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In many sci-fi worlds, though mostly Star Wars, the main weapon of choice is some form of "laser" weapon that fires bolts that are way below the speed of light. In said universes, some factions have the, apparently, good idea of using ballistics weapons that have some form of energy that encases the bullet (usually some form of plasma).

The main question I have is why? Aren't good old slug throwers like what we have on Earth not good enough? And what advantage does adding such complex parts to a gun and projectile that justify its existence, if any?

Ignoring artistic consistency, of course.

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    $\begingroup$ Just as an fyi: Parts of Star Wars are based on real battles. The attack through the trenches of the Death Star in 'a new hope' is based on an attack with planes on a dam (which used bombs that skipped on the water, hit the dam, sunk and exploded. Fascinating stuff). In the last Star Wars movie they based it on battle ships chasing each other. That is why the lasers curve, despite the utter lack of gravity. They represent battleship fire. Even weirder is that in one scene in the prequels you can see the guns have shells. $\endgroup$
    – Trioxidane
    May 2, 2022 at 4:28
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    $\begingroup$ In space, no-one can hear you scream - this is especially true if the air has leaked out through a bullet-hole. Fortunately, in appropriate cases, plasma weapons dissipate harmlessly into the metal hull's surface (maybe stripping the paint a bit). I'm concerned that this is more about tropes than worldbuilding, but I'm going away now and keeping my mouth shut. $\endgroup$ May 2, 2022 at 4:32
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    $\begingroup$ This seems like a question where the answer is highly dependent upon the specifics of the weapons in question relative to the alternative technologies available. Since you don't describe the technology at all this seems more like a discussion of Sci-Fi genre conventions rather than a question about issues you are having with building a specific fictional world. $\endgroup$
    – sphennings
    May 2, 2022 at 13:37
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    $\begingroup$ Can you edit in some examples of works with energy sheathed projectiles? It might help to focus the question a bit. $\endgroup$
    – Harabeck
    May 2, 2022 at 14:43
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    $\begingroup$ @Trioxidane are you referring to Operation Chastise? I didn't know the Death Star scene was inspired by The Dam Busters $\endgroup$
    – Aaron F
    May 2, 2022 at 16:49

12 Answers 12

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Armor penetration

Conventional bullets all work the same way: by applying kinetic energy directly to a small area on the target and punching through it. This is relatively easy to armor against: hard materials to resist the initial impact and then energy-absorbing materials that deform under stress in order to take the brunt of the hit. State-of-the-art armor for tanks right now can handle pure kinetic impactors of any reasonable size, which is why you see anti-tank rounds that e.g. create a jet of molten metal on impact that is designed to cut through armor.

Right now, for infantry, the materials arms race is in favor of bullets over armor but there's no reason to assume that will continue. Body armor keeps improving, but pure-kinetic bullets don't have much room to do the same: you can manufacture more powerful guns than are routinely used but they have human factors and usability problems like weight, recoil, and ammo supply.

So, you need to turn to something more exotic to punch through the full-body armor that tends to prevail on the Battlefield of Tomorrow in fiction. Whether by application of heat or some more exotic process (electromagnetic? radioactive?), the "energy casing" weakens armor sufficiently that the bullet can punch through.

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  • $\begingroup$ Mass Effect approves of this answer $\endgroup$
    – JMERICKS
    May 3, 2022 at 14:49
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Ammunition

Bullets weigh a lot and need to be carried. An energy weapon really is limited by it's battery capacity. Currently our battery tech is rubbish so any sort of energy weapon simply isn't viable. If you have some sort of magical almost infinite energy system that is tiny and portable then energy weapons become possible.

Simply, the way tech currently is, you get more bang for your buck from bullets.

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  • $\begingroup$ Also, a tiny energy source means high energy density. Damage the cell and you'll get colorful effects beyond what a burning car's gas tank can provide. $\endgroup$
    – toolforger
    May 3, 2022 at 11:44
  • $\begingroup$ Pure energy weapons would be an improvement on long missions without resupply. Think an aircraft carrier with a nuclear power plant that can produce jet fuel from CO2 in the air and recharge all the armaments by plugging them in $\endgroup$ May 3, 2022 at 17:40
  • $\begingroup$ Pure energy weapons would be awesome but we simply don't have an energy source that makes them viable, at least, for the foreseeable future. $\endgroup$
    – Thorne
    May 6, 2022 at 4:24
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Carry capacity and weapon handling.

The recoil of a weapon quickly goes up the more powerful your bullets become. A .50cal mounted machine gun would bruise your body if you fired it by hand.

But if most of the energy isnt mass but for example heat in the form of plasma then the recoil you experience goes down as well as the neccessary size of the bullets. That means more ammo and easier handling of a more powerful weapon.

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They're plasma projectors

These guns fire a short jet of superheated gas, that on impact vaporizes armor and kills by sending the body into shock from the combined explosion, pressing the molten armor into the body, and in case there is no armor, just leaving the body with horrific third-degree burns. This is fatal. Some armor just about manages to prevent a deadly impact, but still, such exposure leaves the body crippled.

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  • $\begingroup$ AKA ranged flamethrowers $\endgroup$
    – user57129
    May 2, 2022 at 16:18
  • $\begingroup$ @user57129 more like "Ranged explosive white phosphor loads" $\endgroup$
    – Trish
    May 2, 2022 at 18:38
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Shield Harmonics

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The plasma envelope allows the bullet to penetrate energy shields. This works because the shields are made of the same sort of plasma. Two possibilities.

  1. The plasma envelope pushes the shield to either side (easier than smashing it) so the bullet has to penetrate a thinner layer of shielding.

  2. The plasma is set to vibrate at a frequency that interferes with the shield frequency. For example the energy shield is not always on. It flicks on and off once per nanosecond and is only active for 1/2024 of the time. If it detects a bullet in that time it remains powered up. However if it detects a plasma packet that also oscillates once per nanosecond it gets confused and doesn't register it as a bullet.

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  • $\begingroup$ Third possibility: the plasma envelope and the shield both act like bubbles: when the envelope hits the shield, it merges with it, and the projectile is now treated as inside the shield as the "lump" flattens out. Of course, this means that the now envelope–free bullet can be stopped by a second shield, but fortunately you can't stack them too close together without them interfering… $\endgroup$ May 4, 2022 at 18:52
  • $\begingroup$ @Chronocidal That would make a nice CRACK when the plasma envelope hits the shield. $\endgroup$
    – Daron
    May 5, 2022 at 0:06
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You can find energy anywhere conveniently you can not find gunpowder as easily.

In a sci-fi environment, it is likely for a group to touch ground on one planet, then a couple of weeks later we touch ground on another.

It is impossible to know how much ammo we are going to need when we touch down on the second planet because we will never quite know what is waiting for us. (Even if we have been there before)

In TV series, its common for the main character to be shot at by people who used to be allies. So logically you wouldn't need to bring ammo for that trip, but in reality you needed it then the most.

What you will always have readily available is energy, particularly of the plasma / laser variant because we have no way to synthesize propellant of any other kind without creating matter. But using nuclear fusion or fission we can develop long lasting energy, or better yet, the sun(s) on local planets can charge our ships and we can bring that energy with us on our laser guns / battery packs.

So energized bullets in this case actually makes sense because of a naturally abundance and necessary recourse we need to travel. Energy.

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Shields

What is different here is that shields are everywhere. Large ships, tiny fighters to even some small drones have them.

The goal of firing a laser is in general taking something out of the fight, so you gain more control over the surroundings. Normal lasers might not be effective against shields, nor are physical armaments. I mean in a universe where faster than light travel can definitely destroy an armada with a single ship, you want to have some convenient [plot armour] device that can deflect it with minimal effort.

It might be a question of easy deflection, or simply not enough energy applied to the target. Though physical limitations can be a factor. How do you get an effective railgun without it taking up too much space of the ship?

The slow moving lasers solve all of this. The turrets can project effective high amounts of energy against the shields compared to other weapons. They only need a connection to the reactor of the ship, making the required infrastructure relatively small. They might be more complex to make, but at a certain point technology has processed so far that it hardly matters, or is even easier than the less complex stuff. In our world we print out millions of computer processors. Making the old transistors that were bigger than a man might be less complex, but the microprocessors are now made with such ease that it makes no sense to build the old ones.

The lasers themselves is much like oil. Instead of just throwing water against someone you can throw burning oil. Besides the kinetic energy you are releasing a lot of energy into the target, in this case the shields. This destructive force doesn't need to be heat. It can have any number of interesting processes that negate or weaken the shield. If it does penetrate the shield it will release the remaining energy as heat upon impact, often explosively.

The slow lasers are simply the most effective energy transport vessels through space to destroy shields, which will be the greatest part of the fight. If the shields are down they are good enough to destroy the target as well, although physical means can then be much more effective.

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  • $\begingroup$ space travel benefits greatly from shields, reduce material wear and tear. militarily a shield could offset inbound projectiles with little overhead the rest of the time. $\endgroup$
    – Dor1000
    May 3, 2022 at 9:50
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Gyrojet Plasma Rocket:

This idea has all of the appearance elements of your weapons, is based on real engineering, and would represent a superior projectile weapon with distinct advantages over conventional guns. It's basically all the advanced designs people have looked for in conventional guns, but with the engineering problems solved.

The gun is actually quite simple, but the bullets are the thing. Your bullets have a self-consuming ammunition, a tiny exploding solid fuel rocket the equivalent of a caseless gyrojet projectile. The bullet slowly consumes itself at the back end continuously accelerating. Once the projectile strikes a target, the rest of the projectile converts immediately to plasma in an explosion. Perhaps this explosion even works like a shaped charge, and a jet of plasma is blasted into the opponent. It is thus armor-piercing.

Because it is a self-propelled projectile, it has little or no recoil (like you'd expect from a ray gun), so it can be fired from a drone or in zero g. This also means it can be fired in a vacuum. It will be appearing to move slowly at the firing location but rapidly accelerates. The appearance will be like a glowing streak, or "plasma bolt." A satisfying flash and explosion go off when the bolt hits. There is no left over bullet (or possibly a blob of melted copper, depending on the design). Because there is a bigger explosion at short ranges, the effectiveness at short range improves and compensates for one of the major weaknesses of the gyrojet design (short range effectiveness).

In its simplest form, none of the projectile is wasted - it is all either fuel or explosion. The closer you are, the bigger the explosion. The further you are, the faster the projectile is traveling and the harder the mass hits.

gyrojet

Advantages:

Why this concept is better:

  • Simple gun (a recoilless rifle) easily built under any conditions.
  • Caseless design allows light ammo, simplified gun design.
  • little or no recoil and self-contained propellant (good for zero g/vacuum)
  • no/low recoil allows man-portable weapons in almost any "caliber"
  • Armor-piecing shaped charge.
  • Complex ammo, but made of simple materials potentially 3D printable. Potentially made easily anywhere people have 3D printers (in the future, everywhere?)
  • Usable from drones and other light platforms (even large 'calibers')
  • Effective at a wide variety of ranges.
  • Simple Visual aiming - rocket with flat trajectories, and like tracer ammunition, each round is visible.
  • Gyrojet design potentially allows smart ammunition
  • Appearance of guns (see above), firing, and utility all match "blasters"
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As an author, I would make those anti-matter sheaths. Absolutely the most known "bang for the buck" we know is matter/anti-matter collision, 100% of the mass is converted to energy.

But the only way we (currently) know to contain antimatter is in a "magnetic bottle" around a vacuum that contains nothing but particles of antimatter.

So the much-slower-than-light brilliantly glowing projectile is actually not the super dangerous part of the projectile: The projectile is actually a machine producing a magnetic bottle and emitting highly energetic particles to protect the antimatter inside from any stray atoms it may encounter on its way to the target. Upon impact, the magnetic bottle collapses, antimatter meets matter and they completely annihilate each other.

Using this idea, you can even justify light-sabers: They generate a streamed "loop" of magnetically contained antiparticles, if they touch anything they annihilate it. But of course the magnetic loop cannot be sustained just as far as you like, the meter or so shown in the film is just the maximum extent such a tall thin cylindrical magnetic bottle can be extended. Heck, that stream of circulating antiparticles may itself be just the thickness of a thread, the magnetic bottle just shines as if the cylinder is an inch across.

The anti-particles themselves are stored in the handle, you don't need more than an ounce to power the light saber for centuries.

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  • $\begingroup$ The trouble with an antimatter annihilation weapon (or more accurately one of the many troubles) is that it is stupidly powerful even in extremely small amounts. An annihilation of 1 gram of antimatter would release about twice as much as the Fat Man nuclear bomb that destroyed Nagasaki (i.e. ~180 TJ). For a more useful scale that could be used to punch through armor you could use 1 nanogram, which would deliver about 10 times the energy of a .50 BMG round. How you would house a system to carefully dish out a nanogram of antimatter at a time is beyond me, but you can always handwave it away $\endgroup$
    – Kevin
    May 2, 2022 at 17:54
  • $\begingroup$ @Kevin Sure. But we already have the technology, in physics experiments at least, of dealing with single atoms of matter. If I calculate correctly, it takes 17 atoms of gold to produce 1 joule by annihilation. How do the physics experiments do it? Beats me, but I know the technology exists. The only hand-waving part is miniaturizing the machinery to do it. $\endgroup$
    – Amadeus
    May 2, 2022 at 18:10
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Tracer shots

In such sci-fi works, the troops shooting such "laser" weapons are already [redacted] by the laws of tropes:

  • Conservation of Ninjutsu: In any martial arts fight, there is only a finite amount of ninjutsu available to each side in a given encounter. As a result, one Ninja is a deadly threat, but an army of them are cannon fodder. This also applies to gunfights, so replace ninjutsu with marksmanship and ninja with shooter.
  • Conservation of Competence: There is only so much competence a given faction can distribute amongst its membership.

If you are to give the bad guys at least a semblance of a chance, you need to give them tracer ammunition (emphasis below are mine):

Tracer ammunition (tracers) are bullets or cannon-caliber projectiles that are built with a small pyrotechnic charge in their base. When fired, the pyrotechnic composition is ignited by the burning powder and burns very brightly, making the projectile trajectory visible to the naked eye during daylight, and very bright during nighttime firing. This allows the shooter to visually trace the flight path of the projectile and thus make necessary ballistic corrections, without having to confirm projectile impacts and without even using the sights of the weapon. Tracer fire can also be used as a marking tool to signal other shooters to concentrate their fire on a particular target during battle.

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Space armour is strong enough that most physical projectiles will bounce off harmlessly — they won't even dent it, and in some cases won't even scratch it!

On the other hand, a plasma cutter will slice through the armour nicely. That is, after all, how they trim it to size, and shape it.

However, plasma likes to dissipate, and will spread out to a harmless cloud within nanoseconds of leaving a gun. One way to handle this over short distances (as used in the real-life MARAUDER plasma railgun) is to fire toroidal plasma charge — i.e. donuts of plasma — so that the plasma's own magnetic field will keep it (very briefly) contained and coherent, like a very delicate tensegrity construct. As you say, these are well below the speed of light — here on Earth, in 1993, we were achieving just 3% of $c$ — but a mere 2mg of plasma delivers the equivalent of 5lb of TNT to the target on impact. Scale it up to ship-mounted weaponry, and every blast from your Star Destroyer is effectively launching a small nuke, without any of that pesky radiation to worry about!

However, there are 2 main issues with that approach: first, boosting the plasma to that speed requires a large accelerator, of at least a meter cubed. Hardly suitable for a pistol! Second, the toroid will still dissipate over time, it just does so slightly slower than unshaped plasma. The only reason it makes a viable weapon is precisely because it is travelling 1 million meters in the tenth of a second it exists for. (A third issue is rate–of–fire, since it can take your particle accelerator quite some time to get your plasma up to the velocities required to fire it)

So, if you want to make the weapon hand-held, you need to slow the projectile down. However, this will also mean that even toroidal plasma will dissipate before reaching the target.

Enter the projectile! The solid slug at the centre of your blaster bolt is, basically, a magnet. As a bullet, it is useless — weak and fragile, it will shatter on impact. However, the magnetic field it generates acts as a "bottle" to contain a charge of high-energy plasma as a sheathe around it. And it is this plasma that actually deals the damage: the "bullet" core is only there to make sure the plasma stays together for long enough to reach the target.

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  • $\begingroup$ Uh… what? Who says "Space armour is strong enough that most physical projectiles will bounce off harmlessly — they won't even dent it, and in some cases won't even scratch it"? Where is that written? How are you measuring the strength of your people's armour, or of the projectiles they face? $\endgroup$ May 9, 2022 at 20:01
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They're Just Better (because of space science magic)

The weapons in the Star Wars movies that I've watched are ridiculously effective. They're just better than bullets in most of the ways people care about. The science of how to make glowing laser bullets that are better than regular bullets is sufficiently advanced to appear indistinguishable from magic, along with hyperdrive, shields, and The Force. But their effects can be observed, and their effects are better (or worse, if you're on the wrong side of the barrel) than the effects of real bullets.

There might be counter-examples in some of the newer or less popular Star Wars media, but in the ones I've seen... no non-Jedi, except for military robots, survives a direct hit anywhere on their body, even from small handguns. More than that, they drop immediately, rather than potentially staying in the fight for seconds or minutes despite being mortally wounded. They go through military body armor like paper. One solid hit with a blaster = you're dead. Nobody ever seems to run out of ammunition. Recoil is minimal. Overpenetration is never an issue. They aren't even loud enough to damage your hearing.

The only down side blasters seem to have is rate of fire, and maybe projectile velocity for long-range shooting. The Empire should probably have invested in some modern-style light machine guns, just to force the Rebels to invest in body armor. A plot hole? Maybe, but real life is full of examples of clueless procurement offices cluelessly deciding that they know better than the guys on the ground.

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