That is the bridge.
And the “bump” on the bottom is the dome for a sensor array.
The shape of the saucer is determined by the functions (and hence sizes) of the various decks (e.g., science labs, crew quarters, bulk storage). This is why it’s narrow at the top, wide in the middle, and narrow again at the bottom, like a brontosaurus.
Perhaps they could throw some lobster pots over the side, too. What kind of wine goes with shellfish? 
Perhaps they can drink a lot of Cæsars.
Q: Does Earth have a flying Eleanor Roosevelt…?
…
It’s too bad that château Picard only produces red wines.
Ah. The airlocks were what I was missing.
And, yes, the NX-01 definitely has airlocks, due to actually having people board without transporters. I also know the Enterprise-D has a hangar that can be pressurized or depressurized, letting you use some bigger rocks. I’m not sure about Kirk’s Enterprise. I know it has shuttles, but not whether the shuttlebay can be pressurized. Probably they can be, since you rarely see anyone in environment suits.
Then again, I’m not sure the pressurization part matters, assuming you do have a way to get the rocks in there. Maybe just fly around the big rocks, almost matching velocity.
Also, it is not clear what the structure and hull are composed of, but it is certain that it is some fucking sturdy material. There is quite a bit of air inside, but there is a non-trivial amount of not-air, of unknown density. The idea that NX-01 would float on the sea is fanciful and weakly founded. In addition, the propulsion systems are designed for moving through a medium that is orders of magnitude less dense that water, or even air. If the Enterprise did in fact float, I would not expect it to move very quickly, if much at all.
Yes, it could be pressurized. This was mentioned during the series, and I believe there was a pressurization status panel mounted somewhere as well.
In TMP for sure, Kirk et al. were shown emerging from an airlock on the top of the saucer.
Not sure that NX-01 had airlocks, as such. As I recall, the shuttlepods dock to ports, so that works out to just door-to-door link-up. There was one episode where Tripp was climbing a cable between two ships at warp speed, going directly out of the ship, so I think they just used some kind of force field to hold the air in. Why use an airlock when you can use a force field to do it more easily?
NCC 1701 had a shuttlecraft bay at the back, and you see it get used in several episodes. With its big round doors, using a force field to hold in the air is somewhat more problematic. On the other hand, the Star Treks were never very beholden to realistic science (I liked Enterprise best because it seems a little more realistic).
My level 10 fanwank says it will create explosive steam and that will be very bad for the ship. 40 cubic acres under the ship will instantly turn to steam. Bad!
Unless you’re over that bed of clams dude robert mentioned.
I always assumed “impulse drive” was reactionless, based on gravitational manipulation. (If you have artificial gravity, it doesn’t take much to turn it into reactionless drive.)
That said, it also wouldn’t be too hard to weaponize tractor/presser beams. Remember the TOS episode where the tractor beams broke up a 1970’s jet aircraft.
That was always my impression as well, at least with NCC 1701. However, NX-01 was a less advanced beast, so it might have used some other type of sub-light drive.
dude specifically focuses on NX-01, which was not equipped with a tractor beam (unless one might have been bolted on shortly before it was decommissioned). The tractor beam emanated from the big dish on the lower hull section, so that, again, would be under water. That could be almost as messy as boiling the sea with a phase cannon.
The airlocks I’m referring to are the ones used to enter the ship in general, since they originally didn’t beam on. They would also be the decontamination chambers (or contain them). Otherwise the atmosphere would mix with the ship atmosphere, defeating the purpose.
I’m also not sure they had forcefield tech, since they didn’t have shields. And I would consider the force fields with recompression to be airlocks. They just use force fields instead of doors.
Maybe I use the words differently.
It’s my understanding that the tractor beam unit on 1701 was mounted on a retractable strut at the bottom of the secondary hull, right where the ship would rest if you could set it on a planet. There are stills that show the circular port from which it was lowered, outlined in red.
I’d have to see the remastered versions of “Space Seed” and “Doomsday Machine” to see what they did with this.
(Of course, they used the Bussard collectors as tractors or deflectors in TNG, so I suppose anything was possible on 1701-D. The primary use of the main dish, however, was always a navigational sensor and deflector.)
As regards the impulse drive, the schematic of 1701-D showed a big “fuel tank” in the spine of the secondary hull, right where it met the main access pylon and immediately below the impulse engines. It was connected to the engines by some sort of vertical shaft. (I believe deuterium was mentioned somewhere as the “fuel” they used.)
I think Geordie once said they could run for a month on impulse before they ran out of “fuel,” so it must have been one helluvan efficient engine, given the size of the “tank.”
In this schematic of 1701, you can see the main tractor beam, extended below the secondary hull.
Ok, yeah, that is from the paper blueprint set that was sold in the '70s. And it makes sense, because, if you have to tow, you have to be able to aim backward. But it does not help NX-01, which did not have a tractor beam generator, unless it was bolted on, in which case, it would be on the ventral knuckle between the nacelles.
There is no practical way to direct the tractor beam upward, where ships would be. The best you could do is try to snap off a small island to fling around like a big mace.