Force limited vibration testing and subsequent redesign of the Naval Postgraduate School CubeSat launcher

Abstract

The Naval Postgraduate School CubeSat Launcher (NPSCuL) is a five-sided structure capable of carrying up to 24 CubeSats to orbit. The vibration test environment for CubeSats flying on NPSCuL on the Atlas-V is extremely harsh, partly due to the input vibration environment from the launch vehicle itself, and partly due to amplification from the NPSCuL structure. This thesis documents the implementation of a relatively new technology, Force Limited Vibration Testing (FLVT), and the design of a stiffer structure to reduce the vibration environment for NPSCuL payloads. Most acceleration-controlled vibration tests result in significant over-test. FLVT limits shaker forces, producing more realistic tests and potentially provides relief to payloads. Additionally, increasing the stiffness of NPSCuL using an isogrid design, aimed to increase its first-fundamental frequency, could result in less displacement at higher frequencies for a given amount of input energy, possibly improving the payload vibration environment. It was found that FLVT was very successful in reducing vibration environments for NPSCuL payloads. Although redesigning NPSCuL using an isogrid design achieved the goal of increasing system stiffness, it did not reduce the vibration environment. None the less, lessons learned from the redesign process will be valuable for continuing vibration environment reduction efforts.