Mission Design for the CubeSat OUFTI-1

CHAPTER 9.THERMAL-CONTROL SYSTEMTable 9.1: Surface thermal propertiesαα ɛ Tɛ eqWHITE 0.2 0.9 0.22 0 ◦ CBLACK 0.94 0.9 1.04 125 ◦ CGOLD 0.25 0.04 6.25 350 ◦ C9.2 Analytic temperature determinationIn order to have an idea of the satellite’s equilibrium temperature, we representit as a flat plate hit by solar radiation and albedo, exchanging heat withearth and cold space and dissipating 1W power. The thermal coefficients aredetermined doing an averaged weighed on the surface of solar cells and coating:¯ɛ = ɛ SCA SC + ɛ COAT A COAT0.1ᾱ = α SCA SC + α COAT A COAT0.1The thermal equilibrium says:(9.3)AᾱC s 1.3 +} {{ } }{{} 1 = 5Aσ¯ɛ ( )T 4 − Tcold4 + Aσ¯ɛ ( )T 4 − Tearth4 } {{ } } {{ }sun+albedo dissipationspaceearth(9.4)where T cold = 5k is the cold space temperature and T earth = 255K is the standardearth surface temperature.In this model, we consider that the sun and the albedo act like a visible fluxeach one on a face, that one face is radiating to the earth and not to the coldspace and therefore only 5 faces are radiating to cold space. All these hypothesiswill be explained in the next paragraph.In table 9.2, the average thermal coefficient and the equilibrium temperatureare reported.Table 9.2: Equilibrium temperaturesα ɛ T eqWHITE 0.63 0.84 265.5 KBLACK 0.92 0.84 287 KGOLD 0.65 0.49 301.3 KThese temperatures will also be used as first guess for the nodes model whichwill be introduced in the next paragraph.Galli Stefania 87 University of Liège