Launch vehicles are most often propelled using fluids with liquid oxygen being the most common oxidizer and fuel being liquid hydrogen or kerosene and most recently liquid methane. All these fluids (except kerosene) are commonly stored at cryogenic temperatures. Sealing is critical when liquid oxygen or hydrogen are involved since they are easily ignitable.

In order to handle all the fluids used on a launch vehicle such as in the propulsion system, many different type of valves are installed that also require radial and dynamic seals. Some are poppet valves, which are unique due to the reciprocating movement of the shaft leaving the seal unsupported. As a flow control device, the valve allows the flow of pressurized fluid (liquid or gas) in one direction only.

To control the flow of cryogenic propellants such as liquid oxygen, liquid hydrogen or liquid methane on launch vehicles, cryogenic valves are used within these rockets. To meet the industry’s goals of safety and success in these critical fluid control systems, there are requirements set for not only the launch vehicle manufacturer but also the designer of these valves and their components (e.g., sealing solutions).

Several challenging and extreme conditions affect venting components that regulate the flow of propellants in space rockets: 1) cryogenic temperature, 2) frequent movement to adjust the flow of media without lubrication, 3) subject to liquid oxygen (a very harsh chemical component), and 4) significant pressures (beyond 300 bar).