The article on general laser firearms covered weapons that mostly worked in the infrared, visible light, and ultraviolet spectrums. Far more potentially devastating beams are possible, though, by using highly-charged ionic plasmas to create coherent beams of light instead of mere excited gas or electron flow. These weapons would generate coherent beams of tightly focused x-rays or even gamma rays to achieve potently high penetration factors and energy densities.
X-ray lasers were researched as weapons during the Reagan era's Strategic defense Initiative (SDI) program. In order to produce a powerful enough beam to knock out ICBMs, an x-ray laser weapon system would have to detonate a nuclear bomb. The vaporization of metal rods by the bomb would create a coherent beam of X-rays microseconds even as the weapon itself was destroyed by the bomb. Though the theory of it is still considered solid, the engineering prospects of creating such a weapon proved far more daunting than anticipated, and the project was abandoned.
Today, far humbler x-ray lasers are used in various laboratories throughout the world. Refinements in their use and techniques have pointed to how they may eventually be used more practically as a weapon system in the distant future. This article examines the possibility of x-ray lasers as infantry weapons. Other articles about tactical and strategic x-ray laser weapons will be discussed in other articles.
There are many different frequencies of X-rays, and there are only a few narrow range bands that would function well as weapons. Many others, including those used by medical x-ray machines, are fairly easy to scatter with physical barriers, especially dense metal. As with other types of laser weapons, choosing the right frequency is essential to the effective use of X-ray lasers in combat.
X-Ray lasers would be devastating weapons on a battlefield. If set at the right frequencies, they could deliver tremendous heat damage in a single shot, pulsing through meters worth of armor. Today, it would take a main battle tank to stand up to a soldier armed with a high-powered x-ray laser weapon.
An X-ray laser's main purpose would likely not be against vehicles, however. In the future, individual soldiers look likely to become more and more heavily armored, to the point that they may be sporting mecha-style suits such as those seen in Heinlein's novel Starship Troopers. In such a scenario, high-penetration x-ray lasers may be the ideal direct-fire anti-personnel firearm.
One of the main advantages of any laser weapon is its speed. Missiles can take out armored vehicles and powered-armored soldiers readily, but they still require time to reach their target. Even advanced high-speed missiles would require at least a few milliseconds to cross even a short distance. Not enough time for a human operator to respond, but more than a substantial margin for automated computer-controlled countermeasures to deploy.
X-ray lasers have no such limitation. Travelling at the speed of light, the beam strikes it target with no forewarning whatsoever.
At the heart of a portable x-ray Laser weapon would likely be a pulsed power generator, most likely in cartridge form for easy handling and disposal by the weapon mechanism. These cartridges would be arranged in magazine form and to the soldier the weapon would be loaded very similarly to modern firearms. This pulsed power cartridge would either have a self-contained high-ampere current source such as a high-efficient ultracapacitor, explosive power generator, or superconducting battery, or the cartridge would draw energy from an external source carried by the soldier in a backpack or belt pack.
The heart of any x-ray laser is a high-energy, highly ionized plasma. One way to achieve this is with ultra high current pulsing through the microfine wires in the cartridge, making the wires explode. Because the wires are crossed in certain advantageous configurations, the plasmas of the detonating wires are drawn to the currents of other exploding wires, causing an intense implosion that creates a very high-energy plasma. This plasmas is then used as the ionic source of the lased x-rays used in the weapon.
The weapon will also have to incorporate a means to evacuate the waste gasses generated by the plasma after each shot. An exhaust port will likely be located down along the length of the barrel, to keep the toxic and super-heated exhaust away from the operator, and angled down and away so the escaping gasses would not to interfere with successive shots of the beam.
The high-energy plasma as well as heat issues associated with the x-ray beam itself (the intense radiation passing through may tend to super-heat focusing elements that tighten and intensify the beam) will necessitate the need to incorporate an advanced temperature regulation system into the weapon. The venting of the plasma gas at the end of each firing cycle will help, as would cooling fans or sheaths on the weapon barrel. An active cooling system using refrigerants may also be necessary. In the later case, refrigerant gasses may be shot through the length of the weapon as its fired, keeping the temperature of the weapon within an optimal operational range, and are then expelled along with the plasma gasses. The refrigerants needed for each shot may be held in the weapon magazine itself, providing just enough cooling for each shot in the magazine.
The need to incorporate this cooling system, as well as the probable size of the pulsed power cartridges, will tend to make x-ray laser magazines larger and bulkier than those of modern firearms of like size. The weapon itself will also be well-shielded to protect the operator from any leaking radiation, adding to its weight.
An x-ray laser can operate near-silently and has no visible beam. However, its heating issue as well as the need to vent plasma-hot gasses will mean that it will likely make it practically glow in the infrared spectrum whenever it is fired.
The first X-ray Laser weapon systems will of course be deployed on vehicles first, and after experience with that technology progresses, the system may eventually be miniaturized until it can be used by an individual soldier. The premiere of an x-ray laser firearm on the battlefield will likely be as a squad's heavy fire-support weapon. The various system requirements (power, cooling, shielding, etc) will make the first prototype systems heavy and bulky, requiring the squad's heavy gunner to use a special harness (or given the tech level, maybe even an exoskeleton or powered armor) to carry the weapon.
It is assumed that with enough trial and error, many of the previous man-portable weapon system's bulk issues will be solved, allowing the weapon to be shrunk down so that it can be handled with precision by the average soldier. Most significantly is the development of the Fusor, or small compact fusion generator, thought to emerge around this Tech Level. This would allow an operator to carry as much power for the weapon as he would ever need in a small backpack or beltpack.
It is possible to tweak the beams in the previously mentioned weapon systems so they can be kicked up a notch frequency-wise, into the even higher energy realm of gamma rays. However, the super-heating of material focusing elements becomes even more of a major issue with such weapons, as ever more intense radiation is focused through them. A much more robust and efficient heat-dissipation and shielding system would be needed, adding to the weapon's bulk and expense.
It is possible that the cooling issues can be resolved, allowing these weapons what basically amounts to autofire--holding down the trigger and firing x-ray beams rapidly one after another, perhaps even several dozen a second. These would be devastating anti-personnel weapons, even to the heavily-armored soldiers of the far future, and could even take down heavily-protected targets such as vehicles by concentrating its many beam shots tightly in one spot.
The Mote in God's Eye By Larry Niven and Jerry Pournelle
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