Ultra-light flexible temperature and liquid level sensing probe for cryogenic propellant mass gauging systems

The Cryo-Tracker™, a patent pending, ultra-light, flexible sensing probe for measuring fluid temperature gradients and liquid level has been created for launch vehicle mass gauging systems for cryogenic propellant tanks. The unique one-piece, polyimide mechanically-flexible sensing probe integrates multiple dual-use silicon diode sensing elements within the probe substrate. The Cryo-Tracker has several features including: flexibility, lightweight, high strength, solderless connections, and one-piece construction. The easy-to-install flexible sensing probe measures temperature between 576 °R (320 °K) down to 2.5 °R (1.4 °K). The Cryo-Tracker™ can be integrated into existing standard tank designs or into vehicles that have irregular shaped tank geometries that conform to the aerodynamic shape of the vehicle. The Cryo-Tracker™ probe technology was selected by the NASA 2nd Generation Reusable Launch Vehicle Program to provide accurate stratified propellant mass gauging on future launch vehicles that utilize densified cryogenic propellants. Prototype probes were constructed with one and two sensing elements per probe and tested in liquid nitrogen and liquid oxygen. Several Cryo-Tracker test programs are in progress including a liquid hydrogen test and a high-pressure liquid oxygen test. The objective of this paper is to report test results demonstrating the capabilities of the new probe technology and to provide an update on the current test programs.