So You Want To Have A Space Combat – Part One

I do too. One of the great joys of science fiction on screen is watching giant capital ships pound the snot out of each other. I’m here today to talk about how you can make that happen in your own work!

There are a lot of ways for space combat to take place in science fiction that depends heavily on technology levels and on how much you decide to treat space like an ocean. In a hyper-advanced setting like that found in the culture novels, combat will take seconds at most and will be handled entirely by AI. Then there’s the other end of the scale where ships pull up next to each other to exchange broadsides. I’m going to choose to talk about space combat in a setting like The Expanse or Revelation Space. Universes where there are some fantastical elements but are also grounded in reality.

Shootouts Across Space And Time

Space is really big. It’s had to really describe just how big it is. The human brain really isn’t designed to comprehend the sheer scale of space. And when I say big I mean big, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.

With the scales involved, it’s worth considering what distances combat between ships takes place at. It’s had to hide in space since space is very cold and ships are very hot surprise attacks are bound to be difficult unless the side doing the surprising has time to set a trap. In most situations, your characters will have advanced warnings of their attackers. This doesn’t mean that you can’t have tension though. Two ships could be barreling towards each other for days or weeks before they get close enough to exchange their first blows. And that’s where time and space come in.

With spacecraft moving as fast as they do it’s not enough to know where a target is, but where it will be. Remembering the fact that light does not travel instantly it’s important to keep in mind that a ship’s view of where its target is is actually where it was.

These distances and information delays mean that your characters might need to wait hours or days to find out if the missile they just fired ever hits its target. Or if shots have been fired in their direction.

Doing Damage The Conventional Way

There are a lot of possible weapons but I am going to focus on the three that the expanse uses; missiles, rail cannons, and point defense cannons (PDCs). Lasers are cool too and should be considered, I’m a fan of grasers myself, but a lot of the same limitations for the other three will apply to lasers too.

In the case of all three, it’s important to remember that humans will have very little to do with their aiming and firing. Humans will pick targets and perform maintenance, but it makes much more sense to leave the actual operations to computers.


Missiles are going to be very useful, especially if they allow the warheads to be replaced with other payloads and come equipped with sophisticated targeting and guidance computers. Missiles have a few things going for them

  • They can survive a lot more gees than a human can so they’ll probably catch up to whatever they are fired at.
  • They can be programmed to take complex paths to their targets.
  • They can adjust course midflight.
  • Components can be adjusted to change yield or pupose (ex. makeshift sensor pod).
  • They don’t need to actually hit their targets, just get as close as the given payload requires.

Missiles aren’t perfect though. Their engines are probably going to create a fair bit of heat, although cold gas thrusters might be useful in some cases. Most of a target’s PDC’s are going to be aimed at them in an attempt to blow them up before reaching effective range. There are ways to get past this. But a lot of combat between capital ships is going to be either firing missiles at long range or trying to detect and intercept missiles at long range.

Rail Cannons

I know, I know. Shouldn’t these be outdated? Shouldn’t missiles be so much better? Well, yes, they should. But strangely, depending on the technological capabilities of your setting, a solid projectile fired at relativistic speeds actually works pretty well.

Compared to missiles they are going to give the users less control after firing, but they are going to be harder to detect and harder to hit. Sure the enemy can look at where your cannon is pointed, but with the speed of light considered will probably be a few minutes old. That’s a lot of time to adjust your aim. And on account of not having a tail of hot plasma or ions, it’s going to be a lot harder to detect.

Now, a great deal of how useful rail cannons are will depend on the technology available in your setting. Here are a few examples.

  • Energy is plentiful and components are compact. This allows a ship to have multiple cannons that are each able to fire projectiles at relativisitc speeds.
  • Energy is plentiful but components are bulky. A ship has one or two rail cannons that are large and obvious to attackers. May or may not fire projectiles at relativistic speeds.
  • Energy is not plentiful and components are bulky. A ship can only fire ocassionally. The one or two railguns on board need time to charge their capacitors between volleys.

Point Defence Cannons

Remember what I said about giving AI control of the weapons? PDCS are probably entirely controlled by AI. Missiles and rail cannons at least have humans picking targets and maybe picking approaches, but PDCs need to be much faster than that.

PDCs need to fire a lot of small projectiles quickly. The idea is to increase the odds that they hit the missiles or boarding shuttles that they are meant to be intercepting. The projectiles might be mildly explosive, the equivalent of flak shells, or simple solid slugs. And that’s really all I have to say about that. Here are some examples of different use cases.

  • In order to disable or indimidate another ship the crew manually desigates a handful of PDC bursts.
  • Where sensors are not able to track missiles in real time, the crew selects different interception algorithmns based on what parts of the ship they think are being targeted.
  • Dedicated to the mission above all else, the crew instructs the ship’s computers to prioritize the PDCs to cover only the most critical systems.
  • With limiting sensing and control technology PDCs are programmed to fire in a wide cone aimed by a human opperator.
  • Computers and sensors are advanced enough to track individual missiles and aim grounps of PDCs at them.

Adding Sci-Fi Flavor

Everything up until now has been very mundane (remember I said no lasers). Now I’m going to add some fun twists to the three weapons systems above, because if you can imagine a way to kill people, us humans will probably try it eventually. These will all be various degrees of scifi hardness.

Hydrogen Foam – I’m stealing this idea from a fantastic series called Revelation Space. Here’s how it works. Hydrogen is a gas and it really wants to be a gas. But under intense pressures hydrogen can form a liquid or even a solid. Because hydrogen wants to be a gas, if you compress it into a liquid it’s going to expand violently the first chance it gets.

Nanite Nets – if you make a net that is a few microns thick and spread it out in front of a ship moving at a significant fraction of the speed of light then the ship will have a bad time. At lower speeds, a wide nanite net could do a lot of mischief from subtle sabotage to dissolving through the hull to hack into computer systems and get the intel without ever risking a single member of the attacking crew.

Monomolecular Shards – imagine a lot of ultrathin graphite sheets broken into shads and released to form a dense cloud These could be dispersed in a cloud by a fleeing ship and wreak havoc for a pursuing ship that is not paying attention. A bit like futuristic caltrops.

Drones – there are a lot more things a ship could launch besides missiles and railgun slugs. One idea I particularly like is a cloud of autonomous weapons platforms that could carry their own PDCs, racks of micro-missiles, sensor equipment, maybe even boarding parties. These drones could maneuver around a target and potentially be harder to hit than a complete ship.

Up Next

In the next part, we’ll talk about armor, damage control, and what a destroyed ship might look like. Follow me on Twitter at @expyblg for updates!

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