How to Prevent Flight Hardware Failures During Shock Qualification Test?

In the last few years, there have been several recorded JPL hardware failures during shock qualification tests. These failures raised concerns amongst project management, cognizant engineers, analysts, and others stake holders. These concerns were wrongfully attributed by some to potential over-test using JPL’s tunable beam shock simulation system (TBSS), a conclusion that was not shared by experienced subject matter experts. All the failures from cases examined were traced to issues unrelated to the TBSS. The prime failure mode was traced, in most cases, to excessive sustained structural excitations occurring in mid- to high-frequency shock regions. Other issues were related to overly conservative requirements (in particular specification of the knee frequencies), over-test by test conductors, possible fixture coupling, and design deficiencies. In this paper, root causes of a few flight hardware failures are discussed in detail. A series of recommendations are provided to better prepare for shock tests and to help minimize or even eliminate flight hardware failures.