"Dock" is short for "dry dock" so calling it a "space dock" doesn't automatically mean it can't also be a dry dock.
"Dock" is not
short for "drydock." A drydock is a facility where a ship's hull can be raised above the water line (or have water pumped out as per locks) to make the bottom of it easily accessible. A regular dock is simply a place to tie up a ship. A drydock is always for construction, repair, or maintenance, while the regular dock is just for day-to-day operation. (exception... back in the day, ancient Greek Triremes and the like were always hauled out of water onto a drydock to avoid fouling the wood, but that sort of thing hasn't been done in quite a while.)
Having said that, in space, the need for a drydock in the wet navy sense doesn't ... hold water (gah! I'm so sorry, I couldn't help myself!) I would suggest that Star Fleet drydocks as per TMP, TWOK, and Generations, are for the same purposes of our own drydocks today: construction and major repairs and maintenance. Spacedock, could well be just for docking in the usual sense. However, seeing as how there is no wet (and therefore, no need for dry) in space, then I don't see why you couldn't do such work in Spacedock also if that's your bag.
Robert Comsol wrote:
If Earth Spacedock is an inside-turned-out version of Cloud City from Star Wars the sphere at the bottom is most definitely a reactor as the one of Cloud City was also equally positioned down below (probably as a means of protection from possible, hazardous radiation).
I have no specific reason to deny that the spherical area is a reactor (I tend to think so, myself) but I would be careful identifying too many parts based on trying to find corresponding structures on Cloud City, as that is from a totally different franchise in an unrelated universe and served a very different purpose.
All my old issues of Star Trek; The Magazine
are inaccessible just now... but wasn't there a spread on Spacedock in one of those? might add fuel to the fire if nothing else...