Today I want to talk about science fiction and specifically weapons in science fiction. Anyone who knows me reasonably well knows I really like to talk about guns. I like shooting them, too. I have written lot about guns in the past, present, and future and how they impact a fictional world, and some of that is available elsewhere on the internets.
One thing that is usually true is how science fiction gets weapons wrong. This is virtually guaranteed. Some science fiction gets it mostly right (the UNSC weapons in the Halo series are surprisingly realistic, with a small number of exceptions), but most science fiction just screws it up.
First up is energy weapons. Energy weapons make no sense in most contexts. It is possible that somewhere in the future, electrical energy is so free and disposable that we can use it for guns. Unfortunately most sci-fi settings don't depict this as being the case. In Star Wars, the same energy used to power a blaster that can fire lethal bolts could be used to run Luke's moisture farm for days. It could run a wheeled vehicle for years. It could power your house for months. It could probably run a vehicle like a speeder or swoop for months or more of regular use. It could fly a spaceship on low impulse thrust for virtually forever. Oh, also if we converted the energy in the pack into kinetic energy, it could blow up a pretty good-sized house.
In order for energy weapons to be plausible, they need to deliver recoilless destruction greater than an existing projectile weapon. Now we're talking about enough energy to power your house for years. Maybe decades. These energy batteries would carry so much power that they could juice a whole city. It's not impossible, of course, but there would need to be no such thing as fuel anymore, or fuel would have to be so efficient and powerful that there would not be any shortages of it. Why would you use that much power on a weapon when there were better natural sources of chemical propellant?
Also, in case you're wondering, firearms propellant generally isn't made from any kind of fossil fuel, except possibly in its production -- but if you had free electricity you wouldn't need fossil fuels.
So there's some other options. Portable mass drivers are a thing. I'm not even going to refute it, the technology is plausible and if you have a lot of electrical energy for weapons, mass drivers become possible. They're still more costly than making firearms propellant but there are some advantages.
The problem with mass drivers as infantry weapons is mainly that chemical propellants are cheaper and easier to make. The main draw of mass drivers is that if you can miniaturize the firing system enough, it actually makes carrying ammunition much easier. You still need to feed the rounds into a magazine or belt, but they can be much smaller so a soldier can carry much more ammunition. A rifle mag would be slimmer and could hold 50 or more rounds. Very convenient.
What about Mass Effect where computers shard off a miniature piece of metal? That isn't realistic. The problem with shooting living things (human, animal, or alien) is that stopping power isn't just a function of kinetic energy. You could shoot someone with a 1/10th gram projectile at hypersonic speeds, but all it would do is bore through him and leave a very treatable wound. Not all of the kinetic energy would be transferred into the target, which is really undesirable.
In order for a bullet to stop a target, you want as much of the kinetic energy of the bullet to be transferred into the target as possible. Ideally, that means you need some surface area. You also probably need your bullet going slow enough that it will stop in the target before it goes all the way through, or at least do a lot of damage and exit going pretty slowly. Modern guns, especially handguns, do a really good job of this. Stopping power as a science isn't really known fully yet, but what we do know is that we have a lot of really effective cartridges that are capable of reliably stopping a human. The kinetic energy, velocity, and size of those bullets are known factors, so if we're talking about bullets that are used against people (military or police), they should have similar masses and move at similar speeds.
Another problem with mass drivers is surface area. Ha, I said it twice, right? I'm referring to expansion rather than actual physical surface area. Modern military bullets don't expand (Hague Convention, blah blah) but the most advanced modern bullets used in police and self-defense do. Yeah, you can buy better handgun rounds as a civillian than you can get issued as a soldier. Mind-blowing. Anyway, mass drivers generally use steel or some other hard, ferromagnetic alloy while modern bullets use lead. Lead is denser than steel, so you can get more mass in less space. Lead is also softer, so it deforms better. It expands when it hits something, creating more of that surface area. It's also toxic to most life on Earth, but that's really a secondary concern. You'll die of bullet trauma (shock), organ failure or blood loss long before you die of lead poisoning.
Of course if you use some other non-magnetic mass-throwing technology (like Mass Effect, or gravity, or whatever) you can throw better bullets and negate that problem. It doesn't have to be lead, of course. Lead is just convenient because it's pretty common on Earth. However, an ideal bullet would have similar properties like high density, high plasticity and low hardness.
What about explosive rounds? Well, explosive rounds used against personnel are kind of stupid. How do we make bullets better? I KNOW, WE'LL MAKE THEM EXPLODE! Protip: we already thought of that. The problem is that we already kill people in one shot with bullets. If we were fighting against aliens, we'd make bullets that could kill or disable them in one shot. I mean, 10mm Auto JHP (a pistol bullet) will put you down and probably kill you with a single shot. We have guns and bullets right now that are even more effective at killing fleshy things that aren't humans. .30 caliber/7mm rifle bullets (of all kinds) are extremely capable at killing people at really long range, and can kill tougher things than people like elk, caribou, or big wildcats. We have bigger or higher velocity bullets used to kill buffalo, rhino, hippo, elephant.
Making bullets explode is like saying that we have all this technology right now that we use to shoot bigger animals than people, but we're gonna ignore it because exploding bullets are TEH KEWLZ. In general, if it's the size of a human, .30 caliber rifle bullets are slightly overkill except at long ranges. In fact, we switched to .223 bullets because we realized that .30 caliber bullets were overkill. And then we invented .300 BLK (and 6.8 Remington and a bunch of other rounds) when we found that .223 wasn't quite enough to reliably take out a human. We have exploding rounds right now and they're used for shooting at stuff. Typically stuff made of metal, like vehicles or equipment. A lot of these exploding rounds are much bigger than the rounds we use to shoot at people (like 20mm or 30mm autocannon bullets).
Exploding bullets are fine but they should have a purpose. They shouldn't be just stuck into Space Marine bolters just because they're cool (not that anything in 40k makes sense). Exploding bullets are also bad because if they hit something and explode without penetrating, they usually end up being worse than a bullet that had penetrated a little without exploding. This isn't always the case especially with concrete fortifications (a great choice for explosive bullets), but it's true of most other targets.
So let's go way back to mass drivers again and talk about making bullets faster than real bullets, bigger than real bullets, or both. Let me also say that anyone who made something like a bolt pistol has clearly never shot a real gun before, or at least not any gun with real recoil. A lot of fiction makes mass drivers better or more powerful than real guns, typically by making bullets faster but sometimes by making them bigger. Unfortunately, whenever you shoot a bullet from a gun, the exact same force in that bullet is also applied on you. As the bullet's energy increases, so does its recoil force. And we know that mass times velocity equals energy, so adding more of either makes things worse on us.
And again I want to point out that our science of creating bullets is really good. We've made tons of very effective ways of killing different things for different reasons. You don't need to make a bullet bigger or faster than it needs to be.
What about body armor? Well, humorously mass drivers are pretty good at dealing with it. I really like mass drivers in that role because you can hypothetically flick a switch and go from 800fps to 1500fps. The first setting is light-recoiling, doesn't penetrate walls (great for urban), doesn't ricochet as badly and will reliably stop a person depending on the bullet. 1500fps can shoot through drywall, wood, car doors, and some body armor too, but it'll recoil a lot more and might ricochet on hard objects at close range. That's a real, interesting advantage of mass drivers, that you can take the same 120 grain bullet and go from a pistol caliber carbine type bullet to a medium-powered rifle bullet with the flick of a button. That's pretty attractive, but is sadly never mentioned in science fiction.
What should weapons be like in sci-fi? Well a quick summary for the tl;dr people:
- Energy weapons aren't viable except in extremely super-advanced society, where energy is not a problem at all. Think Star Trek levels of advanced.
- Chemically propelled cartridges are not made with fossil fuels and are unlikely to ever be completely obsolete.
- Mass drivers (electromagnetic or otherwise) are feasible, but the main advantages (lighter ammo weight, adjustable velocity) are rarely discussed in fiction.
- Weapons and ammunition will be tailored to adequately kill or stop appropriate targets. In a universe without aliens dramatically different than humans, the weapons will resemble current man-stopper weapons. With aliens that are different, specialized weapons (or possibly just velocity settings) will be designed to combat them.