Dimensioning and design of direct controlled solenoid actuators in cryogenic Ariane 5 valves

In the Ariane 5 launcher several cryogenic valve actuation units are required, e.g. the helium supply system and the tank pressurization system. The technical specifications demand for fast acting actuators under various constraints such as temperature conditions, low mass, minimum power demand and reliability; the temperatures range from about 420 K over ambient to cryogenic, liquid hydrogen (20 K) or liquid helium (2.8 K). These requirements are met by the design of direct controlled solenoid actuators. The development of the actual design and layout is backed computationally and verified by tests. Modeling of the (electro-)magnetic circuit including permanent magnet, solenoids and several air gaps is needed for design purposes in order to yield sufficient force margins for the operation of the actuator