Satellite Thermal Control Engineering - TAK) 2000

1 SME04, 25jun04, 66 ESTECT hermal & Structure DivisionSatellite Thermal Control Space Agency, Estec, Thermal and Structure DivisionKeplerlaan 1,PO Box 299, 2200AG Noordwijk, The NetherlandsTel +31 715654554, Fax+31715656142prepared for SME 2004"ISSENVISATERSL1 HIPPARCOSECSOLYMPUSARTEMISSPACELABISOULY SSESHUYGENSSOHOGIOTTOCASSINIMSGARIANESME 04, 25jun04, 66 ESTECT hermal & Structure DivisionSatellite Thermal Control Engineering1. heat transfer basics conduction radiation importance of thermo-optical properties2. Satellite energy balance from ground to space simple Satellite Thermal behaviour3. role why Thermal Control required? what is Thermal design? which types of S/C design exist?

2 What to Control the flux/temperaturesWhat you will learn?SME04, 25jun04, 66 ESTECT hermal & Structure DivisionROSETTA* FM in LSS, dec01*without Solar Panels1. Heat Transfer BasicsThermal Control transfer energy , 25jun04, 66 ESTECT hermal & Structure DivisionROSETTA* FM in LSS, dec01*without Solar Satellite Heat Transfer Transfer heat transfer , 25jun04, 66 ESTECT hermal & Structure Satellite Heat Transfer Modes Conduction between any body eventually by contact through an interface Radiation main mode of heat transfer in vacuum/space Convection manned tended satellites (ISS, shuttle, launchers, ) Ablation combination of 3 and chemical reaction (re-entry vehicles)

3 SME04, 25jun04, 66 ESTECT hermal & Structure DivisionROSETTA* FM in LSS, dec01*without Solar Transfer heat transfer , 25jun04, 66 ESTECT hermal & Structure Conduction Definition propagation of energy from particle to particle in solid, liquid or gaseous continuous matter, homogeneous or not without matter displacement Fourier s Law is the heat flow rate vector (W/m2) is the material Thermal conductivity ( ) one-dimensional conductionTkq =rrqrkqrT(x,y,z)nr()chTTlAkQ =T(x)ThTcAlkSME04, 25jun04, 66 ESTECT hermal & Structure Conduction + + + +031101001000 Temperature (K) Thermal Conductivityk ( )CopperAluminiumAA5083-T0304 ssG-10 // to warpTiEpoxy PE //Cu-Ni (70-30)Brass Cu-ZnMylar PETamorphous(90-10)

4 SME04, 25jun04, 66 ESTECT hermal & Structure DivisionROSETTA* FM in LSS, dec01*without Solar Transfer heat transfer , 25jun04, 66 ESTECT hermal & Structure Radiation Characteristics propagation of electro-magnetic energy in straight line between surfaces separated by absorbing, scattering media or in vacuum hence without matter displacement reflected, absorbed or transmitted on surrounding bodies Source Thermal agitation of particlesSME04, 25jun04, 66 ESTECT hermal & Structure Radiation -Black Body Black Body is real or fictitious surface that absorbs all incident radiant energy from every direction at every wavelengths isotropic emitter radiated energy depends only on temperature Black Body Emitted Energyhemispherical spectralhemispherical totalemissive poweremissive power(W/m2.)

5 M)(W/m2) =1252,TkchTBechE 40,,TdEETTbb == Planck s LawStefan-Boltzmann s Law()1,== ()1,== SME04, 25jun04, 66 ESTECT hermal & Structure Radiation Black BodyPlanck and Stefan-Boltzmann , Wavelength ( m)E , , Hemispherical SpectralEmissive Power (1014 W/m2. m) K255 m12 mArea = TE4E , , Hemispherical SpectralEmissive Power (107 W/m2. m)Area = TS4 Planck and Stefan-Boltzmann , Wavelength ( m)E , , Hemispherical SpectralEmissive Power (1014 W/m2. m) K255 m12 mArea = TE4E , , Hemispherical SpectralEmissive Power (107 W/m2. m)Area = TS4 SME04, 25jun04, 66 ESTECT hermal & Structure Radiation -Real Body can absorb, reflector transmitradiation energy-all parameters are wavelength andangular dependent-general case.

6 Semi-transparent-opaquehence()()()1=++ incident s specularlyreflected d diffuselyreflected absorbed transmitted()0= ()()1=+ ds +=SME04, 25jun04, 66 ESTECT hermal & Structure Division Surface Emissivity ratio of surface radiated energy to that of a black body at the same T always <1 for a real surfacefor a black body depends on direction and wavelength of emitted energy therefore can be directional (d) or hemispherical (h) spectral (s) or total (t) averaged over all directions, wavelengths or Radiation -Real Body()1,0,0,,<= dEdETTT()1,== SME04, 25jun04, 66 ESTECT hermal & Structure Division Surface Absorptivity ratio of surface absorbed energy to incident energy always <1 for a real surfacefor a black body depends on incident energy direction and wavelength therefore can be directional (d) or hemispherical (h) spectral (s) or total (t) averaged over all directions, wavelengths or Radiation -Real Body()1,0,0,,<= dEdETTT()

7 1,== SME04, 25jun04, 66 ESTECT hermal & Structure Division Absorptivity vs Emissivity for a given direction and at any wavelength in general hemispherical total values are differentbecause and have a strong wavelength dependence source temperatureof incident radiation (Sun at 5776 K) differentthansurface temperature( Satellite 250 -> 300 C) Radiation -Real Body()() =,,,2ndKirchoff sLaw SME04, 25jun04, 66 ESTECT hermal & Structure Division Solar Absorptivity Sand Hemispherical Emissivity H Sis the solar absorptivity refers to UV wavelengths S= Sintegrated over m 95% solar spectrum His the hemispherical emissivity refers to IR wavelengths H= Hintegrated over 5-50 m body at 250/300 Cbut S Hbecause the spectra are Radiation -Real BodySME04, 25jun04, 66 ESTECT hermal & Structure Radiation -Data Spectral Reflectance Zinc Oxide Potassium Silicate Coating Black Body Emittance integration over solar (5776K) wavelengths s= integration overinfraredblack body (300K)

8 Wavelengths h= PSG120-FD , Wavelength ( m)E , , Hemispherical SpectralEmissive Power (1014 or 107 W/m2. m) K255 m , Spectral Reflectance (-)12 mMAP PSG120-FD , Wavelength ( m)E , , Hemispherical SpectralEmissive Power (1014 or 107 W/m2. m) K255 m , Spectral Reflectance (-)12 mSME04, 25jun04, 66 ESTECT hermal & Structure Radiation -Data Typical ValuesFinish S H S/ HVD (Ag 2 mils) , 25jun04, 66 ESTECT hermal & Structure Radiation -Black Body Radiated Energy between Black Bodieswith Fij, the view factorbetween surface i and surface jorwhen()44jiijiijTTFAQ = AiAjTiTjQijdAidAj()44jiiijTTAQ = 1=ijFSME04, 25jun04, 66 ESTECT hermal & Structure DivisionROSETTA* FM in LSS, dec01*without Solar Panels2.

9 Satellite Energy BalanceThermal Control transfer energy , 25jun04, 66 ESTECT hermal & Structure Division2. Satellite Energy BalanceWHAT HAPPENS fromGROUNDtoSPACE ?SME04, 25jun04, 66 ESTECT hermal & Structure Division Ultra-high Vacuum, 10-14bar < p < 10-17bar => no convection temperature levels Deep Space, @ K imbalance, temperature levels and gradients Solar Eclipse SSO SPOT, ENVISAT32 mn GEO MSG72 mn HEO CLUSTER5 h max2. Satellite Energy Balance - Thermal Environment0 52 PENUMBRAPENUMBRAUMBRASME04, 25jun04, 66 ESTECT hermal & Structure Division intense Solar Flux, SC=1367 W/m2@ 1 AU imbalance, temperature levels and gradients2. Satellite Energy Balance - Thermal Environment2 SSdSC= Solar Intensity vs Sun Distance (AU)Intensity (W/m2) Intensity (SC)EarthMercurySaturnMarsJupiterSME04, 25jun04, 66 ESTECT hermal & Structure Division2.

10 Satellite Energy Balance - Thermal Environment AlbedoFlux reflected by Sun illuminated side of Planet albedo= ratio of solar reflected energy to local solar flux EarthalbedoaE= to 410 W/m2 aEvaries with landscape Planet Flux infrared energy radiated by the Planet Earth=blackbody @255 K (-18 C)equivalent to 240 W/m2incident2 ERSCa SC2)1(ERSCa reflectedabsorbed244 EERT emittedSME04, 25jun04, 66 ESTECT hermal & Structure Division2. Satellite Energy BalanceEquilibrium Temperature of a Spherefrom Ground to Space (degC)Altitude (km)BlackWhiteGoldAirEquilibrium Temperature of a Spherefrom Ground to Space (degC)Altitude (km)BlackWhiteGoldAirSME04, 25jun04, 66 ESTECT hermal & Structure Division2.