Chandrayaan-2 lander propulsion system employs a bipropellant thruster with a throttleable flow control valve (TCV) to vary the thrust produced by 800 N engines. A latching solenoid valve was proposed downstream of TCV to precisely admit/cut-off propellant supply to the engine as the latter does not inherently possess stringent leak tightness characteristics. The proposed valve employs a flexure guided plunger assembly to facilitate both continuous and pulse mode operation of the engine while preventing the possibility of cold welding/stiction between the sliding parts under space environment. A latching type of solenoid configuration was selected with balanced loading and permanent magnets to complement the solenoid in reducing the mass when compared to a conventional solenoid valve for the same application. In the selected configuration, switching of the valve position is accomplished by energising the solenoid coil and latching in the commanded position with the help of permanent magnets. Thus, the solenoid valve does not require continuous external supply, which results in negligible coil heating and very low power consumption. Two sets of proto models were realised which had undergone performance tests, 10,000 cycles of operation and 100 s duration hot test satisfactorily.
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