Abstract: A self-contained supplemental guidance module for use with projectile weapons having a connected body and payload in attachable to the weapon between the body and payload, and includes self-contained power supply, inertial sensors and a plurality of incremental charges angularly spaced around an outer periphery of the module. A control processor in the module is operable responsive to the position of the module as detected by the sensors to calculate deviation of the projectile from a nominal flight path, taking gravity into account, and to detonate individual incremental charges when deviation exceeds a threshold and the incremental charge is in position to reduce the deviation. The supplemental guidance module is particularly applicable to barrage rockets, and includes a multi-level safe-and-arm apparatus initiating operation with sufficient axial thrust and disabling operation in the event of loss of sensor signals.