Abstract: Apparatus for gaging the amount of liquid propellant remaining in a spacecraft (38) tank (1). The tank (1) comprises several preferably V-shaped channels 2A, 2B, 2C, 2D, hereinafter collectively referred to as "2" which communicate liquid propellant from regions within the tank (1) to an outlet port (8) that expels liquid propellant but not pressurant gas. A liquid/bubble chamber assembly (9) couples the channels (2) with the outlet port (8). The channels (2) comprise relatively open portions (11) and relatively closed portions (10). A first ultrasonic transducer (31) is positioned along the outside of the tank (1) and detects a condition of near propellant depletion by measuring the amount of liquid retained in the relatively open portions (11) of the channels (2). The liquid/bubble chamber assembly (9) comprises a liquid trap (27) and a bubble trap (28).

Abstract: A passive propellant management system for a spacecraft liquid propellant tank (1) comprises several preferably V-shaped channels (2) which communicate liquid propellant from regions within the tank (1) to an outlet port (8), which expels liquid propellant but not pressurant gas. A liquid/bubble chamber assembly (9) couples the channels (2) with the outlet port (8). The channels (2) comprise relatively open portions (11) and relatively closed portions (10). In the relatively open portions (11), liquid is retained in a gap (12) between open ends of the V channels (2) and the inner wall of the tank (1). In the relatively closed portions (10), a screen, mesh or perforated plate (14) covers the open end of the V channels (2), intermediate the V channels (2) and the inner wall of the tank (1). The placement of the relatively open and closed portions (11, 10, respectively) is intentionally preselected based upon mission requirements. Where pressurant gas ullage is expected to be present, e.g.