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Astronautics •• Introduction Introduction toto spacespace systemssystems conceptsconcepts •Space•Space environmentenvironment •• Orbital Orbital mechanicsmechanics •• Attitude Attitude dynamicsdynamics andand controlcontrol •• Propulsion Propulsion andand launchlaunch vehiclesvehicles •• Space Space lawlaw andand policypolicy •Space•Space industryindustry Sample Space Applications CommunicationsCommunications Navigation Navigation Relay Relay WeatherWeather Surveillance Surveillance Science Science MaterialsMaterials processingprocessing Search Search && rescuerescue AstronomyAstronomy Weapons Weapons Tourism Tourism SpaceSpace ExplorationExploration Solar Solar PowerPower TransportationTransportation Colonization Colonization Mapping Mapping Basic Elements of Space Missions •Subject• Subject- - the the “thing”“thing” which which interactsinteracts withwith oror isis sensedsensed byby thethe payloadpayload •Space• Space segmentsegment -- spacecraft spacecraft comprisedcomprised ofof payloadpayloadand and spacecraftspacecraft busbus •Launch• Launch segmentsegment- - launch launch facilities,facilities, launchlaunch vehicle,vehicle, upperupper stage.stage. ConstrainsConstrains spacecraftspacecraft size.size. •• Orbit/constellation Orbit/constellation -- spacecraft’s spacecraft’s trajectorytrajectory oror pathpath throughthrough spacespace •C•C33 ArchitectureArchitecture- - command, command, controlcontrol andand communicationscommunications •Ground• Ground segmentsegment- - fixed fixed andand mobilemobile groundground stationsstations necessarynecessary forfor TT&CTT&C •• Mission Mission operationsoperations- - the the people,people, policiespolicies andand proceduresprocedures occupyingoccupying thethe groundground (and(and possiblypossibly space)space) segmentssegments Bus Payload Mission Space segment Operations Orbit and Command, Control and Constellation Communications Architecture Ground Segment Reference:Reference: LarsonLarson Launch Segment && Wertz,Wertz, SpaceSpace MissionMission AnalysisAnalysis Subject andand DesignDesign Payload and Bus Subsystems Spacecraft BasicBasic requirementsrequirements •• Payload Payload mustmust bebe Payload Bus pointedpointed •• Payload Payload mustmust bebe Sensors operableoperable Cameras Power TT&C Antennas Solar arrays Power switching •• Data Data mustmust bebe Radar Batteries Encoder/decoder transmittedtransmitted toto usersusers PMAD Processors •• Orbit Orbit mustmust bebe ADCS Propulsion maintainedmaintained Sensors Orbit injection Actuators Stationkeeping •• Payload Payload mustmust bebe Processors Attitude control “held“held together”together” • Energy must be Thermal Control Structure • Energy must be Coatings Primary structure providedprovided Insulation Deployment Active control mechanisms Deep Space 1 Deep Space 1 Deployed Kepler Kepler Sunside A-Train Formation StarDust Giotto In the LV Lightband MESSENGER Vibration Test Thoughts on Space Some comments overhead at the Officer’s Club •• It’s It’s aa reallyreally bigbig placeplace withwith nono air.air. •• There’s There’s nothingnothing outout there,there, isis there?there? •• How How manymany g’sg’s isis thatthat satellitesatellite pullingpulling whenwhen thethe groundground tracktrack makesmakes thosethose turns?turns? •Why•Why can’tcan’t II havehave mymy spyspy satellitesatellite permanentlypermanently positionedpositioned overover Moscow?Moscow? Useful Characteristics of Space •• Global Global perspectiveperspective oror “There’s“There’s nothin’nothin’ there there toto blockblock youryour view”view” •• Above Above thethe atmosphereatmosphere oror “There’s“There’s nono airair toto messmess upup youryour view”view” •• Gravity-free Gravity-free environmentenvironment oror “In“In free-fall,free-fall, youyou don’tdon’t noticenotice thethe gravity”gravity” •• Abundant Abundant resourcesresources oror “Eventually,“Eventually, wewe willwill minemine thethe asteroids,asteroids, collectcollect moremore solarsolar power,power, colonizecolonize thethe moon,moon, .. .. .”.” Global Perspective AmountAmount ofof EarthEarth thatthat cancan bebe seenseen byby aa satellitesatellite isis muchmuch greatergreater thanthan cancan bebe seenseen byby anan Earth-boundEarth-bound observer.observer. Low-EarthLow-Earth orbitorbit isis closercloser thanthan youyou think.think. Space isn't remote at all. It's only an hour's drive away if your car could go straight upwards. —Fred Hoyle Instantaneous Access Area H IAA IAA= K (1− cosλ) λ A K = 2.55604187×108 km2 Re A R cosλ = e Re + H Example:Example: SpaceSpace shuttleshuttle Re = 6378 km A friend of mine once sent me a post card with a picture of the entire planet Earth H = 300 km taken from space. On the back it said, cosλ = 0.9551⇒ λ =17.24o “Wish you were here.” — Steven Wright IAA =11,476,628 km2 Above the Atmosphere •• This This characteristiccharacteristic hashas severalseveral applicationsapplications –– Improved Improved astronomicalastronomical observationsobservations –– “Vacuum” “Vacuum” for for manufacturingmanufacturing processesprocesses –– Little Little oror nono dragdrag toto affectaffect vehiclevehicle motionmotion •• However, However, therethere reallyreally isis “air”“air” in in spacespace –– Ionosphere Ionosphere affectsaffects communicationscommunications signalssignals –– “Pressure” “Pressure” can can contaminatecontaminate somesome processesprocesses –– Drag Drag causescauses satellitessatellites toto speedspeed upup (!)(!) andand orbitsorbits toto decay,decay, affectingaffecting lifetimelifetime ofof LEOLEO satellitessatellites Vacuum Effects •• While While spacespace isis notnot aa perfectperfect vacuum,vacuum, itit isis betterbetter thanthan Earth-basedEarth-based facilitiesfacilities –– 200 200 kmkm altitude:altitude: pressurepressure == 1010-7-7torrtorr = = 1010-5-5PaPa –– Goddard Goddard vacuumvacuum chambers:chambers: pressurepressure == 1010-7-7torrtorr •• Outgassing Outgassing –affects–affects structuralstructural characteristicscharacteristics –– possibility possibility ofof vaporvapor condensationcondensation Wake Shield Facility (shuttle experiment) Atmospheric Drag •• Can Can bebe modeledmodeled samesame asas wiwithth “normal”“normal” atmospheric atmospheric flightflight 1 2 D = 2 CD AρV −h / H ρ ≈ ρSLe •• Key Key parameterparameter isis thethe “ballistic“ballistic coefficient”:coefficient”: m /(CD A) •• Larger Larger ballisticballistic coefficientcoefficient (small(small massivemassive satellite)satellite) impliesimplies slowerslower orbitalorbital decaydecay •• Smaller Smaller ballisticballistic coefficientcoefficient impliesimplies fasterfaster orbitalorbital decaydecay •• Energy Energy lossloss perper orbitorbit isis ≈ 2πrD Better not take a dog on the space shuttle, because if he sticks his head out when you're coming home his face might burn up. — Jack Handey Weightlessness ThisThis illustrationillustration fromfrom JulesJules Verne’sVerne’s RoundRound thethe MoonMoon showsshows thethe effectseffects ofof “weightlessness”“weightlessness” on on thethe passengerspassengers ofof TheThe GunGun Club’sClub’s “bullet”“bullet” capsule capsule thatthat waswas firedfired fromfrom aa largelarge gungun inin Florida.Florida. TheThe passengerspassengers onlyonly experiencedexperienced thisthis atat thethe half-half- wayway pointpoint betweenbetween thethe EarthEarth andand thethe Moon.Moon. PhysicallyPhysically accurate?accurate? Zero-Gravity? ThisThis plotplot showsshows howhow gravitygravity dropsdrops offoff asas altitudealtitude increases.increases. NoteNote thatthat atat LEO,LEO, thethe gravitationalgravitational accelerationacceleration isis aboutabout 90%90% ofof thatthat atat Earth’sEarth’s surface.surface. Microgravity •• Weightlessness, Weightlessness, freefree fall,fall, oror zero-gzero-g •• Particles Particles don’tdon’t settlesettle outout ofof solution,solution, bubblesbubbles don’tdon’t rise,rise, convectionconvection doesn’tdoesn’t occuroccur •• Microgravity Microgravity effectseffects inin LEOLEO cancan bebe reducedreduced toto 1010-1-1 gg (1(1 µµg)g) On Earth, gravity-driven buoyant convection causes a candle flame to be teardrop-shaped (a) and carries soot to the flame's tip, making it yellow. In microgravity, where convective flows are absent, the flame is spherical, soot- free, and blue (b). A Brief History of Orbital Mechanics AristotleAristotle (384-322 (384-322 BC)BC) PtolemyPtolemy (87-150(87-150 AD)AD) NicolausNicolaus Copernicus Copernicus (1473-1543) (1473-1543) TychoTycho Brahe Brahe (1546-1601) (1546-1601) JohannesJohannes KeplerKepler (1571-1630) (1571-1630) GalileoGalileo GalileiGalilei (1564-1642) (1564-1642) SirSir IsaacIsaac NewtonNewton (1643-1727) (1643-1727) Kepler’s Laws I.I. TheThe orbitorbit ofof eacheach planetplanet isis anan ellipseellipse withwith thethe SunSun atat oneone focus.focus. II.II. TheThe lineline joiningjoining thethe planetplanet toto thethe SunSun sweepssweeps outout equalequal areasareas inin equalequal times.times. III.III. TheThe squaresquare ofof thethe periodperiod ofof aa planet’splanet’s orbitorbit isis proportionalproportional toto thethe cubecube ofof itsits meanmean distancedistance toto thethe sun.sun. Kepler’s First Two Laws I.I. TheThe orbitorbit ofof eacheach planetplanet isis anan ellipseellipse withwith thethe SunSun atat oneone focus.focus. II.II. TheThe lineline joiningjoining thethe planetplanet toto thethe SunSun sweepssweeps outout equalequal areasareas inin equalequal times.times. Kepler’s Third Law III.III. TheThe squaresquare ofof thethe periperiodod ofof aa planet’splanet’s orbitorbit
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