LASER FIREARMS


A military scientist operates a laser in a test environment. Image courtesy Air Force Research Laboratory.

Chemical Laser Firearms
Tech Level: 13
Static Laser Firearms
Tech Level: 14
Free Electron Laser Firearms
Tech Level: 14

This article concerns itself mainly with "standard frequency" lasers, those that operate in the near infrared, visible light, and near ultraviolet spectrums. Masers and X-ray Lasers will be discussed in their own articles, as will Laser dazzlers, tactical lasers, space-based lasers, and laser countermeasures.

Experiments for producing practical laser weapons have been ongoing for decades by many different nations and private interests. Currently the Airborne Laser project by the US Air Force, which uses a large chemical laser embedded in a specially-modified 747 meant to shoot down missiles, is the closest to fruition such a project has ever achieved. Lasers as infantry weapons and everyday firearms may be many decades off yet, but the Airborne Laser and similar project does demonstrate that such weapon systems are possible.

BASICS

Lasers work by stimulating populations of atoms into repeatedly emitting photons of a certain frequency. Listings of in-depth articles on the exact physics and workings of lasers can be found in the Further Information section at the end of this article.

Numerous laser toys, tools, and range finders already exist today in the real world. But the question always emerges: where are the actual laser weapons?

The quick and easy answer is, its a matter of power. In order to produce enough of a punch to do at least as much damage as a medium-caliber conventional pistols, a laser must propagate a certain level of output energy (starting at around 1.5 to 2 kilojoules) near-instantaneously at the pull of a trigger. Weaker lasers can do damage by firing on a continuous beam on the exact same spot on a target for several seconds at a time, which may be good for mechanical or medical applications but is extremely impractical for actual combat. While the controlled chemical explosions found in conventional rounds can easily deliver this much mechanical punch to a bullet, pumping 1.5+ kj into a millisecond laser pulse with a contemporary battery or generator small and light enough to fit into a pistol or a rifle has proven to be quite daunting.

It would be theoretically possible to create a laser rifle today that can produce a 2+ kilojoule pulse-if the user did not mind lugging around a bulky and heavy portable generator and capacitor bank, and was willing to wait up to several minutes while the weapon recharged between shots. Quick-recharge ultracapacitors as well as more advanced and compact energy storage technology such as flywheel batteries may help to alleviate some of this burden in the next few decades, allowing for a more practical rate of fire and a soldier to carry the power source for his laser weapon in a man-portable backpack or half-pack. While a number of science fiction sources have laser weapons with precisely these kind of power sources, usually attached to the weapon via long power cords, the burden of the backpack and the cord would likely be something most users, especially battlefield soldiers, would rather not bother with.

Laser firearms may not become truly practical for combat until the development of compact energy sources, such as Explosive Power Generator (EPG) cartridges, which is estimated to be at Tech Level 14 (circa 75 years from now.) These would eliminate the need for a bulky exterior power source. EPGs could provide the very high current on a moment’s notice that these weapons need, and can be configured and used very much like modern day ammunition cartridges. Up until that point, laser arms will likely remain in the realm of vehicle and point-defense weapons, and man-portable versions will be rare prototypes.

Other, more potent and lightweight portable power sources may become available at higher tech levels than EPGs, allowing much better and smoother performance, like that seen in many scifi sources.

Another somewhat significant hurdle with laser weapons is focusing. Lasers, like most light, will spread out over distance, though dispersion of a laser beam is much less for any given distance than for conventional light. Laser focusing is usually done with specially-designed mirrors, and getting these to focus and align the beam to reach long ranges and still deliver significant damage has proven difficult. While not so much a problem for hand-held weapons (which would usually only have to function over distances of at most 1000 meters during personal combat), this was one of the major problems with strategic laser weapons developed for SDI, which had to deliver significant damage over hundreds of kilometers or more.

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 infantry 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 gun will NOT make neat little 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, causing third and second degree burns in much of the surrounding tissue. This may be made even worse by tough clothing or armor, which would trap the steam and spread it over a larger portion of the body than it would otherwise reach. How widespread the steam damage may be would depend on the energy in the beam. Low-powered beams will create small localized damage, while very high-powered beams will propagate very violent steam reactions that could spread over most of a victim’s body, inside and out.

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

To clear up another misconception perpetuated by some science fiction sources: You cannot see a laser beam, until 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 a 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 laser weapons may even come with a low-power option for the express purpose of blinding enemy targets directly.

Laser weapons tend to have a very low firing signature. There is no muzzle flash and their operational noises would be no louder than a cough or the hum of your computer. Trying to pinpoint incoming fire would therefore be much harder than with conventional arms. A battlefield dominated by laser weapons would tend to be fairly quiet compared to modern battlefields, making things even more nerve-wracking for the future soldier. Invisible, laser-borne death may hit you at any moment, and even the people standing right next to you may never figure out exactly where the shot came from.

Laser weapons also have no recoil, making repeated fire much easier with them than with conventional arms. Lack of recoil also makes them ideal weapons for use in microgravity environments, such as space stations and ships. Shoulder stocks and such will probably still be present, however, to offer stabilization for precision fire.

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 infantry battlefields, a laser beam will hit its target instantaneously. This combined with their other stealth advantages may make lasers into the choice sniper weapon of the late 21st century and beyond, even if competing arms technologies at Tech Level 14-plus may offer other advantages for the everyday soldier.



DISADVANTAGES

For all their abilities, laser firearms would have some significant drawbacks. Two of these, maintaining effective beam focus at long ranges and the need for man-portable high-current power sources, have already been addressed. However, these are assumed to be purely technical hurdles that can eventually be overcome.

More of a problem is the nature of the weapons themselves. Fighting a battle with what are basically very high-powered light sources can prove a tricky endeavor.

For example, lasers can 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, and 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.

Friendly fire issues also arise, as an accidental shot that doesn’t directly hit a friendly might still blind him or her with a nearby indirect hit. For their own safety, personnel outfitted with laser weapons would need to wear protective eyewear or visors.

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 going operational, 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 on Earth’s surface.

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.) If lasers are used on board a spaceship or station or other circumstances where breaches may be very undesirable, the bulkheads may be coated with substances designed to scatter the laser frequencies the defenders would use.

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.


CHEMICAL LASER FIREARMS
Tech level: 13

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 which emits its photons and is then discarded. These atoms are not energized per se, but are created in an energized state as the product of a potent chemical reaction.

Chemical lasers have had the most success in real-life directed energy weapon research to date than any other type of laser. For example, a chemical oxygen-iodine laser is at the heart of the Airborne Laser project and has been used, at least in field tests, to shoot down actual targets.

For man-portable versions, chemical reaction cartridges which produce the right type of energized population can be made modular and self-contained, allowing them to be fed into the gun and then ejected in much the same way as standard ammunition. These would predate similar-working EPG cartridges by one Tech Level, and their development might be a necessary precursor to the development of full infantry-weapon-compatable EPG cartridges. However, instead of producing spikes of high electrical power, these chemical reaction cartridges would primarily produce the energized gas needed to produce the laser beam. They could also provide the seed current for the gun’s firing operations through a small enclosed battery or ultracapacitor in a cartridge clip’s base.

Chemical laser have only limited variable-frequency options. Beam wavelengths can be altered somewhat by altering the chemicals used to produce the laser population. In other words, if someone firing a chemical laser weapons wants one frequency, he’d use one set of cartridges, and if he wants another frequency, he switches to a different kind of cartridge. Different lenses or prisms placed at the beam’s firing aperture could also alter its frequency.

Another drawback is the chemicals these types of lasers use are often quite toxic, and a mishap with the ammunition cartridges could prove to be very hazardous to the user. There’s also the issue of cost, storage, and transportation of large quantities of potentially hazardous chemicals for any military planner to consider.


A chemical laser firearm fom the Traveller RPG universe. Image copyright Fra Future enterprises.

STATIC LASER FIREARMS
Tech Level: 14

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. Discounting the power source problem, a static laser is probably the cheapest means of creating a practical man-portable laser weapon, as it is a well-used and proven technology.

It would be possible to create a static laser firearm at Tech Levels lower than 14 using externally-carried power sources, such as flywheels or ultracapacitors in a backpack and attached via power cord. However, this places a great deal of additional burden on the user and can be awkward to handle. Given other almost-as-good and easier-to-use options at these tech levels, including advanced conventional firearms and ETC weapons, armed forces and other interests would probably opt not to invest large sums of money in these weapons until they come up with a small enough power source that can make lasers handle comparably to modern firearms, such as EPGs.

Static lasers can change frequencies by two general methods: by attaching a modular prism or lens to the beam outlet, or by using variations of dye lasers, which use certain types of complex liquid organic dyes (such as rhodamine 6G) as their energizing population.

The main advantage of a static laser firearm over a free electron laser (FEL) weapon, which also becomes available as a firearm at Tech level 14, would be cost. Static lasers are much easier to produce than FELs, and would likely be the type of laser weapons given to infantry troops, at least until the cost of the latter came down.


FREE ELECTRON LASER FIREARMS
Tech Level: 14

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 in the usual fashion. 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 actually be tuned to emit different beam frequencies at the adjustment of a dial. Given a sophisticated enough weapon and the right training, a user can tune an FEL firearm to any frequency he may need.

As stated earlier, FEL firearms will likely be more expensive than static laser firearms, simply because they’re harder to engineer. In today’s world, static lasers are already a mundane everyday technology, but FELs are still prototype lab equipment. When they first come online as man-portable weapons, they’re likely to be the cadillacs of laser weapons—very capable, but also very expensive. In a ‘war of frequencies’ scenario, however, these would be the most effective weapons to have. Later innovations and mass production may bring the price down and proliferate them among common users, but their first roles will likely be as occasional support or sniper’s weapons.


FURTHER INFORMATION

In Print:

Fire, Fusion, and Steel: The Traveller Technical Architecture

On The Web:

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

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

http://www.spacedaily.com/reports/How_Real_Is_The_Threat_Of_Laser_Weapons_999.html

http://www.realmilitarynetwork.com/~paul/department/hotspots/us-air-force-tests-laser-weapon-capabilities.html

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

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

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

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


Article added 3/8/10

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