Skip Navigation


Cryogenic Fluid Management

Propellant tanks in spacecraft contain cryogens such as oxygen and hydrogen; in all cryogenic storage tanks liquid and vapor coexist in equilibrium. On earth liquid acquisition is straightforward since gravity causes the liquid and vapor to separate and draws the heavier liquid to the bottom of the tank. However, in the weightless environment of space in that there is no "up" or "down" that can tell an engineer the location of the liquid and the vapor with certainty. This presents an engineering challenge because, in order to fire, the rocket must be fed liquid not vapor or a mixture of liquid and vapor.

Liquid acquisition devices (LADs) are the response to this problem. They consist of a channel with rectangular cross section one of whose sides is a porous screen. By placing the channel so that the screen closely faces the tank wall, the LAD will uptake liquid even in zero gravity.

USRA scientists at the National Center for Space Exploration Research (now known as Advanced Research Associates) support several aspects of cryogenic fluid management, spanning from liquid acquisition device (LAD) design, testing and building, to cryogen transfer from a feeding to a receiving tank, to pressure control strategies during tank filling, and mass gauging. Capabilities required in these activities range from expertise in capillary flows and capillary phenomena, to applied mathematics, numerical analysis and asymptotic analysis, to fluid mechanics, heat transfer and thermodynamics.