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[Andrew Broughton]

If they are going to do "hundreds of miles", then they will have to find a way to bend the laser to the curvature of the earth.

That part sounds like a typical political bold statement, that has no basis on reality

At 200 miles, the curvature is close to 27,000 feet.  So the laser would have to be very high up in the air-as in an aircraft.  Keeping it steady on a object would be a whole different problem.

Those darn physics keep getting in the way again---------------

Don't tell me you're one of those that believe the earth is actually round?


 

[Brian Jojade]

At 200 miles, the curvature is close to 27,000 feet.  So the laser would have to be very high up in the air-as in an aircraft.  Keeping it steady on a object would be a whole different problem.

Those darn physics keep getting in the way again---------------

Creating the sound at that distance and being able to wrap around the earth are 2 separate problems.  Conceptually, if the process can be done via an aircraft or a balloon, it could be extremely effective.  Heck, this could eventually come from a satellite orbiting the earth.

[Tim McCulloch]

Don't tell me you're one of those that believe the earth is actually round?


 

Not just round, it's spherical!

[Geert Friedhof]

oblate spheroid

[Tim Weaver]

at frequencies of up to 155 decibels

The new standard of journalism......





Also, I'm guessing that there are 2 laser heads in one device. 1 creates the plasma and the other vibrates that plasma to create noise. So these 2 lasers have to have a focal point somewhere down the line where the 2 beams come together and do their dance. How do they expect to keep these 2 beams straight over that kind of distance through atmosphere? Hitting one beam with another beam is hard enough at 100 meters, but over miles? I have doubts.....

[Jason Glass]

Hitting one beam with another beam is hard enough at 100 meters, but over miles? I have doubts.....

Most likely achieved by using coaxial optics.  The two lasers emit different wavelengths, so Catadioptric systems come to mind as viable means to locate the emitters at separate focal backplanes.

Atmospheric refraction and diffraction can be mitigated by high-speed active deformable elements and focusing mechanisms.

Still a huge engineering challenge to make this work at long range, though.

[Tim Weaver]

Most likely achieved by using coaxial optics.  The two lasers emit different wavelengths, so Catadioptric systems come to mind as viable means to locate the emitters at separate focal backplanes.

Atmospheric refraction and diffraction can be mitigated by high-speed active deformable elements and focusing mechanisms.

Still a huge engineering challenge to make this work at long range, though.

I thought about this, but had never heard of coaxial optics before and didn't know it could be done. I figured the two beams would have to be side by side and crossed at the focal point.

Egon, you said crossing the beams would be bad....

[drew gandy]

Not just round, it's spherical!

Don't tell me you're one of those that believe in 3 dimensions!?!

[Tom Roche]

The tech seems very likely to me.  For years the military has been working on laser-based weapon systems strong enough to destroy targets (e.g., AN/SEQ-3 Laser Weapon System, aka LaWS).  The system I worked on was fielded over three decades ago and the laser (mounted to an aircraft moving at hundreds of knots) could splash a target with pin-point accuracy from 40,000 feet away.

[Luke Geis]

The warplane stuff is a much different beast. The laser only " paints the target " and the sensor sees that reflection. The emitter is being guided by a computer to keep it on target and there is likely a smoothing algorithm on the sensor to reduce flutter, jitter and other things so it can more easily lock on. I would also guess that like an A.I's ability to recognize photos, it too has a picture recognition algorithm that once the target is painted, the computer tracks the image it is looking at that with the laser data. This is a little easier to do when the earth's motion relative to the plane's motion can be calculated and adjusted for. Keep in mind that the plane and the earth or moving really slowly in comparison to the speed of light and to boot, the tangent at which the plane approaches a target makes small movements less critical. If you have two points on the ground that let's just say are both high enough to " see " each other, if one moves even a fraction of an inch the other side will be half a mile off target. It could utilize correction software to move the laser correctly, but again it would have to have a beam that can have a 1mm dot at that distance ( impossible with current technology ) and the error correction devices that move the laser would have to be accurate to thousandths of an inch and make those corrections in milliseconds, not to mention the software would have to be able to read the data, calculate the correction and execute in almost real-time.

You have possibly heard the concept that if you were to make a shadow of a pair of open scissors on earth and project it onto the moon that you could close the scissors faster than the shadow would show on the moon. The thought is that you are closing the scissors faster than the speed of light, but of course, you are not. The relative distance from the creation of the shadow to the reflected surface and back to earth again is just far enough that you can actually witness the time it takes light to travel.  Light travels REALLY FREAKING FAST. So for contrast, light can travel the distance of 3000 miles in about .016 of a second. So you have to have real-time correction software that can calculate movement and correct in literally thousands of a second.

[ProSoundWeb Community]