Two computer programs calculate interaction effects of high speed spacecraft on the environment at altitudes from 90 km to 150 km. EXT program determines fluid field in bodies of arbitrary geometries in transient flow regime. INT program uses EXT output and measures flow conditions inside spacecraft body

Bienkowski, G. K.

Holman, J. M. L.

Mc Kinley, R. R.

Siskind, S. M.

English

NASA Technical Reports Server

December 1971
	
Brief 71-10499 
S
NASA TECH BRIEF 
Goddard Space Flight Center 
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 subscription 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. 
A Low-Altitude Satellite Interaction Study 
The problem: 
To devise a theoretical technique for calculating 
the interaction effects of a high-speed spacecraft on 
the environment at altitudes from 90 to 150 km. 
The free-molecular theory and the ordinary con-
tinuum fluid theory do not give accurate results 
for bodies in the superthermal velocity region. 
The solution: 
Two computer programs: EXT, which determines 
the fluid field in the neighborhood of bodies of 
certain arbitrary geometries in the so-called transi-
tional flow regime; and INT, which uses the output 
from EXT and measures the flow conditions inside 
the body cavity of a spacecraft. 
How it's done: 
The programs utilize a Monte Carlo approach, 
based oil Bird's direct numerical simulation tech-
nique, to conduct numerical experiments with a 
model gas. In the external flow program EXT, a 
velocity sample is determined for both the free-
stream and the interacted molecules. This velocity 
sample is in tabular form. A user-specified velocity 
range is defined by a number of equally-spaced 
velocity values. The table lists the velocity values 
along with the fractional number of colliding mole-
cules which have velocities less than the tabulated 
values. The fractions of free-stream and interacted 
molecules are also printed out. This information is 
used as input for the internal flow program, INT. 
The input velocity sample is curve-fitted by a poly-
nomial subroutine which is then used to generate
the velocity distributions of the molecules at the 
orifice opening of the cavity. 
The output of both programs includes initializa-
tion and periodic flow field parameter printouts. 
INT output includes periodic cavity surface param-
eter printouts and twelve molecular velocity distribu-
tions produced from the velocity sample input data. 
Notes: 
I. This program is written in FORTRAN IV for use 
on the I BM-360 computer. 
2. Subroutine REMTIM is a machine dependent 
subroutine and therefore is not included with the 
distributed versions of EXT and INT. The user 
of EXT and INT must provide his own version 
of this subroutine. 
3. Requests for further information may be directed 
to:
COSMIC 
112 Barrow Hall 
University of Georgia 
Athens, Georgia 30601 
Reference: B7 1-10499 
Patent status: 
No patent action is contemplated by NASA. 
Source: R.R. McKinley, G.K. Bienkowski,

S.M. Siskind, and J.M.L. Holman of

Radio Corp. of America

under contract to

Goddard Space Flight Center
(GSC- l 1384) 
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 ownedrights.
https://ntrs.nasa.gov/search.jsp?R=19710000496 2020-03-17T02:26:28+00:00Z


A low-altitude satellite interaction study

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