Electronic safety and arming unit

An electronic safety and arming unit comprises a micro electromechanical system (MEMS) shutter device. The shutter ( 18 ) is suspended by thin lightweight arms and hinges, all formed by silicon processing of SOI substrates and includes holding latches for holding the shutter ( 18 ) in the closed position. The holding latches may be released by an electrothermal actuator. The shutter ( 18 ) separates an initiator section from an explosive train ( 6 ) of munitions such as shells, thereby providing safety until the shell is fired and away from its start point. After firing, the shutter ( 18 ) is opened ready for the main explosive to be detonated by the initiator ( 3 ). The shutter ( 18 ) may be suspended by a compliant displacement multiplier and may include an electrothermal actuator such as an electrically heatable bent beam. Heating of the beam causes movement of a shutter blade from a shut condition covering a firing aperture to an open condition. Alternatively the shutter ( 18 ) may operate by inertial centrifugal forces generated by a spinning munition. The shutter ( 18 ) may include latches for retaining the shutter in its open position.