Flow rate measurements for cryogenic propellants are required for spacecraft and space exploration systems. Such a requirement has been hampered by lack of fast and accurate instruments among existing technologies. This proposed project will develop a mass flow measurement system for non-conducting cryogenic propellant flow to meet the NASA's need. In the proposed system, an electromagnetic flowmeter for insulating fluids (EMFIF) will be able to provide real-time liquid velocity information under single- and two-phase flow conditions, and an X-ray void fraction sensor will provide phase concentration and interfacial velocity information. The X-ray sensor will also be able to detect bubble existence in cryogenic propellant flow. The whole proposed system will be a useful instrument to measure propellant flowrate in rocket engine feed lines. During the Phase I project, a test model of the proposal measurement technique will be designed and built. The performance of the proposed flowmeter will be studied in an experimental cross-calibration. If the Phase I study shows that it is feasible to employ the flowmeter for single/two-phase flow, the Phase II development towards engineering design and verification of the system will be carried out.