What can counter Laser weapons? MKII

[sjwt]

I appreciate the lot of answers countering my simple mirror idea. Do tell me though, how come laser weapons aren't widespread now? Powerful lasers have been around for a while. If there wasn't an easy counter, they would be in use now, no? Yes, in space warfare speed (or rather, sharp changes of the vector) is the key. See, I watch Discovery too... How about other possible spheres of military application? There is some easy counter. IMHO, it is exactly that - reflective surfaces.

Simple,Size Heat and power.. You need a lot of power, and size to radiate the heat away.

Here is a nice 10kw ''portable'' laser.. its a good 10 fold too low powered to be of major use..

http://defense-update.com/20131214_us-army-tests-high-power-laser-weapon.html

The test system going on a warship this year is in the "15-50KW range".. Able to set test drones on fire, though I'd like to know what they are made of.

http://news.yahoo.com/navys-laser-weapon-blasts-bad-215808231.html

[sjwt]

Yes, but the sun is powerful, and is used for Solar Sails.........

Lasers are just extremely focused, less erratic.

But the point you're missing is Solar sails are not made of some magic exotic metrical, they work in the range of 9.08 μN per square metre (9.08 μPa), thats right Micronewtons per Square meter. They don't power up a 100TW laser and shoot to kill with power measurement in K-Watts per Square meter, they *theoretically* focus a laser to about Solar output. Now at long interstellar distances, then you need a powerful laser to get your force out that far, but close up you dont get fast you get burn though. The material used has a weight in the 5 grams per Square meter and under range. Tissue paper is usually under 20 grams Square meter.

[KASASpace]

But the point you're missing is Solar sails are not made of some magic exotic metrical, they work in the range of 9.08 μN per square metre (9.08 μPa), thats right Micronewtons per Square meter. They don't power up a 100TW laser and shoot to kill with power measurement in K-Watts per Square meter, they *theoretically* focus a laser to about Solar output. Now at long interstellar distances, then you need a powerful laser to get your force out that far, but close up you dont get fast you get burn though. The material used has a weight in the 5 grams per Square meter and under range. Tissue paper is usually under 20 grams Square meter.

Are we forgetting those solar sails that are capable of "thrust to mass" ratios of greater than 1.

And could you be more clear? I didn't exactly understand all of what you said. You made it sound like they "power" the laser, at east in how I read it (sorry about that).

And I'm quite sure that Solar Sails are "super" mirrors, effectively the best your'e gonna get.

But we would something that disperses light........... either that or is strong enough to absorb it.

Smoke could work.

[Kryten]

Well I mentioned them because of the fact that they can actually use lasers to be propelled. It's an ultra-thin mirror, so the light-pressure (it exists!) is used.

Plans to use lasers to propel light sails involve lasers deliberately built to produce huge spot sizes at the ranges the sail would be intended to used at; it's not a comparable situation to use of lasers as weapons.

[KASASpace]

Plans to use lasers to propel light sails involve lasers deliberately built to produce huge spot sizes at the ranges the sail would be intended to used at; it's not a comparable situation to use of lasers as weapons.

Well, considering modern technology it would probably be a not so super weapon yet. So mirrors (and because solar sails are mirrors) might help in this instance. However you are correct.

In the far future though......... good luck using mirrors.

Admittedly it won't help much.

Edited February 10, 2014 by KASASpace

[sjwt]

Are we forgetting those solar sails that are capable of "thrust to mass" ratios of greater than 1.

No, infact they have an extremely low twr but an infinite ''burn time''... are we forgetting that once in orbit outside of the atmosphere and in orbit you need a twr of greater than 0 to get movement. Its only under a gravity well under orbital speeds that you need a twr of more than 1.

Take for example this Ion engine probe Dawn . Total weight 1,240KGS, total Thrust 90mN. thats a TWR of might as well be 0.

Lightsail1 is accelerating at 0.06 mm per second per second on a 4.5kg ship, or half the thickness of a piece of paper every second.

Or for a Kerbal analogy, the Ion Engine in game with no fuel, no power source and no other parts, just the engine on its self has a TWR of 0.2

And I'm quite sure that Solar Sails are "super" mirrors, effectively the best your'e gonna get.

quite the opposite, they are designed to be as light as possible within a decent reflective range, you want a supper 99.999999999999999999999% reflective full band mirror? It will weigh in at Tons per Square meter as opposed to grams. equaling a million fold decrease in your low TWR to begin with.

But we would something that disperses light........... either that or is strong enough to absorb it.

We just do not have super light wight super reflective full band materials..

Smoke could work.

Once more we are down to A) absorption or Reflection, smoke absorbs light, hence you are vaporizing the small particles of whatever the smoke is made from..

The laws of thermodynamics will always apply, you will not get a Material that will reflect 100%, and nothing can absorbed the energy for ever.

Edited February 10, 2014 by sjwt

[Clockwork_werewolf]

I think without knowing the power or duration of the laser burst you can never fully counter it. It ends up being like asking us to stop the sun heating up a ship parked a meter from it's surface, all we can do is make it take longer.

That being said I think multiple layers of mirrors each set to reflect a different wave length, combined with a very fast spinning hull with a second internal hull that does not spin. The laser shouldn't be able to dump much heat into any one area and it shouldn't be able to get past the mirror set to its frequency. I realise enough laser bursts on enough frequency's would still be able to get past the layer with each hitting the areas opened up by other bursts but that's why I said point one.

Another way might be just to use a very good heat dissipation system where you use a material with a high heat conductivity with a layer of fast liquid coolant below it. You might even be able to combine systems one and two together so you have a spinning mirror, conductor, dissipation shell.

[Seret]

I appreciate the lot of answers countering my simple mirror idea. Do tell me though, how come laser weapons aren't widespread now? Powerful lasers have been around for a while. If there wasn't an easy counter, they would be in use now, no? Yes, in space warfare speed (or rather, sharp changes of the vector) is the key. See, I watch Discovery too... How about other possible spheres of military application? There is some easy counter. IMHO, it is exactly that - reflective surfaces.

Simply because lasers don't make particularly good weapons. For the same weight and volume you can get a lot more stowed kills on board your tank/aircraft/spacecraft by using chemical energy. Just look at something like a tank gun, each round of a 120mm gun has about 12MJ of muzzle energy and a good crew could get off as many as 10 rounds a minute (at least initially). That's equivalent to 2MW; and there's no way you could get a 2MW power source into the space available under armour in a tank (power packs in modern tanks are rated at about 1MW, and most of that is used to move the thing)

Lasers are used extensively in warfare, but mostly in fire control systems (as rangefinders) or as target designators.

[KASASpace]

No, infact they have an extremely low twr but an infinite ''burn time''... are we forgetting that once in orbit outside of the atmosphere and in orbit you need a twr of greater than 0 to get movement. Its only under a gravity well under orbital speeds that you need a twr of more than 1.

Take for example this Ion engine probe Dawn . Total weight 1,240KGS, total Thrust 90mN. thats a TWR of might as well be 0.

Lightsail1 is accelerating at 0.06 mm per second per second on a 4.5kg ship, or half the thickness of a piece of paper every second.

Or for a Kerbal analogy, the Ion Engine in game with no fuel, no power source and no other parts, just the engine on its self has a TWR of 0.2

quite the opposite, they are designed to be as light as possible within a decent reflective range, you want a supper 99.999999999999999999999% reflective full band mirror? It will weigh in at Tons per Square meter as opposed to grams. equaling a million fold decrease in your low TWR to begin with.

We just do not have super light wight super reflective full band materials..

Once more we are down to A) absorption or Reflection, smoke absorbs light, hence you are vaporizing the small particles of whatever the smoke is made from..

The laws of thermodynamics will always apply, you will not get a Material that will reflect 100%, and nothing can absorbed the energy for ever.

Some guy went to work making TWR solar sails greater than 1, however the mirrors were so fragile you could not launch them into space.

And solar sails are designed to use the light pressure as thrust. So it has to be a "super-mirror" that takes in a lot of light.

"We" don't have anything to counter lasers, except for a super high gravity field but chances are the enemy has the ability to calculate where to aim.

Of course we could use two ships, one is a decoy, that orbits out in front of the other ship, and takes the laser blast. Now, assuming that the laser will need a cooldown time, we could easily do that. (yeah, it's expensive to get it there)

smoke is used to block light of many kinds, and lasers could possibly be "jangled' so they lose their focus.

[Kryten]

And solar sails are designed to use the light pressure as thrust. So it has to be a "super-mirror" that takes in a lot of light.

No, it needs to maximise TWR. Let's say you have two mirrored materials; the first reflects 70% of the incident light, and the second is a ' super-mirror' that reflects 99%-and weighs twice as much. Which is going to be more effective?

[KerbMav]

As repeatedly some kind of Unobtanium gets mentioned, I might as well through "bend the space between you and your enemy" into the room.

I think a smoke screen is a viable way to either "sit it out" until the enemy has to reload/cool down or while waiting for your own attack to hit or you are able to escape by finding cover or getting out of range (at some point heat resistant armor can take over until you are to far away for the tracking system to keep the beam targeted.)

It may "boil down" (hah!) to run out the clock.

[John Crichton]

I know this has probably been mentioned before...but a mirror will do the trick

[KASASpace]

No, it needs to maximise TWR. Let's say you have two mirrored materials; the first reflects 70% of the incident light, and the second is a ' super-mirror' that reflects 99%-and weighs twice as much. Which is going to be more effective?

Ultra-thin, ultra-reflective.

You need to harness the most light-pressure.

[KASASpace]

I think we need to deflect the lasers, rather than reflect.

So steep sides akin to the F-117, although probably some kind of mirror-esque material.

[Kryten]

Ultra-thin, ultra-reflective.

Is impossible. You can optimise for one or the other, not both.

I think we need to deflect the lasers, rather than reflect.

Those words mean the same thing.

[KASASpace]

Is impossible. You can optimise for one or the other, not both.

Those words mean the same thing.

Well, I haven't built a solar sail, so you may be right about that.

Reflect and deflect are not the same thing. In the case of light/lasers there is a difference. Deflect changes course, but reflect shoots it back in the same general direction.

[rdfox]

There is no difference. Deflection and reflection are the same thing; it's just that deflect is normally used for physical objects, and reflect for wave phenomena. "The angle of incidence is equal to the angle of reflection" is equally true in both cases.

[KASASpace]

There is no difference. Deflection and reflection are the same thing; it's just that deflect is normally used for physical objects, and reflect for wave phenomena. "The angle of incidence is equal to the angle of reflection" is equally true in both cases.

Actually no. Deflect means change direction in this context, whereas reflect means to send it back in the same general direction in this context.

[Kryten]

Actually no. Deflect means change direction in this context, whereas reflect means to send it back in the same general direction in this context.

How are those any different? How is something supposed to be 'sent back in the same general direction' without changing direction?

[KASASpace]

How are those any different? How is something supposed to be 'sent back in the same general direction' without changing direction?

Well, they're similar.

It's in a way like how Perfect Conductors aren't Superconductors.

A Perfect Conudctor has a magnetic flux of nonzero OR zero, whereas Superconductors is zero.

Change direction to ANY direction, not sent back in the same general direction like mirrors when facing straight.

[Lightning22]

If we're assuming that this is occurring in space, we should consider more than on defense, it's clear that there is no single catch-all, mirrors are really only good for certain wavelengths and any smokescreen used to diffuse the beam would also encounter the same problem, ECM can only get you so far, and shooting first isn't always an option due to rules of engagement. So to prioritize, ECM and stealth would be the first choices, you can't hit what you can't "see". Next would be the plan B passive defenses, some way to absorb and perhaps radiate the heat out of the craft, as mentioned, this wouldn't be possible for the entire craft, but if you can keep the sensitive parts out of the beam you might last long enough to break the target lock, or eject in a smaller pod. Finally a plan c, I'm thinking something similar to chaff, similar in material to what is presently used to befuddle radar, only in space, not only do you have a cloud of fine metal to hopefully diffuse the laser, depending on your release method, you also have a very fine cloud of metal hurtling towards your attacker. This would probably be completely last ditch due to the very high improbability of actually catching the beam and the fact that it endangers not only the craft deploying it, but every future vessel to pass through the orbit you just put that cloud of metal in.

[jwenting]

Actually no. Deflect means change direction in this context, whereas reflect means to send it back in the same general direction in this context.

Physically there is no difference. Both have the same effect, energy is transferred to the reflective surface.

Even in your warped "definition", reflection is just a special case of reflection. Which should tell you all about how utterly irrelevant the distinction is except when it comes to efficiency when trying to induce thrust.

[KASASpace]

Wait wait wait.

So, if a laser damages by heat buildup, then wouldn't the ship with a higher capacity for heat buildup win?

So, why not have a crap ton of large heatsinks, connected to the outer extremities of the craft via a heat conductive material and having a few heat sinks near the extremities.

[Rakaydos]

Wait wait wait.

So, if a laser damages by heat buildup, then wouldn't the ship with a higher capacity for heat buildup win?

So, why not have a crap ton of large heatsinks, connected to the outer extremities of the craft via a heat conductive material and having a few heat sinks near the extremities.

the real problem is that firing the laser produces more heat than being hit by the same laser. Therefore it's only practical to have laser weapons mounted on things with more heat tolerance than their intended targets. IE: An asteroid base that can dump it's heat into the nickle-iron, shooting at a missile which has a heat producing reaction engine and tanks of explosive fuel.

[KASASpace]

the real problem is that firing the laser produces more heat than being hit by the same laser. Therefore it's only practical to have laser weapons mounted on things with more heat tolerance than their intended targets. IE: An asteroid base that can dump it's heat into the nickle-iron, shooting at a missile which has a heat producing reaction engine and tanks of explosive fuel.

True, but there are lasers that put the heat into one gas and eject all the gas. That's why you would need to get more gas (like something along the lines of Argon)