Wavelength... Does It Matter If Power Is Equal For Scifi Directed Energy Weapons?

[Spacescifi]

Scenario: A scifi directed energy cannon is made for use on the battlefield.  Just small enough to fit inside the bed of a truck. Powerful enough to cut through an inch of steel every half second of sustained beaming.

Main Question: Choose your wavelength for maximum effectiveness on the battlefield.

You may choose radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, or gamma rays.
 

My pick: Microwaves. Good penetration and heating.

Versus Scenario: Assuming I had an armed ground force with twenty microwave cannons each as powerful as the OP (burns through an inch of steel every half second), would they have any advantage or disadvantage against an enemy force armed with directed energy cannons of the same power but using a wavelength other than microwaves?

 

Edited March 12 by Spacescifi

[RCgothic]

Those powers are not equal because equal power will not produce equal cutting of steel at different wavelengths.

Gamma would probably pass through the 0.5in steel without significant heating. Radio would probably reflect harmlessly.

 

[magnemoe]

I say visible to UV laser works best, easy to produce and you can run it trough mirrors who don't work for x-rays and above so you can have one laser supporting multiple turrets, not relevant here but very nice on an plane. 
Still you are just moving an telescope not an gun turret you could even have extended masts 
As in atmosphere range is not very relevant and assume multiple MW so you cut an hole in the air and you don't want to go to low but if you could make an very efficient IR laser it would make sense. 
 

[AckSed]

My choice: There's an atmospheric 'window' for a specific wavelength of IR, with something like 90% transmittance in the narrow 4-micron near-infrared band. (It says here humans radiate most warmth in the 10-micron band.)

More penetrating power can be achieved by pulsing the laser. In double-pulse laser-cutters, the first pulse excavates material and the second a nanosecond later prevents the ejecta from adhering to the side of the cut, presumably by keeping the vaporised material hot.

[Spacescifi]

  On 3/13/2025 at 2:55 AM, AckSed said:

My choice: There's an atmospheric 'window' for a specific wavelength of IR, with something like 90% transmittance in the narrow 4-micron near-infrared band. (It says here humans radiate most warmth in the 10-micron band.)

More penetrating power can be achieved by pulsing the laser. In double-pulse laser-cutters, the first pulse excavates material and the second a nanosecond later prevents the ejecta from adhering to the side of the cut, presumably by keeping the vaporised material hot.

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Interesting, so my army using masers would likely get wrecked if they faced off against yours with the I-lasers huh?

Since yours would deliver more heat to the target faster?

[AckSed]

Well, there's no one true wavelength. In the case of armour penetration with directed energy, visible to IR or UV wavelengths probably win.

There is, though, more than one way to disable a fighting vehicle. Microwave beams and masers have the advantage of absolutely messing up the electronics and radio signals of unshielded targets, which is an advantage for the new age of drone warfare, connected battlefields and minute-scale LEO satellite flyovers. It's often a lot easier if the targeting system for, say, their rocket artillery temporarily can't receive grid-square coordinates. It may only be for a few minutes, but... that may be all that's needed for your forces to acquire its grid square and drop something nasty.

Perun talks about DEW, and he makes a good show of what microwaves versus lasers are doing on today's battlefield:

We can assume that with something a bit more robust than a diesel generator, heat-causing and armour-penetrating will be more viable.

[Spacescifi]

  On 3/14/2025 at 3:38 AM, AckSed said:

Well, there's no one true wavelength. In the case of armour penetration with directed energy, visible to IR or UV wavelengths probably win.

There is, though, more than one way to disable a fighting vehicle. Microwave beams and masers have the advantage of absolutely messing up the electronics and radio signals of unshielded targets, which is an advantage for the new age of drone warfare, connected battlefields and minute-scale LEO satellite flyovers. It's often a lot easier if the targeting system for, say, their rocket artillery temporarily can't receive grid-square coordinates. It may only be for a few minutes, but... that may be all that's needed for your forces to acquire its grid square and drop something nasty.

Perun talks about DEW, and he makes a good show of what microwaves versus lasers are doing on today's battlefield:

We can assume that with something a bit more robust than a diesel generator, heat-causing and armour-penetrating will be more viable.

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Thanks will watch but have not yet

Armoured targets would be protected from lower powered masers. But at the point where you have a scifi melt steel laser the wavelength matters less... except for power perhaps? Meaning a steel melting gamma laser would be more of a power hog than just using a UV or infrared laser? Is that correct?

On another note, I am not sure we have the power to minaturize them, but if we could arm small drones with anti-drone masers then that would be perfect for drone defense.

[AckSed]

  On 3/14/2025 at 4:56 AM, Spacescifi said:

Armoured targets would be protected from lower powered masers. But at the point where you have a scifi melt steel laser the wavelength matters less... except for power perhaps? Meaning a steel melting gamma laser would be more of a power hog than just using a UV or infrared laser? Is that correct?

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Uh, pretty much - with unfortunate caveats. When thinking about weapons, you also have to think about the armour it's supposed to defeat and penetrate. Chiefly, armour, even future armour, isn't (only) steel, it's composite ceramic or some sort of super-alloy or aligned crystal handwavium. All of those will have differing absorption of microwaves, and induced eddy currents in metal will cause losses too.

Further, any armour that tries to cover all the bases will run into the rock/paper/scissors of weaponry: kinetic/explosive/directed-energy. Or slam/bang/burn if I'm being flippant. Fortunately for the armour-makers, or unfortunately if you're trying to come up with a One True Weapons System, none of these approaches are perfect.

Kinetic is your kinetic-energy: tungsten/depleted-uranium kinetic-energy penetrators, either fired from cannon with explosives like a pleb or fashionably-accelerated from a coilgun or rail gun at such velocities that most any armour will behave like clay. Downside is, the energy with which they leave the gun is all they are going to have, and most of the ways they disable involves secondary shrapnel inside the crew compartment. They also aren't that good against sloped armour and lightly-armoured targets;

Explosive is really another way to apply kinetic energy, either shattering plate with a really big bang or punching through with explosively-formed penetrators. This is the most mature weapons system, and also the one that has seen the most development against it in armour. Cannon need ammo, obviously, and have travel-time, but they deliver packets of focused kinetic energy to the target, on the cheap, ready to ruin someone's day. But as I said, there are approaches to counter most of these, from bar/slat/cage armour to Non-Explosive Reactive Armour, and we are approaching the limits of chemical explosives that can be safely handled;

Directed-energy is the one that is a solution in search of a problem, with practical difficulties we've roughly covered: power requirements, penetration, wavelengths in atmosphere (IR is better for going through atmosphere, UV is easier to focus down to a point), delivering the energy to be incident on the target, dealing with excess heat. They keep popping up because the advantages are that you don't need explosive ammo, they are reasonably good at penetrating metallic armour and the travel-time is the speed of light. The downside of this is that like any light, a simple mirror can reflect most of the energy.

More reading: https://toughsf.blogspot.com/2018/05/lasers-mirrors-and-star-pyramids.html

(For the past couple of years I have been diving into all sorts of armour theory, to link it up to real-life for a fanfic set in the tabletop universe BattleTech.  It has this good-against-everything armour and I'm finding it fascinating and frustrating.)

[Spacescifi]

  On 3/14/2025 at 1:17 PM, AckSed said:

Uh, pretty much - with unfortunate caveats. When thinking about weapons, you also have to think about the armour it's supposed to defeat and penetrate. Chiefly, armour, even future armour, isn't (only) steel, it's composite ceramic or some sort of super-alloy or aligned crystal handwavium. All of those will have differing absorption of microwaves, and induced eddy currents in metal will cause losses too.

Further, any armour that tries to cover all the bases will run into the rock/paper/scissors of weaponry: kinetic/explosive/directed-energy. Or slam/bang/burn if I'm being flippant. Fortunately for the armour-makers, or unfortunately if you're trying to come up with a One True Weapons System, none of these approaches are perfect.

Kinetic is your kinetic-energy: tungsten/depleted-uranium kinetic-energy penetrators, either fired from cannon with explosives like a pleb or fashionably-accelerated from a coilgun or rail gun at such velocities that most any armour will behave like clay. Downside is, the energy with which they leave the gun is all they are going to have, and most of the ways they disable involves secondary shrapnel inside the crew compartment. They also aren't that good against sloped armour and lightly-armoured targets;

Explosive is really another way to apply kinetic energy, either shattering plate with a really big bang or punching through with explosively-formed penetrators. This is the most mature weapons system, and also the one that has seen the most development against it in armour. Cannon need ammo, obviously, and have travel-time, but they deliver packets of focused kinetic energy to the target, on the cheap, ready to ruin someone's day. But as I said, there are approaches to counter most of these, from bar/slat/cage armour to Non-Explosive Reactive Armour, and we are approaching the limits of chemical explosives that can be safely handled;

Directed-energy is the one that is a solution in search of a problem, with practical difficulties we've roughly covered: power requirements, penetration, wavelengths in atmosphere (IR is better for going through atmosphere, UV is easier to focus down to a point), delivering the energy to be incident on the target, dealing with excess heat. They keep popping up because the advantages are that you don't need explosive ammo, they are reasonably good at penetrating metallic armour and the travel-time is the speed of light. The downside of this is that like any light, a simple mirror can reflect most of the energy.

More reading: https://toughsf.blogspot.com/2018/05/lasers-mirrors-and-star-pyramids.html

(For the past couple of years I have been diving into all sorts of armour theory, to link it up to real-life for a fanfic set in the tabletop universe BattleTech.  It has this good-against-everything armour and I'm finding it fascinating and frustrating.)

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Scifi seldom cares about the fact that the devils of physics are in the details.

Everytime I watch folks in Star Trek or Star Wars stand outside a window looking into space from their spaceship I cringe a bit inside. Knowing glass, even with lead or gold film added won't stop all radiative damage from flowing past the glass.

I honestly think if you wanted glass you could still see through to stop the radioactive soup of cosmic space, which includes cosmic rays (relativistic subatomic particles), you would have to rely on an actively powered system as opposed to a standard passive one.

Such as this:

Active Radiation Shield (ARS) window: Glass would have a middle pocket  filled with a dense gas like xenon that circulates  and is cleaned out of the particle rays it catches. A strong magnetic field would be configured to catch cosmic rays so they do not penetrate through to the base layer of glass, which passengers stand behind. Instead the dense gas would scatter them and the magnetic fields would catch the relativiatic particles which would be cleaned out the system some how.

A complex system? Sure. Which is why unlike Star Trek and Star Wars windows on spaceships will be few lol.

Unless you just don't have max radiation protection so you don't care, which is reality lol.

I mean really, all those windows are going to do is get you blinded by the unfiltered light of the sun anyway, which is why on the ISS they have sunshade panels to cover the windows because the sun is harsher to look at in space than it is here on Earth.

[AckSed]

Ah. So in all of these posts, you are using "scifi" as an euphemism for "uses handwave" or "unobtanium"?

*flinches* There is a continuum to these things, and I think you're doing the 'science' part of 'science fiction' an injustice. Especially when you ask for comments from people like me who - with a bit of generalisation - care about these details.

Do it if you wish, but please, please don't paint it all with the same brush.

Nerd-rant over.

[Spacescifi]

  On 3/14/2025 at 2:44 PM, AckSed said:

Ah. So in all of these posts, you are using "scifi" as an euphemism for "uses handwave" or "unobtanium"?

*flinches* There is a continuum to these things, and I think you're doing the 'science' part of 'science fiction' an injustice. Especially when you ask for comments from people like me who - with a bit of generalisation - care about these details.

Do it if you wish, but please, please don't paint it all with the same brush.

Nerd-rant over.

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Really to the masses they are one and the same. Many times people don't know the difference.

  On 3/14/2025 at 2:44 PM, AckSed said:

Ah. So in all of these posts, you are using "scifi" as an euphemism for "uses handwave" or "unobtanium"?

*flinches* There is a continuum to these things, and I think you're doing the 'science' part of 'science fiction' an injustice. Especially when you ask for comments from people like me who - with a bit of generalisation - care about these details.

Do it if you wish, but please, please don't paint it all with the same brush.

Nerd-rant over.

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Educated in science/space physics thoroughly are the minority... because ST and SW don't teach it.

Your mileage on all of that is better watching shows like The Expanse. Which I say looking forward to future scifi series that have not been made but will be similar to The Expanse.

[RCgothic]

With Gamma you might decide you don't need to defeat the armour. Just kill the crew. The amount of shielding required for protection from penetrating radiation would be prohibitive on all but the largest capital ships (good ol' square cube law).

Unfortunately such a capital ship would then be vulnerable to hypervelocity mass drivers. Too big and heavy to dodge.

Unfortunately gamma kills crew slowly over a period of weeks. A brief encounter could leave both ships intact but with both crews fated to an unpleasant death.

[Spacescifi]

  On 3/14/2025 at 8:08 PM, RCgothic said:

With Gamma you might decide you don't need to defeat the armour. Just kill the crew. The amount of shielding required for protection from penetrating radiation would be prohibitive on all but the largest capital ships (good ol' square cube law).

Unfortunately such a capital ship would then be vulnerable to hypervelocity mass drivers. Too big and heavy to dodge.

Unfortunately gamma kills crew slowly over a period of weeks. A brief encounter could leave both ships intact but with both crews fated to an unpleasant death.

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Depends on how good medical technology is I suppose. Since unlike machines biological systems can heal (up to a point anyway). Not saying they will ever be the same, but there just may be a way to slow the process or negate the ill effects enough that they can live years later on even if not a full lifespan.

[DareMightyThingsJPL]

  On 3/14/2025 at 8:08 PM, RCgothic said:

With Gamma you might decide you don't need to defeat the armour. Just kill the crew. The amount of shielding required for protection from penetrating radiation would be prohibitive on all but the largest capital ships (good ol' square cube law).

Unfortunately such a capital ship would then be vulnerable to hypervelocity mass drivers. Too big and heavy to dodge.

Unfortunately gamma kills crew slowly over a period of weeks. A brief encounter could leave both ships intact but with both crews fated to an unpleasant death.

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A few points of note:

As far as I know, we don't know how to make a gamma ray laser.

100,000 rem dose would be enough to instantly cause coma

[RCgothic]

Radiation poisoning effectively scrambles the biological programming of living cells, together with other assorted micro-damages.

The level of medical technology required to repair acute radiation poisoning after the fact is very, very high indeed.

Today's treatments effectively involve palliative care (which is problematic because morphine side effects exacerbate a lot of the symptoms of ARS) and hoping there's enough cellular machinery intact that the patient can pull through. 

A fatal dose is a fatal dose. 

To avert that would require the ability to detect and repair a significant majority of every molecular defect present within the patient.

That's so far beyond our current understanding it's not even funny.

Edited March 14 by RCgothic

[Spacescifi]

  On 3/14/2025 at 8:41 PM, RCgothic said:

Radiation poisoning effectively scrambles the biological programming of living cells, together with other assorted micro-damages.

The level of medical technology required to repair acute radiation poisoning after the fact is very, very high indeed.

Today's treatments effectively involve palliative care (which is problematic because morphine side effects exacerbate a lot of the symptoms of ARS) and hoping there's enough cellular machinery intact that the patient can pull through. 

A fatal dose is a fatal dose. 

To avert that would require the ability to detect and repair a significant majority of every molecular defect present within the patient.

That's so fast beyond our current understanding it's not even funny.

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Basically Star Trek level medical then.

Which is paradoxical because either Picard is proud of his shiny bald head or they still have not cured male baldness.

[DeadJohn]

  On 3/14/2025 at 9:27 PM, Spacescifi said:

Which is paradoxical because either Picard is proud of his shiny bald head or they still have not cured male baldness.

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I recall hearing an interview with Star Trek crew where that was addressed. Their society doesn't care about baldness so there's nothing to "cure". I don't recall if that ever made it into an episode or was just behind the scenes talk.

[Shpaget]

  On 3/18/2025 at 2:34 PM, DeadJohn said:

Their society doesn't care about baldness so there's nothing to "cure". I don't recall if that ever made it into an episode or was just behind the scenes talk.

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In ST VOY, EMH is teased multiple times regarding the baldness, along with dr. Lewis Zimmerman.

Going back to the topic, just look at the industrial lasers. For cutting metal, fiber lasers which operate at around 1 000 nm are used. For acrylic, wood, leather etc. CO2 lasers are used (around 10 000 nm). While both are infrared, CO2 is very poor at cutting metal, and fiber is poor at cutting wood and acrylic. There is very little overlap in their application. Different mterials have vastly different absorption characteristics.

[magnemoe]

  On 3/14/2025 at 8:08 PM, RCgothic said:

With Gamma you might decide you don't need to defeat the armour. Just kill the crew. The amount of shielding required for protection from penetrating radiation would be prohibitive on all but the largest capital ships (good ol' square cube law).

Unfortunately such a capital ship would then be vulnerable to hypervelocity mass drivers. Too big and heavy to dodge.

Unfortunately gamma kills crew slowly over a period of weeks. A brief encounter could leave both ships intact but with both crews fated to an unpleasant death.

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One downside assuming we are still on ground to air defense. Its no crew unless some idiot try to strafe you. Shells, and missiles will be pretty homed in. so if targeting system fails correctly it will be ballistic trajectory from now and still pretty accurate And that gamma rays is questionable, you can make an xray laser but hard and no mirrors.  
Note nuke pumped x-ray lasers for local air defense is like close air support by the deathstar. 

[Spacescifi]

  On 3/18/2025 at 9:42 PM, magnemoe said:

One downside assuming we are still on ground to air defense. Its no crew unless some idiot try to strafe you. Shells, and missiles will be pretty homed in. so if targeting system fails correctly it will be ballistic trajectory from now and still pretty accurate And that gamma rays is questionable, you can make an xray laser but hard and no mirrors.  
Note nuke pumped x-ray lasers for local air defense is like close air support by the deathstar. 

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Sad thing is Star Wars actually did this lol. During the battle of Endor the Death Star must have throttled down it's shot power a bit, since it was shown one-shotting rebel capitol ships during the fleet battle while Imperial allied ships were nearby fighting them.

Edited March 18 by Spacescifi

[DeadJohn]

The introduction of energy weapons will be met by corresponding developments in armor. It's much like the modern armor situation where tanks have multiple layers of different armor types to negate different attacks. One side researches a wavelength for their energy weapon, the other side researches armor against that wavelength.

Energy weapons might eventually be very effective defense against aircraft. Aircraft are more constrained by weight than are tanks, so you can't just stack new armor layers on a plane. Energy weapons also have near-instant flight time which solves the problem of planes dodging/countermeasuring slow missiles.

Edited March 18 by DeadJohn

[Spacescifi]

  On 3/18/2025 at 11:48 PM, DeadJohn said:

The introduction of energy weapons will be met by corresponding developments in armor. It's much like the modern armor situation where tanks have multiple layers of different armor types to negate different attacks. One side researches a wavelength for their energy weapon, the other side researches armor against that wavelength.

Energy weapons might eventually be very effective defense against aircraft. Aircraft are more constrained by weight than are tanks, so you can't just stack new armor layers on a plane. Energy weapons also have near-instant flight time which solves the problem of planes dodging/countermeasuring slow missiles.

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Not to mention frying the 20/20 vision all good pilots need to even get hired on.

Transition to full on effective laser air defense and we may end the role of the fighter pilot in favor of AI and drones.

I know people are not comfortable with the idea of killer AI aircraft, but the day lasers start dominating aerial defense I am not sure there will be any other effective options against them. Harder to blind an AI or drone craft than a human. A camera can look at the sun and not go blind... the human eye other is another story.

War is hell and flesh is weak. That's never changing. We have gone from protecting ourselves with weapons to putting armor upon ourselves, and finally we will have to choose to either make more disposable AI or drones than our opponents can make or settle for good armor.

Offense and having more supply tends to always win out if going by the war in Europe is any indication (let's not get political or put fault to anyone lest the thread get banned).

Defense has an expiration date and will always be breached. It only helps if you have reinforcements coming before it fails or before your opponent's reinforcements arrive.

Edited March 19 by Spacescifi

[magnemoe]

  On 3/18/2025 at 11:48 PM, DeadJohn said:

The introduction of energy weapons will be met by corresponding developments in armor. It's much like the modern armor situation where tanks have multiple layers of different armor types to negate different attacks. One side researches a wavelength for their energy weapon, the other side researches armor against that wavelength.

Energy weapons might eventually be very effective defense against aircraft. Aircraft are more constrained by weight than are tanks, so you can't just stack new armor layers on a plane. Energy weapons also have near-instant flight time which solves the problem of planes dodging/countermeasuring slow missiles.

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I say that lasers against tanks is order of magnitude harder than planes and missiles. Not only the power requirement to get trough armor on an moving target but also that lasers is line of sight so the tank can shoot back. 
Most effective weapons against lasers is probably artillery, if needed make the warhead stealthy, or some sort of stand off glide bomb. 

An high attitude plane with an good laser is another problem, see no other counter here than an good laser. Its not like you can stealth an anti air missile. You could stealth an interceptor drone but it would not be very fast.