I rather like Cary's idea that the Spacedock was "grown" over time. But the size of the station and its siblings is what bothers me. From the outside window arrangement (if that is what the lighted panels are), it looks like Spacedock is built like a skyscraper, with level stacked upon level. Why would you need such a dense facility merely for people to work in when Earth -- which is a paradise, supposedly -- is right below? That's why I started thinking about Spacedock as mostly hollow, with giant fabrication facilities for starships inside. The windowed offices we see on its surface then would occupy only a thin layer of skin, which still means a vast number of people could work there, but not a ridiculous, Manhattan-sized number.
But maybe my imagination is failing me.
Best,
--MyClone
I don't think your imagination is failing you... at least not exactly.
Here's "Spacedock" as seen on-screen.
I suspect that the first section built was the bottom-most section, the sphere... and that section was built as a big spaceborne environment... basically, I see this as a hollow shell with an "artificial sky" and so forth. Probably built a very long time ago, during the reconstruction.
Next, the middle "mushroom cap" section was added. We know that this is a dock section, because in ST-VI we see four underside-mounted spacedoors around the rim. It's probably a smaller space-borne construction yard, capable of handling smaller-scale vessels. But for the really big stuff (1701-ish ships), it would've been way too small.
Now, in between the "yard" and the "habitat sphere" I imagine it was originally just a lot of trusswork, tankage, etc... very industrial-looking. Not the smooth, cylindrical look we eventually have in that region. And I suspect that the "yard" was cruder initially.
I suspect that "the yard" was already underway, if not already in existence, at the time of the NX-01, albeit in a much cruder (and probably nearly unrecognizable) form.
The big problem was that with larger vessels being constructed, the spaceborne facilities couldn't handle anything that big... and thus the big components had to be constructed planetside and be lifted into orbit (not all THAT big of a deal, construction-wise, but a MAJOR issue in terms of transit time... sort of like making parts of a device in China, shipping it to Akron, then shipping it to Germany, then back to Akron again... not technologically challenging, just not the most efficient route).
SO... they created another section... the Spacedock complex... on top of the existing Starbase One structure, providing an otherwise essentially unobtainable environment... microgravity combined with a breathable atmosphere, capable of holding some really BIG ships not only in segments but in fact COMPLETE.
The thing to realize about construction is that it's almost never done entirely at one site. Bits and pieces are made in various locations, shipped to another, reworked or combined or whatever, then shipped to yet another location, and so on and so on.
So, for assembly of components into a full structure, you'd want a framework to wrap around the ship to hold the various parts in place while they're bolted to each other... something like the drydock seen in TMP.
For fine work... paint and polish, really... you'd want it done inside of the pressurized "Spacedock" facility. Which, of course, is what we see in ST-IV (remember seeing the little guy on top finishing the painting of the hull lettering?)
You might also do certain types of heat-treatments in there... things that the excessively-quick heat loss seen in a vacuum wouldn't be conducive towards. In other words, maybe you can weld in a vacuum, but unless you can anneal afterwards, you'd have brittle weldments... totally unacceptable!
Meanwhile, you'd probably still have big chunks of the ship constructed elsewhere and shipped in. I'm one of those people who likes the idea that the engine nacelles are manufactured elsewhere and shipped in for final assembly (just like is done for modern aircraft engines). Some of that (maybe most of it in some cases?) might be constructed in various other areas of Starbase One... or at San Francisco Naval Yards... or Utopia Planetia Naval Yards on Mars (or in orbit above Mars) or on Andor or anyplace else!
The trick for everyone to remember when thinking "starship construction" is that "all in one location" is a bad assumption to make. It's waaaay too complex... and each step would be done wherever it was most efficient to do.