Slashdot Mirror
Laser System to be Tested in Boulder, CO
luv_jeeps writes "Ball Aerospace is going to test fire a laser beam on Sunday night, as part of the CALIPSO project. If you live in the Colorado/Wyoming area, chances are good that you could see it. The article, a little light on details, says that the beam could be as big around as a basketball hoop."
Did anyone read the part about the radar system? HellO?
Well the US army has been testing a airbourne lazer for a while now which shoots down (well supposedly) missiles in flight. I think they got it to work on the ground, no to get it to work on a 747.
The article says it's "about 40,000 times more powerful than a laser pointer", and 40k*5mW=200 watts. Since the beam diameter is "the size of a basketball hoop", nothing would be bursting into flames, although serious eye damage - to birds or pilots - could result.
Although come to think of it, for a LIDAR application I guess the beam is probably pulsed, so the situation is a bit more complicated. At any rate there's a safety shutoff mechanism as someone else pointed out.
Because dust particles or water droplets can reflect it; furthermore, the atmosphere will disperse it. FYI, the sky appears bright because it disperses light (it disperses blue the most and red the least. This is why the sky appears blue during the day and red/orange/yellow/gold/your-favorite-sunset-color when the sun is low in the sky).
In summary, you would see a bright enough beam in the atmosphere even if there were no dust in the air.
Don't waste your vote! Vote for whoever you want, unless you live in a swing state it won't matter anyways
Actually (from the project info page):
Ball will provide an active sensor that probes the atmosphere with green and infrared laser light
They're using IR (almost certainly 1064 nm) and green (almost certainly 532 nm) beams.
If it's light, it would be lidar, not radar. Of course we have no reason to think the author would get something like that right.
~200 W of green light is far, far more than powerful enough to see the backscattered light with the naked eye. Even in a relatively clean laboratory, a 1 W green beam produces enough light to easily see the beam path, along with bright 'flashes' whenever a largish dust particle drifts through. Remember that green laser light is right in the 'sweet spot' as far as human vision is concerned, which is why green laser pointers look so much brighter for the same power.
Yes the Satellite may have Infared on it but it also has Lidar which is Laser Radar. My local university has a lidar setup (or the green beam as its called around here). See the Utah State University link below.
Its used for atmospheric observations.
Utah State University - This page seems to be down at the moment
University of Western Ontario - Here is another University with one
The "common laser pointer" they talk about is one milliwatt(mW). That means their laser is 40W, common in industrial laser applications.
A lightning bolt contains roughly enough power to light an entire city for a second or two; it's about a million volts, and about 10,000 amps on average. That's a -trillion- watts. We're talking a MINOR difference in scale here, my friend. A lightning bolt makes a noise because it turns the air around it into superhot plasma, along with any moisture(which expands thousands of times its original volume when vaporized).
If the satellite were to receive that much energy, it'd explode instantaneously, and no, you -wouldn't- hear it, it's in SPACE, there's no AIR, so there's no SOUND- just wanted to get that straightened out, since you seem to have slept through most of your high school and college science classes.
I cannot -believe- the parent got modded up...
Please help metamoderate.
"The laser system is equipped with radar that will shut down the system in the event that an object is about to enter the laser beam."
How does it work? Does it work? I don't know, but those are the precautions they say they've taken.
"How to Do Nothing," kids activities, back in print!
I'm American, but I don't play sports, so I looked it up. A basketball hoop is about 46cm in diameter. (That's 18 inches for those of you who don't understand metric)
"I like you, but I wouldn't want to see you working with subatomic particles."
you're thinking of red lasers. Red light passes through air much better than the higher frequencies (blue, green, yellow, etc). A great example of this is the color of the sky. Light from the sun passing through the atmosphere has its blue components scattered much more readily than the lower freqency components, so you see the sky as being blue. When the sun is rising/setting you see the sky as red because red light isn't scattered well the red light that reaches your eyes is much more intense
so, why are these people using green light that they know will be scattered? Because that's exactly what tells us stuff about the atmosphere!how much was scattered at position x compared to position y? how much was scattered at time t1 as compared to time t2?
The pollution causes more light to be scattered, for sure, but that's not WHY you see the light. Rest easy :)
There is still no such thing as a phaser, the word has no definition, beyond that found in Star Trek. This device may mimic one of the effects of the fictional weapon, but that is all.
"The question of whether a computer can think is no more interesting than that of whether a submarine can swim" -EWD
It's supposed to shoot down artillery shells (i.e. big lumps of metal with no guidance, fuel, or other fragile bits), although nobody's sure entirely how.
You are thinking of a different laser system. There is a ground-based system designed to do what you're talking about, but there is also one mounted in an aircraft for shooting down missiles.
"...always new atoms but always doing the same dance, remembering what the dance was yesterday." -Richard Feynman
I'm no expert on the situation, but in the Navy, when they're making flight-ops plans, they make sure they go around large flocks. The weather radars will give a reflection for large flocks, and the aerography guys know what's fowl and what's weather. Keeps the navy from F.O.D.ing the engines out with animal parts. It's the single birds they gotta worry about. Damn Turkey Buzzards ;\
Sig not found.
You are also wrong
We've got the one that shoots down missiles, the ground-based laser system. It works. Mostly. I guess there's still a few bugs to work out, but it's an incredibly simple concept -- find missile, point big laser at missile, fire laser for 2-3 sec., missile blows up. They've used it on missiles and rockets, with up to i think 1.5" metal skin, and blew em up.
We've got the airborn version, that I don't think worked as well on the missiles..
and we've also got an airborn laser used not for missiles, but for soft targets. Blow up a truck or a jeep or something like that. Fry a dude standing outside takin a piss. That one, I think, works
The only thing the Geneva convention bans is a laser designed and used specifically to blind enemy forces. Incidental blinding caused by a reflection from a death-laser is allowable.
There's a PDF here that describes the prototype laser as delivering 110 mJ per pulse. At 20 pulses per second, that's about 2 watts average power--but of course the peak power in each (short) pulse will be much higher.
~Idarubicin
HI, I am going to get a little technical on you and try to answer a couple of questions.
;-) and they are invisible unless it reflects off of something and enters our eye. Smoke, pollutants, water vapor and dust provide the particulate that the photons can reflect off of.
;-P
Ok first off
Q: "Wonder what kind of sound effects it will produce?
A: None. It requires substantially more power than they are using to ionize or break down air.
Q: "is it just me, or does the laser beam in the picture in the article spread a *lot* more than what you'd think it should..."
A: All LASERS spread or "diverge", the beam from the actual laser is probably ~8 mm or so and will get bigger as it travels. When you play with a laser pointer you notice that far away the beam gets bigger. Imagine this same effect over hundreds of miles. They are taking that small beam that is getting bigger with distance and making it big and focusing it at a predetermined point in space, or collimating it so they can control the divergence and keep it basketball sized for hundreds of miles.
C: "it is infrared making it a bit hard to see with the naked eye"
A: Actually it probably isn't, if it were IR then we would never even know about the test. The media blitz is so us folk in Denver don't go running for the hills shouting 'THE ALIENS ARE COMING! - THE ALIENS ARE COMING!'
If it is green they are probably using Frequency doubling or second harmonic generation (SHG) this is a technique used to produce a wavelength that is one-half of the fundamental wavelength of a laser. For the 1.06-um ( infrared ) fundamental of Nd:YAG, the second harmonic wavelength is 533nm (visible green, by the way this is right around the peak of the color perception of the human eye that is why 5milliwatts of green look several times "brighter" then the same power of a red 632-670nm laser).
In English: Start out with something that is easy to get high power with, IR then put it through a crystal that relases at green.
Q:" Hu ? I though that lasers were invisible because they are made of photons that all goes in the same direction...
A: Photons do travel in a straight path, more or less
Q: "I know that the atmosphere is polluted, but not THAT much, is it ?"
A: YES, if you have enough light energy present, (not in a vacuum) , think search lights.
Q:" Are they going to attach it to a shark's head eventually?"
A: Not for the foreseeable future. A couple of problems:
First: water is great at absorbing light particularly in the longer wavelength (red side of the spectrum) this would severely limit the useful range. And if you did have enough optical power to do any serious damage to anything it would be IR ~100,000 watt range, and water would absorb most of the energy resulting in a large steam explosion at the laser output window on the sharks' head.
Second: POWER. Most lasers are horribly energy inefficient. A typical ION laser consumes roughly 16,000 watts of electricity to produce ~5 watts of optical power (laser light).
Given this, to get roughly 100kw output power on a sharks head the device would have to consume roughly 320,000,000 watts worth of power probably in the form of a chemical reaction.
All things being equal and ideal this apparatus would roughly be the size of a size of a large van, attached to a sharks head...
_Chad ~ Lazer guy....
Dude, get your facts straight.
The Tyndall effect or Raleigh scattering shows that small particles scatter higher frequency (blue) light more than lower frequency (red) light. Both "pass through" air just fine because they're not absorbed, but the lower-frequency light is scattered less easily. At sunrise/sunset, there is much more air (and also more dust) for the sun to go through, so more light is scattered, so more of the red light is scattered, so the sky appears redder.
As for why light is scattered from a (fricken) laser: because there are *lots* of photons there. Green light will scatter more easily than red, but it also has to do with the amount of light they're shining up. Think of a spotlight shining up into the sky. You don't see the light from the spotlight directly, you see it bouncing off things in the atmosphere. Same deal with a laser.
There is nothing special about a laser as compared to a flashlight in how easy it is to see the beam. In a non-dusty environment, you won't see a flashlight beam either. In a dusty environment, you might see a flashlight beam more easily, because it is a wider beam, but you might see the laser beam more easily, because any dust particles will be lit more brightly by the more concentrated beam. The only way in which the in-phase and parallel aspects of the laser contribute to how easy it is to see the beam is that they make the beam narrower.