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Why Haven't Laser Guns been made yet?


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I'm wondering why laser guns haven't been made yet. Can't you just put a laser from a laser cutter, hook it up to a switch(trigger), and a battery? I dunno. Can anyone tell me what's wrong with this plan?

EDIT: Silly me. Completely forgot the power and heat issues. Thanks everyone. A laser is a light amplified by stimulated emmision of radiation after all, so a laser powerful enough to destroy would use lots of energy. Also the other issues too.

EDIT 2: Silly me again. Didn't read stuff. Anyway, just forget my last edit

Edited by SpaceEnthusiast23
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Energy density, mostly. Also, issues with lasers in atmosphere and a host of other things.

Lasers are inefficient, producing lots of heat. But they also need lots of energy to do damage, as the energy is not kinetic but radiation, essentially heat. Thermal damage on orders similar to kinetic damage must be very high intensity and high energy, otherwise it would be less than a sunburn. Low energy would require more time to inflict damage, not very practical. So the intensity and energy must be huge, meaning small spot size (maintaining that over significant distances may prove an issue) but huge amounts of power. Assuming the energy must be similar to a bullet, around 2000 joules (slightly less, but I like round numbers), we can calculate the power required for stopping the bullet, which imparts damage to the target. If we need to deliver similar amounts of energy, but in just 1 thousandth of a second, then we need 2 megawatts of power, ignoring losses. And the size of the laser/cost and other things depend on the power more so than applied energy. Of course, conventional firearms produce similar amounts of power to accelerate the projectile, but they have the advantage of fast chemical reactions. Of course, technology will improve with time, and laser weapons are being deployed on ships, albeit not as primary weapons and with short ranges.

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It was an essay by the Sci-Fi author David Drake where I first encountered the basic problem. A man-killing laser needs an immense amount of power. And also heat rejection. Anything less than that and it becomes a one-shot (or even no-shot) weapon. If it takes 10 seconds to recharge and cool down enough to fire again, that's a terrible rate of fire. And what if it takes 10 minutes? Or 10 hours? Using any known technology, in order to have something that can fire again as fast as the soldier can aim takes a energy source that is not at all reasonable for a portable weapon.

Chemical-powered weapons (rockets, bullets, etc.) suffer from limits on ammunition, but they are just as deadly the first shot as they are the last shot, and you can tailor the ammunition supply to the mission. Yes, they also suffer from heat rejection issues, but there are ways to manage that (spare barrels, etc.).

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1 hour ago, mikegarrison said:

It was an essay by the Sci-Fi author David Drake where I first encountered the basic problem. A man-killing laser needs an immense amount of power. And also heat rejection. Anything less than that and it becomes a one-shot (or even no-shot) weapon. If it takes 10 seconds to recharge and cool down enough to fire again, that's a terrible rate of fire. And what if it takes 10 minutes? Or 10 hours? Using any known technology, in order to have something that can fire again as fast as the soldier can aim takes a energy source that is not at all reasonable for a portable weapon.

Chemical-powered weapons (rockets, bullets, etc.) suffer from limits on ammunition, but they are just as deadly the first shot as they are the last shot, and you can tailor the ammunition supply to the mission. Yes, they also suffer from heat rejection issues, but there are ways to manage that (spare barrels, etc.).

This, lasers has some benefit, first is accuracy, you can hit small and fast objects like incoming missiles, this become even more useful on planes as its easy to point the laser mirror in all directions giving you an weapon who can hit incoming rockets, other planes and ground targets.
No its not powerful the 20 MM cannon on planes are much more destructive but the laser is easy to aim.
This is why its lots of interest in laser weapons. 

For handheld use its pretty pointless, you would not be able to hit supersonic stuff with an handheld weapon anyway and guns are simple and cheap.

 

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Unlike what sci-fi movies told you, in real life, laser is actually an impractical weapon system. Aside from pinpoint accuracy and instant-hit capability, lasers usually suffer from:

1. Power requirement: This is undoubtedly one of the problem faced by energy weapons (not just laser). The power requirement of generating laser beam with sufficient power to be considered as a weapon to actually cause a damage (and not just blind people) is absurdly high. You will need a nuclear reactor or self-sufficient power generating method to fulfill those power-hungry laser to be considered practical

2. Range: Lasers do have a long range, but in atmosphere, there's a problem with beam dissipation. Basically, laser beam decays as they travel through air. This can be mitigated by increasing the intensity of the laser, but then it ends with more power requirement. Even if the laser have a very long range, the terrain is still a problem. Basically, every laser weapon needs a line-of-sight to the target to be able to damage them, in other words, the laser weapon is as exposed as it's target for return fire, while with good 'ol artillery barrage, you can do same (or even more) damage to target by simply arcing the projectile around obstacles, potentially even surpassing the range of laser weapons while being safer as you fire them from behind terrain obstructions.

3. Damage: Bullets, missiles, rockets, and any other ballistic weapon cause a damage on their target ON IMPACT. While lasers, being a sustained beam, need to be focused on target for a few moments as it cause GRADUAL DAMAGE, meaning most ballistic weapon might be able to destroy the incoming missile targeting an aircraft carrier as soon as it impacts the missile body, but laser beam need more time as it damage the missile until it's sufficiently damaged, during which, the missile might be already close enough that it's destruction still send damaging debris on the carrier

4. Heat: Lasers have poor heat dissipation. Most ballistic weapons can mitigate heat by simply changing barrel (and even if the barrel becomes damaged due to overheating, it's barrel simply need to be replaced). Lasers need a way to dissipate heat, which might be a radiator-type heat exchanger or coolant-based system. But then this brings a question: if a laser gun breaks because it's overheated (like a gun with warped barrel), does the process of fixing it could be considered as practical or complicated? Most guns can simply change the barrel, but laser gun is not a simple thing, it's takes an engineer or scientist to fix that thing, it's not something that every soldier can fix in the middle of battle like their jammed gun

Not to mention cost :P

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Offtop.

Spoiler

A tandem of (laser + microwave emitter + ultrasound emitter) would be greatly useful for an evil scientist living in a grim castle somewhere in Middle-Earth, Westeros or any other medieval.

They spend nothing except pure energy (need no ammo or fuel),
They can be focused with much less number of moving parts than a machine-gun or a flamethrower (so, need less or no spare parts)
Their firepower is tunable.
They don't miss.
They can be easily managed from a notebook.

So, you can put several turrets around your castle and set guard mode on.
Once a hero comes close to the redline, a pair of the nearest turrets gets refocused to him, target with low-energy lasers, and switch on the ultrasound.
Dogs, cats and don't know, maybe the horse who accompany him, get worried and try to alarm him.

If the hero is enough stupid to proceed (as clever animals already get retired), the turrets automatically switch on the microwave emitter.
The hero feels hot, and not only for his braveness.

If this freak keeps moving and crosses the last line, the turrets set the microwave power to maximum  and switch on the high-energy laser.
The hero, blinded by laser and in red-hot (from microvawe) armor (he can't take it off for obvious reasons) randomly walks and falls dead.

If you prefer to capture him, you can switch off the latter options and just wait while he falls down unconscious. Also in this case his armor stays clean.

Also, less armor - less burns. so innocent peasants will not get significantly harmed.
(So, you can continue using their village as a trade post.)

 

If there is a whole army of peasants with horsed heroes, this also helps not to aim them one-by-one to shoot, but can just easily warm them all at one.
Most of soldiers will cowardly run away after first microwave shots, while real knights will rush forward and get fried.
So, you even don't need to click with mouse! Before you get out from bed and look at the screen, the battle will be won.

 

It's easy to aim dragons with laser and blind them, causing their disobedience.
(Griffons, too. I dislike this ugly species.)

You can easily hit the nasty dwarvish spies crawling between the rocks. One shot - one blind dwarf falls down from the wall.

You can easily capture pirate ships with no real harm to anybody onboard, including the captured recaptured princesses,
(Then take their treasures and let them go. In such way you can easily collect treasures and princesses with no trouble,)

 

So, we can conclude, that emissive weapons with no ammo and moving parts are the best friends of an educated dark overlord.

Upd.
 

Spoiler

As they use pure energy, any energfy source is appropriate: nuclear reactor, windwill, water wheel, coal, wood, even magic.

 

Edited by kerbiloid
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Funnily enough I was having the "What sci-stuff from the past did and did not get invented yet?" conversation with someone yesterday and this was something that came up.

We too came to the conclusion that it was, like several other such things, a power issue. We just don't have a cheap or practical way to cram enough watts into a portable device. 

With something like a mobile phone, the power problem has been tackled from both directions: Improved batteries and reduced power requirements. But the problem with the "laser gun" is that there continues to be a high power requirement that can't be reduced much because you need to transfer a lot of energy to a target to do damage.

So until we have the holy grail of loads of power in a small, safe, cheap battery then this kind of thing is likely to remain sci-fi for a while longer. However, I suspect that some lateral thinking might produce something with similar effects but without the high power requirements, like a sonic, rail or ice gun. 

 

Edited by Foxster
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I dare say that power isn't even the key limitation, it's the energy coupling. Bullets are more efficient at demolishing targets than beams; whatever power source you come up with for your laser, I can plug it into a railgun and get superior mileage in all but a few very specific situations.

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Projectiles do damage by means of impact. Energy can do damage, at most, by evaporating things.

I guess there's a reason that we have laser cutting, not bullet-cutting, and bullet holes, not just holes. One is to be done neatly while the other it's meant to destroy things.

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9 hours ago, SpaceEnthusiast23 said:

Can't you just put a laser from a laser cutter, hook it up to a switch(trigger), and a battery?

Uuuuum... what are you thinking? Laser cutter and laser emitter is not the same. Laser emitter that have a long range is generated from optical amplification based on the stimulated emission of electromagnetic radiation. This laser have long range, but almost do no damage (other than blind people). Assuming what you mean by laser cutter is the one that's usually used to cut metal, it's generated by discharging electric current through a gas, which means the range of your laser gun is limited to how far the gas can be expelled (think it like a long range blowtorch), not counting the power requirement and cooling needed to destroy the target, then you might just grab a gun and shoot your target instead

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25 minutes ago, ARS said:

Assuming what you mean by laser cutter is the one that's usually used to cut metal, it's generated by discharging electric current through a gas, which means the range of your laser gun is limited to how far the gas can be expelled (think it like a long range blowtorch),

U. wot. m8!?

LaserCutter.jpg

Quote

There are many different methods in cutting using lasers, with different types used to cut different material. Some of the methods are vaporization, melt and blow, melt blow and burn, thermal stress cracking, scribing, cold cutting and burning stabilized laser cutting.

Vaporization cutting

In vaporization cutting the focused beam heats the surface of the material to boiling point and generates a keyhole. The keyhole leads to a sudden increase in absorptivity quickly deepening the hole. As the hole deepens and the material boils, vapor generated erodes the molten walls blowing ejecta out and further enlarging the hole. Non melting material such as wood, carbon and thermoset plastics are usually cut by this method.

Melt and blow

Melt and blow or fusion cutting uses high-pressure gas to blow molten material from the cutting area, greatly decreasing the power requirement. First the material is heated to melting point then a gas jet blows the molten material out of the kerf avoiding the need to raise the temperature of the material any further. Materials cut with this process are usually metals.

 

Edited by DDE
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Well, most of the cutting laser is a gas laser AFAIK. But even then, using cutting laser as a weapon is not a practical idea anyway

Edited by ARS
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22 minutes ago, ARS said:

Well, most of the cutting laser is a gas laser AFAIK. But even then, using cutting laser as a weapon is not a practical idea anyway

A gas laser is still a laser. It still produces a beam; the hot gas exhaust is a byproduct of using a different medium. The operational version of Skif was to use a CO2 laser to engage targets over hundreds of kilometers.

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33 minutes ago, DDE said:

A gas laser is still a laser. It still produces a beam; the hot gas exhaust is a byproduct of using a different medium. The operational version of Skif was to use a CO2 laser to engage targets over hundreds of kilometers.

Well, that's new for me. I'm sorry if I misunderstood some of the stuff. I'm working on manufacturing company, so most of the stuff about laser cutting is still very basic for me, since that's what my workmate knows. Anyway, thanks for the info! :)

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6 minutes ago, HebaruSan said:

Would it be possible to defend against such a weapon with simple mirrors?

Possibly. A laser beam is I think a very powerful light. I'm not sure, but I think so.

EDIT: Wait. No. The light thing is a different kind of laser (info from pervious posts). So no. Mirror not going to work. 

Edited by SpaceEnthusiast23
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19 minutes ago, HebaruSan said:

Would it be possible to defend against such a weapon with simple mirrors?

Your average mirror is only about 90% efficient, and the reflective layer is fragile enough that the 10% not reflected is enough for it to stop being a mirror pretty quickly.

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52 minutes ago, HebaruSan said:

Would it be possible to defend against such a weapon with simple mirrors?

No. The mirror gets burnt through near instantly - see @Kryten's note on efficiency. Using a high-albedo material for all of your armour (good example - aluminium) is a potential mitigator. But, basically, you're ought to go looking for a strong, heat-resistant material. Aerogel (OK, not necessarily strong), basalt fibre, boron carbide or nitride, carbon-reinforced carbon...

Edited by DDE
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43 minutes ago, HebaruSan said:

Would it be possible to defend against such a weapon with simple mirrors?

As mentioned above, you wouldn't want a mirror made from silvered glass (which has a nice insulating layer of glass above a tiny mirror layer that heats up).  A more effective defense is to make the target shiny (any polished metal, aluminum should work well) and rotating.  This is easier when trying to force a laser to blast N-1 missiles and force at least one missile through.

One thing to remember is that in [US] military terminology, a "gun" is operated by a crew.  "We" already have "laser guns", but nothing like what Han Solo might strap to his hip.  Considering the US Navy has some large ships powered by nuclear reactors, they aren't terribly worried about the amounts of power needed (note: I think the ships that have these laser aren't nuclear powered, but they still have big engines).  Ships also aren't as concerned with cooling (I know the Navy, at least recently, used water-cooled heat exchangers for their electronics).

There was supposedly some work on an "X-ray laser" back in Reagan's "Star Wars" project.  Somehow it was supposed to detonate a nuclear explosion and then use the X-rays (or simply heat/pressure) to get coherent X-rays.  This may have been pure bunk to get the Soviets on a useless path, because I've never heard of it since.

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2 hours ago, DDE said:

U. wot. m8!?

LaserCutter.jpg

 


This method (melt and blow) is very similar to a plasma cutter (common shop tool for cutting steel, stainless steel, and aluminum) and it's very effective in cutting holes, patterns,  or even cutting off metals in a very short time. Eventho' it's not a laser (electric arc melts the metal, compressed air blows the material down and away from the cut) it's rather power intensive (average setting on our plasma cutter is 70 amps at 240 volts) so if a simple plasma cutter needs 16,800 watts to cut 10mm thick stainless steel (shiny) then think of how much power a laser cutter would need.

Laser guns are a cool idea, but unless optical components inside the gun reach 99.999% transmission and reflectivity, plus a power supply that is small enough for a person to carry and be able to deliver at least 30,000 watts at any given time, over a extended period of time, this ain't gonna happen.

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Handheld lasers make perfectly good weapons. They are commercially available today, to common people, for fairly cheap.

You just have to step away from the silly notion that you would use lasers to cut flesh. :P 

Here's an example. This laser is available in 1W for $199, and 3.5W for $299.

The 1W variant (watt, not kilowatt) comes with the explicit warning to never turn this thing on without wearing the included safety goggles because at typical indoor ranges of less than 5 meters, the reflection of the beam hitting a surface can be enough to temporarily blind you. Nevermind the beam hitting your eyes directly, which can cause permanent blindness with even a second's worth of exposure.

Now keep in mind, they sell you one with nearly four times the power of that. And it's not the highest power you can get by any means. 5W and more is just as easily available.

And then there's hobbyists building things like this from scrap.

For this application, the color of the laser matters. The blue light emitted by the linked example is actually the most dangerous to the eyes. Green lasers are slightly less dangerous at the same wattage, with red lasers being less dangerous again. So raw power is not the only thing you should consider when judging the danger.

Edited by Streetwind
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