NASA Goddard Space Flight Center has developed the NOVA zero-leak, permanent isolation valve that helps prevent leaks in space propulsion systems with operating pressures less than or equal to 500 psia. The actuator is made from nitinol, a heat-activated, non-explosive, shape memory alloy and the result is a valve that is much safer than the currently used pyrovalve.
Prior to actuation, the valve allows propellant flow with a pressure drop of <3 psi at a flow rate of 0.15 kg/s. NOVA is actuated by heating a compressed piece of nitinol, which causes it to recover or elongate. This applies a force to the actuator tube that fractures it, initiating a spring that closes the valve, creating a leak-tight seal. NOVA is designed in such a way that the pressurized propellant upstream provides positive pressure on the valve's seal. The valve is compatible with all storable propellants.