1. A HYDRODYNAMIC ACCELERATOR COMPRISING A LINEAR TUBE OPEN AT BOTH ENDS, A FRACTURABLE TRANSVERSE WALL DISPOSED ACROSS THE TUBE INWARD OF A FIRST END OF THE TUBE, AN EXPLOSIVE CHARGE ADJACENT TO SAID TRANSVERSE WALL, AN ELECTRICAL CIRCUIT INCLUDING A CURRENT SOURCE AND A MAGNETICALLY-OPERABLE SWITCH DISPOSED IN THE TUBE AND CONNECTED TO THE EXPLOSIVE CHARGE, A MAGNET POSITIONED EXTERNALLY ON THE TUBE ADJACENT TO THE SWITCH, A MAGNETIC KEEPER REMOVABLY POSITIONED ADJACENT THE MAGNET, MEANS FOR REMOVING THE KEEPER FROM THE MAGNET, AND A CLOSURE FOR THE SECOND OF THE TUBE.