Astrotropes: Space Battles part 2

In Space Battles part 1, I discussed the basics of how real life space combat might work and why the crew of a Battlestar would need to be good astronomers to get the upper hand on their opponents. In part 2, the knives are out. Let’s talk about space weaponry!

Really, there are two types of weapon used throughout science fiction in deep space fights. Energy weapons and kinetic projectile weapons (the latter of which includes missiles), and in truth these are quite sound possibilities in reality too. But remember before. Dogfights might not actually happen in space. It’s far more likely that two ships might duel while being so distant they can barely see each other. It becomes less like Top Gun and more like a battle between snipers. To maximise your chances of actually winning, you’d hopefully be making your first shot before your opponent knew where you were. Perhaps before they even knew you were there.

Lasers

Without warning, a patch of the ship’s hull suddenly glows white hot and explodes into plasma and droplets of glowing metal, slowly cooling in space. The blast jolts the entire vessel, knocking several crew members off their feet. Somewhere thousands of kilometres away, the attacking vessel sees a sudden increase in infrared output from their target, informing them that their shot hit home.

Lasers in real life won’t be like the ones you see in the movies. There will be no pretty red or green beams visible. Actual lasers in space will be a lot more stealthy, but no less deadly.

Invisible until it hits, a high powered laser pulse will instantly vapourise whatever it connects with. If it hits a ship’s hull, it’ll blast a hole with startling speed, ripping whatever material the ship is constructed from into ions. Also, the sudden rapid ablation of the surface of the ship into gas and plasma would indeed exert pressure and, if large enough, jolt the ship. More so if any depressurisation occurred as the result of the gaping hole now in the ship’s hull.

Also, while movies like to depict lasers as continuous beams that slice things up into glowing chunks of metal, well aimed laser pulses would probably be far more effective. Most lab experiments use pulsed lasers for one simple fact – using the same power supply, you can pack a lot more energy into pulsed lasers than you can into a continuous beam.

I actually heard a rumour of a lab somewhere in which, when calibrating their high energy laser, they like to vapourise bricks. Funnily enough, given how eccentric some physicists can be, this wouldn’t surprise me. Suffice to say that lasers would probably be the most effective kind of space ship armament you could have. Accurate, long range, and capable of rapidly ripping apart any target.

Kinetic Projectiles

(Or as you might know them better, bullets and missiles.)

In retaliation, the damaged ship launches missiles. Accelerated by a railgun, three projectiles fire towards the opponent in rapid succession, at speeds of nearly 3 kilometres per second. Seconds after being launched, the missile engines flare into life, aiming for the infrared signature of their target, and accelerating them at 80 g. Even at such blistering speeds, they have a huge gulf of empty space to get through before reaching their final destination.

As I was musing not long ago, kinetic energy can and will kill you. At least it will if you’re not careful, anyway. Like I said before, an object travelling at three kilometres per second will do damage equal to its own weight in TNT. The same object travelling at 90% the speed of light will do damage equal to its own weight in antimatter. In other words, accelerating a projectile as much as possible before hitting its target would mean it could impart massive damage. And that’s not even accounting for any explosive charge carried by that projectile!

The defending vessel spots the missiles as soon as their engines fire. Three new bright infrared sources in their field of view. But missiles are small and difficult to target. In the few minutes the missiles take to reach their mark, the defending crew will need split second accuracy to avoid being destroyed. A gunner, stationed at the ship’s laser cannon, waits anxiously. As soon as the targets are within resolving distance, the navigator gives the all clear. The gunner takes careful aim and fires, as the ship’s pilot changes their velocity to avoid shrapnel. One hit, again signalled by a sudden flare up in infrared brightness. Then the second explodes, seen clearly in visible light. Two missiles are down, but the third still remains. A bead of sweat runs down the gunner’s forehead, as she takes careful aim at the third. A laser blast and a third and final burst of infrared signal the destruction of the final missile.

The best defense against missiles would probably be to destroy them before they reached you. Those lasers would be good at that, and even the huge distances in space would mean that accelerating to even with rapid acceleration, it would still take missiles a few minutes to cross the literally thousands of kilometres that make up this playing field. It would still be difficult to resolve something as small as a missile and successfully target it before it struct. Hats off to that gunner. But it’s not quite over yet.

All down to the pilot now. The gunner’s careful shooting pulverised the missiles, but only one was exploded. Two lumps of superheated molten metal are still speeding towards the ship at close to 100 kilometres per second. Firing the ship’s engines at full force, the ship changes its velocity, taking several seconds to overcome inertia. The first destroyed missile sails past the ship amid a hail of shrapnel from the exploded missile, missing by only a few metres. But the next isn’t quite so easily evaded. Unable to move in time, the ship is still in the path of the missile’s remains as it crashes into the one of the ship’s main engines. With that much kinetic energy, the damaged engine is ripped clean away from the rest of the vessel. The resulting jolt is strong enough to give several crew members concussion as they’re hurled into the walls.

Everyone seems to forget that even if a missile is destroyed, exploded even, it still leaves a chunk of mass speeding towards the same target. How exactly those projectiles are destroyed becomes important. If they’re vapourised, then a cloud of hot metal vapour can still cause damage travelling at high speeds. If they’re exploded, less material may impact, but the remaining shrapnel may be travelling at even greater speeds. Or if they remain as cohesive molten remnants, as in the case of this unfortunate ship, they could still do some serious damage.

I’ll leave the ending of this little skirmish to your imagination – as well as who the combatants are and exactly why they’re fighting. But I hope my second foray into space battles has highlighted a few interesting facts.

trope is a recurring theme in any narrative which conveys information to the audience. These are snippets of information which have somehow ended up in our collective subconscious as ways in which storytellers have gotten their points across. Overused tropes end up as clichés.

Inline images are from Star Trek: First Contact, because the Star Trek depictions of laser and missile weapons in science fiction are about as iconic as it gets. © Paramount Pictures, all rights reserved. Images are used here for research and criticism in accordance with fair use policies.

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About invaderxan

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
This entry was posted in astrotropes, physics, space. Bookmark the permalink.

2 Responses to Astrotropes: Space Battles part 2

  1. Baribal says:

    I think plasma weapons could be considered as a third class. Without actually digging into it, I guess that they’d suffer greater attenuation than lasers/masers/*asers and wouldn’t transfer enough mass to count as kinetic weapons even at projectile speeds close to c, but still, it’s a very-fast-moving cloud, so it would heat up the whole side of a ship (or less if fired in close proximity), possibly disabling lots of fragile systems (sensors, gun turrets) at once which would be lucky shots with beams or projectiles.
    Also, this guy has covered a lot of ground on the topic of space combat over at YouTube: http://www.youtube.com/user/SpreadingtheMuse
    I’m still thinking about actually putting my notes to work, and I think there are a few issues with your lines of reasoning (like IR sensor resolution, or ships using hot gas / the exhaust of liquid medium lasers as IR “chaff”), but… Well, I’m at work right now, please don’t tell my bosses. :)

    • invaderxan says:

      To be honest, as long range space weaponry, I’m not entirely convinced that plasma weapons (if they can exist) are even feasible. Given things like the ideal gas law, plasma would probably become rarefied quite quickly. After a kilometre or so, it’s questionable how significant it would be compared to the background solar wind, for instance. Also, the two weapon types here definitely can (and do) exist.

      Thanks for the link, too. In honesty, most of this is just me thinking like an astrophysicist, taking my own understanding and applying it to sci fi. I’m not claiming to be an authority, so if you can see anything wrong or which needs improvement, do let me know!

      I’m intrigued. Please tell me more about which lines of reasoning you find questionable, and why – I was hoping someone might say that! :)

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