Passive recirculation system for eliminating geysering in liquid oxygen feed system of cryogenic propulsion stage

In cryogenic and semi-cryogenic propulsion stages, liquid oxygen (LOX) is often used as the oxidizer. LOX is supplied to the engine for combustion through stage feedlines. A stagnant column of LOX is likely to be present in some portion of the feedline before engine start. Heat in leak from ambient will cause boiling and bubble formation near the feedline walls. Excessive boiling and bubble formation can lead to geysering in the feedline, resulting in high pressure surges inside feedline components. Geysering in cryogenic feedlines can be avoided by maintaining a continuous downward flow of LOX through the feedline. This paper discusses prevention of geysering in cryogenic feedlines using passive external recirculation based on the thermo-syphon effect.