Imagining realistic energy weapons

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Tamren
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Imagining realistic energy weapons

Post by Tamren »

Over time I've been slowly ditching the various misconceptions I have about energy weapons portrayed in sci-fi media. Thanks in no small part to things like Outsider who incorporate elements of realism. For instance until recently I've thought that man-portable laser weapons would drill precise and even holes in a human target. Without secondary effect other than neatly cauterizing the wound. In reality the area struck by the laser beam would explosively vapourize, having a similar disruptive effect in terms of tissue damage as a lead bullet.

I figured this was a good place to update my knowledge a bit, so let the discussion begin! All of you making RP threads will probably find this a handy topic as well.

To start things off, I've been playing a lot of XCOM and one key component of humanity's war against the aliens are laser weapons. The laser rifle is probably the best standard rifle weapon in the game and remains effective all the way to the final mission. However, other than the basic principles of laser function I have no idea how I would build one.

For instance, how wide would the beam be? The "calibre" of a laser weapon is just a matter of focus. But the desired effect of the laser beam is delivery of energy. So would the thickness of the laser beam alone have any effect on its performance as a weapon?

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Re: Imagining realistic energy weapons

Post by fredgiblet »

Tamren wrote:For instance, how wide would the beam be?
How wide do you WANT it to be?
Tamren wrote:But the desired effect of the laser beam is delivery of energy. So would the thickness of the laser beam alone have any effect on its performance as a weapon?
Very much. The wider the beam the more dispersed the energy is. That will be difference between punching a hole through someone and giving them a mild sunburn.

osmium
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Re: Imagining realistic energy weapons

Post by osmium »

http://www.youtube.com/watch?v=RUXXGbNS8oY

Note especially the slow mo and demonstration on wood towards the end of the clip.

A high enough energy laser or really any electromagnetic radiation based weapon would very quickly boil (i.e. turn into gas) the matter in the direct path of the beam (i.e. the spot).

There are a number of factors to consider for energy weapons. For light based ones the absorption of the light in the matter that it is expected to be fired against can be a big deal. If your goal is to penetrate some amount of armour and damage some delicate (say computer) systems on the other side you likely want a very high energy photon (like X-rays or gamma rays). However that same beam would be significantly less effective against a human target as a very significant fraction of the energy will pass right through. Some materials absorb few X-rays, but most visible light that hits them. Another factor is the power to spot size ratio. Basically if you know what you need to melt and how quickly you need to melt it to accomplish whatever the intended purpose of the weapon is. That will specify a power requirement in order to attain that amount of energy transfer into the target for a given spot size.

Others can chime in more, there is certainly more distance to cover, just a few random thoughts.

-O

Tamren
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Re: Imagining realistic energy weapons

Post by Tamren »

Very cool video. The beam demonstrated there has been focused down to a few mm.

Against metal a thinner beam means a thinner hole vapourized in the material. But say you fired the beam into something water-packed, jello for instance. Would a tightly focused beam of 1mm transfer the same amount of energy and vapourize a similar amount of material as a less focused beam of 10mm? Or would it affect a much smaller area and drill a hole straight through and into the ground?

Most man-portable laser weapons in fiction have thick beams. But it sounds like it would make more sense to focus the beam down, especially in regards to armour penetration.

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Mjolnir
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Re: Imagining realistic energy weapons

Post by Mjolnir »

For laser weapons, expect large apertures. They'll tend to look more like telescopes than sci-fi laser guns:
http://www.youtube.com/watch?v=LThD0FMvTFU

This does a couple things...it makes it easier to focus to a small point at a large distance, reduces heating of the air leading to beam defocusing effects, and keeps the beam intensity low enough to keep the air from ionizing, which would block much of the beam. It also keeps the intensity on the output optics down so that they don't self destruct if you get a speck of dust on them.

Also, it's often pointed out that beams won't be as visible as they are in movies, but another thing is how bright and violent the effect on the target will be with a laser powerful enough to burn a decent hole in it. The clip osmium linked demonstrates some of this. Note that much of what the camera saw was scattered near-infrared that is largely invisible to the eye, but still quite capable of causing eye damage, and the vaporizing material will be comparable to an electric arc.

Majincarne
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Re: Imagining realistic energy weapons

Post by Majincarne »

Another reason laser based weapons will have a large aperture and beam size is you have to keep the laser on target for enough of a duration to deal damage to the target. Small beams mean the object you are hitting needs to be still or tracked to an extraordinary degree.

To burn through a missile casing and deal damage to the internals you probably need a few milliseconds dwell time over an area of the missile thats illuminated by the beam. Not hard if its sitting still. However a missile will be armored somewhat to protect against high speed travel. it will be spinning for stability and the added affect that that makes tight beam lasers infective and it will likely be flying an avoidance pattern to prevent interception by point defense.

So a tight beam would hit he missile and melt the missile casing surface as teh affected hull material would be constantly moving out of the lasers beam width.
A larger beam with is less powerful but affects much more of the missiles surface giving the affected hull material more exposure time to the beam before it can be moved out of the beam.

The exact with and power needed are determined by how hard the object is to keep targeted(how good your tracking is) how strongly it is armored and how powerful your laser is.
And if your hitting a missile with a beam that burn it though with a pin head sized hole in a nanosecond your wasting fire from a weapon capable of disabling systems on a cap ship on a loansome missile.

Also note if lasers are your primary point defense the enemy missiles are likely to be mirror coated with a cermet under hull.
This also applies somewhat to human targets as well as if its anything other than an ambush they are going to be ducking and dodging, and possibly wearing armor of their own.

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Arioch
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Re: Imagining realistic energy weapons

Post by Arioch »

Assuming that the original poster is referring to a man-portable laser weapon, it would have to be of a high enough power to do instant damage, or it would probably not be a viable weapon. Target tracking and attempting to keep a weaker beam trained on a target for long enough to do damage would be very problematic for a hand-held laser.

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Re: Imagining realistic energy weapons

Post by osmium »

Again I think it boils down to purpose. I mean we *have* energy weapons. Some are designed to be non-lethal others shoot down rockets and satellites etc (namely the microwave "pain beam" crowd control / area denial sort of weapon / the chemical laser powering the 737 laser as well as the one above).

If the goal is to punch a hole in the person, blind the person/sensor, heat up the device to cause premature explosion / failure of important components, cause physical damage via cutting holes or penetrate something (armour, some sort of casing etc) and cause some damage through it without really damaging the intervening substance each will pose different design goals.

I think the major problem with man portable lasers will be the power requirements to cut through the atmosphere and project enough power into the target to cause significant damage... especially when considering that projectiles weapons are likely to be much harder to stop. Was it the luger that was railed on in WWI(or was it II) for not having enough "stopping power" with it's 7.65mm (later 9mm) round. So any laser weapon is going to need to be able to produce the effects of that pulse laser I linked at what 50 yards with more than 8 times the diameter (requiring 64 times the power output * some factor to make up the loss for not being at like 1cm range) and penetrate at least as far as a round would (i.e. 6" or so) OR it's going to have to be super accurate so that a small spot size can be used well (such as by poking a hole in the eye and damaging the brain, or by causing damage to a major artery or organ reliably from a similar distance to projectile weapons).

I feel like for man portables the reason you might use an energy weapon would be to utilize the characteristics that make them unique from projectile weapons. I think a sniper type rifle energy weapon could be *very* effective, and would provide interesting characteristics, such as potentially blinding enemies nearby to the target, it may be harder to locate, or if you use invisible wavelengths of light you could make a weapon that would be very difficult to pinpoint the angle of attack of.

-O

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Mjolnir
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Re: Imagining realistic energy weapons

Post by Mjolnir »

Arioch wrote:Assuming that the original poster is referring to a man-portable laser weapon, it would have to be of a high enough power to do instant damage, or it would probably not be a viable weapon. Target tracking and attempting to keep a weaker beam trained on a target for long enough to do damage would be very problematic for a hand-held laser.
I would expect a serious laser weapon to have a good deal of optical stabilization and target tracking built in. Once it starts firing, the hot spot produced on the target will be rather easy to track...use filters to cut out the scattered laser light so the spot can be seen clearly.

(this is of course for weapons that operate at planetary or orbital ranges, where lightspeed lag permits such tracking)

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Re: Imagining realistic energy weapons

Post by Arioch »

The enemy can see this spot too... any weapon that doesn't deal instant damage in a tactical situation like that just invites the enemy to kill you with his conventional rifle while you ask him to politely stay still and wait to catch on fire.

Again, I'm talking about small arms. We already have chemical slugthrowers that are very effective, portable, inexpensive and reliable, so in order to be viable, a laser is going to have to be even more effective. Since it's almost certainly not going to less expensive, lighter or more reliable.

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Re: Imagining realistic energy weapons

Post by osmium »

Only thing I'd do it turn around Mjolnir's statement to make it clearer (perhaps) for our less English fluent peoples: at planetary and orbital ranges light speed lag introduces only a small % error, unlike the light second lag we talk about often in ship to ship combat at which distances light speed lag introduces significant error in the knowledge of the position of something.

Also to note, there could be a category of "laser" weapon that covers the whole body that could work even if slow. The point being that the target cannot look at you without being blinded, so while it doesn't protect you from his friends, your friends may very well have similar weaponry too. I guess the point being that if it doesn't deal instant damage it needs to have some very good reason why it can get away with it (difficulty in locating a long range shooter, inability to look in the direction of the beam, by the time they notice it's too late because their gun has melted etc).

-O

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Mjolnir
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Re: Imagining realistic energy weapons

Post by Mjolnir »

Arioch wrote:The enemy can see this spot too... any weapon that doesn't deal instant damage in a tactical situation like that just invites the enemy to kill you with his conventional rifle while you ask him to politely stay still and wait to catch on fire.
The enemy will only see the spot if you miss. They'll probably feel it though.

And again, I'm talking about using stabilization and tracking systems to keep the beam on the spot it first hit without requiring inhumanly steady aim. No need to ask the enemy to sit still. Very similar systems are already implemented in cameras.

Arioch wrote:Again, I'm talking about small arms. We already have chemical slugthrowers that are very effective, portable, inexpensive and reliable, so in order to be viable, a laser is going to have to be even more effective. Since it's almost certainly not going to less expensive, lighter or more reliable.
This is true, weapons using chemical-propelled solid ammunition is a very compact and effective way to store and deliver energy to the target, on top of the weapons and ammunition both being quite cheap and simple to make. I also have doubts about the practicality of laser small arms due to eye injury concerns. When witnessing a high-power laser strike a shiny object somewhere in your field of view has a good chance of leaving permanent holes in your vision...

I mostly see lasers being useful as anti-artillery and anti-air weapons. Laser "small arms" might have some use in some very limited situations, such as security systems where electrical power is easier to supply and secure.

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Re: Imagining realistic energy weapons

Post by Majincarne »

A realistic use of a man portable in atmosphere laser would probably not be in the damage dealing section of the weapon. at least not directly.

I remember hearing about experiments using a laser to ionize the air between a weapon and a target in order to give an electrical discharge a conductive path to travel through to the target.
Such a weapon would likely be far more effective than a laser for energy used until you got to very thickly armored installations or vehicles where a lasers penetrating power would be advantageous. though probably not more so than a good and excessively sized shape charge in a missile would be.

An ionizing arc weapon would positively deathly to personnel unless they happen to have been wearing a full suit of chain mail. and even then rather uncomfortable burns are likely to happen.
That probably still counts as an energy weapon even if its not using lasers or plasma balls.

here we go. Not eh weapon but they both discus teh laser electric arc properties.
http://home.earthlink.net/~jimlux/hv/hvtrigsg.htm
laser arc welding PDF(page 10 for relevent arc laser properties)

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Mjolnir
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Re: Imagining realistic energy weapons

Post by Mjolnir »

Electrical discharge weapons, even with a UV laser to pre-ionize a path, will be rather unpredictable, limited in range, and quite sensitive to weather. They seem like another thing for more controlled environments, like inside buildings...and not only as a lethal weapon due to the deterrent factor (for instance, having lightning jump across the door in front of you).

And of course, lasers are used right now for target designation. Perhaps a combination laser/heat seeking system could be used, with the projectile locking onto the spot of a laser not powerful enough to cause damage itself, and then seeking on the hot spot left by it. This would be more vulnerable to countermeasures like flares, but would avoid the need to keep the designator on the target. Simple optical tracking on the target itself would probably work just as well, though.

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Re: Imagining realistic energy weapons

Post by BattleRaptor »

Weapons grade lasers for soft targets(living) blow them apart, they dont burn neat little holes into anything, they cause massive raggid holes that dont penetrate very deeply either.

Infact a new version of non lethal weapons uses such a laser to vaporise 1/100th mm of your skin to create a concussion wave that knocks you and anyone in 3 m of you out.

Another type using the same effect is overall low power but fractures lenses on equipment and missiles.

Lasers in general have 3 effects.

Slow-heats the target over time
(these work by continual heating and reflective armor works agasint them, this also includes pulse lasers that turn on and off to allow the vaporised gas to disperse before the next blast)
These lasers work by heat.. to melt/burn or otherwise damage the target.

Flash-These are very short single burst.
these work very quickly and reflective type armors dont work., The atoms cant absorb and reflect the photons before more hit.
They cause explosive effects with very high Brisance.

Then you have Femto array based lasers, when focused correctly on target they cause matter to decay much like a matter/antimatter reaction and use rather tiny ammount of energy to do it.

Defending a human agasint slow based lasers is easy.. and the human wont stand still.
Defending agasint flash also is rather easy, because they cause explosive damage, padding and thick material will offer good protection compared to the ammount of energy that the other guy has to expand to kill you.

Now you could create lasers that can kill a human though such protection, but the problem comes down to the ammount of energy you have to expend to defeat the protection compared to say a normal bullet.

Lasers if ever used to directly kill will most likely replace explosive based weapons... Laser systems designed for taking out artillery rounds and missiles are greatly improving in the last few years and attempting to get explosives though traditonal means to provide artillery based fire may force the use of laser systems even if they are not as effective.

Over time you would likely see them improve to the point where a aircraft with laser based weaponry would have more total destructive power then if it carried actual physical explosives.

Something else not talked about...
The energy storage problems.. you wouldnt want to be near a Cell thats capable of the quick discharge a laser weapon would need if it got hit.
At best it would be a all mightly massive EMP bomb(that would kill you and people near you aswell)... at worse it would be chemical reaction type cell and work just like an explosive.. with all that energy being released icreating a expanding shockwave of super heated plasma(kill everyone in a city block or more).

Imagine the chainreaction that would happen with 30-40 soldiers near each other as just ones power cell goes.

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Re: Imagining realistic energy weapons

Post by Tamren »

Hmm. So a laser rifle would have to be:

1. Either pulsed (or "flash") in operation. Or sufficiently powerful that momentarily touching a continuous beam would be damaging.
2. Have some advantage over existing projectile firearms. At least in a terrestrial environment.
3. Used with considerable eye protection.
4. Powered by an extremely dense and dangerous power source.

In regards to point one, assuming the beam could be made sufficiently powerful. Is there any reason why the weapon could not have multiple settings? One example in fiction I can remember had the laser rifles being used to cut open a large metal roof hatch that had been welded shut. This was done by making the rifles emit a continuous beam. But this effect is never mentioned in combat, presumably they were used in a pulsed mode.

Lasguns in Warhammer 40k are hardly the most realistic application of lasers in fiction. But apart from melee weapons, they are probably the most common type of weapon used on the battlefield. The reasons cited are that lasguns are cheaper to make and easier to resupply than comparable "autoguns". This is mostly because the power packs used can be easily recharged by direct sunlight or a source of heat. Now the logistics advantage is kind of arbitrary because it completely relies on the sophistication of your batteries. But the other cited reason is that lasguns (not having any moving parts) are extremely durable and hence easy to field strip and repair.

Would a laser weapon really be this easy to maintain? Lasguns take this to unrealistic extremes, continuing to function after being buried in mud or submerged in swamp water. Dust or damage to the focusing lenses would make the weapon unusable. Electronic components would have to be heavily shielded. And field repairs would be extremely difficult without a large supply of replacement parts. By comparison you can pick up an AK 47, whack it with a hammer as hard as you can, and it almost certainly will continue operating as if nothing happened.

The durability of the battery pack is suspect as well. Lasguns can reputedly sever the arm of an unprotected target with just a single shot. "High power" Or "Overcharged" powerpacks are supposedly good for 20 shots. That is a crapton of energy! They do incorporate some sort of safety mechanism because you don't see them detonate all over the place when their owners are horribly killed. But the one time a story depicted a loaded lasgun being deliberately sabotaged to overload itself. It managed to knock a hole in an enemy tank.

Oddly enough, I have never ever heard of eye protection being used in conjunction with laser weapons. Or any energy weapon for that matter. Basic polarized visors/faceplates are common, but certainly nothing like laser safety googles tuned to block specific frequencies of light. Laser "splash" off the target would probably make traditional magnifying optics unusable as well. If you can't see the beam, or where it hits, how exactly could you aim? Then again since lasers are completely accurate. A properly zeroed sight would point directly to the point of impact each time.

osmium
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Re: Imagining realistic energy weapons

Post by osmium »

I agree on the power packs, although you could sort of fluff it away saying that it was some sort of fuel cell with a built in recharge via either solar power or a heat engine. Such a device is horribly overengineered and likely to not be very economically viable, but not much is in the warhammer universe.

As for penetration that depends entirely on the power output and the absorption characteristics of the beam. An x-ray beam would completely penetrate the target, whereas a microwave beam would be severely concentrated in the outermost layer of skin. So it depends on what your goal is. A *very* high energy wide beam microwave laserbeam could conceivably explosively damage all of the skin on a target, whereas a carefully tuned beam designed to penetrate might say coagulate all the blood in a person (not sure how possible that is, but certainly it could cause incredible internal damage before the presence of the spot were detected).

For eye protection it really depends on the range at which you expect to use it, and if you're going to be viewing the target with a naked eye or through a special sight. If you expect to be close, it could be a problem, at long range I'd be somewhat less concerned especially because you can just put some filtering on the sight.

-O

Tamren
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Re: Imagining realistic energy weapons

Post by Tamren »

40k bucks the trend a bit in that the golden age of technology already happened. The power packs they use are highly sophisticated, but poorly understood. Probably the only reason the technology survived at all was because they were so ubiquitous.

Another example from fiction which is a little more realistic is the laser weapon tech depicted in UFO: Alien Invasion. The weapons are chemical lasers and the power packs are a sort of liquid flask containing the chemicals. They are good for about 10-20 shots, depending on the size of the weapon. The accompanying "fluff" is highly detailed and specifically mentions that the power packs are designed to be as durable as possible. And that the chance of a power pack being breached by enemy fire in combat is "a barely acceptable risk". In fact the spent power packs left lying around the battlefield are so toxic that after the mission is over, they apparently send a hazmat team in to collect them.

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Re: Imagining realistic energy weapons

Post by icekatze »

hi hi

In Eclipse Phase they use nuclear batteries to power beam weapons. Basically you fire some shots and then the battery slowly gets recharged by some kind of radioactive process. I'm not sure how much radioactive material you'd need to actually make that feasible though.

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Mjolnir
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Re: Imagining realistic energy weapons

Post by Mjolnir »

icekatze wrote:In Eclipse Phase they use nuclear batteries to power beam weapons. Basically you fire some shots and then the battery slowly gets recharged by some kind of radioactive process. I'm not sure how much radioactive material you'd need to actually make that feasible though.
It's not an unreasonable approach. RTGs and betavoltaic devices produce relatively small amounts of power, but produce it continuously for years on end and don't tend to explode, and you generally aren't firing your weapon continuously. Some tradeoffs though...a larger nuclear battery will recharge shots faster but be bigger, use more radioisotopes (meaning fewer nuclear batteries can be produced), and will produce more waste heat that has to be dealt with even when your batteries are fully charged. A smaller one will require more batteries to prevent the user running out at an inconvenient time. Another possibility along similar lines would be a microturbine generator capable of using common vehicle fuels in place of the atomic battery. Not limited by availability of radioisotopes, and you can shut the thing down when you're not recharging.

In terms of number of shots fired in a short period, the whole power supply will certainly be a lot bulkier and heavier than an equivalent number of shots in chemical ammunition. With the nuclear battery, though, if the rate of fire is lower than the recharge rate, the system can keep going for years, or as long as you have fuel with the microturbine approach. I still see it being mainly useful for things like mostly-stationary anti-artillery defenses due to the bulk and weight. (And note that the same power supply issues affect things like railguns that would be more directly useful against armored targets).

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