A closed/semi-open pressure or vacuum system uses an electric screw mechanical actuator that can be digitally controlled and monitored, and which receives feedback directly from an external or internal source. This innovation can adjust for media temperature changes, expansion, and contraction in a constant volume and pressure system. This is done by extending or retracting a leak-free, high-pressure, or vacuum-sealed piston that is controlling pressure or vacuum.

This system has the capability to maintain a precise pressure or vacuum. The system can recharge itself by movement of the piston to a centering position to account for system small pressure changes either up or down. By this method, this system is able to calculate the total mass changes that are in the system at any time. This unit assembly consists of a screw actuator and a hydraulic piston or other pressure developing device, and a controlling computer.

This work was done by Mark Stevens of Johnson Space Center. MSC-24825-1