Witness the firepower of this armed and operational...

Witness the firepower of this armed and operational...

Postby Mikey » Fri Mar 06, 2015 11:34 am

... test platform? Lockheed has successfully tested an anit-machine laser weapon.
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Re: Witness the firepower of this armed and operational...

Postby Graham Kennedy » Fri Mar 06, 2015 1:24 pm

I notice that they don't say how long it took.

The heat capacity of Iron is 0.45 J/g/K. So heating 1 kg or Iron by 1K takes 450 J. The melting point of Iron is 1811K, so to heat it to that from room temp of 293K would take (1811-293)*450 = 683,100 J.

So to heat 1 Kg of iron to melting point would take a 30 kW laser about 23 seconds, minimum.

And this is just to reach the melting temp, not to actually melt the iron. How much energy that takes varies according to the type of iron, but around 130 kJ per kilo seems to be in the right ballpark, so another 4+ seconds. And that's per kilo... I wonder how many kilos of car they have to heat/melt to guarantee stopping it?

And that all ignores whatever the atmospheric losses are, and assumes you can keep your laser perfectly aimed at a given point (me, I'd be weaving the truck from side to side if somebody was shooting a laser at me. I'd also cover it in kitchen foil or silver paint before I set out.)

Personally I don't find a weapon that has to dwell on the target for 25+ seconds to do that amount of damage all that impressive.

And of course if it's raining or foggy, your laser is probably next to useless. Good job we mostly fight in the desert these days, I guess.
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Re: Witness the firepower of this armed and operational...

Postby Mikey » Sat Mar 07, 2015 5:53 am

Other reports merely say that the dwell time on target was "a matter of seconds." Other than that, I'm not involved in the project so I can't answer your questions. I can tell you that one of the ideas of Lockheed's "spectral beam combining" is to help obviate atmospheric losses, and that it apparently isn't intended for use on targets as large as a small truck.

I'm not sure I understand why you're using 1kg of iron for your example, though. To incapacitate a UAV - for example - would require an amount of material damage far less than the equivalent of melting 1kg of iron.
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Re: Witness the firepower of this armed and operational...

Postby Graham Kennedy » Sat Mar 07, 2015 9:51 am

Using 1kg just as an example. Yes, absolutely taking out a UAV would be easier, but they're demoing it on a truck. If you're going to kill a truck you need to do damage to a chunk of engine, which is likely to take at least 1kg worth.

I don't want to be a killjoy, I just don't get the hype about laser weapons when they don't seem up to the jobs that guns currently do.
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Re: Witness the firepower of this armed and operational...

Postby Captain Seafort » Sat Mar 07, 2015 10:06 am

Graham Kennedy wrote:I don't want to be a killjoy, I just don't get the hype about laser weapons when they don't seem up to the jobs that guns currently do.


Because they have the potential to reap huge advantages - vastly reduced ammunition requirements, not affected by gravity, strike effectively instantaneously, etc. I expect a lot of Edward III's commanders were a bit dubious about his decision to take those weird metal tube things with him for his 1346 Normandy campaign. Of course, they might have been right, and they certainly played an insignificant role at Crecy, but they got better.
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Re: Witness the firepower of this armed and operational...

Postby Mikey » Sat Mar 07, 2015 11:16 am

Captain Seafort wrote:not affected by gravity


That's a much bigger factor than most people would think, considering that one of the main intended uses for this type of weapon is from a high-altitude platform and the horizon becomes a real issue.
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Re: Witness the firepower of this armed and operational...

Postby Graham Kennedy » Sat Mar 07, 2015 5:14 pm

Captain Seafort wrote:Because they have the potential to reap huge advantages

Sure, the potential. But from what I've seen of these demonstrations, that potential is a long way from being fulfilled. Stories like this make it seem like practical laser weapons are just around the corner. I suspect we won't see them for decades to come, if then.

But time will tell.
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Re: Witness the firepower of this armed and operational...

Postby Mikey » Sat Mar 07, 2015 11:37 pm

No, stories like this merely report on the state of the test. If nobody performed a test like this, then nothing would ever be developed ever.
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Re: Witness the firepower of this armed and operational...

Postby Graham Kennedy » Sat Mar 07, 2015 11:40 pm

Mikey wrote:No, stories like this merely report on the state of the test. If nobody performed a test like this, then nothing would ever be developed ever.

"Laser weapons might finally be here."
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Re: Witness the firepower of this armed and operational...

Postby sunnyside » Sun Mar 08, 2015 2:40 am

There is all this emphasis on taking down vehicles. But I'd bet they'd settle for even slightly damaging an incoming missile. I couldn't see it taking that much to mess up its forward sensors.

Also as an American I'd be quite happy with a system that would let us have zero collateral damage airstrikes. Lasers might well be what makes that a reality. Sure at the ranges they're talking we have gun systems that can reach out that far, but those systems also tend to splatter anybody in the vicinity and unless (or even if) they're explosive they might sail through a wall and blow up some kids.

But I can appreciate that a truck makes for a cool demo while blowing up a pigs head might not quite grab the headlines in such a positive way..
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Re: Witness the firepower of this armed and operational...

Postby McAvoy » Sun Mar 08, 2015 5:36 am

I want a fricking gatling laser gun
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Re: Witness the firepower of this armed and operational...

Postby Mikey » Sun Mar 08, 2015 11:22 am

Graham Kennedy wrote:
Mikey wrote:No, stories like this merely report on the state of the test. If nobody performed a test like this, then nothing would ever be developed ever.

"Laser weapons might finally be here."


Ah, I see the confusion. In England they must not have introductory taglines and everything in the history of ever has been entirely literal with no authorial techniques. Seriously, using an intro line like that to engage interest in the body of the article is a writing skill my daughter learned in 4th grade (age 9.)
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Re: Witness the firepower of this armed and operational...

Postby Graham Kennedy » Sun Mar 08, 2015 1:12 pm

I think it's that writers here have even advanced enough that some of them can write taglines (and conclusions) and without hugely exaggerating.
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Re: Witness the firepower of this armed and operational...

Postby Mikey » Sun Mar 08, 2015 3:33 pm

Graham Kennedy wrote:I think it's that writers here have even advanced enough that some of them can write taglines (and conclusions) and without hugely exaggerating.



As they did. Let's see:
"Laser weapons might finally be here."

Hmm. I see nothing about "laser weapons ready for general deployment," "laser weapons fully operational within intended mission parameters," or even "laser weapons are perfected." As it stands it appears that it's less of a case of "...some of them can write taglines (and conclusions) and without hugely exaggerating," and more a case of "readers over here can understand an intention without it being spoon-fed to them."
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Re: Witness the firepower of this armed and operational...

Postby Captain Seafort » Sun Mar 08, 2015 4:21 pm

There is all this emphasis on taking down vehicles. But I'd bet they'd settle for even slightly damaging an incoming missile. I couldn't see it taking that much to mess up its forward sensors.


Anti missile/shell lasers are a lot more advanced - indeed, I think the Israelis have a couple of Iron Beam instillations already in service.

Mikey wrote:I see nothing about "laser weapons ready for general deployment,"


Really? How else would you interpret that statement in the absence of running the numbers to realise that the required dwell time is far too long for an operational system? Even if you're being charitable, the tone of the article is that the next step is to go from prototype to operational model, rather than scaling up the proof of concept rig to something that can get the job done in a reasonable time (which I'd guesstimate as at 100+ kW). This is certainly an important step forward, but no more than that, and certainly not enough of one to say that anti-vehicle lasers are "here".
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