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đź”— Essay on Realistic Space Combat

I have had this post from SpaceBattles.com saved in my browser bookmarks for well over a decade now. It felt like the sort of topic my readers may enjoy so I thought I'd highlight out some of the more interesting passages.

Note: for the purposes of this essay I am assuming only technology theoretically achievable to current science. Devices such as force shields, cloaking devices, FTL drives, reactionless drives, and other such common soft SF tropes are assumed to either not exist or exist in such a matter as to have minimal impacts on tactics (ex. an FTL drive that requires you to exit the solar system before it can be used, like in Larry Niven’s Known Space universe).

Damn it! I thought I could just set deflector shields to maximum and call it a day.

Well, the thing you really have to remember about space is that it’s big, dark, cold, and empty, and, paradoxically, you have perfect visibility. This brings us to our first realization: there will be no stealth in space. Any source of radiant energy in space will be very obvious. Since any spacecraft will be emitting a lot of radiant energy (your vessel will usually need to keep its habitation module several hundred degrees warmer than the external environment to prevent your crew from freezing to death for starters) it will stick out from the cold darkness of space like a campfire in the desert at night. Surprise attacks will be rather difficult, to put it mildly, when the enemy can see you coming halfway across the solar system. The simple fact is just about every viable space propulsion scheme in existence works by blowing hot gas out the back of your ship, and that’s just not something you can hide. The space shuttle’s main engines could be detected past the orbit of Pluto. The space shuttle’s maneuvering thrusters could be detected from the asteroid belt. Even a puny ion drive with an acceleration of .01 m/s^2 (1/3000th the space shuttle’s acceleration) could be spotted at a distance of 1 AU (the distance of Earth from the sun).

It's a funny thought that to get into space we have to be travelling at such insane speeds that we actually become easier to spot. Also paradoxically, the faster we make things, the easier it is for us to detect and therefore not get hit by them.

We humans have a profoundly distorted intuitive sense of how motion works, as a result of spending our lives in an environment ruled by friction and gravity. In space movement will follow the Newtonian rule that an object in motion will remain in motion unless acted upon by a force counter and equal to the force that set it in motion. What this means, in practical terms, is that slowing down will take every bit as much energy as speeding up. On Earth if you’re in a car and shut the engine off you slow down and stop. In space if you turn the engine off you’ll just keep drifting away at the same speed forever.

I legitimately wonder what percentage of the first-world doesn't understand that there is no friction in space?

Another thing about motion in space is that changing your ship’s orientation does nothing to your speed and vector unless it is accompanied by firing your main engine, because there is no friction. This means that all those space dogfights where one fighter gets behind the other and the other one has to try and shake it like in air combat are very unrealistic. There’s no comprehensible reason why the pursued pilot can’t just turn his fighter around and blast the bugger.

I had never thought of this but it makes complete sense. How has not a single science-fiction movie or show not had something like this? Seeing a space fighter just pivot in place would be super cool.

In space there are three basic kinds of weaponry available to you: missiles (guided kinetic and explosive weapons), guns (unguided kinetic weapons), and directed energy weapons (lasers and particle beams). Guns will probably be mostly useless: in order to be competitive with lasers and missiles they will need infeasible muzzle velocities of thousands of km/s. That leaves missiles as your most powerful weapons.

To fully understand why missiles are superior to lasers and guns (aka railguns) you just need to read the whole section on weapon systems. Going into this I always though railguns would be best because the speeds they could theoretically reach would always be highest but I could not have been more incorrect.

OK, so we’ve got the technical stuff worked out, so what will a real space battle probably look like? Well, you’ve probably got a fairly good idea already, but let me summarize it for you. The best terrestrial analogy for space warfare would probably be a battle on a perfectly plain at night, fought between sports cars painted with phosphorescent paint, with machine guns mounted on their hoods. All sides will be aware of the movements of the other. The battles will likely consist of long periods of boredom while the ships chase each other, accelerate towards each other, or vie for an intercept that favors them, punctuated by a few minutes of terror as they scream past each other at many kilometres per second and fire away.

OK, so we're essentially pirates in Bugattis with guns on the roof. I love this mental imagery.

In pop SF fixed defenses usually take the form of armed space stations bristling with weaponry like Medieval castles. Realistically, it’ll probably be a bit different. The largely one-shot one-kill nature of space combat will tend to push defensive installations away from reliance on a handful of hardened installations and toward reliance on a large number of dispersed expendable platforms. There will be military space stations, but they’ll be refueling and servicing facilities for the warships.

Just like on Earth, when you stop moving you make yourself an easier target. But unlike on Earth, things are moving at such ludicrous speeds that being stationary on a battlefield with perfect visibility and no cover, you're just asking to be destroyed.