RocketCat Cheat Sheet
  1. Any laser gun powerful enough to shoot a hole in somebody can probably instantly blind you if it hits your eyes. Even if it just reflected off something shiny. It is a danger to anybody nearby, with "nearby" defined as "closer than the horizon."
  2. It takes lots of tricky engineering to make a laser bolt do more damage than your average bullet. And to be more efficient than your average bullet
  3. Shooting a continual laser beam at somebody is like spitting into the wind. Vaporizing metal or flesh from the target will mess up the beam. Instead the beam should be a series of short pulses.
  4. Lasers need large batteries because they are power hogs
  5. A "heat-ray" is a continuous beam laser. It is like a flame-thrower. Made of energy beams
  6. A "blaser" is a pulsed beam laser. It is like a bullet. Made of energy beams
  7. A laser aimsight can be the actual weapon optics, much like an SLR reflex camera eyepiece. This makes the aimsight vastly more accurate than iron sights
  8. If you are having a raygun fight in an atmosphere, you want the laser gun to use some color of visible light or near-infrared frequencies
  9. Particle-beam weapons are far more efficient at doing damage to the target compared to lasers
  10. Particle-beam weapons can give serious doses of deadly radiation to the gunslinger, due to radiation backscatter
  11. Plasma weapons do not work

Science fictional "ray guns" that shoot futuristic beams of energy instead of boring mundane bullets have been popular since about 1898 when H. G. Well's introduced the "heat ray" in his novel The War of the Worlds (though Zeus had been zapping people who ticked him off for thousands of years). They were popular in Flash Gordon, Buck Rogers, the Lensman series, and Tom Corbett Space Cadet. As their popularity wained they were given a new lease on life when Bell Labs invented the laser in the 1960's, and again later with the phasers of Star Trek and the blasters of Star Wars. However they started going out of style in the mid 1980's, probably due to the testosterone-dripping slugthrower pulse rifles in the movie Aliens.

Various real-world militaries are trying to develop actual combat lasers, under the term Directed Energy Weapn (DEW). Which sounds so much more pragmatic than "ray gun".

The two main types are Lasers and Particle Beam Weapons.

The main advantages of laser weapons include: weapon bolt travels at the speed of light, excellent accuracy, damage inflicted by the bolt can be dialed up or down, lasers have no recoil, and the "ammunition" (i.e., electricity required per bolt) is much more inexpensive than the equivalent conventional bullet.

The main disadvantages of laser weapons include: it still requires huge amounts of power, bullet ammo takes up far less space than power generators, it has far more of a waste heat problem than a conventional firearm, and the energy in a given bolt is severely reduced by dust, smoke, clouds, or rain.

The main advantage of particle beam weapons is they have penetration that make lasers look like throwing a handfull of thistledown.

The main drawbacks of particle beam weapons is they are power hogs, they are difficult to reduced to pistol size, and Terra's atmosphere will scatter enough of the beam to give the firer a lethal dose of radiation.

Refer to the weapon energy and weapon range tables to compare energy weapons to slugthrowers.

"Your knowledge of weaponry is impressive."

"A holdover from my game-hunting days. Remember them?"

"I remember disapproving of them."

"Well, combustion (gunpowder) weapons are still in demand by 'sportsmen' who find their sense of masculinity cheated by the lack of recoil in energy weapons."

From HEALER by F. Paul Wilson


First a safety note. Pretty much zero science fiction stories, movies, or TV shows mention that laser sidearms have the ability to permanently blind anybody closer to the weapon than the horizon. If the beam is in the frequencies that can penetrate the cornea of the eye, and the beam reflects off a door nob or other mirrored surface, anybody whose eyes get flashed by the beam is going to need a seeing-eye dog. There are more hideous details here.

"Laser" is an acronym for Light Amplification by Stimulated Emission of Radiation. A laser weapon can cut through steel while a flashlight cannot due to the fact that the laser weapon beam can have a higher intensity. This is by virtue of the laser's use of coherent light, which pays an important part in achieving heightened intensity at a distance. Nobody wants a laser pistol with a range of three millimeters.

Coherence means all the photons in the beam are marching in lock-step with each other, instead of every-which-way like ordinary light. By analogy, a unit of army troops marching in step can inadvertently cause a bridge to collapse, while the same number of people using the bridge in a random fashion have no effect. Almost by definition the only thing that can emit coherent light is a laser.

A laser is composed of three main components

  • An energy source (usually referred to as the pump or pump source)
  • A gain medium or laser medium
  • Two or more mirrors that form an optical resonator

In Dr. Theodore Maiman's original laser, the pump source was a xenon flashtube, the laser medium was a rod of synthetic ruby, and the dielectric mirrors on each end of the rod formed the optical resonator.

An important fact to note is that the laser medium has to be "pumped" by filling it with a higher energy/shorter wavelength compared to the laser beam that will emerge. You cannot pump it with the same wavelength as the result beam, or the act of pumping the laser will simultaneously stimulate emission, and you'll never get anywhere.

Also note that you can run the result laser beam through certain materials to do tricks like frequency doubling. This will allow one to send a 1064 nm infrared laser beam (from a Nd:YAG laser) thorugh a lithium triborate frequency doubler and turn it into a 532 nm green laser beam.

So the two things a laser weapon needs are [a] a source of coherent light (a laser) and [b] milspec beam focusing optics. A flashlight has neither, a laser weapon has both. A laser pointer just has [a].

Kerr points out a flashlight can cut through steel as well, IF it is very powerful and very close (making up for the lack of coherent light and optics). Edward Teller's EXCALIBUR nuke-pumped x-ray laser is pretty much a very powerful flashlight, in light of the fact that the design contains no focusing lenses or mirrors at all. So while EXCALIBUR was a laser because it emitted coherent light, it wasn't strictly a laser weapon because milspec x-ray optics are an unsolved problem. Ergo: powerful x-ray flashlight. The only reason EXCALIBUR had any range at all was that it used about six orders of magnitude more beam energy than a proper weapon would need (i.e., it was horribly inefficient).

Luke Campbell has an in depth analysis of laser weapons for science fiction on his website. Also check out Future War Stories Armory: LASERS: the Killer Light. There is a list of various real-world lasers and their lasing frequencies here.

From a science fictional standpoint, Dr. Campbell is of the opinion that laser weapons will fall into three broad catagories:

Heat Rays

Lasers that shines a beam of near constant power on its target for a prolonged period of time (from a few hundredths of a second or more).

As a weapon they are not as efficient as a blaster, and they do damage more slowly. They are sort of a futuristic flame thrower or acetylene torch. Heat rays use frequencies longer than 200 nanometers: visible light and infrared.


Lasers that emit a pulse of light so intense that it causes the matter it hits to violently explode.

A stream of pulses comprising a single laser bolt is the key to making a laser inflict bullet levels of damage. Blasters use frequencies longer than 200 nanometers: visible light and infrared.

Ray Beams

Lasers that emit needle-thin beams that produce a white-hot plasma along their path and easily burn deep holes into their targets.

The main difference between ray beams and other lasers such as heat-rays or blasters is that they use extreme-ultraviolet, x-rays, or gamma-ray frequencies instead of visible light frequencies. In other words, they use "vacuum frequencies", those frequencies shorter than 200 nanometers which are readily absorbed by Terra's atmosphere. As a side note, anything shorter than 10 nanometers is what scientists call "ionizing radiation" and everybody else calls "OMG We're All Freaking Gonna Die deadly nuclear radiation".

Oddly enough, while vacuum frequencies are absorbed by Terra's atmosphere they are not effected by plasmas. Which is the exact opposite with respect to non-vacuum frequency laser beams. This means that you do not have to pulse vacuum frequency lasers in order to have bullet levels of damage.

Dr. Schilling does not think the laser pistol is as far fetched as most believe. Erik points out that the problem with a man-portable laser pistol would be the power source. Kinetic weapons are probably going to outperform beam weapons for man-portable sidearms for a long time.


I'll assume a 50-year time frame with no particular haste in developing directed-energy small arms and no fundamental breakthroughs. Only technology currently on the drawing board, in however limited a form, is allowed, but in 50 years expect today's crude laboratory demos to be refined, mature technologies.

I'll also use a standard military or police service handgun as the baseline - you can easily extrapolate down to a compact pistol or up to a small submachine gun-equivalent if you like, but going up to rifle or heavy-weapon scales is a bit trickier.

There are four basic technological approaches I would consider based on my personal knowledge, all of which would lead to similar end results if they worked at all.

Phase-locked diode laser arrays
Lots of microlasers on a chip, all working together. Extremely efficient, if you can actually get them to work together.
Diode-pumped YAG lasers
Lots of microlasers on a chip, each working alone. They won't produce a good beam that way, but if you tune them to the right absorption band and direct them all into a YAG crystal, you can get the latter to lase quite efficiently.
Pulsed linear induction accelerators
Fairly conventional technology for producing high-energy, high-current electron beams with external magnetic fields. This one will need to be pushed right up to the theoretical limits to work on a handgun scale, and it will need an unconventional electron source such as a pseudospark discharge.
Wake field accelerators
Clever way of producing high-energy electron beams using the internal electric fields of forced plasma waves. Still in it's infancy, potential unknown but may well be adequate in the long run.
Dr. Schilling

Heat Ray

A heat ray is a laser that shines a beam of near constant power on its target for a prolonged period of time (from a few hundredths of a second or more). It uses non-vacuum frequencies, wavelengths longer than 200 nanometers (visible light and infrared). Andre Norton called them "flamers."

In other words they are like flame-throwers with no flame, just the intense heat.

Engineering-wise it is much easier to make a heat ray than a blaster. The latter requires complicated electronics to create the precise laser pulse trains, heat rays just need an on/off switch. But heat rays waste lots of energy by their brute force approach. As soon as the beam hits the target, the target emits a plume of plasma that jets right into the beam path. The beam wastes large amounts of energy burning through the plasma plume before it reaches the target to do further damage. Which makes a fresh plume of plasma. Blasters use a clever technique to avoid this.

This is bad since laser weapons already have a big problem trying to squeeze a worthwhile power source into something man-portable. The inefficient use of laser energy by heat rays means the power source has to be bigger or it has to contain less laser-time before it runs dry. Or both.

In a workshop, heat rays can be used like an acetylene torch.

In battle they can be used much like flame throwers, along with the drawback of making the user into the enemy's priority target. If the enemy soldiers seen [1] a bunch of you guys ineffectually making "pop-pop" noises with rifles and [2] one of you with a ravening inferno beam of death turning enemy soldiers into barbecued corpses, which one of you do you think the enemy is going to shoot at? Historically soldiers armed with flame throwers had an average life-span on the battlefield of about four minutes (the technical term is "bullet magnet"). Granted, part of that mortality is due to walking around a flying bullet infested battlefield with a big vulnerable tank of gasoline strapped to your back, but still. So a soldier armed with a heat ray might survive for five minutes instead of only four.

The illuminated surface of the target is heated up hot enough to cause softening, warping, blistering, cracking, charring, cooking, ignition, melting, or vaporization. The ray instantly scorches or ignites the surface but takes a bit of time to burn through to the inner layers. Which means heat rays have problems with armored targets. Even an unarmored target can avoid damage by jumping out of the way when they feel the pain. The target can also protect itself by spinning or turning. This constantly puts fresh armor or surface layers into the path of the heat ray, forcing it to start back at square one.

Heat rays are very ineffiicent weapons, unless they have a wide spot size in order to hose wide areas as a futuristic flame-thrower. Alternatively they could be set to raster-scan the beam over the target's body.

If you want to go that route, for a flash lasting from a fraction of a second and several seconds:

Energy densityInjury
10 J/cm2 to 20 J/cm2First Degree Burns: Epidermis damage.
20 J/cm2 to 35 J/cm2Second Degree Burns: Damage extends into partial dermis.
35 J/cm2 to 50 J/cm2Third Degree Burns: Damage extends through entire dermis.
> 50 J/cm2Fourth Degree Burns: Damage extends to muscle below dermis.
125 J/cm2Exposed hair and clothing burst into flame
400 J/cm2Exposed flesh flashes into steam, flaying exposed body areas to the bone

Equation to calculate energy density can be found here.

First degree burns cause pain. Second or third degree burns covering more than 15% of the body will likely result in death if not given medical attention, incapacitation will be rapid and shock will occure within minutes. Skin color significantly affects susceptibility, light skin being less prone to burns. The table above assumes medium skin color.

Percentage of skin burnt can be estimated by the rule of nines. Since heat-ray victims will only be irradiated on the side facing the ray, the percentages below should be halved.

Anatomic structureSurface area
Anterior head4.5%
Posterior head4.5%
Anterior torso18%
Posterior torso18%
Anterior leg, each9%
Posterior leg, each9%
Anterior arm, each4.5%
Posterior arm, each4.5%

A heat ray with a 60 centimeter diameter spot size on the target will cover the torso of an average adult human, irradiating 20% of the body with one flash. The spot area wil l be about 3000 square centimeters. To irradiate that area with 128 J/cm2 will take a whopping 384 kilojoules (128 * 3000 = 384,000).

Luke Campbell says "It is not very energy efficient compared to a bullet, but if batteries or fuel are cheap or lightweight or convenient it might still be better overall (after all, bullets are not energy efficient compared to an arrow, but we still use them)."

Luke Campbell wants to make clear that while "heat-ray" is a vivid name, according to physics it is not actually a ray composed of heat. It is a ray that heats what it illuminates.


The key to making a laser do bullet levels of damage is pulsing the laser. This is what distinguishes Luke Campbell's "blasters" from other kinds of lasers.

Consider a laser beam striking an evil Asteroid Pirate. The beam strikes human flesh, turning the water of a thin layer of skin into plasma (ionized gas, not blood transfusion supplies). Where does the plasma go? Mostly into a jet aimed right back at the laser beam.

The jet of plasma partially shields the Asteroid Pirate from the rest of the laser beam. The beam has to waste energy to burn through the cloud of plasma, which reduces the amount of energy actually hitting the asteroid pirate.

{Note this only happens with laser frequencies longer than 200 nanometers: visible light and infrared which are strongly absorbed by plasma. Laser frequencies shorter than 200 nanameters (extreme-ultraviolet, x-rays and gamma-rays) totally ignore plasma. Keep in mind that making a sub-200 nm handheld laser is really really hard.}

The secret to avoiding the instant plasma armor problem is pulsing the beam.

Take one kilojoule's worth of laser energy and divide it up into 1,000 single-joule pulses separated by 5 microsecond intervals. Focus it down so the spot size is about one millimeter. The first pulse hits asteroid pirate epidermis. The pulse is fast enough and the energy is concentrated enough so that it creates a little explosion. This blasts a crater in the asteroid pirate's flesh up to four centimeters in diameter, depth of 2 centimeters.

Plasma and bits of flesh fly into the path of the beam but there is no beam there. The explosion was done by a single pulse, but the next pulse won't arrive for another 5 microseconds. The plasma vanishes almost instantly. 5 microseconds later roughly 90% of the flesh debris has cleared the beam path. Now laser pulse #2 arrives, sailing through a void with no plasma or flesh bits, and arrives at full strength causing a second explosion at the bottom of the crater. This creates a second crater. The two craters have a combined depth of 4 centimeters. Repeat for the remaining 998 pulses.

Dr. Schilling calculates you can bore a hole through soft body tissue about 30 centimeters deep before the tunnel collapses (taking about 0.005 seconds for all 1,000 pulses). Roughly the equivalent to a high-velocity pistol bullet or a small centerfire rifle.

The 5 microsecond pulse rate is optimized for soft body tissue, other rates are optimal for steel or other materials.

Sample Blaster Bolts
of pulses
Schilling1 kJ1,0001 J5 μs1 mm
Campbell assault eq.1 kJ10010 J1 μs10 mm
Campbell Light Laser Pistol1.2 kJ6020 J4 μs
Campbell Battle Laser10 kJ50200 J10 μs

(ed note: this paper is about streams of water drops impacting a pool of water instead of laser pulse trains impacting human flesh, but the effects are similar.)

When a water droplet impacts a free surface with sufficient velocity, the momentum transfer results in the formation of a hemispherical cavity expanding radially from the point of impact. This cavity continues to expand until the kinetic energy is completely converted to potential energy. Pumphrey and Elmore equated the potential energy of this subsurface cavity with the kinetic energy of the impacting droplet, concluding that the magnitude of the cavity radius is proportional to impact velocity and droplet diameter.

Less is known about the effect of several droplets impacting a water surface in rapid succession. The first impacting droplet creates a subsurface cavity as described above; the second droplet creates a very similar result, but with the cavity initiating from the base of the first. A third droplet and a fourth droplet expand the depth and compound nature of the cavity. We refer to the nested cavity shape formed in the wake of multiple droplets as a matryoshka cavity (named after Russian nesting dolls). This phenomenon is only observed when a series of droplets impacts a free surface with a sufficiently high temporal frequency such that subsequent cavities form before the initial cavity closes. One may be inclined to conclude that the ideal droplet frequency should involve a droplet impacting just as the previously formed cavity has reached its apogee. However, this would result in the lower portions of this complex cavity forming as the upper levels collapse. We conjecture that the ideal frequency is higher than this definition, allowing the top of the cavity to continue to expand outward while the bottom is extending downward. Of course, the upper bound on droplet frequency would be the case where the droplets are so close together that they coalesce to form a single jet, which results in a different impact event.

See video here

As we approach this ideal impact frequency, larger compound cavities can be formed, extending much deeper below the free surface and lasting longer than a cavity generated from a single droplet impact. Rather than producing the spherical cavity observed by Worthington, a droplet stream produces a long conical cavity. Fig. 2 presents an extensive cavity formed by approximately 15 droplets impacting the water surface in succession, and is approximately 14 times deeper than a cavity created by a single droplet. It is likely that this image does not represent the upper limit of the cavity proportions that can be achieved.


Dr. Schilling

Whether you use lasers or particle beams, you'll need a bit over a kilojoule of output energy to reliably incapacitate a human target. In the case of a laser weapon, that energy would be subdivided into ~1 joule pulses at ~5 microsecond intervals, to achieve penetration in the face of a laser's natural tendency to deposit energy at the target's surface. Particle beams don't have that problem; boost the electrons up to a few hundred MeV, and you can dump the whole kilojoule's worth at once.

The plasma clears away easily in that time frame; debris is the real issue, and the driving force between the 5 microsecond pulse rate. That allows roughly 90% of the debris to clear the beam path, assuming a 1mm beam and instantaneous 1J pulses. 1 joule every 5 microseconds is optimal against soft tissue, other materials will want different pulse trains.

I'm assuming a weapon designed to penetrate ~30cm in soft body tissue. This gives about 15cm in bone or plastic, 5cm in brick or concrete, or 2.5cm in steel or most ceramics. Synthetics won't be very good at stopping energy weapons, even tough ones like kevlar, but you might be able to find a ceramic that could stop a laser beam with a centimeter's thickness or so. Particle beams are tougher to stop; it mostly comes down to sticking mass in the way without regard to material properties.

(ed note: if my slide rule is not lying to me, 1000 pulses at 5 microseconds per pulse will take 0.005 seconds. 1000 joules in 0.005 seconds is equivalent to 200 kilowatts)

Luke Campbell

Keep in mind that in tissue, the cavity blasted out will collapse back on itself in a few milliseconds (and probably re-expand and collapse again in pulse-like oscillations for a few cycles).

Dr. Schilling

Yes, and this is a problem if you want to push the penetration much above the 30cm I specified. If your pulses come fast enough to gouge out a meter-deep path before the surrounding tissue recoils back into the cavity and blocks the beam, they come too fast for the per-shot debris to clear the beam.

In soft materials, vapor expansion will carve out a hole much larger than the original one millimeter — I got four centimeters maximum hole diameter for soft body tissue, so the effect should be at least equal to a modern high-velocity pistol bullet, and perhaps comparable to a small centerfire rifle. Brittle materials are likely to shatter within a similar radius, tough stuff like steel will show little effect beyond the original hole.

And no, mirrors will not work as armor. The best finish you can reasonably expect to keep on an exterior surface, will still absorb 10-20% of the incident energy, which will be enough to burn through the outer layer on the first pulse. And the rough and now hot interior will be even less reflective.

I also mentioned earlier that lasers would likely have to have pulse energy and frequency tuned to the specific material being targeted. It might be possible to do this automatically, based on crude spectoanalysis of the material vaporized in each pulse, but if not expect penetration to be roughly halved if a laser weapon is fired at a target it has not been optimized for. Target-shooting lasers won't be optimized for flesh, and certainly not for ceramic armor, so there may be legal implications here. Particle beams are less likely to suffer such inconveniences.

Taking into account the inefficiency of the system, the input energy will likely be somewhere between two and five kilojoules per shot. So you could get fifty to a hundred shots from a pistol-sized non rechargeable energy source, or half that with a rechargeable battery. Automatic fire at anywhere up to 20 Hz (1200 rpm) shouldn't be a problem in the short term, though might cause cooling problems if you keep it up.

You also need to focus the energy on the target, with a spot size of a millimeter or less. With a laser, that gets kind of tricky. A 5-centimeter mirror, about the largest you can really imagine on a pistol, gives an effective range of perhaps sixty meters, beyond which the weapon starts losing penetration quite rapidly.

Luke Campbell

If you are already talking about the laser excavating cavities several centimeters in diameter, sub-millimeter spot sizes do not seem necessary, you just need a moderate fraction of the cavity's maximum size.

Dr. Schilling

No, you still need to get down to a millimeter or so to flash-boil water in a layer ~one optical depth in thickness. Once you do that, the steam will expand and spread the damage around, but if you don't hit the threshold for turning water into steam all you do is warm up the target.

And the mirror needs to adjust for target range - adaptive optics (flexible mirror with microactuators)coupled to a laser range finder seems to be the way to go here - you've already got the pulsed laser part of the rangefinder.

Conversation between Dr. Schilling and Dr. Campbell

Luke Campbell

{amount of damage caused by battle laser shot: 10 kJ per shot, made up of 50 pulses of 200 J each, spaced 10 microsecond apart} I use my damage calculator here which lays out all of my physical assumptions and approximations, but which I think captures the basic physical processes of crater gouging. Since stress is concentrated at the tips of cracks, you may get individual cracks propagating beyond the distances listed below in brittle materials, but severe pulverization should be limited to approximately the distances given (as observed in impact and explosive craters).

Incident on meat, the aforementioned pulse train will blast out a hole 53 cm deep and 2.2 cm across (this is probably reported to one more significant figure than is justified). The diameter of the temporary cavity will be about 10 cm, but since muscle is highly elastic this will probably cause only bruising beyond the 2.2 cm permanent hole. Adding gristle and bone doesn't change this much - you get the same permanent cavity and depth in gristle, while bone will be drilled through to a depth of 29 cm, a permanent cavity diameter of 1.2 cm, and shattering and fracturing out to 1.45 cm diameter. Note that a typical person will be about 20 cm to 30 cm through the torso (depending on orientation), so this pulse would not only shoot through a person, but through the guy behind him as well.

Incident on plastic — in this case high density polyethylene — the pulse train will blast out a 32 cm deep and 1.3 cm across hole, with possible plastic flow out to 2.43 cm diameter.

Incident on sandstone, you get a 25 cm deep hole, 1.1 cm across, with shattering and cracking out to 2.1 cm. On granite, the hole is essentially the same except that shattering and fracturing is limited to 1.5 cm diameter. On concrete, the hole is again about the same depth and width, but now you can expect shattering out to about 3 cm.

Against structural steel, you get a 16 cm deep hole that is 0.65 cm across, and possible cracks or permanent deformation out to 1.1 cm. The very strongest maraging steels have the same size hole, but will lack any permanent deformations in the vicinity of the hole.

A representative titanium alloy might get an 18 cm deep hole 0.74 cm across, with possible permanent damage out to 0.84 cm diameter. Aluminum alloys will get drilled to 19 cm and 0.79 cm across, with possible permanent deformation out to 1.5 cm diameter.

High tech armor is likely to be some sort of carbon, perhaps diamondoid, fullerite, or nanotube weave. Against diamond I get a hole depth of 6.1 cm and a 0.26 cm hole diameter. Expect permanent damage out to 4 cm in the form of shattering and cracks. Against fullerite and nanotubes, the hole will be 7.7 cm deep and 0.32 cm in diameter, with possible permanent damage out to 0.41 cm.

Anthony Jackson

(Luke Campbell: 10 kJ per shot, made up of 50 pulses of 200 J each, spaced 10 microsecond apart)

Why that level of overkill? You should get the same penetration out of 100 pulses of 25J each, spaced 5 microseconds apart. You'll just have a hole that's half as wide, and you've just dramatically cut the energy requirements.

Luke Campbell

Two reasons, all relating to the fact that the hole is half as wide.

First, very large aspect ratio holes may be problematic to drill, based on issues of the ejecta interacting with the beam and the hole. With the pulse parameters I used, I'm looking at a 25:1 aspect ratio - which is probably doable although the hole will likely have constricted significantly near the end. At half the width, the aspect ratio will be more like 50:1, which is pretty extreme and may be unachievable. Also, if the hole is constricted, each subsequent pulse will produce a smaller bang, which will gouge out a smaller crater, which will in turn reduce the penetration from this optimistic assessment. In the limit of lots of small pulses, this should give a penetration that depends on the logarithm of the number of pulses, which quickly reaches a point of diminishing return.

Second, your range for maximum effect is cut in half, since you need to focus the pulses to within half the width to efficiently blast out the crater. Against diamondoid armor, the 200 J pulses require a 0.26 cm spot size for maximum effect and a 1 micron wavelength, 6 cm aperture laser will be able to be effective out to about 120 meters with a perfect Gaussian beam. If the craters are only half as wide, you would need to be twice as close.

Although now that I think about it, all my previous figures on the beam power were from the figures on power consumption, not beam power. Since I assumed by lasers were 50% efficient, all the previously stated beam powers are too large by a factor of 2 (and the details on the pulse trains which I retro-fitted to give the right beam power will be off as well). Ah well, I plead that I was distracted (I had just learned that I was going to be a daddy).

Anthony Jackson

(Luke Campbell: First, very large aspect ratio holes may be problematic to drill...)

Hm. On reflection, this suggests that the ideal number of pulses in a blast may be fixed (probably somewhere in the 20-100 range), since the aspect ratio is basically about half of the number of pulses.

(Luke Campbell: In the limit of lots of small pulses, this should give a penetration that depends on the logarithm of the number of pulses...)

Pretty sure it's order 1/3, since the lost energy tends to go towards making the hole wider.

(Luke Campbell: Second, your range for maximum effect is cut in half, since you need to focus the pulses to within half the width to efficiently blast out the crater...)

On reflection, this may be problematic for unrelated reasons. Air breakdown in clean air occurs at upwards of 1010W/cm2, but in dirty air it can drop down to 108W/cm2 or so. Your 0.26 cm spot size is 0.05 cm2, so the dirty air limit is around 107W or 10J/microsecond. For clean air, the 200J pulses are likely not a problem.

Luke Campbell

(Anthony Jackson: Hm. On reflection, this suggests that the ideal number of pulses in a blast may be fixed, probably somewhere in the 20-100 range)

Yeah, that's the conclusion I've been coming to.

(Anthony Jackson: Pretty sure it's order 1/3, since the lost energy tends to go towards making the hole wider)

I can see this is true if you are mainly working via melting or evaporation of the material. If the pulses are blasting out a void, however, the energy deposited on the sides of the hole may not be sufficiently intense to deform the material. Of course, the hypersonic jet of ejecta may be able to strip material from the sides of the hole. So we are looking at penetration scaling at somewhere between the 1/3 power and logarithmically for large numbers of pulses. For small numbers of pulses we should, of course, be in a linear regime.

Looking at pictures of various aspect ratio laser drilled holes, the opening to the hole looks to have about the same radius regardless of aspect ratio, which is about the same as the width of the beam. As the aspect ratio of the hole increases, the hole constricts with depth, eventually becoming significantly narrower than the beam.

I am not sure if the same mechanisms that operate in close focus laser drilling necessarily take place in holes drilled as part of an attack by a laser weapon. For example, in laser machining the walls of the hole are often used as a waveguide to extend the depth of field of the laser beam. For weapons, this will be irrelevant at significant ranges. If loss due to multiple reflections down the waveguide is responsible for much of the constriction, then this will not be as much of an issue for laser weapons.

For pulse lasers, as long as you can get most of the energy of the pulse into a given area of the target material, you will blast out a full sized crater. So suppose the crater is 1 cm across (and thus you have a maximum spot size of 1 cm in which to focus your beam for maximum effect), and also suppose your beam is focused to 1 mm. You will continue to blast out full sized craters until ejecta deposition constricts some part of the hole to less than 1 mm. This will result in a much deeper hole than if your beam started out close to the threshold limit of 1 cm.

(Anthony Jackson: On reflection, this may be problematic for unrelated reasons. Air breakdown in clean air occurs at upwards of 1010W/cm2, but in dirty air it can drop down to 108W/cm2 or so. Your 0.26 cm spot size is 0.05 cm2, so the dirty air limit is around 107W or 10J/microsecond. For clean air, the 200J pulses are likely not a problem.)

This is a very interesting observation. It may be that in air we can never be able to reliably penetrate carbon-armor materials.

Anthony Jackson

Beam divergence for a near-IR laser (such as neodymium-doped yttrium aluminium garnet (Nd:YaG)) can be estimated as on the order of 1mm per (aperture in mm) meters, and focus tighter than 1-2mm is probably not useful due to issues of hole aspect ratio, so the range at which these weapons would retain full penetration is reasonable for their apparent roles (as assault rifle, SMG, pistol), though rather sharply capped as compared to conventional rifles (which, while not very effective beyond a few hundred meters, don't drop to irrelevance).

Luke Campbell

I was envisioning these as pulsed lasers. With a pulse, so long as the light is delivered into a smaller spot than the crater which is excavated, the crater will explode to full effect. Since higher energy pulses explode to give bigger craters, higher energy beams will have longer range for the same primary aperture.

So take the battle laser, with a 6 cm aperture and 200 J pulses (fired in bursts of 50 pulses spaced a few microseconds apart). At 200 J, the crater blown out of a good structural steel is about 6.5 mm. So suppose we want the beam to focus into a 6 mm spot. If the beam wavelength is around 1 micron, we get a range of about 275 meters. As the materials get less strong, the crater gets bigger and the range of the laser gets longer — about 470 meters in concrete, or about 940 meters for meat. Stronger materials need you to be closer — for sooper carbon nano stuff, you will want to be closer than about 140 meters.

Luke Campbell

      WINCHELL CHUNG Luke Campbell, a question if you please, sir!
     The classic Colt .45 automatic pistol has a classic name. "Colt" is the manufacturer, and .45 is the caliber of the weapon.
     In essence, the .45 is a crude measure of the destructive power of the weapon. Since both the mass of the bullet and the amount of gunpowder charge is roughly proportional to the damage energy inflicted on the target.
     So if I was to name the item below, what would it be?
     The manufacturer be something along the lines of "Campbell", but what about the weapon designation? Would it be "3 cm" (aperture), "4 μs" (pulse interval), or "3.2 kJ" (beam energy)? Or would there be another more logical specification number?

     BRIAN RENNINGER Super 8 sounds kind of deadly.

     JENNIFER LINSKY the Campbell collimator.

     MATTER BEAM Perhaps pulse energy with a pulse length descriptor? Like a Campbell 100 Short, for 100 joules over a typically short pulse length?

     JUAN OCHOA Gods I love you people.

     JASON FRITZ "In essence, the .45 is a crude measure of the destructive power of the weapon." Well, the designator ".45" was never meant to be indicative of the power of the weapon, but the caliber of the ammunition it fired.

     DAN THOMPSON I think it really needs a two-number designation because it's going to deliver an amount of energy over an amount of time. Saying it's a 10kilojoule is meaningless without knowing that if it's delivered over a nanosecond or over an hour. So, first number would be energy (assume kilojoules) and the second number would be the number of nanoseconds it's delivered over. Better weapons have big first numbers and small second numbers, so a 100@5 would be much better than a 50@12.

     WINCHELL CHUNG Dan Thompson, so it would be a Hundred-aught-Five ? {grin}

     ISAAC KUO I would think in terms of marketing, and the culture/society we're dealing with. Is this a civilian weapon? Is this a military weapon? Is it, like here currently in the USA, a situation where the military weapon has civilian versions, so the naming will more likely be dominated by the civilian naming?
     Is this just one weapon in a huge array of weapons supplied by this manufacturer? Or is it only one or two? If the latter, then the manufacturer's name will likely become the common name. Think Armalite, or Baretta, or whatever.
     Or depending on the circumstances, it's more likely a simple military designation that becomes the common name (like M2 or M60 or whatever)...

     JOHN REIHER I think before I, as a military commander, would field a laser weapon, I would want to know if the laser was capable of delivering 1100 joules at about 100m. That's the yield of a 7.62 round fired from a standard military assault rifle. 100 meters is the iron site engagement range for most military assault rifles.
     Now, if you're assuming that you're barrel sighting with a laser weapon, (And why not? You make your laser weapon the same as a SLR camera.), you'd have a greater range, but as person who used to shoot targets with a scope, it takes longer to sight in your target the farther away they are. So, I'd stay with the 100m range. That means for me to switch over to laser rifles, I'd have to be assured of two things: Rate of fire down range is at least the same, and the accuracy is comparable.
     If I can only get one of those, then it's worthless. A FN-SCAR has a ROF of 3 a second for a 3 round burst. So, if your laser assault rifle has a ROF of 1 a second, it's worthless for me. But you say, "But the accuracy is much better!"
     Yeah, but that's only important if every soldier is a crack marksman. But they are not. They jerk, they twitch, and at 200m, they'll miss their target. But a soldier with an ballistic assault rifle will get off a 3 round burst and one of those bullets have a good chance of hitting.
     Now, I'd use a laser rifle for snipers. There it will excel. No drop-off, no worrying about wind, and it delivers most of its energy on target. And it's absolutely silent. That's where I'd employ laser weapons.

     BRIAN RENNINGER Probably want to add a third parameter — some measure of divergence. So, energy/release time/divergence. Similar to a shot gun: shot size or type/dram equivalent of powder/and choke setting. Though, divergence, like choke, may be an adjustable setting.

     JOHN REIHER 30kj is about 3 Wetherby elephant rounds, .460 cal. Not bad. But, as Brian points out, what's the divergence on your pulse rifle at 100m? 200m? Would a light fog complete defeat your weapon? A mylar shield? The uniform is designed to reflect infrared light?

     ISAAC KUO I really don't think miitary users would care about beam energy — simply doesn't matter. There are too many other variables when it comes to actual effectiveness — which is what matters. What's the practical range? What sorts of targets are it effective against? That's what matters.
     As for an energy rating, there actually is a place where that number is useful, but it's on the other end of the equation — energy consumption. Today, we already give battery ratings in terms of how much energy they store. This gives us a useful standard for feeling how much battery life we've got.
     Energy consumption tells you how many shots your battery is worth. To put it mildly, your amount of "ammunition" is kind of a big deal to know.
     So, if you've got a pulsed laser rifle "in the 40 watt range", it's going to be talking about 40 watt consumption rather than 40 watt beam power.

     JOHN REIHER It's much like most modern assault weapons have fully automatic ROF that is a useless metric. The FN-SCAR has a FA ROF of 300 rounds a minute. With a 30 round magazine, that's only 5 seconds of wasting ammo.
     And that's the first thing you're taught in the military. "See that 'auto' setting? Never use it." You're trained to fire in bursts for a couple of reasons. A well placed 3rnd burst will have a good chance of hitting a target. Second, if you're standing there for 5 seconds spraying and praying, the sharpshooter on the other side can target you and take you out.

     TODD ZIRCHER Yeah, the Terminator already set the stage. From a marketing perspective, what would be the watts delivered with a single trigger pull ala what does a .45 deliver with a single round. Not sure what the numbers would look like but that is how I would SELL a zap gun.
     So a Campbell 45 would deliver 45 watts and things like ammo capacity, rate of fire, alternate firing modes, beam diameter and spread would all be on the text after you got the reader's attention.
     "(ed note: if my slide rule is not lying to me, 1000 pulses at 5 microseconds per pulse will take 0.005 seconds. 1000 joules in 0.005 seconds is equivalent to 200 kilowatts)"
     Okay, that's a Campbell 200k then. Maybe the Terminator dropped the 'k' like all the cool kids do.

     MATT WILSON I think Isaac is on the right track. The military will call it whatever version number it is (M4, M9, M16), and the consumer model will have either a neato descriptive name like the Wilson Lasers "Sharknado" personal defense face pulverizer or a more serious model number (Walther P99, Glock 17, etc). They'll do focus groups for the names and test for arousal. "Hmm when we said Sharknado the ambient room temp went up 2 degrees, looks like we have a winner."
     In terms of describing destructive power, I bet there will be a shorthand, or common outputs, because human beings are lazy af. Maybe there will be thread wars similar to 9mm vs. 45 about which combo is best. "Laserstatic shock, you morons! Beam aperture matters!"
     And of course the brochures will tell you that the lens on the Sharknado is coated with Focusbritetm for a 14% greater zapification, and there will be one of those comparison charts that show you how the Sharknado has all these extra features you won't find in other laser pistols, like rubberized grip and fresh pine scent.

     JOHN REIHER The Zzzapmatic 3000! Capable of delivering eleven hundred joules a second on target! 23 angstrom focusing reticle and inline targeting system! Only 23,099 CR! Get yours now!

     LUKE CAMPBELL In my Vergeworlds setting, that looks like it is in the Sòng family of weapons, fitting into the "heavy laser pistol" category. So call it the Sòng XL-P 238 "Durendal", in the standard 3-1.5 configuration (here, Sòng is the manufacturer, XL-P 238 is the model number, Durendal is what everyone calls it, and 3-1.5 designates a 3 cm aperture and a 1.5 kJ beam pulse. As everyone else is saying, there's a lot more detail that goes into a full description of the weapon's utility — beam duration, beam quality, firing latency, beam stabilization algorithms, durability, heat rejection, solenoid power storage, etcetera. But then, Colt .45 just tells you the projectile diameter, not its muzzle velocity, projectile length, projectile mass, action (single action revolver, unless you are talking about the Colt M1911 automatic pistol, which fires a different .45 caliber cartridge), ammunition capacity, weight, rifling twist, ergonomics, reliability, or the duration of the waiting period in the state you buy it in. And if you try to put the .45 ACP bullets for your Colt M1911 into your Colt Single Action Army revolver (the classic Colt .45 of the old west) you'll be in for a nasty shock).

     PETER KISNER 3.2 kilo Joule?
     Nah, man! Joules are that New World Order SI crap. Here in America we arm ourselves with the Campbell .76 μt (that's pronounced you-tee).
     The ol' Campbell 76!
     That's 760 nano-tons of TNT to protect your home and property in the hard fighting, freedom loving spirit of 1776. (well, 760 micro-tons of TNT, actually, but the idea is the important thing)

     JUAN OCHOA U niversal L aser W eapon P rofile a la Traveller?

     JOHN REIHER So, those weapons can be had for a... Sòng?

     LUKE CAMPBELL John Reiher, hah! Yeah. I remember thinking of the same pun when daydreaming about the really cute girl in my Judo class with the last name of Sòng. I totally didn't name one of the major electronics manufacturers in the Verge after her.
     Isaac Kuo, energy might not matter to the military grunt schlepping around one of these things, but bullet diameter probably doesn't either — and they still call cartridges things like 7.62mm NATO and 5.56mm NATO and such.
     In my Vergeworlds setting, an energy storage solenoid can store such a ridiculous amount of energy that ammunition capacity is not that much of a worry for lasers (typically, you would expect about 1000 shots per charge, and due to issues with dissipating the heat most lasers only shoot semi-automatic. So you are not likely to run out of energy during a firefight).

     JOHN REIHER So, what happens if someone manages to peg that solenoid with a more or less full charge?

     LUKE CAMPBELL John Reiher, at least it would be quick. If it is any consolation, if the pulse was a few centimeters off and drilled you through the torso instead you would be just as dead.
     It also helps that by their nature, the solenoids are very well armored. They need to withstand the field-current interaction that is constantly trying to burst them open. The current-carrying superconductor is actually just a fairly thin layer lining the empty central torroid where the field is contained. Everything else is a super-tough, super-strong backing of carbon nano-stuff that compresses the solenoid and keeps its insides on the inside. And of course engineers build in a satisfactory safety tolerance. So by the very nature of the way they work, solenoids can withstand quite a bit of abuse.
     But probably not a full powered pulse from a laser weapon.

     TOBIAS KLAUSMANN (BLACKBIRD) It's a laser, which today are put into classes that designate how dangerous they are to retinas, essentially.
     So it'd be a Campbell class 5 (or whatever, the class system would need to be made up going from LTL all the way to "melts people in 5µs" or whatever the pinnacle of photon delivery is).
     Note that even today, people don't say, for example "Glock .45", but rather "A Glock in .45", possibly adding if it's a full-frame pistol. The "Colt .45" works mostly because without further qualifiers, everybody assumes something 1911-patterned.
     With rifles, the variations are much wider, including barrel length, bullpup vs. traditional, control style (even though Ar15 is everywhere, it's not everything), and of course ammo: there are a lot more rifle cartridges (not just calibers!) that have sizable market share than there are handgun calibers in common use (basically, it's .45, 9x19 and .40S&W plus a few revolver cartridges and oddballs like 5.7x28).
     If you want to go the cartridge route for lasers, people would classify the weapons by their laser module and possibly wattage. From a narrative point of view, this gives variation for use cases: not all modules would be good for high-energy pulse fire, or would suck at sustained use (cooling etc).

     ISAAC KUO Luke Campbell, okay, but if we're assuming plausible near future technologies, the number of shots available from a lithium-ion battery is likely going to be in the single to double digits.

     BENJAMIN BAUGH Many gun names are abbreviations for some of its features or for terms of art used in its branding. Like in a H&K VP70 the VP stands for "Volkspistole" — people's pistol.
     So here, this might be a Campbell J32-P (Called Little Campy by fans) — a Campbell Arms 3.2J Pulsed weapon, series J.

     MICHAEL EARL The caliber designation we tend to use for firearms don't just tell you how much damage they do (although they do do that), it tells you what you need to reload it. I suspect portable laser weapons would be labelled by the output specification of the swappable power pack ("Campbell 30 Amp" or, yes, "plasma rifle in the 40 watt range") or maybe by the required external cooling for a man-portable crew served weapon equivalent to our current medium machine guns ("Campbell 10/15" for a heavy laser rifle requiring a cooling system that can dissipate 10Kw at 1500 Kelvin).

     STEPHEN WHITEHEAD You need a letter and a number. The letter has some relation to what it is or does, so it could be P for "pulsed laser". The number is non-specific but probably has some connection with a physical property, at least initially. It can be incremented arbitrarily for improved models, with a letter suffix for the major tweaks. It wants to be fairly short and snappy — decimal points or zeroes best avoided especially for military use. So I think this is a Campbell P32.

     JOHN POWELL Different manufacturers will have different naming conventions and a popular or novel weapon with an awkward designation will gain a nickname. A really popular brand may become a generic term for the class of weapon. “Blaster” could have been a manufacturer’s brand for hand held energy weapons.

     JOHN REIHER Hmm, "Blaster" might be considered to "kitschy". But then some marketing droid comes up with "Blazer" which keeps the blaster esthetic, but makes it sound more like a laser.

     JOHN POWELL Pictured in the original post is the classic iGun Sierra 3. Love the retro Late 20th Century look!

ISAAC KUO Luke Campbell: "Energy might not matter to the military grunt schlepping around one of these things, but bullet diameter probably doesn't either — and they still call cartridges things like 7.62mm NATO and 5.56mm NATO and such."     Reading this more did indeed matter. Remember, earlier military guns were muzzle loaders. So, bullet diameter alone determined what ammunition would fit in your musket/pistol/rifle.
     As cartridge ammunition was developed, cartridges were originally loaded in a way that legacy bullets would still be used when wrapped up into cartridges.
     Preloaded cartridges used diameter to describe them because that's what was already used.
     With modern cartridges, diameter is no longer entirely adequate. We've resorted to slightly lying about diameter in order to distinguish incompatibly shaped cartridges which happen to use the same diameter bullets (.357 Magnum vs .38 special for example). It's easier to develop new cartridges that use the same bullets and rifling diameters as already standard.
     The point is, it's not an illogical decision — it's something that was logical at the time.
     So, we need to think about the legacy of how things got to where they are at the time of the setting.
     With current technology, we have numerous incompatible lithium-ion battery packs for power tools. Are these the sorts of things that would be used for laser weapons?
     I'm guessing not. We may need huge backpacks for anything useful. In that case, a standard power cord connector might be what's relevant rather than a battery form factor that fits within a laser weapon itself...

     ROB CONLEY My day job is writing and maintaining software for the metal cutting machines my company manufactures. In the US but we say 1 1/4 inches and generally use inches for human scale measurements. The rest of the world use mils for millimeters.
     So I would call it the Campbell 60 mil. And note regardless of the name the technical reference will be using millimeters not centimeters.
     "The aperture is a 60 mil window protecting a 60 mill lens."

     JOHN REIHER Isaac Kuo, exactly, though the military would put a stop to multiple different connectors and power controllers. They would force an industry standard for power supplies so that the armorer doesn't have to stock 20 different power supplies and connectors for them.
     But milspec systems might get restricted to the military and the civilian market might have unique systems with controllers that only work with specific model lasers. Much like the printer ink market, after market or "generic" power systems would be available but would violate the warranty on your Camp0-32.
     And as man spreads out in system and in other star systems, local manufacturers might "adapt" big market systems for their homegrown weapons. So a Ceres Chungster 0-36 might use the same system used by the Campbell line of lasers, just with some minor modifications. Can you use a Chungster power supply on your Campy? Maybe... possibly...

     RAYMOND McVAY The Campbell Aught-three Peacekeeper

     KERR Well, we could use some regime of energies and average power output to roughly define the weapon. Similar to how you would differentiate a carbine and an SMG. The aperture size describes the physical "bore" of the laser and can be related to range and to some degree also damage. As for the ammunition, I think we can assume that those devices have some sort of integrated capacitor which feds into a quasi-CW laser that pumps the Q-switched cavities. So you could use an appropriately powerful battery as long as it fits (doesn't mean you would survive a fight by plugging your li-ion battery into the laser pistol).
     Cam-bell .30 ?

     ROB GARITTA I suggest the brand followed by mm dash output (kJ!). Like thirty aught six names and he diameter an the year of introduction only this tells you enough to stat it for a game. Ex: Campbell 30-3.5 thirty three point five or just thirty three five. As opposed to thirty five (a heavy weapon by output).

     MICHAEL EARL Ship-mounted weapons are of course a different animal, but for what it's worth: in the (relatively hard) 'Children of a Dead Earth' video game, laser designs being discussed are generally referred to by designer and power input requirement ("Apophis 100Mw", "jt Gigawatt"), or if you're really getting into the nitty gritty, by the diameter of beam and distance at the point where the laser intensity drops below a specific threshold:
     "What's the spot size on that JT one gigawatt anyway?"
     "6 meters at 3.5 Megameters."
     "!@#$. How many railgun drones are our carriers packing these days, exactly?"

From a thread on Google Plus (2018)

(If you have droplets of water/ oil / mud on the lens and your first pulse hits it could the resulting steam eventually degrade the lens?)

An interesting question. For the parameters I assumed for these devices, a single shot is about 5 kJ in 0.5 milliseconds, or 10 MW of power time averaged over the pulse. At the lens it is spread out over a 6 cm diameter spot (since the lens is 6 cm in diameter). Since 100 J distributed over a 6 cm spot is not likely to give an impulsive shock wave, I'll treat this as if a 10 MW beam was incident on the lens debris.

I turn to the calculator and look at what 10 MW in 6 cm will do to granite — assume a piece of dust is equivalent to a tiny granite fleck. I find that the vapor pressure is 242 kPa — a bit less than two and a half atmospheres. This is much less than the structural strength of any reasonable lens material, so the evaporating dust fleck will not blast a hole in the lens (material strength of strong refractory materials are measured in tens of GPa or more — hundreds of thousands or millions of atmospheres). The temperature is 2584 K. This will burn unprotected diamond, so we will have to assume that the surface of the lens is not diamond. Zirconia has a melting point of 2986 K, so we can make a thin film covering out of that, with diamond underneath (diamond has excellent thermal conductivity and transparency). Silicon carbide is another possibility for a lens coating. In the half a millisecond of laser irradiation, the dust will evaporate to a depth of 0.06 mm.

So what looks like will happen to a bit of dust on the lens is that a thin layer of the dust will be heated to vapor. The vapor will expand, acting like a rocket to launch the dust off the lens. With a proper selection of materials, the lens will be undamaged.

Repeating the calculation with perfectly absorbing water (a model for mud), I find a pressure of about 6 atmospheres (615 kPa), a temperature of 433 K (a bit over boiling), and vaporization to a depth of 0.6 mm. This comes nowhere near harming the lens, and blasts the water off the lens with a puff of steam. In practice, the water is likely to be mostly transparent, and might boil throughout its volume or even transmit the beam without significant heating for very pure water rather than having a bottom layer evaporating.

Oops — SiC also burns when it gets too hot. It looks like zirconia will need to be the lens coating material.

Or rather than zirconia, cubic boron nitride could be used as a coating, since it is just about as hard as diamond, has extraordinary chemical stability, thermal conductivity, and thermal stability. Maybe you could make the entire lens out of cubic boron nitride rather than diamond.

Luke Campbell

(ed note: in 2015 somebody asked Luke Campbell how far in the future such laser sidearms are.)

My best guess about the time span for pulsed lasers is maybe about thirty years, plus or minus fifty.

This would be for ship-board and vehicular weapons. Getting a laser into a rifle-sized package sounds like a much more challenging task.

Although over the last several decades laser power levels have been advancing faster than Moore's law, so who knows? Admittedly, that's for instantaneous power rather than time average power. And you would need to put a few kilojoules into a pulse train about a microsecond long, with individual pulses of tens of joules energy and nanoseconds duration. Modern pulse lasers that fit on a tabletop (as opposed to an ICF facility) are doing really good if they reach millijoules (1/1000th of a joule) in a nanosecond, in a package much larger than a rifle, so they've got a long ways to go.)

Luke Campbell (2015)

(ed note: in 2017 somebody asked me if the ejecta from a laser wound would appreciably thrust or tumble a target who was in free fall. I asked Dr. Campbell. TL;DR: nope.)

Luke Campbell

I'll work this out when I get a chance to go over my high energy laser absorption code. It should calculate the speed and mass of the ejecta as part of the intermediate calculations. I'll just have it print that out.

Incidentally, I find the lasers tend to work better with about 100 pulses than 1000.

The conceptual weapon fires over a one millisecond time period. That's roughly the period of oscillation of impulsive cavities in flesh (but a bit shorter, the cavities tend to collapse and oscillate with a period of several milliseconds), so a one millisecond beam could drill through a person without having the beam interrupted by the cavity produced by the violent vapor expansion collapsing back.

This one millisecond pulse is broken up into a number (about 100 or 1000) of individual "micropulses", each on the order of a nanosecond duration.

(Dr. Campbell returns from his calculations)

The easy one first. If you take a 1 MW beam and focus it to a 1 mm wide spot on a person for 1 millisecond, it is just about as effective at blasting out a hole on them as if you break the beam up into hundreds of nanosecond pulses (the armor penetration will not be as good, but still better than a bullet). My calculator tells us that the pressure of the laser-irradiated spot is 224 MPa. With a 1 mm diameter spot, this means the force is 176 Newtons. The beam lasts for 1 ms, but the hole it drills in meat is 71 cm deep — and most people are not that thick. Since you have constant drilling speed, and a typical cross section across the human body is 25 cm, you will be getting that force over about 1/3 of a millisecond. This gives an impulse of 0.06 N s. A 75 kg human would be sent moving at the blistering speed of 0.08 mm/s (about 2 minutes to move one centimeter). If you shot someone at a distance of 1 meter from their center of mass and were drilling the hole more-or-less perpendicular to the vector from their center of mass to the point of incidence, and assuming we can calculate the moment of inertia as if the person were a uniform rigid rod 1.6 meters long (for I = 16 kg m2), the target would be set rotating at a speed of about 0.004 radians per second (or about 1500 seconds for a full revolution). (so it would take 25 minutes for a full revolution. This is about twice as fast as the minute-hand on an analog clock for those of you old enough to have seen a non-digital clock)

Now consider breaking that 1 MW, 1 ms pulse up into 100 pulses of 1 ns duration and 10 J each, separated by 10 microseconds (for the same total pulse duration and beam energy). The pressure in the irradiated spot is 228 GPa so the force is 180 kN. Over 1 ns, that's an impulse of about 1.8×10-4 N s. It will take about 20 of these pulses to blast through your target, so the total momentum transferred is 0.0036 N s. So you would get roughly 1/15th the impulse, 1/15th the change in speed (0.005 mm/s, 33 minutes to move 1 cm), and 1/15th the rotation (2.7×10-4 radians per second, 22,500 seconds or 6.25 hours for a full revolution) as from a single pulse.

I suspect that the splatter of blood and guts will deliver significantly more momentum to your poor target than the evaporate, but that's well beyond the level of simple calculations.

Luke Miller

As you drill deeper, would you have less evaporate as more energy is transfered into surrounding tissues?

Luke Campbell

To some extent. Laser drilled holes tend to be limited to aspect ratios of 1:20 to 1:30 or less. In metal, the surface of the drill-hole tapers inward. This intercepts more and more of the beam. The losses are not as bad as it might seem at first, because the sides are still somewhat reflective and form a wave guide that funnels the beam to the end of the hole. Still, too deep of a hole can interfere with drilling even deeper.

In meat, it is not quite as clear what's going on. For obvious reasons, this is not something people nowadays have a lot of experience with. You have the evaporation of the meat producing a high vapor pressure, which expands out the surrounding meat to produce a big hole or cavity. The laser beam is much narrower than the cavity, so it might be able to just sail through and hit the back wall, producing even more high pressure vapor to dig out and deepen the cavity. Experiments might reveal complications to this model — if anyone wants to fund me to buy a megawatt laser and drill holes in slabs of meat, I'm listening.

Luke Campbell (2017)


Dr. Campbell's observation about how 5 μsec pulse rate is optimized for soft tissue but others are better for hard materials made me wonder about adjusting a blaster according to what material you are trying to shoot through.

Dr. Campbell figures that for most users it would be enough to have two preset modes: a button for "anti-personnel" beams and another button for "armor piercing" beams. He figures that the optimal beam characteristics to penetrate steel, bronze, stone, and advanced nanostructured carbon armor will not be much different. So alteration for the specific armor are probably not worth the trouble.

There is no doubt in my mind that Dr. Campbell is correct, but I also figure there will be fanatics who want to tweak every last bit of efficiency out of their weapon. The variables appear to be:

  • ΣE: Total energy in the bolt (pulse train emitted with each trigger pull) in joules = ΣP × Ep
  • Ep: Energy in one pulse, in joules = ΣE/ΣP
  • ΣP: Number of pulses = ΣE/Ep
  • Tp: Duration of pulse in seconds (probably a constant) = (ΣT/ΣP) - Td
  • Td: Time delay between pulses in seconds = (ΣT/ΣP) - Tp
  • ΣT: Total duration of the bolt ((Tp + Td) × ΣP)

(symbols suggested by Tobias Klausmann. Σ means "Summation" which is a fancy word for "total")

This would be for a customizable laser sidearm. Average users will use simpler guns with just a FLESH/ARMOR toggle. Stupider users would use even simpler guns hardwired for "anti-personnel" or "armor piercing".

So simplistically speaking each variable will have an up/down toggle control and an indicator readout. Since the variables are interconnected (like linked equations in a spreadsheet), altering one variable will also change some of the others. In fact there may be a way to reduced the number of toggle controls by exploiting the connectivity, but I haven't looked into that yet. Alternatively there may be a way of editing a "config file" for the weapon using a computer or smartphone, and uploading the config into the sidearm. Such a file could create new custom preset values, say a configuration prefectly optimized to penetrate the carapace of a Blortch Crab Soldier.

Dr. Campbell said:

     So we have two pulse durations here to worry about. The length of the entire pulse train (ΣT), and the length of the individual pulses in the train (Tp).

     For the individual pulses, pulse lengths in the several nanosecond range will probably be optimal. Make them too short and you start getting stimulated Raman scattering ruining your beam, and self-focusing causing filamentation. Make them too long and you don't get an adequate blast at the target. The lower the pulse energy, the shorter you will need your pulse to be, and the shorter it can be before it stops working. (translation: this value does not need to be tweaked, so there will be no control to change it)

     For the full pulse train, varying the length (ΣT) can have significant effects. The shorter the pulse train, the more the energy tends to "bunch up" before it penetrates very far, leading to a wider but shallower hole (he mentioned later that he means making the pulse train shorter by reducing the delay between pulses Td). This is particularly noticeable in soft materials, such as flesh. In the limit of an instantaneous pulse, you just get a surface explosion and a spherical cavity with little penetration. As the pulse train lengthens, it can bore deeper into the target resulting in higher penetration but a smaller wound channel. To penetrate armor, you will want as high of a penetration as you can get, which could result in significant over-penetration of the target (meaning the bolt will penetrate the target and still have enough power to wound or kill somebody standing behind). Making the pulse train shorter can lead to a beam that can still punch deeply enough to affect vital organs while leaving a wider wound channel. For beams with a long depth of focus, the shorter pulse train will present less danger to bystanders and equipment behind the target (although the depth of focus of most near-visible lasers will be short enough that this will not usually be of concern except when the target is nearly touching the bystander or equipment).

(ed note: I asked him a question about shortening the pulse train)

     I was initially thinking about altering the pulse delay (Td), but if you reduce the number of pulses (ΣP), but increase the energy per pulse (Ep) to compensate and keep them at the same delay between pulses, you could get a similar effect.

     It might help to simply consider smearing the entire pulse train into a single uniform pulse of about a millisecond long. When this hits meat, the meat will evaporate at a certain rate according to the pulse's power. This gives a certain amount of pressure and volume of evaporate which blows out a given sized hole in the meat, leaving room for the rest of the pulse to go through and continue blasting out the hole deeper in the meat. If you compress the pulse in time (seconds) (to 0.5 millisecond, say) while keeping the energy (joules) the same, the power goes up (joules/sec i.e., watts). This produces more pressure and makes the evaporate faster, so it blows out a bigger hole. But although the increased pressure helps the pulse burrow into the meat faster, it does not compensate for the reduced duration. With less time to dig the hole, the hole ends up being shallower but wider.

     Since the dynamic response time for meat is around a millisecond, these pulse trains with lots of smaller pulses spaced just a few microseconds apart get averaged together as far as meat is concerned and you end up with a situation similar to the single, millisecond-scale pulse.

Ray Beams

Ray beams are lasers that emit needle-thin beams that produce a white-hot plasma along their path and easily burn deep holes into their targets. Andre Norton called them "needlers."

The main difference between ray beams and blasters/heat-rays is that ray beams use vacuum frequencies. These are frequencies shorter than 200 nanometers: extreme-ultraviolet, x-rays, or gamma-rays. Note that another name for frequencies shorter than 10 nanometers is "nuclear radiation."

Blasters and heat-rays use non-vacuum frequencies, such as visible light or infrared. These frequencies freely pass through Terra's atmosphere, but have to burn through plasma (waste energy on boring a hole through the plasma so the rest of the beam can hit the target).

Vacuum frequencies are the opposite: they have to burn through atmosphere, but they sail through plasma with nary a problem. Which means vacuum frequencies do not need to resort to the blaster trick of pulsing the beam. But a vacuum frequency laser beam has to burn through all the atmosphere between the laser muzzle and the target before any of the (remaining) laser energy can start inflicting damage.

The main problem it is astonishingly challenging to make a laser that uses vacuum frequencies.

It is even more astonishingly challenging to make the weapon smaller than a self-propelled artillery vehicles.

Extreme Ultraviolet is incredibly difficult to work with. It pretty much tries to destroy any matter it hits. That's why they call them "vacuum frequencies", they work best in vacuum. This means you cannot use lenses to focus the beam. You cannot use windows to isolate the lasing element from the environment. Ordinary mirrors do not work (the UV burns holes in it), you have to use grazing incidence mirrors with special dielectric coating. And even then you are lucky to get 70% reflection efficiency.

Soft x-rays have all the above problems but worse. The mirrors have to be smooth down to 1/3 of a wavelength, which with soft x-rays means no mirror imperfections larger than 10 atoms high. And now you have a pumping problem.

You see, the laser generator has to be "pumped" with large amounts of the same frequency it will emit. This is not a problem with infrared, visible light, or ultraviolet. But there are not any good sources of large amounts of x-rays or gamma rays. At least short of a nuclear explosion, that is. The current best solution is free-electron lasers. However free-electron lasers have abysmal maximum efficiencies, and are generally hundreds of meters long.

Hard x-rays have wavelengths smaller than an atom, so mirrors will not work. All matter is rough on this scale. The proposed solution is to use x-ray crystal diffraction to make a difractive resonant cavity. Note that hard x-rays are ionizing radiation, so you are now inside the realm of nuclear radiation lasers.

Gamma-rays would make the most penetrating ray beams of all. Unfortunately there is no known way to focus gamma rays, which is a problem if you are trying to make a laser. And like hard x-rays there is a problem pumping the blasted thing. The only known way of making a gamma-ray laser is with an "Excalibur" style bomb-pumped laser. Which is problematic as a handgun.

Power Supply

The crummy efficiency of lasers make it clear that the laser's battery will be carrying plenty of juice. Anything carrying that much energy will be at least slightly unstable. In other words, it wouldn't take much to make a charged battery into a home-made bomb (which might come in handy if one suddenly needed a bomb.). You might have read news reports about laptop computers whose batteries suddenly burst into flame.

And don't even think about sticking a fork into the open contacts.

This has been observed somewhat tongue-in-cheek by John Routledge as Routledge's Law:


Any interesting battery material for a laser gun would be more usefully deployed as an explosive warhead.

John Routledge

He also notes the problem with ammunition cook off. If you are holding a fully-charged laser pistol, and some lucky enemy sniper manages to score a direct hit on the pistol's battery, it is going to be just too bad if the resulting explosion vaporizes you and all your friends within a large radius.

Assuming a worst case of 5 kilojoules per shot and a rechargeable magazine containing 50 shots, the magazine is packing 250 kilojoules. This is the equivalent of 250,000 * 2.7778×10-4 = 70 watt-hours or 250,000 / 4,500 = 55 grams of TNT (For comparison purposes, a standard 8 inch stick of dynamite is about 208 grams and hand grenades used by the US Army have explosive charges of 56 to 226 grams of TNT). At his specified energy density of 2.5 kilojoules per cubic centimeter, this would imply a magazine volume of 100 cm3. this is approximately the same volume as forty-two .45 caliber rounds.

You may remember that in Star Trek, phaser hand weapons could be set to explode like hand grenades, a "forced chamber explosion."

The above is a reasonble energy magazine. At the ludicrous end, in L. Neil Smith's BRIGHTSUIT MACBEAR, we find the five-megawatt fusion-powered pistol.


I make a point of noting — although mine are superconducting batteries — that the distinction between "battery" and "grenade" is essentially disabling the safety circuits that stop it from discharging Much Too Fast and causing a sudden, catastrophic, energy-dumping quench. But nevertheless, energy storage with that sort of energy density is just too useful not to use — so a lot of work has gone into very good, no-fail safety circuits.

(In ISS agent and special forces training, of course, they teach you how do to exactly this: Explosive Overclocking)

That said, they don't worry about it much for military applications, either, because you have to be a very good, very cocky sniper with an amazingly good gun to successfully hit a target that small in just the right way to break through the deliberately-hardened-against-this-scenario shell and fracture the loops.

Alistair Young (2016)

Strength in other divisions at Samsung helped offset the financial hit the company took in the third quarter as a result of its unprecedented Galaxy Note 7 recall. But if a new claim pans out and a “safe” Note 7 issued as a replacement did in fact catch fire aboard an airplane earlier this week, Samsung’s initial recall might just be the beginning.

As we know all too well at this point, a major manufacturing defect has completely spoiled Samsung’s Galaxy Note 7 launch over the past two months. The issue, which is believed to only have affected a small number of Note 7 devices, can cause the phone’s battery to overheat and explode. So far, Note 7 fires have injured people, destroyed cars and even burnt down one family’s house. Now, it’s time to get up-close and personal with an exploding Note 7 to see exactly what it looks like when Samsung’s flagship phablet explodes.

In a safe and controlled lab environment, the researchers applied pressure to the Galaxy Note 7’s battery. They continued to apply an increasing amount of pressure until finally, the phone burst into flames. While the test doesn’t simulate the exact conditions under which a defective Note 7 might combust, the result is the same: Smoke, then a huge ball of fire, then the charred remains of a one-beautiful smartphone.

Photos of the lab’s test, which were posted by The Telegraph, follow below. First, the phone begins to smoke:

Where there’s smoke, there’s fire…

Lots of fire…

And finally, the charred remains:

Again, this test was performed in a lab and outside pressure was applied to the battery. But unfortunately, this is also what happens when a defective Note 7 explodes on its own, and that’s why we recommend that no one should purchase a Galaxy Note 7 right now under any circumstances.



     Luke Campbell, Hi!
     I and some others were wondering on the ToughSF discord: What is the peak output of the 'blaster' designs you created a few years ago?
     You mention that the battle laser design produces '50 pulses of 200J spaced by 10 microseconds'. We guessed that Q-switching allowed for very high peak output, but we could not find details on the pulse duration.
     The reason why is because if the pulses were nanoseconds in length, like suggested by your RPG page, the peak output works out to gigawatts of power — we don't know of any energy storage system could deliver this in handheld devices, let alone handle it without superconductors.


     The intended pulse duration would be between 1 and 10 nanoseconds in length — the exact amount probably isn't all that important for the terminal effects, at that energy and duration you will get much of the pulse energy in the form of a blast. The advantage to slightly longer pulse lengths is to avoid atmospheric self-focusing.
     And yes, the peak power will be on the order of gigawatts. You don't need to supply gigawatt pulses of electricity, however. A few megawatts can serve to energize the lasing medium, storing up energy in the excited states of the material to be released in a nanosecond pulse when the lasing cavity is made resonating via the Q-switch mechanism.


     Hello! I am a content manager on MatterBeam's discord and I started the conversation because of the laser weapons ideas I occasionally mention. A XM-25 sized laser blaster using 20J pulses with a length of 10 nanoseconds was the reason. I thought the power of the lasing medium is equal to the pulse energy times the time between each pulse. For example one pulse every 40 microseconds leds to a pumping power of 500kW, is this the correct way to calculate it? Also I am interested how the lens/focusing mirror avoids LDT at those powers?


     There are two power levels you need to worry about, the time averaged power and the instantaneous power.

     The TIME AVERAGE POWER is the total length of the pulse train. For example, if you have a 1 millisecond long pulse train (consisting of, say, 100 pulses each separated by 10 microseconds), and each pulse has 10 joules, then the total pulse train energy is 1 kilojoule and the time averaged power is 1 kilojoule / 1 millisecond = 1 megawatt. This is the power than needs to be provided by your power supply, such as a capacitor or inductor (in addition to any inefficiencies in the system — if the laser is 50% efficient at turning electricity into light, then the power supply will need to provide 2 megawatts). The power supply provides this energy constantly over the millisecond of the pulse train — the lasing medium being energized up to its capacity over 10 microseconds and then emitting a 10 joule pulse, over and over for 100 times.

     The PEAK POWER, or INSTANTANEOUS POWER will be the energy per pulse divided by the pulse duration. So if each of those 10 joule pulses last 10 nanoseconds, the peak power is 10 joules / 10 nanoseconds = 1 gigawatt. (This is a bit of a simplification, since the pulse time profile is unlikely to be square, so the maximum peak energy is going to be somewhat bigger, but it gives an idea of the order of magnitude of the power.)

     The way to make the optics work is to use highly robust materials for your optics with very little absorption, and to spread the pulse out over a large area on your optics. Dielectric layer mirrors, for example, are on the order of 99.999% reflective, so a GW pulse with a total energy of 10 J will only have something like 10 kW and 100 uJ absorbed by the optics. If your optical focusing lens is, say, 5 cm across (for a total area of roughly 20 cm^2), it will be exposed to a thermal flux of 500 W/cm^2 and a thermal fluence of 5 uJ/cm^2. This is within the published limits for dielectric layer mirrors, although pushing close to the limits in terms of flux (typically a few tens of uJ/cm^2 and several tens to hundreds of W/cm^2).

(ed note: spread pulse out over larger area of optics so there are more square mm of lens or mirror surface. This means each square mm has to deal with a smaller fraction of the total laser energy. All the energy is eventually focused down to a tiny dot on the hapless target. This means the laser muzzle will be somewhat large, 5 cm diameter in the example.)

     If you are using a lens, use similar methods — a wide area lens made of a highly transparent highly refractory high bandgap material with high thermal conductivity (diamond, for example, would be ideal) would be able to handle the heat load.


     20J * 10μs = 2MW
     20J * 100 = 2kJ
     2kJ * 1ms = 2MW
Alright thank you.

     Do you think that using a small phased array makes sense? A 40mm wide lens emitting at 450nm requires 800 emitters to produce a steering angle of 1 mrad. Resulting in a steering distance of 1cm/10m. Vibrations from the user and the cooling system could throw the beam off the drilling spot and thereby decrease penetration. Or at least how I'd imagine it.

Luke Campbell

     A phased array certainly makes sense — if you have the tech for it. The ability to flick the beam well off-axis would be nice for any automatic targeting system.

     But if all you want is to suppress vibrations — we can do that already like we do with high end autostabilized cameras. You just need a moveable mirror in the beam path, with a fast response and feedback to adjust its tilt so as to counteract the jitter in the device. You will probably also want a deformable mirror in the beam path, in order to pre-focus the beam so that the fluctuations in atmospheric density that normally defocus the beam just act to refocus the beam to the diffraction limited spot at the target. This is called adaptive optics, and is used on modern astronomy telescopes and laser weapons. But it can also be done just using a phased array.


     You also mentioned that the exact length of the pulse duration isn't so important, could you explain why? Shorter pulses result in higher intensities and vapor pressures, increasing kinetic damage of the laser beams. Which can be 4x as penetrative than ideal case continuous wave beams.

Luke Campbell

     Once you get to nanosecond-scale beams, the beam is over before the material can repond to the additional energy just dumped into it. Before the material even has time to deform, all the energy of the beam is absorbed (or partially reflected) to create a thin layer of plasma at the surface. So the net result is that whether your beam is 1 ns or 10 ns long, you end up with the same physical condition — a layer of plasma of the same dimensions with the same energy. As this plasma explosively expands, it will gouge out the same sized crater.

     But there are other effects where the pulse length does matter. If you exceed a threshold power level, you can initiate catastrophic self-focusing where the beam's interactions with air (via the optical Kerr effect ) will result in the beam converging well before it is supposed to, possibly causing filamentation.
     In addition, lower power levels can also keep the beam below the critical power threshold for your optical elements in the beam, preventing damage to your lenses and mirrors.


     My worries regarding movement are not only from the laser weapon itself, but also from a moving target. A lateral movement of 5km/h could throw off the beam spot so much that penetration is cut in half or worse.
     Interesting, although this image seems to imply that pico/femtosecond pulses create major shockwaves in the target material.
     So where should I put my benchmark when creating a pulsed laser weapon? Your calculator indicates that ideal pulse length scales of intensity, with vapor pressures exceeding the cavity strength by over 200% being a mark of near ideal pulse length. And if that is true, would variable pulse length be possible by utilizing something like a "dynamic" q-switch?


     I figured that laser weaponry would get a fix on the rate of lateral displacement of whatever they were aimed at at the moment of firing. Then the autostabilization mechanism would instead track the target for the millisecond or so duration of the target. This would keep the beam focused on the same spot.
     Pico- and femtosecond duration laser pulses are weird. During the time of laser irradiation, they heat up only the electrons of the material, leading to a situation where the target material has two different temperatures - one for the electron system and one for the ions in the lattice. It is only after the laser is done that the hot electrons come into thermal equilibrium with the rest of the material. This tends to lead to very "clean" craters, with less roughness than from nanosecond pulses.Using picosecond or shorter pulses for weapons would be problematic — when each pulse has on the order of a joule of energy or more, the instantaneous power level would be so high it would be hard to avoid damaging the optics or producing a self-focused filamented beam (the later effect may or may not be bad — it would let you overcome depth of focus limitations, but would give away your position, would likely have less control over the beam propagation, and could significantly decrease the range).
     The duration of the pulse train should be around a millisecond or a few — much shorter than this and the tissue of the human body does not have time to respond and all you get is a shallow surface crater. For the individual pulses, around a nanosecond is probably the best compromise for putting enough power on the target but not so much power that you damage your weapon or have unwanted interactions with the air.


     I think we have the same communications problem again regarding pulses and pulsetrains, I am talking about the individual pulses not the pulse train as a whole. My question is if ideal laser pulse length depends on a certain "intensity threshold"


     For the individual pulses, I suspect that for pulse energies of several joules to several tens of joules, you will want nanosecond scale durations (for the reasons I outlined above) This will put you well above the threshold intensity for flashing a thin layer of the surface to plasma, having the plasma absorb the beam and become highly energized, and then having the energized plasma explode to create a crater.

From Google+ thread (1981)

“We know where we stand, then.” She popped the charge pack out of her weapon, placed it in sunlight. “That might pick up enough power for one or two shots before dark. Give me yours.”

AnyKaat’s weapon had power enough for three more shots. Just enough. “Somebody comes along, you don’t act like that won’t work. Point it at them and make them get down on their belly. Then stick them with this.” She gave AnyKaat the longest blade she had collected. “Don’t hesitate. We got no friends around here.”

From THE DRAGON NEVER SLEEPS by Glen Cook (1988)

Power Parameters

There are several ways to measure the power source of a laser weapon with respect to how big and how heavy it is. This is useful to know, because it helps you figure out how many shots the gun has in it. Unfortunately the units are confusing, and some times the same name is used for two different terms. And I am probably going to do a poor job of explaining. When you give up on me, skip to the next section.


This is the total amount of electricity or whatever in something (e.g., a battery or a laser bolt).

Energy is measured in Joules (J, refer to the Boom Table). Sometimes you find energy rated in kilowatt-hours, where 1 kW-h = 3,600,000 joules or 3.6 megajoules

It is a property that must be transferred to an object in order to perform "work", which in this case means "blasting a flaming hole into your opponent."


This is how fast you can extract energy from your battery or whatever. Or insert energy: you may have noticed that it irritatingly takes a few hours to charge up your smartphone battery, instead of charging up to full in a fraction of a section as we wish they would.

Power is measured in Joules Per Second (J/s), also known as Watts.

Remember how energy must be transferred to an object in order to perform work? Power measures how fast the energy is transferred, or "how many seconds does it take to drill a blazing laser hole in your opponent."

Example: Luke Campbell's battle laser has 10 kiloJoules in each laser bolt. Since the bolt is emitted over 0.0005 seconds that means the power output is 20 megawatts. THIS DOES NOT MEAN IT NEEDS A 20 MEGAWATT BATTERY, especially since watts is a unit of power but you are probably thinking about the battery energy rating in megawatt-hours. Since Luke's battle laser has batteries containing only 100 laser bolts worth of energy in them, the battery contains 0.28 kilowatt-hours (0.00028 megawat-hours or 1,000 kilojoules). It still has to be able to deliver its 1,000 kilojoules of energy at a rate of 20 megawatts. If the battery does not have that many watts, it can use the camera-strobe trick.

This is the power that has to be supplied by the laser's power source. For a blaster style laser bolt, this is the total energy in the bolt divided by the total duration of the bolt. For example, if you have a bolt which is a 1 millisecond long pulse train (consisting of, say, 100 pulses each separated by 10 microseconds), and each pulse has 10 joules, then the total pulse train energy is 1 kilojoule and the time averaged power is 1 kilojoule / 1 millisecond = 1 megawatt.
In a blaster, this is the energy in an individual pulse within a bolt, divided by an individual pulse duration. For example, using the bolt described above, if each of the 10 joule pulses lasts 10 nanoseconds, the the peak power is 10 joules / 10 nanoseconds = 1 gigawatt.

This is how much power is crammed into a gram of something, usually a battery. Each type of battery or other power source has a power-to-weight ratio rating. Given the ratio and the power requirement, you can calculate the weight of the power source. Conversely given the ratio and the maximum weight requirement, you can calculate the power contained.

Power-to-weight ratio is measured in Watts Per Kilogram (W/kg).

This is also called "specific power" or "power-to-mass ratio".

This is the inverse of Power-to-weight ratio, and is generally only used with vehicles. Not batteries. It is measured in Kilograms Per Watt. It is also called "power loading".

This is how much energy is crammed into a gram of something, usually a battery. If the power contained remains the same but the energy-to-weight ratio rises, the battery becomes lighter.

Each type of battery or other power source has a energy-to-weight ratio rating. Given the ratio and the energy requirement, you can calculate the weight of the power source. Conversely given the ratio and the maximum weight requirement, you can calculate the energy contained.

Energy-to-weight ratio is measured in Joules Per Kilogram (J/kg). Occasionally you'll see it measured in Watt-Hours Per Kilogram (Wh/kg), where 1 watt-hour equals 3600 joules. Of course 1 watt-second equals 1 joule.

This is also called "specific energy" or "energy-to-mass ratio".


This is how much energy is crammed into a volume of space of something, usually a battery. If the power contained remains the same but the energy density rises, the battery becomes smaller.

Each type of battery or other power source has a energy density rating. Given the ratio and the energy requirement, you can calculate the volume of the power source. Conversely given the ratio and the maximum volume requirement, you can calculate the energy contained.

Energy density is measured in Joules Per Cubic Meter (J/m3).

For purposes of comparision a conventional .45 caliber cartridge for a slugthrower has a volume of approximately 2.4×10-6 cubic meters. If the volume of a battery capable of powering one laser bolt is larger, the slugthrower is more efficient.

Yes, the term "energy density" was used in the section on heat rays with respect to how many joules per square centimeter of skin area was inflicted. This is the wrong term to use, but I am unsure what the right one is.

PWR = power-to-weight ratio of power source (W/kg)
WPR = energy-to-weight ratio of power source (J/kg)
DT = time to totally discharge all the energy (sec)

BM = (LE * LPS) / PWR
PWR = power-to-weight ratio of power source (W/kg)
LE = energy in one laser bolt (J)
LPS = laser bolts per second
BM = battery mass (kg)

Camera Strobe Whine

Note that batteries generally have pretty good energy density and energy-to-weight ratios, but lousy power-to-weight ratios. They contain lots of energy (high joules), but it trickles out real slow (low wattage).

Capacitors are the opposite, with lousy energy density and energy-to-weight ratios, but pretty good power-to-weight ratio. They do not contain lots of energy (low joules), but what they have can be spat out in a fraction of a second (high wattage).

To try and get the best of both worlds, they engineer things so large batteries are feeding a capacitor, and the capacitor feeds the laser or whatever.

You've probably seen this in a camera strobe. It flashes, then you have to wait for the "charged" light to come on before the strobe will flash again. The energy in the capacitor makes the strobe flash, then the delay comes from the battery slowly recharging the empty capacitor. This is because the camera strobe flash tube demands lots of watts.

Power Sources

Dr. Schilling assumes that in the near future rechargable batteries will reach an energy density of 2.5 kilojoules per cubic centimeter (2.5×109 J/m3). James Borham says that currently available lithium-polymer rechargable batteries have an energy density of 1.08 kilojoules per cubic centimeter (1.08×109 J/m3).

Anthony Jackson says ultracapacitors may reach energy-to-weight ratios of 100 J/g (1×105 J/kg).

Asphalt-lithium batteries may charge 20 times faster than conventional lithium ion batteries:

  • Energy-to-weight ratio: 3.4×106 J/kg
  • Energy Density: ~8.5×109 J/m3
  • Power-to weight ratio: 1,322 W/kg

Asphalt helps lithium batteries charge faster

Winchell Chung

Are they near 2.5 kilojoules per cubic centimeter? The article says 943 watt-hours per kilogram, but I am not sure what the density of the battery material is.

Luke Campbell

Winchell Chung, with the given information, the specific energy is about 3.4 kJ/g. Li-ion batteries are about 2.5 g/cm^3. Assuming this new electrode doesn't significantly change the density, we get something like 8.5 kJ/cm^3.

Winchell Chung

     Luke Campbell, thanks!
     I had calculated that a .45 caliber cartridge is about 11.43 mm x 23 mm, which gives it a volume of about 2.4 cubic centimeters.
     At a rechargeable 2.5 kj/cm^3 this means a battery the size of a .45 round would hold a good 6 kilojoules, enough for an extra-strength laser bolt.
     So this new stuff allows a laser firearm to have a better ammo density than a slugthrower weapon.

Luke Campbell

Winchell Chung, but note that with the listed specific power of 1.322 kW/kg, to get your 6 kJ laser to shoot even one time per second you will need a 4.5 kg battery. So either we need further improvements in specific power, or use the battery to charge up a supercapacitor that will allow, say, 10 rapid-fire shots and that can be continually recharged at a slower rate by the battery.

BM = (LE * LPS) / PWR
PWR = power-to-weight ratio of power source (W/kg)
LE = energy in one laser bolt (J)
LPS = laser bolts per second
BM = battery mass (kg)

BM = (LE * LPS) / PWR
BM = (6,000 * 1.0) / 1,322
BM = 6,000 / 1,322
BM = 4.5 kg

You'll also need a power source. Three approaches come to mind, two of which are pretty sure things. Burning a liquid propellant in a pulsed MHD generator or flux compression generator can be done now, and there are thermal primary (i.e. non rechargeable) batteries that are pretty close to what would be needed. Unfortunately, both of these involve high operating temperatures and expendable power sources.

Advanced bipolar designs of conventional secondary batteries might be up to the task, and have the advantage of being fully rechargeable. Besides, it is rather humorous to consider that a 21st-century laser weapon might really be powered by a lead-acid or NiCad battery.

I'll assume non-rechargeable systems at an energy density of 2.5 kilojoules per cubic centimeter, which is quite plausible. You might consider a rechargeable battery pack as an option, with half the capacity of the non-rechargeables.

Dr. Schilling

It turns out that the future is already here. Lithium-polymer cells are rechargeable, and have an energy density of 1.08 kJ/cm3. This is just shy of half of Dr. Schilling's assumed energy density.

As for nonrechargable batteries, check out the various molten salt batteries. They're stored as a solid, so they can be stored 'charged' virtually forever. As soon as you bring them up to operating temperature (400 C or more), and as long as you keep them there, you have an incredibly high output battery. The military has used them like this for a very long time, and most current research is focused on making them rechargeable. I can't find any hard numbers on them (apparently the energy density varies widely), but it's clear that they can have very high energy density.

(Ed. Note: for a list of energy densities of various storage devices, refer to the Wikipedia article)

James Borham

Either way, the energy will have to be stored in and dumped from a capacitor or (if the switching problem is solved) inductor to meet the peak power requirement. Electrochemical double-layer capacitors ought to do the job if nothing else is available.

(Ed. Note: using a capacitor will make the laser operate in a similar manner to a camera strobe. You fire, then you have to wait for the little "charged" light to come on before you can fire the next shot.)

Dr. Schilling

If you can combine a chemically fueled laser with the type of pulse behavior needed for optimal armor penetration (a rather formidable challenge), a 'laser rifle' might not be too bad; under ideal circumstances a 10 kilojoule laser might be similar in lethality to a rifle, and could even have fuel requirements on a par with the ammunition weight of a rifle. Of course, this requires a very narrow focus beam (a couple millimeters wide) and you'll be limited to optical or near-IR. If we assume a helium-neon laser (634 nm) a 10 cm mirror would have a beam divergence of 15 microradians, giving a useful range of 100 meters or so (3mm spot).

So...this requires massive tech inventions and an expensive, probably delicate weapon to reach the performance of a rifle. This is not exactly worthwhile.

Efficient ultracapacitors might allow around 100J/g, which in combination with an excimiter laser (and probably a fuel cell for recharge) might be enough for a decent sniper weapon and could give a quite large number of shots on a fuel tank, though the number of shots at one time would be quite limited.

On the severe handwavium side, there's gamma-ray lasers powered by nuclei in metastable states. In this case, the energy density is immense (1.2 GJ/g for Hf-178m2, for example) and diffraction limits are unlikely to be relevant (a 1mm diffraction-limited lens could project a constant 1mm beam for 1,000 km or so). However, the technical problems are, to say the least, formidable, and even if resolved, the 'fuel' is highly radioactive; simply avoiding killing the user would require large amounts of shielding.

(ed note: the handwavium Hf-178m2 is the basis for the infamous Hafnium bomb. Yes, it exists. Yes, it stores incredible amounts of energy in a very tiny package. No, we have not yet figured out how to increase the power output to better than half of the energy discharged every 31 years.)

Anthony Jackson

(ed note: Noted science fiction author Charles Stross has this deliciously biting analysis of a ridiculous proposed laser weapon called the Stavatti TIS-1 Gasdynamic Laser Infantry Rifle)

The laser itself looks pretty reasonable, in an if-we're-talking-about-laser-weapons way ("laser" and "weapon" belonging in the same sentence in the same way as "automobile" and "rubber-band powered"), but the power supply is what makes this one special. In search of the ultimate in infantry-portable enemy-slaying goodness, Stavatti have one-upped all previous attempts by proposing to use a radioisotope generator containing 750 grams of Polonium-210. This would, of course, provide the necessary 100 kilowatts to power the man-portable death ray. It would also provide 125 petaBecquerels of radiation (as compared with the 100 pB of Cesium-137 spewed out by the B reactor at Chernobyl), and the need to pressurize it to 4000psi leads me to agree with my military informant's summary that "it might actually achieve the near-impossible feat of making Project PLUTO look environmentally benign by comparison."

I will also confess that my suspension of disbelief took a slight knock when I got to the bit about the TIS-1 also sporting a bayonet lug.

Anyway, I'd just like to say that I fervently hope the Pentagon's planning and procurement folks give this proposal the attention it undoubtedly deserves. As Polonium-210 is accounted for (when you can buy it) at a market price of roughly $12 million per gram, this weapon system will cost roughly $54Bn per rifle per year to run — the US Army could afford almost an entire squad, and thus might have to scale back their other projects accordingly.

(PS: 100 kilowatts is, in automobile terms, about 130 horsepower. So if you were to ditch the Dr Strangelove power supply the gadget could plausibly be mounted on a HMMV or Land Rover. But I find that idea somewhat disappointing ... and anyway, what would be the point of sticking a bayonet on a vehicle-mounted laser cannon?)

blog post by Charles Stross

There was discussion about ultracapacitors:

Apparently ultracapacitors are approaching 50% of the energy capacity of a lithium ion battery. Boost that over 100% and it would make a nifty power source for a man-portable laser weapon.

Winchell Chung

It looks to me like they expect 25% to 50% of the energy of a Li-ion battery. They still haven't made a prototype yet. It is exciting work, and I hope they succeed.

Luke Campbell

Hm. 50% would be 80 Wh/kg (288 kJ/kg). This is approximately 7% of the energy density of a typical chemical propellant and 0.6% of the energy density of gasoline. Incidentally, EEstor is claiming 1330 Wh/kg, but I'm not convinced that I believe them.

Note that thin film lithium and lithium-ion batteries have already pushed significantly beyond the capacity of lithium-ion. For current (if non-commercial) versions, I'm seeing numbers of around 250 Wh/kg and 2500W/kg, which is a bit low power density for a shot from an energy weapon. Theoretical potential is substantially higher.

For amusement: 2nd generation batteries in Ken Burnside's Attack Vector: Tactical game hold 2 gigajoules in a 25 ton structure, which works out to 80 kJ/kg or 22 Wh/kg, and can discharge in 16 seconds (or possibly less), which works out to 5 kW/kg. However, I'm pretty sure that a 1 hullspace component that can provide 1 energy point per game-turn segment for 20 segments (thin-film Li-ion with no tech improvements other than scaling and commercialization) would be gamebreaking. For that matter, 7th gen batteries (extrapolating from high end ultracapacitors) would rather distort the game as well.

Anthony Jackson

The thin film stuff should suffice for electrically powered projectile weapons, if you carried a backpack of batteries. If you figure a modern assault rifle packs something like a 1.5 kJ punch, and if you can get ~50% electrical ⇒ mechanical efficiency, and you want to be able to autofire at 10 round/s, you'll draw 30 kW. This is about a 15 kg pack for modern lithium batteries, 12 kg for your thin film varieties.

On the other hand, you could fire off many hundreds of shots if you had enough bullets. If you limit your fire to 3-round bursts, you could cut the power draw perhaps in half (depending on how fast our soldiers pull the trigger), and thus will only have to schlep around half as much weight. Needless to say, the batteries will be used to charge up a capacitor for the intermittent high power pulse used to launch the projectile.

Near future heat-ray style lasers are expected to be practical weapons at about 100 kW. This would require a 40 kg pack using the thin film batteries, but would give you 6 minutes of continuous lasing. Note that 100 kW is for use against rockets and thin skinned aircraft, it might or might not be useful against humans!

If, as I suspect, pulsed lasers are more efficient at causing death and destruction, you could get by with smaller power packs.

In my pet future setting, admittedly optimistic "battle lasers" put out lethal 5 kJ beams at full power, and draw 10 kJ. They can sustain 2 shots/second if you want to avoid heat buildup, but can be fired more rapidly for short periods if they have the electrical power available.

Lower power beams allow significantly higher rates of fire, although they are not too good against foes with armor. Something like could use an 8 kg pack for 2 full power shots/second if using the thin film lithium batteries, and would give you 720 shots. Combine this with something like a 1 kg ultracapcitor for rapid fire of a limited number of shots when you need them. The ultracapcitor recharges from the battery pack when you are hiding behind cover, switching between targets, crawling through the mud, or whatever else you are doing to avoid being shot.

(For what its worth, my setting uses "fast discharge power packs," roughly modeled on ultracapacitors, with specific energies of 200 kJ/kg and specific powers of 40 kW/kg. There are also "high capacity power packs" with three times the specific energy but one third the specific power if you want to tote around a heavy pack that gives you lots of shots, as well as various batteries that give even higher specific energies but even lower specific powers.)

Luke Campbell

Luke Campbell

Here's some artwork of mine on this issue

Isaac Kuo

That looks awesome! One minor idea—I notice that the layout is similar to a modern automatic rifle with the "barrel" lined up with the butt stock. This makes sense for modern automatic weapons because it minimizes muzzle rise due to recoil. Of course, a laser weapon has no inherent recoil.

Having the butt stock below the line of fire allows someone firing from a prone position from behind cover to have a lower profile. That's why single shot rifles had a downward sloping stock.

Similarly, having a large box magazine stuck to the bottom of a weapon forces the user to have a higher profile in a prone position. This is why some guns had magazines off to the side, despite the balance issues and the annoying carrying ergonomics.

Luke Campbell

Having the butt stock below the line of fire allows someone firing from a prone position from behind cover to have a lower profile. That's why single shot rifles had a downward sloping stock.

That's a good idea. I'll keep it in mind for my next model.

Similarly, having a large box magazine stuck to the bottom of a weapon forces the user to have a higher profile in a prone position. This is why some guns had magazines off to the side, despite the balance issues and the annoying carrying ergonomics.

This makes me wonder where to put it. I suppose you could put it on the side, since a battery or ultracapacitor doesn't actually have to stick out like a cartridge feeding magazine. Putting the power pack forward of the grip seems like it would make it easier to switch an exhausted pack for a fresh one, probably on the side of the off hand. On the other hand, if you have a power cable from a larger battery or capacitor pack worn on the belt or as a backpack, a connection near the butt end would seem to present fewer problems with the cable snagging on things.

Christopher Thrash

This makes me wonder where to put it.

Put it on top of the frame in back, behind the optics and above the buttstock. Make it as long as possible while still able to fit into a vest pouch, and flat enough to not obscure the sighting mechanism. Think of a handier version of the G11 magazine, mounting in back rather than in front.

Isaac Kuo

This makes me wonder where to put it.

I'm sorry, I actually don't think your energy pack sticks out very far. I was thinking of the problems with normal rifle/submachinegun box magazines. Box magazines full of rifle/pistol rounds are long and thin due to the way the feed mechanism works. Besides the double stack of rounds, there's a need for a rather bulky magazine follower for reliable feeding.

Your energy pack doesn't need to have such a shape, so it doesn't need to stick out so much. The amount your design sticks out is not a problem. You could lower the profile a little by placing the energy packs to the sides of the fore-end, but this is of dubious benefit.

Speaking of which, having two energy packs means that you can reload while always having some "rounds in the chamber". Instead of having a vulnerable period when you have no firepower, you always have one energy pack available.

The energy pack could be the butt stock itself.

Business end of a laser pistol? from sfconsim-l (2007)

      So here's a new energy development:

     The article mostly talks about the way these new supercapacitors are transparent and flexible. That's all very nice, but what really caught my eye was the specific capacitance: 178 F/g. Most supercapacitors can carry a maximum potential of around 2.5 to 2.7 V. So, if these things could be produced in bulk you could get energy storage of around 167 W-h/kg. This is well in excess of what you can get with lead-acid batteries (30 to 40 W-h/kg), and in the range of the specific energy of lithium ion batteries (100 to 265 W-h/kg).

     The energy of a Li-ion battery but with the ability to charge and discharge within seconds could be a real game changer. Your electric car could be fully recharged in less than a minute rather than overnight, significantly decreasing the range anxiety that is currently hampering electric car sales. Your laptops and smartphones could be instantly recharged at any outlet (using a rectifier, of course).

     And for all my sci-fi loving friends out there, you could get hundreds of shots out of your laser blaster gun before needing to recharge.

From a thread on Google+ by Luke Campbell (2016)

Modular Power

In science fiction an uncommon power supply is a modular supply. This is where you can add a variable number of power supply units to your weapon as if they were a stack of Lego bricks.

Ian Borchardt says the proper term for this capability is "upgradable". My personal favorite term is "stacked". (In some role-playing games a player's die rolls or characteristics are subject to modifiers, for example a magic sword that adds +5 to the player's strength or doubles endurance. If several modifers can be applied one after another, the terminology is that the modifiers can "stack." If you've never played an RPG then the preceeding sentences were total gibberish.)

The example of a modular power weapon that comes to mind is the good old Phaser from Star Trek.

A type 1 phaser is unit about the size of a bar of soap, and functions like derringer-sized directed energy weapon. A low-powered low-ammo discreet easily-concealable weapon. The Trek writers bible says a type 1 is something the crew would carry on a diplomatic mission to a friendly planet, where you didn't want to be obnoxiously packing heat but not totally defenseless either. Something that a stereotypical woman from a 1950s pulp detective story would tuck into their garter belt, handwarming muff, or purse. In Star Trek the type 1 phaser would be carried in the small of the back near the kidney concealed under the shirt, clinging to the pants by virtue of the "magnatomic adhesion area" (high-tech velcro). Type 1 phasers are worn right next to the communicator.

Snap the type 1 phaser into the larger power pack and it becomes a type 2, a phaser pistol. A handgun-sized directed energy weapon. Something a policeman or a military officer would carry as a service pistol. Or the equivalent of a frontier cowboy's six-shooter.

The Star Trek original series did not take it to the next logical step. Instead it made an outlandish phaser rifle that had no kindred spirit with the phaser pistol, and which was used for only one episode. A pity.

However, in the cancelled Star Trek II project they would do the logical thing and have the type 2 phaser pistol snap into a shoulder stock with a larger power pack to make a type 3, a phaser rifle. A long-gun-size directed energy weapon. Something a military soldier would carry.

The stacking phaser is a limited case of the "modular weapon" concept.


PHASER I: features fully self contained, operable components with a touch actuated lighted settings bar and side-mounted trigger. Batteries included (re-chargeable). Nose key lights function with trigger for easy optical matting of phaser beam. Features different color for each energy setting, plus on/off button for total shutdown.

Energy indicator bar colors: (front to back) Green: stun (neural effect), Red: kill (neural effect), Yellow: heat (molecular movement), Blue/White: disintegrate (molecular disruption)

Special feature: overload. simultaneous depression of all four settings buttons will arm the phaser for explosive overload (grenade effect). All four color bars flash warning until canceled with off button.

(ed note: the prop designers also added a row of beam emitters, so the weapon could be fired as a fan beam)

PHASER II: features easy interlocking with phaser one. Nose key lights now function with hand trigger. Features top inserted dilithium crystal power booster (pulsating light). Perfectly balanced, phaser two will stand up on any flat surface without support. Features overall cool silver/blue coloration. Exact size of Colt .45.

PHASER III: features easy interlocking with phaser two. Grip and operation remain the same. Connects to handle and undercarriage — drape-fit over forearm. Arm features booster packs (lighted). Overall shape reminiscent of old-style rifle stock.

External Power

Before laser bullets are developed, you might find laser pistols with separate power sources. A large battery strapped somewhere on your body, connected to the laser pistol or rifle with a power cable.

In the role playing game Traveller, laser carbines are powered by a large battery worn in a back pack. In the Barbarella comic, deflagrating guns have their battery strapped to the upper leg. In William Tedford's Silent Galaxy AKA Battlefields of Silence, the hand laser's battery pack is strapped around the wrist.

Gene Roddenberry's original conception of the Star Trek phasers had a connection between the guns and the "power belt." He visualized the belt looking something like a waist-type life preserver, having individual power units, three inches by six inches. The units can be replaced, just as bullets in a gun can be replaced

There was an amusing scene in a remarkably bad '50s movie called Teenagers from Outer Space. The hero unfortunately broke the power pack on his focused disintegrator ray. He manages to cobble together a solution just in time to save the day. He attaches a cable from a nearby high-tension power line, and convinces the power plant to shove the generator output up to maximum!


“Whichever way we look there are too many ‘ifs’ and ‘buts’ to suit me,” Kinnison summed up the situation finally. “If we can find them, and if we can get up close to them without losing our minds to them, we could clean them out if we had some power in our accumulators (fancy word for "battery"). So I’d say the first thing for us to do is to get our batteries charged. We saw some cities from the air, and cities always have power. Lead us to power, Worsel—almost any kind of power—and we’ll soon have it in our guns.”

“No danger of that,” replied the Velantian. “There are no windows in any of these rooms, no light can be seen from outside. This is the control room of the city’s power plant. If you can convert any of this power to your uses, help yourselves to it. In this building is also a Delgonian arsenal. Whether or not anything in it can be of service to you is of course for you to say. I am now at your disposal.”

Kinnison had been studying the panels and instruments. Now he and vanBuskirk tore open their armor—they had already learned that the atmosphere of Delgon, while not as wholesome for them as that in their suits, would for a time at least support human life—and wrought diligently with pliers, screwdrivers, and other tools of the electrician. Soon their exhausted batteries were upon the floor beneath the instrument panel, absorbing greedily the electrical fluid from the bus-bars of the Delgonians.

“Now, while they’re getting filled up, let’s see what these people use for guns. Lead on, Worsel!”

With Worsel in the lead, the three interlopers hastened along a corridor, past branching and intersecting hallways, to a distant wing of the structure. There, it was evident, manufacturing of weapons was carried on, but a quick study of the queer-looking devices and mechanisms upon the benches and inside the storage racks lining the walls convinced Kinnison that the room could yield them nothing of permanent benefit. There were high-powered beam-projectors, it was true, but they were so heavy that they were not even semi-portable. There were also hand weapons of various peculiar patterns, but without exception they were ridiculously inferior to the DeLameters of the Patrol in every respect of power, range, controllability, and storage capacity. Nevertheless, after testing them out sufficiently to make certain of the above findings, he selected an armful of the most powerful models and turned to his companions.

“Let’s go back to the power room,” he urged. “I’m nervous as a cat. I feel stark naked without my batteries, and if anyone should happen to drop in there and do away with them, we’d be sunk without a trace.”

Loaded down with Delgonian weapons they hurried back the way they had come. Much to Kinnison’s relief he found that his forebodings had been groundless, the batteries were still there, still absorbing myriawatt-hour after myriawatt-hour ("myria" is an obsolete metric term for 104 or ten-thousand) from the Delgonian generators. Staring fixedly at the innocuous-looking containers, he frowned in thought.

“Better we insulate those leads a little heavier and put the cans back in our armor,” he suggested finally. “They’ll charge just as well in place, and it doesn’t stand to reason that this drain of power can go on for the rest of the night without somebody noticing it. And when that happens those Overlords are bound to take plenty of steps—none of which we have any idea what are going to be.”

“You must have power enough now so that we can all fly away from any possible trouble,” Worsel suggested.

“But that’s just exactly what we’re not going to do!” Kinnison declared, with finality. “Now that we’ve found a good charger, we aren’t going to leave it until our accumulators are chock-a-block. It’s coming in faster than full draft will take it out, and we’re going to get a full charge if we have to stand off all the vermin of Delgon to do it.”

Far longer than Kinnison had thought possible they were unmolested, but finally a couple of Delgonian engineers came to investigate the unprecedented shortage in the output of their completely automatic generators. At the entrance they were stopped, for no ordinary tools could force the barricade vanBuskirk had erected behind that portal. With leveled weapons the Patrolmen stood, awaiting the expected attack, but none developed. Hour by hour the long night wore away, uneventfully. At daybreak, however, a storming party appeared and massive battering rams were brought into play.

As the dull, heavy concussions reverberated throughout the building the Patrolmen—each picked up two of the weapons piled before them and Kinnison addressed the Velantian.

“Drag a couple of those metal benches across that corner and coil up behind them,” he directed. “They’ll be enough to ground any stray charges—if they can’t see you they won’t know you’re here, so probably nothing much will come your way direct.”

The Velantian demurred, declaring that he would not hide while his two companions were fighting his battle, but Kinnison silenced him fiercely.

“Don’t be a fool!” the Lensman snapped. “One of these beams would fry you to a crisp in ten seconds, but the defensive fields (they got anti-raygun force fields) of our armor could neutralize a thousand of them from now on. Do as I say, and do it quick, or I’ll shock you unconscious and toss you in there myself!”

Realizing that Kinnison meant exactly what he said, and knowing that, unarmored as he was, he was utterly unable to resist either the Tellurian (obsolete term for "Terran") or their common foe, Worsel unwillingly erected his metallic barrier and coiled his sinuous length behind it. He hid himself just in time.

The outer barricade had fallen, and now a wave of reptilian forms flooded into the control room. Nor was this any ordinary investigation. The Overlords had studied the situation from afar, and this wave was one of heavily-armed—for Delgon—soldiery. On they came, projectors fiercely aflame, confident in their belief that nothing could stand before their blasts. But how wrong they were! The two repulsively erect bipeds before them neither burned nor fell. Beams, no matter how powerful, did not reach them at all, but spent themselves in crackingly incandescent fury, inches from their marks. Nor were these outlandish beings inoffensive. Utterly careless of the service-life of the pitifully weak Delgonian projectors, they were using them at maximum drain and at extreme aperture—and in the resultant beams the Delgonian soldier-slaves fell in scorched and smoking heaps. On came reserves, platoon after platoon, only and continuously to meet the same fate, for as soon as one projector weakened the invincibly armored man would toss it aside and pick up another. But finally the last commandeered weapon was exhausted and the beleaguered pair brought their own DeLameters—the most powerful portable weapons known to the military scientists of the Galactic Patrol—into play.

And what a difference! In those beams the attacking reptiles did not smoke or burn. They. simply vanished in a blaze of flaming light, as did also the nearby walls and a good share of the building beyond! The Delgonian hordes having disappeared, vanBuskirk shut off his projector. Kinnison, however, left his on, angling its beam sharply upward, blasting into fiery vapor the ceiling and roof over their heads, remarking:

“While we’re at it we might as well fix things, so that we can make a quick get-away if we want to.”

Then they waited. Waited, watching the needles of their meters creep ever closer to the “full-charge” marks, waited while, as they suspected, the distant, cowardly-hiding Overlords planned some other, more promising line of physical attack.

Nor was it long in developing. Another small army appeared, armored this time, or, more accurately, advancing behind metallic shields. Knowing what to expect, Kinnison was not surprised when the beam of his DeLameter not only failed to pierce one of those shields, but did not in any way impede the progress of the Delgonian column.

“Well, were all done here, anyway, as far as I’m concerned,” Kinnison grinned at the Dutchman as he spoke. “My cans’ve been showing full back pressure for the last two minutes. How about yours?”

“Same here,” vanBuskirk reported, and the two leaped lightly into the Velantian’s refuge. Then, inertialess all, the three shot into the air at such a pace that to the slow senses of the Delgonian slaves they simply disappeared. Indeed, it was not until the barrier had been blasted away and every room, nook, and cranny of the immense structure had been literally and minutely combed that the Delgonians—and through their enslaved minds the Overlords—became convinced that their prey had in some uncanny and unknown fashion eluded them.

From GALACTIC PATROL by E. E. "Doc" Smith (1937)


Some SF novels have postulated one-shot power modules. "Laser bullets" in other words.

A .45 caliber cartridge is about 11.43 mm x 23 mm, which gives it a volume of about 2.4 cubic centimeters. At a rechargeable 2.5 kj/cm3 this means a battery the size of a .45 round would hold a good 6 kilojoules, enough for an extra-strength laser bolt.



In Norman Spinrad's Agent of Chaos, laser pistols were a ruby rod with a magazine full of "electro-crystals". Pulling the trigger caused the next crystal in the magazine to release its charge, that is, it was sort of a super-capacitor. The crystals handwavingly released their energy not as electricity, but instead as a burst of the correct frequency of light needed to pump the ruby laser rod.


Johnson drew his lasegun. The compact weapon, with its translucent sythruby barrel jutting out of its six-inch black ebonite handle, which contained the standard magazine holding fifty tiny electrocrystals each of which would give up the stored energy in its structure in one terrific burst of coherent light when the button trigger was pressed, could not be mistaken for anything innocuous.

Johnson pointed his lasegun outward, at the ring of Guards containing the crowd, pressed the trigger. A powerful beam of coherent light flashed from the barrel as the electrocrystal in the chamber gave up its energy and crumbled to dust.

The beam seared into the shoulder of at hulking, dark-skinned Guard. He screamed, writhed in pain, and fired instantly with his good right arm back in the general direction of Johnson.

From AGENT OF CHAOS by Norman Spinrad (1967)


Robert Merrill envisions individual energy capacitors in a sort of "laser revolver". Capacitors can be re-charged at leisure, but a handgun can be rapidly re-loaded from a bandoleer of charged caps. Don't throw the spent capacitors away, they can be re-charged.


Chris Roberson expanded upon Robert Merrill's concept, creating the "Cap Gun."


(ed note: for all you young whipper-snappers, the title is a pun. It makes reference to a toy that was common when I was a child, but is hard to find nowadays, the infamous "Cap Gun")

      The cap gun I’d acquired in my early years with the Orbital Patrol.
     Setting down the Space Man action figure, I picked the cap gun up off the bed and checked the action, gratified to see that it appeared to be in perfect working order.

     An energetic personal handgun, the Merrill 4KJ Capacitor Gun was equipped with a revolving cylinder containing ten capacitors, each about the length and diameter of my little finger. In the stock was a miniature generator with the ability to recharge the capacitors once used, but recharging took time (and probably makes a whining noise like a camera strobe). In pressing circumstances, the capacitors could be ejected from the chambers and already charged caps slotted into place.

     The Merrill 4KJ had two modes—beamer and needler. In beamer mode, it fired pulsed laser beams of variable intensity and duration. In needler mode, it acted as a gauss gun, accelerating slivers of metal to high speeds in the barrel. It also contained a small number of explosive flechettes that could be fired as alternative needler rounds.

     Each capacitor packed four thousand joules, roughly the amount of solar energy received from the sun at 1AU by one square meter in three seconds. Emptying a capacitor all at once in beamer mode produced roughly the same kinetic energy as a 9.33g 7.62mm NATO round, but while it had more than enough stopping power to halt a full-grown man or a feral corvid miner in its tracks, it wasn’t likely to puncture a ship’s hull and cause an explosive decompression, and so cap guns were the weapon of choice for Orbital Patrolmen and space-side Peacekeepers.

     Everyone serving in the Orbital Patrol was issued a Merrill 4KJ or an equivalent handgun from another manufacturer, but this one was mine, and had saved my life more times than I could count. Once I’d even had to rig a charged capacitor as a stand-alone explosive, but my ears still rang a month later, and it was an experience I was in no hurry to repeat. I wasn’t about to leave it behind when I was seconded to UNSA (United Nations Space Agency).
     I slid a cartridge out of the cylinder, checked the power gauge, saw that it was at full charge, and slotted it back into place, careful to ensure that the safety was engaged. I put the cap gun back on the bed and picked up the handheld.

     Arluq got the Compass Rose ready for takeoff, and the landing party was outfitted with mantles and wrist-mounted projector cuffs. The projectors were intended for use as general multi-tools, not as weapons, but when everyone gathered in the landing bay, I had my cap gun holstered at my side.
     “Captain Stone,” Xerxes said, a puzzled look on his metal features, “we’ll be landing on an uninhabited world in orbit around a dead star. Why could you possibly need to go armed?”

     “If I learned anything in the Orbital Patrol, it was that it’s always better to walk into an unknown situation and discover the sidearm you brought along wasn’t needed than walk in unarmed and discover that it was.”

     I didn’t know how right I was. If I had, I would have brought a hell of a lot more firepower with me.


In David Drake's Hammer's Slammers novels, the "powerguns" utilized an as-yet undiscovered scientific principle to instantly convert copper impregnated plastic wafers into a high-temperature bolt of plasma traveling at high velocity. Drake said all he wanted to do was postulate some hand-waving way of putting plasma bolts into bullets so he could write about futuristic soldiers. Instead of forcing his soldiers to wear a huge backpack full of batteries feeding their weapons.


Lasers, though they had air-defense applications, were not the infantryman's answer either. The problem with lasers was the power source. Guns store energy in the powder charge. A machinegun with one cartridge is just as effective—once—as it is with a thousand-round belt, so the ammunition load can be tailored to circumstances. Man-killing lasers required a four-hundred-kilo fusion unit to drive them. Hooking a laser on line with any less bulky energy source was of zero military effectiveness rather than lesser effectiveness.

Science lent Death a hand in this impasse—as Science has always done, since the day the first wedge became the first knife. Thirty thousand residents of St. Pierre, Martinique, had been killed on May 8, 1902. The agent of their destruction was a "burning cloud" released during an eruption of Mt. Pelée. Popular myth had attributed the deaths to normal volcanic phenomena, hot gases or ash like that which buried Pompeii; but even the most cursory examination of the evidence indicated that direct energy release had done the lethal damage. In 2073, Dr. Marie Weygand, heading a team under contract to Olin-Amerika, managed to duplicate the phenomenon.

The key had come from spectroscopic examination of pre-1902 lavas from Pelee's crater. The older rocks had shown inexplicable gaps among the metallic elements expected there. A year and a half of empirical research followed, guided more by Dr. Weygand's intuition than by the battery of scientific instrumentation her employers had rushed out at the first signs of success. The principle ultimately discovered was of little utility as a general power source—but then, Olin-Amerika had not been looking for a way to heat homes.

Weygand determined that metallic atoms of a fixed magnetic orientation could be converted directly into energy by the proper combination of heat, pressure, and intersecting magnetic fields. Old lava locks its rich metallic burden in a pattern dictated by the magnetic ambiance at the time the flow cools. At Pelee in 1902, the heavy Gauss loads of the new eruption made a chance alignment with the restressed lava of the crater's rim. Matter flashed into energy in a line dictated by the intersection, ripping other atoms free of the basalt matrix and converting them in turn. Below in St. Pierre, humans burned.

When the principle had been discovered, it remained only to refine its destructiveness. Experiments were held with different fuel elements and matrix materials. A copper-cobalt charge in a wafer of microporous polyurethane became the standard, since it appeared to give maximum energy release with the least tendency to scatter. Because the discharge was linear, there was no need of a tube to channel the force as a rifle's barrel does; but some immediate protection from air-induced scatter was necessary for a hand-held weapon. The best barrel material was iridium. Tungsten and osmium were even more refractory, but those elements absorbed a large component of the discharge instead of reflecting it as the iridium did.

To function in service, the new weapons needed to be cooled. Even if a white-hot barrel did not melt, the next charge certainly would vaporize before it could be fired. Liquified gas, generally nitrogen or one of the noble gases which would not themselves erode the metal, was therefore released into the bore after every shot.

From HAMMER'S SLAMMERS by David Drake.

Gun as Power Supply

In the original Star Trek episode "The Galileo Seven", Mr. Scott drains the energy out of a bunch of phaser pistols into the engines of the shuttlecraft. Doing some pointless calculations based on a very unscientific script we can hazard a guess at the energy content of a phaser pistol.

Some website I found claimed that a shuttlecraft was 17 metric tons. Assume that each crewmember is 68 kilos (150 pounds), this adds another 476 kilos for the seven crewmembers. The shuttle doesn't quite make orbit. As an upper limit, to make orbit would require a deltaV of around 8 km/s. Plugging this into the equation for kinetic energy gives us an energy requirement of about 5.6×1011 joules. There appears to be six phaser pistols drained, so each phaser contains 5.6×1011 / 6 = 9.3×1010 joules.

How much is 9.3×1010 joules? Well, it is 9.3×1010 * 2.7778×10-7 = 26,000 kilowatt-hours or 9.3×1010 / 4,500,000 = 21,000 kilograms of TNT. Well, let's face it, it takes lots of energy to vaporize an human being with one zap.

...Jaksan got wearily to his feet again. "I don't know. We can keep that in mind. It could be a lead, but I don't know." He lapsed into a deep study as they moved on but at the next halt he spoke with some of his old fire. "Dalgre, what was that process you told me about — the one for adapting disruptor shells for power?"

His assistant armsman looked up eagerly.

"It is." Within three words he had plunged into a flood of technicalities which left the rangers as far behind as if he were speaking some tongue from another galaxy. The Starfire might have lacked a mech-techneer, but Jaksan was an expert in his field and he had seen that his juniors knew more than just the bare essentials of their craft. ...

..."What do you propose to do?" Jaksan asked after a long moment.

"This process you were discussing with Dalgre, can you use disruptor charges in the sled? We must keep the extra fuel for emergencies."

"We can try to do it. It was done once and Dalgre read the report. Suppose we can, what then?"

"I'll take the sled and investigate that."...

...Jaksan was as good as his word. The next morning Dalgre, Snyn and the arms officer dismantled the largest of the disruptors and gingerly worked loose its power unit. Because they were handling sudden and violent death they worked slowly, testing each relay and installation over and over again. It took a full day of painful work on the sled before they were through, and even then they could not be sure it would really rise.

Just before sunset Fylh took the pilot;s seat, getting in as if he didn;t altogether care for his place just over those tinkered-with power units. But he had insisted upon playing test pilot.

The sled went up with a lurch, too strong a surge. Then it straightened out neatly, as Fylh learned how to make adjustments, and sped across the river, to circle and return, alighting with unusual care considering who had the controls. Fylh spoke to Jaksan before he was off his seat.

"She has a lot more power than she had before. How long is it going to last?"

Jaksan rubbed a grimy hand across his forehead. "We have no way of telling. What did that report say, Dalgre?"...

From Star Rangers (aka The Last Planet) by Andre Norton (1953).

Laser Power Output

Keep in mind that this is POWER (watts) not ENERGY (joules). That is, it measures the rate the gun can dish out laser energy.

Example: Luke Campbell's battle laser has 10 kiloJoules in each laser bolt. Since the bolt is emitted over 0.0005 seconds that means the power output is 20 megawatts. THIS DOES NOT MEAN IT NEEDS A 20 MEGAWATT BATTERY, especially since watts is a unit of power but you are probably thinking about the battery energy rating in megawatt-hours. Since Luke's battle laser has batteries containing only 100 laser bolts worth of energy in them, the battery contains 0.28 kilowatt-hours (0.00028 megawat-hours or 1,000 kilojoules). It still has to be able to deliver its 1,000 kilojoules of energy at a rate of 20 megawatts. If the battery does not have that many watts, it can use the camera-strobe trick.

Laser Power
<2 milliwattsClass 1 laser. Harmless
2 milliwattsClass 2 laser. Harmless
5 milliwattsClass 3R laser. Mostly harmless.
Laser pointers
30 milliwattsClass 3B laser if wavelength 400 to 700 nm pulsed.
Needs protective eyewear
400 milliwattsRed DVD burner x24 Dual Layer Speed Recording
0.5 wattsClass 3B laser if wavelength 315 nm to far infrared continuous.
Needs protective eyewear.
Medical laser for cosmetic procedures
>0.5 wattsClass 4 laser. Needs protective eyewear and protection
from burns and igniting combustible material.
0.7 wattsBlu Ray DVD burner x12
5 wattsBeam capable of lighting your cigar or burning wood
30 wattsLow-powered CO2 laser
60 wattsLaser light show at a rock concert
100 wattsCO2 laser used in surgical procedures
200 wattsIndustrial CO2 laser
1 kilowattBeam capable of cutting metal plates
30 kilowattsUS Navy's Laser Weapon System (LaWS)
Solid State Laser (SSL) Directed Energy Weapon (DEW)
50 kilowattsGerman point-defense laser system
100 kilowattsUS military's MILSPEC directed energy weapon for tactical targets.
"Weapons-grade Laser"
200 kilowattsDr. Schilling's sidearm: 1 kJ divided into 1000× 1 J pulses at 5 μs intervals
1 megawattUS military's MILSPEC directed energy weapon for strategic targets.
Goal of Strategic Defense Initiative spaceborne laser.
Approximate power level of the Boeing YAL-1.
5 megawattsLuke Campbell light laser pistol: 1.2 kJ divided into 60× 20 J pulses at 4 μs intervals
20 megawattsLuke Campbell battle laser: 10 kJ divided into 50× 200 J pulses at 10 μs intervals
0.25—2.4 gigawattsFictious Attack Vector: Tactical starship laser turrets


Lasers are notoriously inefficient. Figure as a general rule the efficiency of a near-future laser weapon will range from 35% to 50% with a potential to get up to 60%. So at the low end, in order to emit a 1 kilojoule bolt the laser will require 2.9 kilojoules of energy, and will have to somehow get rid of 1.9 kilojoules of waste heat. 1.0 kJ / 0.35 = 2.9 kJ. 2.9 kJ - 1.0 kJ = 1.9 kJ.

This will be much easier if the weapon is to be used on Terra or another planet with an atmosphere, where the weapon can use conduction and convection in addition to radiation for the rejection of heat. A weapon desgned for use in airless space is going to need lots of heat radiator fins because it can only use radiation.

And you'll need some serious cooling. I'd go with liquid-metal microchannel heat pipes etched into all the hot surfaces, and leading to cooling fins around the "barrel". If you use the chemical-propellant option, regenerative cooling could also work.

en note: "regenerative cooling" is where the cold liquid chemical fuel is used as coolant for the reaction chamber, right before it is fed into the chamber to be burnt for power.

Dr. Schilling

I recently asked this question to master game designer, and all around great human being Ken Burnside, who is creative director of Ad Astra Games:

Ken Burnside: "You'll also have the not-so-trivial task of not cooking the hands of the person using the weapon."

"When you fire a bullet from a rifle, about 80% of the chemical energy imparted to the projectile sends it downrange. The remaining 20% is waste heat, ejected in the form of hot brass. The waste heat rejection issue is also why caseless ammo never really took off. In round numbers, a typical .223 (5.56mm) round delivers (9752) * 0.0035 kgm/sec energy or about 3.3 kilojoules of energy to the target. It's dumping about .05 kilojoules in waste heat and hot gasses."

"Right now, lasers are about 7-15% efficient. For the sake of numbers, we'll call it 12.5%. That means that for every kilojoule you're delivering to the target, you'll need to get rid of 7 kilojoules of waste heat. Very roughly, cooking a 9oz New York Strip steak to medium-rare is about one kilojoule."



Dr. Luke Campbell has a brilliant idea. Since lasers use optics and telescopic sights use optics, why not combine the two? Much like an old fashioned reflex camera, what you see is what you get. No problems with the gun sights misaligned with the gun barrel, both the sights and the barrel are using the exact same path.

This also can be used as a solution to another problem: you cannot look through a conventional telescopic sight if you are wearing a spacesuit helmet. Such sights are designed for you to put your eye on the eyepiece, but a space helmet prevents your eye from getting that close. Well, actually the eye relief on a telescopic sight can vary from 25 mm to over 100 mm, but that is still too close for somebody wearing a fishbowl helmet. At least with a laser weapon you do not have to worry about recoil smashing the eyepiece into the fishbowl and shattering it like a large lightbulb.

But a reflex camera image can be sent to small video display, say the size of a smart phone. That can be viewed from helmet distance easily.

If you want to get more military one could attach your spacesuit to the reflex camera video feed, and project a heads-up display on the inside of the helmet.

I will also note that there currently exists a species of "scope through the gun barrel" piece of gear for conventional slug-throwing rifles, the EOP system. It uses an aftermarket TV camera since slug-throwers do not fire their bullets through optics.


With penetration, range, and repeatability dealt with, it is time to turn to accuracy. Lack of recoil, automatic fire capability, and line-of-sight accuracy are all major assets here, but there is one more improvement to be made. Both lasers and particle beams can be steered at least a degree or two off-axis, in the case of the laser via the adaptive-optic mirror, for particle beams with a transverse magnetic field at the muzzle.

If we can throw in a chip-mounted laser or acoustic gyro set, we can have a gyrostabilized handgun. The weapon shoots not at where the gun is pointed at the instant of firing, but at a weighted average of where it has been pointing over the past quarter of a second or so. Smoothes out a lot of the jitter inherent in human marksmanship.

You'd probably want to integrate this feature with the weapon's sights. A reflex-type optical sight could have an LED display linked to the gyrostabilizer, rather than a fixed reticule. The dot, or crosshairs, would then indicate the actual shot path and would remain similarly stable under jitter.

(ed note: "Reflex" in this context refers to the viewfinder on a reflex camera. A mirror allows the viewfinder to use the actual camera's optics. The user literally sees the exact image which will be captured on film. When the shutter is tripped, the mirror moves out of the way and allows the image to fall on the film. So in Dr. Schilling's concept, the shooter would aim through the laser pistol's optics, the same optics that will direct the weapon's beam.)

Dr. Schilling

Another interesting thing is that you could use the beam optics for your scope. Just install a switchable mirror that flashes reflective for the millisecond the beam is on, and you could then direct the light from your target that comes into your weapon's optics straight into an eyepiece. You could see exactly where the beam would strike without having to make any allowances for parallax or beam deflection (since the incoming light would be deflected along exactly the same path as the outgoing beam). Thus, no separate lens for a scope, sitting on top of the gun.

Luke Campbell

While using the laser's optics as a scope is pretty clever, a quicker type of sight will be needed for close in shots. Iron sights or some type of collimating sight (e.g. red dot sight, holographic sight) strapped to the top will do well.

Another clever one would be to use the laser's optics to project a laser sight. Pull the trigger, and the harmless red dot suddenly explodes. BANG!

(ed note: this will be even more accurate than a laser dot sight for a conventional slugthrower firearm. Laser dot is guaranteed to be parallel to laser weapon beam since it is using the exact same optics. Unlike bullets, weapon laser beams are not subject to bullet drop and windage. Target mobility while the bullet travels is also not a factor since the target is unlikely to be moving at a high fraction of the speed of light. The weapon laser beam will hit exactly where the red dot is resting.)

Using the laser optics as a scope would be more useful for long range or high accuracy shots.

James Borham

In combat, I would expect such a weapon to be used in automatic fire mode at ~10 Hz. With fifty to a hundred pulses to play with, you won't run out of ammunition too soon as is the case with current machine pistols. And recoilless, stabilized automatic fire should allow a moderately capable marksman to walk a burst on target in one or two reaction cycles (say, half a second) in most circumstances. Imperial Stormtroopers (tm) could no doubt still find a way to miss with such a weapon at ten meters, but not competent soldiers. Practical combat range, if you don't mind missing a good part of the time, would be on the order of 50 meters

Dr. Schilling

As it turns out, the Phaser type-I from the classic Star Trek TV show had a reflex aimsight. Turning the dial on the top would raise the acrylic aimsight. This would also work with the type-II pistol phaser, since that incorporates a type-I phaser. You can read about the aimsight here, here, here, here, and here. Refer to the illustrations below.


BandWavelength (m)
Far Infrared1e-3 to 5e-5 m (1,000,000 to 50,000 nanometers)
Mid Infrared5e-5 to 2.5e-6 m (50,000 to 2,500 nanometers)
Near Infrared2.5e-6 to 7.5e-7 m (2,500 to 750 nanometers)
Red7.5e-7 to 6.2e-7 m (750 to 620 nanometers)
Orange6.2e-7 to 5.9e-7 m (620 to 590 nanometers)
Yellow5.9e-7 to 5.7e-7 m (590 to 570 nanometers)
Green5.7e-7 to 4.95e-7 m (570 to 495 nanometers)
Blue4.95e-7 to 4.5e-7 m (495 to 450 nanometers)
Indigo4.5e-7 to 4.2e-7 m (450 to 420 nanometers)
Violet4.2e-7 to 3.8e-7 m (420 to 380 nanometers)
Ultraviolet A4e-7 to 3.15e-7 m (400 to 315 nanometers)
Ultraviolet B3.15e-7 to 2.8e-7 m (315 to 280 nanometers)
Start of
Vacuum Frequencies
2.e-7 m (200 nanometers)
Ultraviolet C2.8e-7 to 1e-7 m (280 to 100 nanometers)
Extreme Ultraviolet1e-7 to 1e-8 m (100 to 10 nanometers)
Start of
Ionizing Radiation
1e-8 m (10 nanometers)
Soft X-Ray1e-8 to 2e-10 m (10 to 2e-1 nanometers)
Hard X-Ray2e-10 to 2e-11 m (2e-1 to 2e-2 nanometers)
Gamma-Ray2e-11 to 1e-13 m (2e-2 to 1e-4 nanometer)
Cosmic-Ray1e-13 to 1e-17 m (1e-4 to 1e-8 nanometers)

There is a list of various real-world lasers and their lasing frequencies here.

Note that wavelengths shorter than 200 nanometers are absorbed by Terra's atmosphere (so they are sometimes called "Vacuum frequencies") and anything shorter than 10 nanometers is considered "ionizing radiation" (i.e., what the an average person on the street calls "atomic radiation"). So Heat Rays and Blasters will have wavelengths longer than 200 nanometers (2.e-7 m) and Ray Beams will have wavelengths that are shorter.

The cornea, lens, and vitrous humor of the eye are transparent to wavelengths between roughly 0.35×10-6 and 1.4×10-6 meters, lasers using these wavelengths can cause blindness.

Far infrared is a poor choice. Rapidly blocked by moisture in the air, and there are very few materials you can make a laser window out of (single large salt crystal or expensive high-tech materials). The wavelength is long enough that diffraction makes it difficult to focus. The only reason to use it is if you are on a budget, since 10,600 nanometer CO2 industrial lasers are common and cheap.

Mid Infrared has most of the same problems as far infrared. The US military has built a few been deuterium fluoride chemical lasers with a wavelength of 3,800 nanometers.

Near Infrared is a desirable wavelength for lasers to be used in Terra's atmosphere. There are quite a few frequencies that the atmosphere is totally transparent to: around 2500 nanometers and the band from 1200 to 700 nanometers. The best is 1000 nanometers (1e-6 m) because it will go through pretty much anything that is transparent to visible light. The ALP turret used chemical oxygen iodine lasers lasing at 1315 nanometers. Neodymium lasers lase at 1060 nanometers. Titanium sapphire lasers lase from 1100 to 800 nanometers.

Visbile Light is desirable since by definition the laser beam can pass through anything that is transparent. It does not attenuate in the atmosphere much, and it focuses more sharply than infrared. Thre is a problem with atmospheric twinkle. Of course one of the drawbacks of lasers using visible frequencies is that the laser is visible to the human eye, especially at night. When the beam hits something there will be a laser-light-show flare. If there is dust, fog, or something in the air the beam will be visible.

There are no known lasing mediums that can make high powered visible light lasers, but that doesn't mean there are none. Feel free to use them in science fiction. Certain crystals can double the frequency of light passing through them. Lithium triborate is sometimes used to frequency-double a Nd:YAG 1064 nm infrared laser beam into a 532 nm green laser beam. If you are going to be firing a laser underwater, you should use blue or green or the beam won't get very far before it is absorbed.

Near Ultraviolet can be focused to a smaller spot size than infrared or visible light. Drawbacks include attenuating faster in air, can ionize the air producing a glowing trail, the frequences are blocked by the ozone layer making orbital bombardment impossible, and ultraviolet shorter than 200 nanometers are vacuum frequencies blocked solid by atmosphere. It cannot penetrate window glass but quartz is transparent to UV.

Lasers using vacuum frequencies are Ray Beams. Lasers using frequencies longer than 200 nanometers are either Heat Rays or Blasters.

Extreme ultraviolet is difficult to make into a laser since there is nothing transparent to EUV that can be used as a window or a lens, normal mirrors do not work, and grazing mirrors work poorly (70% reflection, tops). Thus it is hard to focus the blasted rays. On the plus side they can focust to a tiny spot size and they are penetrating as all get out. The exact frequency determining the border between extreme ultraviolet and soft x-rays is nebulous.

Soft x-rays have all the advantages and drawbacks of extreme ultraviolet, but more so.

Plus one advantage: frequencies below 10 nanometers are ionizing radiation (nuclear radiation), so biological targets will also be suffering from radiation sickness.

Plus two more problems: the mirrors cannot have any imperfections larger than 10 atoms, and there isn't any good source of soft x-rays to pump the laser with (short of a fission bomb).

Hard x-rays have all the advantages and drawbacks of soft x-rays, but more so. Plus one drawback: grazing mirrors do not work at all, youh ave to use x-ray crystal diffraction to make a diffractive resonant cavity.

Gamma-rays have all the advantages and drawbacks of hard x-rays, but more so. Plus one drawback: there is no known way to focus gamma rays. The only gamma-ray laser proposal uses gamma-rays from a nuclear detonation and just tries to use gamma rays that happen to be moving in the right direction.

In the chart below, you can see the vulnerability of various parts of the human body to various laser frequencies. Hemoglobin is blood. Melanin is skin and hair. Water is all body tissue. Scatter is the molecular bonds holding proteins together.

As a point of detail: see that blue water line? That shows wavelengths to not use, because it means atmospheric water vapor is opaque at those wavelengths. Also, light that is transmitted through flesh or is scattered internally will still typically wind up being absorbed in the end.

Once you have a reasonably deep hole (fairly high aspect ratio) absorption will be essentially 100% regardless of wavelength — light that is scattered or reflected will often not bounce straight out of the hole, giving it a chance to be absorbed by the sides of the hole. This won't help with penetration, but will make the hole bigger.

Anthony Jackson

In the past, I have advocated for using "cyan" (bluish-green) lasers for orbital bombardment of Earth, mainly because of graphs like this:

This image basically plots how much light of a given frequency reaches the ground. E.g. 1m-wavelength radio waves aren't absorbed at all, visible light is absorbed a little bit, and 10nm UV is completely absorbed. We want a frequency that is not absorbed very much, and as high as possible so that we don't suffer diffraction losses.

Cyan is a sweet spot in this image: it's the furthest-left trough (i.e., highest-frequency, and therefore lowest-diffraction, band that doesn't get outright absorbed), and it's the bottom of that trough (i.e., the least-absorbed within that band).

Well, lately I got flustered with this graph for being too coarse. This graph looks like a cartoon sketch! I went looking for a better source and, well, it turns out not to exist. I mean, I can find tons of graphs that look like this, but none that have reasonable resolution (and preferably, data, so that I could reproduce it myself).

In-fact, the only detailed data that people seem to have even collected is in certain frequency ranges, notably the IR bands (ref. HITRAN, GEISA, etc. datasets, and the many projects that use them). In-particular, I played with HITRAN's buggy API for a while until I figured out they don't actually have data on the whole spectrum. However, I did find a graph:

It's basically the interesting section of the previous graph (inverted since it is transmittance rather than absorbance). It goes to 150nm, shorter than which we can be fairly confident will be absorbed by the atmosphere (such are called "vacuum frequencies" for a reason. You can still get sunburned by UV, so I assume that's basically the 300nm-400nm section of the last image that's still UV, but also nonzero transmission).

Now let's consider diffraction. To first order:

(divergence half angle) = (wavelength) / (π (aperture radius))
(spot radius) = (distance) (divergence half angle)
(irradiance) = (transmittance) (laser power) / (π (spot radius)²)
(damage rate) ∝ (irradiance)
(damage rate) ∝ π (transmittance) (laser power) ( (aperture radius) / ( (distance) (wavelength) ) )²

Considering distance, aperture radius, and available power to be constants with respect to the wavelength we choose, we can see that:

(damage rate) ∝ (transmittance) / (wavelength)²

To maximize damage rate, we simply have to take that graph and divide it by the x-axis-squared. Since the data was not available, I digitized the chart using WebPlotDigitizer, copied the approximate data out, and plotted it myself. In the graph below, you can see the original data in blue, and the effect of the division in orange.

The graph's peak says that a wavelength of about 400nm is optimal for orbital bombardment!

We can see that cyan (about 480nm) is close, at about 92% relative effectiveness. At least it's a better recommendation than green (which I also see bandied about: 532nm, 83% effectiveness).

400nm is pretty much the border between violet and ultraviolet, but in human perceptual terms it's not a binary cutoff. Under well-lit viewing conditions, the human eye sees best at about 555nm. At 400nm, a light source appears about 0.04% as bright—which might sound small, but the human visual system is logarithmic, and anyway a typical orbital-bombardment laser would use extremely high powers. As another reference: I've myself have 405nm lasers (expected 0.065% as bright) and they're plenty visible.

How general is this? Technically, it applies to surface-to-orbit/orbit-to-surface bombardment at a 70° surface-to-horizon angle. The main optical variation in the atmosphere is moisture content, but it turns out that water's transmission (for liquid or vapor) is actually coincidentally near-maximum at 400nm, so if anything more moisture will make every other wavelength even worse.

One thing that doesn't generalize is firing lasers from points on the surface to other points on the surface. In the first case, the exact height of the orbit didn't matter (it's orbital bombardment; one assumes you're above nearly all the atmosphere), but here, the path length within the atmosphere varies, meaning that the amount of absorption that you suffer at a given wavelength does too.

Given a particular range, one could measure/compute a graph like the above and get the optimal wavelength. Longer ranges will absorb more, making having a higher transmission coefficient (lower absorption coefficient) more important. But, because the Beer-Lambert law is nonlinear, there's little we can say else generally about such a graph.

Note: after the fact, I noticed that "MODTRAN", named on the source graph, is the name of a software package that computes such spectra. If it didn't cost $1800+, it'd be perfect. Of course, I could also wonder why no one hasn't just uploaded a reasonable-quality graph ever.

From a Google+ post by Ian Mallett (2018)


The US Navy is exploring the feasibility of using a high energy laser weapon as a ship-borne self-defense system against sea-skimming cruise missile attacks. Since the attenuation of laser energy by the atmosphere is the highest at low altitudes and varies with frequency, the selection of appropriate wavelengths becomes critical for a laser weapon to be effective. A high energy free electron laser (FEL) is suitable for employment in the envisaged role because it can be designed to operate at any desired frequency and, to a degree, is tunable in operation. This study aims to determine the optimal atmospheric windows for high energy, pico second, short pulse lasers.

Suitable wavelength windows were selected from either the Jan 1 or July 1, 2004 spectra for the date with a narrower transmittance window by meeting the following two criteria:

  1. Transmittance value of at least 90%, 95% and 99% respectively over a 10 km long, 10 m high horizontal path.
  2. Absorption coefficient value of less than 0.02 per km.

Table 5 summarizes the suitable wavelengths. The first four bands from 0.95 μm to 2.5 μm were able to meet the criteria of at least 90% transmittance and absorption coefficient of not more than 0.02 per km. However, there are no wavelengths in the 3.45 to 4.16 μm band that can meet the two specified criteria. The best wavelength window for this band is chosen for 70% transmission and absorption coefficient less than 0.04 per km.

From Table 5, the optimal wavelength windows for molecular atmospheric absorption are between 1.03 μm and 1.06 μm, and around 1.241 and 1.624 μm. This band provides a transmittance of more than 99%. However, as noted earlier, the main drawback of operating in a lower wavelength band is the strong extinction of energy from aerosol scattering.

Table 5.
Suitable wavelength windows for various values of T(z) in μm
T(z) > 90%
αabs < 0.01/km
T(z) > 95%
αabs < 0.005/km
T(z) > 99%
αabs < 0.001/km
T(z) > 70%
0.95 to 1.11 μm0.990 - 1.0750.992 - 0.998
1.002 - 1.006
1.01 - 1.067
1.030 - 1.060N/A
1.11 to 1.33 μm1.230 - 1.260
1.271 - 1.283
1.235 - 1.2561.241N/A
1.47 to 1.82 μm1.530 - 1.6801.535 - 1.565
1.58 - 1.595
1.610 - 1.660
2 to 2.5 μm2.125 - 2.140
2.220 - 2.245
3.45 to 4.16 μmN/AN/AN/A3.91 - 3.94

Summary of suitable wavelength bands for FEL operation for a 10 km horizontal path, 10 m above the ocean with no aerosol extinction.

(ed note: 400 nm equals 0.4 μm)


The possibility of using a laser beam as a ship-borne self-defense weapon has become more feasible with recent advancements in laser technology. The advantages of a high energy laser as a weapon are its key attributes of speed-of-light response, ability to handle fast maneuvering and crossing targets, deep magazine capacity, minimal collateral damage, target identification and adaptability for lethal to non-lethal employment. The attenuation of laser energy by the atmosphere is a result of molecular attenuation and scattering. Atmospheric scattering mainly disperses the energy of the laser beam but molecular absorption heats the atmosphere, reducing the index of refraction and thereby creating thermal blooming. The FEL has potential as a shipborne weapon system because it can be designed to operate at any desired frequency and, to a degree, is tunable in operation. The ability to select an operating frequency greatly enhances the successful propagation of the laser beam through the relatively dense air at low altitudes.

The objective of this thesis was to determine optimal operating wavelength bands for a high energy FEL weapon between 0.6 μm and 4.2 μm using the US Air Force PLEXUS Release 3 Version 2 program to set up MODTRAN 4 Version 2 and FASCODE 3 atmospheric transmission programs. Since PLEXUS and its user interface are export limited, this thesis was restricted to processing the MODTRAN and FASCODE output files. These codes allow for complex atmospheric transmittance and radiance calculations based on absorption and scattering phenomena for a variety of path geometries. The input parameters chosen for the simulation runs are meant to represent likely operational scenarios for ship self defense against a cruise missile attack. The main consideration was a 10 m altitude horizontal transmission path. Korea, Taiwan and the Persian Gulf were the three geographical areas chosen for the study. The effect of a short FEL laser pulse was modeled by convolving a normalized Gaussian frequency spectrum with the MODTRAN and FASCODE transmission and absorption coefficient spectra. The result of the convolution operation averages the transmittance values over a number of wavenumbers. The amount of averaging increases as the length of the FEL pulse decrease.

2. FASCODE Results

The higher resolution 0.1 cm-1 FASCODE was used to conduct further analysis on five selected bands or “windows” found from the MODTRAN results. Using the FASCODE aerosol extinction output file results, absorption coefficients for each wavenumber (or spectral frequency) were calculated. The molecular absorption coefficient is a key parameter for thermal blooming calculations. Data for the absorption coefficient were also used to compute the transmission spectrum for molecular absorption only. Using the transmission spectrum and absorption coefficient graphs, the optimal wavelength bands for employment of FEL at low altitudes were identified and summarized in Table 5. The four main bands of 0.95 to 1.11 μm, 1.11 to 1.33 μm, 1.47 to 1.82 μm, and 2 to 2.5 μm contain quite a number of suitable wavelengths that allow transmittance of at least 90% for a 10 km path and have absorption coefficient values of 0.02 per km or less. For a more stringent requirement of at least 99% transmittance, the suitable wavelength windows are between 1.03 to 1.06 μm and around 1.241 and 1.624 μm. However, the main concern for laser transmission through the atmosphere in the 1 μm region is the strong aerosol extinction.

So lets take a hypothetical laser sidearm, assume a 10cm lens, 10kW output power, 1ms beam duration, and 0.5 duty cycle. Given these as constant, but varying the wavelength of the laser, we get the following penetration on a carbon target at the listed ranged:

7e-7 m (Near infrared)
5.5e-7 m (Green)
100m 0.20mm
4.3e-7 m (Indigo)
100m 0.42mm
3.2e-7 m (UVA)
100m 1.02mm

It's obvious that as wavelength decreases, neglecting atmospheric effects, damage on the target increases. So the question is, how low can I push my wavelength, and what are the effects? If 90% of the UVA beam is scattered, then it is equivalent to the infrared beam. If only 50%, it is superior.

Seems like an important point to figure out. Does anyone have a good model? I've been digging on to no avail.

Eric Rozier

Hm. Not sure how you're getting penetration.

Actually, it's penetration that increases, not damage. In any case, the practical limits for laser weapons are as follows: 1) We have very limited ability to generate high power short wave lasers. 2) Beyond a certain energy density, air breaks down and becomes opaque due to nonlinear effects. I'm not sure exactly how this scales with wavelength, but I'm pretty sure shorter wavelength is worse.

Factor (1) tends to produce lasers in the 800-1000 nm range. Factor (2) doesn't generally limit modern lasers, but is a real issue for small arms lasers.

Anthony Jackson

Anthony Jackson: Hm. Not sure how you're getting penetration.

From the equations on the Atomic Rocket website. As I said, assuming a Carbon target.

(ed note: he even made an online calculator)

Anthony Jackson: Actually, it's penetration that increases, not damage.

Not sure how you figure that. At 7×10-7m, we vaporize 2.23×10-8m3 of carbon at 25m. At 4.3×10-7m, we vaporize 3.61×10-8m3 of carbon at 25m.

Both damage and penetration increase.

Anthony Jackson:

1) We have very limited ability to generate high power short wave lasers.

2) Beyond a certain energy density, air breaks down and becomes opaque due to nonlinear effects. I'm not sure exactly how this scales with wavelength, but I'm pretty sure shorter wavelength is worse.

Factor 1 disappears with less handwavium than it takes for an MFT (magic fusion torch spacecraft), so I'm not terribly concerned with it. While X-rays have some inherent problems, we can and do make cheap UV lasers right now, and there seems to be no reason why we can't up their power significantly.

Factor 2 is definitely an issue for small arms lasers, but at what point does it become a problem? What is the wave length at which we get the most bang for the buck? How bad is it at various wave lengths? Surely a model exists somewhere.

Eric Rozier

A lower limit on wavelength in oxygen atmospheres is somewhere around 150 to 200 nanometers. Below this you get single photon absorption by an electronic transition — this means your beam gets absorbed very fast.

For femptosecond pulses when you get self-focusing, you can get so called supercontinuum light, where the monochromatic light of the laser gets scattered into white light across a range of wavelengths. Self focused filaments can propagate for ten meters at least, and the primary absorption is in the plasma core of abut 0.1 mm across, indicating that air can handle gigawatt power levels across most of the visible spectrum across areas of more than 0.01 mm2.

Another data point is that 0.193 micron light (193 nanometers) at 50 GW/m2 will fall off with distance R as approximately exp(-R/100 m) due to two photon absorption.

If I'm not concerned about civilian eye safety and I don't care if the bad guys can see where I am, visible green is probably a pretty good wavelength to use for long distance lasing — it focuses well compared to longer wavelengths but doesn't suffer much from atmospheric Rayleigh scattering like shorter wavelengths. Details on calculating Rayleigh scattering can be found here

Since you are describing a pistol, however, you probably don't care about long range targets. In this case you might consider using nanosecond to femptosecond pulses, causing damage by producing power levels high enough to explode a small part of the target, thus causing mechanical damage through the shock wave rather than direct heating. Now the range depends more on your instantaneous intensity. Some rough details can be found at

In this regime, you can also use self focusing and filamentation to increase your depth of field so you can penetrate your target right through at close range

Luke Campbell

Spot Size and Brightness

An important feature of the laser is the "spot size". This is the tiniest dot the laser optics can focus the beam down to. Dr. Schilling's laser has to focus the spot size to less than a millimeter. The spot size depends upon the wavelength of the beam, the radius of the lens or mirror at the muzzle, and the range to the target. Remember that a spot 1 millimeter in diameter has a radius of 0.0005 meters.

RT = 0.305 * D * L / RL


  • RT = beam spot radius at target (m)
  • D = distance from laser emitter to target (m)
  • L = wavelength of laser beam (m, see table)
  • RL = radius of laser lens or reflector (m)

Don't forget to double the spot radius in order to get the spot diameter.

Dr. Schilling figures that a laser pistol would be unwieldy if RL is bigger than 0.025 meters (2.5 centimeter radius). For a blaster-type laser the spot size has to be about 0.0005 meters. If the laser is designed to be used in a breathable atmosphere (and this isn't a Ray Beam type laser), the wavelength will have to be between 1×10-3 and 2×10-7 meters, the smaller the better.

If you want to find the "effective range" of the laser's optics, you take the desired spot radius, weapon lens radius, and weapon laser wavelength:

D = ( RT * RL ) / ( 0.61 * L )

My slide rule says that the optics of a blaster-type laser pistol and a wavelength shorter than mid-infrared will have a range much longer than to the horizon (5 kilometers). Meaning if you can see the target, the laser has enough range to hit it. RT = 0.0005 m, RL = 0.025 m.

Pistol Blaster Range
ColorWavelengthOptics Range
Far Infrared1e-3 m60 meters
Mid Infrared5e-5 m655 meters
Near Infrared
(sweet spot)
1e-6 m32.8 kilometers
Red7.5e-7 m43.7 kilometers
Violet3.8e-7 m86.3 kiometers
Start of Vacuum Frequencies2e-7 m163.9 kilometers

Just because the optics can reach the target at range X, this does not necessarily mean the laser will damage the target. The laser has to pump out enough energy so that the energy density is high enough.

To calculate the "brightness" or energy density of the spot, you take the spot size at the target and the laser energy at the weapon's muzzle:

BPT = BP / ( π * RT2)


  • BPT = energy density of the spot (Joules/m2)
  • BP = laser energy at emitter (Joules)

Armor can be rated by the joules per square meter needed to punch a hole in the armor. This is calculated by the armor material's vaporization energy in joules per kilograms, and the armor layer's thickness in kilograms per square meter.

Laser Muzzle


Winchel Chung

I'm a little fuzzy on what the muzzle of a laser pistol would look like

Dr. Schilling's laser has to focus the spot size to less than a millimeter. He says that at a guess, a pistol could not have a focusing mirror larger than, say, 5 centimeters in diameter, which would restrict the effective range to about 60 meters.

Question: how do you vary the focus with a mirror? Does the mirror have to have a variable geometry, or do you just alter the distance between the emitter and the mirror?

Would the laser pistol muzzle look like the ALP turret, or like the lens on a camcorder, or like something totally different?

Isaac Kuo

You can just alter the distances of the optics.

For John Schilling's laser pistol, I'd guess that maybe the beam generator would have a diameter of 10mm, so the laser cavity optics suffer only 1/100 the intensity of the light on the target (1mm diameter spot). The highly reflective dielectric mirrors would only absorb maybe 1/1000 as much light as the target would absorb, so the intensity of the absorbed light would only by 1/100,000 as much as the target suffers.

It might look something like this:

However, such an exposed mechanism would get dirty and would be difficult to keep clean. Thus, the muzzle would be protected by a shroud with a clear flat circular window. This window would be much easier to wipe clean.

Luke Campbell

I always figured it would look like a camera lens. Maybe several camera lenses, for focusing at targets at long, medium, and short ranges, and the beam switched to the lens most appropriate to the target range.

Question: how do you vary the focus with a mirror? Does the mirror have to have a variable geometry, or do you just alter the distance between the emitter and the mirror?

Either would work, though the latter is simpler (although maybe slower). Note that the "emitter" should be a diverging beam (so may in fact be the focal point of a mirror that diverges the beam that comes nearly parallel out of the laser).

Would the laser pistol muzzle look like the ALP turret, or like the lens on a camcorder, or like something totally different?

The airborn laser turret would be appropriate for something that aimed itself. This would probably not be called a pistol (but would be really scary). Something designed to be pointed with a human hand and arm would have a fixed lens or mirror. If using a mirror, I expect it would protect the mirror with a window. So either a lens or mirror ends up looking like a camcorder or camera lens or some such.

David McMillan

If my experience is any guide, the field kit for such a weapon will require at least a few spare "window" glasses — even with the beam diffuse as it passes through the final optics, at these power levels a speck of dirt on the window can create a burn spot on the glass, which will absorb some of the beam energy and become larger, absorbing more of the beam, and so on. The performance drop is roughly asymptotic.

The field kit should probably also include at least one spare lens, just in case — some fumble-fingered grunt is sure to drop the weapon and crack the lens while they have the window unit detached for cleaning/replacement. On the systems I've built, the lenses usually ran ~$500 and the post-lens window glasses ~$30.

Whichever way you go, though, a near-optical laser weapon is going to raise the military mania for clean weapons to unprecedented heights.

Stephen Rider

Can we slap an iris on the ends of these suckers? Means you'd need an aiming port, but I know first hand how much dust you can get on digital optics just from changing a camera lens in a dusty room that an extra level of protection would be VERY useful.

Isaac Kuo

The iris can be made of clear plastic so it can be used for optics or to fire an "aiming dot". Its acceptable for the iris to get a little dirty. Upon firing, the iris slides out of the way to reveal the clean window underneath.

Perhaps the window behind the iris could have a number of layers. If the outer layer gets too dirty to wipe clean, you peel it off.

Business end of a laser pistol? from sfconsim-l (2007)

Triple Turret

If the business end of the laser is not sophisticated enough to have a wide range zoom lens, it might have a lens turret with multiple lenses. The turret is rotated to engage the lens appropriate for the target's distance band (long, medium, or short).

I always figured it would look like a camera lens. Maybe several camera lenses, for focusing at targets at long, medium, and short ranges, and the beam switched to the lens most appropriate to the target range.

Luke Campbell

Real world movie camera triple-turret lenses

Triple-turret lenses in science fiction.

Lasers In Practice

If one is using this information in order to write an SF novel, the question comes up of what will an observer see and hear during a laser pistol battle. Luke Campbell has the information.

What would it sound like?

The actual mechanism of producing the laser beam could sound like anything, from complete silence, to the click of an electrical contact, to a sharp, electric snap, to a gunshot-like thunderclap.

The beam, when incident upon its target, will make a nice bang.

The pistol won't make a "zap" sound, will it?

If the beam is repeated rapidly it might, however, make a buzz. It might end up sounding quite electrical at a few hundred Hertz.

Will it be too quiet to hear or will be loud enough to cause hearing loss? Will it sound like an extended explosion as the series of steam detonations bore a hole?

Remember that the temporary cavity caused by the explosions only lasts a few milliseconds, so the beam has to have completed its work of piercing the target at this time. The individual explosions will be too closely spaced (microseconds apart) to be individually audible. Since shocks are always supersonic to the air in their path, and subsonic to the moving air left behind them, multiple subsequent shocks from the same source tend to merge into one stronger shock. Thus, each pulse probably makes one bang. The bang comes from a series of explosions whose total energy is about the same as that of the gunpowder detonating in a firing rifle, so it will probably be about as loud.

What would the beam look like?

This depends on a number of things. If the beam is in the visible part of the spectrum, you get a noticeable path through clean air at indoor lighting intensities. I am not sure if it will be visible out of doors under full sunlight, but you could see it at night. The beam will be widest at the aperture of the gun, probably a few centimeters across to keep the optics from being damaged by the intense light. The beam will converge to a spot a millimeter or so across at the target. In unclean air, the beam will be a lot more visible. This Rayleigh scattering is linear, so the total integrated brightness across the cross section of the beam should be constant, if we neglect the gradual attenuation of the beam due to the light being scattered out of it. Higher frequency light scatters much more than lower frequency light, so a blue beam would be much more visible than a red one.

When a visible beam is incident on the target, it creates a very bright flash of the same color as the beam. This may temporarily dazzle those looking at it, and the beam itself may be overlooked because of the bright flash obscuring it.

If the weapon lases in the UV, the intense pulse may cause multi-photon ionization of atoms in the air, causing a fluorescent glow along the path of the beam (possibly red, green, or violet, I'm not quite sure what sparsely ionized air at atmospheric pressure looks like). Since this process is non-linear, it will be dimmest near the aperture where the beam is widest, and most intense nearer the target. Weapon designers will probably try to minimize this effect, since it leads to attenuation of the beam and subsequent loss of effectiveness.

Near IR beams are likely to only be visible if there are relatively large pieces of dust, lint, or pollen floating around, which will glow incandescent as they burn under the irradiation of your beam. I doubt beams in the "thermal" IR range would be used, even though the air is fairly transparent to these wavelengths, because with short, intense pulses you tend to get cascade ionization with these lower frequencies, and this will completely absorb the beam.

Beams at non-visible frequencies will also make a flash and a bang where incident on the target from the expanding plasma of their explosion, but nowhere near as bright as that of a visible beam.

In vacuum, of course, the beam itself is always invisible, but you can still see the flashes at the target.

Luke Campbell

What would the Asteroid Pirate look like after they got hit?

The method of subsequent explosions on the back of an expanding cavity driving the cavity through the target will leave a wound much like that of a gunshot, except without fun stuff like the bullet fragmenting or breaking up. A variant where nearly parallel beams a few cm apart literally rip the tissue between them could leave a wound looking more like an ugly gash - add on a few more of these beams on the same plane and you could literally cut someone in half with one millisecond pulse, using only about as much energy as goes into accelerating the bullet of a modern day battle rifle. (ed note: in some SF novels by E.E."Doc" Smith and Robert Heinlein, this is referred to as setting your sidearm to "fan beam".)

Will there be a large splash of blood and gore on the wall behind the unlucky pirate?

Quite likely, Note that since you do not have the momentum associated with a projectile, it will be more spread out than you would get from a gunshot wound, and you would get blood and gore coming out the front, too.

I assume that since the beam is one millimeter in diameter but the hole in the pirate is four centimeters, little or no wound cauterization will occur.

Nope, the wound would be ragged and messy. It is created by mechanical, not thermal effects.

Luke Campbell

Laser / Bullet Pro and Con

Laser sidearms and Slugthrower sidearms have various advantages and disadvantages relative to each other.

Advantage Laser:

  • Laser bolt travels at the speed of light in atmosphere, bullets are much slower
  • Laser bolt is not affected by gravity or air resistance, but the accuracy of a bullet is significantly degraded
  • Damage inflicted by a laser bolt can be finely dialed up or down for nuance. Bullets are mostly constant, except for air resistance
  • Laser sidearms have no recoil. Slugthrowers kick like a mule
  • Lasers just need electricity which is available from many field sources. Slugthrowers require bullet ammunition which have logistical supply problems

Advantage Slugthrower:

  • Need no electricity, while lasers requires lots of if
  • Bullet ammunition takes up far less space than laser electrical batteries/power source
  • Ejected bullet shells take care of waste heat problem, lasers need cooling fins
  • Bullets do not have their damage potential reduced by dust, smoke, clouds or rain. Laser do.

(ed note: in this future society, duels are legal. Everybody uses energy weapons, bullet-firing slugthrowers are ancient history)

      "Me? Shucks, no. I'm one long joke on myself. Remind me to tell you about it sometime. But look—the other thing I came to see you about. Notice my new sidearm?"
     Monroe-Alpha glanced at Hamilton's holster. In fact, he had not noticed that his friend was bearing anything new in the way of weapons—had he arrived unarmed Monroe-Alpha would have noticed it, naturally, but he was not particularly observant about such matters, and could easily have spent two hours with a man and never noticed whether he was wearing a Stokes coagulator or a common needlebeam.
     But, now that his attention was directed to the matter, he saw at once that Hamilton was armed with something novel…and deucedly odd and uncouth. "What is it?" he asked.
     "Ah!" Hamilton drew the sidearm clear and handed it to his host. "Woops! Wait a moment. You don't know how to handle it—you'll blow your head off. " He pressed a stud on the side of the grip, and let a long flat container slide out into his palm. "There—I've pulled its teeth (no, you haven't. You also have to check that there is no round in the chamber). Ever see anything like it?"
     Monroe-Alpha examined the machine. "Why, yes, I believe so. It's a museum piece, isn't it? An explosive-type hand weapon?"
     "Right and wrong. It's mill new, but it's a facsimile of one in the Smithsonian Institution collection. It's called a point forty-five Colt automatic pistol."
     "Point forty-five what?"
     "Inches…let me see, what is that in centimeters?"
     "Huh? Let's see—three inches make a yard and a yard is about one meter. No, that can't be right. Never mind, it means the size of the slug it throws. Here…look at one." He slid one free of the clip. "Damn near as big as my thumb, isn't it?"
     "Explodes on impact, I suppose."
     "No. It just drills its way in."
     "That doesn't sound very efficient."
     "Brother, you'd be amazed. It'll blast a hole in a man big enough to throw a dog through."

     Monroe-Alpha handed it back. "And in the meantime your opponent has ended your troubles with a beam that acts a thousand times as fast. Chemical processes are slow, Felix."
     "Not that slow. The real loss of time is in the operator. Half the gunfighters running around loose chop into their target with the beam already hot (continuous beam laser). They haven't the skill to make a fast sight. You can stop 'em with this, if you've a fast wrist. I'll show you. Got something around here we can shoot at?"
     "Mmm…this is hardly the place for target practice."
     "Relax. I want something I can knock out of the way with the slug, while you try to burn it. How about this?" Hamilton picked up a large ornamental plastic paperweight from Monroe-Alpha's desk.
     "Well…I guess so."
     "Fine." Hamilton took it, removed a vase of flowers from a stand on the far side of the room, and set the target in its place. "We'll face it, standing about the same distance away. I'll watch for you to start to draw, as if we really meant action. Then I'll try to knock it off the stand before you can burn it."
     Monroe-Alpha took his place with lively interest. He fancied himself as a gunman, although he realized that his friend was faster. This might be, he thought, the split second advantage he needed. "I'm ready."
     Monroe-Alpha started his draw.

     There followed a single CRACK! so violent that it could be felt through the skin and in the nostrils, as well as heard. Piled on top of it came the burbling Sring-ow-ow! as the bullet ricocheted around the room, and then a ringing silence.
     "Hell and breakfast, " remarked Hamilton. "Sorry, Cliff—I never fired it indoors before." He stepped forward to where the target had been. "Let's see how we made out. "
     The plastic was all over the room. It was difficult to find a shard large enough to show the outer polish. "It's going to be hard to tell whether you burned it, or not."
     "I didn't."
     "That noise—it startled me. I never fired."
     "Really? Say, that's great. I see I hadn't half realized the advantages of this gadget. It's a psychological weapon, Cliff."
     "It's noisy."
     "It's more than that. It's a terror weapon. You wouldn't even have to hit with your first shot. Your man would be so startled you'd have time to get him with the second shot. And that isn't all. Think…the braves around town are used to putting a man to sleep (killing him) with a bolt that doesn't even muss his hair. This thing's bloody. You saw what happened to that piece of vitrolith. Think what a man's face will look like after it stops one of those slugs. Why a necrocosmetician would have to use a stereosculp to produce a reasonable facsimile for his friends to admire. Who wants to stand up to that kind of fire?"

(ed note: Monroe-Alpha and Hamilton go to eat at a fancy restaurant. Some stupid bravo insults Hamilton, trying to start a duel.)

     Monroe-Alpha touched Hamilton's arm. "He's drunk, " he whispered. "Take it easy."
     "I know, " his friend answered in a barely audible aside, "but he gives me no choice."
     "Perhaps his friends will take care of him."
     "We'll see."
     Indeed his friends were attempting to. One of them placed a restraining hand on his weapon arm, but he shook him off. He was playing to a gallery—the entire restaurant was quiet now, the diners ostentatiously paying no attention, a pose contrary to fact. "Answer me!" he demanded.
     "I will, " Hamilton stated quietly. "You have been drinking and are not responsible. Your friends should disarm you and place a brassard on you. Else some short-tempered gentleman may fail to note that your manners were poured from a bottle."
     There was a stir and a whispered consultation in the party behind the other man, as if some agreed with Hamilton's estimate of the situation. One of them spoke urgently to the belligerent one, but he ignored it.
     "What's that about my manners, you misplanned mistake?"
     "Your manners, " Hamilton stated, "are as thick as your tongue. You are a disgrace to the gun you wear."
     The other man drew too fast, but he drew high, apparently with the intention of chopping down.

     The terrific explosion of the Colt forty-five brought every armed man in the place to his feet, sidearm clear, eyes wary, ready for action. But the action was all over. A woman laughed, shortly and shrilly. The sound broke the tension for everyone. Men relaxed, weapons went back to belts, seats were resumed with apologetic shrugs. The diners went back to their own affairs with the careful indifference to other people's business of the urbane sophisticate.
     Hamilton's antagonist was half supported by the arms of his friends. He seemed utterly surprised and completely sobered. There was a hole in his chemise near his right shoulder from which a wet dark stain was spreading. One of the men holding him up waved to Hamilton with his free arm, palm out. Hamilton acknowledged the capitulation with the same gesture.

     Hamilton chewed his lip. "I say…you'll pardon me…but isn't it indiscreet for a man who does no fighting to appear in public armed?"
     Mordan smiled. "You misconstrue. Watch." He indicated the far wall. It was partly covered with a geometrical pattern, consisting of small circles, all the same size and set close together. Each circle had a small dot exactly in the center.
     Mordan drew his weapon with easy swiftness, coming up, not down, on his target. His gun seemed simply to check itself at the top of its swing, before he returned it to his holster.
     A light puff of smoke drifted up the face of the wall. There were three new circles, arranged in tangent trefoil. In the center of each was a small dot.

From BEYOND THIS HORIZON by Robert Heinlein (1948)

      The girl laughed harshly. “Lord, I sure do get the live ones, don’t I? I just can’t believe it,” she repeated. “If I hadn’t seen you in action … What are those things, anyway?” she said, pointing to Jalandra’s pistols.
     He took one out, thumbed on the safety, and showed it to her. “Rhorrvo-Jenkins’n 11-mm. automatics. A chemical explosion set off inside each cartridge propels a small pellet, called a bullet, out the barrel.” He slipped out the clip. “Each one of these holds nine cartridges. Some sets are explosive bullets; others are non-explosive slugs of lead or steel. Or some other things. Depends on what I want to use them for.”

     “Sounds weird, but I guess they work pretty good. Loud, though.”
     He smiled. “You get used to it.“ He replaced the clip and returned the automatic to its holster. “The advantage over a blaster is primarily impact. A blaster beam is primarily heat energy. Hit a man in the arm, say, and while you’re burning the arm off, he can put a beam in your guts. A man gets hit with one slug from these automatics, he’s not going to be returning fire very accurately. At short range, it’s as accurate as a blaster, and at longer ranges a blaster beam’s not that effective, anyway. The heat’s not intense enough. The speed difference is negligible. I more than make up for that.

     “So my uncle became my guardian, and he trained me. For my thirteenth birthday he made those automatics and gave them to me.”
     “Made them?”
     “Yes. He was a gunsmith. Benson didn’t have a lot of off-world trade, probably because it didn’t have much worth exporting, so we were pretty self-sufficient. He had seen the design somewhere and made copies. He wouldn’t let me wear them in public, and he wouldn’t let me register. But he practiced with me every day, drawing and shooting.

     “Take shooting. Most blaster-men aren’t really good marksmen, because they don’t have to be. Most of them shoot first and aim afterward. Oh, they shoot in the right general direction, but, since the beam is visible and lasts as long as the charge holds out, most of them use the beam itself to adjust their aim. In itself, that visible beam is handy; you can adjust your fire quickly and precisely. The trouble is, everybody’s lazy. They get to depend on being able to take that split-second to direct the beam precisely on target.

     “You can’t do that with those guns of mine.

     “I got to know those guns better than my own hands. I could take them apart and put them together in the dark. l could hold one in my hand and tell you how many shells were left in the clip, just from judging the weight.

(ed note: Jalandra the professional duelist takes his lady fair Julane to a fancy restaurant. A stupid bravo from Vega sends a fancy drink to Julane, tring to pick her up.)

     Jalandra shook his head. Incredible. He looked at Julane and saw, with surprise, fear in her eyes. He sensed rather than saw the Vegan approach.
     “Let me buy you a drink,” the man said to Julane, “even if he won’t.”
     Jalandra was too shocked for a moment even to speak. When he did, his voice went high with disbelief. “Are you out of your Bog-bedamned mind?” he cried. “l’ll blow you apart!”
     The Vegan swung toward Jalandra, backed away a step. The room had gone suddenly still at Jalandra’s outburst. “Challenge,” he said in the silence. (dueling is legal in this society)

     For an instant, Jalandra looked at him, unable fully to believe anyone quite capable of such conduct. “Accepted,” he said. Without moving from his chair, he drew his right-hand automatic and fired.
     The Vegan was fast. For the briefest of moments the astonishment on Jalandra’s face was mirrored on his own. Then he reached for the blaster at his side. He did not quite make it.
     By the time the Vegan’s body hit the floor, there were five gaping holes in it. Let them patch that up, Jalandra thought savagely.

     As Jalandra’s automatic went off thunderously, nearly everyone in the room jumped. Half a dozen men were standing. A few even had guns out. Those hastily holstered and sat down. A loud murmur replaced the silence that had again fallen as the echoes of the automatic died away. Abruptly, everyone was babbling to his neighbor.

From LORD OF THE RED SUN by William T. Silent (1972)

Laser Blindness

As I already stated, pretty much no science fiction in movies, TV or novels mentions the blindness hazard of laser sidearms (with the possible exception of Jack Williamson's Trapped In Space). On Terra, anybody within about five kilometers (i.e, the horizon) of an operating laser weapon is at risk of loosing their eyesight permanently. If the beam flicks over a window, a shiny automobile, or anything else reflective (reflected or scattered light); an innocent bystander will suddenly require the services of a working dog. People knowingly entering a laser gun battle will be wearing anti-laser goggles (or contact lenses). Laser gunmen who care about innocent bystanders will use lasers of frequencies opaque to the cornea of the eye. That means either greater than 1400nm (infrared to microwave) or less than 400nm (ultrviolet to x-ray). In other words, a frequency other than the rainbow colors of visible light.

There is a laser safety classification system. Class 1 is safe for eyesight. Class 1M is safe as long as you are not looking at the laser through a magnifying glass or telescope. Class 2 is safe for eyesight due to the human blinking reflex (most laser pointers fall into this catagory). Class 2M is safe with no magnifying glasses or telescopes. Class 3R are mildy dangerous. Class 3B are dangerous but diffuse reflection is not (laser protective goggles required). Class 4 are incredibly dangerous, since it will also burn holes in clothing and skin (laser protective goggles required). Naturally all laser weapons are class 4.

Will the beam be invisible or bright enough to be blinding?

It is quite likely to be both. The beam itself may be invisible or minimally visible, but if even a tiny fraction of the beam is specularly scattered into your eye, near IR and visible and some near UV will be focused to a diffraction limited spot on your retina, causing burns and permanent scarring. This can lead to degradation of vision or total blindness. Interestingly, the brain compensates for blind spots on the retina, so that you might have lost up to 60% of your vision from multiple exposures to beams and you still think you can see just fine. Also interestingly, the fluid in our eyes can cause a small amount of non-linear upconversion of intense coherent light that passes through it, so when directly exposed to a near IR beam, you may actually see it as two IR photons are combined into one visible photon with twice the frequency. Some people who have been blinded by pulsed neodymium lasers (which lase at around 1 micron near IR) have reported that the last thing they ever saw was a green flash (green, at 0.5 micron, has half the wavelength and twice the frequency of the 1 micron neodymium line).

Anyone likely to be using a laser will probably wear protective goggles or contacts. With today's technology, you would probably make them out of an optical band gap material that excludes a very narrow window of light centered on the laser's frequency. This means that the people who fired the lasers would not be able to see the beams or flashes of their own weapons (assuming they used visible light lasers). They would still see the flashes from the plasma explosions, though, plus incandescence of suspended atmospheric particles and fluorescence from multi-photon absorption.

Luke Campbell

Luke has more details about laser eye damage here. Below is a sample:

LUKE CAMPBELL: Any death ray worth its name will be sufficiently intense that anyone looking directly into the beam will be instantly blinded (if not killed — it is, after all, a death ray). There are, however, other vision hazards. The cornea, lens, and vitrous humor of the eye are transparent to wavelengths between roughly 0.35×10-6 and 1.4×10-6 meters. If a small fraction of a death ray beam in this wavelength range is specularly reflected off a smooth surface, anyone looking at that surface will focus the reflected light into a tiny spot on their retina. This can heat the retina up enough to cause a third degree burn, leading to a spot of permanent blindness. Very powerful lasers (such as just about any death ray) can still be hazardous after mutliple specular reflections — the fraction of the beam that reflects off the target might bounce off a shiny hubcap, reflect off a window, and then reflect off the shiny paint job of a passing car to blind a bystander.

JOHNNY1A: Suppose our weapon users want to minimize the effect on potential innocent bystanders, or are worried about having to fight without their optical protections. What would be the best way to make such a laser weapon so that bystanders/unshielded users were not blinded?

LUKE CAMPBELL: You could use a weapon that emits a beam at frequencies that are mostly absorbed by the lens or vitreous humor. I seem to recall that laser light at 1.5 microns near IR and longer wavelengths are largely absorbed by the eye before any of it can get to the retina. At the other end of the spectrum, many near UV wavelengths are also absorbed by the materials of the eye.

(ed note: Holger Bjerre points out that while such UV wavelengths do not penetrate the eye, they will abrade the surface of the eye. After all, such UV lasers are used for laser-vision correction surgery. Such abrasion may or may not be correctable, but it is damage.)

LUKE CAMPBELL: If I'm not concerned about civilian eye safety and I don't care if the bad guys can see where I am, visible green is probably a pretty good wavelength to use for long distance lasing - it focuses well compared to longer wavelengths but doesn't suffer much from atmospheric Rayleigh scattering like shorter wavelengths.

ISAAC KUO: Is there even a plausible solution to the eye safety problem? I can see that for missile defense or blowing up IEDs, eye safety might not be too much of a problem...but for small arms it seems implausible to field weapons that tend to leave civilians blind.

ANTHONY JACKSON: You can cut down on it by a lot by using frequencies that don't pass through the eye. That means either greater than 1400nm (infrared to microwave) or less than 400nm (ultrviolet to x-ray). There is still the possibility of indirect blinding caused by the target of the laser being heated white-hot and emitting thermal radiation, and it's possible to actually produce sunburns on the cornea if enough radiation hits them, but these are lesser problems (and the latter effect probably isn't a factor at ranges where the heat won't also start fires).

For that matter, self-focusing lasers may not reflect well and thus have similar advantages.

LUKE CAMPBELL: Other than repeating what Anthony said, let me just expand a bit on the self focusing aspects. A self focused filament will convert the initially coherent laser radiation into incoherent white light directed by the lens that its field creates in air rather than the inherent directionality of the light. Take away the air, or the high field causing the lensing, and the light will spray out in all directions (it is actually mostly forward and backward propagating, but is not tightly collimated). If part of the light is reflected, it will lose this self focusing ability. Even incoherent light can be dangerous if it is intense enough, but less so than a collimated reflected beam. In addition, when the beam interacts with solid matter, it will flash that matter to plasma, and the plasma will absorb much of the beam. Most reflections will be off the plasma-air interface, which is likely to be irregular thus giving diffuse rather than specular reflection.

All this assumes that the self focusing works as advertised. If your gun tries to self focus the beam half a meter in front of the target, but it misjudges the distance to the target, the beam could still be monochromatic and coherent, and might reflect off shiny bits. Is this more of a worry than bullet ricochets from modern firearms? I don't actually know.

ISAAC KUO: This filamenting ability seems to require a very high power level, so diffuse reflection would seem to be dangerous. I'm thinking of close quarters situations, like a hostage rescue, where the civilians in question might be less than a meter from the bad guys you're shooting at.

But let's suppose we're not using filamenting. A "death ray" laser weapon is going to need to be somewhat powerful in order to take down the bad guy. Even if we're using a wavelength that is blocked by the eye, diffuse radiation from the hot target spot might be a problem. Is it?

Or maybe the diffuse radiation is only as much of a threat to eyesight as the muzzle flash of a pistol?

ISAAC KUO: This filamenting ability seems to require a very high power level, so diffuse reflection would seem to be dangerous.

LUKE CAMPBELL: While the power can be mind bogglingly high, the total energy can be fairly moderate. To cause eye injury (of the sort normally discussed with lasers) you need to deposit enough energy onto a point on the retina to cause third degree burns, fast enough that heat conduction can't take the energy away. Filamented beams clearly have the fast part down, but an uncollimated reflection may not deposit enough energy to burn (or it might — we really don't have the experience with this yet).

ISAAC KUO: Even if we're using a wavelength that is blocked by the eye, diffuse radiation from the hot target spot might be a problem. Is it?

LUKE CAMPBELL: I expect it is more like the threat of the arc of an arc welder. Glancing at the flashes, or watching from a distance is pretty safe, but the welder himself better be wearing protective eyewear.

ANTHONY JACKSON: Looking at laser safety (, a typical weapons laser will probably take somewhere between a microsecond and a millisecond to drill into a target, split into multiple pulses.

Each pulse will be something like 10J and 10-9 seconds. That time gives a safe level of 5×10-7 J/cm2 or 5×10-3J/m2. At 1 meter, the reflected light will probably be 0.1 to 0.5J/m2, so each pulse will be a hazard out to 5-10 meters.

In addition, we're delivering 1+ kilojoules over maybe a millisecond. That increases our maximum dose to 1×10-5J/cm2, but we're delivering 100+ times as much energy, so this will give a hazard at 10-20 meters. Note that the safe level is 10% of the 50% damage threshold, so the 50% damage distance is 3-6 meters for a 1 kilojoule laser.

ISAAC KUO: Oh! Blink reflex!

If you use a visible laser, like a green laser, then you can maybe flash a weak "safety" pulse to induce endangered civilian eyes to blink before the main weapon pulses.

Put maybe 0.1 seconds between the safety pulse and the main pulse. That's enough time for civilians to blink but not enough time for a bad guy to dodge the "bullet". That's similar to the time delay of a pistol bullet traveling 30m.

ANTHONY JACKSON: It's not like the safety pulse has to be the same wavelength as the main pulse. However, I suspect a better option is to use a wavelength that doesn't penetrate the eye, and then operate at a power level low enough that plasma formation is not a major factor (relying on regular vaporization). This means that the reflected primary beam is not directly dangerous unless it actually hits someone at near full power, and emitted radiation is (a) fairly long wave, and (b) a small minority of the energy release.

Unfortunately, this still requires bringing the surface up to the sublimation temperature of the material. This is not a problem for humans or for soft armors, but refractory ceramics will require temperatures in excess of 3,000K, which will give an emissions peak in the near IR.

Also note that Protocol IV of the 1980 Convention on Certain Conventional Weapons (issued by the United Nations on 13 October 1995) states:

Article 1: It is prohibited to employ laser weapons specifically designed, as their sole combat function or as one of their combat functions, to cause permanent blindness to unenhanced vision, that is to the naked eye or to the eye with corrective eyesight devices. The High Contracting Parties shall not transfer such weapons to any State or non-State entity.

Article 2: In the employment of laser systems, the High Contracting Parties shall take all feasible precautions to avoid the incidence of permanent blindness to unenhanced vision. Such precautions shall include training of their armed forces and other practical measures.

Article 3: Blinding as an incidental or collateral effect of the legitimate military employment of laser systems, including laser systems used against optical equipment, is not covered by the prohibition of this Protocol.

Article 4: For the purpose of this protocol "permanent blindness" means irreversible and uncorrectable loss of vision which is seriously disabling with no prospect of recovery. Serious disability is equivalent to visual acuity of less than 20/200 Snellen measured using both eyes.

Of course the U.S. Department of Defense is working on the Personnel Halting and Stimulation Response rifle, which is a laser-blinding weapon intended for crowd control. It is intended to skirt the 1995 UN Protocol on Blinding Laser Weapons by not blinding the target permanently (they hope).


(ed note: Warning: Spoilers for the story follow. The protagonist is a native of the fictional African nation of Umbala, which on the equator has a fictional Zambue crater. The nation has been taken over by a power-mad dictator named Chaka who has instituted a reign of terror. The protagonist is only a humble astronomer, but realizes Chaka must be stopped. The fact that Chaka put to death several of the astronomer's relatives only makes it personal.

The radio telescope will be opening soon. The astronomer knows that Chaka won't be able to resist taking the elevator to the top of the telescope and overlooking his domain.

Meanwhile, the narrator is waiting on the other side of the hills.)

It seems strange that my country, one of the most backward in the world, should play a central role in the conquest of space. That is an accident of geography, not at all to the liking of the Russians and the Americans. But there is nothing that they could do about it; Umbala lies on the equator, directly beneath the paths of all the planets. And it possesses a unique and priceless natural feature: the extinct volcano known as the Zambue Crater.

When Zambue died, more than a million years ago, the lava retreated step by step, congealing in a series of terraces to form a bowl a mile wide and a thousand feet deep. It had taken the minimum of earth-moving and cable-stringing to convert this into the largest radio telescope on Earth. Because the gigantic reflector is fixed, it scans any given portion of the sky for only a few minutes every twenty-four hours, as the Earth turns on its axis. This was a price the scientists were willing to pay for the ability to receive signals from probes and ships right out to the very limits of the solar system.

Chaka was a problem they had not anticipated. He had come to power when the work was almost completed, and they had had to make the best of him. Luckily, he had a superstitious respect for science, and he needed all the rubles and dollars he could get. The Equatorial Deep Space Facility was safe from his megalomania; indeed, it helped to reinforce it.

The Big Dish had just been completed when I made my first trip up the tower that sprang from its centre. A vertical mast, more than fifteen hundred feet high, it supported the collecting antennas at the focus of the immense bowl. A small elevator, which could carry three men, made a slow ascent to its top.

As soon as the NASA technicians had installed their equipment and handed over the Hughes Mark X Infrared Communications System, I began to make my plans.

Colonel Mtanga, his Chief of Security, would object, but his protests would be overruled. Knowing Chaka, one could predict with complete assurance that on the official opening day he would stand here, alone, for many minutes, as he surveyed his empire. His bodyguard would remain in the room below, having already checked it for booby traps. They could do nothing to save him when I struck from three miles away and through the range of hills that lay between the radio telescope and my observatory. I was glad of those hills; though they complicated the problem, they would shield me from all suspicion. Colonel Mtanga was a very intelligent man, but he was not likely to conceive of a gun that could fire around corners. And he would be looking for a gun, even though he could find no bullets….

I went back to the laboratory and started my calculations. It was not long before I discovered my first mistake. Because I had seen the concentrated light of its laser beam punch a hole through solid steel in a thousandth of a second, I had assumed that my Mark X could kill a man. But it is not as simple as that. In some ways, a man is a tougher proposition than a piece of steel. He is mostly water, which has ten times the heat capacity of any metal. A beam of light that will drill a hole through armour plate, or carry a message as far as Pluto—which was the job the Mark X had been designed for—would give a man only a painful but quite superficial burn. About the worst I could do to Chaka, from three miles away, was to drill a hole in the colourful tribal blanket he wore so ostentatiously, to prove that he was still one of the People.

For a while, I almost abandoned the project. But it would not die; instinctively, I knew that the answer was there, if only I could see it. Perhaps I could use my invisible bullets of heat to cut one of the cables guying the tower, so that it would come crashing down when Chaka was at the summit. Calculations showed that this was just possible if the Mark X operated continuously for fifteen seconds. A cable, unlike a man, would not move, so there was no need to stake everything on a single pulse of energy. I could take my time.

But damaging the telescope would have been treason to science, and it was almost a relief when I discovered that this scheme would not work. The mast had so many built-in safety factors that I would have to cut three separate cables to bring it down. This was out of the question; it would require hours of delicate adjustment to set and aim the apparatus for each precision shot. I had to think of something else; and because it takes men a long time to see the obvious, it was not until a week before the official opening of the telescope that I knew how to deal with Chaka, the All-Seeing, the Omnipotent, the Father of his People.

It took me three days to install the carefully silvered, optically perfect mirror in its hidden alcove (at the top of the hills). The tedious micrometer adjustments to give the exact orientation took so long that I feared I would not be ready in time. But at last the angle was correct, to a fraction of a second of arc. When I aimed the telescope of the Mark X at the secret spot on the mountain, I could see over the hills behind me. The field of view was tiny, but it was sufficient; the target area was only a yard across, and I could sight on any part of it to within an inch.

Along the path I had arranged, light could travel in either direction. Whatever I saw through the viewing telescope (at his observatory on one side of the hills) was automatically in the line of fire of the transmitter.

It was strange, three days later, to sit in the quiet observatory, with the power-packs humming around me, and to watch Chaka move into the field of the telescope (standing at the top of the radio telescope on the other side of the hills). I felt a brief glow of triumph, like an astronomer who has calculated the orbit of a new planet and then finds it in the predicted spot among the stars. The cruel face was in profile when I saw it first, apparently only thirty feet away at the extreme magnification I was using. I waited patiently, in serene confidence, for the moment that I knew must come—the moment when Chaka seemed to be looking directly toward me. Then with my left hand I held the image of an ancient god who must be nameless, and with my right I tripped the capacitor banks that fired the laser, launching my silent, invisible thunderbolt across the mountains.

Yes, it was so much better this way. Chaka deserved to be killed, but death would have turned him into a martyr and strengthened the hold of his regime. What I had visited upon him was worse than death, and would throw his supporters into superstitious terror.

Chaka still lived; but the All-Seeing would see no more. In the space of a few microseconds, I had made him less than the humblest beggar in the streets.

And I had not even hurt him. There is no pain when the delicate film of the retina is fused by the heat of a thousand suns.

From THE LIGHT OF DARKNESS by Arthur C. Clarke (1966)


WARNING: if you are easily nauseated or upset, I'd skip this section if I were you. Also skip if you are younger than 18, this means You. Jump here instead.

Among the many settings on the amazing Star Trek Phaser dial-a-gun is "Dematerialize". This is basically a disintegrator ray, where whatever you shoot turns into a glowey outline and quietly fades away.

Rocketwash. It ain't going to be so soft and gentle. Vaporizing a human body will be akin to detonating a mannequin made out of C-4 plastic explosive. Not to mention what happens when the laser battery in the victim's laser pistol cooks off.

Scott Lowther has the straight dope:


I’ve always liked the phasers of Star Trek more than the blasters/turbolasers of Star Wars. Ship to ship: phasers are computer controlled and seem to always hit the target (even if they don’t necessarily damage the target), while turbolasers are manually targeted and can’t seem to hit a damn thing. Same with hand-held weapons… phasers are zero time of flight weapons that non-professional soldiers can wield accurately, while blasters seem to travel slower than bullets and the biggest, most expensive and advanced military out there has troops so poorly trained that they can’t seem to hit the broad side of a barn.

But there’s one area where blasters are better than phasers: total energy usage per shot. If you get shot with a blaster, it’s like getting shot with a firearm. Perhaps an extra powerful firearm… a 12-gauge filled with buckshot, perhaps, but still roughly equivalent to a conventional gun. But phasers have a top setting that will vaporize a human. That’s not just overkill, that’s an insane level of overkill. It’s like using a TOW anti-tank missile to target an individual.

And this is one of the things that Star Trek got wrong. Not that it’s necessarily impossible for a weapon the size of a keychain to vaporize a human, but that the process of vaporizing the human wouldn’t utterly trash the surroundings. Face it: you’re converting, oh, 180 pounds of water to steam, and converting the calcium in the bones, the metal and plastic in his clothes, tools, weapons, etc. into plasma. And if the target is also holding a phaser, you’re converting that into vapor, which means that its battery (or whatever the power source is) is going to explode.

Phaser-vaporizing someone on board a spaceship is going to be a disaster, because by converting 180 pounds of water into steam, you’re increasing the volume by a factor of around 1,000. Imagine if the room the target was in suddenly found itself loaded with 1,000 more people. The pressure will blow the hull apart. While a blaster will simply poke a hole in the target, maybe burning their clothes.

Star Trek always made the result of someone getting vaporized pretty… well, sterile. Zap, bright light, gone. But it wouldn’t be like that. If you want to know what someone getting phasered at full power would look like, YouTube provides. Behold the phenomenon of the “Arc Flash,” where enough electrical energy can be dumped into a human to convert said human into a steam explosion. Obviously, this might be considered slightly grisly, so gather the kids around (occurs at 1:14; you can adjust settings to .25 speed to watch the guy go from “normal” to “Hey, he’s a glowing blob, just like in Star Trek” to “Where’d he go?” in three frames):

It’s kinda unclear just what the hell happened here, but it sure looks like the guy was converted into mostly a cloud and a bit of a spray. In any event, there’s no missing the fact that something really quite energetic happened to the guy. The captain of the Klingon scout vessel vaporizes one of his crew on the bridge, they’re going to be scrubbing it down for days, assuming that the steam and overpressure doesn’t kill everyone else on the bridge.

In the later Star Trek series, the “vaporize” setting seemed to fall out of fashion. More often than not energy weapons were used as “simple blasters” of roughly firearm-power. And that’s all you need. Firearms are as powerful as they are because that’s Good Enough. You don’t need a weapon that essentially turns the target into a suicide bomber.

It might be interesting to actually show accurate phasering on some future Star Trek movie or episode. In one scene, out heroes board a wrecked space station. They go in a room where someone was shot with a phaser set to Blaster Mode: the doctor rushes over, applies hand to carotid artery, looks up sadly and says “He’s dead.” Then they go to the next room, where someone was vaporized. All the furniture is smashed up against the walls; the floor, ceiling, walls, furniture are all covered in gore. Blood sprayed everywhere, teeth embedded in the ceiling, small bits of burnt, semi-burnt and unburnt eviscera scattered about, bits dripping from the ceiling. Doc stands there in the door, slack jawed; Ensign Redshirt looks in and promptly doubles over and upchucks the Tribble Surprise he had for lunch. Captain Hero looks looks in, turns a shade of green and asks “So, Doc, who was it?”

Doc looks at Captain Hero like he’s a freakin’ mo-ron and replies with something like “How the hell would I know?”


What will the laser pistol look like?

The laser weapon will probably end up looking something like a camcorder, with a big lens that the beam goes through, and a fairly compact design. Since mirrors and internal optics can bend the beam inside the weapon, there is no need for the long barrels you see on modern firearms. Cooling, if necessary, would probably not involve fins - I would expect something more like the radiator on modern automobiles. Remember, shedding your heat through contact with the air is much more efficient than radiation.

(ed note: keeping in mind that using contact with the air doesn't work if there is no air, i.e., in vacuum. C. James Huff notes that there is one kind of fin for radiant cooling and another for air cooling. He mentions that the fins on a CPU hot sink is a good example of the latter. For a vacuum rated laser he recommends a compressed or liquified gas cartridge since a radiant cooler would be inconveniently huge.)

Also, lasers are getting surprisingly efficient. When each beam pulse contains no more energy than imparted to a rifle bullet, lasers might need cooling no more than a modern rifle.

Luke Campbell

Luke Campbell

The aperture is a 6 cm window protecting a 6 cm lens. Below the main lens is a secondary beam path for close focus attacks (close than ~1m). My conception when designing this thing was that the laser was a phase locked semiconductor laser near the butt of the stock, the large opening in the rear is for the cooling fan to force air past the cooling fins of the laser block (the model actually has all the fan blades, but they don't show up in the renders). And just because we all want to be able to "set lasers to stun," there is a pair of alternate beam paths on either side of the secondary beam path that can emit paired self-focused light filaments that will conduct a taser-like current.

Luke Campbell

...The side vents blow hot air (hot, not red hot)... I was illustrating some equipment from a role-playing setting I've been developing...

These are pulsed lasers of the "blaster" variety, which emit rapid bursts of ultra-short pulses to drill through their targets. They primarily emit in the near infrared at around 1 micron wavelength, but can frequency double their beam color to green if desired. All these lasers are 50% efficient at turning electric energy into beam energy. The beam parameters are fairly flexible — they can emit lower energy beams for a higher sustained rate of fire, for example.

The battle laser is a heavy hitting weapon designed as an infantry longarm to emit high energy beams for light anti-armor and anti-personnel roles, although it is also popular with sportsmen hunting large game. The beam energy is 10 kJ per shot, made up of 50 pulses of 200 J each, spaced 10 microsecond apart. This puts each pulse in the range of a big firecracker. The total beam energy is about the same as a .460 Weatherby magnum bullet — a bullet for the Weatherby elephant gun and the most powerful sporting cartridge in existence.

It can sustain a rate of fire of up to 2 full energy pulses per second, or safely handle overheating by up to 8 full energy shots. It has a mass of 4.5 kg and a 6 cm primary aperture. The beam causes full damage out to about 350 meters. It is commonly powered by a 1.7 kg high capacity power pack, with enough energy for 100 full energy shots and enough power to supply 2 full energy shots per second, although the laser can be hooked to a power backpack via a power cable to allow higher rates of fire and ammunition capacity. 6 cm lens.

(ed note: if my slide rule is not lying to me, 50 pulses at 10 microseconds per pulse will take 0.0005 seconds. 10 kilojoules in 0.0005 seconds is equivalent to 20 megawatts)

The Sniper Laser variant has a larger aperture for accuracy at a greater distance.

Luke Campbell

The assault laser is designed as a rapid fire anti-personnel infantry weapon. It emits lower energy beams than the battle laser, but has beefed up cooling and power supply systems to allow a greater time averaged power. The beam energy is 4.8 kJ per shot, with a sustained fire rate of 5 full energy beams per second, and can safely handle up to an additional 14 full energy beams worth of overheating. Its mass is 4.5 kg and it has a 6 cm aperture. It has an effective range out to about 250 meters. It is commonly equipped with a 2 kg high capacity power pack, with enough energy for 250 full energy shots and a power sufficient to supply 5 full energy shots per second, although again it can hook into a power cord to attach to a larger power pack for greater ammunition capacity and rate of fire. 6 cm lens.

Luke Campbell

The heavy laser pistol is a bulky handgun for heavy hitting stopping power. The beam energy is 3.2 kJ, with a sustained fire rate of 2 shots per second and a safe overheating reserve of up to 8 shots. It masses 1.25 kg and has a 3 cm aperture. It can keep a tight focus for full beam effect out to about 100 meters. It is commonly powered by a 0.24 kg fast discharge power pack fit into the grip. This can supply the laser with 15 full energy shots and 3 full energy shots per second. Alternately, the laser can be attached to a larger power pack worn on the belt or as a backpack for greater ammunition capacity. 3 cm lens.

(looks like a common civil camera) It's a case of convergent evolution. Both are designed to direct and focus light.

Luke Campbell

The medium laser pistol is a common self-defense and law enforcement sidearm. It has a beam energy of 1.6 kJ, with a sustained rate of fire of 2 shots per second and a safe overheating reserve of up to 8 shots. The mass is 0.65 kg and it has a 2 cm primary aperture. The effective focus range is around 50 meters. A 0.2 kg fast discharge power pack fits into the grip, which can supply the pistol with 25 shots at up to 5 shots per second. 2 cm lens.

The Auto Laser emits lower energy beams than the medium laser pistol, but has beefed up cooling and power supply systems to allow a greater time averaged power.

Luke Campbell

The light laser pistol is a compact sidearm for concealed carry. Its beam energy is 1.2 kJ, consisting of 60 pulses of 20 J each spaced 4 microseconds apart. It has a sustained rate of fire of 2 shots per second and a safe overheating margin of 8 shots. It masses 0.45 kg and has a 1.5 cm primary aperture. The effective focal range is around 30 meters. It is commonly powered by a 0.15 kg power pack in the grip, which gives 25 full power shots at up to 5 per second. 1.5 cm lens.

(ed note: if my slide rule is not lying to me, 60 pulses at 4 microseconds per pulse will take 0.00024 seconds. 1.2 kilojoules in 0.00024 seconds is equivalent to 5 megawatts)

Luke Campbell

Soviet Laser Pistol

Ah! The infamous Soviet Laser Pistol!

Details are sketchy but apparently it is not a hoax, it was a prototype, it was meant for Soviet cosmonauts to defend themselves, and it didn't work very well. The prototype was created in 1984. The project leader was Professor Major-General Victor Samsonovich Sulakvelidze, assisted by B. N. Duvanov, A. V. Simonov, L. I. Avakyants, and V. V. Gorev. Currently it is on display at the Museum of Military Academy RVSN (the project site), where it is the most popular exhibit. Many of the visitors ask if they can hold it.

The weapon was intended for cosmonauts to ward off attacks from evil American astronauts, and was to have a mass no greater than a conventional army sidearm. It is unclear why they started with a laser. Probably they were either concerned about the recoil from a conventional slugthrower in free-fall, or they wanted to demonstrate the superior technology of Mother Russia. Officially it was a "self-defense" weapon.

Naturally they ran full-tilt into the power supply problem. Apparently they dealt with this by specifying the weapon did not need a beam hot enough to actually cut through the aluminum hull of an evil American spacecraft. It would be acceptable if the weapon was just strong enough to permanently blind American astronauts or burn out American optical sensors. A drastic lowering of the power requirements. This is because both eyeballs and optical sensors obligingly contain lenses which focus the weak diffuse laser beam into a destroying hot spot right where it will do the most damage. However, if the laser bolt was actually strong enough to poke a hole in an American spacesuit, that would be great.

Ostensibly it used the same basic design as the old mark one, mod zero Ruby Laser. A solid rod of lasing medium inside an optical resonator is pumped by intense light. The ruby laser used a flashtube much like a camera strobe to pump the ruby rod. However Soviet laser pistol instead used a magazine full of pyrotechnic flashbulb "bullets". Flashtubes require lots of electrical power, a flashbulb just needs a spark to set it off.

When a bulb was ignited, the intense light would pump the pistol's neodymium-doped yttrium aluminium garnet rod, creating a near infrared laser beam (1064 nm). The two ends of the rod were mirror plated to create the optical resonator. If I a reading the Russian translations properly, there was a later design replacing the garnet rod with fiber optics (30 micron diameter each, 300 to 1000 fibers) doped with neodymium.

The flashbulbs were full of oxygen and zirconium foil/powder, plus a metal salt to tune the emitted light to the best pumping frequency. Each bulb is ignited by an electric spark (from a piezo-electric device in the pistol, attached to a rail under the barrel) passing through a tungsten-rhenium filament coated with a combustible paste. It burns about 5 milliseconds at 4733 Kelvin (4460° C). Burning zirconium emits about three times as much light as burning magnesium. In all likelihood after each shot a bolt action was used to eject the spent bulb and to chamber a fresh one from the magazine. The weapon is not automatic, each new flashbulb much be chambered manually. The flashbulbs are non-toxic and not prone to spontaneously detonate, which was another requirement.

The magazine contained eight flashbulbs, each 10mm in diameter. Each laser bolt contained something between one and ten joules of energy (about the same as a BB gun), and had an effective range of 20 meters. The pistol had a length of 180 millimeters.

The conversion of the Soviet defense industry caused the project to be cancelled. There was some talk about altering it into some sort of medical tool, but nothing ever came of it.

Particle Beam

Particle Beam Weapons uses a high-energy beam of atomic or subatomic particles to damage the target by disrupting its atomic and/or molecular structure.

Their minor draw-back is the fact that each shot you fired would have the side effect of exposing you to a lethal dose of radiation. At least if you were standing inside an atmosphere when you pulled the trigger. This is because of backscatter and Bremsstrahlung.

But other than that they would be quite spectacular weapons.

You see, in the vacuum of space there is nothing to impede the high-energy beam of particles from expending all their deadly energy on your target. But firing a particle beam through an atmosphere is like sending a load of red-hot buckshot through a room full of dynamite. When you are standing inside the room.

The high-energy particles start ricocheting off air molecules like a radioactive pinball machine. This is called backscatter. Quite a bit of it will reflect back and hit you, the weapon wielder. Not enough to blow a hole in you, but more than enough to give you radiation sickness. This is because a significant part of the backscatter is happening a few centimeters in front of the gun muzzle, which means it is happening one arm-length plus a few centimeters away from your vulnerable pink body. Less if you are firing from the hip.

And then there is Bremsstrahlung. When a charged charged particle (like, say, in a particle beam weapon) is decelerated by another charged particle (like, say, a proton in an air molecule) the lost kinetic energy turns into electromagnetic radiation. At this point medical technicians are blanching as they recognize the mechanism used in an x-ray tube, creating useful but deadly x-rays. Again, a significant part of the Bremsstrahlung occurring one arm-length plus a few centimeters away from your vulnerable pink body.

The problem with particle beams is that scattered radiation from the beam will irradiate the person firing the gun. When you are throwing around kilojoules of ionizing radiation, this will be enough to cause radiation burns, radiation sickness, sterility, and possibly cancer and genetic damage.

At kilojoule levels in air the backscatter isn't terribly bad; these would be very high-energy electrons, which tends to collimate the scattered radiation in the forward direction. Particle-beam artillery would be another matter, of course.

Dr. Schilling

Dr. Schilling mentions above that the conventional way to generate particle beams are with pulsed linear induction accelerators, but these will be difficult to reduce to pistol size. A more radical method of creating particle beams is with wake field accelerators, which produce electron beams on the electric fields of forced plasma waves.

He also mentions that high-current electron beams tend to be self-focusing in air, which simplifies things if you take that route. For ranges much over a hundred meters you have to start worrying about energy loss, which can probably be dealt with. For handguns, it isn't a problem.

You'll need a bit over a kilojoule of output energy to reliably incapacitate a human target, just like lasers. Unlike lasers, you won't have to pulse the beam, just pour it on in one big bolt.

Luke Campbell and Anthony Jackson got into a discussion of this. Alas it is over my head like a cirrus cloud.

Semantically, "particle beam" usually means the things being shot out the end can be treated as individual particles, without too much interaction. "Plasma" usually has significant inter-particle interactions.

Practically, particle beams fire a stream of relativistic atoms or sub-atomic particles. These are beams of ionizing radiation — you know, the stuff the anti-nuke crowd gets so worked up about.

If you get a particle beam intense enough to burn someone, it will also deliver a lethal dose of radiation from a hit anywhere on the body while it is at it. Radiation will scatter from the beam "impact" site, irradiating things around it. In an atmosphere, radiation will scatter off air molecules to irradiate things near the beam. Some of it will backscatter, irradiating whatever fires the gun. Forget about a sci-fi hero using a particle beam "blaster" — after blasting a hoard of bug eyed space aliens, he'd be sick or dying from radiation poisoning. In real life, particle beam weapons were considered for their ability to use radiation to disable things (mostly ICBMs) without necessarily blowing holes in them.

Using real tech, there are only two types of particle beams to worry about: electron beams and neutral particle beams. Electron beams are nice because relativistic electrons can get through about half a kilometer to a kilometer of air before either being brought to a stop by collisions with air molecules or (for higher energies) colliding with an air molecule and disintegrating both into an uncollimated shower of radiation. They also exhibit a self focusing effect in air - their interaction with the air concentrates the beam to prevent it from spreading out (this is quite important - since electrons are so much lighter than air molecules, they tend to bounce all over the place if shot out in low quantities - hit a molecules and your electron can end up going in any direction). Note that just because the beam is self focusing, it does not necessarily keep going in the same direction - I've heard humerous stories by observers of atmospheric high power particle beam tests of the beams wandering off in random directions. Some sort of beam guiding mechanism would be necessary (perhaps use one of those self focusing ultrashort laser pulses to ionize a path).

Electron beams don't work at all well in space, since the like charge of the electrons tends to blow the beam apart. Also, the charged electrons tend to interact in wonky ways with the earth's magnetic field, leading to unpredictable beam paths. Hence the neutral particle beams. Here, you accelerate an atom stripped of one or more electrons, and then neutralize the atom before shooting it off into space. Since all the particles are uncharged, they ignore magnetic fields and each other, and just merrily drift along until they slam into their target at relativistic velocities. They are pretty useless in air - the collisions with air molecules either stop the beam within a few meters or disintegrate it into an unfocused shower of radiation.

Apparently an electron particle beam would resemble a lightning bolt.

(Jason: "For an idea of an electron beam path... Look at lightning, which If I'm reading right sounds about the same")

Not exactly, but close, unless you have some sort of beamguide. If you create an ionized path with a laser, the electron beam will tend to follow that path.

Actually, that's true of lightning as well. this shows images of an electric discharge done normally and with a beam path created by a femtosecond-terawatt laser.

The shot will basically look like a straight lightning bolt (blue-white flash with extremely short duration), and will produce a snap of sound, though at the power levels proposed it won't be very loud; probably rifle bullet level.

The wound won't be all that visible, but will seem peculiar as compared to a bullet wound, since the skin will not be pushed inwards and may actually be pushed outward. It's possible that the skin will not even be visibly punctured, just blackened in a spot (depends how focused the beam actually is, which is unclear). Any tissue near the impact site will be dead or dying, and nervous system operation will be disrupted (stuff near the beam may absorb 100,000 rads or more).

I'm not sure how well it will penetrate flesh; electrons will go a couple inches in, and secondary X-rays (and, most likely, gamma rays from positron annihilation — very high voltages are required, meaning you get pair production of electrons and positrons) will go a bit forward of that, further penetration is dependent on the ability to open a hole in tissue and/or fully ionize the flesh.

Anthony Jackson

The CSDA (continuous slowing down approximation) range of a 1 GeV electron in skeletal muscle tissue is close to one meter - lower energy electrons will travel less far. This means it is quite possible for the burn path to completely transfix the target. It is also useful to note that the energy deposited per unit length (or volume) is highest near the end of the track when the electrons are moving slower. For a beam that penetrated, say, 10 cm into tissue, this would mean that you could have a narrow burn entrance wound without a visible hole but get significant flash vaporization of tissue inside the victim.

That same 1 GeV electron will travel over 800 meters through dry air at sea level in the CSDA. If you are shooting at distant targets, however, keep in mind that the electrons in the beam will have lower energy the more air they have to punch through, and thus will have lower penetration at the target.

Data is taken from ESTAR

We're talking a pistol here. It's probably 10-100 MeV, for a penetration of a couple of inches.

Anthony Jackson

Mr. Andrew Broeker has some issues with Mr. Campbell's approximations:

My first concern regards Luke Campbell's use of the CSDA approximation to calculate electron penetration depth. This approximation should only be used for very thin targets where only a small fraction of incident particles' energy will be lost traveling through the sample. Since the discussion regard's the loss of all energy, more math gets involved. I've done similar calculations in my lab work and would be happy to do so again if Luke could provide me with the ESTAR data he used to do this.

My second concern is Luke's suggestion that weaponized electron beams should be a micron in width. While he is correct that modern accelerators can achieve such narrow beams, they can do so only via collimation. To achieve such beam diameters, up to 99% of your beam ends up getting dumped on your collimators. This has two consequences. First, drastically reduced beam current. Second, the operator gets irradiated far worse than his target.

Andrew J. Broeker

With realistic breakdown voltages around 10 to 20 MV/m, a 10 MeV pistol would be half a meter to a meter long. Given additional engineering considerations, for realistic electron beam pistols I wouldn't expect more than 1 to 2 MeV, maybe 5 MeV at the limit. The ranges in skeletal muscle: 1 MeV - 0.5 cm, 2 MeV - 1 cm, 5 MeV - 2.5 cm. Multiply by 800 for the range in air. Unless you consider non-linear beam-matter interactions (such as heating a tunnel to a partial vacuum) this gives very short ranges in air (4 to 20 m), and you would need to use multiple pulses to blast a deep enough hole to reach vital organs.

If you want better performance out of a pistol sized device for a sci-fi setting, you need to postulate a Sufficiently Clever method to get around the breakdown voltage limit. Once you do this, there's no obvious upper limit on the available electron energy.

It's a problem, though I'm not sure how many MeV you really need (my research-fu is failing me). As a practical issue, going above 10 MeV is of limited value for penetrating armor, but may have value for enhancing range.

I found some interesting studies, that were above my head, last time I looked into this. I can't find any of them right now, but I recall a need for a fairly high voltage, a very high current, and a very clean beam, to maximize atmospheric propagation. Key terms might be Nordsieck length and hose instabilities.

Some things I found that seem vaguely promising/related, though they're generally abstracts and often aren't articles I can get at or really understand if I did read them.

This PDF (ed note: Chapter 12 of Charged Particle Beams by Stanley Humphries) seems to contain useful information that I'm not particularly good at parsing; see section 12.9 in particular.

Two other links, more historical: link1 link2

Anthony Jackson

This looks useful. It indicates there are two range-limiting effects.

The first is the loss of energy of the beam electrons due to ionization of the air molecules. The other is the spread of the beam due to collisions of the electrons with air molecules causing random changes in direction to the electrons. Magnetic self pinching allows the beam to recover somewhat from the scattering beam spread, but not entirely.

One necessary value for analyzing electron beam range due to scattering is the Alfven current, denoted I_A. This is the current at which the magnetic self focusing overcompensates and causes some of the beam electrons to turn around and move in the opposite direction.

It is the upper limit on the current of an electron beam (with the caveat that the limit is for the net current - for rapid rise times, magnetic induction can cause plasma electrons to move backwards along the beam, partially canceling the beam current and allowing more beam electrons to pass by before the limit is reached).

For electrons, this limiting current is

I_A = 17E3 amperes * β * γ

where β = velocity / (speed of light) and γ = 1 / sqrt(1 - β2) is the usual relativistic parameter.

The other necessary value is the increase to the spread of the beam due to scattering per unit length traveled, neglecting magnetic self focusing. For dry nitrogen with at atom density (in particles per cubic meter) of N this value is

d(θ2) / dz = 1.04 meters2 * N / (γ2 * β4)

At STP this becomes

d(θ2) / dz = 2.8 / (γ2 * β4) m-1

If we neglect energy loss of the electrons, the beam spread can be determined analytically. For a beam of current I and initial radius R_0, the Nordsiek equation gives the spread of the beam with distance

R(z) = R_0 exp[(d(θ2) / dz) * z / (2(I/I_A))] = R_0 exp[ z / z_0]

In other words, we get an exponential increase in beam radius over a characteristic range equal to

z_0 = 2I / (I_A * d(θ2) / dz))

As an example, let us look at a beam of 10 MeV electrons with a current of 5000 amperes in dry nitrogen at STP.

I_A = 34E4 amperes

d(θ2) / dz = 0.007 m-1

z_0 = 4.2 meters

For the electron energy loss range in dry nitrogen, I get 44 meters from this reference. This indicates that our original assumption of neglecting the energy loss in finding the beam expansion is probably fine for a a multiple of z_0 or two.

One consequence of this is that electron beams in air will tend to have very short pulses of high current to maximize the self focusing in order to cancel collisional spreading. Unfortunately, this can hinder heating an evacuated tunnel through the air, since for very rapid pulses the air atoms will not have time to move out of the way of the electron beam.

17e3 = 17,000, correct? For relativistic electrons we can probably safely approximate β as 1 and γ as 2 * energy in MeV.

θ is what here? Rate of expansion?

It appears we want a current fairly close to I_A; go up to 50,000 amperes and z_0 is now 42 meters.

I suspect this range will change as ionization occurs, assuming the electron beam energy is adequate to cause substantial ionization.

Let's assume a pulse with an initial diameter of 2mm and a current of 50,000 amperes. That's a peak magnetic field of 5 tesla, which is high but not completely out of the believable range, at least as compared to everything else involved. We have a peak current here of 5e11W, putting us just shy of a terawatt. Now, sustain the pulse for 1 nanosecond, thus depositing 500J in the channel.

The channel has a base cross-section of 3.14e-6 m2 and a maximum cross-section of four times that, and a length of 40 meters, so figure total volume is about 4e-4 cubic meters, resulting in heating up about half a gram of matter. 500J / 0.5g = 1 MJ/kg, which is less than the ionization energy of the gas, but is sufficient to heat it up to around 1300K (assuming temperature stabilized) and give an average velocity to the gas of 1400 m/s. It will take about one microsecond for gas to evacuate the channel.

Now, the evacuated channel is maybe 1/4 the density. That will increase the range of electrons by a factor of 4, and also reduces N (and thus d(θ2) / dz) by a factor of 4, which will also increase the nordsieck length. This means the initial 40 meters are only as costly as 10 meters normally, and thus we can tunnel another 30 meters. Rinse and repeat; the theoretical limit is 160 meters.

This, of course, ignores problems with the channel formation: much of the deposited energy may be radiated away rather than turning into thermal movement of molecules, and the shockwave from the initial pulse is going to bounce back as it hits nearby molecules.

Now, lets say our beam hits a human, with a cross section of 5 square millimeters when it hits, and we'll assume a penetration depth of 5 cm2, for a total affected volume of 0.25 cubic centimeters, or 2,000J/cm3. Assuming the volume is mostly water, water has a specific heat of 4.18J/cm3, so we flash-heat the water from 37C to 515C. This puts it well above vaporization temperature, and in fact well above its triple point, so it starts to expand, cooling as it does so. In theory, up to 77% of the liquid could turn to vapor; in practice, I suspect the actual amount is somewhat less, due to energy being lost from breaking chemical bonds, secondary X-rays spreading beyond the impact area, and energy loss on contact with nearby flesh.

Interestingly enough, if the cross section reaches 38 square millimeters (about a 7mm wide beam) it will no longer vaporize flesh at all, which means it would produce a charred spot and little other visual effect, though anything in the beam path is dead. Of course, the direct damage may not mean much; 5 cm penetration isn't really enough to kill anything (I'm not sure how the secondary X-rays will be distributed, or what energy level they're at, but the secondary radiation may be quite adequate to disrupt the nervous system). Again, secondary pulses on a microsecond time scale may allow tunneling through matter, as long as the power density of the initial pulse was adequate to cause vaporization.

I suspect this range will change as ionization occurs, assuming the electron beam energy is adequate to cause substantial ionization.

Anthony Jackson

I suspect you are correct. At 10 MeV collisional losses dominate, and if you don't lose energy to ionizing the air molecules the energy loss drops by quite a lot. At higher energies you get radiative losses beginning to dominate, and this will not change with increasing ionization. Note that for a beam burning away an evacuated tunnel for it to travel through, we want to have mainly collisional losses - radiative losses take the form of x-rays which can travel several mm or cm through air and thus do not contribute to heating up the volume of air the beam will travel through.

Let's assume a pulse with an initial diameter of 2mm and a current of 50,000 amperes.

Anthony Jackson

I don't see any real reason not to make the beam very narrow, say a micron in width or so. We seem to be able to generate micron width beams with modern accelerators.

We have a peak current here of 5e11W, putting us just shy of a terawatt. Now, sustain the pulse for 1 nanosecond, thus depositing 500J in the channel.

Anthony Jackson

Complicating this analysis is that the energy deposited increases as the electron energy decreases. However, the energy loss per unit length is roughly constant from 10 MeV to 1 MeV, so this is probably not too significant in this energy range.

Plasma Weapons

Silly as they are, plasma weapons are a popular SF concept that just won't go away. They are encountered in such diverse places as the original Star Trek TV series, the Traveler role playing game, and the Babylon 5 TV series. They play the role of a futuristic flame-thrower.

Their main draw-back is that they won't work.

Plasma is the so-called "fourth state of matter", and is basically hot air. That is, it is a gas heated to temperatures comparable to the interior of a star or the center of a thermonuclear explosion so that all the atoms are ionized. Unfortunately, according to the virial theorem, the plasma wants to equalize its internal pressure with the external, i.e., it wants to expand into a diffuse cloud of nothing.

Note that another term for "gas heated to temperatures to the interior of a star" is "explosion". As in "thermonuclear explosion occuring at the tip of the gun muzzle, enveloping the shooter and vaporizing them". has a nice in-depth article detailing all the reasons why plasma weapons are the most stupid weapon concept ever invented since the smoke-ring gun. High points from the article:

  • Plasma ions in a plasma bolt are moving at high velocity in all directions. So at least half of them will move away from the target. Would it not make more sense to have all the ions moving towards the target, as in, say, a particle beam weapon?
  • Since the plasma bolt is basically a traveling explosion, if it takes more than a thousandth of a second for the bolt to travel from the sidearm to the target, by time the bolt arrives it will have dissipated into a warm breeze.
  • "OK, fine", you say. "How about containing the plasma bolt?" Well, now your problem is to somehow make a handwavium force field to enclose the traveling explosion. Such a field must be thousands of times stronger than steel, self-sustaining, yet somehow brittle enough to shatter when it hits the target. And you still have the problem that half of the ions will be worthlessly traveling away from the target.
  • Not to mention the fact that if you can make such a handwavium force field, nothing is preventing the enemy from using the same technology to make defensive force fields capable of protecting their soldiers from exploding plasmas.

To me, the logical solution is to generate the plasma at the target, not at the sidearm. Congratulations, you've just invented a sidearm firing bullets with miniature thermonuclear warheads.

Plasma guns have a significant problem. If the plasma is at higher pressure than the surrounding air, it expands and pushes the air out of the way, becoming a cloud rather than a beam or pulse. Clouds of lightweight gas (a plasma is essentially a gas with wierd interactions with electric and magentic fields) are quickly stopped by air pressure, and will cool quickly as well. If it is at really high pressure, it will expand violently - this is what we call an explosion. Trying to confine the plasma with electric or magnetic fields just makes things worse. In order to get the fields to travel with the plasma and contain it, they need to be generated by sources within the plasma (generally electric currents generating magnetic fields). The forces exerted by the fields on the sources either helps to explode the plasma (for magnetic fields and electric currents) or squishes the plasma in one direction while helping it to explode in another (for electric fields and macroscopic electric charges).

So, we need to keep the pressure down. Ignoring electric and magnetic fields, we find that the pressure is given by a constant times the temperature times the density. The temperature is necessarily high (there are cold plasmas, but what's the point as a weapon?), so we need low density. Unfortunately, low density means low energy per volume (it turns out that the energy per unit volume is given by the pressure - you can't win by playing with combinations of higher temp and lower density or vice versa). As a result, you need to squirt out a large volume of hot, low density plasma to deliver much energy to your target. You can do this by squirting out a stream of it really fast. You don't have a "pulse" or "beam" of plasma this way, you have a plume (or, equivalently, a jet). You train your jet on your target and hold it there for long enough to burn through. This is sort of a very energy intensive flame thrower with the disadvantage that your target is not covered with sticky, burning chemicals after you take the jet off him (as an idea of how energy intensive, if you can direct the beam only onto the person's skin, about half a megajoule is needed to cause lethal burn injuries involving third degree burns to exposed skin, second degree burns under light clothes, and ignition of hair and clothes. In practice, more energy will be required because the jet will not all impact your target. Compare this to the energy of an assault rifle bullet [500 times less] or an arrow [10,000 times less] for an idea of why plasma guns will not be used - the same energy could propell 500 coilgun projectiles, each highly lethal and much more penetrating).

Backscatter Protection

In science fiction, some weapons could harm the person firing the weapon.

Particle beam weapons when fired inside an atmosphere can backscatter deadly radiation in all directions, including right back at you.

Any weapon which vaporizes your target is converting your opponent's body into an exploding bomb, which you are standing dangerously close to.

The idea is that it would be handy if your weapon had a build-in shield to protect you.

A minor problem is bulk and size added to the weapon, think about how awkward it is to carry around an opened umbrella.

A more pressing problem is how do you see where to aim with that blasted shield in the way? A reflex aimsight would be an excellent solution. Failing that, a peep-hole might help, peering through a thick block of leaded quartz or something.


Disintegrator Ray: Without the later trappings of safety and convenience. The beams used really do vaporize their targets, with all the attendant thermodynamics, so best wear a shielded suit when firing unless you want your front half to be blackened cajun-style.

Kim Kinnison fires his DeLameters while unarmoured on several occasions, and it's hinted that its ancestor, the Lewiston, can also be fired by an unprotected user. The Semi-portable projectors, on the other hand...

(ed note: with semi-portables the person shooting the weapon shelters behind a large integral metal shield with a built-in force field, which the weapon muzzle sticks out of. In the novels the shield is ostensibly to protect you from hostile weapons fire.)

Hydramatic Mark 4 Flame gun

This is an example of 1953 space opera in those days of yore when technobabble was king and scientific accuracy was non-existent.

A. This is the Hydramatic Mark 4 Flame gun, which you see me toting with the space suit above. It was developed by Professor Maklin Devonport of the Interplanetary Research Institute in 1995. The Hyramatic takes its name frmo the fact that it operates on a liquid hydro-ammonal compound, which is contained in a cylinder and fed to the gun via a feed line, which couples onto the gun at (a). Its lethal range in space is 2,000 yards - a useful weapon.

B. This is the Atomatic. It is rather bulkier than the "Hydra" but it has the great advantage of being self-contained. It fires .20-calibre atomic bullets; of course a .20 bullet in the old days would have been just about useless, but these, having atomic heads, produce spectacular results. I once saw a pirate ship (which was attacking transports on the Earth-Mars run) torn completely apart by a burst from one of these atom guns. The burst had penetrated the hull and hit the power plant; the pirates never knew waht hit them!

C. Another type of atomic weapon, but working on the controlled-fission principle, the Radiumatic projects a concentrated radiation beam. Another "brain child" of our brilliant Professor Devonport, it is a much heavier weapon than the previous two, but proportionally more effective.

There is no recoil with this weapon or the flame gun and therefore great accuracy is obtainable.

The Radiumatic, when the front hand grip is removed and the tripod screwed into its place, is converted into an idea weapon for ground use - in positions of defense, for instance.

From Ron Turner's Space Ace pop up book (1953).

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