Liquid hydrogen in aviation: A critical review of usage and level sensing technologies

In an effort towards sustainable aviation, the use of liquid hydrogen as an energy carrier has the potential to enable zero carbon emission flights. While the idea has been around for decades, challenges in storing and handling liquid hydrogen safely and reliably to meet aviation standards still remain. As liquid hydrogen needs to be stored at − 253 °C, the tank architecture, interfaces and sensors differ greatly from those used for kerosene. Previous studies have investigated and rated certain LH 2 fill level sensors for space applications but no comprehensive evaluation has been conducted regarding their suitability for future commercial aircraft. This paper aims to provide an extensive overview of LH 2 fill level sensor technologies, significantly expanding upon previous research including novel measurement techniques and commenting on the technology readiness level. No fuel level sensor concept excels across all evaluation criteria. Therefore, the authors selected 6 out of the 22 measurement concepts presented in this study to be investigated further in order to advance their respective Technology Readiness Levels.