Langasite Cryogenic Pressure Sensor for Space Shuttle Fuel Tank Monitoring

Abstract With the increasing demand for outer space exploration, particularly for NASA missions, the structural safety of space shuttles has garnered significant attention over the past decades. One critical aspect is the external fuel tank, which stores liquid hydrogen and oxygen at cryogenic temperatures of −253°C and −183°C, respectively. Detecting early-stage changes in temperature or pressure is crucial for preventing serious issues in fuel storage or even catastrophic failures in the spacecraft. Accurate and frequent pressure monitoring within the fuel tanks is essential to avoid malfunctions. Langasite (Lanthanum Gallium Silicate, LGS), a piezoelectric material known for its high-temperature stability, also exhibits good piezoelectric properties at cryogenic temperatures. However, there has been limited research on the application of LGS sensors in cryogenic conditions. In this study, we designed and fabricated an LGS bulk acoustic wave (BAW) sensor with an “H”-shaped cross-section, along with a housing suitable for cryogenic pressure sensing. A COMSOL simulation was used to validate the resonant frequency of the LGS BAW sensor. The current housing design is optimized for gas-phase media. The frequency shifts of the LGS BAW sensor were recorded and analyzed using a Vector Network Analyzer, allowing us to relate applied pressure to the frequency changes.