SYSTEMS

Designs Ordnance-Induced Pyrotechnic Shock Tests to Accurately Simulate Hazardous Rocket Launch Environments Prior to Testing

National Technical Systems has developed a new, accurate, physics-based computer modeling approach that enables the custom design of shock test apparatus and setup needed to perform high intensity shock tests required on flight hardware for rocket launch vehicles. The modeling approach, developed by the NTS Ordnance Sciences Division based in Dana Point, CA, is the first of its kind created specifically for aerospace and defense customers in the Space Mission and Space Launch System (SLS) industry.

All flight hardware used in rocket engines and space craft must be tested to insure it can withstand pyrotechnic shocks that occur during launch, stage separations, and throughout the spacecraft mission profile and still function during flight. Historically, the method used to develop apparatus to perform these shock tests has been based on empirical experience gained only from prior testing that may not reflect the precise shock requirements imposed on the new flight hardware.

If the design of the ordnance induced pyrotechnic shock test does not accurately reflect the requirement, the results of the subsequent testing performed is difficult to assess, noted Jon Conner, NTS Director, Engineering Services, whose group created the new computer modeling approach. The actual tests, which involve inducing pyrotechnic shock by actually detonating explosives against the test apparatus to which the flight hardware is mounted, are expensive and time consuming so it's imperative that the test designs be accurate before they are conducted, Conner added.

"This is a dramatic paradigm shift for the industry," Conner said. "For years, this kind of testing was more an art than a science. Typically you would grossly over-test the hardware to insure the minimum shock level was achieved across the entire frequency spectrum, which can work if the hardware tests out positively. But if it fails, you don't know if it failed because the hardware needs to be re-developed to insure adequate margin, or if the failure was due to the gross over-test across much of the frequency spectrum. Our modeling approach brings more science to the pyrotechnic shock test design process, which leads to a better testing and more accurate interpretation of the results."

The model created by the NTS team is custom-designed to assure flight hardware developers that the tests will accurately meet their product shock test requirements and provide valid results that will qualify the hardware for space flight, Conner added.

"We actually model the test environment in excruciating detail," Conner said. "The result is a model that accurately replicates the physics of an ordnance induced pyrotechnic shock test."

NTS also performs the high intensity shock testing at its Santa Clarita facility using a pneumatic, cantilever beam shock machine based on a design created by Sandia National Laboratory.