So, I’m writing sci-fi and I want to know about weapon ranges when it comes to space ships/station, or land to space missiles. What is possible, or if isn’t actually possible/we don’t know, what makes sense, especially when it comes to max ranges or accuracy/effective range. Also, would there be a such thing as sniping extremely long distances like idk 50 million km?? But the problem would still be speed and take too long to actually reach?
Something a lot of sci-fi genuinely screws up (for entirely artistic reasons) is engagement ranges. If you have a beam weapon which travels at the speed of light, a 50 million kilometer range will only take about a 6th of a second to hit the target. If that target is ship sized, you can connect with the target at that range, unless that ship can move at incredibly high speeds, with almost impossibly high reaction speeds, assuming it can also detect the beam before impact, which is kind of an issue when you consider that baring some kind of quantum physics mess any information that ship has regarding a hostile ship firing on it will be at least a sixth of a second out of date.
So, when you’re talking about these ranges, you’re talking about travel time for a beam weapon that is roughly equivalent to firing a pistol at someone in the same room.
Take that same beam weapon, and fire a range of an astronomical unit, and you’re still only looking at about eight minutes of travel time. If your targeting is good, that’s more than enough time to hit all but the most nimble of ships,
There is a problem with extreme range and beam weapons. A laser is just an extremely focused beam of light. This appears to remain as a tight dot at the destination, but that’s because you’re not using a laser at ranges where the angle of the beam becomes apparent. It’s not (strictly) a cylinder of light, it’s a cone. When you’re pushing a laser to thousands (or hundreds of thousands) of kilometers, this starts to become very apparent. This is not an unsolvable issue from a technological standpoint, a tighter cone, a true cylinder, or the cone as a payload for something else (such as high energy particles of some variety), all potentially expand the maximum range a beam weapon significantly. So, I’m not going to dig into the idea of extrasolar beam weapons, it’s still distinctly possible.
Parallel you have kinetic delivery systems. This is basically just a gun in space. It may be a rail gun, or it could be a classic propellent that gets it moving. Now, here’s the problem with bullets in space: There’s nothing to stop them.
On Earth, a 5.56mm NATO round has a rough maximum range of ~600m, and it’s effective range is only ~300 meters. Take that exact same bullet, put it in space, and it’s maximum range is infinite. It will continue to travel until it hits something or is pulled into a gravity well. There is no friction from the atmosphere to slow it down, so it will continue traveling at its original velocity (roughly 1km/s) until the heat death of the universe. (It will probably hit something before then. But, there a real possibility that this bullet would spend tens or hundreds of millions of years traveling through space before it connected with anything. To be fair, I think it would take that bullet about 1.3 million years to reach Alpha Centauri at that speed, though my math could be a bit off there. I’m using rounded numbers at a point where those rounding errors result in differences of hundreds of thousands of years.)
Sci-fi loves to put ships in close proximity to one another. Films and TV love to get the hero and villain ships in the same frame, and have them bouncing around for your amusement. As artistic license, this is fine, but you’re looking at ships where the engagement ranges should be well beyond visual range. In a science fiction shooting war, your ships should never even see each other. They should be fighting over radar/lidar signals. (Incidentally, this is also a problem with jet fighter dogfighting in films and TV. When you’re looking at a plane going over 343m/s, fighting another plane at similar speeds, you’re simply not going to be close enough to see each other for any length of time.)
Parallel to this, guided missiles are as accurate and fast as the technology allows. When it comes to missile sniping, with an FTL capable civilization, we’re potentially talking about firing from a different solar system. A simple rocket engine with an explosive payload traveling at a lower speed than a bullet isn’t going to be useful for much. However, guided projectiles, and anything that travels at relativistic speeds is going to start to explode maximum ranges in a very real way.
The same thing is true for planetary bombardment. Launching kinetic projectiles at relativistic speeds means you can be outside the solar system if you’re patient enough. Planets, as a rule, aren’t particularly good at dodging incoming projectiles, and you can use math to have a pretty good idea of exactly where it will be twenty years from now. The frightening thing about orbital bombardment is, you don’t actually need to be in orbit, or even in the stellar gravity well. If you’re targeting a rocky terrestrial world inside The Goldilocks Zone, it gets worse, because the star’s gravity well will assist in accelerating the projectiles as they get closer. It will also distort aiming, but this is in incredibly predictable ways, that anyone with a functional grasp of physics and a calculator can adjust for.
When it comes to naval warfare in space, 50m km isn’t really long distance. That’s pretty close to one another.
When you’re writing combat in space, it’s important to set the technological limitations of your ships and setting. This is why I’m somewhat permissive of settings which put ships within a few kilometers of each other, and have them engage at those ranges, when it doesn’t really make a lot of sense. Maybe your world’s beam weapons are only effective to 10km, and your ECM have enough time to disable missiles fired from more than 20km away. At the same time, the concept of ship to ship combat has some downright horrifying potential, especially when you realize that all of those missed shots will hit something, eventually.
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