The Laser And The Modern Battlefield
Douglas Bunger, ©1988

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Since the first stone was thrown thousands of years ago, man has been attempting to develop more efficient ways of killing his enemies. Someone thought up the bow and arrow to hunt food and, shortly there after, someone used it to kill a man. One thing led to another, man invented the gun, the howitzer, the tank, and before too long the nuclear missile. To the trained eye, everything has potential as a weapon. So when the laser was invented, it was not surprising that someone asked how it could be used as a weapon. What is a laser? How is it used on today's battlefield- and how will it be used tomorrow?

Laser is actually an acronym for Light Amplification by Stimulated Emission of Radiation. A light bulb radiates light in all directions. If you were to place a mirror next to the bulb it would reflect the radiated light to one side of the bulb. A flashlight uses a curved reflective surface to reflect and focus the light. A laser works by bouncing the light between two mirrors, one called the exit mirror that is similar to a one-way mirror. As this happens the light is not radiated in all directions, but all shines in the same direction. The light will continue to reflect and focus until it has gained enough power to "punch" through the exit mirror in the form of a coherent beam of light. Thus, it expands very little when it travels and has compacted its energy into small area.


By placing a shutter behind the exit mirror, the beam can be held inside to allow it to continue to gain power. This allows the laser beam to be pulsed. The speed at which the beam is pulsed is known as the pulse rate. By allowing the light to gain power, it can achieve destructive potential.

The most common vision that comes to mind when people think of a laser is that of Captain Kirk using his phaser to disintegrate Klingons. The lasers we have now are too low power for that. So how effective are they as weapons?

The laser projects a concentrated, extremely intense beam of light. Its mass (force) is so small, that it is non-existent to all but the scientists. The only way a laser can destroy an object is to focus light of such intensity that it burns a hole through it. The laser beam itself cannot cause an explosion. If a laser beam was fired on an air tight metal target, there is the possibility that the heat of the beam could warm the air inside the target, causing it to expand rapidly, and pop like a balloon. The chances of this happening on a tank are small since the laser would burn through the hull before heating the air sufficiently. Once the hole is made, the air escapes and any shrapnel generated is blown out through the hole (the primary round used by American tanks does not explode, but slams into the target with such force that the target shatters and turns to shrapnel that does most of the destruction).

As you can see, a laser is not very useful against a tank. The Air Force is having good luck using the laser as an anti-aircraft weapon. They have mounted a high power carbon dioxide laser in an NKC-135 (modified Boeing 707) that is known as the Airborne Laser Laboratory, or ALL. The laser is used to burn through the skin of another aircraft and destroy internal components, thus downing the target. Furthermore, if they are able to fire on an aircraft from the side, bottom, or top, there is a possibility of dissecting the aircraft. The ALL has successfully downed several Sidewinder air-to-air missiles which are 9 feet long and 5 inches around.


To utilize the laser as a weapon on the battlefield it is necessary that the laser be very powerful. But today, and probably for the next several years, powerful means big. Because a target the size of a 707 would not survive long in battle against tanks, artillery and anti-tank weapons, we will have to think smaller. Using small hand-held lasers as can openers to get into tanks is not practical, because once the tank crew realized what you were doing, they would not stick around for the fun.

There is one more possibility. Take a lump of raw hamburger and put it in the microwave for about five minutes, after a while it will start popping, and at the end of the five minutes you may have quite a mess to clean up. The laser's intense heat could have the same effect on the human body, causing a small section to burn and explode (it's the grease in the fat that causes it to pop), thus wounding the enemy soldier. This may sound good, but as the laser's beam passes through the air it looses energy by colliding with air molecules. Because of this, the effectiveness diminishes rapidly with distance. The weapon would have a range about the same as a combat rifle but would not be as rugged and could cost thousands of dollars more. This too, does not seem like a practical, cost-effective weapon.

Since the early seventies, both the military and the scientists have realized the laser's potential as a guidance device. The publics first exposure to the laser in combat, was in 1972 when the Air Force used a Laser Guided Bomb (LGB) to destroy the rail bridge at Thanh Ho, in North Vietnam. Several attempts had been made to destroy the target using conventional bombs and rockets, but none had had sufficient effect. The problem was to strike the bridge in one of its main supports. Texas Instruments provided the answer with the GBU-10 Paveway LGB. This weapon is a bomb that is released from an aircraft and glides to its target. Controlled by fins on its tail section, it homes in on a laser beam that is projected on the target. By shining the laser onto the bridge's main support, the Air Force scored a direct hit.

Generally, there are two types of laser guidance: laser homing and beam riding. Both concepts rely on the laser's ability to project a thin, straight beam of light. With laser homing, a "designator" projects the beam onto a target. The missile has a sensor mounted in its nose that detects only light of a certain wavelength and pulse rate. When the weapon locks onto the laserlight, it will continue to home in on it until the light is turned off, or there is an impact. The disadvantage to laser homing is that smoke generated around the target could obscure the laser's beam, thus causing the missile to loose its lock-on. In this case the missile will continue on a straight line and hope for the best.

The beam riding system is almost the opposite of laser homing. The laser is shown on the target and the missile is fired. A beam rider has its sensors in the tail looking backwards towards the launcher and attempts to stay on the beam. Since there is no need to lock-on, and its sensors have a narrow field of view, the beam rider is less susceptible to jamming by smoke, fog, rain and dust; all common on todays battlefield. The disadvantage of beam riding is that it requires the launcher and laser to be in the same place, unlike the Copperhead Anti-Tank Round.

The Martin Marietta M-712 Copperhead is a new concept in anti-tank weapons. It is known as a Cannon Launched Guided Projectile (CLGP) and is fired from a 155mm howitzer. Artillery has traditionally had little tank killing ability, the chances of a kill using indirect fire are about 2500 to 1. The odds are better when firing directly on a tank, but the rate of loss for the artillery is ten times normal (people often confuse the M-109 self propelled gun as a tank, but officers are trained not to try to outgun a tank, because if you miss, he won't). When a target is found, the forward observer calls for a Copperhead and gives an approximate position and the round is fired in the general vicinity of the target. The observer is instructed when to illuminate the target with his Ground Laser Locator Designator (GLLD). The CLGP senses the reflected laser energy and glides to the laser spot. The Copperhead will hit, even if the target moves, as long as the dot is on the tank. Tests have shown that the Copperhead is accurate within two feet.


The biggest advantage to the CLGP is that the weapon is not fired from the same place that it is sighted from. When the TOW and Dragon guided missiles are fired, there is a large blast from the launcher. This reveals the position of the firer and gives the target a chance to fire back or run for cover. If the target is able to hit the firing unit before the missile hits him, then the missile will go wild and miss. With the launcher (a howitzer) well out of range of the target, it cannot be hit by return fire. Furthermore, it would be well beyond earshot and, as far as the target is concerned, virtually silent. This would make it a good ambush weapon. A small, fast recon vehicle equipped with a GLLD could easily kill a platoon of tanks in an open area such as a hiway, plane, or dessert, with out fear of engagement.

The first wide scale use of the laser for military use was the laser range finder. By projecting a pulse of laser light on to an object, and measuring the time and intensity of the reflection, the rang finder's computer can calculate the distance to target. The Army's present model, the GVS-5 can be used to range targets with accuracy of 10 meters in less than one second. It weighs about 5 pounds and is smaller than a football.

The laser range finder plays an important part in modern armor combat. When the M-60 tank was first introduced in the late '60s, it was equipped with Optical Coincidence Ranging. The gunner looked into a set of eyepieces that viewed the target from two different angles and turned a handcrank until the two images were superimposed. The range was displayed in a window and through a system of gears, applied to the main gun to compensate for the effects of gravity.

The M-1 Abrahms tank is equipped with a new laser range finding system, that allows for faster targeting and more accurate firing. The gunner places the crosshair on target and presses a button. The laser calculates the range and applies the necessary adjustments to the gun. A squeeze of the trigger, and the round is off. The Abrahms tank is the first American tank that can fire on a moving target while it is moving. The Army has been adding several modifications to the M-60A1 tanks changing them to M-60A3's. One of these modifications is laser range finding system.

Because the laser's beam is pulsed, it cannot be seen in adverse conditions such as fog, rain, or smoke. The pulse rate however, is not compatible with the pulse rate of the Laser Guided Munitions (LGM, the general term that describes all types of laser guided weapons). Although it hard to believe that scientists could not make the two compatible, it is true. When the British were fighting in the Falklands, they attempted to use a laser range finder on a Hawker Harrier to designate a target for a Paveway LGB launched from second Harrier. The LGB's sensors could not "see" the laser and as such did not lock-on.


In recent years the laser has found a place in the world of small arms. This is in the form of the Laser Gun Sight. A small low power laser is strapped onto a weapon, typically an assault rifle, in line with the barrel so as to shine a laser dot on the target. It is the general belief that this increases the riflemans accuracy. Nothing is farther from the truth. The rifleman is instructed to "simply place the dot on your target and pull the trigger- the bullet will hit the dot." The assumption here is that either the bullet travels in a straight line, or that the laser beam curves to match the tajectory of the bullet.

Consider the M-16 combat rifle firing a 5.56mm (.223 cal) bullet. If the rifle were mounted with the barrel level, the effect if gravity would cause the bullet to drop as shown below.

Target distance (yds)   50   100   150   200   250   300   400   500

Bullet drop (inches)   0.4   1.8   4.5   8.4  14.3  21.5  44.4  81.8

Laser drop (inches)    0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0
As you can see, the farther the target, the farther the bullet and dot are apart. Furthermore the laser beam does not get larger with distance like a flashlight beam, but instead would remain the size of a dime out to 500 yards. At 300 yards, a man appears to be about one inch tall, imagine trying to see a dime at that same distance. The logical solution is to supplement your laser with a rifle scope, to magnify the laser dot at long range. If, however, you do place a scope on your weapon, then you may as well use the crosshair.

This brings up a few more flaws with the laser rifle scope. First it does project a bright, glowing (usually red) dot onto your target but what most people don't realize, is that if you can see it, so can your target. Imagine two enemy sentries on guard, when one says to the other: "Wow, you should see the funny red dot on your in the middle of your face." More than likely, upon seeing the dot your target will jump for cover. Second is that since the beam must remain on to provide a constant dot it cannot be pulsed. This means that in fog, rain, or smoke the beam would be visible- one end is a dot on your target, the other end is an arrow back to your weapon. All your target needs to do is fire at the beam's source and he's got you.

Because the laser sight is not of any military use in medium to long range all weather combat, what good is it? It is one of the best methods of rapid target acquisition (aiming). In close quarters combat, the laser allows the soldier to fire from the hip with both eyes open. The bullet hits the dot (the chart shows the effects of gravity are too small to matter at less than 100 yds). Does this mean we can expect to see laser rifle sights on the battlefield of the future? Probably not. At over $300 each the sight would cost more than the rifle. Additionally, most combat veterans learn to shoot from the hip quickly; after all, their life depends on it.

Another military use of the laser is in combat training with a system known as Multiply Integrated Laser Engagement System, or MILES. A very low power laser is attached to the barrel of an M-16 rifle and is set to pulse only when a blank cartridge is fired. The soldier also wears a harness of laser sensors that are connected to a central computer. If a soldier is hit by a laser beam, which simulates a bullet, the sensors detect the reflected laser light and tell the computer to sound an alarm. The computer is also connected to the laser on the rifle, so when there is a hit, the laser will not function, thus keeping a "dead" soldier from firing. The system is an excellent training aid because it teaches soldiers to move under fire without getting shot. The better trained the soldier is, the more likely he will survive combat.

The lasers potential is not limited by the topics discussed here, but the laser of today is not that different from the lasers of thirty years ago. The size and power have increased dramatically, but sufficient progress has not been made to make the "Ray-gun" a practical weapon in this century. For the laser to be an effective weapon, its destructive area will have to be increased from the size of a nickel to the size of a basketball, and the device and power source must by able to be carried in a backpack or on a jeep. Furthermore, the Laser Rifle Sight falls prey to the bureaucratic term: cost effective. These systems are only as good as a conventional rifle scope but cost ten times as much.


The biggest growth in laser combat will definitely be in the guided-missile/targeting catagory. The first step will be to standardize the range finders and designators, and make them at a cost and size that will allow it to be issued to each platoon. The next step will be to deploy "Rat Patrol" type ambush units that could operate behind the lines, thus preventing the enemy from having a safe place to rest, refuel, and repair.

By developing missiles that give the modern soldier the firepower of a small tank, and guidance system that allow him to effectively engage targets before they can engage him, we can increase the versatility and effectiveness of our troops.


Sources:
Ballistics data interpolated from Federal Ammunition Co
The Concise Encyclopedia of Science and Technology
FM 7-11B Infantryman Soldiers Manual
FM 6-30 Observed Fire Procedures
Advanced Technology Warfare
The US War Machine

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