An Active Cooling System for the Solar Probe Power System

The Solar Probe Plus (SPP) spacecraft will orbit the Sun closer than any other previous probe. As dictated by the current mission design, the spacecraft will achieve many perihelia as close as 9.5 RS from the Sun. During those passes, it will encounter a solar flux of ~500 suns, or 70 W/cm 2 . This flux is more than 50 times larger than the solar heating seen by any previous spacecraft. During the entire mission, the spacecraft and science instruments will be protected by a Thermal Protection System (TPS), and electrical power is produced by using somewhat conventional photovoltaic technology. Because of the high solar load, an active cooling system is required to remove the waste heat from the solar cell and transport it to a remote radiator system for rejection to deep space. As part of the SPP Pre-Phase A study, a specific effort focused on the development of the cooling system design, analysis, material, and test methods needed to address the basic feasibility of the system, and to develop the path needed to bring that system to a Technology Readiness Level (TRL) of 6 on the schedule needed for the flight project.