The size of aluminum oxide particles produced by small rocket motors is determined by tank collection and spectrophotometry. The size of the particulate determines loss in thrust due to particle lag, particulate radiant heat transfer, acoustic attenuation and impingement and rocket plume structure and properties

Dobbins, R. A.

Strand, L. D.

English

NASA Technical Reports Server

November 1969	 Brief 69-10572 
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., 
A Comparison of Two Methods of Measuring Particle

Size of Al203
 Produced by a Small Rocket Motor 
.
Knowledge of the size of the particulate effluent of 
solid propellant rocket motors containing aluminum 
as a fuel additive allows prediction of thrust loss due 
to particle lag, the particulate radiant heat transfer, 
the particulate acoustic attenuation, particle impinge-
ment, and the rocket plume structure and properties. 
Study of the particle size of the Al 20 3
 produced by 
a small rocket motor as determined by tank collection 
and by spectrophoto metric tests helps to explain a 
previous discrepancy and to realize the potential of 
using both of these methods of size measurement in 
a complementary manner. 
Principal variables in the tank collection tests per-
formed are tank volume, aluminum loading in the pro-
pellant, and chamber pressure. Various mean diam-
eters, moment ratios, and the mass median diameter 
are factors used for analysis of particle size data from 
these tests. By defining the mean size in terms of low 
moments of the distribution function, the tank collec-
tion tests give internally consistent results. Particle 
size is independent of receiver tank capacity, inde-
pendent of aluminum concentration within the pro-
pellant, and weakly dependent on rocket motor cham-
ber pressure.
Aluminum content and chamber pressure are the 
principal variables in spectrophotometric tests per-
formed at three wavelengths on rocket motors. Inter-
pretation of the transmission measurements with 
internal consistency is possible by postulating that 
the size distribution is bimodal. Results of these tests 
agree with those of the tank collection tests, namely, 
that particle size is independent of aluminum concen-
tration within the propellant and weakly dependent 
on rocket motor chamber pressure. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP 69-10572 
Patent status: 
No patent action is contemplated by NASA. 
Source: R. A. Dobbins and L. D. Strand of 
Caltech/JPL 
under contract to 
NASA Pasadena Office 
(N PO- 1 1198) 
Category 03 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the UniteØ 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.
https://ntrs.nasa.gov/search.jsp?R=19690000535 2020-03-16T18:07:55+00:00Z


A comparison of two methods of measuring particle size of Al2O3 produced by a small rocket motor

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