by Douglas S. Ritter
The brilliant light from a laser would seem to be a natural for distress signaling, but it’s only recently that a product has become available that takes advantage of a laser’s unique capabilities. When we first saw Greatland Laser’s prototype for the “Rescue Laser Flare” back in 1999 we were impressed with the concept. It seemed to have strong potential as a nighttime signaling device. In 2001 they entered limited production and the device has undergone a series of improvements over the past three years. Our latest series of tests suggest it’s ready for prime time.
How It Works
The basic concept of the Rescue Laser Flare is to modify a laser beam so that it projects a line rather than the pinpoint of light we normally associate with a laser. The theory is that the expanding vertical line will cover a wide swath, so that it will greatly increase the odds of being seen as a survivor aims it along a horizon or at a potential rescuer. The laser light is distinctive and stands out better than a flashlight. It will cover a much greater area than a normal flashlight (because the beam line stays powerful as it keeps expanding) and it works very well when it crosses any retro-reflective material, like that affixed to PFDs and liferafts.
Greatland Laser has adopted the aiming technique used for signal mirrors without an integral aiming aid, and this has proved reasonably effective: The laser is held up just below the eye with one hand, while the other hand is stretched out to arm’s length with a pair of fingers forming a “V” to provide a sight. Keeping the target sighted between the fingers, and aiming the laser light directly through that “V” increases the chances the light will reach the rescuer’s eyes. This technique is illustrated on the instruction card provided with each device.
This technique, unfortunately, requires two hands. Greatland Laser has told us they’re working on aiming sights that can be added to existing Rescue Laser Flares, or that will become integral in the future.
The devices come packaged with a piece of self-adhesive retro-reflective material and instructions for how best to operate the device. Effective use is not necessarily intuitive, and by using the retro-reflective material as a target, it’s easy to see how critical it is to move the laser very slowly in order to signal a target, or to locate someone. If moved too fast, the flash of the thin laser line is too quick to register on the eyeball. Anyone who relies on this device should practice with it. It doesn’t take much—five minutes is probably all that’s needed in most cases.
We’ve seen that without training, virtually everyone who tries the device moves it too quickly to be effective in scanning mode.
The flash of the laser light is definitely distinctive and not likely to be confused with anything else. It’s perceived as a flash of light similar to, but not exactly like that from a signal mirror, but bright red in color. In any area with other white light sources, it stands out better than the flash from a white flashlight.
The red laser beam exits the device with a 4-degree spread. This gives a line of roughly 9 inches at 10 feet, compared to the typical pinpoint laser pointer beam next to it.
Plugging the beam angle into a formula, this results in a beam 738 feet long at two miles and 3,690 feet long at 10 miles. This long line improves the chances that you will hit a target you’re aiming for, while still providing a concentrated narrow light source.
For safety purposes, the U.S Government strictly controls the power output of laser devices. These lasers are Class IIIa devices, similar to a laser pointer, and they are limited to 5 mW of output. The laser itself is an LED- based solid-state device, and a lens is used to covert the pinpoint laser beam into a line.
There’s nothing to keep the cylindrical device from rolling, and the small lens cap designed to protect the recessed lens over the laser aperture isn’t attached, so it can be easily lost. The lens cap is translucent, so if the device is inadvertently switched on, there is a visible indication.
A waterproof instruction tag is included, tucked under the lens cap. We would suggest adding a neck lanyard and attaching the instructions—laminated, with a punch-hole—to the lanyard itself.
Greatland Laser makes the device in three sizes, offering similar signaling performance. The different sizes incorporate smaller and larger batteries, which impacts duration of operation, but the actual laser module is the same. The standard red laser versions are all about 3/4″ in diameter. The current line-up includes the original Rescue Laser Flare ($100), now powered by a pair of 1.5-volt alkaline N-cell photo batteries. It is 4″ long, weighs 4 oz., and will operate for 15 hours. The Magnum version ($110) is powered for 72 hours by a pair of AA-cell alkaline batteries, is 5-3/4″ long, and weighs 6 oz. The Rescue Laser Light ($90) is only 2-3/4″ inches long and is powered for 5 hours by a single 6-volt 28 L-cell lithium photo battery. It weighs 3 oz. The end cap can be removed and it can be screwed onto the butt of a Mini-Maglite.
The two larger units are constructed of black Delrin plastic and proved plenty tough in our tests. The Rescue Laser Light is made of aluminum and is anodized black. All incorporate some light knurling on the barrel, but not enough to provide an especially non-slip grip.
The tail caps all incorporate a lanyard hole. The two larger Rescue Laser Flares are switched on via a screw-in tail cap and are rated as waterproof to 80 feet. The Rescue Laser Light has a rotary bezel switch and is rated as waterproof to 10 feet. This rotary switch is too easily switched on inadvertently. A piece of tape will secure it in the off position.
We’ve conducted two surface-to-air tests of the Rescue Laser Flare, along with one on-water surface-to-surface test. Visibility during both surface-to-air tests was about 40 miles in very light dust/haze and low relative humidity. We also had available generation-three military night vision goggles (NVGs).
Our testing revealed that to be truly effective, the devices must be aimed. Simply scanning with the device— slowly moving it from side to side— was ineffective at anything beyond modest distances of a few miles. Even then, it must be scanned very slowly.
One of our experienced survival instructor volunteers improved on the aiming technique by rapidly “vibrating” the laser from side to side while aiming it at the target, resulting in far more signal flashes on target and about 20% greater range.
Using the standard Greatland Laser aiming technique, the Rescue Laser Flare was visible with the naked eye out to 22 miles in the surface-to-air test, and with NVGs out to 28 miles. Some powerful incandescent flashlights, such as a Sure Fire 6P, provided equivalent or better range when aimed using the same technique, but their white flash wasn’t nearly as distinctive, and their battery life is very short in comparison to even the small Rescue Laser Light.
This range represents the maximum that the laser flash was visible when we knew where to look and when the volunteers on the ground were able to locate our aircraft strobes using NVGs for aiming purposes. For practical signaling use, we’d estimate the surface-to-air range to be 10-15 miles.
It should be noted that the red flash from the laser may not be immediately recognized as a signal of distress by someone who just happens to see it, as opposed to searchers looking for a signal of some sort.
Surface-to-surface range was limited by the horizon. Under clear conditions, the laser will be visible to any line-of-sight boat or ship. For a person in the water in a man-overboard condition, that would be, for example, only 2.8 nautical miles to a pair of eyes approximately 6 feet above the water.
The laser is less affected by visible moisture, haze or fog, than a typical flashlight or searchlight beam, which generates significant backscatter—but it is still attenuated to a degree, and won’t penetrate heavy fog very far.
Greatland Laser claims three miles visibility during daytime. This may be true under overcast conditions, but we were unable to view it at any significant distance in bright sunshine. It may be that daylight conditions are sufficiently different in Alaska, where Greatland Laser is located. We don’t consider this a reliable daytime signaling device, though it may be somewhat useful under the right conditions when a signal mirror would not be.
In our tests, the devices worked effectively for an average of an hour longer than indicated by Greatland Laser before the line started to dim and was extinguished. Their published battery life numbers appear to be conservative.
On The Horizon
We also recently tested a prototype green laser device. While the output from this laser is also limited to 5 mW (with a wider 5-degree angle), our 4 mW prototype was still showing strong to the naked eye at 30 miles, which is the greatest distance at which we had time and resources to test. In fact, it was so extraordinarily easy to see that we used the green laser to identify the location of the testers on the ground at the more extreme distances when we lost the location after a course reversal. It was instantly noticeable when slowly scanned in our direction. Aiming wasn’t even necessary. Because the green laser line is easily visible in the atmosphere, whereas the red is not, no special aiming technique is necessary—another advantage. The green laser wasn’t any more visible in bright daylight.
The reason the green laser is so much more effective than the red is simply that the human eye is many times more receptive to green light— approximately 100 times more receptive, in this instance, to dark-adapted eyes.
There are a few notable downsides to the green laser, however. DPSS (Diode Pumped Solid State) green lasers are considerably more expensive than the ubiquitous red laser diodes, so the green 5-mW “GLAS 2000” (Green Line and Scanner) will have a suggested retail price of $295. It is also an inherently less efficient laser-producing mechanism, consuming a good bit more power, so the 4-inch long production version using a single 123-cell 3-volt lithium battery is expected to have a three-hour operating life—a fair trade-off for the significantly increased probability of being seen, and still better than any similar-sized flashlight with far less range.
Unfortunately, green light isn’t generally recognized as a distress signal. However, it’s so noticeable and unusual that it might well prompt investigation on its own. In an active search-and-rescue mission, the green color won’t matter: Responders will see it at far greater distances, and they will investigate.
A primary use of this laser by the military is to lay down an approach path to a landing zone by creating a long line on the surface of the ground or water leading in. The line has a brighter spot at one end to facilitate such use.
The Rescue Laser Flare, in its various forms, definitely has a place in any mariner’s bag of survival signaling tricks. It offers some significant advantages over pyrotechnic handheld flares for nighttime distress signaling in many circumstances. It is without question safer and more compact; it offers duration of signal that no flare can match. It is, however, still a battery-operated electrical device, with all the potential problems that entails, no matter how reliable.
It is not, in our opinion, a substitute for having plenty of flares on hand. A pyrotechnic flare will, for some time to come, be more immediately recognizable as a distress signal. Nor can the Rescue Laser Flare signal over obstacles, extend its reach over the horizon, or “punch out” of fog or cloud cover. Line-of-sight will always be an issue with any directed signal: It’s good when carefully aimed, but it doesn’t “broadcast” a mayday like an aerial flare.
It can be difficult to aim in an unstable environment, such as heavy seas. The need to use two hands to aim it accurately for best performance is a drawback. When Greatland Laser solves this issue, it will be a better device.
The bottom line is that the Rescue Laser Flare and its siblings are effective signaling devices. Despite their expense, we can recommend them for inclusion as part of your distress signaling gear. We have added a Magnum version to our survival gear, and a Rescue Laser Light is attached to our PFD, right next to the whistle.
All the volunteer testers with us were extremely impressed with the prototype green laser. It was so exceptionally brilliant, and reached out so much farther than the red, as to place it almost in an entirely different category. While it is nearly three times the cost, we’re already saving our pennies. We don’t know of any directed nighttime visual signaling device in a hand-sized package that comes even close to its effective range.
Contact – Greatland Laser, 866-889-3425, www.greatlandlaser.com.
-Contributing editor Doug Ritter is an expert in safety matters. He runs the non-profit Equipped To Survive Foundation. See www.equipped.org.