Real-life laser weapons continue to inch closer to reality. Two recent examples: Raytheon says its “prototype solid-state Laser Area Defense System (LADS) successfully detonated 60-millimeter mortars.” And Northrop Grumman is opening up a new “directed energy production facility” for building high energy, solid-state lasers.
Raytheon’s announcement is interesting, because solid-state, electric lasers haven’t yet hit the 100 kilowatt threshold which many people consider to be the minimum strength for weapons-grade lasers. (They’re not too far off, though.) But Raytheon says they zapped these mortars using “an a proven, existing, off-the-shelf solid-state laser, coupled with commercially available optics technology.“
So how did the company pull it off? I got a non-answer from a company flack, something about “view[ing] the problem from the user point of view.“
Now, this was a very limited test. These mortars were small — just 60 mm. The company wouldn’t say how long they were zapped (even a weak laser can bore holes in metal, given enough time). And the mortars were on the ground, around 550 yards away, not flying through the air. But this LADS is built on the back on Raytheon’s 4,500-round-per-minute Phalanx gun, which is already knocking down mortars in Iraq. So presumably, the targeting and tracking piece is won’t be that hard to manage. In-air tests of the laser are planned for later this year.
Meanwhile, Northrop has opened up a new facility, south of Los Angeles, to build what the company hopes is the world’s first 100 kilowatt, solid-state laser. It’ll start by putting together the series of 32 garnet crystal “modules” that form the heart of the system. Shine light-emitting diodes into ‘em, and they start the laser chain-reaction, shooting out focused light. Combine all those beams into one, and you’ve got yourself a battlefield-strength ray. The array is similar to what Northrop used in its 25 kw demonstrator. But the gum-stick-sized crystals have been shrunk by about 50% — part of the company’s effort to make the laser small and rugged enough for war zone use.
50 people should be hired over the next year in the new facility. Company officials say they’re still on track on demonstrate their 100 kw laser by the end of next year. If everything works according to plan, there should be enough room in the new building to simultaneously build and test three weapons-grade lasers at once.
Electric Lasers Shoot Mortars, Gain Strength
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Presumably, one doesn’t need to cut through the metal. Simply heating the metal to the point where internal explosives ignite would be enough.
This would presumably not be terribly scale dependent. If the thermal conductivity of the metal between the surface and explosive in a 155mm mortar round really that much greater than in a 60mm mortar round? Indeed, the larger round would present a larger target, which might compensate for a somewhat longer heating time.
We must also keep in mind that an artillery or mortar round is spinning (usually) when in flight. This would complicate efforts to heat the metal sufficiently to cut through.
Hey Grendel, what’s the photon momentum in the beam? Kinetic kill my ass.
Actually, photons have zero mass but do have momentum. The magnitude of the momentum of a photon is given by
p=h*nu/c
where h is Planck’s constant, nu is the frequency, and c is the speed of light.
Actually, photons are not "attracted to the sun".
They appear to bend around the sun and other large objects (as seen with gravitational lensing), however this is not due to mutual gravitational attraction.
The light appears to bend because it is actually travelling a straight path through space-time. Because large masses, such as a star, warp space-time around them, they have the effect of bending the apparent light path.
Hope this helps
photons DO weigh something, sorry. They are visibly attracted to the sun
OK, physics lesson time.
Photons have no rest mass. The could not travel at the speed of light if they did. They DO have both energy and momentum. They are attracted to gravitational mass (e.g. they bend towards the sun) but this is true even though they do not have mass.
http://en.wikipedia.org/wiki/Photon
Here comes the math. Assume a frequency of 3E14 Hertz (which is a good frequency for passing through the atmosphere and adaptive optics is easiest at this frequency). Each photon has an energy of 1.98E-19 Joules and a momentum of 6.62E-28 kilogram*meter/second.
A 100 KW laser firing a 1 second pulse (generous, the pulse is probably shorter) fires off 1E5 joules or 5E23 photons. The entire momentum in the beam is 3E-4 kilograms*meters/second.
A typical 2 gram rifle bullet with a typical 1000 meter/second exit velocity has a momentum of 20 kilogram*meter/second, roughly 66,000 times more momentum than the 100 KW laser beam.
So laser weapons are not kinetic kill weapons. There is not enough momentum in the beam. Even the largest lasers in the world don’t have the momentum of a single AK47 round. They do their damage thermally, so spinning targets and reflective surfaces are a problem.
100 kw laser is nothing. In the book “Solid State Lasers for the Laser Enthusiast” by Daniel Gregory, he provides information on how to build a laser using an Nd:Yag rod with q-switching. One use a 3mm x 50mm rod and the other uses a 6mm x 76mm rod. I believe the bigger rod produces a 16 Megawatt beam and the smaller is around 2 Megawatts. Either of which far exceeds 100 Kilowatts. Here is the website for his company:
http://www.americanlasertechnic.com/index.htm
check out the late paul marmet http://www.newtonphysics.on.ca/info/author.html for the real spin on the photon.
particularly spend some time with the article on the fundamental nature of the electron.
http://www.newtonphysics.on.ca/
article 20
not that the math is wrong it really isn't; it's the theory behind it.
I agree, photons do have mass. They are quite ‘light’, though. (I couldn’t resist)
JDrudge
this is truly amazing. :(
it make me feel sooo proud to be part of that twenty first century :((
now talk about medical applications
You do realize a Q switched laser has an ultra short pulse duration. Meaning your hypothetical laser wouldn’t even come close to the sustained output of a 500 watt continuous wave laser averaged over a given time period.
All of you need to take some Laser Physics lessons. Until you get your Ph.D. in laser physics, stop speculating. Just stop it. Make your point, but don’t speculate. Until you actually are making these products or have been in the laser field for many years, you have no right to guess this or that. Do your homework before you talk. Thank You.
- from someone who DOES have a Ph.D. in laser physics
poupou your self!