Why Workmanship Vibration Tests is Important to Prepare Flight Hardwar for launch

Recently, there has been a tendency during random vibration and sine vibration testing for spacecraft projects to eliminate or reduce minimum workmanship to levels low enough that the objective of performing an adequate workmanship screen during the test is defeated. The chief reason for not exposing flight hardware to adequate workmanship levels is that pre-test analysis shows the test will exceed the predicted structural capability of the hardware. Upon reviewing some of the recently predicted results, it became clear that some analysts did not include the force-limited method as part of their base-shake analysis. In this paper we will briefly discuss the history of the application of the minimum workmanship requirement at JPL and provide technical reasons why the minimum workmanship level has become a standard part of the screening tests that are performed on flight hardware. We will show that if force-limited analysis is performed properly, it will most likely bring structural margins into positive territory, therefore, eliminating the need for lowering workmanship requirements. We will provide a couple of examples exploring the importance of proper structural analysis in relationship to verifying that fight hardware is ready for launch.