THERMAL MANAGEMENT OF INERTIAL NAVIGATION PACKAGE IN LONG DURATION MISSIONS
Indian Space Research Organization (ISRO) has placed multiple satellites in different orbits in a single mission using
PSLV rocket recently. Such complex missions are of 2 to 3
hours duration as compared to regular missions of 30 minutes. Thermal management of inertial navigation package becomes challenging due to prolonged exposure to deep space thermal environments. Apart from its high power dissipation it is exposed to radiative heating from solar and Earth emitted
radiation and radiation loss to deep space after heat shield
separation. Maximum computed temperature of inertial navigation package was reaching 54°C against a constraint of 45°C due to prolonged exposure to solar load. Temperature of the package has to be maintained within prescribed limits till the end of mission.
Optical Solar Reflector (OSR) is a candidate material which can be used as a barrier for solar load. However geometrical constraints imposed restrictions on application of OSR on the package surface. Simulations showed that the thermal management of the package can be carried out by enhancing the emission loss from bottom side of the deck below the package using OSR, during the period when the stage is in shadow of Earth. OSR on the bottom side of honeycomb deck plate helps to enhance the emittance from 0.10 to 0.80.
Thermal characterization of honeycomb deck was carried out with and without OSR under vacuum conditions by simulating power dissipation using resistive heater elements. Post-test thermal studies validated the thermal model of honeycomb with OSR and confirmed the effectiveness of thermal management scheme. The scheme was successfully implemented for long duration PSLV missions and the package temperatures were restricted within limits till end of mission.