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posted by: thelibra
A Lesson in Physics and HEWs
I can actually speak with a tad bit of authority on this subject, as I attended an IEEE conference where one of the tracks was a whole lecture on the use of HEW weapons, and I can say with 99% certainty that High Energy Weapons of any sort, including "laser beams" are impractical across that distance. Here's why:
HEWs heat, not cut or bore. - Lasers, as weapons, are not intended to cut through objects, bore through them, or anything of the sort. Their purpose is to heat up the target to the point where its operation thermal threshold is exceeded and the device is thusly disabled.
Cannot track well through atmospheric particles - Despite how clear or stable the air appears to be, it is, in fact, exponentially detrimental to tracking with a laser. As we are all well aware, a laser is composed of highly concentrated photons. Over short distances, the sheer volume of photons are able to mostly burn through the dust and vapor floating in the air. However, it is important to note that some photons are deflected when this happens, their trajectory might change as subly as a fraction of a degree, or as much as 180 degrees, depending on the angle of incidence (the angle the photon strikes relative to the surface of the particle it hits) and the ablation (reflectiveness) of the particle. The important thing to remember is that particles floating in the air are MUCH more massive than photons.
The effect would be akin to throwing a rock at the side of a building. Now, if you had billions of little rocks, equal to the volume of, say, a stadium, and were able to forcefully project them at a building the size of a house, you would still end up destroying the house and sending a LOT of rocks out the other side, in roughly the same direction, but a portion of the rocks would be lost during impact, or deflected, leaving fewer rocks most likely travelling at a different angle.
This is one of the reasons when you shine a beam of light (like a flashlight), the light spreads out further and weaker the longer the distance. A laser is little more than a very very powerful concentrated flashlight, and is thus susceptible to the same trajectory-altering physics.
The end result is that prolongued laser exposure to surface will "dance" at the impact point in a random fashion. The more atmosphere it is beamed through, the larger the dance will be on the target. As of about two years ago, the best they managed was a two-foot radius dance at a littler under 40,000 feet with two stationary targets, over the course of 30 seconds. It was not a solid dot that slid around the radius, but rather a jumping dot that sometimes disappeared altogether. For a satellite to remain in orbit, the distance to Earth's surface must be at least 35,768 km, most are around 45,000 km.
That means over 117,349,081 feet of atmosphere must be passed through. Using only simple math, that equates to a "dance" of 5867 foot radius. Since the effect is actually exponential, it is unlikely to be that small in reality.
With only a two-foot dance, there is still not enough continuous contact to generate enough heat to disable craft at only 40k feet, within Earth's comparatively thick atmosphere and hotter temperature, much less the much colder depths of space where there is no air insulation to trap heat.
So effectively to disable a satellite with a HEW, you would have to overcome the random particulates and airflow through the atmosphere, and to do that, you've either got to be in space, or somehow create a vacuum between your laser and the target for the length of the heating.
"The Chinese are very strategically minded and are extremely active in this arena. They really believe all the stuff written in the 1980s about the high frontier," said one senior former Pentagon official.
Originally posted by kinglizard
lol Please, believe whatever you like but the fact remains that this is old technology at least a decade old.
My point is that the dancing particals (the element required to apply heat and thus damage) is NOT REQUIRED (or even desired) by this system.
It's just light. It's a bright enough light source to blind a camera looking in it's direction.
Infact, because you only need to spam the satellite with enough light to block out naturally refected light, the system my not even require knowing where the satellite is OR the abillity to track it. If your laser is powerful enough, you could difuse it at it's source to create a large cone that would act like an umbrella. This would blind any camera pointing in the general direction of the laser's source. That would be in-efficent, but doable.
Personally, if I were to implement a system like this, I would create a hybrid between tracking and spamming to maximize efficency. A broad cone that fires into the trejectory of the satellite and uses some very basic math to predict it's path. Hell, I've writen more complex code for computer games!
The only really hard bit is seeing the satellite in the first place. Those things are small and fast moving, so detection is difficult. That said, China has it's own satellites and it's no great leap to assume that some of them are likely equiped to look for other satellites.
Reguardless, the important thing I'm trying to get across is that this system doesn't have to damage anything in order to work. This is no more an "attack" than a security guard shining a flashlight into your face when he catches you trying to sneak into someplace you shouldn't be.
Bit raiser made some interesting points I could actually reflect on in another thread regarding this subject, and I would say that after careful consideration I agree with him.