Laser vs UAV: No Fair Fight Here

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DeltaV
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Laser vs UAV: No Fair Fight Here

Post by DeltaV »

DEWs are rapidly reaching the size/weight/power needed for mounting on airborne platforms.

As I've often said in other threads, once DEWs become commonplace the aerial combat advantage will go to the larger platform.

UAV size and maneuverability will offer little advantage against lightspeed weapons fired from large platforms having plenty of electrical power and sensor aperture.

Laser vs UAV: No Fair Fight Here

ladajo
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Post by ladajo »

Back to the Glory Days of massively manned large bombers with gun turrets EVERYWHERE!

Warms my heart just thinking about it... 8)

ladajo
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Post by ladajo »


ladajo
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Post by ladajo »

Nd if you are interested, here is what Boeing syas they are up to in support of your government.

http://www.boeing.com/defense-space/ic/ ... erview.pdf

Tom Ligon
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Post by Tom Ligon »

Aw, lasers are easy to counter:

http://www.youtube.com/watch?v=lsO5j2Ui ... re=related

See, the thing about UAVs is that when the laser fries them, you don't have to write a sad letter to next of kin. Just get a new one out of the box. We'll gladly add another control system to the production run.

When the heavy bomber bristling with guns gets fried, you have to write ten letters and train a new crew. And the box is much bigger.

So what you do is launch several UAVs and some weapons systems backing them up. Missiles, for example. When the laser fries the UAV, the beam should be sufficiently bright to be detectible ... dust and humidity at least will glow. So the laser's location is known, and it will be gone in a few seconds.

Betruger
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Post by Betruger »

Tom Ligon wrote: So what you do is launch several UAVs and some weapons systems backing them up. Missiles, for example. When the laser fries the UAV, the beam should be sufficiently bright to be detectible ... dust and humidity at least will glow. So the laser's location is known, and it will be gone in a few seconds.
Now where've we seen this picture before... :D

ladajo
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Post by ladajo »

:D

DeltaV
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Post by DeltaV »

Tom Ligon wrote:So what you do is launch several UAVs and some weapons systems backing them up. Missiles, for example. When the laser fries the UAV, the beam should be sufficiently bright to be detectible ... dust and humidity at least will glow. So the laser's location is known, and it will be gone in a few seconds.
Let's see...
UAV speed at, say, Mach 2, is about 1500 statute miles per hour, or (1500 mi/hr)/[(186000 mi/s)(3600 s/hr)] = 0.00000224 c = 0.000224% light speed.
Missile speed at, say, Mach 4, is double that, at 0.00000448 c or 0.000448% light speed.

Ohhh yeahhhhh, the missile would win, hands down!

hanelyp
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Post by hanelyp »

The matter has been discussed at length at http://www.rocketpunk-manifesto.com in the context of space battles. One consideration is how fast a missile can reach a target vs. how fast the laser can disable the missile. Neither is instantaneous. If the missile can cool its skin with propellant headed to the engine, it may be able to last until after the fuel runs out.

Tom Ligon
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Post by Tom Ligon »

Lasers have the drawback of being easy to reflect. A shiny chrome missile would probably reject something like 98% of the heat from a laser. Nose cones are also typically considerably more rugged than UAV airframes.

True enough, light beams travel at the speed of light. Yes, you can put servos on a laser so it can swivel pretty quickly. But how fast can you acquire a target coming in from an unknown direction? How well can you detect small targets? How well can you hit small targets at a significant distance? That fast-moving laser is going to shake a little after a fast transit, probably enough to make it difficult to hit a 5" diameter target at a mile or more. So that means you may have just a couple of seconds to kill it. Do you have the power to get past a mirrored nose cone in that time?

I think laser weapons are neat and all that. I've wanted to see that mortar-shell defense capability since Viet Nam, when it was first discussed. But don't go thinking they're the ultimate weapon.

Back in the day there was some work going on using coupled lasers and plasma weapons. They'd found a plasma burst would stay tighter if it could follow a laser beam. A powerful laser made a channel of ionized air for the plasma to follow. Otherwise plasma cannon tended to be short range. Plasma is harder to shield against than lasers.

Luzr
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Re: Laser vs UAV: No Fair Fight Here

Post by Luzr »

DeltaV wrote:DEWs are rapidly reaching the size/weight/power needed for mounting on airborne platforms.

As I've often said in other threads, once DEWs become commonplace the aerial combat advantage will go to the larger platform.

UAV size and maneuverability will offer little advantage against lightspeed weapons fired from large platforms having plenty of electrical power and sensor aperture.
What makes you think that large plarform cannot be UAV?

DeltaV
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Re: Laser vs UAV: No Fair Fight Here

Post by DeltaV »

Luzr wrote:What makes you think that large plarform cannot be UAV?
It can, but, other parameters being more or less equal, the manned platform will have the added advantage of unpredictable human responses, intuition, strategic thinking, improvisation, etc.

The time-critical stuff, such as beam pointing, will of course have to be automated in either vehicle.

It's going to be a while (at least several decades) before AI reaches human levels of sophistication. I don't care what Kurzweil, Minsky, etc. say.

DeltaV
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Post by DeltaV »

Tom Ligon wrote:Lasers have the drawback of being easy to reflect. A shiny chrome missile would probably reject something like 98% of the heat from a laser. Nose cones are also typically considerably more rugged than UAV airframes.

True enough, light beams travel at the speed of light. Yes, you can put servos on a laser so it can swivel pretty quickly. But how fast can you acquire a target coming in from an unknown direction? How well can you detect small targets? How well can you hit small targets at a significant distance? That fast-moving laser is going to shake a little after a fast transit, probably enough to make it difficult to hit a 5" diameter target at a mile or more. So that means you may have just a couple of seconds to kill it. Do you have the power to get past a mirrored nose cone in that time?

I think laser weapons are neat and all that. I've wanted to see that mortar-shell defense capability since Viet Nam, when it was first discussed. But don't go thinking they're the ultimate weapon.

Back in the day there was some work going on using coupled lasers and plasma weapons. They'd found a plasma burst would stay tighter if it could follow a laser beam. A powerful laser made a channel of ionized air for the plasma to follow. Otherwise plasma cannon tended to be short range. Plasma is harder to shield against than lasers.
A variable-frequency laser (mini-FEL, admittedly not near-term, barring some classified breakthrough) would be better at finding reflectivity gaps. An x-ray laser wouldn't care. I was talking about DEWs in general, not just lasers.

Back in the mid-70s I was reading in the open literature about DoD particle beam projects such as Sipapu and White Horse. How far have they come in 35 years?

Active arrays used as weapons are now in the microwave range, but are likely to go T-ray, optical and maybe higher as nanotech advances. These have minimal beam-steering delays since no physical turret is being slewed. A conformal array on a large vehicle could deliver some serious power. They might even integrate it with active camouflage at various wavelengths.

Then there are sublight hypervelocity weapons such as rail guns and the plasma cannons you mentioned.

Lots of DEW possibilities.

mdeminico
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Post by mdeminico »

Tom Ligon wrote:But how fast can you acquire a target coming in from an unknown direction? How well can you detect small targets? How well can you hit small targets at a significant distance?
Very very fast, very very well, and very very well. Limited only by the precision created by the engineering that went into the system.

Acquiring, tracking, & aiming is relatively simple work for computers compared to other stuff.

And yes, I did see that tech you mentioned about the plasma riding the ionized beam created by a laser.

Regarding lasers, some frequencies are easy to reflect, others not so much. What reflects one frequency may absorb another. Laser-type weapons don't *have* to be limited to visible light.

Tom Ligon
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Post by Tom Ligon »

To hit an incoming 5-inch rocket at a mile requires an angular precision of about 0.079 milliradians.

I work routinely with a precision 2-axis positioning turntable. It resolves a circle into about 921,000 divisions, which is .0068 milliradians, or about 1.4 arc-seconds. Sounds pretty good. But if you look at the actual positioning repeatability of the payload in the machine under ideal lab conditions, with the machine bolted to a concrete floor, the truth is more like 15 arc-seconds, or 0.073 milliradians, just barely good enough to hit that target. And that's to get a quasi-static fixed angle ... it has to settle in for several seconds. We get 15 arc-second errors just from sunlight coming thru the windows heating the concrete floor unevenly.

Understand that Jupiter is a 40 arc-second disk in the night sky. Put a telescope on it some time and see just how much vibration you get if you even touch the scope. Now tell me you think you can get 90-degree in 0.1-second slew rates to lock in on a small target a mile away ... without allowing vibrations to settle out. Tell me you can do this on a vehicle with rubber tires on soft ground. Tell me you think an aircraft is sufficiently stable.

Yes, you can target a small object at a great range. We can manage the precision. Hell, our snipers are out to routine kills at something like 2600 meters now. But the precision needed to take out a 5" rocket (I believe this includes Hellfires and a number of others using the old HVAR rack), or a 6" artillery shell, will make it extremely challenging for rapid targeting at any kind of range.

That big bomber had better shoot first though, because it would be a much better target for a ship or ground-based laser.

How many of you guys have ever worked with small UAVs? The one in the link above was pretty damned close. But have you ever tried spotting or even hearing a Shadow 200 at 4000 ft? A Scan-Eagle at half that? Many is the terrorist who never knew he'd been spotted. And a GPS-guided bomb screaming in from a drop point 20 miles away? We've never bothered making those stealthy, but I bet it would not be hard.

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