Method utilizes an analytical model, a method of solution which is compatible with digital computer analysis, and a generalized computer program to carry out the computations

Bobco, R. P.

Egendorf, F. L.

Mc Grath, R. J.

English

NASA Technical Reports Server

August 1971
	 Brief 71-10295 
NASA TECH BRIEF 
Manned Spacecraft Center	 1IL 
A	 - 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a aubscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the. Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Determination of Radiation Interchange Factors 
The problem: 
To devise a method for the analytical and empirical 
determination of radiation interchange factors. 
The solution: 
An analytical model, a method of solution which 
is compatible with digital computer analysis, and 
a generalized computer program to carry out the 
computations. 
How it's done: 
The program computes thermal and solar radiation 
interchange factors among surfaces having any com-
bination of the following properties: 
1. Diffuse emittance and reflectance, 
2. Diffuse emittance and specular reflectance, 
3. Diffuse emittance and components of diffuse 
and specular reflectance, and 
4. Directional emittance and bidirectional reflec-
tances. 
Enclosures which contain only the first three types 
of surfaces may be simulated by a maximum of 1500 
surfaces. Fully bidirectional enclosures are limited to 
38 surfaces or less. The maximum number of surfaces 
in a mixed enclosure is governed by 
NM+M — N 
where M = total number of surfaces, and N = num-
ber of bidirectional surfaces. 
In addition to the standard node-to-node matrix 
formulation, a mean-to-local approximation is avail-
able as a user's option. The method utilizes average
property values for groups of surfaces. This can 
result in significant reductions in the size of the 
matrices and in the time required to invert them. 
The program input includes surface properties 
and geometrical data defining the shape, size, and 
location of each surface in the enclosure. The pro-
gram printout includes input data, form factors, 
exchange factors, the transfer matrix and its in-
verse, nodal areas, and interchange factors. 
Notes: 
1. This program is written in FORTRAN V for use 
on the UNIVAC-1 108 computer. 
2. Requests for further information may be directed 
to:
COSMIC 
112 Barrow Hall 
University of Georgia 
Athens, Georgia 30601 
Reference: B71-10295 
Patent status: 
No patent action is contemplated by NASA. 
Source: R. P. Bobco, F. L. Egendorf,

and R. J. McGrath of

Hughes Aircraft Co.

under contract to

Manned Spacecraft Center

(M SC- 13475) 
Category 09 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
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Determination of radiation interchange factors

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