I’ve decided that I’m going to use the title “Diving Into the Cracks” as my series of headcanon for various series. It’s probably going to be mostly Star Trek, since that’s what I have most headcanon for, having thought about it for years and years. As usual with headcanon, I’m going to try to not defy actual canon, because the point, or at least my point, is to link the various things I see in canon (and other works, like vidya games) together into a more seamless whole. Star Trek gets the bulk of my attention not only because I’ve been exposed to it since I was a baby, and not only because there’s just so much there, but also because a lot of people who don’t really think too hard about it think it’s very inconsistent, whereas I want to create consistency. And as a part of this series, I’ll give background and explanation as to why I think the way I do, just like the last one. I don’t think most of them will be anywhere near as long as the first, since it’s mostly small things I worry about.
Small things like giant space ships. The Nebula class is that beasty up top there. If you think that looks an awful lot like the Enterprise, that’s because it does. It started life as a kitbash of a normal Enterprise model set for the TNG episode “Best of Both Worlds (Part 2)”. They needed a lot of ships for a scene – a wreckage scene, since a whole fleet of Starfleet ships had been shreked by the Borg. Since there were only so many different kinds of ships that had been made, and since the scene would only be shown for a few moments, and since all the ships would be half-destroyed anyways, this was acceptable. Several other ships were also kitbashes of the Enterprise model – we’ll talk about some of those, too.
Later, the general ship shape was made into the guest-star ship in the episode “The Wounded,” where it was decided that they wanted a spiffy new ship, one that looked like it could be a contemporary of the Enterprise, not one of the old movie ships that the show had been using for the past several seasons. That’s the ship at top, by the way. It’s not just a regular kitbash; even though it uses the same shape as the Enterprise model, the lower section is definitely different. After this, the ship would go on to make several appearances in the various shows, even getting a digital model made for Voyager and DS9 (which was a lot more like the Galaxy-class Enterprise).
Now, the reason I am adding this to the series is that a lot of people assume that it’s an offshoot of the Galaxy class. But I don’t think so, at all. In fact, I think that it’s a precursor to the Galaxy.
The first question, if you think it’s an offshoot of the Galaxy, is why? Why would you have that ship like that? It’s all squished and stuff. “But the pod!” you might exclaim, “that answers everything.” Not really. Why take off the neck, for the pod? And it’s not like they can’t put a pod there, even with the neck – they put another engine nacelle there for the Galaxy: ExTREME Edition, after all.
Also, you have to answer why the ship looks older on the inside. Why does the bridge look so different – so old-fashioned? Why is everything so much tighter? We see three different bridges for this ship, and none of them are the big Galaxy-class bridge.

So, my answer is: the Nebula came before the Galaxy. The bridges are older-fashioned because they are actually older. The neck was added to the general design of the Nebula, not the reverse. The pod was to add functionality to an otherwise somewhat lacking design.
So that’s the simple explanation. Now we get to the more complicated (and fun) headcanon. You see, there were a few Enterprise kit-bashes in that Wolf-359 graveyard. But unlike the Nebula, they were more heavily modified, including changing the window size – and thus, the scale of the saucer and the ship. Here are the kitbashes I’m going to be talking about: the Nebula, the New Orleans, the Cheyenne, and the Springfield. (There’s also the Freedom, but it’s ugly and nonsensical, so I don’t care.) As you can see, there are two different nacelle types – one that looks like a pen with a cap on it, and one with the familiar Galaxy nacelles. So, we can posit that they are of at least two different generations of ships. From here on out, I’m just making things up, based on all of the above.

In the latter part of the 2200’s, there were several smaller powers that were friendly with the Federation. They would have liked to join, but for one problem: the Klingons. At this point in history the Klingons were about equal in power to the Federation, and highly aggressive; indeed, from about the 2250’s on, there was a state of cold war between the two powers, which almost went hot, save for the intervention of godlike beings. These smaller powers didn’t want to get involved in that mess, so they just stayed friendly. Some of them were technologically similar, or even more advanced, than the Federation, but they were small, sometimes involved just with their home system, so they would be devastated if such a war ever came to them.
However, with the signing of the treaty at Khitomer after the explosion of Praxis, things in that corner of the galaxy cooled down significantly. Additionally, advances in warp drive with the advent of the transwarp drive meant that space, at least Federation space, was quite a bit smaller, in practical terms. Those smaller powers would now be relatively safer as a part of the Federation, rather than standing separately.

One of those powers was Trill. The Trill had been friendly with the Federation ever since its founding, but never joined up themselves. They did have a thriving starship design program of their own. One of the hallmarks of Trill ships was modularity: often their ships had interchangeable pieces, or places where they could add on modules.
One of those Trill design companies merged with/was absorbed by one of the Federation’s major design teams, Yoyodyne, when Trill joined the Federation. This was the company that designed the famous Constitution-class ships, along with the Miranda and the Constellation. However, a rival firm had designed the Excelsior, which blindsided Yoyodyne, in that it was better at pretty much everything, and had transwarp drive integrated in the very design. With the new Trill ideas, they hoped to come back into the good graces of Starfleet (prestige being at least as valuable as any currency).
The first two designs weren’t flagship material, but covered the roles of attack cruiser and fleet cruiser – the Cheyenne and Springfield, respectively. The Springfield in particular retained the traditional Trill modularity: it had both a top and bottom pod that could be used for various mission parameters. Starfleet wasn’t too hot on either of these designs, but ordered some of both, since it was a time of experimentation and growth.
After a few decades, the Excelsior was getting a bit long in the tooth. Still quite the capable platform, but it wasn’t quite up to flagship snuff. So Starfleet held its usual trial competition – who would get to design and build the new flagship. In the past couple of decades, there had been another leap in warp engine design, so the old stuff just wouldn’t do. Yoyodyne decided to go with what it new – big, ovoid saucer, with a modular focus. To this end, it developed the Nebula. It was significantly larger than the Excelsior, and much faster. It also didn’t have integral torpedo tubes, as this was an exploration vessel, and a vessel of peace. There was a modular pod that could add on any major functionality necessary (including more weapons if needed). Yoyodyne was so confident in this design, that it created a smaller ship, the New Orleans, as a direct replacement to the Excelsior.

However, Starfleet didn’t chose the Nebula as its new flagship class. It was just too radical a departure from the traditional Starfleet template. The new flagship would be the competing Ambassador class. However, the Nebula was indeed a good design, and was put into basically every other job a ship of its size and versatility could handle. The New Orleans, not so much, since the Excelsior was still a very viable platform. But a few New Orleans ships were still ordered – it was a good ship too, just not necessary.
However, the Ambassador turned out to be a bit of a flop. It didn’t have quite the speed or power – or bite – necessary to keep the Federation safe, what with the increasing aggression of minor hostiles like the Tzenkethi and the Cardassians. Yoyodyne was given another chance – the Nebula was good, but too strange and presumptive. If some of the kinks could be ironed out, it would make a great flagship. And so, with a bit of modification (including more spacious areas and a return to the traditional Starfleet ship form), the Galaxy was born. It was still modular – just on the inside, since any internal part could be swapped out without too much fuss.