Re: USS Grandeur - One... More... Time!
One of Enterprise A's torpedos was rigged to track a Bird of Prey's exhaust in STVI. So, at least, some
torpedos had the capability of self propulsion. Also, IIRC K'Ehleyr's transport in "Emissary" (TNG not DS9) was a torpedo tube modified to acheive warp velocity and/or support a being for some length of time.
To strive, to seek, to find, and not to yield.