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Laser Weapon Shoots Down Airplanes In Test
airshowfan writes "Boeing's directed-energy weapons (a.k.a. frickin' laser beams) have been getting some attention lately. The Advanced Tactical Laser (ATL) is a C-130 that famously burned a hole through a car's hood, and the YAL-1 AirBorne Laser is a 747 that shoots a laser from its nose that is powerful enough to bring down an ICBM. But even cooler is the Mobile Active Targeting Resource for Integrated eXperiments (MATRIX), a laser that is mounted on a truck (which probably costs less than a 747, but who knows) and that can shoot down small aircraft, as shown in the picture on this article. (The Laser Avenger supposedly also has this capability). We live in the future!"
Ignoring the fact that you can't make an object shiny enough, because there'll always be a thin layer of dust, crud, or even oxides on the surface...
That won't work. The problem starts at step 2. If the top layer isn't reflective, then as it "boils away" it will convert incoming energy from the laser into heat efficiently enough to destroy any reflective layer that might be under it.
Even if that weren't the case, you'd still have a problem at step 3, because your reflective surface will still absorb too much energy. An expensive mirror that's new, clean, and in perfect condition would still absorb 5% of the energy hitting it in lab conditions. In the air, in combat conditions, coated with goo from the stealth paint that just got burned off of it, the reflective layer wouldn't last even a measurable fraction of a second.
Optical vs. radio is just a choice of wavelengths. Whatever wavelength you pick to be shiny, can be used to detect you. Whatever wavelength you choose to be "not shiny", can be used to destroy you.
I wish GP hadn't bothered to mention the problem of stealth, because it's diverting attention from the point that matters - no material of any sort can be kept sufficiently reflective under combat conditions that the laser wouldn't destroy it. So really, even whatever wavelength you pick to be shiny, can still be used to destroy you.
Each photon in the beam transfers its momentum to the target. For total reflection it transfers twice its momentum. This will result in radiation pressure exerting a very localized force (so high pressure), and if there is any absorbtion it will heat up the material locally, causing a temperature shock, since the immediate surroundings don't get time to heat up.
Wow, really? These are all just corporate welfare programs? I guess all the knights in the Middle Ages said that firearms were just affirmative action programs so that poor, untrained, conscripted villagers could compete on a level ground against knights. You can never predict the ways in which methods of combat shift, and so you have to continue to fund initiatives such as these. The current method of conflict now is clearly unconventional and asymmetric, however it could easily switch back to traditional, set-piece combat(ie. WWII and theorized Cold War confrontations). If this shift occurs, Strykers, MRAPs, COIN planes will do nothing for us. That's why we need to continue developing air-to-air technology, ground-to-air technology, and the likes. These things won't win us the current wars, but they damn sure might win us the next ones.
The only thing necessary for evil to triumph is for it to be pitted against a slightly greater evil
Ronald Regan, he played the role of George "The Gipper" Gipp in the film "Knute Rockne, All American;" from it, he acquired the lifelong nickname "the Gipper."
RUGBYRUGBYRUGBY
What country were those hijackers from, again?
The hijackers were from all over, mostly from countries with governments that are our allies who are doing what they can to combat the problem themselves. Invading them would halt those efforts and turn the populations against us. The plan was hatched in Afghanistan, however, where the then government did what they could to protect and harbor those who planned the attacks.
There is no "I disagree" mod for a reason. Flamebait, Troll, and Overrated are not substitutes.
As another poster mentioned, we have not suddenly developed better ethics, we've developed better bombs. Carpet bombing is unnecessary now. We only ever carpet bombed cities with heavy war industries. Certainly, the effect on morale was part of the decision to target cities, but we did not use carpet bombing primarily as a terror tactic.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
No, I wouldn't happen to work for Boeing. I would happen to have taken basic physics, though.
For the sake of argument, I'm going to pretend that your idea of shedding a stealth layer would work, because it's moot. You can call my statements "mighty assumptions" all you want, but I'll stand by them. If I'm wrong, we'll surely see the headline that proves it soon enough.
As for this: "A laser weapon designed to fry a plane that absorbs 70% or more of it should be less than effective if the said plane absorbs only 5%."
Wrong. The 5% is only the initial amount of energy that gets through. That's enough to destroy the mirror so fast that you'll never notice any of the laser reflecting away. From that point forward, the target receives close to 100% of the laser's energy and is destroyed quite effectively.
And, that 5% is a very optimistic figure. Again, that's for a clean, flawless, perfectly maintained mirror made for lab use and kept under lab conditions.
I know it's much easier to bitch about lack of citations then to do, say, a google or wikipedia search on reflectiveness of mirrors, but I'm just gonna leave that as your problem.
Power != energy. Energy is not measured in watts. Come back once you understand that.
Coding with assembly is like playing with Legos. Coding an application in assembly is like building a car with Legos.
They are also quite good at locking people up. If you want anything else done right you will have to do it yourself.
Each photon in the beam transfers its momentum to the target. For total reflection it transfers twice its momentum. This will result in radiation pressure exerting a very localized force (so high pressure)
Hm... I can't find anything specific about the power, just "mega-watt class". So let's call it a megawatt and we can multiply the result as necessary. I'm also going to guess it's a 1.315um COIL laser. Momentum per photon is h/lambda = 5.039e-28 kg*m/s, energy is hf = 1.511e-19 J. The megawatt laser therefore produces 6.618e24 photons/s, so assuming total reflection that's a force of about 0.0066 N.
I don't know how tightly the beam is focused, but if it's 1mm^2 (which seems pretty damn tight, someone else can calculate the divergence), that's a pressure of about 6600 Pa, or about 6% of standard atmospheric pressure. How many atmospheres do you need to damage a plane?
I dunno, I have a hard time believing radiation pressure is going to be a significant factor in the effectiveness of a laser.
The enemies of Democracy are
A couple comments here are focusing on stealth, that's not the big question.
There is not a single US Gen 2+ stealth aircraft engaged in Iraq/Afghanistan. F-117s have been retired, B-2 are not needed. The aircraft over there are relying on a variety of other IR countermeasures (tactics/flares/directed IR) to defeat threats.
TFA is talking about shooting down UAVs, which pose a unique problem because they are very small and can be made out of low-tech composite stealth materials like frickin balsa wood. That, combined with a naturally low IR signature because of their low performance envelope, make it hard to target then with traditional guided weapons (IR and Radar guided).
The key question, which TFA avoided giving details about, is what range they are talking about. If the range is = a 25mm chain gun, this system has little value yet, as if you can find it and track it, a turreted chain gun is already very deadly, the ballistics models aren't that hard to compute. But those weapons are also very easy to fly above.
If this laser has a range of, say, 8 miles (40,000-ish feet), then things could get interesting. Data that would also be important is how long the laser needs to stay on target, and how small the beam is. If the beam is 1" wide, and must stay on the same spot for 1/2 a second, it could be defeated by old-fashioned 'jinking' which would move the beam around and diffuse the heat. But if it's 1/100 second, then again, it's really deadly.
Finally (and then I'm done), this laser is really cool, but must be guided by something... at 40,000 feet (or at night), you'll need something better than a Mk 1 eyeball to find and track the target accurately enough, just like you do today, and that's where countermeasures could be applied.
But a really good EO/IR guidance system that can find/track targets up to 40,000 feet on a clear day at night and a laser that can kill in 1/100" second (or close), and you've got a game-changing technology, forcing aircraft to hope for cloudy days.
Maybe. Chemical lasers are hard to pulse, unless you Q-switch them. (but then you waste some energy when the Q-switch is off.
A favorite technique these days is to use multiple diode lasers to pump a glass slab. It's the same thing in principle to green laser pointers which have a single laser diode pumping a ND:YAG crystal. (The green light comes from a frequency doubling crystal) In a weapon laser, you'd have hundreds of multi-watt infrared diodes pumping multiple doped glass slabs all bathed in a liquid whose index of refraction matched the glass at the wavelength(s) you are creating. The liquid also cools the system and the output mirrors. The diodes can be pulsed or continuous.
B.t.w if you have enough gain in your system, you don't need and output coupler mirror, just the highly reflective mirror behind your laser medium.
All ideas^H^H^H^H^Hprocesses in this post are Patent Pending. (as well as the process of patenting all postings)
You might want to talk to the residents of Dresden circa 1945. While the war in Europe was not yet over, it wasn't far from completion, and most of the reasoning for bombing it look to have been retrospective and stretched. Even Churchill, rarely one to shy away from attacking the enemy to advance even small objectives, distanced himself from it after he realized what the effects were.
You can never go home again... but I guess you can shop there.
no material of any sort can be kept sufficiently reflective under combat conditions that the laser wouldn't destroy it.
Indeed. A more fruitful approach would probably be more similar to reactive armour; a material that produces large amounts of refractive or absorbing smoke particles to dissipate the beam and rapidly transport the energy away; a cursory reading about directed energy weapons indicate that even the ordinary vaporization of the target can cause shading problems.
Various kinds of vapour countermeasures might also have the advantage of providing beam tracing possibilities for a retaliatory strike.
Just a word about Afghanistan...
The Soviets tried invading it like WWII and still lost.
They had no qualms about carpet bombing villages or shelling it ground level. They would even storm them with full tank brigades.
They would execute suspected guerrillas on the spot without question.
They still lost that war.
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The topic of discussion was the radiation pressure of the laser. ByteSlicer was hypothesizing that a laser this powerful would have enough momentum to destroy things just with that, but they are quite wrong.
The actual energy of the laser ("mega-watt class" according to tfa) is of course sufficient to cause significant damage; the whole point of this demonstration. But it's not doing it's damage by the photons imparting their momentum to the target. ;)
The enemies of Democracy are
The carpet bombing and artillery shelling of WWII had two effects. First it did reduce the ability to wage war through the destruction of industrial facilities. Also, since we were bombing the living crap (killing) civilians in their homes, it broke the will to fight of the civilian population. We tend not to do that anymore, so we are ignoring a major component of how wars are won due to us wishing it wasn't true.
Current chemical lasers suck for firing at low-value targets. The fuel is massive and incredibly toxic. It's worth using 300 pounds of fuel to take a shot at a boosting ICBM, but not so much at a UAV. However, that's just a fuel source, and not the core part of the weapon technology. An electrical laser would be dandy for defending equipent that naturally generates power from UAVs. And shooting down boosting ICBMs is becoming more valuable as more countries gain access to those.
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