GUMRAP: A computer prgoram for analyzing molecular flow in complex enclosures

The General Unwanted Energy Rejection Analysis Program (GUERAP), which uses a Monte Carlo ray trace technique to analyze complex optical systems, has been in use for a number of years. This report describes the development of a molecular ray trace computer code (GUMRAP) based upon the extensive geometric and Monte Carlo ray trace portion of GUERAP. Portions of GUERAP strictly concerned with radiation such as diffraction, refraction, and internal radiation have been removed, and a new gas-surface interaction subroutine REFLCT, based upon the reciprocity relation, has been included. A detailed description of the input variables is given, as is a listing of control cards so that GUMRAP can be run on an IBM 370/165 computer by anyone desiring to analyze the molecular flow in complex systems such as space chambers.