An Overview of the Thermal Challenges of Designing Microgravity Furnaces

Marshall Space Flight Center is involved in a wide variety of microgravity projects that require furnaces, with hot zone temperatures ranging from 300 C to 2300 C, requirements for gradient processing and rapid quench, and both semi-conductor and metal materials. On these types of projects, the thermal engineer is a key player in the design process. Microgravity furnaces present unique challenges to the thermal designer. One challenge is designing a sample containment assembly that achieves dual containment, yet allows a high radial heat flux. Another challenge is providing a high axial gradient but a very low radial gradient. These furnaces also present unique challenges to the thermal analyst. First, there are several orders of magnitude difference in the size of the thermal 'conductors' between various parts of the model. A second challenge is providing high fidelity in the sample model, and connecting the sample with the rest of the furnace model, yet maintaining some sanity in the number of total nodes in the model. The purpose of this paper is to present an overview of the challenges involved in designing and analyzing microgravity furnaces and how some of these challenges have been overcome. The thermal analysis tools presently used to analyze microgravity furnaces and will be listed. Challenges for the future and a description of future analysis tools will be given.