The Thermal Protection System (TPS) for the Space Shuttle consists of an outer layer of rigid surface insulation tiles. It is important that an accurate understanding of the thermal behavior of this system be obtained prior to usage. This computer program was developed to compute the transient temperature history and the steady-state temperatures of complex body geometries in three dimensions. Emphasis has been placed on the type of problems associated with the TPS, but the program could be used in the thermal analysis of most three-dimensional systems.
The thermal model is subdivided into sections, or nodes, to a level of approximation which yields the desired level of accuracy. Input to the program consists of a geometrical description of the physical system, the material properties, and selected boundary conditions. The boundary conditions are used to account for heat flux, reradiation, radiation interchange, convection, fixed temperatures, and phase changes. The program will accommodate a thermal model with as many as 500 nodes, 4000 conductors, 3600 radiation interchange conductors, and 75 of each type of boundary condition. The program solves the differential equations describing the transient and steady state behavior of the model using finite difference techniques. For the transient analysis, the user may select either a forward difference method, a midpoint difference (Crank-Nicolson) method, a backward difference method, or an alternating direction method to numerically solve the governing equations. For the steady-state analysis, a modified backward difference method is available. Program output is in the form of temperature versus time histories for each section of the thermal model. (Rockwell International Corp. for NASA Marshall).
This program was released by NASA through COSMIC as MSC-18616. The italicized text above is from the official NASA release.