Space combat in The Expanse kind of makes sense, assuming that you have magic engines that can accelerate you to something like 5% or 10% of light speed before running out of propellant.

The thing is that space is big. Hundreds of thousands of kilometers is a short range, and 50 km/s is a low speed. Missiles appear slow, because they use the same engine technology as ships, which limits the acceleration they can achieve. Reaching 50 km/s at 50g takes over 100 seconds and is obvious to everyone in the general area. Railgun speeds are inconsistent in the setting, but firing them is also obvious, and random course corrections are an effective defense against them.

Your freighter trick would not have worked. The acceleration would have taken days or even weeks, depending on what kind of acceleration the ship can handle. And it would have been obvious to everyone in the solar system. That would have been plenty of time to send a fleet (that can accelerate faster) to intercept it.

I dunno, surely you would coast out of the system for a year or two. Once out in the Oort cloud, you can drift and turn quietly with your engines away from the solar system and vanish. Then point your engines away (add a glare shield maybe) and nail it inwards. Even if you get so spotted coming from some angle out of the ecliptic no one is going to be able to catch up considering you're coming straight at them rather than a nice stern chase. Accelerating out to meet you head on only makes it worse (though at 50,000km per second, say, you won't be in range for long no matter how far they go).

And even in the books the missiles that killed the Canterbury closed 200,000km in eight minutes. That's nearly 200g and the closing speed would have been 800km/s. They'd go 20 miles in a single frame of the 24fps video of the event.

Even 50km/s is not a low speed if your defensive strategy is a machine gun. You have 1 second to go from a dinner plate sized cross section object at 50km to being dead, and if even if you did hit it with a bullet going say 2km/s the other way, which is a very fast bullet, if it was on target before, the bits will still hit you nearly as effectively. In fact, a better missile would disperse into a spray of fine metal pieces a few 10s of km away and be uninterceptible and cover a wider area in car you can try a dodge.

Seems to me like combat in the universe would be a lot less close-in dogfights and a lot more long range stealth kills by tiny relativistic bullets. And a lot more plausibly deniable "disappearances" in deep space. And I get it, don't get me wrong, rule of cool and all that.

And while we don't have those engines, the approximate same techniques probably apply to any spaceship combat we'll see in the next 100 years. Months of nothing slogging across nothingness then dead in a second out of nowhere. Unless radar really improves and stealth doesn't, I guess.

And surface impacts from deep space will make current ICBM concerns seem quaintly sedate, even if we can't get to relativistic speeds.

The exact numbers in the books are often inconsistent. In Persepolis Rising, the forces that surround the Tempest form a bubble almost three light seconds across. And railgun rounds take less than a minute to reach the center.

My overall impression from the books was that the typical engagement distance is from seconds to tens of seconds at railgun speed (relative to the target), whatever that speed is. Anything beyond that, and random course corrections would make hitting anything with an unguided round effectively impossible, no matter how accurate your weapons are. And if you hit a missile at that distance, the random corrections will probably also get you out of harm's way.

Yeah, and my point is, a guided missile capable of multi-G course correction coming in at tens of km per second is very unlikely to be stopped by a machine gun. And you do hit it with a bullet by a miracle, you'll only do so at a range that's means you're in the debris shower, which is all going multiples of times faster than a shaped charge detonation.

You certainly won't have time to pirouette about firing multiple guns photogenically while a bunch of missiles and the ship are all in one frame.

The missiles seem a lot scarier than the railguns which you actually might be able to dodge given the ranges, as long as you saw the firing happen. Not least because a solid rocket motor actually could do quite a lot of that today.

The debris will likely miss due to the evasive maneuvers both the missile and the target did, and due to the lack of thrust after the destruction of the missile. Plus the standard practice seems to be pointing the main engine (with exhaust velocity measured in percent of light speed) at the approaching missiles. To avoid being vaporized, the missiles must be intentionally trying to miss and then do aggressive last-moment maneuvers once they are close enough to the target.

Agreed. And just to add, the limiting factor is what kind of acceleration the occupants can handle. Even with magic anti-g fluid injectors replacing your blood with marshmallows, it'll still take a long while to get up to 5% or 10% of light speed without turning into goo. Not minutes or hours anyway.

Individual space battles might be measured in years, even in the participant's timeframe.

"So who won that space battle out by Ceres?"

"Dunno, it's only been 3 years."

Surely that just makes it even more lopsided to the guy who gets a missile off before you notice. Even if you can pull 20G before your brain explodes, if the missile does 100G (and even Sprint anti-ballistic-missile missiles in real life did that, in atmosphere, but admittedly not for long, they "only" reached 3.4km/s) then you may as well be standing still. Plus you only really have evasive capability in one axis, you can't leap to the side with any major acceleration in the last 100 milliseconds while the missile covers the last final 5km.

5-10% of light speed won't really change timeframes much (the Lorentz factor is like 0.5% at 0.1c).

If there were a major fight that weren't just a sneak attack and involved fleet on fleet, I imagine it would look like swarms of super fast autonomous missiles rushing in and trying to take each other out faster then you could blink. Any that got through the opposing swarm would proceed to absolutely shred the squishy, slow human containers due to their speed and agility.

We don't have those engines, so it would probably just be a bit like a modern naval engagement would be today: a long range missile fight between ships that have negligible speed relative to the missiles. Except there's no such thing as terminal velocity, the ships are made of tissue paper and your CIWS equivalent has orders of magnitude less time with the target in range.

An interesting missile would be one that catches up to you, latches, and accelerates you to only 20 G or whatever is the minimum to kill you.

Then when your crew is braindead it uses little maneuvering thrusters to spin you around and takes you back to the point of engagement, so your ship/secrets can be salvaged.

I suppose a simple neutron bomb missile would be more efficient for this, and wouldn’t involve a long elliptic trip, so long as it didn’t fry your systems and data storage media.

Edit: I asked ChatGPT and apparently there’s no sci-fi involving a missile that functions to latch and accelerate the target to enough Gs to kill the occupants. Did I invent this just now?

Yes, I think you did! It's a brilliantly diabolical design!

It's not quite the same, but there's a short story by Alastair Reynolds (I think in Galactic North) where a missile forces a ship to run forever, chasing it out of the galaxy as the universe ages around them (I think).