Laser Flares

[sarman]

There have been multiple instances where lasers have been shone at emergency services helicopters. A local TV article of the effect from the pilots point of view, associated with reporting the court case, showed that they are effective at attracting attention.

The Greatland Laser Rescue Flare was designed by pilots for the use of pilots (crashed) to attract the attention of pilots (searching).
It was designed to attract attention, not kill the person trying trying to save you.

 

[jetwake]

I use a green laser in my astronomy "hobby" and as far as that goes its a bright green beam of light, visible all round, that points straight at ME. On that basis, a red one at sea would do precisely the same. I think it might be the future and I await the developments with eager anticipation.

David

 

[sarman]

I use a green laser in my astronomy "hobby" and as far as that goes its a bright green beam of light, visible all round, that points straight at ME. On that basis, a red one at sea would do precisely the same. I think it might be the future and I await the developments with eager anticipation.

David

Your eye is best at seeing green (555 nano metre wavelength). Red is around the 6 hundreds and the ability to "see" falls off sharply.

A laser at 635 nm will seem to be twice as bright as a laser at 650nm of the same power, and then at high 600's/700 we are into infra-red which you cannot see. Both will seem dull compared a green (555nm) laser at the same power.

Your green laser is set at a frequency which works best with your eyeball - so you notice the tiny reflections from dust particles in the air and appear to see a solid beam.
To get the same effect for a red laser one must use a very high level of power - a level which will fry your retina. You will only just be aware of it (before you go blind).

But the tiny and very inefficient reflections from dust particles will not be visible because it is red and your eye can only just see red.

Funnily enough, this is why your Starboard navigation light always seems brighter that the Port navigation light.

 

[greenalien]

As someone who regularly uses lasers for entertainment purposes - I currently run a 3W RGB system - I can confirm that even high-powered lasers are almost totally invisible unless they are projected through some medium, like fog or smoke, that scatters the light beam. Even then, the viewer needs to be fairly close to the beam axis to see much, even if the beam looks bright when viewed from the source end.
I await these new laser flares with interest!

 

[2Tizwoz]

The need to light something applies to all forms of flare and light show.

Traditional flares use smoke but also rely on a chemical means of producing light which is short lived and dangerous in use.

The real problem is producing something to light which is waterproof.

The new light sources overcome the danger and longevity issue. We use flashing lights to signal as they attract our attention.

Could a sufficiently high intensity led source strobe be produced which would not be so dependent on something to light but would attract attention in daylight?

 

[greenalien]

Very high-intensity LED sources are already available, such as those red ones being used, in conjunction with lasers, in the latest generation of video projectors such as the Casio XJ-A140. Combining one of these with a white smoke source could be a better basis for a flare than something using a laser, as the beam is more diffused and would light up the whole area of the smoke.

 

[Twister_Ken]

Still not going to get up to 1000 feet, like a paraflare though. And almost everybody, even granny on the prom, knows WTF a red flare means.

http://www.youtube.com/watch?v=5IBHWzFBmfI&feature=related

 

[greenalien]

No reason not to loft a package of optoelectronics with a parachute - using this with chemical, rather than pyrotechnic smoke could potentially be a lot safer due to the reduced fire hazard.
Some years ago, I returned to my tent at the Glastonbury festival to find a large hole burned in it. I still have the remains of the culprit, a parachute flare, hanging on my wall...

 

[maxi77]

Could a sufficiently high intensity led source strobe be produced which would not be so dependent on something to light but would attract attention in daylight?

One of the problems with high intensity lights is they can be dangerous to your eyes. It is perhaps not the best idea to blind your self and your crew in attracting rescuers.

There are ways of managing this but care is needed to keep people safe.