Sentence:  For example , the importance of the Regulus 2 , , a very promising aerodynamic ship to surface missile designed to be launched by surfaced submarines , was greatly diminished by the successful acceleration of the much more advanced Polaris <WSD>ballistic</WSD> missile launched by submerged submarines . 
Meaning of the word marked with <WSD> tags:  a missile that is guided in the first part of its flight but falls freely as it approaches target