Test program evaluates thermal and electric ignition mechanisms in selected nonmetallic materials found in spacecraft with concentrated oxygen atmospheres. The phenomena evaluated were spontaneous ignition, ignition of flammable vapor by a spark, and ignition by an arc where the arc produces the combustible vapor and the ignition source

Gerstein, M.

Mc Lain, M.

Ross, W.

English

NASA Technical Reports Server

May 1968	 Brief 68-10167 
NASA TECH BRIEF	 1 
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. 
Evaluation of Ignition Mechanisms in Selected

Nonmetallic Materials 
The fire hazard associated with concentrated 
oxygen atmospheres in enclosures has been recognized 
for many years. Spacecraft, deep submergence ve-
hicles, and high altitude simulators used in medical 
research often use such atmospheres. In spite of 
attempts to provide a greater margin of safety through 
more stringent material selection procedures, fires 
have occurred in chambers having high oxygen partial 
pressures. These incidents point up the need for better 
understanding of the ignition and flame propagation 
process for solid materials which will lead to advanced 
and improved materials screening and test methods. 
To this end, a test program was initiated to evaluate 
ignition mechanisms in selected nonmetallic materials 
usually found in the structures and fixtures of space-
craft, etc. The principal focus of attention in the study 
of ignition mechanisms has been associated with two 
types of ignition sources, thermal and electrical. Three 
separate phenomena may be considered in discussing 
the problem. 
The first phenomenon is closely related to the 
process variously called thermal ignition, autogeneous 
ignition, or spontaneous ignition. Heat acts as the 
energy source for ignition and in most cases also 
causes the formation of gases by vaporization, sub-
limation, or decomposition. The ASTM autogeneous 
ignition apparatus and various modifications of it 
provide tests for this type of ignition. 
The second process involves the ignition of a flam-
mable vapor by means of a spark or glowing surface. 
The source of flammable vapor may be vaporization 
of a volatile combustible or, for low volatility materi-
als, exposure to heat may (as in the thermal ignition 
process) generate flammable material by vaporization,
sublimation, or decomposition. The flash point and 
fire point tests are examples of standard procedures 
which provide this kind of information on materials. 
It should be emphasized that tests for these two 
processes are quite different. While heat may be the 
source of combustible vapor in both cases, in the flash 
point test an ignition source exists, such as a spark, 
flame, or glowing surface. In thermal ignition tests, a 
critical temperature is sought, below which no ignition 
occurs. Thermal ignition is thus a measure of the 
minimum energy required for ignition; flash point is a 
measure of the heat necessary to provide a combusti-
ble mixture. 
The third process involves ignition by a spark or arc 
where the arc is the source of energy producing the 
combustible vapor as well as the ignition source. Gen-
erally the energy in an arc is adequate to accomplish 
both purposes but the transfer of energy is very inef-
ficient. In any event, this process simulates the events 
occurring when a circuit is overloaded or when a short 
circuit exists. 
In order to scan quickly a variety of configurations 
and to investigate all three mechanisms, several differ-
ent ignition test configurations were used. Each con-
figuration was selected to provide data in a given 
environment. 
Note: 
Inquiries concerning this test program may be di-
rected to:
Technology Utilization Officer 
Manned Spacecraft Center 
Houston, Texas 77058 
Reference: B68-10167
(continued overleal) 
Now
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.
https://ntrs.nasa.gov/search.jsp?R=19680000167 2020-03-12T05:33:09+00:00Z
Patent status: 
No patent action is contemplated by NASA. 
Source: W. Ross, M. Gerstein, 
and Mary McLain 
of Dynamic Science 
under contract to 
Manned Spacecraft Center 
(MSC-1 1645, 11646, 11647) 
Brief 68-10167 Category 03


Evaluation of ignition mechanisms in selected nonmetallic materials

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