Development of a Guided Wave Experiment for the International Space Station

Abstract

Structural health monitoring (SHM) has gained increasing interest among scientific and engineering communities. Among the many applications of SHM, aeronautics and space-structure development stand out as fields where the environment is especially harsh and managing material deterioration over time is a constant issue. This work reports the progress made in developing experiments designed to explore applications of SHM in space environments with a particular focus on elastic-wave propagation in metallic structures. Active elements of the proposed payload are piezoelectric ceramic sensors/actuators that have demonstrated the ability to withstand the environmental conditions of low Earth orbit (LEO) and are a low-cost option for performing guided-wave testing. The Materials International Space Station Experiment (MISSE) platform onboard the International Space Station (ISS) sets the design specifications of the payload and limits its mass, geometric, and power requirements. The rectangular payload is designed as a layered structure of aluminum plates carrying sensors and electronic hardware. To understand the influence of space environments on the SHM process, ultrasonic guided-wave testing is suggested to infer the variability of the speed of sound in structural materials. A particular payload and sensor layout is proposed to optimize wave transmission for several different guided-wave experiments while still staying within the MISSE based specifications. The anticipated influence of the LEO environment on both the payload and these guided-wave SHM experiments is also considered and modeled. Initial laboratory experiments have demonstrated the detectability of cracks, possibility to infer dispersion characteristics of guided waves, potential to monitor the condition of bolted joints, and strong dependence of the results on the excitation frequency in all of these experiments. The eventual goal of this work is to improve the understanding of the ultrasonic guided-wave response of structural materials in space environments and demonstrate the potential of SHM on the ISS.