Guided Missiles For Britain's Defence -- A British Guided Rocket taking off. It is being boosted up to its cruising speed by the motors attached to its sides. After a few seconds these boost motors drop off and the missile itself continues on, driven by its own sustainer motor.Likely to be the mainstay of Britain's future defences are guided missiles, travelling at well over 2,000 mph, to heights far greater than that attainable by any bomber. They will be able to jettison their rocket booster a