Originally posted by Murcielago
With forseeable developments of aircraft and lasers my bet is that the aircraft will stay in front for a fairly long time to come.
Yeah, I'd guess around 10-15 years before lasers have a large impact on the modern battlefield.
[edit on 4-9-2005 by Murcielago]
This comment only applies to anti-air laser weapons wherin the laser beam is itself the weapon. When the beam is used for other purposes (which is
all we've really been able to accomplish up to now), then I would have to say lasers have been very effective in combat for many years now.
Someone asked how hot lasers got and I understood the question to be asking how hot the target would get. If that was the question, then the answer
depends upon the amount of power contained in the laser beam at the point it encounters the target. To refine the answer further, it depends upon the
wattage delivered per unit of target area. In other words, if the beam is very small then all the wattage is contained within a small area and the
target heats up quickly, thus requiring less dwell time on target to be effective. Of course, the more wattage contained in the beam to begin with,
the quicker a target will heat up. Ideally, you want the highest power and the smallest beam in order to cut the dwell time to something the
targeting system can attain. Another factor though is the heat generated within the laser system itself because of imperfect optics, less than
perfect mirrors, etc. These defects currently limit the amount of time a laser beam can be continuously projected without destroying the weapon,
which is why laser weapons are pulsed projectors (gives the equipment a break between pulses). Another factor to consider is the actual delivery of
power to the weapon. It is impractical, because of physical limitations, to actually pump enough power into the weapon on a continuous basis to make
it useful. Therefore, quick discharge power storage devices, such as capacitors, are used. However, that also means the devices require recharging
and the recharge time is limited by the magnitude of the power available on a continuous basis. It all boils down to a bunch of engineering tradeoffs
that must be considered for each weapon.
Now, having said all that, I'll tell you that the best systems currently available require only a few tens of miliseconds dwell time on typical
aircraft materials to be effective at reasonable ranges. Again though, that time will vary depending upon atmospheric attenuation and the angle of
incidence of the laser beam. (The closer the aircraft, the more nearly the angle of incidence to 90 Degrees, and the dryer & thiner the air, the less
the dwell time required.) The real long pole in the tent is the targeting system (i.e., actually pointing the beam at the target and holding it there
long enough for the laser beam to be effective). It turns out that building the targeting system is generally more difficult than building the beam
To illustrate the problems, lets take a 50 ft. long aircraft at an altitude of 25,000ft. moving at a velocity of say 1200 knots (relative to the laser
beam projector). The planes velocity in miles per hour is about 1380 mph, or 2024 feet per second. If one could project the laser beam onto the
aircraft and say focus it enough that the beam was only 6 inches across at the point where it struck the aircraft that would still mean the aircraft
would be moving through the beam at the rate of 24,288 inches per second, or 24.288 inches per milisecond. In other words, the beam would only dwell
on any one point for about a quarter of a milisecond (this, of course, assumes the beam is stationary relative to the target). Now, if the beam spot
were reduced to say 1 inch across the dwell time could be reduced by a factor of 36 times (the old square law of variation at play). However, in the
example used, the beam would still not be effective against that aircraft because it would still be moving to rapidly through the beam. The beam
would have to be reduced in size a little further before it would be effective. At a beam size of 1/2 inch, the aircraft would be destroyed by simply
flying through the beam, but we don't have an optical system that can focus a beam to a 1/2 inch spot at 25,000 ft. What we can do is try to move
the beam along with the target, but the air itself causes the beam to dance around quite a bit at that range. Hopefully, you get the idea just how
tough the problem really is.
[edit on 4-9-2005 by Astronomer68]