Long Lived Venus Lander Thermal Management System Design

Abstract

The thermal management system for a Long Lived Venus Lander is critical for mission success. The difficult operating environment on Venus, 460°C and 92 atm pressure, presents significant thermal design and implementation challenges. No previous mission has operated for more than two hours on the surface of Venus and missions with longer operating duration are needed for a more consistent science return. Dyson et al. have proposed a Stirling system that generates power as well as provides cooling to allow the lander’s instruments to survive for more than one Venusian year in the harsh environment of Venus’ surface. It consists of a multi-stage cooling system using several Stirling engines in reversed cycle, and an energizing radioisotope Stirling power converter that is coupled (electrically or pneumatically) to the Stirling coolers. During operation, heat is supplied by the High Temperature Thermal Management System (HTTMS) to the main (energizing) Stirling converter at approximately 1000°C. The converter provides power to the instruments and the Stirling coolers. The waste heat from the Stirling converter is at roughly 500°C, and must be rejected to the Venusian environment via the Intermediate Temperature Thermal Management System (ITTMS). The Venus lander has to operate successfully in four different modes: (1) space transit with the Stirling deactivated, (2) precooling in space prior to entry, (3) nominal operation on Venus, and (4) stoppage of the Stirling on Venus. This is accomplished using a variable conductance heat pipe (VCHP) as the primary component of the HTTMS and a diode heat pipe (DHP) for the ITTMS. Systematic system level thermal analysis has been carried out on the HTTMS and the ITTMS simultaneously due to their strong thermal interaction. The goal was to observe critical temperatures and thermal resistances within the system when applying boundary conditions that correspond to each mode.