Has anyone ever wondered if perhaps the large interior cavity of Earth's giant spacedock had a substantial atmosphere contained within? Evidence for this:

1. The spacedock spotlights, have a noticeable dispersion of the light in their beams. (although it is not as noticeable in TSFS). The fact that you can make them out as beams at all suggests some medium through which the light must pass, but these beams seem to be passing through a relatively dense atmospheric medium. I suspect this was done to augment the sense of scale inside the model.

2. The simple fact that the entire (and substantially huge) structure is an enclosed one (unlike say, dry-dock or McKinley station) with huge exterior doors that open and close. These doors are the only means of access or egress for the coming and going starships. Maybe the doors or their surrounding frame members house some type of force field technology that prevents the escape of atmospheric gases.

We have known since at least The Motion Picture, that Starfleet has had some form of forcefield technology that allows large cavernous spaces to maintain atmosphere, even when exposed to the vacuum of space. In TMP the refit Enterprise in dry-dock had its landing bay doors open to space while workbees with cargo sleds entered from outside the ship, and crew members walked freely about the interior without the aid of environmental suits. If the case were the same for spacedock, it would be beneficial in that starship maintenance and repair could be carried out with more ease, comfort and efficiency; no bulky space suits.

The only problem I might foresee with this scenario would be possible radiation contamination from the ships themselves. Who knows what kind of radiation hazards might arise from a ship's exhaust systems or plain and simple leaks. Something tells me that there would be contingencies for these problems though.

So is it just me or is it reasonable to think that the spacedock mushroom might have a breathable interior space. Your thoughts....

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It doesn't matter if you don't know what you're doing as long as you look good doing it.

That is, the enclosed environment is desirable for a reason other than creating a breathable atmosphere (but we don't know the reason) and a toxic or at least unbreathable atmosphere results from the fact that starships are operating in this enclosed environment. No forcefield is applied over the big doors, but the existence of the doors themselves is sufficient to retain a light-scattering atmosphere inside the dock area, even if the area is vented to space every now and then.

fructose1: I too had thought about the thruster only rule, but I didn't know if it was related to possible exhaust hazards or if they simply didn't want ships barreling out of spacedock so fast they take half the super structure with them.

Timo: This is exactly the kind of counter-thought I wanted and it makes sense. Maybe that is why the spotlights are less "beam" like in TSFS, and much more noticeable in STIV and VI. Higher traffic means more emissions. However it still does not explain why the structure is even enclosed in the first place. Dry-docks, McKinley station, and DS9 were all dockable without having such elaborate and complete enclosures. Having such a huge closed off environment without any other obvious purpose screams wasteful and extraneous to me.
Your thoughts...

I think the "atmospheric haze" is just an attempt to give a sense of scale. They probably also provide atmospheric haze even for scenes in space.

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When you're in the Sol system, come visit the Starfleet Museum

The structure should date back at least to the birth of the Federation, or parts of it should at least. Then we could assume that the enclosed environment was created in order to protect the ships inside from things like thermal stresses, micrometeoroid (mainly lost nuts, bolts and spanners) bombardment and radiation while they are being services.

Modern starships are of course impervious to mere thermal stresses, and the enclosing is currently more of a hindrance than an asset. In case your starbase is attacked, you don't want to protect the ships inside. You want to deploy them as soon as possible, so that they are of some use to you. Having them emerge from a few cramped doors makes them sitting ducks for the attacker.

This idea of the Spacedock being an old structure has an obvious weakness: we know of at least three big deep-space starbases that share the shape if not the size. Supposedly these are newer than the Earth Spacedock. But perhaps the increased size of the stations and thus of the exit doors negates some of the problems. And perhaps the environment near these stations poses some special risks even to modern starships, against which enclosing is needed.

Anyway, I also think they just did the beam of light for effect, not thinking that we would start theorizing about the scientific background.

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RIMMER [as Ace]: "Stoke me a clipper, I'll be back for Christmas."

I suppose a version of the SIF field mentioned in TNGTM could account for this better than pressurizing the interior volume, but I think its still a valid point.

As to atmosphere. The waste gas idea seems the most plausible and not all that harmful since star ships moving in and out would expel very little in the way of gasses that could easily be filtered out.

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[Bart's looking for his dog.]
Groundskeeper Willy: Yeah, I bought your mutt - and I 'ate 'im! [Bart gasps.] I 'ate 'is little face, I 'ate 'is guts, and I 'ate the way 'e's always barkin'! So I gave 'im to the church.
Bart: Ohhh, I see... you HATE him, so you gave him to the church.
Groundskeeper Willy: Aye. I also 'ate the mess he left on me rug. [Bart stares.] Ya heard me!

If Spacedock is primarily an "airport in orbit", a facility only designed to handle the "passenger interface" of starships, then the enclosed nature could be simple aesthetics. Perhaps the facility is civilian, even, with Starfleet just operating a pier or two? The structure could be Earth's primary spaceport, and would mostly handle passenger liners and the like.

This would also help explain why Kirk and pals flew a "civilian" shuttle (no Starfleet markings, but instead a UFP logo plus a NAR registry) to the station in ST6. They simply took the "regular" transportation instead of the "military" one, perhaps because Starfleet prefers to give its personnel vouchers to civilian flights instead of maintaining a dedicated passenger shuttle that has few military uses (the "Generations" rescue being one of the few).

And since some civilian passengers prefer old-fashioned shuttles to transporters, the shuttles are kept as a sales gimmick. Or then public transporters back in the days of ST6 simply weren't all that good, and shuttles were the preferred means of transportation of medium to large groups of people, unless there was an emergency.

Timo Saloniemi