Laser guns have been the go-to staple for far-future science fiction for decades. Be they actual lasers or particle-beams that produce an energy pulse visual, they’ve rendered our movie and video game sci-fi battle scenes more seizure-inducing than a European night club. Directed Energy Weapons have been a focus of military research for some time, but just how close are we to actual, handheld laser guns, and how faithful will they be to their fictional portrayals?

The Phaser vs. The Blaster

Blaster

The most common types of laser guns in fiction can be divided into two main categories, which we’ll call the phaser and the blaster – any aficionado of sci-fi knows where we’re going with this. Popular in older sci-fi, the phaser, as seen in Star Trek, fires an uninterrupted beam of light that strikes a target near-instantaneously. But the phaser-style of laser gun has fallen into disfavor in the last couple of decades, being replaced with the far more cinematic blaster, which fires a discrete package of “light” or illuminated matter that can be observed as a distinct projectile. Star Wars popularized the blaster, so much so that even the new Star Trek movies have adopted the visual style.

While the official canon of both Star Trek and Star Wars describe – in painstaking detail – the fictional mechanics of their respective weapons, we’re going to base ourselves simply on their most commonly observed characteristics and whether our current technology can replicate the results.

The Projectile

Guns fire bullets. Bazookas fire rockets. Laser guns fire… lasers, right?

That’s the idea, at least. The projectiles that issue from phasers and blasters have distinctly different qualities which form the core difference between these two weapons. We’ll call a phaser’s projectile a beam and the blaster’s projectile a bolt.

UT3 Laser

The difference between a beam and a bolt is presented most simply in First Person Shooters. Typically, futuristic FPS games such as Unreal Tournament feature weapons that can be divided into two groups: projectile and hitscan weapons. With a hitscan weapon, the moment you click “fire,” the computer calculates a straight-line path, and the nearest object that intersects that path is struck. A projectile weapon, on the other hand, fires an object that travels through the air at a given velocity and – if the game’s physics are good enough – has a ballistic trajectory.

The distinction between hitscan and projectile weapons in video games is effectively the same as that between beams and bolts, for our purposes. When you aim a laser pointer at someone, the beam strikes the target instantaneously – or at least, near-instantaneously, since even light has a velocity. Put simply: a beam cannot be dodged; a bolt can be dodged, if it is traveling slowly enough.

Projectile Speed

Star Wars Blaster

In both movies and video games, we find examples of humans dodging bolts without the aid of supernatural abilities or bionic augmentations. This arguably renders bolts inferior to beams and even bullets for most anti-personnel purposes, and calls into question the science behind the projectile.

If the projectile is a laser, then it is traveling at light speed and cannot be dodged. If the projectile is a stream of accelerated particles, which is the most common explanation for such weapons, then it is merely traveling at roughly 670 million miles per hour. Barring any form of Force powers or other magical hokum, it doesn’t matter how fast your reflexes are – you aren’t dodging that.

But maybe we want to argue that the bolts aren’t actually being dodged, that the characters are instead dodging before the trigger is pulled. Fine, but then how do we explain the visual depiction of a bolt flying across the movie screen?

Movies traditionally play at 24 frames per second, and in order for a viewer to determine the direction of a blaster bolt, that bolt must be visible in at least two consecutive frames: one frame to serve as a reference, the next to suggest the movement. Modern rifles have a muzzle velocity of more than 3,900 ft/s, meaning a bullet would travel 3,900 feet in 24 frames, or 163 feet per frame – that’s greater than the length of half a football field. Even a humble Beretta pistol has a muzzle velocity of 1,250 ft/s, or 52 feet per frame.

Add to that the fact that the human eye can only process 10 to 12 separate images per second and we realize that we would actually need a minimum of about 3-4 frames for the human eye to process the direction the bolt is traveling in. That means that by the time your eye can register the movement of a Beretta bullet, it has moved at least 100 feet. Most fight scenes don’t take place on such scales.

What about long corridors and perspective shots? Doesn’t that put that 100 feet figure into the realm of plausibility? If it were a glowing Beretta bullet, maybe. But we’re talking about accelerated particles traveling at almost one million ft/s, or over 7,500 miles per frame. That’s over twice the length of the continental United States.

The conclusion is obvious: not only would a realistic bolt be moving too fast to dodge, it would also be moving too fast to be seen.

Projectile Appearance and Noise

Now, there is one saving grace for the blaster. Modern militaries make use of tracer rounds, which are bullets that include a pyrotechnic charge that leaves a visible trail. If you watch footage of tracers in action, you’d swear you’re seeing a blaster bolt.

If we concede that a blaster bolt is something that cannot be dodged, and the visual effect is simply the trail left by some form of tracer that is perhaps even latent to the bolt itself, then we have redeemed the bolt into the realm of plausibility. However, the implication is that your target would be dead before you saw the bolt, which would simply be a “ghost” of the actual projectile.

What about laser beams? Shouldn’t lasers be invisible?

To answer that, we need to clarify what we are seeing when we “see” lasers. A laser consists of concentrated photons, or particles of light. We don’t “see” light; we see the physical objects that light illuminates. When you direct a laser pointer at a wall, you see a red dot on the wall because the beam of photons is being concentrated on that spot. Point the laser through fog, and you’ll be able to see some of the beam because the photons are illuminating the fog particles in its path.

Whether we “see” a laser beam or not depends on three factors. The first is the wavelength of light the laser emits – many military lasers used for tracking are in the infrared range, invisible to the human eye. Regardless of other factors, infrared and ultraviolet lasers are inherently invisible to us. Green lasers happen to be the most visible to us simply because our eyes are most sensitive to that wavelength of light. The second factor is the number of particles in the air the photons have to bounce off of – the greater the number of particles, the greater the visibility of the beam. Lastly, the strength of the laser also matters. Even in the absence of fog, a powerful enough green laser beam will be visible to us by reflecting off individual air molecules.

What this means is that a weapons-grade laser could either be visible or invisible; the decision is up to the designer. An invisible laser seems to be the perfect stealth weapon for a sniper, who can steadily aim through a scope from an incredible distance and not have to compensate for wind or ballistics. However, as a sidearm, having a visible laser may be beneficial to aiming.

But what about the noise? Would we hear the distinct pew pew popularized in fiction?

Likely not, but we would hear something. The machinery that operates high-powered lasers, their power source, and their cooling equipment, will make noise, generally a low humming or buzzing. Likewise, a particle accelerator would also generate similar noise as the magnets hum with electrical current.

Recoil

Super Battle Droids

When a modern gun is fired, there’s a strong kickback that, depending on the caliber of the round, can be powerful enough to injure an operator who isn’t properly wielding the weapon. In fiction, blasters have distinct recoil, whereas phasers do not. Would a laser gun have recoil?

Recoil is the result of one of the fundamental laws of physics: the conservation of momentum. Before you pull the trigger, the total momentum of the bullet and firearm, taken as a system, is zero. After pulling the trigger, the total must remain zero, so whatever momentum is imparted to the bullet speeding towards your target must be matched by the recoil of the gun pushing back against you. Momentum is a function of mass and velocity, so given two objects with equal momentum, the one that is more massive will be traveling slower – that’s why the gun doesn’t kill you through recoil.

In actuality, we need to consider the momentum of both the bullet and the gases escaping the barrel created by the explosive combustion, and it turns out that the gases impart more recoil on the gun than the bullet itself. That’s why suppressors reduce recoil significantly: they divert and trap the gases, releasing them slowly over a long period of time.

In the case of a laser, there is no explosion adding gases to the system. Further, the “projectile” being emitted is a stream of photons, which are massless. Lasers are powered by focusing the traveling direction of photons emitted from atoms. When we apply energy to an atom, it enters an “excited” state, and it returns to its normal state by releasing photons. A piece of red-hot metal glows because its atoms have been excited through heating and are releasing photons. While photons do exert some pressure – the concept of solar sails depends on this fact – that pressure is negligible for our purposes.

What about a particle-beam weapon? Again, it would not be powered by exploding gases. Particle accelerators use electromagnetic fields to send particles speeding along in a desired direction. There is some debate over whether or not this would produce appreciable recoil, but we’ll err on the side of “no recoil” for the following reasons. Firstly, there are no gases or other matter added to the system, which we’ve described to be a significant source of recoil in modern guns. Secondly, atomic and subatomic particles are so minuscule that even when accelerated to near-light speeds, their momentum is negligible. And lastly, electromagnetic fields violate Newton’s law of action and reaction and do not conventionally follow the principles of conservation of momentum, though an explanation as to why is beyond the scope of this article.

Physics Sidebar

Prospective Real-Life Laser Guns

So we’ve concluded that an actual laser gun would have no appreciable recoil, wouldn’t emit a pew pew sound, would fire a projectile that may be invisible or unobservable, and cannot be dodged. Now, how close are we to having the technology to produce a practical, handheld laser gun?

Let’s take a look at our top prospects.

Actual Lasers

We already have surgical lasers that can cut through human flesh, manufacturing lasers that slice through steel, and military lasers undergoing R&D that can detonate enemy missiles midair. Why haven’t we already made a laser gun?

The problem largely lies in power consumption. A typical laser pointer uses 1-5 mW of power. A high-speed CD-RW burner uses 100 mW, 10 to 100 times that of a laser pointer. A surgical laser uses 30-100 W, up to 1000 times that of the burner. An industrial cutting laser could use up to 3000 W, 30 times that of the surgical laser. But for a laser to be classified as “weapons grade,” it needs to reach the 100 kW threshold, over 30 times that of an industrial cutting laser. That’s also the average power requirement of a couple dozen houses.

While we do presently have the technology to make such powerful lasers, both the laser device and the laser’s power source are massive. The Boeing YAL-1, now decommissioned, was basically a flying laser gun housed within a jumbo jet, and it was “only” a megawatt-class laser that required two minutes to burn a hole through an incoming enemy missile.

At this point, it’s just a matter of engineering and advances in miniaturization. If it seems hard to believe we’ll ever get laser weapons down to handheld size, just remember that the first computer weighed more than 60,000 lb, measured roughly 8 by 3 by 100 feet, and consumed 150 kW of power.

Electrolasers

Basically a long-distance Taser, the electrolaser comes very close to Star Trek‘s phaser, complete with a stun setting. An electrolaser works by firing a non-deadly laser that rapidly heats and ionizes the air around it to form plasma, then sends an electric current down that plasma “channel” to the target.

Lightning works similarly. Though we don’t have a great understanding of how the air initially ionizes, the lightning bolt travels along an electrically-conductive plasma channel that consists of a soup of positively charged air molecules and the electrons that have been stripped from them. Since the 1970s, researchers have been trying to use lasers to trigger lightning strikes.

No electrolasers have yet been built, but the science is there. Successful tests in 2012 have shown that an electric discharge can travel along a laser beam, and weaponized applications are in development. We’re getting close to Unreal Tournament‘s lightning gun.

Pulsed Energy Projectile

Formerly under development by the U.S. military, the PEP was a weapon intended for riot control. It worked by emitting an infrared laser pulse that, upon striking a target, vaporized enough molecules to create a small explosion of plasma. The resulting pressure wave could stun and knock down a person, and the released electromagnetic radiation had proven to cause pain and temporary paralysis in animal experiments.

The weapon weighed about 500 lb and would have been vehicle-mounted at the time that it was canceled in the mid 2000s. According to the Department of Defense, “The research finally concluded that the PEP laser could not reproduce the required waveform characteristic of a non-lethal weapon.”

While this is pure speculation, it is possible to interpret this to mean that the weapon caused damage to living beings, which would render it unusable for riot control purposes, and it was too cumbersome or fragile for battlefield deployment as a deadly weapon. Again, advances in miniaturization may one day lead to a revival of this technology as a portable, deadly gun.

Plasma Gun

UT3 Pulse Rifle

Corporations have been funding research into weapons that fire plasma to cause severe burns, melting, and even death, though no practical examples have been produced. As with the case of laser guns, plasma guns would require more power than a handheld device can currently supply.

Even with a portable fusion reactor, though, plasma guns have other technological hurdles to overcome. Until some way is found to make a plasma beam self-sustaining over a longer period of time, it would be stopped by simple air resistance; the resulting gun would be similar to a blow torch. Generating a channel with a laser beam, as with the electrolaser, could be a way to circumvent this problem.

But nature herself seems to already have the solution: ball lightning, a phenomenon that we still don’t understand. One theory is that ball lightning is a spinning ring of plasma, which researchers have been able to reproduce in labs.

The plot thickens when we consider that a U.S. government research project called MARAUDER – an acronym for Magnetically Accelerated Ring to Achieve Ultra-high Directed Energy and Radiation – was successful in producing rings of plasma and balls of lightning that allegedly exploded with devastating effects upon striking a target. The project was first reported in 1993 and classified later that year. No further details about project MARAUDER have surfaced since.

Particle-Beam Weapons

Both Star Trek and Star Wars describe their phaser and blaster as particle-beam weapons that fire atomic or subatomic particles at near-light speeds, an idea founded in firm science. Imagine taking a particle accelerator like CERN’s Large Hadron Collider and weaponizing it.

A particle-beam weapon is similar in concept to a railgun, which uses electromagnetism to launch projectiles at hypersonic speed. Hurl a physical object at someone with enough speed and it’ll cause damage. Fire a stream of subatomic particles at near-light speeds and, given sufficient power and time, you can tear through virtually any physical material.

Again, a key problem lies in miniaturizing the technology. Ongoing research is seeking to apply military use to particle-beams, but we’re a long way off from handheld weapons.

Active Denial System

ADS

Finally, we arrive at our most promising lead. Also known as the Heat Ray, ADS is an actual nonlethal weapon developed by the U.S. military that was deployed in Afghanistan in 2010, but withdrawn before it saw combat. Mounted on a humvee, the weapon heats a target with microwaves that excite the water and fat molecules in the skin.

How effective is ADS? Most human test subjects reached their pain threshold within only three seconds of exposure, and none could endure more than five seconds. “For the first millisecond, it just felt like the skin was warming up,” said one of the test subjects. “Then it got warmer and warmer and you felt like it was on fire… As soon as you’re away from that beam your skin returns to normal and there is no pain.”

Both the U.S. Marines and police are working on portable versions of the Heat Ray. While a far cry from a flashy laser gun, this is the closest thing we have to a functional, practical, directed energy weapon.

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