Pyrotechnically actuated valves are triggered on or off by firing an explosive charge that rapidly releases large amounts of high-pressure, gas. Pyrovalves are generally used for critical safety functions in almost all liquid and solid rocket systems and are designed to be fail-proof and provide extremely reliable actuation. However due to the lack of mature analysis tools, current design practices and safety analysis are heavily based on empiricism and are testing driven. The innovation proposed here is a comprehensive design and analysis tool that can characterize the transient performance of pyrotechnic actuators and provide a virtual test bed to assess performance and functional margin of these systems. The objective under this effort would be to develop a comprehensive three-dimensional transient tool that would simulate the gas --dynamic interactions with combustion, and model thermal effects in the valve material. For more complex initiator designs where multiple initiators may be fired, the tool could be used to identify "skew" effects resulting from the offset between the initiator firings. Since pyrovalves are ubiquitous and necessary for any rocket system, the tools and technology developed here would be useful to a broad variety of programs of core interest to NASA including the constellation program.