotorintothemotormountproperly.

Kitbash:Takingtwo(ormore)kitsandcombining("bashing")themintoanewdesign.Origin:Thetermappearstohavecomefromthemodelrailroadinghobbywherekitsforbuildingsandotherdioramaitemshave,fordecades,beenmodifiedfromtheiroriginalintenttosuittheneedsofaparticularlayout.

KN:Potassiumnitrate;theoxidizerusedin“sugarmotors”.Alsothedefinitionofthepropellantsurfaceburnareadividedbythethroatareaatmotorstartup(Kn).

KrushnicEffect:Averydramaticphenomenonwhereyourrocketmakesatremendousamountofnoiseandsmokebutdoesn'tgoanywhere!Thishappenswhenthemotorisrecessedintothebodytubebymorethanonetubediameter.Ifsorecessed,thecylindricalvolumebelowthemotorformsasecondaryexpansionchamber,whichallowstheexhaustgassestoexpandbelowatmosphericpressurebeforeleavingtherocket.Surroundingairaspiratedintotheexhaust

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streamcausesturbulence,whichnegatesmuchofthethrust,alongwithcreatingthecharacteristicroar.Amulti-stagemodelthatejectsitsboostermotor,butnottheairframe,isaperfectexample.NamedforRichardKrushnic,therocketeerwhocharacterizedtheeffectinthelate'60s.Nottobeconfusedwith"SuctionLock"(q.v.).

L!,L2,L3:Levelsonethroughthree:referencetothethreelevelsofhighpowerrocketrycertification.UnlessyouareinCanada,Eh?

LandShark:Arocketthathasfailedinsuchawaythatitendsuphittingthegroundwhilestillunderpower.Upperstagesofunstablemulti-stagerocketsoftenenduplikethis,asdosome(too)heavyHPRrocketswithlong-burning,lowthrustmotors,orclusterrocketsinwhichallmotorsdonotignite.

LaunchController:Anelectricaldeviceusedtoactivatethemotorigniter,whichinturnignitesthemotor.Thelaunchcontrollershouldalwaysincorporatealock-outdevicesuchasakey,topreventaccidentallyactivatingtheigniterbeforetherocketisreadytobelaunched.

Launcher:Alauncherisrequiredtoholdtherocketinaverticalpositionandguideitstraightduringthebeginningofitsflight(beforetherocketgainsenoughairspeedforthefinstotakeeffect).Themostcommonkindoflauncherisabasewithathinsteelrodattachedtowhichtherocketmountswitha"launchlug."

LaunchLug:Typicallyasectionof1/8”to¼”diameterpapertubingattachedtotherocketatitscenterofgravityandusedtoguidetherocketduringinitialpoweredflightbyasteelrodattachedtothelaunchpad.Usedprimarilyinlowandmid-powerrockets.

LaunchRail:Typicallyasinglesixoreightfootlongsectionof1”or1.5”80/20structuralrailusedinconjunctionwith“railguides”toguidehighpowerrocketsduringtheirinitialflight.Thelaunchrailhasreplacedlaunchrodsgreaterthan¼”onmostlaunchranges.Ithastheadvantageofbeingstifferandnotsuffering“rodwhip”duringpoweredboost.

TheLaundry:Slangtermforrecoverycomponents,especiallytheparachute(s).

LawnDart:Similartoa“CoreSample”butrequiresthenoseconetoremaininplacepriortoimpact.Namedafterapopular(butdangerous)lawngameofthesixtiesinwhichlargedartswerethrownintotheairtolandinsideringsplacedonthegroundabout25'apart(asinhorseshoes).

LinerTube:Usedinreloadablemotors.Atube,usuallypaperorphenolic,thatholdsthepropellantgrainsinsidethemotorcase.Actsasadditionalinsulationandprotectionforthemetalmotortube.

LCO:LaunchControlOfficer:theindividualresponsibleforsafeoperationofthelaunchrange.

LDRS:TheannualnationalhighpowersportlaunchsanctionedbyTripoli.LDRSstandsfor'LargeandDangerousRocketShips,'thederivationofwhichisbestlefttoothers.Note:LDRShasNEVERstoodfor'LetsDoRocketrySafely',despitewhatyouhearfromhistoricalrevisioniststryingtomollifypublicofficials.OriginatedinMedina,Ohioin1982.ThefirstfiveLDRSeventswereheldtherebeforemovingtoColoradoandotherstates.

LEUP:LowExplosivesUserPermit.ABATFEpermitpreviouslyrequiredtopurchasehighpowerrocketmotors.Nolongerneededformotorsbutstillneededforpurchaseofignitersandblackpowder.AMagazinePermitisstillneededtolegallystoreblackpowderandcertainigniters,includingelectricmatches.

LovelaceEffect:Aphenomenonwherethenoseconeisapparently"sucked"outofthebodyrightatmotorburnout.Itismoreprevalentonparabola,ogiveandotherlowdragnoseshapes.FirstobservedwithDualEggLoftmodelsusingtheCMReggcones.Thetheory(asyetunproven)isthatsincethenoseconehasmuchlessdragthanthebody,itsmomentumtendstocarryitforwardfaster(or,morecorrectly,thebody'sdragdeceleratesitmorequickly)puttingtensiononthenose-bodyjoint.Theconditionisexacerbatedbyanynoseweightsaddedforstability(whichalsoraisethemomentumofthenose)and/oraloosefitofthenoseinthebody.Anotherpossiblecontributingfactorcouldbe

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thedenserair(trappedinthebodytubefromgroundlevel)exertingpressureonthenoseconeoncetherocketreachesahigheraltitude.Thetermisnamedafteranearly'70spornographicmovieactresswhohadcertainoralskills.FirstcoinedbytheSNOARNARsectionwhowerefrequentDualEggLoftflyersandavidmoviegoers.

LowPowerRocketry:TypicallyrocketsflyingonmotorsintheAtoDrange,usuallyweighinglessthanonepoundor500grams.

MachDiamonds:Adiamondshapedpatternthatdevelopsinthesupersonicflowofgasfromarocketnozzle;thesearecausedbyshockwaves,whichreflectoffofthepressureboundarybetweentheexhaustplumeandtheambientenvironment.

MagneliteTM:AnignitermadebyRocketfliteusedmainlytostartcompositemotors.Amediumpowerdevice(2-3ampsat12volts),itrequiressignificantlymorethananelectricmatch(q.v.),butnotasmuchasaCopperhead(q.v.).Itconsistsofanichromebridgewiredippedinamagnesium-basedpyrogen,whichburnsveryhot(~6000F),aidingintheignitionofstubborncomposites,suchassparky,smokyorcertaincoloredeffectmotors.Theheadcanbequitelargesotheyworkbestinmotorswithlargernozzlesandcores.Sometimesusedasagenerictermtodescribeanyigniterpyrogen.

Mandrel:Arodorbar,usuallynylonorDelrinusedasacorearoundwhichamaterialismolded,cast,orwound;typicalusesinrocketryaretoformthecoreinapropellantgrain,tomakeanairframe,ormoldanosecone.

MarginalStability:Rocketswithastaticmarginbetween0.5and1.0caliberareconsideredtobe'marginallystable'.Theserocketsmayflyfine,butextraattentionmustbegiventothewindconditions,thrust-to-weightratio,andlaunchrodvelocity.Forexample,shortstubbyrocketswithalength-to-diameterratioofunder10typicallywillbestablewithunderonecaliberofstaticmargin.

MassLaunch:Alaunchoflargenumbersofrockets,usuallysmallmodelrockets,atthesametime.TheGuinnessworldrecordwascapturedbylaunching3,973modelrocketsatthesametimeonOctober29,2014,duringRocket4theCure,acampaigncreatedtoraise$20,000forbreastcancerresearchandawareness,accordingtotheWorldRecordAcademy.ThepreviousGuinnessWorldRecordsworldrecordwas3,130rocketslaunchedatthesametime.(Seealso“DragRace”)

Max-Q:Thepointduringthepoweredflightphaseofarocket'sascentatwhichaccelerationstressesontheairframearethegreatest.Thisisthepointatwhicha“Shred”ismostlikelytooccur.

MicroClips:Small,toothlesselectricalclipscommonlyusedtoconnectthelaunchsystemtothethinnichromeigniterwireonblackpowdermodelrocketmotors.LargertoothedclipsareusedinHPRbutusuallycalled“igniterclips”.

Mid-PowerRocketry:Thetermdescribesrockets,whichfallbetweentheoldNFPA1122weightlimitof1lb(454grams)andthecurrentmodelrocketweightlimitof1500grams.Rocketsinthe'E'through'G'classaren'tnormallyconsideredhighpowerrocketsbut,tobesuccessful,mustbebuiltusingmanyofthesameconstructiontechniquesasthelargerrockets.

MidwestQualified(flight):Duringthe1970's,NARcontestflyerscirculatedapersistentrumorthatmeetsheldontheEastCoastwereheldtoamuchhigherstandardofflightqualificationthanthoseflownintheMidwest.TheContestBoardsteadfastlymaintainedthatcontestruleswereuniformlyenforced.ThedifferencesinflightqualificationoccasionallysurfacedatNARAM.IfanRSOqualifiedaflightthatmanypeoplefeltshouldnothavebeen,hisortheflyer'sgeographicallocationcameunderscrutiny.Whilenorulechangesorproceduresweremodified,flyerscontinuetorefertothosemarginalflightssqueakthroughas"MidwestQualified."ThetermalsogainedpopularitywhenagroupofcompetitorsfromtheSNOARsectioninClevelandbeganofferingatNARAMthe"BestMidwestQualifiedFlight"award.AcollectionofwreckageofNARAM'sprangs,largeandsmall,wereattachedtoalargesheetofcardboard,alongwithlocalflora,fauna,touristbrochures,foodwrappers,etc.SNOARmembersthendecidedwhohadthebestprangofNARAM,andpresentedthe"trophy"tothe"winner"attheawardsbanquet.Nominationwascauseforpainenough,butwinningmadeonealegendinhisowntime.

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MIF:MissingInFlight.Arocketthatdisappearswithnosignoftherecoverysystemdeployment,andnootherobviousfailuremode(e.g.PrangorCATO).Sometimescalled"intoorbit."

MinimumDiameter:Arocketbuiltwiththesmallestpossiblediameterbodytubeforthesizeofmotorcasing.Usuallydonetoreducedraginsportorcompetitionmodelseventhoughitcanincreasethedifficultyofattachingfinsandrecoverysystems.(Seealso"BoostedDart")

Mini-Max:AlineofhighpowerD-FblackpowdermotorssoldbyCenturiEngineeringbeforetheintroductionoftheircompositeEnerjetline.Discontinuedin1969.CenturiboughtthetechnologyfromAtlasRocketMotorCompanyinthe1960’s,who,alongwithCoasterCorp.,madeblackpowdermotorsuptoGclass.

ModelRocket:Anaero-vehiclethatascendsintotheairbymeansofareactionmotor,butwithouttheuseofaerodynamicliftingsurfaces.Therestrictions,asdefinedinNFPA1122,areasfollows:Thegrosslaunchweight,includingmotor(s),willnotexceed1500grams.Motor(s)willnotexceed160NSofimpulse(total)and/orcontainmorethan62.5gramsofpropellanteach,andnomorethanatotalof125gramsofpropellantinmultiplemotorapplications(clustersand/ormulti-stages).Allcomponentsofsaidvehiclewillbeofwood,paper,rubber,andbreakableplasticorsimilarmaterialandwithoutsubstantialmetalparts.Seealso"FAR101"and"NFPA1122"

ModelRocketeer:TheoriginalNARnewsletter.FirstpublishedintheAMAmagazineasasinglecolumn.LaterpublishedasaninserttoMRM(q.v.)whileitlastedandthusavailabletonon-NARmembersforawhile.AfterMRMfolded,itwasagainpublishedstand-aloneandgraduallyexpandedtoamagazinestyleformat.Itbecame“AmericanSpacemodeling”(q.v.)inJuly1984,althoughtherecontinuedtobeasectioncalled"TheModelRocketeer"fortheNARpresident'scolumnandotherassociationnews(justlikeinMRM!)whichbecamethe"President'sCorner"in1992.Nowcalled“SportRocketry”.

Modroc:ModelRocket.Alsoseenas'modrocer',orsimilarspelling,tomean'modelrocketryenthusiast'.

Monopropellant:(See"SingleBasePropellant")

MoonBurner:Agraingeometrywherethecylindricalcoreisoffsetandtouchestheouterwallofthegrain;amoonburnerisregressivethroughoutitsburn.

Motor:Somethingthatimpartsorproducesmotion,suchasamachineorengine.Themotiveforcecausingarockettotaketoflight.Adevicethatconvertsanyformofenergyintomechanicalenergy(from*AmericanHeritageDictionary*).Solidfuelpropellantdevicesarecalled“motors”(despitewhatEstessays)becausetherearenomechanicalmovingparts,whichisthedefinitionofan“engine”.

MotorClass:ThecommercialmotorclassletterdesignationandtheaveragethrustinN-s.Alsoshowniswhatpercentage(%)ofthatletterclassthemotoractuallyis.

MRM:ModelRocketryMagazine-Anearlyattemptata"newsrack"stylerocketrymagazine.Itattemptedtodoforrocketrywhat“ModelRailroading”didforthathobbyor“RCModeler”didformodelairplanes,namelycreateaforumwherethewholeindustrycouldtalkdirectlytothehobbyistwithoutlimitinghimtoasinglecompany(e.g.theMRNorAR)ormakinghimjoinanorganization(e.g.theNAR).Whatitactuallyprovedwashowtinythehobbywasbackthenasitonlylastedabitoverthreeyearsfrom10/68through1/72thenquietlyfolded.Despitethecrudegraphicsandgenerallymarginalproductionvalues,themagazinewastreasuredbyitssmallbandoffollowersandcopiesareingreatdemandtoday.Photocopiesarecirculatedbyan"oldboynetwork"atmeetingsandswaps.Whileitlasted,italsoincorporated“TheModelRocketeer”theNARnewsletterthatlaterbecame“AmericanSpacemodeling”andstilllater“SportRocketry”(availableofftherackinlargerhobbyshops).“HPRMagazine”(q.v.),theTripolijournal,likewisestartedasacaptivepublicationforTRA,whichwaslatertakenprivate.

MRN:TheModelRocketNews-Theoldestcontinuouslypublishedrocketryperiodical.StartedbyVernEstesandhissmallcrewin1960,itisstillsenttoallofEstes'sactivemailordercustomers.Somewhatsophomoricinstyle,itcontains

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agreatdealofpracticalinformation,especiallyforbeginners.Ithassurvivedabewilderingarrayofchangesinformatovertheyears,butisstillpublishedthreeorfourtimesannually.

MSL:MeanSeaLevel.

Murphy’sLaw:TheguidingprincipleofRocketrypreparation:"Ifanythingcangowrong,itwill."

NAR:NationalAssociationofRocketry.AnationalhobbyorganizationpromotingmodelandhighpowerrocketryintheUnitedStates.TheNARpromotesrocketryrelatedsportflying,competitions,andeducation.

NARAM:NationalAssociationofRocketryAnnualMeet.TheNARnationalmodelrocketcompetitionchampionships,heldinAugustofeachyearatadifferentlocation.

NARCON:NationalAssociationofRocketryAnnualConvention.AnannualeventsanctionedbytheNARorientedtowardsnon-competitive(i.e.,sport)modelandhighpowerrocketry.Itincludesseminars,R&Dpresentationsandlotsofsportflying.Heldatadifferentlocationeachyear.ReplacedthePittsburghSpringConvention(PittCon)andMITCon,themodelrocketryconventionheldatMITinBoston,bothwhichceasedtobeheldinthelate70’s.Previously,theKentStateModelRocketryConvention(KentCon),areplacementforbothdiscontinuedconventionswasheldfrom1980-83.

NARTS:NationalAssociationofRocketryTechnicalServices.AserviceprovidedbytheNARforbothmembersandnon-members.NARTSstocksrocketplans,technicalreports,andotheritemsofinteresttorocketryenthusiasts.NARTSmaybereachedat:

NARTechnicalServices(NARTS)P.O.Box1482Saugus,MA01906CompuServeaccount:73320,1253

NeutralBurn:Whenthethrustofthemotorisrelativelyflatthroughouttheburn.(Seealso“Burn”,“ProgressiveBurn”,and“RegressiveBurn”)

Newton&Newton-second:Metricunitsusedtomeasurethrustandtotalimpulse(q.v.)respectively.Onepound=4.448newtons.

Nichrome:Analloyofnickelandchromiumdrawnintoawireofvaryinggaugestypicallyusedtoheatapyrogentoignitionwiththeapplicationofsufficientvoltageandamperage.Beforetheadventofpyrogen-typeigniters,barenichromewasusedfortheignitionofblackpowdermodelrocketmotors.

NitrousOxide:Gaseousoxidizerusedincurrenthybridrocketmotors.AlsocalledNOX.Thereareseveralgradesofnitrousavailable,withindustrialgrade,thetypeusedinnitrousinjectionsystemsforcarsbeingthemostcommonforusewithhybridmotorsystems.Ithasanadulterantaddedwhichrendersitunbreathable.

Nomex:Alightweight,fire-resistantNylonfiber,originallywovenintofireproofgarmentsforfirefighters,racecardriversandastronauts.Alsocommonlyusedinaircraftupholstery.InhobbyrocketryNomexisusedassheathsandbagstoprotectelasticshockcordsandparachutes.(See“DeploymentBag”)

NOS:Acronymfor“NewOldStock.”OftenusedtodescribeoldblackpowderMRorHPcompositemotorsstillavailableforsaleanduse.Itisn’tunusualtosee20+year-oldcompositemotorsstillbeingflownatResearchlaunches.NottobeconfusedwithNOX.NOSisalsotheshortenednameofNitrousOxideSystems,amanufacturerofnitrousoxidegasinjectionsystemsforracecars.Nose:Theforwardendofarocket.Thetapering(pointy)partoftherocketisoftenreferredtoasa"nosecone,"eventhoughtheshapeisrarelyconical.

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Nozzle:Theportionoftherocketmotorwhichacceleratestheexhaustgasestosupersonicvelocityatthenarrowestpartofthenozzle(thethroat)thenexpandsthemtogreatervelocityintheexitcone.Theseareusuallymadefromgraphiteorphenolic.

NSL:NationalSportLaunch.Anannual,nationalhigh-powersportlaunchsanctionedbytheNAR.ItwasoriginallyheldinFebruaryofeachyearsothatitismidwaybetweenNARAMnationalmeets,butthatlimiteditsouthernandwesternstates.NowitisheldovertheMemorialDayweekend.StartedasaNARalternativetoTripoli’sLDRSlaunch.

NFPA:NationalFireProtectionAssociation.Aprivatefor-profitorganizationresponsibleforcraftingrulesandregulationsdealingwithfiresafetyissues,whicharebeyondtheexpertiseoflocalagencies.TheNFPAisNOTagovernmentagencyandhasnoenforcementpowerofitsown.Itgathersexpertsinvariousfieldstowritesafetyregulationsforadoptionbylocalfireagencies(atthediscretionoftheFireMarshal).ThecurrentNARModelRocketSportingCodewasdevelopedbytheNARandNFPA.BoththeNARandTripoliaremembersoftheNFPA.

NFPA1122:ThecurrentNFPAregulationdefiningModelRocketry.Thisdocumentdefinesamodelrocketashavinglessthan1,500gramstotallaunchweight,containinglessthan125gramsoffuel(nomorethan62.5gramsinanyonemotor),andnomorethan160NStotalimpulseinallmotors(noindividualmotorhavingmorethan80NSoftotalimpulse).

NFPA1127:TheNFPAregulationdefiningHighPowerRocketry.Thedraftprovisionsof1127(notyetratified)definesHPRasfollows:Highpowerrocketshavenototalweightlimits,butdohaveasinglemotorlimitofnomorethanOpower(40,960NStotalimpulse)andhaveatotallimitationof81,920NStotalimpulse.

NXRL:TheNationalExperimentalRocketLaunch.Atermrarelyused.(See“BALLS”and“Fireballs”)

O-Ring:Aroundrubbergasketusedtocontaincombustiongassesinsolidrocketmotors,orliquidnitrousoxideinhybridmotors.

OctoberSky:AmovieaboutagroupofboysinacoaltowninWestVirginiawhobuildtheirownrockets.OctoberSkyisresponsibleformuchnewinterestinthehobby.Themoviewasbasedonthebook“RocketBoys”byHomerHickam,Jr.ThenameforafalllaunchformerlyheldbytheErieRocketGroup(ERG).

Oddrocs:Arocketnotshapedorconfiguredlikeatraditionalrocket.Thesecanincludepyramids,spools,saucers,oranythingelsethatnormallydoesn’tfly.

Ogive:Ashapedefinedbytheintersectionoftwocircles.Itisnotthesameasaparabola(q.v.).Bothogivesandparabolasproducelowdragsub-sonicnoseshapes.Theycanbetoldapartsinceaparabolaalwayshasaroundednosewhileanogivecomestoapoint.

OOP(OutOfProduction):Arocketkitorotherrocketryproductnolongercurrentlymade,butmanytimesrememberedfondlyfromthepast.ManydiscontinuedEstesandCenturirocketkitsarehighlyprizedbyBAR’sandhavehighcollectorvalue.

Opacifier:Anpropellantadditive,usuallylampblackoraluminum,whichmakesthepropellantopaqueinordertolimitexcessiveinfraredpropellantpreheating.Atranslucentpropellantwilltransmitandabsorbinfraredlightenergyfromthecombustionchamber,heatingtheremainingunburnedpropellant,whichcancauseanincreaseoftheburnrate. Manyearlycompositemotorshadclearpropellant(nometals)andtranslucentfiberglasscases,whichallowedyoutoseethemotorburnonstatictests.

OpenRocket:Afreewarecomputerprogramthatallowsyoutodesignanysizerocket,andthensimulateitsflighttoseehowhigh,andhowfastitwillfly.Evenbeforeyoustartbuildingyourcreation,you'llfindoutifitisstableandsafetolaunch.

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OptimumMass:ForanygivenmotorandDragFormFactor(q.v.)theliftoffmassforwhicharocketwillreachmaximumaltitudeindenseatmosphere.Atfirstthismightseemtobejustthelowestpossiblemass,butthereisatwoedgednaturetomasscoveringbothpoweredflightandcoasting.Lowermasswillgivehigherburnoutvelocity,butwilldissipateitsmomentumtodragfaster.Conversely,aheavierrocketwillhavemoremomentumatburnouttocoastfarther,buttoomuchmasswillholddownbothburnoutaltitudeandvelocity.Hence,thereisa"knee"ontheliftoffmassvs.altitudegraph.

OverStabie:Rocketswithastaticmarginovertwocalibersareconsidered'overstable'.Theserocketswilltendtoweathercockbadlyandmayoscillateorevenbecomeunstable.Careshouldbegiventothethrust-to-weightratio,launchrodvelocity,andwindconditions.

Oxidizer:Asubstance,whichprovidesoxygentoacombustionprocess,aidinginthespeedandefficiencyofcombustion.Theadditionofanoxidizertothechemicalprocessofcombustioncancauseafuelthatwouldbarelyburnundernormalatmosphericconditionstoburnsoenthusiasticallythatitcanbeusedasarocketpropellant.

PacificRocketSociety(PRS):Anexperimentalrocketorganizationwhichexperimentswithamateurrocketsbothsolidandliquidfueled,althoughmostlythelatter.Itisaveryoldorganizationbyhobbystandardswithrootsdatingbacktothe'50sthuspredatinghobbyrocketryinitscurrentform.TheylaunchintheMojaveDesertfromfacilitiesleasedfromtheReactionResearchSociety(q.v.).Theirmailingaddressis:

PacificRocketSociety1825OxnardBlvd.,Ste.24Oxnard,California93030

PadManager:Personresponsibleforassigningpadsandcontrollingthelaunchpadarea.Helpsrocketflyerssetuppadsandrocketsforflight.

Parabola:Ashapeproducedbytheformulay=x^2.Usedtoproducelowdragnosecones.(Seealso:"Ogive")

Parachute('chute):Themostcommonrocketrecoverysystemandtheonlyoneusedwithlargerrockets.Modelrocketoftenuseflatplastic"parasheets"whichareattachedtotherocketwithtapeandthread.Largerrocketsusetrueparachutesmadeofrip-stopnylonorsilkbecauseofthesizeandweightoftherocketsbeingrecovered.

ParachuteProtector:Alsocalleda“recoveryblanket”or“flameresistantblanket”.Apieceoffireproofcloth,usuallyNomex,usedtoprotecttherecoverydevicefromdamagecausedbythehotgassesoftheejectioncharge.Inlowandmid-powerrockets,thetraditionalEstes“flameproofrecoverywadding”(actuallytoilettissuesoakedinboricacidtomakeitfireproof)or“DogBarf”isused.

Payload:Anythingcarriedaloftbytherocketthatisnotpartoftherocketitself.Commonpayloadsincludealtimeters,computers,cameras,andradiotransmitters.TheSafetyCodespecificallyprohibitsthelaunchingoflivepayloads.

PBAN:PolybutadieneAcrylicAcidAcrylonitrileprepolymer;anotherbinderusedinAPCP.(See“Binder”)

PinkBookLawyer:AnyNARmemberwhouseshisownmanytimeslooseinterpretationoftheAssociationscompetitionrules(calledThePinkBook)toallowhisquestionableflighttoberuledqualified.

Phenolic:Aheat-resistantplasticmostfamiliarasthematerialfromwhichplasticashtraysaremade.Whenmixedwithcarbonblack,itisusedtomakecasingsforcompositepropellantrocketmotors.Severalmanufacturers,suchasPublicMissilesalsosellphenolicairframetubes.

PilotChute:Asmallparachuteattachedtotheapexofalargemainparachute,andsoorientedthatitemergesfromtheairframefirst.Airdragfromtheinflatingpilotchuteassiststhemainchutetoexittheairframe,pullingitoutapex-firstsothatitislesslikelytotangle.Nottobeconfusedwith“DrogueParachute”

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Plasmajet:AhighpowerrocketmotorcompanyfoundedbyRandySobszakandJohnKrell.Testedandsold29mmcompositemotorstolocalrocketeersatLucerne,CAlaunchesfromthelate70’stoearly80’s.HadmotorscertifiedbyTRAinearly90’sbutceasedproductionbecauseofseveremanufacturingandshippingrestrictions.OthermotorcompaniesputoutofbusinessforthesamereasonsatthistimewereSynerjet/R3,PropulsionIndustries,EnergonandRocketflight.PlasmajetmotorsstilloccasionallyshowupatResearchlaunches.

Plasticizer:Achemicaladditive,whichmakesthecompositepropellantmixturemorefluidduringthemixingprocessthusallowingamorehomogenousdistributionofthechemicalsinthebinder,inadditiontomakingiteasiertomixandreducingmixtimes.

PMC:PlasticModelConversion.Thetermusedtodescribeaplastic,staticmodelofsometype(typicallyanaircraft,rocketorspaceship)thathasbeenconvertedtoflyasamodelorhighpowerrocket.ThistermisalsousedasanabbreviationforanNAR-sanctionedcompetitionusingconvertedmodels.

PowerShred:(See“Shred”)

Prang:Termdescribingafailuremodewherebyarocketcomesdownaerodynamicallystable,inotherwords,'streamlinesin'.Thisisalmostalwayscausedbysomesortofrecoverysystemfailure,usuallytheresultofatoo-tightnosecone,too-tightlypackedparachuteoratoo-loosemotorthatejectsouttheback.Multistagemodelswithupperstageignitionfailuresalsoresultinaprang.

APrangthatoccurswhilethemotorisstillburning(e.g.amarginallyunstablerocketthatperformsonelargehalfloop)iscalleda'PowerPrang'.

Origin:Ifyouinsistonitbeinganacronym,thepostwarmilitarysoundingrocketprogramhadaquasi-officialfailuremodecategory"ParachuteRecoveryApparatusNoGood."However,likeCATO(q.v.),thisisanother"PostHoc"definition.ThetermwasinwidespreaduseduringWWIIinaviationcirclestodescribeaircraftcrashes,especiallyexperimentalormilitaryones.PriortouseintheU.S.,itwaspopularinBritainsinceatleastthe'30swheretheexpression"PranghisKite"wasequivalenttoour"Augerin"or"BuytheFarm."

ProDyne-PropulsionDynamics:Amanufacturerofearlyhighpowercompositerocketmotorsinthe60’sand70’s.OperatedbyJohnRahkonnen,arealrocketscientistwhoworkedatThiokol.ProDyneproducedtheCycloneandHurricanelinesofmotors,butonlyhadonecompositemotoreverTRAcertified.OneofhisearlymotorsisondisplayattheNationalAirandSpaceMuseum.

ProgressiveBurn:Whenthethrustofthemotorincreasesthroughouttheburn.Typicalofmonolithic(onepiece)propellantgrains.(Seealso“Burn”,“NeutralBurn”,and“RegressiveBurn”)

Prototype:Aninitial,developmentdesignusedtotestoutprinciplesandconceptsbutneverintendedtobeafinishedorproductiondesign.Inscalemodeling,theoriginal"real"rocketafterwhichthemodelispatterned.

Origin(inthemodelingsense):Thetermcomesfrommodelrailroadingwherehobbyistsmodelsectionsofentirerailroadsincludingwholetowns,mountains,lakes,etc.inadditiontotheengines,carsandtracks.(Seealso:"ScaleData"and"ScalePlan")

PTFE:Tetrafluoroethylene;(See“Teflon”)

Pyramid:Arocketshapedlikea3or4-sidedpyramid.Highpowerversionsofthisareoftencalled“flyingpyramidsofdeath”becauseoftheirtendencytoflyintothegroundunderpower.TheTripoliRocketryAssociationnolongerallowsthese,oranyother“oddrocs”suchasspools,tobeusedforLevel3Certificationattempts.

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Pyrodex:AblackpowdersubstitutemadebyHodgton;intendedformuzzleloadingfirearms,itisactuallyconsideredapropellantanddoesnotrequireaLEUPforpurchaseorstorage.NotrecommendedforuseinejectionchargesbutsolidPyrodexpelletsarebeingusedaspropellantgrainignitersinCTImotors.

Pyrogen:Liquidsolutionthatisusedtomakeignitersorahighlyflammablesubstanceusedtoigniterocketmotors;typicallyaliquidthatignitersaredippedin.OnecommoncommercialpyrogenisMagnalitebyRocketflite.

RailGuides(orrailbuttons):Small,round“H”shapedbuttonsmadeofnylonorphenolicattachedtotherocketairframewithscrewsandusedinconjunctionwithalaunchrailtoguidetherocketduringitsinitialflight.Usedinsteadof“LaunchLugs”,theyhavelessaerodynamicdrag.

RangeBox:Aboxusedtocarryeverythingthatyouneedforflyingrocketsontherocketlaunchrange.

Rangehead:Thepartofalaunchsitewheretherocketlaunchpadsarelocated.

RASP:TheRocketAltitudeSimulationProgram.OriginallywrittenbyG.HarryStineinBASICinthelate'70s(andincludedasanappendixinthelatereditionsoftheHandbook),itperformsasimulationofrocketflightusingsmalltimeintervalapproximations.TheoriginalwasrelativelyprimitiveassumingconstantCd,verticalflightandothersimplifications.Therehavebeenseveralrewritesinto"C"andotherlanguagestobothbroadenitsappealandincreaseitssophistication.

ReactionResearchSociety(RRS):Oneoftheoldestamateurrocketryorganizations.Foundedin1943,membersofthisSouthernCaliforniagroupinvestigateallformsofreactionbasedvehicles:solid/liquid/hybrid.Theircurrentveryambitiousplansincludeorbitingthefirst*completely*amateursatellitewithavehiclebasedonthe"10K"(10,000lbthrust)LOX/Kerosenemotornowindevelopment.

TheyhavethedecidedadvantageofowningtheirMojaveDesertlaunchsite,whichisadjacenttoEdwardsAirForceBaseandthusprotectedbytheir"infinite"restrictedairspace.TheyleasetheuseoftheirlaunchfacilitiestothePacificRocketSociety(q.v.)andwelcomeHPRflierstocomedownandflyanythingasbigandhighastheywantaslongasit'sprearrangedandyouplaybytheirsafetyprocedures.

FormoreinfothereisamessageonthePacificEnergyvoicemailsystemwhichcanbeaccessedafter6PM(Pacifictime)onweekdaysandanytimeonweekends(213)725-1139,ex777.PRcoordinator:NielsAnderson.

Mailingaddressis:ReactionResearchSocietyP.O.Box90306WorldWayPostalCenterLosAngeles,California90009

Recovery:Rocketsmustberecoverysafely.Gettingyourrocketbackinoncepieceisimportantaspartofasuccessfulflight(nottomentionthatitallowsyoutoflyagain).Themostcommonrecoverysystemsareparachutesandstreamersalthoughmanyothershavebeendevised,suchasrocketglidersandhelicopterrecovery.

RedBaron:Aboostglider,whichhastangledwiththestreamerorparachuteoftheboosterpod.Theentiremodeltendstonosediveintotheground,likeaWWIairplane,whichhasjustbeenshotdown.

Reef:Aseriesoftechniquesusedtogathertheshroudlinesofaparachutetogethertopreventitfromfullyopening.Thisisusuallydoneonrocketsthatreachextremealtitudesorlaunchedonwindydays,whichneedhighersinkratestohelpthemlandnearthelauncher.Thereisalsoa"travelingreef"techniqueofplacingasodastrawormetalwasherontheshroudlinesandslidingitallthewayuptothechutecanopyduringprep.Atdeployment,theparachuteispreventedfromopeninguntilthechuteisfullydeployedandtherocketstabilizedbeneathit.Thestraw/washerthenslidesdowntheshroudsallowingthecanopytoopengradually.Onmannedparachutes,thisiscalleda“slider”.Thisis

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usedmostlyonlargerockets,whichmighthaveveryhighspeedorhighaltituderecoverydeploymentsinceitallowstherockettoslowanddropconsiderablybeforechuteopening.

RegressiveBurn:Whenthethrustofthemotordiminishedthroughouttheburn.(Seealso“Burn”,“NeutralBurn”,“ProgressiveBurn”)

Re-Kitted:A(painfully)humoroustermthatreferstoanysituationwherearocketgoestopiecessuchasaprang(q.v.)oraCATO(q.v.).ThoughttohaveoriginatedatLDRSXIII.Typicalusage:"ThatMmotorsurere-kittedmyBlackBrant!"

Relayer-RelayLauncher:Alaunchcontrollerthatcontrolselectricalcurrenttotheigniterthroughanelectricalrelay.Thisarrangementallowsthepowersource,usuallya12vautomotivebattery,tobeplacedclosetotherangehead,reducingthevoltageandcurrentlossthroughlongwires.

Reload:Acompletekitcontainingpropellantgrains,nozzle,linertube,o-rings,delay/smokeelementandablackpowderejectionchargeusedbytherocketeertoloadacommercialrocketmotorcase.

ReloadableMotor:Arocketmotorwithareusablemetalcase,endclosuresandsometimesagraphitenozzle.Therocketeerloadspropellant“reloads”intothecasehimselfinsteadofhavingthemotormanufacturerdoitasinthecaseofsingle-useorexpendablemotors.Supposedlylessexpensivethananequivalentsizedexpendablemotor.ExamplesaretheAerotechRMSSystemortheKosdonTRMSystem.

ResearchorResearchRocketry:Anicheofhighpowerrocketryinwhichrocketeersmix,castand“burn”theirownhomemadeAPCPorsugarpropellant,inexistingcommercialbutsometimesinhomemadereloadablecasings,ratherthanusingcommerciallymademotors.Canalsoincludehybrid,butnotblackpowdermotors.Formerlycalled“EX”(pronouncedE-X)orEXperimentalrocketry.

ReynoldsNumber(Rn):Adimensionlessnumberusedbyfluidflowengineerstocharacterizethewayafluid(gasorliquid)willbehavewhenpassingoverasolidsurface.Thenumbercombinesthefluid'sdensity,viscosityandvelocitywiththelengthit'straveledalongthesurface.Nomatterwhatthefluidisorwhatsizethesurface,theflowconditions(laminar,turbulent,detached,etc.)shouldbethesameatthesameRn.DiscoveredbyOsborneReynoldsinthe19thCenturywhilestudyingtheflowofwaterinpipesandchannels,ithasprovenmostusefultoaerodynamicengineersandnavalarchitectsinscalingupwind/watertunneltestresultstofullsize.

R/G:Rocketglider:Aglider,whichisboostedtoaltitudebyarocket.Theentiremodelglidesdowntogether.Nopartofthemodelseparates,asinaboostglider.Technically,anR/GisaparticularformofB/G.

Rip-StopNylon:Acommonparachutematerial;itisdistinguishedbyafinepatternofboxes(barelynoticeable)thataredesignedtokeepfabricfromtearing

RMSTM:ReloadableMotorSystem.ThetrademarkednameoftheAeroTech/ISPreloadablemotors.Oftenused(incorrectly)asagenericnameforallreloadabletechnology.

RoadFlare:Areloadablerocketmotorthathasblownoutoneofitsend-closuresandisstillburningpropellantbutproducingnomeasureablethrust.Cancausegreatdamagetotherocketifitistheforwardclosureandmotorstaysintheairframe.

RDC-RocketDevelopmentCorp:AmodelrocketcompanyoperatedbyIrvingWaitfamousforofferingthefirsttruecompositepropellantrocketmotortohobbyrocketeersinthe‘60’s.The“Enerjet8”wasa40s-secEmotorwith8pounds(orabout34n-sec)ofthrust.Itusedafuseforanejectiondelay,whichtherocketeertrimmedforthedesireddelaytime.RDCsoldthecompositemotortechnologytoCenturiEngineeringCompanyandtheyintroducedthe“Enerjet”lineofE,FandGrocketmotorsandhighpowerkits.RDCthenshutdowntheirmodelrocketdivision,althoughtheycontinuedtoproducemotorsforprofessionalandmilitarycontractsuntilabout1990.Inthemid-80’sRDC

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producedthe“Whirlwind”compositeEmotorforNorthCoastRocketry,whichwasthefirstsmokycompositemotoravailableforsale.

RocketandSpaceFoundation:AnorganizationinHollandthatsupportsbothmodelandamateurrocketryandamateurastronomy.TheSecretaryisMarcelVerhoef,DelftUniversityofTechnology,whocanbereachedat:

RocketandSpaceFoundationP.O.Box3143350AHPapendrechtTheNetherlandsInternet:[email protected]

RockSim:Acomputerprogramthatallowsyoutodesignanysizerocket,andthensimulateitsflighttoseehowhigh,andhowfastitwillfly.Evenbeforeyoustartbuildingyourcreation,you'llfindoutifitisstableandsafetolaunch.(Launch)RodWhip:Theflexingofalaunchrodduringrocketlift-off,whichmaycausetherockettoheadoffatanundesirableangle.

RomanCandle:Afailureofthemotorrestraint(thrustringorenginehook)wheretherocketstaysonthepadwhilethemotorfliesoutofthebody(usuallypushingthenoseconeandrecoverysystemaheadofit).SometimesmistakenforaCATO(q.v.).

RSO:TheRangeSafetyOfficer,theindividualresponsibleforensuringthatrocketspresentedforlaunchareproperlyconstructed,preppedandbalancedforstability.

SafetyNazi:Apersonoverlyconcernedwithsafetytothepointofdetractingfromtheenjoymentofthehobby.SomeonewhofeelstheSafetyCodedoesn'tgo"farenough"inpreventinginjuriesdespitethehobby'soutstandingsafetyrecord.

Sears-Haack:Aseriesofnoseconesdesignedandusedformaximumaerodynamicefficiencyonveryhigh-speedrockets.ThemostcommonlyencounteredconeinthisseriesisaVonKarmoncone.

St.LouisArch:ThetrajectoryofaPrang(q.v)whenviewedfromadistance.Namedforthefamousmonumentwhoseshapeitmimics.

ScaleData:Drawings,photos,dimensions,anddescriptionsofaprototype(q.v.)rocketusedinmakingamodelofthatrocket.

ScalePlan:Instructions,diagrams,andpatternsforbuildingamodelofaprototype(q.v.)rocket.Ascaleplanspecifiesdetailsofamodelthatmaynothaveanythingtodowiththeprototype,includingmaterials,scalefactor,internalconstruction,andcompromisesinaccuracynecessaryforsafeflightoreaseofconstruction.(Seealso"ScaleData")

SectionalDensity:Aprojectile'smassdividedbythesquareofitsdiameter.Usedasameasureofaroundprojectile'sabilitytocoast.(Seealso"BallisticCoefficient")

Separation(Sep):Whentherecoverysystemcomesouttooearlyortoolateduringtherocketflightand/orthevehicleisstillmovingtoofast,therecoverysystemcantakehigherloadsthandesignedfor.Iftheshockcordbreaks,thetwopartsbecomedetachedandyouhaveaseparation.Alsoifthenoseconeaccidentlydetachesfromtherocketatejection.

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ShearPin:Apinorpinsthatretainanoseconeorotherairframesectiontoavoiddragseparationorprematuremainparachutedeploymentcausedbytheshockofanapogeeejectioncharge.Theyareshearedoffbytheforceoftheejectioncharge;oftennylonscrewsareused.

ShockCord:Alengthofrubber,elastic,bungee,nylonorKevlarstraportube,whichprovidesshockabsorptionfortherocketcomponentsatthepointofflightwheretheejectionchargefiresandtheparachuteopens.

ShockCordMount:Theattachmentpointforashockcord.

Shred:Amodel,whichhaslostoneormorefinsduetoaeroloadsand/oraccelerationortheconditioninwhicharocket'sairframefailsduringlaunch.Thisiscausedwhentheforceappliedbyarocketmotorexceedsthetensilestrengthoftherocketairframe.Theeffectofashredissimilartoanexplosion.Alsocalleda“PowerShred”.Canbeusedaseitheraverbornoun.(Seealso"Strip")

ShroudLine(Parachute):Linesorstrings,whichpulldownontheedgesofaparachute.Theshroudscometogetherattheirbottomendstoprovideapointofattachmentbetweentheparachuteandtherocket.

SilverStreakTM:Alargeblackpowdermotor(F&Gclass),oncemadebyRocketflite,Inc.,whichproducedalargeplumeofsparklingexhaustwhenignited.

SingleBasePropellant:Asolidpropellantbasedonasinglemonopropellant.Inpractice,usuallynitrocelluloseinamixturewithstabilizersandplasticizers.Singlebasepropellantsareusedassmokelesspowdersinammunition.Inrockets,suchpropellantshavebeenlargelyreplacedbycomposites.Singlebasepropellantsarenotusedinhobbyrocketry.Seealso"CompositePropellant"

SinkRate:Therateofverticaldropduringtherecoveryphaseofaflight,infeetormeterspersecond.Sinkrateusedtospecifyparachuteorstreamersizeforarocket.Sliver:Remnantofpropellantorfuelincompositemotorsasaconsequenceofinitialgeometry.Thelast10%ofamotorburnisusuallyconsidered“slivering”andnotincludedinthetotalimpulseofthemotor.SkidMark:AmotorbyCTI/AnimalMotorWorksthatusesabinderrichpropellantwithmetallictitaniumtoproducealotofflame,blacksmokeandsparks.Alsousedasagenerictermforanysparkymotor.VariationbyothermanufacturersaretheFirestorm,MetalStorm,DarkMatter,BlackLightning,Spitfireandothers.SnapRing:Aspringmetalringthatisintendedtosnapintoagrooveeitherinsideoroutsideapipeorshaft;innersnapringsareusedtoretainnozzlesandforwardclosuresinKosdon/AMW/Gorilla-stylereloadablemotors,andanouterringisusuallyusedasathrustring;requiresaspecialsetofplierstoinstall/remove.Sorbitol:Anartificialsweetener,verysimilarinappearanceandwithsimilarphysicalcharacteristicstobothsucroseanddextrosesugarsusedin“sugarmotors”.

SolarIgniterTM:EstesIndustriesbrandofIgniter.Madefromtwowireconductorswithapieceofnichromewireconnectingthematoneend.Thenichromewiretipoftheigniterisdippedinapyrotechniccompound,whichflarestoignitetherocketmotor.

SolidsLoading:Theproportionofsolidsinapropellantformulation;increasingthesolidsloadinghasseveraleffects,includingincreasingtheIsp.

SpaceCAD:Acomputerprogramthatmakesiteasyforyoutodesignrockets.Youcanviewthemin2Dand3D,youcanzoomintoyourdesignandyoucangetseehowyourrocketwilllooklike-beforeyouevenstartbuildingit.Specificimpulse(Isp):Referstothepowerperunitofpropellant.Forinstance,whenamotormanufacturersaysthat

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theirpropellantdeliversnearlythreetimesthepoweroftheequivalentamountofblackpowderpropellant,they'rereferringtothespecificimpulse.

SpillHole:Anopeningcutinthetopofaparachutetoincreasethesinkrate(thusdecreasedriftdistance)andaidrecoveryonwindydays.

SportRocket:Amodelrocketdesignedandbuiltwithnospecificpurposeinmindotherthantoflyit.Mosthighpowerrocketsaresportrockets.

SportRocketry:ThejournaloftheNationalAssociationofRocketry.Previouslyknownas“AmericanSpacemodeling”(q.v.).Publishedsixtimesperyear.DistributedaspartofmembershiptoallactiveNARmembersbutalsoavailableofftherackinlargerhobbyshops.IthasnoconnectionwiththeCompuServediscussiongroupofthesamename.

Squib:Asmallexplosivedeviceusedtodetonatelargerexplosivecharges.Whilethetermissometimesusedtodescribeignitersusedinhobbyrocketry,especiallyHPRigniterssuchaselectricmatches(q.v.),truesquibsarealmost*never*usedasigniterssincetheirpurposeistosetupadetonationpressurewavetosetoffpressuresensitiveexplosives(e.g.plasticexplosive),whileanignitermuststarta(relatively)lowspeedflamefrontsothatthemotorburns,ratherthanexplodes.

Stability:Hobbyrocketsalmostalwaysdependonfinsandbalancetoguidetherocketinastraightlineduringflight.Aparticularrocketisstableonaparticularmotorifitwilllaunchandflyinastraightline.

StaticTest:Firingarocketmotorinarestrained,protectedareaforpurposesofrecordingchamberpressure,thrust,walltemperature,plumecharacteristics,burningduration,etc.

StrandBurner:Adevicethatmeasurestheburnrateofanenergeticcompositioninanelevatedpressureenvironment.AlsocalledaCrawfordBomb.

Streamer:Arecoverysystemforthesmallestofmodelrockets.Streamersareflatplastic,crepepaperorMylarbands,whichareattachedtotherocket,andflapastherocketcomesdown,slowingthedescent.Sometimesusedtoslowthedecentofdualdeployrocketsafterapogeedeployment.

StringTest:Asimplemethodfortestingthestabilityofamodelrocket.Astringapproximately10ftlongistiedtothecenterofgravityofafullypreppedrocketwhichisthentwirledoverheadinacircle.Ifthenosepointsinthedirectionofthespinandtherocketdoesnotwobblethenitisverylikelyastabledesign.Notapracticalmethodtousewithlargehighpowerrockets.

Strip,Stripped:Termsdescribingaparachutethathashadoneormoreshroudlinesbreakorpullfreeduetoopeningshock.Usualcauseisrecoverydeploymentattoohighaspeed,butcanalsobeduetoage(ofthetapedisksonaplasticchute)orpoorconstruction.Canbeusedasaverbornoun.(Seealso"Shred"and"Reef")

StufferTube:Asmall-diametertube-commonlyanextensionofthemotortube-whichisusedinlarge-diameterrocketairframestoductdeploymentchargegasestotherecoverysystemstoragearea.Thisreducestheinternalarea,whichmustbepressurizedbythedeploymentcharge.

SU:SingleUse(motor)Aone-timeusedisposablemotor,whichcannotbere-used.Beforereloadablemotorsbecamethestandardforhigh-power,allrocketmotorsweresingleuse.

SuctionLock:TheMotherofallBaseDrag.(See"BernoulliLock")

SugarMotor:Anexperimentalmotorthatusesamixtureofpotassiumnitrateandsugar(typ.sucrose,dextroseorsorbitol)asapropellant;alsocalled“candyfuel”ora“candymotor”

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Surfactant:Compoundsthatlowerthesurfacetension(orinterfacialtension)betweenaliquidandasolid.Incompositepropellantproduction,itactsasawettingagenttobetterallowthebindertocoattheAPparticles.AnexampleisTritonX-100surfactant.

TailOff:Referstogradualreductioninpressureandthrustatendofburningofarocketmotor.

TARC:TeamAmericaRocketryChallenge.AnaerospacedesignandengineeringeventforteamsofUSsecondaryschoolstudents(7ththrough12thgrades)runbytheNARandtheAerospaceIndustriesAssociation(AIA).ThegoalofTARCistomotivatestudentstopursueaerospaceasanexcitingcareerfield,anditisco-sponsoredbytheAmericanAssociationofPhysicsTeachers,EstesIndustries,theDepartmentofDefense,andNASA.Thetop100teamsfromamongallthosewhohaveenteredwillmeetinafinalfly-offcompetitioninGreatMeadow,ThePlains,VA tocompetefor$100,000inprizesandafreetriptoeithertheParisortheFarnboroughairshowinEurope.

Teflon:ThepolymerPTFE,anextremelyslipperymaterialthatisinerttoalmosteveryknownchemical;rocketusesincludelubricants,releasefilms,andreusablerecoverywadding;patentedbyDuPont.

TestStand:Designedtorestrainamotorduringtestandpermitenoughmotiontoactuatealoadcell.(See“statictest”)

TerminalVelocity:Inthepoweredphase,thespeedwherethemotorthrustequalsthecombinedforcesofgravityandaerodrag.Theoretically,therocketwouldcontinueascendingataconstantspeed(i.e.noacceleration)withtheseforcesinbalance.Thisdoesn'tactuallyhappensincemotorthrustvarieswithtimeandaerodragwithaltitude.Asecondmeaningis,whendescending,whereaerodragbalancestheweightofthedescendingmodel.Ifundera'chuteorotherhighdragrecoveryaid,thisisquiteslow.Ifincoresample(q.v.)modethisspeedcanbeseveralhundredfeet/sec.(Seealso"HyperterminalVelocity")

Thermalite:Amaterial,originallyusedtodetonateplasticexplosive,whichburnsatacontrolledrateandhightemperature.Usedwithrocketmotorsasanignitionenhancement.Itcanbeignitedbyelectric(nichrome)means,electricmatches,flashbulbsortheexhaustofapreviouslystartedmotor.Itcomesinthreeburningspeedscolor-codedaspink(slow),green(medium)andblack(fast).Foraroughorderofmagnitude,slowisaround1in/secandfastis5in/secinfreeair,butthiscanbeaffectedbytemperature,humidity,pressureandwhetherornotthefuseissheathedinatube.

Thrust:Thisisameasureofinstantaneousforce(inNewtonsorpoundofforce).The"averagethrust"ofamotoristheaverageamountitpushesontherocketduringit'sentireburnphase.Notethatthemotorgenerallyproducesdifferentamountsofthrustasitburnsandagraphofthisiscalleda"thrustcurve.”

ThrustCurve:Thepropulsiveforceofarocketmotorplottedagainsttime.(See“Thrust”)

ThrustCurve.Org:Awebsitethatcontainsspecificsincludingsize,weight,averagethrust,totalthrust,andthrustcurvesofcertifiedcommerciallyavailablerocketmotors.

ThruTheWall(TTW):AnHPRfinattachmenttechnique,whichprovidesmuchgreaterstrengththanthetypicalsurfacemountusedinmodelrocketry.TouseTTW,slotsarecutinthebodytubewherethefinsmountandthefinsarebuiltwithextendedtabsontherootedge,whichfitthroughtheseslots.InoneformofTTW,thetabsareshortandjustprovideasurfacetobuildupepoxyfilletsontheinsideaswellastheoutside.InastrongerversionofTTW,thetabsreachallthewaytothemotortubewheretheyaregluedformingaveryrigidboxstructure.ThrustCoefficient:Theamountamotorsthrustisaugmentedbynozzleeffects.Valuesusuallyrangefrom1.2to1.4.1.25isthevaluenormallyused.

TigerTailTM:AnignitersoldbyQuestAerospaceconsistingoftwoverythincopperfoilleadsseparatedbyandeventhinnerplasticinsulatorwiththepyrogeniccompoundatthetip.EssentiallyaminiCopperhead(q.v.),itsnamecomesfromtheorangeandblackstripedtapestripprovidedtoallowittobeusedwithordinaryalligatorclipignitionsystems.

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MeantforusewithQuestblackpowdermotors,theyarewidelyusedforignitingejectionchargesinrocketsfittedwithdualdeployrecoverysystems.

TimeDelay:(See"DelayTrain")

TotalImpulse:Thetotalthrustproducedbyarocketmotoracrossitsfullburntime.UsuallyexpressedinNewton-secondsorpound-seconds.

TripleBasePropellant:Asolidpropellantbasedonthreemonopropellantsandadditives.Inpractice,themonopropellantsareusuallynitroglycerin,nitrocellulose,andnitroguanidine.Inmilitaryrockets,suchpropellantshavebeenlargelyreplacedbycomposites.Triplebasepropellantsarenotusedinhobbyrocketry.(Seealso"CompositePropellant")

Tripoli(TRA):TripoliRocketryAssociation.Aconsumerrocketryorganizationfoundedtopromotetheinterestsofhighpowerandadvancedrocketryenthusiasts.

Tripolitan:“TheTripolitan...America'sHighPowerRocketryMagazine”ThebimonthlyjournaloftheTripoliRocketryAssociation,publisheduntilJuly/August1992.Itbecame“HPRMagazine”(q.v.)withtheSept/Oct1992issue).

TubeFins:Thecasewherethefinsaremadeofsectionsoftubingthataretangentiallyconnectedtotheairframe;6sectionsoftubing,thesamediameterastheairframe,willcompletelyencloseanairframe.TubeFinRocket:Arocketthatusesseveraltubesratherthanconventionalfinsforstability.TubeFinRocket-Arocketthatusesseveraltubesratherthanconventionalfinsforstability.Severalkitmanufacturerssellrocketsofthistype.

UnsymmetricalThrust:Aconditioninwhichthethrustofamotorormotorclusterisnotparalleltotheaxisoftherocket.Thisismostoftencausedbythefailureofpartofaclusterofmotorstoigniteoraprotuberanceextendingintotheexhauststreamofasinglemotor.

Upscale(ing):Thepracticeofbuildinglargeversionsofsmallermodelrockets.Popularamongstold-timehighpowerrocketeers.ManyofthefirsthighpowerrocketswereupscaledEstesandCenturimodelrocketkits.

USLI–NASA'sUniversityStudentLaunchInitiative:Acompetitionthatchallengesuniversity-levelstudentstodesign,buildandlaunchareusablerocketwithascientificorengineeringpayloadtoonemileabovegroundlevel.TheannuallauncheventishostedatBraggFarmsinToney,Alabama,andlaunchservicesareprovidedbytheNationalAssociationofRocketry.

VolumeLoading:Totalpercentageofmotorvolumethatispropellant.

VonKarmon:Anoseconeshape.VonKarmonisaspecialcaseoftheSears-Haackseriesofnoseconeshapes,usedonveryhigh-speedrockets.Itisthemostefficientvolumeperunitnosedrag.

VulcanSystems:AprofessionalrocketmotorcompanyrunbyScottDixon,nowlocatedinColoradoSprings.VulcanmanufacturedhobbyrocketmotorsforNorthCoastRocketryandthemselvesinthe80’sand90’s.Specializinginwhattheycalled“stumppullers”,thatis,highthrust,shortburnmotors.Oneoftheearlyproducersofsmokycompositepropellant.Vulcanmanufacturedthe“DarkStar”lineofrocketmotorsforNorthCoastRocketryandlater,EstesIndustries.VulcannolongermakesmotorsforHPR,insteadtheyconcentrateonprofessional,militaryandDARPAcontracts.Vulcan,throughasubsidiary,makestherocketmotorsthatdeployssmallairplaneparachuterecoverysafetysystems.VulcanmotorscanstillbeseenbeingflownatResearchlaunches.

Wadding:Anyflame-retardantmaterialusedtopreventthescorchingoftherecoverysystemduetotheheatoftheejectioncharge.Thematerialisplacedinthebodytubebetweentheengineandtherecoverysystem.(Seealso“DogBarf”and"FlameproofRecoveryWadding")

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Waiver:ThetermusedtodescribetheofficialpermissiongivenbytheFAAallowingrocketswithmorethan113gramsoffuelorweighingmorethan3.3poundstobeflownintoFAAcontrolledairspace.(Seealso"FAR101")

Weathercocking:Thetendencyofarockettoflyintothewinddirectionbecauseofwindloadingonthefinswhenitleavesthelaunchrodorrail,alteringtheflightpathfromvertical.Rocketswithlargelength/diameterratiosorwithlargefinsareespeciallysusceptible.

Web:Thethickestdepthofthepropellantthattheflamefrontwillburnthrough.InaBatesgrainmotorthatisthedistancefromtheoutsideedgeofthepropellantgraintotheoutsideofthecore.Itvariesforothercoregeometries.wRASP:WindowsRocketAltitudeSimulationProgram;apublicdomainprogramthatsimulatestheflightofarocketinonedimensionX-FormParachute:Aparachutethatisformedbyconnectingtogethertworectanglesofmaterial,forminga'X’pattern.

YABAR:YetAnotherBornAgainRocketeer.

Zipper(orZippering):orZipperMotorEffect:Adevastatingsideeffectofmountingtheshockcordtothemotormount(whichisoftendoneforstrengthortoanchorapistonejectionsystem).Ifstrongandthincordisused(e.g.Kevlar)andtherecoverysystemopensattoohighaspeedthenthelinecan"zip"openthebodytubeallthewaydowntothemotormount.Asufficientlystrongtopmountedshockcordcanpartiallyzipabodytubeifopenedatahighenoughspeed.


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Ye Olde Rocket Plans · 2008. 1. 7. · A few of the topics were: basic model rocketry, advanced model .rocketry and club formation. The groups encouraged each par- ticipant to relate

ALTITUDE PREDICTION CHARTS - Discount Rocketry › media › model_rocket...ounces without engines. An A8-3 engine is used to power the rocket. The rocket uses a BT-20 body tube. Assume

United Kingdom Rocketry Association Safety Code Version 4United Kingdom Rocketry Association Safety Code Page 2 of 25 ... 4.21 25th February 2004 5 Changed model and high power rocket

[Rocketry].[Water Bottle Rocket Handbook]

HPR Staging & Air Starting By Gary Stroick Complex Rocket Design Considerations

Richard Nakka's Experimental Rocketry Web Site · Richard Nakka's Experimental Rocketry Web Site Solid Rocket Motor Theory -- Propellant Grain Propellant Grain The propellant utilized

Jan-Feb 2003nar.org/pdf/HPR - V2 Dual Deploy Project - Sport Rocketry... · 2019-01-03 · * Nosecones & Other Rocket Supplies * Learn About Rocket Camps Summer 2003 CP Technologies

by Graham Platt by Leon Kemp - United Kingdom Rocketry ... · The rocket was nicknamed “Oranje Boven” which means Orange Above in Dutch, seems appropriate for an orange rocket

Biomark HPR and HPR Plus Reader User Manual

ARCAS Rocket Assembly Instructions - HARA Rocketry

ROCKET BASICS - engineering108.com · 2013. 1. 1. · ROCKET BASICS A Guide to Solid Propellant Rocketry For additional information about Thiokol Propulsion please contact: Thiokol

Rocketry 101 Available Sheet. Part of this area of focus includes building your own rocket

Sponsorship Packet - MASA Packet 2020-2021.pdfHelios, its first rocket with a composite airframe, and its largest rocket to date. 2003: MASA is founded as an amateur rocketry club

Rocketry Starter Kit€¦ · • Purchase an inexpensive, one-stage rocket kit to familiarize your team with rocket building & flying. Estes has a number of resources available for

International Rocket Competition - National Association of Rocketry

4-H ROCKETRY PROJECT - Prince Edward Island · 2014-01-03 · 4-H ROCKETRY PROJECT ... S Members will assemble a model rocket from a kit and launch it! ( Model rocket kits S Members