Structural Health Monitoring in Near-Space Environment, a High Altitude Balloon Test

The advent of commercial space travel has inspired engineers to rethink design and operation of space transportation systems. Structural health monitoring (SHIM) is seen as a promising technology to reduce time to launch and operation costs with simultaneous improvements in the safety of commercial space vehicles. This technology, however, should be validated in realistic environments. In this contribution, exposure of sensors and measurement hardware to the near-space environment was considered and its effect on SHIM procedures was investigated. The flight profile of the high-altitude balloon included 1 hour and 36 minutes of accent, 57 minutes of float at 102000 ft and approximately 30 minutes of decent. Three SHIM technologies were tested: elastic wave propagation, electro-mechanical impedance, and strain/temperature wireless sensing. The elastic wave propagation experiment consisted of structural sound speed calculation, damage detection, and acoustic emission studies enabled by commercially available hardware. The test was successful, showing variation of sound speed at different stages of the flight and potential to detect structural damage in bolted joint connecting elements of the payload. Acoustic emission activity was also measured. In the second experiment, electro-mechanical impedance of active sensors was measured. However, due to launch delay, only on-the-ground data was collected. The third experiment explored wireless sensing in near-space environment using a commercially available hardware configuration for strain and temperature sensing. Sensor data was collected wirelessly during the high-altitude balloon flight. The study suggests potential of active diagnosis for continuous SHIM of space vehicles and indicates specifics of using off-the-shelf sensor solutions in the near-space environment.