Hi, I remember reading in... i think it was "popular science" a while back and they mentioned satellite laser defense systems- a satellite in space capable of using laser beams to shoot down enemy missles.
I was wondering... did they make this yet/ is it true?
I remembered this because i watched Batman Beyond: Return of the Joker and... well they had them in the future...
i remember the magazine i read was from the early 2000's though... they also talked about "hover planes", jets and such that were mobile like helicopters
The problem with a satelite based laser is the type to use. Chemical laser, crystal diode, CO2 would require alot of energy, durable optics, a very large resonator, and ofcourse the laser medium. other little problems along the way is the particles in space would affect the beam as it travels. anything in its path will weaken the beam. Even with today's lasers, dust, fumes and smoke distort and reduce the lasers beam, robbing it of energy. many of the lasers today have what is called a beam purge that forces nitrogen or purified high pressure air into the beam path to remove or reduce interference (fumes, dust, smoke) so the beam remains at it's intended strength. Space is a vacuum but there is alot of dust particles, ice particles and the like that would distort the beam form a satelite laser weapon system.
The program was called "The Strategic Defense Initiative", or SDI. It was cancelled after the Soviets agreed to mutual disarmament.
Dust and debris isn't as big a problem as you might think- look at the Airborne Laser that was successfully tested a few years ago. The big problems were targeting and optics, both of which were solved in the late 1990s, and the shear size of the system. The ABL needed a 747 to carry the jet-engine sized chemical laser and the huge tanks needed to fuel it.
The recent breakthroughs in solid-state lasers open the whole thing up again,
the optics issue was never resolved and plagues lasers to this day. Optics are generally made of Zinc Selenide (?) and after200 hrs of use on a class 4 CO2 laser, the lens breaks down, thermal distortion (micro cracking). A class 4 are generally in the range of 1800 to 6 kilowatts, enough to cut a 1 inch thick plate of mild steel or 3/4" stainless steel. a laser of that size, regardless if it is a RF (radio frequency solid state resonator)or a DC (direct current solid state)is going to burn out it's lens after a few shots before replacement. Cleanliness of the lens is paramount, any debris on the lens, visable or not, destroys the lens. A solid state resonator only makes a portion of the system smaller and the aircraft lighter to house more lasing medium (chemicals or gas)and the large capacitors to output the required energy to keep the beam integrity. focusing the beam is still an issue. Every lens has a waist that is the smallest most intense protion of the beam. That would be the business end of the beam, the part that melts/destroys to be placed on a target. The waste is a fixed point of a lens and each lens no matter how precise it is made, must be calibrated for that point. In practical application, one would move the waist to the point in which you want that contration of the beam to do it's work, example, moving the lens up or down to create that small hot point. Although we were able to destroy several missles with a laser, it required to be a given distance in order for the laser to destroy it's intended target. Can it be down, most cetainly but not reliably. In a satelite from space, not quite yet. I would love to see how they do it when they do.
The Airborne Laser has demonstrated 100 KW class performance on moving targets, using mirrors rather than lenses. Adaptive optics (distorting mirrors) correct for atmospheric effects and range.
That was in the 1990s. In 2003 we deployed a solid state laser in the 10 KW class to destroy IEDs in Iraq. It had reliability problems, but it was mounted on a HMMWV so I don't think size is quite the issue anymre.
a laser has to use a lens to focus the beam. both interanally (colminator and output window) and externally (focusing lens). Adaptive optics do nothing for atmosheric conditions, A.O. does correct for beam divergence (inconsistencies in focus point at the beam travels away from the light source) and focal correction/adjustment over a short distance. An adaptive optic is usually controlled by water or air pressure to deform the mirror (copper mirror with a cured, gold coating). The weapon system mounted on a hummer was using a large capicitor and good for 2-3 shots in a realtively short range. It super heated the intended target rather focusing the beam on a specific point to maximize the burn. It used a raw beam that opened up to about a foot in diameter or more as it traveled further. Correcting atmosheric conditions (fog, cloud cover, dust clouds, heat humidity)was burning it away in order to reach the target. a small laser ( an example, 3.5 kw) has an inside wattage of 10 kw but the output window will allow and handle ( over heating) a maximum of 3.5 kw. The rest or the light bounces around the resonating chamber between mirrors maintaining 3.5 kw for continually use. The technology is there but the materials to maintain a reliable beam isn't there. Eventually, maybe 5-10 years, it will be. Wow, it sounds like I'm at work in front of customers...
