Future technologies

SPACE WEAPONS HUB
ORBITAL BOMBARDMENT SYSTEMS

A concept rendering of the "Rods From God" orbital bombardment system. Image copyright Popular Science.
Fractional Orbital Bombardment SystemTech Level: 9
Orbital Missile PlatformTech Level: 9
Kinetic Orbital Bombardment ProjectilesTech Level: 13
This article covers weapon systems specifically designed for orbital bombardment. Intentional asteroid and meteoroid bombardment will be dealt with in another article, as will orbital bombardment by spaceships.
Orbital bombardment is just what the name implies--targeting and firing weapons at a planet's surface from orbit. Though not well advertised, it was the fear of the development of this technology which fueled the early years of the Cold War-era Space Race between the US and the USSR. If one side developed advanced spaceflight capabilities and the other didn't, that meant that one side could use orbital technology to target the other with impunity. Neither side was willing to be that vulnerable, and fanatically rushed ahead with rocket technology to make sure they didn't fall behind. It was with a sigh of relief when both sides signed and--suprisingly--adhered to the Outer Space Treaty of 1967, which forbade the placement of nuclear weapons in space. The SALT II treaty of 1979 placed further limitations on such technology by the major players in the Cold War, but does not prevent non-signatories of the agreement from developing such weapons in the future.
One of the major complications with orbital bombardment of a planet such as Earth is its relatively thick atmosphere. Air friction will tend to burn up or deflect incoming projectiles, and many beam weapons such as lasers and particle beams will scatter in the miles of thick atmosphere before it ever reaches the ground. Of course, bombarding worlds with no atmosphere, such as the Moon, will encounter no such difficulties.
One way to get through the atmosphere is to just power your way through it. A big enough projectile or powerful enough beam would be able to just slice through the atmosphere as if it wasn't there. However, for most weapon systems, this takes an enormous amount of energy, equivalent to many nuclear bombs' worth, so such tactics wouldn't be available until relatively high tech levels.
An alternative tactic would be to try for an upper-atmosphere detonation. If the weapon system can't penetrate all the way to the ground, you could instead focus the energy beam/projectiles on a point in the atmosphere you know the weapons can reach. Piling enough energy onto this one point all at once will result in an explosion and shockwave that in turn will slam into the ground.
An example of this, albeit from a natural source, can be found in the Tunguska Explosion of 1908. A comet fragment some 20 meters across was pulled into Earth's gravity well, plummeting toward the ground at over seven miles a second. At those speeds, the thick layers of the lower atmosphere acted pretty much as a physical wall. The comet fragment shattered, unleashing some 10 to 20 megatons of power from its pent-up kinetic energy some six miles above the ground. The resultant explosive shockwave was powerful enough to knock over 80 million trees over 830 square miles around the point of impact.
The remainder of this article mostly addresses weapon systems that can hit the ground directly. However, many space-based weapon systems not discussed here could conceivably attempt the upper-atmosphere detonation strategy.
There's also the issue of which orbit to place such weapons. A Low Earth Orbit will mean that it has a high orbital speed, and will zip over its potential ground target quickly, giving it a narrow firing window. Its low orbit will bring it back into position in as little as 15 to 20 minutes, but in an ongoing conflict that can be an eternity. Higher orbits can mean more time over a potential target and a longer firing window, but the weapon will also have to cover more distance between its position and the ground to reach its target. Geosynchronous orbit will allow a bombardment system to essential hover continuously over its target, keeping it always in sight, but in return any potential projectile will have to cover the 22,300 miles between it and the ground, which could take hours. Designers of orbital bombardment systems will have to take this potential trade-off (strike distance versus open target windows) into account when creating their weapons.
FRACTIONAL ORBITAL BOMBARDMENT SYSTEM
Tech Level: 9
Basically, this is an orbital missile. The weapon is shot into space and placed into low orbit just like any other satellite. The difference here was that this satellite is a nuclear warhead, and would de-orbit itself and plunge through the atmosphere at a planetside target when signaled to do so. Like with warheads of ICBMs, the weapon would be cone-shaped and hardened for fast re-entry, with a small liquid-fueled maneuver rocket and flight avionics attached to allow for a swift de-orbit burn to let it coast to its target. Its orbital capability put no limits on it range, and its orbital trajectory would give only a vague indication of its actual target.
The Soviets actually did develop a Fractional Orbital Bombardment System (FOBS) in the 1960s. It was called "fractional" because it needed not complete an entire orbit to work, only a fraction of one. In the wake of the aforementioned 1967 treaty, it was tested without a live warhead. FOBS became an official part of the Soviet arsenal for nearly two decades, though it was never deployed with an actual live weapon. The SALT II treaty of 1979 explicitly forbade any FOBS system from being deployed, and the Soviets quietly faded the weapon out in the early 1980s.
Still, this is a capability available to any nation or organization with access to nuclear technology and space, which now includes at least a dozen countries. It is one reason why ballistic missile technology is as closely monitored as nuclear capabilities by the international community.
One of the major drawbacks of the Soviet FOBS was it lacked precision targeting. It was good enough to hit somewhere in the vicinity of a city, but could not be maneuvered precisely enough to guarantee a kill on smaller, specific targets, such as early-warning radars or military installations. This was why it was deemed impractical for hitting hardened targets, and remained classified as a strategic as opposed to a tactical military asset.
Today, with far superior electronics and positioning systems available, this limitation can be easily overcome. A modern FOBS-like system could land a nuclear warhead anywhere on Earth, probably with a variance of a few hundred meters from its target at most.
Another disadvantage is its lack of stealth. When first conceived, FOBS would have allowed the Soviets to launch a surprise attack on the US, allowing the missiles to approach North America from the south, as opposed to going over the north pole, where much of the US's early-warning radar arrays were located. Today, however, with world-wide monitoring provided by satellites and a large array of ground-based radars monitoring objects in space, it would be near impossible to disguise the launch and trajectory of a FOBS warhead. Unlike submarines, which can remain undetected underwater even within a few miles of shore, tracking a FOBS warhead would be a simple enough matter from the ground.
However, it would be possible today to use modern stealth technology to help hide the warhead, provided one could find a way of employing it in orbit without being detected. FOBS warheads could also be disguised within a more normal satellite until the time came to strike.
ORBITAL MISSILE PLATFORM
Tech Level: 9
This is a larger satellite sporting numerous ground-targeted missiles. It is the orbital equivalent of a nuclear missile submarine; it would be capable of hitting a large number of surface targets from a single vehicle. It would allow devastating first strike and rapid counter-offensive capabilities within the span of a single orbit.
When the prospect of space stations was first being bandied about by both the US and the USSR in the 1960s, it was in part their potential use as orbital missile platforms that justified their further development. Unlike a FOBS, a manned orbital missile platform such as a space station could be manually targeted and would have had a somewhat better chance to hit a hardened target than the automated systems of the time.
Unlike a FOBS warhead, a larger integrated missile platform would be much harder to hide. If constructed today, it can of course be fully automated and have near-pinpoint satellite-guided accuracy. But unlike a FOBS, it would be more difficult to disguise and stealth, because of its larger size.
KINETIC ORBITAL BOMBARDMENT PROJECTILES
Tech Level: 13
This system has been informally called the "Rods From God." The idea originated in the 1950s from the RAND corporation, who suggested putting clusters of iron rods on ICBMs to act as kinetic energy weapons to use against conventional targets. Science fiction writer Jerry Pournelle expanded the idea into its current orbital satellite version. The US Military has researched the concept and several papers and reports on it still appear from time to time.
The current incarnation of the idea involves a dual satellite system, where two or more satellites are deployed in very close proximity to each other. One satellite would contain the sensors and targeting equipment, while the other would contain the actual bombardment projectiles and de-orbit launch system. The advantage of using this system is two-fold; the vibrations of the launch of the projectiles won't skew the precision targeting necessary to make the system practical, and keeping the projectile magazine separate would allow the system to be easily "reloaded" without having to replace the entire system. In fact, a single targeting satellite might support a number of nearby projectile-magazine satellites.
The actual projectiles themselves are dense tungsten alloy rods a foot in diameter and up to twenty feet long, similar to the dimensions of a telephone pole. The rods are re-inforced and tapered to allow fast re-entry, with stabilizing fins to keep it on target. The projectiles would be ejected from the launcher and plunge to the ground at over 36,000 feet per second, the sheer force exerted by its orbital deadfall making explosive warheads superfluous. The projectiles would also have a very high penetration factor, allowing them to be used to take out targets even buried deep underground.
The main barrier to developing this system is not so much technical as it is economic. It currently costs $10,000 to lift a pound of payload into orbit. The 'Rods from God' system would weigh dozens of tons, especially the projectile-carrying satellites, and the system would have to be deployed in large numbers to be effective. Many analysts simply believe it isn't worth the cost compared to many other, cheaper alternatives that can give comparable results. Only when launch costs become significantly cheaper would this weapon system become practical.
Aside from costs, there are a few technical issues that still need to be grappled with. The first is precision targeting. A variance of a few hundred meters is not a big deal for a nuclear weapon bombardment system such as FOBS. However, kinetic deadfall weapons such as the rods need to hit their target precisely dead-on in order to be optimally effective, a capability that's still very iffy at orbital speeds from 200+ miles up. In order to overcome this limitation, the rods would most likely need to be used in clusters instead of as individual projectiles. This is why they would need to be deployed in orbit in large numbers, and this in turn is why the system is likely to remain prohibitively expensive until launch costs come down by a large margin.
Others have expressed doubt that the rods could really be used for deep-penetration targeting. They may be travelling so fast that they would completely vaporize on impact with the ground, doing a great deal of surface damage but leaving buried targets shaken but intact. If this is indeed the case, the rods can be re-engineered to overcome this (perhaps by having a frangible outer layer that would absorb the majority of the impact energy, while a denser inner core retains enough of the momentum of the fall to continue the plunge deep into the surface), but this would only drive the cost of the already expensive weapon system up more.

ASTEROID BOMBARDMENT

A bad day for Earth as an asteroid impacts its surface. Image courtesy NASA.
Redirected Asteroid ImpactorTech Level: 9
Asteroid SwarmTech Level: 12
Tactical Meteoroid ImpactorTech Level: 13
During the Cold War, it was generally accepted the superpowers’ nuclear arsenals were the ultimate weapons available at the time. However, thanks to their space programs, it would have been possible for either side to escalate the level of destruction available by at least an order of magnitude. Given the aggression and paranoia both superpowers exhibited at times, it was probably fortunate that this option was never taken seriously, or if it was, it was never enacted upon.
The option in question is deliberate asteroid bombardment. Though it has only sporadically been studied in the real world as a means of warfare, variations of it has been seen in numerous science fiction sources. Links to articles detailing the exact effects of asteroid and comet impacts are at the bottom of this article.
REDIRECTED ASTEROID IMPACTOR
Tech Level: 9
In the related article Redirecting Asteroids (link at the end of this article), a number of methods was discussed for nudging both asteroids and comets onto new trajectories, either to avoid a catastrophic impact with Earth or to push such bodies into more advantageous orbits for economic exploitation.
However, if one wanted to, one could use the same techniques to hurtle one of these flying mountains deliberately into Earth’s path. If done with precision, such a massive impactor could be made to hit any specific spot on the planet, including an enemy stronghold. This is actually a capability that has been available since at least the late 1960s, but no one has yet taken advantage of it.
For most of the Cold War era, the scientific community was largely unaware of the role played by such collisions in the history of Earth, and of how truly devastating an asteroid impact could be on a large scale. More importantly, they only had rudimentary theories on the composition and nature of this cosmic debris. Even though they could reach nearby asteroids with spacecraft and effect a change in course via nuclear impulse weapons, it would have also taken months using the computational methods at the time to work out a new trajectory for any impactor, and pinpoint accuracy was by no means guaranteed.
Today, any power that can boast interplanetary spaceflight capability can use asteroid impactors as weapons. Besides the US and Russia, today this includes the member nations of the ESA, and in the near future will likely include China, India, and Japan as well.
A potential asteroid weapon would have to be carefully chosen, and its trajectory laid out with equal attention to detail. Ideally, a candidate impactor should be just large enough to cause tremendous local damage, but not so massive as to create global environmental havoc and risk the redirecting nation’s existence.
Composition of the impactor will be a factor to consider. Asteroids composed mostly of nickel-iron are ideal, as they are the objects mostly likely to make it through the atmosphere intact. Carbonaceous asteroids and comets are thought likely to break up high in the atmosphere, their relatively fragile structures shattering as they hit the thicker layers of the lower atmosphere at the tremendous velocities orbital deadfalls generate. This is not necessarily a detriment to their use, as the Tunguska Explosion of 1908 showed. That impact of a small comet or asteroid shattered six miles above the ground, unleashing some 20 megatons of explosive force that felled trees for nearly a thousand square kilometers around the point of impact.
The exact size of the asteroid chosen would probably depend on the desired level of destruction and the estimated speed with which it would impact. The higher the velocity, the less mass needed to cause a target goal of collateral damage. Smaller asteroids would cause the same amount of destruction as nuclear weapons, but would not have the accompanying radiation and radioactive fallout, making them ideal for taking out enemy strongpoints and cities in a region that an aggressor may plan on capturing at a later point.
Asteroids capable of delivering Hiroshima-like blasts would usually measure between 10 and 50 meters across, depending on its final impact speed. Impactors measuring 100 meters or more across are capable of delivering multi-megaton level damage. Asteroids larger than one kilometer across would unleash catastrophic environmental damage across an entire continent and plunge the world into a nuclear winter with gigaton or even teraton-level power. With impactors much larger than this an aggressor risks triggering a guaranteed mass extinction event.
Availability of weaponizable rocks becomes another factor in this kind of warfare. Even though there are some one million or so usable asteroids (neither too small so that they would burn up completely in the atmosphere, nor too large as to trigger major global damage) near Earth's orbit, finding the ones that are of the right composition, in the proper position, and on a trajectory that can be altered favorably is another matter. Comprehensive full-sky surveys would be needed to find which ones can be put to optimal use.
One tactic that can be deployed here is not diverting the asteroids from their original orbits directly to their targets. Instead, a small population of them can be diverted into "holding" points closer to Earth until they are needed. Potential stable holding points for impactors include the Earth-Moon L4 and L5 LaGrange points, Lunar orbit, or even the Earth-Sun L4 and L5 LaGrange points. In fact, putting the clusters of impactors near Earth where they can clearly be seen in the sky with the naked eye would tend to have a tremendous psychological impact on a potential rival.
This is also not an option for the impatient. Even the nearest asteroids would take weeks or months to properly divert. Acquiring ammunition from even farther out in the solar system may take years to accomplish.
Of course, the entire purpose of such an attack may indeed be total global devastation after all, in which case larger and more massive impactors will be used. Such a capability may be used by one faction or another as a potential doomsday option, a threat to frighten rivals into submission. A demonstration on another celestial body, such as the moon or a nearby planet, may be arranged to prove that they have such a capability.
In the future, as human civilization becomes an interplanetary and perhaps even an interstellar entity, bombardment by doomsday rocks may be used deliberately to remove entire worlds from the strategic equation.
However, asteroids as weapons have two serious drawbacks that have so far prevented them from being considered seriously as potential weapons: cost and targeting accuracy.
At current launch and spaceflight costs, sending a mission to divert a nearby asteroids would cost at least hundreds of millions of dollars and would require constant monitoring of a year or more. Nuclear ICBMs, which do a comparable level of damage and can be deployed much quicker, are a bargain in comparison.
This may not always be the case, however. As major infrastructures are built up in orbit and beyond in the decades to come, access to space rocks may become much more common and economical. Their potential use as weapons will likely increase as well in these circumstances.
The other major obstacles is pinpoint targeting. Asteroids usable as weapons often mass millions of tons, and that's on the low end of their size scale. On top of this, they are usually very irregularly shaped and can have wildly varying density throughout. As one can imagine, these are very difficult objects to wrestle about with precision. The variations in shape and densities can throw off course corrections very easily. Also, unforeseen fault lines within the rock could cause portions of it to fracture or break away during or after a course alteration, or even release outgassing that can change its trajectory.
All this adds up to a projectile that is by no means guaranteed to hit the target you aim it for, especially with the techniques available at lower tech levels. One would need a redirecting spacecraft to stay with the impactor for most of its journey to make the necessary nudges as needed, right up to the point where its entering the atmosphere, to ensure a direct hit. Asteroid-anchored rockets and dedicated asteroid tug spacecraft are ideal, perhaps coupled with other redirecting techniques.
Asteroid-sized artificial masses can also be used similarly. In the long-running anime science fiction series Gundam, renegade colonies in orbit unleashed their ultimate weapon against the nations of Earth: dropping an asteroid-sized O'Neill Colony on the planet with apocalyptic results.
ASTEROID SWARM
Tech Level: 12
Instead of hitting a planet with one asteroid, you hit it with multiple large impactors all at once. This can be accomplished in two ways: actually gathering many asteroids in one place and then set them hurtling together toward the target world, or by detonating a single large asteroid so its many fragments will impact the world in a short amount of time. While Cold War Era technology is up to the task of redirecting single asteroids, herding them accurately in large numbers or knowing enough about their structure to fracture one with precision is the task of more advanced periods.
While the results of single catastrophic impact are fairly well known at this point in time, no one is really sure of the exact effects of large numbers of impactors hitting a world like Earth all at once. Imagine several hundred or even several thousand Tunguska-like events striking all over the globe within a period of several hours. Besides the expected global dustclouds and land devastation and tsunamis, hundreds of large impact events could super-heat the atmosphere over large swaths of territory, perhaps sparking off a world-wide firestorm.
Asteroid swarms are definitive doomsday weapons for inhabited worlds. It is hard to imagine any nation or organization today would attempt such an attack. However, in the future when interplanetary or interstellar societies become possible, asteroid swarm bombardment may become a viable tactic.
Though arranging the impactors to strike within minutes of each other is theoretically doable, given the scale of such a bombardment, it will likely have to be carried out over a period of several hours or days or weeks, as the mountain-sized rocks are slowly maneuvered about over distances of many thousands (or even millions) of kilometers.
Asteroid swarm bombardments can be seen in two very different on-screen science fiction properties:This Island Earth and Space Battleship Yamato, both of which depict one civilization trying to grind another under its heel by bombarding their rivals' homeworlds with swarms of asteroids. In the real world, a very dramatic example of a multiple asteroid bombardment was seen in 1994, when fragments of comet Shoemaker-Levy 9 crashed spectacularly one after another into the atmosphere of Jupiter.
TACTICAL METEOROID IMPACTOR
Tech Level: 13
A tactic that requires significant more tactical and technological finesse is using space debris such as meteoroids to attack smaller targets without causing any kind of major environmental damage. Their effect on the battlefield would be the equivalent of artillery shells launched from orbit. Since acquiring, launching, and aiming enough small impactors to make this scheme practical is a much harder task than just redirecting a single large impactor, this weapon system's tech level is that much higher.
The size of these impactors would be significantly smaller than those previously discussed, perhaps several to a dozen meters across at most. Nickel-iron asteroids or similar heavy metal compositions which could endure fiery re-entry all the way to the ground would be a must; the atmospheric detonation strategy simply would not work with projectiles this small.
Even with highly advanced technology, it would be quite impractical to hunt down appropriately-sized projectiles from all over the solar system. It would be much easier just to mine the rocks from a larger source. This way, not only would an aggressor have a very large supply of potential ammunition, but the impactors could even shaped and sized to specification.
Two ways have been proposed for providing meteoroid impactors in quantity: one is with a large asteroid redirected into orbit about Earth, and the other is from a base on the Moon. In both instances, mining of the impactors will likely be carried out by automated machines and shot into holding orbits with electromagnetic launchers. There, a launcher spacecraft or satellite will rendezvous with and gather the meteoroids for use in the actual bombardment. These in turn will also likely be electromagnetic launchers. Alternately, many small, cheap, expendable flight packages--composed of a small rocket to break orbit, radio transceiver, and flight avionics--will mate with individual rocks and await a signal to launch them at a target.
Problems with precision targeting will persist as with the larger asteroids, complicated even more now by the effects of atmospheric entry on these smaller projectiles. Since meteoroids would not be ideal for very deep penetration attacks, such tasks would likely be left to other weapon systems while this bombardment system concentrates on surface damage. Because of targeting issues, these are most effective when employed in swarms of half a dozen or more.
Meteoroid bombardment is most effective against non-mobile installations such as airbases and radar installations, but can be used to target slow-moving vehicles or vehicles moving in a predictable pattern, such as tank columns, naval surface ships, and trains.
For an example of tactical meteoroid bombardment warfare used in science fiction, refer to the novel Footfall by Larry Niven and Jerry Pournelle.

MESON GUNS
Deep Bunker Meson Gun EmplacementsTech Level: 18
Spinal Mount Meson GunsTech Level: 19
Bay-Mounted Meson GunsTech Level: 20
Meson Gun Tactical WeaponsTech Level: 22
A specialized type of particle beam weapon first postulated in the Traveller RPG universe is the meson gun. Pi neutral mesons (created by the collision of an electron and a positron) are subatomic particles that pass through normal matter with very little interaction, similarly to neutrinos. However, the also have a very short life span, decaying with a burst of gamma rays, which reacts much more substantially with material substances. A meson gun accelerates pi neutral meson particles to near-lightspeed, where time dilation slows their rate of decay. If done with precision, the mesons can be timed to decay at a predetermined spot, and if packed densely enough in the beam they can unleash a tremendous amount of energy, approaching the level of nuclear bombs.
Mesons guns are a technology that requires a very advanced degree of sophistication in all its elements, as the weapon has to accelerate the pi neutral mesons to within the right tiny window of near-lightspeed to delay their decay until they are passing through or near the desired target. They do have a very unique property of being able to be fired through physical objects without harming or even interacting with them in any way. They can bypass defenses such as sandcasters clouds, magnetic fields, and physical armor easily. In fact, a ship equipped with a sufficiently powerful meson gun could theoretically fire completely through a planet to hit a target on the other side.
The great hurdle in producing this technology is the precise three-dimensional targetting needed in order to make a hit. Meson guns would work best against slow moving targets or against targets with predictable paths, such as installations on a planet or an orbitting space station.
Hitting a rapidly moving target such as a spaceship would be considerably more difficult. In order to assure a hit, the distance between target and gun should be as narrow as possible. In space combat, even if its packing a nuclear-bomb-level punch, a meson gun would probably work best if the target is within a light-second at most so the target's predicted paths of movement cannot vary too much for the weapon to get a lock on it.
DEEP BUNKER MESON GUN EMPLACEMENT
Tech Level: 18
Like most new weapon systems, the first meson guns are likely to be large and bulky and require tremendous amounts of energy. Their first practical use may be in deep-underground bunkers, where they can have ready access to large, immobile powergrids and the bulky machinery that would be needed to make them work. Since the beam of the weapon can pass through any arbitrary layers of matter, meson gun emplacements can be placed many kilometers underground without affecting weapon performance.
In the Traveller RPG universe where meson guns hail from, deep meson gun emplacements were considered one of the toughest planetary defenses to defeat by attacking forces. Not only were they supremely well protected under miles and miles of rock, but even determining their exact location could be probematic as meson beams leave no tell tale sign of their origin point.
A deep meson gun emplacement could also target locations on the planet's surface as well as anything in nearby space.
SPINAL MOUNT MESON GUN
Tech Level: 19
A spinal mount is a weapon system that runs the length of an entire spaceship. Often, the ship is literally built around the weapon system. The most famous example of such a weapon can be found in the title vessel of Space Battleship Yamato (called Starblazers in the US) and its 'Wave Motion' Gun.
A spinal-mount meson gun ship would require the best sensors its tech level could provide to better facilitate the three-dimensional targeting that would be needed. It would of course not need any kind of open arperture for its weapon, as the meson gun can easily pass through its hull when fired.
Even though the ship would have to be aimed in the general direction of the target, it probably would not need to be lined up precisely. The barrel of the particle accelerator will likely be built to allow some variance in the angle of the beam, maybe up to as much as ten or fifteen degrees or so.
BAY-MOUNTED MESON GUN
Tech Level: 20
As meson guns miniaturize, they will eventually be able to be fitted into small bays within a spaceship. These would basically be internal turrets of a sort, completely englobed to allow easy 360-degree targetting. If desired, meson guns could be placed externally onto barebettes and turrets and such, but it would make more sense to keep the weapons within the hull where they would be better protected.
TACTICAL MESON GUNS
Tech Level: 22
Its possible, that with ever-increasing sophistication in power generation, miniaturization, sensors, and computer power, that meson guns could become small and convenient enough to use on a battlefield. They would of course be far less potent than their larger ship-mounted cousins, but their ability to ignore any type of physical armor would make them very desirable in any type of conflict.
A tactical-level meson gun, whether mounted on a vehicle or carried by an individual soldier, would need a very sophisticated active sensor array and computer core in order to pinpoint precisiely in three-dimensions what the operator is aiming at and adjust the velocity of the mesons in the beam accordingly. The operator would also be able to program the weapon quickly to fire through barriers at a target beyond, perhaps through a neural link.

PLASMA ACOUSTIC SHIELD SYSTEM

A plasmoid, a primary feature of the plasma acoustic shield system, trapped in a laboratory bottle and seen through a heavy visual filter. Image from JLN Labs.
Plasma Acoustic Shield SystemTech Level: 12
This technology is more commonly called a plasma shield. However, its more formal name is used here in order to distinguish it from the cold plasma shields currently being developed to protect spacecraft.
The Plasma Acoustic Shield System (PASS) is a defense system being researched by the company Stellar Photonics at the US Army's Advanced Energy Armaments Systems Division at Picatinny Arsenal in New Jersey. Its operation is based on the technique of dynamic pulse detonation. A laser focused on a specific spot in the air will superheat the gasses there instantly, creating a super-hot ball of plasma called a plasmoid. A second laser focused on the same spot creates a supersonic shockwave within the plasmoid, resulting in an explosion accompanied by a bright flash of light and a loud, often disorienting bang. Focused microwaves are thought to also be able to produce this kind of effect.
The current system has a maximum range of about one hundred meters. Because of power issues, many think that PASS is unlikely to be used as an offensive weapon anytime in the near future. The lasers, by themselves, would have trouble burning through a sheet of paper.
As a potential defense against incoming projectiles, PASS may be surprisingly effective. Unlike other laser weapon systems being developed, such as the Airborne Laser, PASS does not rely on directly hitting a target and burning through a missile’s casing. Rather, rapid firing of the system in a relatively short area just ahead of the speeding projectile could produce dozens or even hundreds of small, potent shockwaves within a fraction of a second that would cause the missile to tumble and perhaps even throw it off-target.
While this would not necessarily prevent the missile from detonating or even hitting the target, causing the projectile to tumble could still prevent a great deal of armor penetration, as most anti-armor warheads depend on precise alignment with the target to work properly. While currently being developed as a vehicle defense, when PASS technology properly matures (and the mobile power available to it becomes sufficiently potent,) it can stripped down to protect individual soldiers from bullets, or scaled up to target ballistic missiles and aircraft kilometers away.
In order to be effective, PASS needs to be coupled with an advanced and highly efficient targeting system that can recognize and respond to incoming threats in time to intercept them, which would be an impressive engineering accomplishment on its own. However, given the time scales involved—usually milliseconds or less—this would mean the human operator would be completely out of the operational loop; the system would be fully automated, for better or ill.
The technology is also being considered for use as a small-scale alternative flash-bang grenades, as each individual plasmoid shockwave is about as loud and bright as a firecracker. Several hundred going off all at once near an enemy combatant could have a disorienting stun effect. The plasmoid detonations can also be precisely aligned, forming a ‘wall’ or other simple shape in the air to function as active deterrents.

ELECTROMAGNETIC DEFENSE FIELD

The USS Enterprise from the Star Trek universe utilizes electromagnetic 'deflector' shields to protect itself from space-borne hazards.
Electromagnetic Defense FieldsTech Level: 12
Two related concepts, the Electrostatic Defense Field and the Plasma Shield, will be discussed in their own articles. Though mentioned many times in passing in science fiction (often called "deflector shields",) a serious discussion of magnetic fields as a physical defense could not be found. Some of what follows is an extrapolation on current research.
The idea of electromagnetic fields as a defensive barrier originates from the golden age of science fiction, when mad scientists and aliens in pulp magazines used fantastic-seeming "fields of force" to create a barrier against attack. In nature, Earth’s magnetic field helps to shield us from both solar and cosmic radiation. In high-energy physics, powerful magnetic fields contain and shape super-hot plasmas and particles travelling at near-light speed.
NASA is also currently looking into integrating active electromagnetic fields into spacecraft hulls to shield them from radiation hazards. Because solar wind particles and cosmic radiation tend to be charged, deflection via active electromagnetic fields are thought to be an effective way to protect a crew during a long-duration space flight outside of Earth’s protective magnetic blanket.
Using such fields as barriers against attack are another matter, however. A defensive magnetic field in principle is fairly easy to generate; all one needs is high grade conductive coils in abundance and a power source. Higher tech levels may use superconducting materials instead, to generate more powerful fields using less energy and less material.
The more powerful you want the field, you either add more wires coils or more current, within limits. Too much current, and the electrical resistance in the wire will generate too much heat, degrading the field or perhaps even melting the conductor. Superconducting systems can handle much more current than normal conducting wires, but even they have limits.
These fields work best against metallic objects, but fields of sufficiently immense strength would be able to deflect almost any kind of normal matter. How far an object can penetrate the field will depend greatly how much mass and inertia is backing it up. Projectiles with sufficient velocity may be able to penetrate magnetic fields no matter how powerful such defenses can be.
This technology is usually associated with spacecraft and space stations, mainly because of its previously mentioned potential use in protecting such assets from radiation. It can be used in an atmosphere, but at diminished efficiency; the constant ionization of air molecules will sap away some of the energy of the field.
The principle for using magnetic fields for deflecting attacks is straightforward. Upon encountering field, an incoming projectile will become ionized (if its not already) as electrons on its outermost layers are repelled away by the field. Upon encountering the inner, stronger portions of the field, the now-charged object is pushed away, hopefully curving the trajectory of the incoming projectile away from the ship. Low-powered lasers directed at incoming threats could also help to ionize targets, increasing the potential effectiveness of the field.
Besides physical threats, such fields can also potentially deflect charged particle beams and plasma weapons. They would only have a negligible effect on lasers and neutral particle beams, however, no matter their strength.
One of the big drawbacks to using these fields defensively is their potentially enormous energy drain. Deflecting radiation such as in current NASA proposals does not require great field strength, but larger, speedier threats like micrometeoroids (which at orbital speeds can hit like bullets), missiles, shrapnel, particle beams, and so on require a magnetic field many thousands of times more potent than the one Earth generates naturally. Creating such a field around, say, a tank or a space station would require a constant drain on even potent energy resources.
Another big drawback is the effect the field will have on both operating personnel and nearby electronics. Powerful electromagnetic fields are known to have an effect on long-term health, leading to medical complications later in life. Fields of the strength discussed here could also cause immediate injury (including headaches, nausea, and loss of consciousness) or even outright death.
Electronics will suffer short-circuits, and glitches as their circuits pick up stray charges from the field. In both cases, heavy shielding of the crew and operating equipment may be necessary, adding to design complications and cost. Unfortunately, projectiles fired against the target can also be similarly shielded, nullifying the shield’s effectiveness.
Such defense fields may also play havoc with communications, but this can be at least partially bypassed by extending a shielded radio mast or antenna out past the field.
Other vulnerabilities exist. For ground-based vehicles especially, the presence of incidental conductive material in the field (spent shrapnel, casings, debris, etc) can help sap a field’s strength. A wily enemy could pepper a battlefield with such material with the express purpose of degrading any protective magnetic fields present.
Finally, there is the consideration that in combat, an active electromagnetic defense field would show up like a bright star on enemy sensors, pretty much drawing a large metaphoric bullseye around the target vehicle.

PLASMA SHIELDS

Plasma shields may protect future spacecraft from space-borne radiation and other hazards. Image artist unknown.
Plasma ShieldsTech Level: 14
Two related concepts, the Electromagnetic Defense Field and the Electrostatic Defense Field, will be discussed in their own articles. Magnetic Sails, a form of deep space propulsion, also uses similar technology. Plasma shields may turn out to be the closest 'realistic' technology can come to mimicking the nigh-magical force fields of science fiction.
Plasma shields postulate using cold plasmas in conjunction with powerful electromagnetic fields to protect spaceships from hazards. This type of shield is thought to be most useful against space-born radiation, but they could also offer decent protection against micrometeoroids, shrapnel, beam weapons, and other types of physical damage if made sufficiently potent.
Cold plasmas are just what they sound like. Normal plasmas, such as those used in fusion and rocket research, can usually only be produced at very high temperatures. Cold plasmas are produced at room temperature or lower, making them ideal for a number of practical applications. Ionized hydrogen is usually cited for space applications, as a strong electrical current can easily strip the element into raw nuclei and electrons.
Cold plasmas are much easier to generate in a vacuum environment such as space, so its likely their first large-scale applications will be found there in the form of a protective shield for spacecraft.

A laboratory magnetic field holding cold plasma.

The ship generates an electromagnetic field about itself, much as in the case of electromagnetic defense shields. In this case, however, cold plasmas are ejected around the ship and held in place by the magnetic fields. As the plasma is itself electrically charged, it adds to the field's strength, allowing it to obtain much greater resilience at lower power levels than magnetic fields alone.
The powerful magnetic field will turn away the charged particle that make up space-borne radiation hazards such as the solar wind. Physical objects such as micrometeoroids or shrapnel will become ionized on encountering the outer edges of the field and can be deflected by the like-charged but much stronger inner portions of the field, assuming the field is made strong enough to overcome their kinetic energy. The ionized plasma particles of the field will greatly aid this effect, by knocking off surface electrons via impacts on incoming objects and by setting up swirling electrical eddies throughout the field.
The denser the plasma in the field, the better the field will be at deflection. Dense plasma shields also offer protection against beam weapons such as lasers by creating an obscuring cloud that can dissipate the beam's energy. The plasma cloud can also help stymie the neutral particle beams used in space combat.
In order to generate the field, meshes or loops of superconductors would have to be affixed to the outer hull of a spacecraft. There are two modes of thought on the actual design: one, an 'open' shield design, would rely on the magnetic fields generated directly from the hull. These would work similarly to the Van Allen radiation belts that naturally trap ionized particles in Earth's magnetic field. The second option, a 'closed' shield, would use the electromagnetic field of a wire mesh suspended some distance from the spacecraft.
Both options have their advantages and disadvantages. An open shield design would be slowly but constantly bleeding away plasma just from normal entropy, and any hit on the shield would deplete it that much more. Thus, open plasma shields would require constant replenishing of the plasma, which would require a greater supply of fuel, which in turn can add to the weight, bulk, and expense of the spacecraft. However, open shields can be deployed and dissipated rather quickly.
A closed shield would prevent most plasma loss by literally forming an enclosed magnetic bottle around the vessel, and allow the ship to carry much less fuel for the shield. However, the shield would take more time and effort to deploy and take down each time than an open version, and would be much more vulnerable to physical damage. Closed shields would also tend to be more complicated in their construction and use.
Thus, closed shields will probably be used in situations where spaceship mass and fuel needs to be conserved, such as on near-term interplanetary missions. Open shields, because they are relatively simpler and can be deployed faster, will more likely be used farther in the future on ships designed for combat.
It should be noted that even though cold plasmas are used to initiate these shields, there is no guarantee that the plasma will remain cold for long. If used as a radiation shield, it will pick up heat from the rays its absorbing and deflecting. If used as a weapons shield, this problem becomes even more exacerbated. In fact, if hit by a sufficiently powerful beam weapon or explosion, the shield may be successful in deflecting the attack, but it may heat up so much that it could bake the crew inside.
Certain types of propulsion, such as plasma rockets and ion drives, generate plasma exhausts. Its certainly possible that some of this exhaust could be diverted into the shields to give the spaceship an alternate source of fuel for the shields.
Additional problems may arise with communications and sensors while the plasma shield is in operation, but this can be circumvented by telescoping an antenna past the field or towing a sensor/communication package behind the main spacecraft.
Plasma shields can be employed by vehicles and bases within an atmosphere, but at reduced efficiency. The magnetic field would be constantly losing more energy than it would in a vacuum from ionizing the air molecules around it. The interaction with the atmospheric gasses would bleed away the plasma more quickly and could even lead to lightning-like electrical discharges, making them hazardous to be around for friend and foe alike.

FORCE FIELDS

From the TV series Stargate: Atlantis, the title city uses an enormous force field to protect itself from a tsunami. Image copyright MGM.
Absorptive Force FieldsTech Level: 17
Deflective Force FieldsTech Level: 17
Structural Support Force FieldsTech level: 18
Specialty Force FieldsTech Level: 19
Force fields are one of the most commonplace speculative technologies in modern science fiction, seen on screen in properties like Star Trek, Star Wars, Independence Day, War of the Worlds,Stargate, in novels such as The Mote In God’s Eye by Larry Niven and Jeremy Pournelle and Startide Rising by David Brin, and in video games like Starcraft and Homeworld. However, they are also one of the more unlikely innovations that may emerge from real-world science, at least in the form as they’re usually depicted on screen and elsewhere.
A ‘field of force’ is a term used in real world science to describe how particles act near electromagnetically charged objects. Early writers in the science fiction field, as well as many scriptwriters and directors since, apparently misunderstood these fields of particle influence to be actual physical barriers made up of some conveniently obscure type of energy. This interpretation has become so commonplace that it has supplanted the original definition of the term in popular use.
In most sources, the explanation of how force fields function is usually hand-waved away as being "energy barriers." However, there is the serious question of how energy that acts as a solid wall could work, or would even be possible. There are real-world technologies currently being researched (Electromagnetic Defense Fields and Plasma Shields; links at the end of the article) that share some characteristics of fictional force fields, but come no where near the science fiction staple’s apparent versatility, potency, or ease of use. Powerful and currently unguessed-at ways of manipulating subatomic particles would have to be developed in order to make these technologies comply with the visions seen in science fiction.
For all intents and purposes, science fiction force fields are similar to FTL drives and time travel--they can only exist if the workings of the universe turn out a certain specific way. Because of this, their position on the Tech Level scale is relatively arbitrary. Their starting point (the theoretical breakthroughs that could lead to their development) is placed at Level 16 in order to coincide with their use in space opera civilizations, where they are most frequently seen. Truthfully, though, for all we know the scientific understanding needed to create them could come tomorrow as easily as thousands of years from now, if they’re even possible at all.
FORCE FIELD PARTICLES
Because Force Fields are in large part pure speculation with only a tenuous connection to real-life science, they come in a wild variety of fictional characteristics and effects, dependant much more on the imaginations of writers and special effects engineers than any real physical restraints. However, because certain motifs carry over among many of the scifi books, movies, and TV series, we can infer some things about their operation in general. By employing energy, we know the force fields are made up of particles of some kind, which are somehow held or cycled in place by some unknown means of quantum manipulation. But which particles?
Electron Force Fields: Some sources have particle barriers that seem to carry an electrical charge. This is a popular motif in the force fields used in scifi’s jail cell doors; a character will invariable touch the field, and get a shock which causes him to quickly pull his hand away. This would seem to indicate that electrons might be a good candidate particle. In fact, at least one source, the Traveller RPG, describes their force fields (known in the source material as black globes) as dedicated electron screens. Real-life experiments in using electromagnetic fields and cold plasmas as protective barriers are ongoing; the far-future force fields we see on screen might just be a highly advanced versions of these technologies, augmented by quantum technology we can’t yet guess at.
Photonic Force Fields: A few older mentions of force fields in the Star Wars universe quoted them of being made of photons; the holo-decks of Star Trek fame also seem to create their force-field ‘holograms’ at least partially out of heavily-manipulated photons. There are a number of techniques for manipulating and even slowing down a beam of light; the idea of a free-standing three-dimensional hologram goes back to this idea that large populations of photons can be tamed and sculpted at will. A force field in these sources could in essence be nodes of overlapping and intersecting photons, herded by immensely sophisticated quantum manipulators. How even heavily-concentrated photons could act as a wall-like physical barrier remains unknown.
Graviton Force Fields: The defensive force fields in Star Trek may be created through the manipulation of gravity ("coherent graviton emissions" one character was quoted as saying in one episode when explaining the workings of force fields.) Because gravitons can theoretically bend the fabric of space itself, force fields of this type might be minor discontinuities in space/time. One way to visualize this would be to think of space as water on the surface of a pond, with the force field as a permanent ripple around the ship that holds at a steady distance. The more powerful the force field, the deeper and wider the ripple, and the more effective it would be at deflecting the trajectories of incoming attacks on the pond surface.
This would be keeping with Star Trek’s technological motif of creating warp bubbles and working subspace, both of which also require manipulating space/time as a whole with a high degree of sophistication.
PROPERTIES OF FORCE FIELDS
No matter their actual particle make-up, science fiction force fields have some basic characteristics in common.
Units: The device that actually creates the barrier is called either a force field generator, projector, or emitter. It usually (but not always) needs to be free of obstructions between it and where the force field is to be created. Multiple projectors can also apparently be networked together to merge and/or overlap the fields they create, allowing them to protect an object that might be too large for a single generator, such as a spaceship.
Energy Consumption: Force fields require a steady supply of power, usually at what would be considered very high levels for us in the twenty-first century. Unlike a physical barrier that a force field imitates, it must be continually bleeding away particles from its surface and losing energy, which needs to be constantly replenished.
Instant Activation, Deactivation: A force field usually pops into existence within milliseconds of activation. If the power is cut off, the force field almost instantly dissipates. There are some exceptions to this, such as in Stargate: Atlantis, where the city-englobing force field can take up to a minute to erect. Also, in Independence Day, the alien force fields flickered for a few seconds before finally disappearing. But for the most part, force fields are seen as instant-access devices.
Particle Frequency: According to superstring theory, all particles, matter and energy both, have quantum vibrational frequencies. If an accurate physical model, that would mean that all force fields would feature the quantum wavelength and frequency of their component particles. Star Trekin its later incarnations got a lot of tech babble mileage out of this, as battles between ships often became duels of which ship’s weapons frequencies could match their opponent’s shield attenuation first.
Cycle Frequency: In some scifi universes, force fields "cycle," or rotate their component particles through their volume, at very high rates. Even though the fields seem to be static glowing walls, in these sources they are more akin to rapidly flowing rivers of energy particles, constantly looping back on themselves. The force fields used by the Gua’uld in the Stargate universe have been established to have this feature.
Non-Interaction With Matter: Most force fields in scifi, when formed, will be stopped by a physical barrier. It may conform around the barrier, but it won't slice into it or permeate it. For example, if a force field is projected into a ship’s corridor, it will conform to the dimensions of the hallway, but won’t penetrate its walls. Why they would do this is unknown; most force fields wield so much energy that they should be able to easily slice through most matter.
Regeneration Time: If a force field is overwhelmed or dissipated by an outside force, it takes a certain amount of time for it to be able to be used again, at least at its full capacity. For instance, in space combat in Star Trek, Stargate, and other sources, the shields will degrade as they’re repeatedly hit ("70%, 40%, 20%...the aft shield is down!" is a typical character quote) but for some reason, once its down, it can’t just be turned immediately back on again, despite the force field generator itself apparently suffering no damage.
This may be caused by a number of reasons. Force fields may need a minimum amount of power to operate, and need to build up a certain level of charge before it can project again. Or, in the case of absorptive force fields described below, the onboard capacitors which absorb energy from attacks become full and need to discharge, which can take a certain amount of time.
Selective Permeability: Except for the absorptive force fields detailed below, most force fields in science fiction seem to be permeable to certain select phenomena. For example, most force fields in on-screen science fiction allow both visible light and sound to pass through fairly effortlessly. Its acknowledged here that this is done mostly for storytelling purposes; a pure black, silent sphere surrounding a spaceship or base can advance the plot only so far.
Yet, if an actual built-in feature of the field, this does raise some interesting possibilities. Fields might indeed be designed to have selective permeability to certain frequencies of electromagnetic radiation, for example, for the simple reason of the ship being able to use its sensors and communication equipment effectively. Being blind during a battle or other crisis can prove just as dangerous to a vessel as not having a force field at all.
However, if a force field allows visible light to pass through, for example, what is to stop an enemy from using a visible-light laser to attack them? Or an a planet surface, if the characters can talk back and forth through a force field easily, doesn’t that mean that hypersonic weapons could also pass through unimpeded?
Force fields might also have other types of designed vulnerabilities. For example, in the Stargateuniverse, the personal force shields of the Gua’uld lords had a permeability window based on velocity. They would stop high-velocity projectiles hitting the field, such as a bullet, but would allow low-velocity objects, such as air, food, and the occasional thrown knife, to pass unimpeded.
However, there is one force all energy fields in science fiction seem helpless to block, and that is gravity, either from a natural source or artificially created. The reason for this is unclear, but it seems to be a feature in almost all types of force fields from across the science fiction spectrum, in films, TV series, novels, and video games alike.

ABSORPTIVE FORCE FIELDS
Tech Level: 17
Absorptive force fields completely absorb and retain all energy that hits them. The two major examples of this type of force shield are the black globes from the Traveller RPG and the Langston Field from the novel The Mote In God’s Eye by Larry Niven and Jerry Pournelle. Whether a scifi source will have absorptive or deflective force fields (or any force fields at all, for that matter) will depend greatly on how the physical laws of its universe work.
Traveller’s black globes get their name from what they look like in operation. Because they absorb all energy they encounter, including light, any ship using one will appear as a sphere of utter darkness.
All energy absorbed is routed to an array of high-energy capacitors attached to the black globe generator within the ship. With the advanced capacitor and energy-storage technology the Travelleruniverse has access to, this meant that black-globe-equipped vessels could absorb a truly impressive amount of punishment during battle. However, even they had limits, and when exceeded the capacitors would explode or melt down, often taking the entire ship with them. The system also had the downside of completely blinding all sensors and blocking all communication when on.
In order to avoid these pitfalls, ships with black globe generators often also came equipped with large and highly efficient radiator units on their hulls, used to bleed away the excess energy the force field would accumulate in its capacitors. However, these are useless while the globe was actually active, so in dangerous situations such as combat the crews used a strategy of flickering the globe on and off quickly, hundreds or even thousands of times a second. The ship would still be partially shielded from attacks, and could also bleed away the energy from its capacitors that could possibly destroy it as well. The amount of flicker was usually measured in percentages—30%, 50%, 90% etc, reflecting the amount of time in any given second that it was on-and usually reflected how much of an incoming attack’s energy it would absorb. Flicker strategies also allowed the ship to use sensors and communications, so the ship could still take advantage the black globe without being rendered deaf, dumb, and blind. Used in conjunction with other defensive technologies, flickering black globes proved to be a very effective means of ensuring a ship’s survival in extreme conditions.
The Langston field from Niven and Pournelle’s novel worked in many ways similar to a black globe, except in this case the field itself was the energy capacitor. As the field absorbed energy, it would work itself up the visible spectrum, first appearing a sphere of darkness like a black globe, but then turning red, orange, yellow, and so on up to violet and ultraviolet. The field re-radiates the energy it absorbs along its surface area, but sufficiently potent attacks can overwhelm its re-radiative ability and cause the field to overload. If the field overloads it just shuts down and leaves the ship vulnerable, but in some cases (such as in the Motie-modified ship in the novel) the field may become so overwhelmed that it incinerates the ship within.
Absorptive force field also have the added advantage of completely shielding the ship from most active and passive electromagnetic sensors when on.

DEFLECTIVE FORCE FIELDS
Tech Level: 17 The weapons of humanity prove useless against the Martians' deflective force fields. From the 1953 film version of War of the Worlds. Image copyright Paramount Pictures.

These are by far the most common type of force field seen in on-screen science fiction. The force fields seen in Star Trek, Star Wars, Stargate, and many other milieus are deflective barriers, even if the exact details of their effects vary with the source material.
These are somewhat inaccurately named. Though they do act as deflective barriers, they also absorb a certain amount of the energy that they encounter. The percentage of the deflection/absorption rate is variable from source to source, but in general these fields will deflect or re-radiate away much more energy than they absorb. Energy that is not deflected away is absorbed into the system and wears away at the field and/or its generator until the field dissipates.
These fields at times seem to have different deflection/absorption rates, depending on what hits them. For example, in Star Trek, the shields are often depicted as being able to handle hits by energy weapons much more handily that physical impacts, meaning that the force fields absorb a much higher percentage of the energy from kinetic impacts than they do the heat and nuclear radiation of the energy beams that strike them.
STRUCTURAL SUPPORT FORCE FIELDS
Tech Level: 18
Also called Structural Integrity Fields. They are often mentioned on Star Trek, but are also seen in sources as diverse as Iain M. Banks Culture novels and the comic-book version of Iron Man. Basically, these are force fields designed to be integrated and work with normal matter, in order to greatly strengthen and reinforce the latter.
There is some indication that electromagnetic fields can be used to ‘stiffen’ certain metals, but the punishment taken by materials in science fiction far exceeds what that technology could realistically do, indicating that some form of true force field is required. The force field may conform itself over the surface of the object, helping it retain its shape, or it may permeate the quantum structure of the object itself, reinforcing it on a subatomic level.
Either way, it allows materials in science fiction that use such technology to withstand some truly astounding damage, such as when the USS Enterprise can survive a near-hit with a nuclear bomb without its shields, or when Tony Stark’s armor can keep its wearer alive even while being hit by the mountain-shattering blows of the Hulk.
Because of the greater skill and finesse it would take to integrate force fields with matter without seriously deforming or damaging the latter, structural support force fields are considered one tech level higher than projected force fields.
SPECIALTY FORCE FIELDS
Tech Level: 19
These are force fields that have a much narrower purpose that as a general barrier against external hazards. Some might be designed against one specific type of weapon, other might be used to achieve a certain specific effect. Since this fine-tuning of the exotic particles needed usually takes more technical sophistication, the tech level for them is set higher than other types of force fields.
An example of a specialty force field would include meson screens from the Traveller RPG, which makes the particles in a meson gun decay upon first encountering the field, well away form the ship. The meson screen is a barrier of particles much like a normal force field, but only affects pi neutral mesons. It cannot, for good or ill, effect anything else, but in its source material it uses much less energy than a conventional force field and is actually much more effective against that one specific type of attack.
Cloaking devices from Star Trek and other sources also seem a type of specialty force field. They generate an ‘energy field’ that completely surrounds a ship that seems to only affect photons, bending light around it and rendering the craft invisible.