US Patent 11939938 Liquid level equalization for propellant tanks

Systems and methods for equalizing fluid levels within a vent line and a propellant tank in which the vent line is located are discussed herein. The vent line includes a vent valve and an equalization valve. The vent valve can be included in a vent duct of the vent line. The equalization valve is included in a bottom wall (i.e., a low point) of the vent duct of the vent line. A controller is also included in the system to instruct a vent valve and the equalization valve to open and close.