ST8 Validation Experiment:Ultraflex-175 Solar Array Technology Advance: Deployment Kinematics and Deployed Dynamics Ground Testing and Model Validation

Abstract

The UltraFlex-175 solar array technology was chosen by NASA's New Millennium ST8 Program to be systematically advanced from a laboratory environment to system model or prototype demonstrated in a relevant (or simulated, ground) environment. This new solar array provides breakthrough performance beyond the current state-of-the-art rigid panel composite solar arrays due to its unique radial, tensioned membrane architecture and compact stowage volume. UltraFlex’s benefits include power-to-weight improvement, increased deployed frequency, and reduced deployed mass moment-of-inertia. A novel test method was used wherein the base was fixed and a displacement controlled sinusoidal-sweep excitation is minimally applied at a point on the array structure. At a natural frequency of the array, minimal force is required to keep the array vibrating at the controlled displacement input and also results in a low displacement response over the entire array. This method enabled quick, multiple, and repeatable tests because the minimal response avoids risk of damaging the hardware. This dynamics testing, along with deployment kinematics testing, was performed in both ambient pressure and vacuum conditions. Crucial to the accurate measurement of the test hardware kinematics and deployed dynamics was the development of off-loaders that minimize any influence on the system. The comprehensive ST8 ground test regimen performed on the high-fidelity 5.5-meter prototype UltraFlex solar array advanced this solar array technology making it ready for infusion into a wide range of manned and unmanned space missions.