MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
Contact: John G. Watson
FOR IMMEDIATE RELEASE
ROCKET SCIENTIST PEEKS INTO THE PHYSICS OF PROPELLANTS
While the term “rocket scientist” gets tossed around rather
loosely these days, Dr. Josette Bellan, a senior research
scientist at NASA’s Jet Propulsion Laboratory, is the genuine
article, spending much of her time pondering the mysteries of
propellants at high pressures and temperatures.
Bellan is currently leading research to help better
understand the intricacies of high-pressure fluid behavior, which
could help in the eventual use of powerful computers to simulate
what goes on in combustion chambers. That could result in
significant cost savings over the current rocket design standard,
which is primarily based on hardware testing.
Bellan and one of her associates, JPL’s Dr. Kenneth Harstad,
are about to publish a paper in the International Journal of
Multiphase Flow that may provide researchers with key elements
needed to unlock the mystery of high-pressure fluid behavior.
The work, titled “An All-Pressure Fluid Drop Model Applied
To a Binary Mixture: Heptane in Nitrogen,” due to be published
this spring, documents the accuracy of their model of a single
hydrocarbon droplet in a high-pressure environment, emulating the
conditions that propellants endure in combustion chambers. It
also pinpoints differences between low- and high-pressure fluid
behavior.
The model highlights the importance of a previously
neglected quantity, the “thermal diffusion factor,” describing
how a highly localized change in temperature within a mixture of
fluids can give rise to a flow of one ingredient in that mixture
compared to the rest of the ingredients. Conversely, this factor
describes how local changes in ingredients can give rise to local
changes in temperature.
While typically playing no role at ordinary atmospheric
pressure, the thermal diffusion factor becomes important at high
pressures.
“Because this factor is usually unimportant, quantifying it
has not been a high priority in the past,” said Bellan, who holds
a Ph.D. in aerospace and mechanical sciences from Princeton
University and now conducts research in JPL’s Thermal and
Propulsion Engineering Systems section. Reared in France, she
earned a master of science in applied mathematics from the
University of Sciences in Paris.
“Our research shows that if we want to understand
propellant behavior under high pressure, knowing this factor is
in fact very important,” she adds.
She points out that this model brings scientists a step
closer to creating realistic computer simulations of rocket, jet
and diesel engine combustion chambers. Long-term benefits will
likely include cost savings and greater design accuracy.
Those simulations may well lead to new estimates of the
ideal size of combustion chambers, because those simulations will
now include the thermal diffusion factor, whose importance has
been proven by this model.
This research has been supported by the Advanced Subsonic
Technology Program at the NASA Glenn Research Center, Cleveland,
OH, and by the NASA Marshall Space Flight Center, Huntsville, AL.
The Jet Propulsion Laboratory is a division of the
California Institute of Technology, Pasadena, CA.
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