I'm writing a semi-realistic science fiction story set, let's say, 500 years in the future, where humanity has colonized some of the solar system. For combat purposes, I've been playing with the idea of two common weapon types:

  1. a semi-automatic ballistic weapon with frangible rounds, for defense onboard a spacecraft (you don't want to cause a hull breach!)
  2. the weapon I'd like to discuss: a laser sidearm.

I don't want these laser weapons to have a rapid fire rate or a continuous beam. I'd prefer if they functioned like a musket, with one shot and then a long "reload". My current idea is that each shot uses one capacitor as ammunition; when drained, the capacitor must be removed, then another is snapped in place. Even then, this process would take a skilled user 3 to 5 seconds. I'd like it to be somewhere between ten and thirty seconds. This weapon would mainly be used to take down criminals in heavy anti-ballistic armor, which the frangible rounds cannot penetrate.

How can I explain a laser sidearm that has one shot, then a 10 to 30 second reload time?

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    – Secespitus
    Commented Aug 23, 2017 at 10:52
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    $\begingroup$ I see you already accepted an answer. That's fine as accepting what is helpful for you is completely up to you. But as a little tip for the future: WorldBuilders live all around the globe in different timezones. Your question currently only has 51 views and was asked only 40 minutes ago. It's often a good idea to wait at least 24 hours before accepting to give everyone the chance to have a look at the question and check whether the answers are good or need some work. It increases the quality and some people might be deterred if they think you found your answer. You can accept as often you like $\endgroup$
    – Secespitus
    Commented Aug 23, 2017 at 11:32
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    $\begingroup$ Can you provide a rationale for the existence of such a weapon? it doesn't seem terribly useful. $\endgroup$
    – ths
    Commented Aug 23, 2017 at 11:49
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    $\begingroup$ I love settings with higher-tech but "lower-tech" ideas of weapons (lightsabers, one-shot "pistols", etc.) My suspension of disbelief is strained, however, unless the author answers why someone would use a one-shot weapon (even a powerful one) when a modern 9mm semi-automatic can put out more (even if they're less powerful) rounds. Why would I handicap myself with this laser gun instead of a good old-fashioned slugthrower? $\endgroup$
    – Ghotir
    Commented Aug 23, 2017 at 14:01
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    $\begingroup$ @ghotir Exactly my thought. Sure, when inventing hi-tech sci-fi gadgets, you have a lot of latitude in the capabilities that you suppose they have, as the technology is all hypothetical anyway. But if the hi-tech gadget is less capable than existing machines, why would anyone use it? Maybe there's some situation where this one-shot laser is better than a 21st century pistol, but you'll need to explain when and why. $\endgroup$
    – Jay
    Commented Aug 23, 2017 at 15:19

14 Answers 14


Lasers need a lot of energy to be used as weapons. Even with a high-density battery (better than our current Li-ion batteries), it's going to be a large and heavy battery, so it's the equivalent of a one-shot cartridge. Every time you shoot, you discharge the whole battery, and you have to insert a new one.

Another possibility is cooling time. Even if you have batteries or generators able to provide the power the laser needs, it's a lot of heat to deal with, so you have to wait 20-30 seconds before you can shoot again.

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    $\begingroup$ Adding: EXCEPT (cooling time) the battery also acts as heatsink - so you replace the heatsink that is really hot and put in a new one ;) Well, of not heat sink the battery also has liquid that turns into gase from the heat - one use colling cartridge ;) $\endgroup$
    – TomTom
    Commented Aug 23, 2017 at 12:38
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    $\begingroup$ If you just have to switch out the battery, someone would very soon develop an automatic weapon that uses a clip/belt of batteries and exchanges empty for full ones within milliseconds (this is 500 years into the future, after all). Your idea about cooling time prevents this, though - I like that. There might still be automatic laser guns, but they would need a heavy and unwieldy cooling system. $\endgroup$
    – oliver
    Commented Aug 23, 2017 at 13:33
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    $\begingroup$ @oliver a clip of batteries may be too heavy to be easily mobile, which would allow stationary turrets nicely. $\endgroup$
    – DonyorM
    Commented Aug 23, 2017 at 13:46
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    $\begingroup$ @oliver With a 0.5kg battery the size of a AK-47 clip allowing just for one shot, there's not much room for improvement. You just can't just make a 3kg clip the size of a box of shoes and attach it to a pistol. $\endgroup$
    – Rekesoft
    Commented Aug 23, 2017 at 13:50
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    $\begingroup$ You don't even have to switch out the battery. Batteries can store a lot of energy, but they can't necessarily discharge that in a short enough period of time. Instead, the battery continuously charges a capacitor which can discharge quickly enough to fire the weapon. (Compare the real-life usage of capacitors in a car stereo: crutchfield.com/S-76VDwLx66BS/learn/learningcenter/car/…) $\endgroup$
    – chepner
    Commented Aug 24, 2017 at 12:28

You could have your power supply as 2 parts:

A super-capacitor that, once fully charged, can power one shot from the pistol.

A battery. The battery provides a slow trickle of power to the super-capacitor that takes however long you want to want it to to power up the next shot. Say, 30 seconds.

Your battery pack can supply 1, 6 or more shots depending on how you want the mechanics to work.

One important question you'll need to answer is, if you need to change clips as often as with a normal pistol why they don't just use normal gunpowder pistols. Perhaps the advantages of being able to recharge ammo for free back at base is a big enough advantage.

You'd also expect someone who can hook their weapon into a more powerful power supply to be able to fire a lot more shots per minute unless you want to make the weapon prone to overheating.

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    $\begingroup$ Capacitors: yes. Also, they could make that little rising-pitch whine, like defibrillators: "ooooiiieeeeeee- pew!" The cosplayers will be on that. $\endgroup$
    – Neal
    Commented Aug 23, 2017 at 13:07
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    $\begingroup$ Maybe they don't use batteries, instead they use a miniature fission-reactor. It provides basically infinite energy and thus infinite ammunition. You just have to wait until it charges the capacitor. $\endgroup$
    – nwp
    Commented Aug 23, 2017 at 13:25
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    $\begingroup$ @AdamRilatt Whatever mechanic you choose, unless everyone wears super heavy protective goggles all the time in this war there's going to be a lot of soldiers with damaged vision from near misses hitting objects near them in their field of vision. $\endgroup$
    – Murphy
    Commented Aug 23, 2017 at 14:17
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    $\begingroup$ An example of the whine @Neal mentioned: youtube.com/watch?v=EzdMYhkOdT8, youtube.com/watch?v=u3BYjJnw4bs. Makes for a nice sci-fi sound! $\endgroup$
    – Bob
    Commented Aug 23, 2017 at 14:22
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    $\begingroup$ See also old, cheap, camera flashes. There would be a slight whine while the batteries recharged the capacitors in those. $\endgroup$
    – CaM
    Commented Aug 23, 2017 at 16:59

You can use a chemical laser

A chemical laser is a laser that obtains its energy from a chemical reaction. Chemical lasers can reach continuous wave output with power reaching to megawatt levels. They are used in industry for cutting and drilling.

Incidentally, the output power make them suited for weapon use...

If your laser is designed in such a way that a cartridge with the reactants has to be loaded before use, this can easily explain why between various shots one has to pause:

  • reloading the cartridge
  • allow cooling down of the equipment
  • require finite time to allow the system to neutralise the HF gas before loading the next charge or choke to death

An added benefit is that you can set it to free purge when fighting in vacuum and fire as fast as you can reload (pump action shotgun style).

The reason for laser over more powerful balistic sidearms is the damage they would do to the ships hull is less likely to result in an explosive decompression of the craft, however a hole cauterised through a pirates helmet and head is likely to give him pause.

Third party edits added

  • $\begingroup$ Chemical, or gas dynamic, either would do. You could I suppose use something like a COIL where after loading the cartridge and flipping the switch to arm, chemistry has to happen to make the laser gases and you then have a finite time to use the resulting chemical oxygen in the laser before it recombines. Deuterium/Florine is also possible, but someone hitting the ammo would not end well for the guy carrying the ammo. $\endgroup$
    – Dan Mills
    Commented Aug 23, 2017 at 13:31
  • $\begingroup$ The problem with chemicals reaction is that you can more or less always find some catalysts to make it faster, and if they're fighting in space with lasers they can have found plenty of new possible catalysts on new planets. $\endgroup$
    – Rolexel
    Commented Aug 23, 2017 at 14:12
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    $\begingroup$ @Alexandre Um... not really no. Catalysts aren't magic and don't exist for every reaction. More importantly, speeding up a high energy reaction could result in many problems including a non-uniform energy or concentration density, increase cartridge cost, decreased cartridge storage life, increased weapon fatigue, or (and most concerning) weapons exploding in the wrong way. Catalysts may be needed/used but that doesn't mean that mean you can't speed up a system like this indefinitely. $\endgroup$
    – kaine
    Commented Aug 23, 2017 at 14:58
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    $\begingroup$ This was my initial thought as soon as I saw the title of the question. It reminded me of the movie Real Genius, where the laser was "frozen in an excited state." Just think...if the cartridge is small enough, you can build a six-shooter laser or convert a Colt .45... $\endgroup$
    – Deacon
    Commented Aug 23, 2017 at 20:29
  • $\begingroup$ @kaine I know this, but since it's still part a fiction, and they seem to explore space it could lead to discoverys, and then hacks of this reload time. I just wanted to point out this possibility for the OP or anyone who could want to work on your theory. Plus, all the exploding part of the problem could be turned as a mastered part of it, you could have a weapon shooting like 5 times in a row and then become a strong grenade, or only shoot once or twitce and then cool down a couple of minutes. It's fiction, you can come up with whatever you want $\endgroup$
    – Rolexel
    Commented Aug 24, 2017 at 9:50

Having actually built a laser in the past, I think this might be a smaller problem than you realize.

Modern lasers aren't a burn risk until they reach around the 3 Watt range. (Yes, only three Watts, but concentrated in a single direction; pen lasers are more like a milliwatt device.) At that point, not only is the beam plainly visible in the air, it will cook flesh by both radiation and induction.

However, such beams usually take around half an hour to heat up and provide sufficient light. It involves reaching a state called a "population inversion", meaning that more than 50% of the active medium is in an excited state. Afterward, pulsating lasers generally have a reflective block on them; energy gathers while the beam is contained. Well, that's one way, there are a bunch of odd ways to do it.

The other thing to consider is that these lasers, like dye lasers, are generally the size of an entire table, and cost around US$100K. The rationale behind the military not using them for infantry weaponry yet should be overt.

500 years in the future, it's likely that we'll have made a few discoveries which will make them a lot smaller. However, as historical precedent shows, there is no guarantee that we'll have made equal progress on warm-up time. Perhaps the beam takes a full five seconds to reach population inversion?

Another thing I would like to point out to you, on the side, is that light does actually carry momentum; and while it's usually insubstantial to massive creatures like people, it is quite tangible for a focused beam. That's part of how one can get burned by a high-wattage laser. It's also why, under the wrong circumstances, a laser might do little to protect the hull. (It's also why dumb mirrors are completely useless against weaponized lasers.) Look up the "Mössbauer Effect" for further details; it might even give you some ideas for your writing.

  • $\begingroup$ When I read this question I was thinking isn't that the usual characteristic a laser has? Thinking back to my physic course on highschool, I remember having learned, that a laser actually is simply light sent into a chamber where it is in between2 mirrors sent through some specific elements which bundle(?) the light. Can't we just use the time the light has to travel through the "mirror chamber" as explanation and also describe some powerful characteristics by that procedure? $\endgroup$
    – Zaibis
    Commented Aug 24, 2017 at 7:29
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    $\begingroup$ Well, almost. The key difference with a laser is that, while other light sources deepend upon "spontaneous emission ", lasers use an alternative process called " stimulated emission " which requires the presence of initial photons. $\endgroup$ Commented Aug 24, 2017 at 18:10
  • $\begingroup$ A 3 watt laser is the size of a table? My school has a 40W+ laser cutter where the actual laser is about the size of three C batteries stacked together. I don't udnerstand $\endgroup$
    – anna328p
    Commented Aug 25, 2017 at 21:06
  • $\begingroup$ Depends on the type of laser, Dmitry; as well as the type of Wattage you're referring to. The dye laser we were using, around 2001, reached a total of 4 W and took up the better part of a pneumatic table. Some forms of laser do exist which are smaller, but it requires a significant change of active medium and methodology. The ones we built required a set distance between the two mirrors—down to the micrometer—in order to reach stimulated emission; HeNe is a great example of that. An alternative spacing gets you no beam, or famously, a green beam, or GreNe. $\endgroup$ Commented Aug 25, 2017 at 21:11
  • $\begingroup$ Generally lasers reach and fall back from the population inversions in fractions of a second. Modern lasers are more compact and powerful than old dye and gas lasers from academia in the past. You can get a 4W laser that is smaller than your small finger. To penetrate metal you would need a well focussed spot with much more power continuously at 50W is considered a very low limit. A pulsed laser is more practical and measured in Jules per pulse. $\endgroup$
    – KalleMP
    Commented Aug 26, 2017 at 13:38

Don't make them literal lasers. Make them plasma weapons instead.

In a plasma weapon, a small piece of ammo is heated to the plasma state, and then the plasma is fired at the target using a magnetic field. The target is damaged by the heat of the plasma, and plausibly by the plasma's kinetic energy or electrical charge as well.

A plasma weapon might have these characteristics:

  • Typical rifle or pistol shape. The part you hold in your hand contains ammo storage and the heating chamber. The barrel contains the magnetic coils for launching the plasma.

  • Simple weapons would use a supply of pellets, which have to be heated to be fired. This would take time. Larger weapons with bigger power supplies might have a storage tank for plasma, allowing rapid fire. The barrel would also build up heat and need time for cooling.

  • Shots would emit visible light and heat in all directions. Notably, they'd be visible from the side, unlike a laser.

  • Shots could be different colors depending on what is in the ammo. The evil Coppertonians might use weapons that fired a green beam, for example.

  • Shots might "only" travel at several hundred to a few thousand feet per second, instead of traveling at the speed of light. Under the right conditions, someone could hypothetically see a shot coming and dodge or otherwise react to it.

  • $\begingroup$ Space low temperatures may make it hard for plasma shots from spaceships to spaceships $\endgroup$
    – Rolexel
    Commented Aug 23, 2017 at 14:15
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    $\begingroup$ Space is not cold. Space is a vacuum. It's like putting your plasma in a thermos flask. It will radiate heat, but it won't quench like you'd get in an atmosphere. $\endgroup$
    – Sobrique
    Commented Aug 23, 2017 at 15:03
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    $\begingroup$ A plasma weapon would work well, but I'm actually trying to incorporate the non-visible beam of a laser into my story; the only time the beams will be visible is if there's smoke or an aerosol screen. Thanks for the input though! $\endgroup$ Commented Aug 23, 2017 at 20:51
  • $\begingroup$ Do you have a source for how magnetic coils can produce thousands of atmospheres of pressure, and then maintain that pressure from an indefinite distance, even after the projectile has left the weapon? $\endgroup$
    – Catgut
    Commented Aug 23, 2017 at 21:12
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    $\begingroup$ @Catgut: self-stabilising plasma toroid magnetic circuit handwave. Basically they've figured out a way to get the charged particles in the plasma to move in a way that generates a magnetic field that keeps the plasma contained and the particles continuing to move in the necessary way, at least for a short time. $\endgroup$ Commented Aug 24, 2017 at 16:29

A charge storage device (capacitor, battery, etc.) that can give you the fast discharge you need for a laser shot has to be heavily optimised in that direction - and so will be poor on things like overall power storage, leakage rate when charged, etc.

Therefore you may well find you have the laser being fed by something like a flywheel+dynamo; the flywheel is then spun up by a power source (such as a more conventional battery) that can store more power over a longer term, but takes a while to deliver a shot's worth of power.


Hand cranked capacitor.

Steampunk pistol with added hand crank.

This would be similar to a crossbow which one must crank up with a handle between shots. Here, the crank flexes a piezoelectric crystal, accumulating charge in a capacitor. At full load the capacitor discharges into the laser generator and fires. Then get cranking!

Artistes and creatifs: I tried hard to find an image of a steampunk weapon with a handle and bike gears mounted on the side. No luck; I had to halfassedly MS Paint my own. But this would be a fine project for Dragoncon or some similar venue where there is a forum for steampunk creations.

gun from https://i.pinimg.com/736x/37/23/c2/3723c21ad87c2785a64268ac889ded31--arms-race-steampunk-weapons.jpg modified by me with crank from https://www.picclickimg.com/d/l400/pict/263133537680_/Antique-Victorian-Eastlake-Style-Brass-Doorbell-Hand-Crank.jpg

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    $\begingroup$ In a spacefaring civilization though, why wouldn't you just have a power pack that charges the capacitor much quicker (and with much less manual effort)? $\endgroup$
    – Doktor J
    Commented Aug 25, 2017 at 14:59
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    $\begingroup$ @Doktor J : Maybe this is a weapon often carried by people far from civilization where power is unreliable. Maybe the powerpacks themselves are unreliable and prone to explosion? $\endgroup$
    – Willk
    Commented Aug 25, 2017 at 21:20
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    $\begingroup$ Magnificent photo concept (and comendable DIY editing). $\endgroup$
    – KalleMP
    Commented Aug 26, 2017 at 13:27
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    $\begingroup$ @KalleMP: I am delighted with "commendable"! $\endgroup$
    – Willk
    Commented Aug 27, 2017 at 14:01

Do they need to have to take it out? Capacitors, like the ones in flash photography, take a while to charge a lot of energy from a low amp, low voltage battery. This could explain the wait time. If you want them to have to remove the battery, you could have single use battery technology.

One way to figure this out is to estimate how much energy light would need to burn through fabric, metal, plastics, etc, or just look up ballpark estimates, then reverse engineer battery technology to match that.

Another reason you could use would be single use, nuclear batteries. It fires, but you have to open the chamber to vent the radiation or risk being burned, then eject the battery once it's cooled or no longer high radioactivity. Then, the user replaces the battery with a new one.

Changing the caps themselves don't really make sense as caps are not an energy source, but an energy storage device.


The Springfield MMMXI muzzleloading carbine/revolver is your choice!

This carbe is the combination of state-of-the-art plasma technology ( most Scifi lasers in our beloved movies actually act like plasma!).

How does it work?

The carbine consists of three main parts. The muzzle, that has a plasma-push stick attached. The cartridge vessel, that loads the energy cell. The trigger, state of the art sensitive hammerhead engine.

How it might look according to our engineers: (copyrigh -> someone, somewhere).

Carbine enter image description here Revolver enter image description here Steps to use it:

First, take a Plasma cell from your space cartridge box. They're round, expell a radioactive shiny color, and are shock resistant as they don't have any catalizer installed. You can play tennis with them! (2-8s)

Second, put the plasma cell with the + side pointing outwards from the muzzle, into the muzzle. push it hard, it's made to fit in void without holes. (4-8s)

Third, push it down with the plasma-push stick. (4-8s)

Fourth, open the breechloading energy compartment. (2-4s)

Fifth, introduce the unstable Unobtamium energy cell, the catalizer that will transform the glowing plasma in a all-environement super fast, glowing projectile. (4-8s)

Sixth, close the catalizer and pull the activation lever. (2-4s)

Seventh, aim and shoot.(Ns)

approximate 1-shot time length with no skills:

40s to 1 minute.

Power output: that of a small artillery piece.

Disclaimer: Mimetic Radioactive plasma cells that mimetize with the nevironement they're shot are on sale. It's like an invisible shot (that irradiates a lot of heat and shows on infrared or with spray/dust).


A ruby laser is a pulsed type laser that uses a Lab grown Ruby doped with Cadmium and some rare earth minerals. You excite it with a Flash tube. Depending on which flash tube you use and how much power you put through it, they will burn out after only a single pulse. Still powerful enough to punch a hole in thin gauge, mild sheet steel.


Instead of using batteries use a generator (something like a Fuel Cell, but enhanced) that cannot give enough power to keep the laser on continuously, but will need to recharge (possibly ramping up voltage) a condenser which will provide the energy for the shot, but will need time to recharge.

A mechanism similar to old battery-capacitor flashes.


I really like the idea of weapon style 1. 1 way 2 explain your laser pistol would be that instead of firing from the changing the capacitor, the pistol itself contains a capacitor, and to reload you instead add batteries, it takes 10-30 seconds for the batteries to charge the capacitor. I'd love to read your story at some point.


Maybe Mass Effect (the video game series) can give hints here? In Mass Effect 1, continuous fire would overheat a weapon, after which there'd be a cooldown of 5 seconds or so until you could shoot again. Some overpowering weapon mods would make sniper rifles overheat from a single shot, so there'd be a cooldown timer after each shot. To me, that sounds similar to what you're getting at.

Mass Effect 2 then introduced a thinly-veiled ammunition system: your weapon builds up thermal heat until it's overheated, at which point you'd throw away the "thermal clip" (=emptied magazine) and insert a new one.


You can use an Explosively pumped flux compression generator to power a laser or other energy weapon, it uses explosives to create a very short, very strong current.

Each generator would come in a nice disposable cartridge that you can spend several seconds reloading. It also has other nice aesthetic benefits, such as causing a nice bang sound, and possibly a flash from venting the exhaust.


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