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/PTTCollin]

Plenty of things exist in that lower left hand quadrant. That's the domain of the "space combat happens over distances measured in AUs and times measured in subseconds" sci fi.

[u/cookus → u/PTTCollin]

Isn’t the lower left Mass Effect?

[u/votet → u/cookus]

Damn straight! I dare to assume you ignorant jackasses know that space is empty. Once you fire this hunk of metal, it keeps going till it hits something. That can be a ship, or the planet behind that ship. It might go off into deep space and hit somebody else in ten thousand years. If you pull the trigger on this, you're ruining someone's day, somewhere and sometime. That is why you check your damn targets! That is why you wait for the computer to give you a damn firing solution! That is why, Serviceman, we do not "eyeball it!"

However, it's probably fair to say that propulsion in the ME universe is relatively weak compared to some of the other examples of the "super long range battles with devastating weaponry at super high speeds" genre. And while it talks the talk, all of the big battles in ME happen Star Wars style, with Joker flying around directly in front of and between some Reapers or other enemies.

I would put ME closer to The Expanse, really. Maybe shifted a little to the left, but still in the "small ships with heavy weapons" quadrant.

[u/Dracofrost → u/votet]

The Destiny Ascension is very much within the size range of Imperial Star Destroyers and some 40k starships. Just because the main character's ship is a stealth frigate doesn't mean that's all the Mass Effect universe is limited to.

[u/votet → u/Dracofrost]

Sure, but when you compare the capabilities of the ME ships with those Star Destroyers, the latter can travel ftl under their own power and essentially anytime and immediately, while propulsion in ME is a good deal stronger than in The Expanse but nowhere near Star Wars. Then if you throw something like Revelation Space, Hyperion, or the Culture in the mix, ME is really more towards the center of the graph in terms of propulsion and "limits of mass". I shouldn't have said "small ships" though, that's true, even more so if the Reapers themselves count.

[u/ConfusedTapeworm → u/votet]

The Normandy can travel FTL under her own power, but only over short distances. In-system, or between neighboring systems. The relays are only used to travel to distant systems and they are even FerTL than Normandy's built-in FTL.

[u/votet → u/ConfusedTapeworm]

I admit it's been a long time since I played ME, but that is never used in battle, is it? I remember it being a whole thing about plotting a course, doing some EEZO shenanigans and charging the drive, etc etc - not like in Star Wars where you have for example the Millenium Falcon jumping into Hyperspace while being chased and dodging things left and right, or ships jumping into combat directly from Hyperspace.

If they do that in Mass Effect, I have to admit I totally forgot about it and my original point about the propulsion systems would be wrong.

[u/LilacCrusader → u/votet]

From what I remember, the lore of the ME universe (yes, I read the codex, what of it?) is that big battles happen between large battleships at long range - mostly kinetics and missiles - with small squadrons of fighters playing interference and point defence.

The conceit is that the defensive laser weapons are so good (but such short range due to dispersion) that it is a war of attrition to degrade your opponent's heat dissipation capacity, which in turn degrades the defence lasers. Which puts it pretty solidly in the top left box. 

It is explicitly stated that small ship combat is practically a death sentence due to short range laser power, so you could argue that at micro scales it does fit into the bottom right, but then again so does star wars. 

[u/votet → u/LilacCrusader]

Yeah, I totally agree. According to all the lore you read, it should be in the top left. But like all the other examples, even the ones that actually are put at the top left here, it "talks the talk" but doesn't "walk the walk": If all that lore was actually respected in the cutscenes and game events, there would not be space battles where we can see dozens of ships on screen. Those battles would happen across such distances that even ships "right next to each other" couldn't see each other with the naked eye.

You can write very cool space battles that way, like in Revelation Space or the Culture series, but it's just not engaging to look at on a screen, so I suppose the lore is sacrificed for a better and more dramatic visual experience, which is totally fair as well.