Structural tests determine experimentally the amount of thermal protection required on the Apollo service module because of plume impingement heating. Exhaust flow field analysis correlates with flat plate heating rate and surface pressure in a vacuum

Pieski, E. T.

Simkin, D. J.

English

NASA Technical Reports Server

December 1966
	 Brief 66-10633 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Predicting Surface Heating Rates and Pressures 
Resulting from Hot Exhaust Gases 
The reaction control system (RCS) rocket engines 
on the Apollo spacecraft are placed on the service 
module in such a manner that the effects of engine 
exhaust plume impingement on the vehicle (surface 
heating and surface pressure) are important to struc-
tural integrity. To determine experimentally the 
amount of thermal protection required on the service 
module because of plume impingement heating a 
series of tests was performed, and sufficient paramet-
ric data were obtained to allow a theoretical correla-
tion of the results. 
A report, "High Vacuum Plume Impingement Test 
Correlation," by E. T. Piesik, SID 64-1563, August 
1964, was prepared which presents analytical methods 
(backed up by experimental data) for predicting the 
heating rates and surface pressures which result from 
an exhaust plume impinging on a flat plate in space. 
These methods have been used to design the service 
module plume heat shields for the roll, pitch, and yaw 
reaction control system engines. 
The method of characteristics, described in the re-
oort. is capable of solving the complex problems in-
volved. Individual computer programs exist throughout 
industry which calculate various parts of the problem: 
chemical composition and engine performance param-
eters at various nozzle area ratios, three-dimensional 
nozzle characteristic flow field properties with variable 
specific heat ratio for performance loss calculations, 
and exhaust plume flow field characteristics based on
the nozzle exit Mach number and exit pressure. How-
ever, a computer program which currently accounts for 
all physical phenomena which make up the exhaust flow 
field of a contoured nozzle rocket engine is not 
known. Because of the complexity of calculating 
plume flow field for other than relatively simple nozzle 
exit conditions, the requirements for an exact flow 
field calculation must usually be relaxed. The report 
shows, at least for the engine tested, that a very simple 
analysis of the exhaust flow field will result in good 
correlation with the experimental data on heating rate 
and surface pressure for a flat plate impinged upon by 
an exhaust plume in a near-perfect vacuum. 
Note: 
The report is available from: 
Technology Utilization Officer 
Manned Spacecraft Center 
Houston, Texas 77058 
Reference: B66-10633 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: D. J. Simkin and E. T. Pieski 
of North American Aviation, Inc. 
under contract to 
Manned Spacecraft Center
(MSC-971) 
Category 05 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
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Predicting surface heating rates and pressures resulting from hot exhaust gases

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