loads the rear end of the outer tube 15 is locally thickened and internally threaded to receive an externally threaded nozzle plate 17 see fig3 also of high strength aluminium alloy and which has two series of sixteen nozzle holes 18 on two pitch circle diameters alternate nozzles 18 39 on the outer pitch circle diameter are canted to impart a clockwise spin to the missile as viewed from the rear the throats of the nozzle holes 18 may be treated or fitted with metal inserts to resist erosion the nozzle plate 17 also includes a central aperture 19 having an annular lip 19 39 which protrudes into the efflux of the main missile motor 11 when ignited the aperture 19 is internally threaded to receive the externally threaded rear end of the inner hollow cylindrical tube 20 of the expulsion motor referring now in particular to fig2 the forward end of the inner tube 20 passes through an aperture in the front end of the outer tube 15 and is externally threaded to engage an internally threaded locking ring 21 which locks the inner tube 20 to the outer tube 15 which is bottled over as shown an annular collar 22 is secured to the outside of the locking ring by screws passing through the collar 22 into the locking ring the forward surface of the collar 22 is castellated to provide four lugs 23 the missile is provided with a complementarily castellated collar 24 so that the torque induced by the canted nozzles 18 39 may be transferred from the expulsion motor casing to the missile body the expulsion motor includes a propellant charge 25 and associated igniter 26 located between the.