Distributed Leak Detection System Using Structure-Borne Noise

Manned spacecraft are vulnerable to air leaks caused by micrometeorite and space debris impact. The ability to detect and quickly locate and mitigate a pressure vessel breach is critical to the safety of any long duration spacecraft, such as the International Space Station or a proposed lunar base or mission to Mars. Current NASA protocol for finding a spacecraft leak uses a handheld ultrasonic directional microphone, similar to those widely deployed industrially, to detect the 40 kHz airborne ultrasonic hiss generated by the downstream leak turbulence. However, known limitations exist regarding the use of airborne ultrasonic emissions for locating leaks in the spacecraft environment because the downstream side of the leak occurs into the vacuum of space, creating reduced leak noise inside the pressure vessel. Blockages of the transmission of airborne ultrasonic energy by structural components, avionics, and equipment racks also limit the detection range of such systems. An alternative approach that we propose is to monitor the spacecraft structure itself---the pressure vessel skin---for leak-generated surface-borne ultrasound by means of a flexible and modular electronics package with fully integrated surface sensor arrays, data acquisition electronics, and radio frequency communication capabilities.