TACTICAL LASER WEAPONS


One of the most useful applications of tactical lasers may be their use as anti-aircraft weapons. Image copyright Popular Science.

Point-Defense Anti-Missile Lasers
Tech Level: 11
Chemical Laser Cannons
Tech Level: 12
Static Laser Cannons
Tech Level: 13
Free Electron Laser Cannons
Tech Level: 13
Vehicle Anti-Missile Lasers
Tech Level: 14

This article primarily concerns so-called ‘standard frequency’ lasers, those weapons that operate in the near infrared, visible light, and ultraviolet spectrums. Masers and x-ray lasers are handled in their own articles, as are topics like laser firearms, laser dazzlers, space based laser weapons, and laser countermeasures. Links to more technical and detailed explanations of how lasers basically work can be found in the links at the end of this article.

A tactical laser is any laser weapon designed to take out targets the size of vehicles or strategic missiles or larger. During the Cold War, both the US and USSR pursued tactical laser weapons with the intent of using them to shoot down ICBMs.

In 1984, the reality of these programs came starkly to public attention when the USSR fired a ground-based chemical laser at the US Space Shuttle Challenger as a "warning shot" to protest then-president Reagan’s SDI program. The laser merely damaged some visual sensors and dazzled the vision of some astronauts. But it still demonstrated the potential power of such weapons, by being able to hit a target practically instantaneous over two hundred miles up.

Tactical laser weapon research in the US peaked during the SDI projects of the Reagan Administration in the 1980s, and research continued at a slower but steady pace through the decades that followed. Today, two major tactical laser projects are being pursued by the US Military and seem close to producing viable weapon systems. These are detailed later in this article.

There are three general types of laser weapon-chemical lasers, static lasers, and free-electron lasers.

A chemical laser does not use the same population of atoms or molecules over and over to produce its beam, but continuously creates a new energized population of photons through a potent chemical reaction. These atoms are not energized per se, but are created in an energized state as the product of the chemical reaction. After the reaction is complete, the chemical residue is discarded and a new batch of chemicals is loaded for another shot.

A so-called static laser uses a single population of atoms or molecules which are energized by electrical or light input, emit their photons, fall to a lower energy state, and are then re-energized to emit again, over and over. Many modern real life lasers are static lasers, including solid state lasers, ruby lasers, gas lasers, dye lasers, diode lasers, and excimer lasers. The lasers one finds in most appliances, including CD players, supermarket checkout scanners, and laser pointers, are static lasers.

The third broad category of laser is a free electron laser (FEL), and is similar in performance to static lasers, but with one critical difference: it is tunable to almost any frequency. An FEL passes an electron beam through a series of magnets which bend the path of the electrons. As the electrons’ paths are bent, they are made to emit or absorb photons. By placing mirrors at both ends of the electron beam, the photons are gathered coherently to form a beam. Because the electrons are free, and not bound to an atom, they are not locked into any particular quantum energy state, and therefore can absorb or emit photons of any wavelength, depending on how they are manipulated by the magnets. In this way, the FEL laser weapons can be tuned to emit many different beam frequencies at the adjustment of a dial.

Most research programs attempting to create viable laser weapons have so far focused chemical lasers. Practical problems with the storage, transfer, and generation of large amounts of electrical current needed for the other laser types have led to their lagging behind chemical laser development. Chemical lasers produce a population of photons for a laser beam from the quick reaction of two or more chemical substances combining, bypassing the potentially long charge-up time currently needed for static or free-electron lasers. This chemical reaction is also able to create much higher potential energy for a beam than capacitor-fed lasers are capable of right now.

The main disadvantage of chemical lasers is the need for large quantities of potentially toxic chemicals, and dealing with the toxic results these chemicals leave behind after the beam is created. The reason the Airborne Laser project has to be housed in a modified 747 cargo airliner is in part because of the weight and bulk of its chemical fuels.

This can be alleviated somewhat in later Tech Levels by the development of compact chemical laser cartridges, grenade- or artillery-shell-sized or larger units that contain just enough of the chemicals for a single shot, plus a battery or ultracapacitor to initiate the beam and other weapon operations. With these, tactical chemical lasers can be loaded and operated in a manner very similarly to modern day artillery, and the storage and handling of the hazardous chemicals by personnel can be simplified as well. Transportation of the chemicals can also be made safer, though even with armored and hardened cartridges, care in handling will still be required, as a ruptured cartridge cans till prove dangerous.

Static and Free Electron tactical laser weapons will only become a reality after mobile battery and/or ultracapacitor technology allows them to concentrate enough power quickly into a pulse to do significant damage to other vehicles and hardened targets. As it stands now, such capacitor banks that would allow pulses similar in power to the Airborne Laser are even bigger and bulkier than the chemicals the ABL uses, and its cycle rate would be measured in many minutes between shots. Very impractical for a direct-fire weapon in most combat situations.

One solution to this would be the development of Explosive Power Generator (EPG) cartridges, similar to the chemical laser fuel cartridges described above. However, these would contain one or more Flux Compression Generators, which generate high spikes of current through a combination of coiled electromagnets and explosives. A link to an article on EPGs can be found at the end of this page.

Lasers damage different substances differently. With dry materials such as metal and plastic, it simply burns a hole straight through. The more energetic or higher the frequency of the beam, the farther it can "drill" into the material in a single pulse, perhaps even shooting right through it.

The laser will vaporize some of the material, creating a small cloud of particulate around the strike point in a phenomenon called blooming. This blooming effect may inhibit the damage a laser can do by interfering with the beam in a sustained shot, but with the quick pulses generally considered here for tactical weapons, the consequences of it will be minimal.

With wet materials, the story is different. The energy delivered by the beam manifests itself as heat, and the beam pumps a lot of heat into a target all at once. With water, this means an instantaneous steam explosion from the blooming effect.

Organic tissue like skin and muscle are mostly water.

So a laser will NOT make neat holes in the people that it hits. Instead, as the beam hits the skin and the viscera underneath, the water in the tissue blooms instantly into steam very messily, with second and third degree burns on the surrounding tissue. Given the energy potential of these weapons, this would cause a very messy death for anyone fully caught in a beam. Armor may mitigate the damage, but any body part exposed to the beam directly will likely be vaporized down to the bone.

Lasers will also very likely cause dry combustible materials like wood and cloth to instantly burst into flame.

How widespread the beam damage becomes would depend not just on the energy in the beam, but how wide the beam itself is when it leaves the gun. Science fiction likes to portray combat lasers as these pencil-thin beams, but in reality beam apertures can be many inches or feet across and still deliver its full damage. The size of the aperture plays into beam focusing; the wider the beam, the longer its focal length can be as determined by its focusing lenses or mirrors, and the longer the weapon’s potential effective range. The effective range (where the largest percentage of energy for each shot can go into damaging the target damage) would be about twice the weapon’s focal length. The best place to hit a target would be right at the beam’s focal point, but its assumed that in normal combat conditions being able to line up targets at the precise length from the weapon for this to occur will be very impractical. Some laser weapon systems, such as those on Free Electron Lasers, may be able to dynamically adjust their focal length for each shot, but this may add unneeded cost and complication to an already very complex weapon system. Just hitting the target within the weapon’s effective range will usually be considered good enough.

Depending somewhat on beam frequency, a focusing lens or mirror width of a few centimeters is usually enough for an effective range of at least 1000 meters, and apertures of up to thirty centimeters would be able to handle most ranges usually involved in direct fire tactical combat, about ten kilometers or so. ICBM-targeting lasers, which may have to reach a hundred kilometers or more, may need focal lens or mirror widths of a meter or more.

Some laser weapons of sufficiently high energy and frequency may end up destroying their focusing lenses and mirrors. Most weapons would be designed to operate below these thresholds, but in cases where weapons simply have to operate at those levels, sacrificial focusing elements may be used. They may be designed to last just long enough for a single shot, and then swapped out as needed. Very advanced future lasers may use non-material focusing technologies, such as pinpoint gravitic fields, and bypass this limitation.

To clear up another misconception perpetuated by some science fiction sources: You cannot see a laser beam, unless it actually hits a visible object or passes through a visible medium. This is easily demonstrable; get a common laser-pointer, wait until dark, and shine it at a house or a tree across the street. You’ll see a red dot as the laser hits its target, but not the beam itself. You can see it, however, if you spray a fine mist of water from a bottle right in front of the pointer; since the water is visible, the beam that hits the mist droplets are reflected or diffracted, and become visible to the viewer.

So a battle field dominated by laser weapons would not be crisscrossed by colorful, movie FX-style beams. It would actually be far more unnerving, in that the deadly beams are there, maybe crisscrossing just a few inches from your eyes, but you would never be aware of them until too late.

Very high powered lasers are also capable of blinding secondary targets with reflected light. In other words, if a laser hits a target, the flash of the beam striking may render victims nearby temporarily blind even if they aren’t hit by the beam directly. There are a lot of variables to this, such as intensity of the beam, angle of reflection, reflectivity of the target surfaces, and so on, but it’s a real danger. Some large laser weapons may even come with a low-power option for the express purpose of blinding enemy targets directly.

Laser beams are not affected by wind or gravity the way bullets are, and there is no projectile drop or drift to calculate for very long-range targets. And on the scale of most terrestrial battlefields, a laser beam will hit its target instantaneously. These features make lasers an attractive weapon for both main battlefield tanks and attack aircraft, or any fighting vehicle that may need to go toe to toe, so to speak, with enemy armored vehicles.

Science fiction also tends to show large laser weapons as long-tubed guns, similar in appearance to conventional artillery but with a sleeker more high-tech look. This is only one possible configuration for such weapons, however. Since the beams themselves can be reflected and refracted within the weapon, it doesn’t necessarily need a long barrel for it to achieve proper focus for its beam. In real life, experimental US and Soviet laser cannons have tended to look more like enormous spotlights, with beam apertures from a few inches to many feet across.

DISADVANTAGES

One of the main disadvantages with these heavy weapons is that indirect fire with lasers is impossible; obviously one cannot curve a beam of light over the horizon or other obstacles using gravity.

It may be possible to set up indirect shots using mirrors, and parabolic mirrors may even be used to help re-focus the beam to hit targets that may normally be outside its nominal effective range. These mirrors wouldn’t be the big polished ones most people are used to, but monochromatic mirrors, that will reflect only the frequency of the laser’s beam and appear matte black to all other wavelengths of light. However, setting up these bank shots would be extremely complicated, and may be completely impossible under most battlefield conditions. It may be possible to use this kind of tactic for an ambush, if the monochromatic mirrors can be hidden or camouflaged effectively.

Lasers can also be at the mercy of bad weather. Rain, fog, snow, and other conditions that obscure visibility will also degrade the effectiveness of a laser beam. Depending on the power of the weapon, it likely won’t stop the beam from reaching its target, but all that particulate it has to punch through will sap energy away from it, diminishing from its potential target penetration and damage. Also, beams using visible light frequencies would be visible in these weather conditions, making tracking them back to their source much easier for the other side.

Units aware that the enemy is using lasers can also employ specially-made countermeasures, such as smoke generators and smoke bombs, as well as aerosol sprays to put fine reflective particulate into the air to help scatter incoming beams. This is more fully detailed in the article Laser Countermeasures, linked to at the end of this article.

A WAR OF FREQUENCIES

The ultimate effectiveness of any laser weapon on the battlefield will be determined by its range of operational wavelengths.

When these weapons first start becoming widespread, many will find it a marvel that they can deliver such devastating damage at all. However, as the weapons become more common, combatants are going to find that certain frequencies work better for some targets than for others, and defenses may become customized to defeating preferred weapon frequencies of the enemy.

For example, the eye is transparent to frequencies of light in the near-infrared, but they don’t invoke the eye’s protective blink reaction. So for laser weapons whose intent is to blind the enemy, this would be the preferred frequency of operation.

However, many substances will absorb and distribute infrared radiation (heat) much more efficiently than others, such as many metals. So in order to be more effective against targets armored with these metals, higher frequencies such as UV lasers may be warranted.

More, the atmosphere is very absorptive of many frequencies of UV and IR light, degrading their potential range and damage. Visible light lasers will usually be able to reach farther and deliver more damage than either over long ranges within Earth’s atmosphere. If in the far future tactical laser weapons are used on other worlds with different atmospheric mixtures, other frequencies optimized for these alien environments may need to be used.

Enemy defenses such as aerosol sprays may be opaque to some frequencies of laser (such as those used by the enemy) and transparent to others(such as those used by friendlies.)

And there are a number of other circumstances as well of one frequency of laser working better than others. This all points to laser weapons capable of adjusting their frequency as being much more versatile and effective on the battlefield than those that can only cleave to one preset wavelength. This is not to say that single-frequency lasers would be ineffective, only that adjustable multiple-frequency lasers would give a fighting force that much more of a potential advantage.



POINT DEFENSE ANTI-MISSILE CHEMICAL LASERS
Tech Level: 10
An experimental US military point-defense laser turret.

These were the true goal of laser weapon programs during much of the Cold War, both by the United States and the Soviet Union. The idea was to place these lasers near vital strategic assets, such as ICBM silos and military bases, and use them to disable incoming enemy nuclear warheads before they could detonate. Various treaties, and then the end of the Cold War, put an end to these projects, and the technology was repurposed toward mobile laser cannons.

These point-defense lasers would be housed in ground based turrets and immobile mostly because of the enormous amount of chemicals needed for multiple sustained shots, and the amount of such required to produce a beam energetic enough to drill through hardened ICBM warheads many miles up.

Even that might not be enough, however, as it was generally assumed that the beam would need to track and follow each falling warhead for at least half a second to do its job, possibly longer. So these weapons would also need to be attached to very sophisticated sensors and tracking software to ‘follow’ the warheads for the time needed. This latter consideration proved almost as daunting as the creating the laser itself, especially to researchers in decades past. However, modern computer technology has caught up to that requirement, and it is now being used to make harder-to-aim mobile systems like the Airborne Laser possible.

The targeting task would be more complex than many assume; most nuclear weapons were designed to be air burst weapons, and would detonate a mile or more high to maximize its spread of damage. So an anti-ICBM laser would have to track and target the incoming warhead before it reached that threshold. Most nuclear missiles in the late Cold War era carried multiple warheads, along with decoy warheads. And because they were hardened against reentry heat, lasers would need to track them longer in order to effectively take them out. So in order to be fully succeed, the lasers would have to hit multiple targets in quick succession, and pack enough power in each shot to punch the beam through a re-entry heat shield.

As an alternative to destroying the target outright, these lasers could also have been deployed with a tactic called dynamic pulse detonation. A laser focused on a specific spot in the air will superheat the gasses there, creating a super-hot ball of plasma called a plasmoid. A second laser focused on the same spot a split-second later creates a supersonic shockwave within the plasmoid, resulting in an explosion.

Because of the energies these laser weapons would pack, well into the megawatt range, the resultant explosions could prove fairly potent, but probably not enough by itself to significantly damage an incoming warhead. However, the lasers could produce many plasmoid explosions in quick succession directly in front of the falling warhead, possibly throwing it off course and/or causing it to tumble. While diverting a warhead a mile or so away might not necessarily be a distinct advantage when dealing with nukes, this tactic could still be very effective against conventional missiles and other types of high-altitude-to-ground weapons, such as incoming artillery shells and even the "Rods from God" impactors.

These weapons could also be used to take out enemy aircraft, and could even be used to blind optical sensors on low-orbiting satellites.


CHEMICAL LASER CANNONS
Tech Level: 12
Smplified diagram of the Airborne Laser.

The Airborne Laser (nowadays more formally called the Boeing YAL-1 Airborne Laser Testbed) and the Advanced Tactical Laser (ATL) programs currently being developed by the US military will be the progenitors of mobile chemical laser cannons. Both are airplane mounted, the difference being that the Airborne Laser is designed shoot down missiles in their boost phase, while the Advanced Tactical Laser is designed for use against ground targets.

The Airborne Laser is a much larger, more robust system than the ATL, operating in the megawatt range, compared to the ATL’s kilowatt-level shots. The Airborne Laser has to hit targets over much larger ranges, which will be moving at fairly high speeds relative to itself, so it has to pack a much more potent punch to ensure a kill with a single pulse. The ATL, which will be targetting stationary or slower-moving ground targets, can make do with less beam strength.

Both systems use large, heavy Chemical Oxygen-Iodine Laser systems to propagate their beams. The ATL system weighs over 3000 kilograms and has to be housed in a C-130 cargo plane. The Airborne Laser system is three times as massive and has to be housed in a 747 cargo liner, taking up about as much space as six SUVs.

The laser systems usually run most of the length of the airplane fuselage, with a gimballed turret composed of a wide focusing mirror directing the actual laser beam to the target. On the ATL this is located in the belly of the aircraft; in the Airborne Laser its located in the aircraft’s nose. Secondary targeting lasers illuminate and read the distance to the target, so that the system can adjust the energy and focusing of the beam as needed.

Both systems have been able to track, hit, and destroy targets in ongoing field tests, proving the potential viability of the technology. However, there have been very serious doubts as to these systems’ actual battlefield practicality and cost effectiveness, at least in the near term. For one, their size, bulk, and chemical fuel make them very expensive systems not only to develop, but to maintain and operate as well, especially in a mobile platform.

For another, the Airborne Laser is specifically designed to be used against ballistic missiles in boost phase, when the targets would be most vulnerable. However, getting an Airborne-Laser-equipped aircraft within range of a potential launch at just the right time could prove problematic. A fleet of such planes, placed strategically around an enemy’s territory and constantly flying patrols could solve the problem, but creating such a fleet would prove prohibitively expensive even after the Airborne Laser is fully developed as a mature technology.

The Advanced Tactical Laser has a bit more of a mundane quandary. Though also a workable system, what it does—targeting and neutralizing ground targets—can be done by currently existing technology more cheaply. On the surface there would seem to be little going for it as a weapon system.

However, the ATL’s one big advantage over other systems would be pinpoint targeting—it would be able to hit very small targets instantly over very large distances, making its potential killer app, so to speak, anti-personnel. For example, a controversial modern US operation targets high-ranking members of terrorist organizations using missiles that cause a lot of collateral damage. An ATL-equipped aircraft could theoretically target a single person from miles up, and take him or her out while doing very little damage to surrounding bystanders or buildings. They could also be employed on the battlefield, and used specifically to take out officers or artillery crews or other vital enemy personnel. However, the idea of just randomly ‘zapping’ people from on high, especially with weapons that could produce very messy results like high-powered lasers, would be abhorrent to many people no matter the rationale and the resultant potential political firestorms may kill such applications before they even start.

More advanced versions may reduce bulk and expense by using a chemical cartridge system for ammunition, though operators may lose some ability to fine-tune shots according to power.


STATIC LASER CANNONS
Tech Level: 13

Chemical lasers may have proven the concept of heavy tactical lasers, but it seems they might not be very practical for mobile applications because of the bulk, weight, and large amount of chemical fuels involved. Eliminating the need for the chemicals with a more traditional static laser system would greatly reduce the size and cost of such systems, and would make them much better suited for mobile platforms.

The missing variable for this would be compact power systems that can generate sufficient energy to make a mobile laser cannon worthwhile. Powering a static laser cannon on a vehicle can be done in three general ways: through a dedicated power plant or energy storage unit; by drawing from the vehicle’s main engine; or through explosive power generator (EPG) cartridges.

A dedicated generator or battery array for the weapon would be the most straightforward method. These could take the form of a second engine, a fuel cell array, conventional batteries, flywheel batteries, compulsators, or ultracapacitors. Very advanced future options could include compact nuclear reactors (fission or fusion) or supercapacitor coils. Most of these would add extra weight, cost, and bulk to the vehicle. However, a dedicated generator or energy bank for the weapon would likely ensure much longer performance and more overall shots. It would generally not be a good idea for a vehicle that usually gets into fierce but brief engagements, such as fighter aircraft. But for others that may have to be in engagements for relatively long periods of time, like spacecraft, it may be a wise investment.

Laser cannons could also draw power from the vehicle’s main engine or engines. If this is the case the engine would likely designed to be over-powered enough to both drive the vehicle and power the cannon at the same time, at least to a point. When such systems were employed in the real world, the vehicle is often designed to lose some driving power when the weapon is engaged, and would likely be the case with a static laser cannon as well. This often results from trade-offs designers make with performance, endurance, cost, and other factors when engineering a vehicle.

Vehicles that normally have large and powerful engines, such as naval vessels, may best benefit from this arrangement.

Such cannons may also use large or multiple-stage EPGs, which would be packaged and used very similarly to modern day artillery shells. They would be loaded in, triggered to initiate the current for the beam, then the waste gasses and the remains of the cartridge would be expelled to make way for the next round. With automated loading systems, this would allow for fairly rapid pulsed fire. This would be advantageous for aircraft, main battle tanks, and dedicated laser cannon artillery pieces.

Generation is only part of the power equation for these weapons, however. Also needed would be rapid charging and discharging capacitors or their higher-tech equivalents for each individual shot. Ultracapacitors, as well as flywheel batteries and compulsators, could fill this role.

Static laser cannons would be useful in a number of applications. Once fully mature, the technology would almost certainly be the short-range air-to-air option of fighter aircraft. They would have far more range than any type of conventional gun, would be able to hit the target instantly, and would have no recoil that may work against the aircraft’s movement.

Because of their range and instant hit capabilities, they would also be useful as ground-based anti-aircraft weapons.

Static laser cannons would also find a niche on secondary ground fighting vehicles, allowing smaller and more lightly armored ones, such as APCs, to field more potential direct firepower.


FREE ELECTRON LASER CANNON
Tech level: 13

Free Electron Laser (FEL) Cannons would operate and be deployed very similarly Static Laser Cannons. The main difference would be that FEL lasers would have a much broader range of adjustable frequencies it could choose from, and could change between them more easily. This would make adjusting to weather conditions, enemy defenses, and shifting tactics much easier, as detailed above.

Though FEL cannons are the same Tech Level as Static Laser cannons, they are in general harder to engineer and thus likely would remain more expensive and complicated than their cousins. Thus their deployment on a vehicle class would always be weighed against cost considerations.


VEHICLE ANTI-MISSILE LASERS
Tech Level: 14

A laser cannon’s most important application may not be as an offensive weapon but as missile defense. At first, because of the bulk required for even Static or FEL lasers of sufficient power, only larger vessels such as naval vessels and spacecraft could benefit from this. But as power sources and the lasing systems themselves become more compact and potent in later Tech Levels, they may be able to be fit on almost any sized vehicle.

A vehicle’s sensors would pick up an incoming missile. High-speed processors would allow the laser cannon to track and strike the missile before it gets within range of the vehicle. However, this often would happen so quickly that human operators of the vehicle wouldn’t have time to react themselves, meaning the system would have to be completely automated. While this may not seem like a potential disadvantage, it would also mean that the computer tracking system would have to be sophisticated and smart enough to distinguish an incoming enemy missile from friendly units, such as personnel, aircraft, and missiles from friendly sources passing through to other targets.


FURTHER INFORMATION

http://www.howstuffworks.com/laser.htm

http://www.usatoday.com/tech/science/2010-05-14-1Adeathray14_CV_N.htm

http://news.cnet.com/8301-11386_3-10024153-76.html

http://www.popsci.com/military-aviation-space/article/2006-05/attack-speed-light

http://www.orbitalvector.com/Firearms/Laser%20Firearms/LASER%20FIREARMS.htm

http://www.orbitalvector.com/Firearms/Laser%20Dazzlers/LASER%20DAZZLERS.htm

http://www.orbitalvector.com/Firearms/X-RAY%20LASER%20FIREARMS.htm

http://orbitalvector.com/Firearms/Laser%20Countermeasures/Laser%20Countermeasures.htm

http://www.popsci.com/node/19965

Airborne Laser

http://www.mda.mil/system/altb.html

Advanced Tactical Laser

http://en.wikipedia.org/wiki/Advanced_Tactical_Laser

Explosive Power Generators

http://orbitalvector.com/Power/Explosive%20Power%20Generators/EXPLOSIVE%20POWER%20GENERATORS.htm


Article added 3/16/11

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