Screen channel LAD bubble point tests in liquid hydrogen

• We present a metric for gauging the performance of screen channel LADs.
• The bubble point pressure increases with decreasing liquid temperature.
• The LAD screen pore itself is temperature dependent.
• Noncondensible gases cause evaporation at the screen and thus increase performance.
• Autogenous gases promote condensation and thus decrease performance.

This paper presents experimental results for the liquid hydrogen bubble point tests for liquid acquisition devices (LADs) operating in low gravity cryogenic propulsion systems. The purpose of the test was to investigate parameters that affect screen channel LAD performance in a low pressure liquid hydrogen (LH2) propellant tank and to demonstrate several ways to increase the LH2 bubble point pressure. Three fine mesh screen channel LAD samples were tested in LH2 over the range of 16.7 K < T < 21.1 K and 31.5 kPa < P < 155 kPa using gaseous helium and hydrogen as pressurant gases. Results show that bubble point pressure is affected by screen mesh type, liquid temperature and pressure, and type of pressurization gas. Higher bubble points are achieved by using a finer mesh screen and pressurizing and subcooling the liquid with gaseous helium. In addition, there is evidence that the screen pore is itself temperature dependent.