Launch Vehicle Avionics Passive Thermal Management

Abstract

A passive thermal management system was designed to cool avionics on a launch vehicle for 3 different thermal modes. Prior to launch, the heat sink for the avionics is purge duct flow. During the 10 minute launch period, the thermal energy is stored in phase change material (PCM). On orbit, the heat sink is a radiator. The system consists of 1. A high conductivity thermal shelf, 2. A PCM thermal storage system, 3. Heat pipes to conduct the heat from the shelf to the heat sinks, 4. Fins to reject the heat to the purge duct, and 5. A radiator to reject the heat on orbit. A unique aspect of the system design is the avionics shelf, which contains embedded heat pipes. While the electronics locations are fixed before manufacturing with encapsulated high conductivity material, this design allows the avionics boxes to be positioned anywhere. A second benefit is the much higher thermal effective thermal conductivity, which can approach 2500 W/m K in long systems. A low-cost, simplified version of the system to fabricated to verify the design during ground testing, consisting of the high conductivity plate, the heat pipe, and the purge duct sink. The general performance matched expectations, except that the overall ΔT was higher than expected, due to the thermal interface materials. This can be improved with a better material.