Abstract: Solid propellant combustion apparatus such as a rocket motor, incorporating a combustion termination valve for providing two combustion phases from a single propellant charge system, the valve comprising a valve body (50) surrounding an opening (52) in the pressure vessel of the combustion apparatus, a valve member (60), retaining means (65) for releasably retaining said valve member in sealing engagement with the valve body whereby to hold the valve closed during a first combustion phase, valve opening means (68) operable on command for releasing said retaining means whereby to cause the valve member (61) to disengage from the valve body thereby opening the valve to terminate said first combustion phase by rapid de-pressurisation of the combustion gases through said opening, and valve closure means (72) operable on command to move the valve member (61) into sealing engagement with the valve body whereby to close the valve prior to re-ignition of the propellant charge for a second combustion phase.