Publications

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Satellites and launch vehicles are subject to pyroshock events that come from the actuation of separation devices. The shocks are high frequency transients that decay quickly—within 5-20 ms—and can be damaging events for satellites and their components. The damage risk can be reduced by good design practice, taking advantage of the attenuating properties of structural features in the load path. NASA and MIL handbooks provide general guidelines for estimating the attenuating effects of distance, joints, and other structural features in the load path between the shock source and the shock sensitive component. One of the challenges is adequately modeling the dissipative mechanisms in structural features to better understand the risk to shock sensitive components. Previously, we examined the modeling of pyroshock attenuation in a cylindrical structure and used peak acceleration to evaluate how much shocks are attenuated by distance and structural features in a cylindrical structure. In this work, we investigated different quantities to gain more insight into how and why pyroshocks get attenuated by a bulkhead. We found that the bulkhead affects the SRS peak more than the SRS ramp and that approximately 30% of the structural intensity of the pyroshock flows into the bulkhead regardless of the thickness.

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Pyroshock events from the actuation of separation devices in satellites and launch vehicles are potentially damaging, very short, high intensity events with high frequency content. The pyroshock damage risk is mitigated somewhat by the fact that the shock intensity is attenuated by the spacecraft structure. The NASA and MIL standards, developed from extensive tests performed in the 1960’s, provide pyroshock attenuation guidelines for various structures common to spacecraft and launch vehicles. In this paper, we present the results from a numerical investigation of pyroshock attenuation in cylindrical shell structures. Pyroshock events were modeled using Sandia National Laboratories’ engineering mechanics simulation codes, specifically Sierra/SD. Upon verifying the numerical simulation results against a NASA-HDBK-7005 curve, various structural features were added and design variables were varied to investigate their effects on pyroshock wave propagation and attenuation. The results showed that current numerical simulation tools, given appropriate tuning parameters, are capable of modeling pyroshock events in a simple cylindrical geometry at a reasonable cost. The numerical simulations showed that the presence of geometric features had greater attenuating effects than previously understood. However, shock attenuation levels were less sensitive to design variables of the structural features than expected.

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