A theoretical model that predicts the time-dependent behavior of a pyrotechnically actuated mechanism and a computer program that implements the model have been developed. The model and program are especially applicable to a pyrotechnic device known as the NASA Standard Initiator (NSI). Before this model and program were developed, the only principles that guided the design of pyrotechnically actuated mechanisms were those derived through empiricism.

The theoretical model includes (1) equations of conservation of mass, momentum, and energy, (2) equations of state, (3) equations of reaction kinetics, and (4) the assumption that there are no spatial variations in the relevant physical and chemical quantities (the "well stirred reactor" assumption). The computer program that solves the model equations is written in FORTRAN 77. This program requires the use of two other programs, known as "CET88" and "Chemkin," that are standard for calculations of the type in question.

The program has been found to predict accurately (as determined by comparison with experimental observations) the pressure history of an NSI firing into a pin-puller device, a closed vessel that has a volume of 10 cm3, and an apparatus called the "Dynamic Test Device." The program has also remedied several conceptual errors in prior design models.

This work was done by Joseph M. Powers and Keith A. Gonthier of the University of Notre Dame for Glenn Research Center. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Physical Sciences category.

Inquiries concerning rights for the commercial use of this invention should be addressed to

NASA Glenn Research Center
Commercial Technology Office
Attn: Steve Fedor
Mail Stop 4 — 8
21000 Brookpark Road
Cleveland
Ohio 44135.

Refer to LEW-16869.


NASA Tech Briefs Magazine

This article first appeared in the May, 2000 issue of NASA Tech Briefs Magazine.

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