Demonstration of 3D printed Phase Change Material Heat Capacitors for Space Application

As peak dissipations in combination with thermal constraints become more and more a limiting factor in radar-satellite or planetary rover missions, it is becoming increasingly attractive to buffer the dissipated heat and release them over a greater period of time, e.g. one full orbit or one day/night cycle. An efficient way of storing large amounts of heat is the phase transition of pure substances, which occurs isothermal. To demonstrate this, two heat capacitors, each consisting of a 3D-printed housing, including an internal heat spreader, and Octadecane (C18H38) have been developed and built. Each prototype weights about 350g and has a capacity of 24.4kJ only in the alkanes phase transition, happening at 28�C. Those prototypes were then successfully subjected to a series of tests to verify thermal and mechanical models as well as the demonstration of its properties. The test sequence consists of determination of the thermal capacity, a thermal balance test in vacuum to determine the thermal conductivity, thermal vacuum tests for 8 thermal cycles from -50�C to 80�C and a theoretical use-case scenario, a CT-scan after the thermal tests and mechanical tests, including Eigen frequency searches and random vibration tests. This paper will discuss the design, modelling and testing of those prototypes to provide first lessons learned.