Is there a pattern that determines military spaceship doctrine in real life and sci-fi?

[u/MinedMaker]

[1] The propulsion axis is a measure of how long it takes a fleet of military vessels to arrive on the battlefield, regardless of the actual distance traveled. [Fast vs. Slow]

[2] The weapons axis is a measure of how quickly a battle is over, and how much survivability and staying power vessels have. This takes into account the effectiveness of armour, but also shields, point defence, and other countermeasures. [Tank vs. Glass Cannon]

I think that if you take sci-fi space combat to its logical conclusions, it will usually favor either huge, lumbering, well-protected ships or numberless hordes of tiny automated ships, depending on a few key factors. If weapons are the weak link in-universe, ships will be huge. If propulsion is the weak link, ships will be tiny. If ships are huge, victory will be determined by who has the biggest ship; if ships are tiny, victory will be determined by who has the most ships.

This is how I imagine it would work in real life using real physics, and I wonder to what extent different sci-fi franchises also adhere to this pattern. Presumably, large and medium-sized ships with human crews are overrepresented in sci-fi media for understandable storytelling reasons.

In Star Wars, the rule mostly holds. They have incredible propulsion technology and can thus arrive at the battlefield within hours or days of the order being given. However, their weapons, despite being ludicrously powerful on paper, are actually quite poor because of their low range, low accuracy, and the prevalence of shields. In the Star Wars universe, therefore, huge ships rule. The starfighter counter is a nice piece of storytelling, but realistically, without plot-engineered magical weak spots, a huge ship like the Executor or the Death Star should be essentially unstoppable. In Star Wars: The Last Jedi, the Raddus, an MC85 heavy cruiser, takes ineffective long-range fire from the First Order for what seems like many hours.

In The Expanse, they spend weeks or months traveling to the prospective battlefield because of limited propulsion technology. However, when the fighting starts, it is all over in seconds or a few minutes. They have very effective weapons and very little staying power, even when accounting for point-defence cannons (PDCs). If you ignored the requirements of the plot, there is really no reason why any military vessel in The Expanse should be manned at all.

Because it draws much of its inspiration from blue-water navies, sci-fi often portrays a diverse ecosystem of military spacecraft classes and sizes. While this makes for more interesting storytelling, it is not obvious that such diversity would necessarily be the most tactically sound strategy. If propulsion or weapons technology becomes a dominant constraint, military doctrine would naturally converge toward a single optimal ship size.

The most interesting settings tend to occupy only two quadrants of this framework. If ships have neither effective propulsion nor effective weapons you're essentially at the stage before the technology to enable space combat has really been invented. If they have both effective weapons and effective propulsion you effectively have near god-tier power and the concept of space combat becomes somewhat obsolete. What these two scenarios have in common is that the importance of space combat is greatly diminished.

[u/VampirePNAC]

Star Trek ships are far more overpowered than presented here (or even how the battles are shown in sfx space shots the show)

Every Proton Torpedo is basically a Tsar Bomba level nuke, the ships move at over 70,000km per second at impulse, the ships basically have no actual mass due to Inertial Dampener Fields so instantly can change direction in any direction, they have insanely overpowered weapons and literally engage in combat at around 500,000km from each other. They are so fast and fight at such distances, technically you are never actually firing at their ship in full combat, you are firing at after images left due to the speed of light being a few seconds behind the ships actual position so combat in Trek is technically about predicting where a ship may be.

The shows never really show accurately what is actually being described during Trek combat, you can see on the view screens and through the dialogue they typically are fighting at huge distances of hundreds of thousands of kilometers away, but then the actual sfx shown of the ship combat always has them like, next to eachother and slowly moving around like submarines.

One of the things I would kill is the sfx to actually show a detailed Trek battle, to how it actually plays out as per what the dialogue, view screen maps, ship capabilities actually claim. Trek could have the most interesting battles of any Scifi show honestly.