TABLE OF CONTENTS Radiation is the only means for rejecting satellite waste heat in space and is often the dominant mode of heat transfer among large structures. This has naturally led to considerable involvement by thermal engineers who, in the process, have advanced some of the most practical methods for dealing with radiation problems. Much of the development has been in computer software (known as thermal programs) with the versatility to treat practically any situation. The speed and numerical accuracy of most of these programs are presently at a very satisfactory level, with more being done to simplify utility and improve graphics.
Radiation mathematics involves integral equations that cast the energy exchange at a surface as function of direction, wavelength, temperature, and surface properties. But because only average values of properties are usually known and radiation distribution data are limited and often inconsistent, it is found both practical and useful in thermal control to replace some formally defined relations with equations and quantities that represent averages over the regimes of applicability. It is in this context that radiation exchange factors and optical properties (emissivity, absorptivity, and reflectivity) are quoted and used. The approach simplifies an otherwise extremely complicated problem and establishes a basis for a tractable analysis and for finding properties by measurements. By way of justification, it may be pointed out that the methods adopted have not been seriously refuted by evidence from test or flight data.
Foremost among the relations to formal radiation physics are the spectral and directional...
