A treatise on Lasers in the Babylon 5 universe

DISCLAIMER: Someone may be tempted to respond something like

<Tongue in cheek>:

"But these are ALIENS. They may have some magical laser with a form of energy we don't know about."

<Tongue to normal>

This would be true, and this article would not apply, except that it will not be a laser. If it is a laser, we can describe it's properties.

DISCLAIMER 2: This gets heavy in places. Physicists will notice many gross simplifications and shortcuts, and maybe the occasional error.


First, lets talk about frequency, wavelength and energy. I recall a couple of posts that seemed to be referring to Lasers with similar frequencies but different wavelengths. Sorry, can't happen. The relationship between frequency and wavelength is fixed. A photon of frequency X will always have a wavelength Y, and for that matter, an energy Z. They are all just different ways of describing the same thing. Basically, the higher the frequency, the shorter the wavelength and the greater the energy.

How they work

I'm going to be very brief here. Interested parties can get a more detailed description from many sources. My main aim is to explain a few terms I will use later on. The key feature of lasers is _stimulated emission_. The requirement is a population of molecules or atoms at the correct energy state to emit a photon of frequency X. If struck by a photon of the correct frequency, the atom or molecule emits a photon of the same frequency, travelling in the same direction. We now have two photons where we previously had one. This process is called _laser gain_. However, a population of atoms will not all naturally be at the proper energy state at the same time. Instead, they will tend towards thermodynamic equilibrium, with more lower energy state atoms than higher state ones. The excess lower energy atoms will absorb photons rather than emitting them, and thus smother the photon emissions. To produce stimulated emission, we must somehow manufacture a population inversion, make the target energy state outnumber the lower energy state. Heat is no good, the preferred methods are electrical current, intense light or chemical reaction.

Types of laser

I make 5 broad 'types' of laser we should consider. We'll call them static, gas, free-electron, bomb-pumped and Nucleonic.

Static lasers

are what most people think of as a laser. The famous ruby laser is an example. They are called static because the lasing material, e.g. Ruby, is not used up, but continually pumped with energy to produce a population inversion. The lasing material need not be a solid and many subtypes of this laser exist. This laser may well be common in B5W.

Gas lasers

use chemical reactions to produce a population inversion. The gas is used up after every shot, vented and then must be replaced. The gases involved and the waste products are usually highly dangerous and/or toxic. No appreciable amount of energy is required. Do not confuse these with lasers such as the common Helium-Neon laser, which is a static laser using a gas for the lasing material. This type of laser does not seem to be used in B5Wars, except, maybe on the Hyach fighter.

Free electron lasers

use electro-magnetic fields to bend a beam of electrons. As they 'turn' they emit photons. The more the electrons are bent, the higher the frequency of the photons. This allows the laser to be tuned to a desired frequency. However, the probability of inducing stimulated emission varies with the cube of the desired frequency. That means the higher the frequency, the more difficult it is. Producing x- ray Lasers this way is hard. This is likely to be the most common type in B5W.

Bomb-pumped lasers

use a 'small' nuclear warhead in combination with lasing rods to produce an x-ray laser. They are one shot weapons not suited for use in anything other than a remote vehicle or missile (suprise). They do not appear to be used in B5Wars. A pity. Guess JMS didn't know about them.

Nucleonic lasers

are pretty new. They rely on manipulating the energy states of the nucleus of certain isotopes rather than the energy states of the electrons. They produce gamma-ray lasers. I have not been able to find a theoretical reference to it, but it seems to me a 'free neutron' laser might be possible. Laser emission from manipulating neutrons with an artificial gravity field.

Small piece of trivia. The atmosphere of Mars is a natural, non-coherent laser! (Static).

We should note that there are two further modes of operation to consider; continuous beam and pulse. Most B5W lasers should be pulse. This may sound wrong, but I'll explain why that isn't necessarily so later.

From this point on, we will only consider Static, free electron and 'free neutron' lasers, as these seem to be the only types in B5W.

Doing Damage

Lasers do damage by delivering large quantities of energy to the target. How much? Well, a 1/1000th second pulse of 2Mj per square cm will blow through one cm of steel, and is equivalent to about 12 ounces of TNT. Note that the area we apply the energy to is important. 2Mj per square metre might scorch cardboard. Pulse lasers are usually regarded as the best to use in weapons. This is because the initial strike of the laser causes material to explode off the target and this interferes with the beam, wasting energy. A series of pulses is more efficient as it means we do not fire at the times when most of the material is boiling off the target. A series of rapid pulses, maybe 100 a second works well. Note that this will _appear_ to be a beam. 25 frames a second is movie film speed. 100 a second cannot be seen as individual pulses. I propose that most B5W lasers are rapid pulse lasers. They only appear to be continuous beams. We will ignore the incontrovertible fact that they should not be visible at all.

Energy requirements

Simply put, the more energy we put in, the more we can deliver to the target. We do not of course get 100% efficiency, or even close. A good guess might be efficiencies of 20-50%, depending on the sophistication of the laser and it's makers. So how much energy is useful? We have established that 2Mj/cm^2 is good for punching through one cm of steel. If we pulse 100 times a second for 5 seconds, that's 1,000Mj, one Gj!! If we assume 25% efficiency, that's four Gj input required. That's the output of one of the largest power plants in the world IRL for four seconds!! Fortunately we don't have to provide that energy all at once, we can generate it gradually over time and store it in a capacitor. This fits very well with B5W RoF for lasers you note. If we charged up our capacitor for 100 seconds, we would only need a power output of 40MW to generate 4Gj in the time available. Of course, we need a damn good capacitor. Better than can be managed today IRL. A superconducting loop would be very good. Failing that some kind of homopolar generator, which is one of the flywheel energy storage devices. Last I looked, 1 tonne of homopolar generator would hold about 4Gj. In the B5 universe they are doubtless much more efficient, but there will still be limits. Capacitor technology and lack of superconductors will be one of the things that prevents races from fielding certain weapons.

Homopolar generators and superconducting loops

These are both advanced capacitors. Homopolar generators are available now IRL. They store energy in a rotating mass, usually a flywheel. When a charge is passed through, the flywheel slows rapidly, converting energy to electricity in a powerful discharge. Superconducting loops are a loop of superconductive material (well fancy that). They are available now IRL, but require extremely low temperatures to function. The properties of superconductors allow them to store vast amounts of energy with no loss, and for this energy to be quickly and efficiently charged or discharged from the loop. The development of room temperature superconductors will make these the storage medium of choice.

Hitting the target

It's all done with computers! If we know where the target is, and it's current relative velocity, our computers can calculate where to aim the laser to hit; and it will hit. The calculations required are trivial, we just need to be able to aim the beam with the required accuracy; which

can be tricky. What if the target is evading? A jinking Starfury say. Sadly, this is a waste of time. A laser pulse travels at 3*10^8 meters per second, or 300,000 km a second if you prefer. If our Starfury can jink at 12G, and is 1000km away, in the time it takes our laser to reach it, it can have altered its position by... wait for it.... 0.7 mm!!! Wow!! That's really going to induce a miss isn't it? It is a sad fact that if you can aim your laser with sufficient accuracy, no target capable of holding a man sized crewman can evade at less than about 10,000 km! So it's that easy? Well there a few complications. To go back to our Starfury, let's say it is travelling at a relative velocity of 3,600 km/hour. That's 1000 metres a second. The pulse duration is 1/1000th of a second. During that time the fury moves 1 metre, while the pulse plays over it. So we don't get a spot 1 cm across, we get a line 1 cm across and 100 cm long. Oops! What happened to our 2Mj/cm^2? It is now 0.02Mj/cm^2. We might blister the paint. What can we do about this? Well, we need to move the laser during firing to compensate for the relative motion of the target. Tricky, but not for our computers. Note that jinking is a help here. The beam may not miss, but the random motion will cause at least some of their pulses to be diffused over a wider area reducing damage.

There is another complication. Vibration. The tiniest vibration effecting the firing laser will produce a wide divergence at the target at all but the closest ranges. A ship will have to take measures to limit the effects of the vibration of running machinery. A ship in combat taking damage will have large vibration problems. The more advanced races will have better techniques to compensate for vibration. Control of gravity will help enormously here. One thing I will point out. Mechanical traverse for our lasers is right out. Too much vibration, slow response time, and insufficient accuracy. The upshot is that your computer is your friend. Ivanova's performance aside, "Use The Farce Luke" is not an option.


This is where it gets really tricky. The problem is spot size. We think of lasers as a thin line that does not diffuse. Lasers beams do produce a larger spot, just like a torch however. It just takes a much longer range to observe the diffusion. How long a range and why does it matter?

It matters because the trick with a laser is to deliver as much energy as possible to a small area. Remember 2Mj/cm^2. If that nice damaging spot grows to a square metre, our laser is useless. We might still hit the target but it does no damage. We have to all intents and purposes missed.

The equation that governs this is:



I = intensity in Joules per square cm .

P = Discharge in Joules

L = Wavelength of laser in cm.

D = Focusing element diameter in cm.

R = Range in cm.

To break that down into useful English, the longer the range, the larger the spot. According to this formula, there are three ways to ensure adequate damage.

1. Use a wider focal array. Examination of the formula reveals that it has to be much wider. Lasers are thought of in SF (and B5) as gun barrels, but they are more likely to resemble searchlights or radar dishes. BIG radar dishes! There is another option. Gravity bends light. If one has gravity control, like the Minbari, we can use 'lenses' of gravity to focus the beam. This 'gravitic focusing' offers tremendous advantages.

2. Use a higher frequency laser, which tends to require a higher level of technology. As we said, X-rays are difficult.

3. Failing that, putting more power in allows us to still deliver enough energy to do damage even over the wider area, but that presents a capacitor problem.

Lets run a few examples through. For these examples we'll see what happens at a range of 500 km, to a discharge of 2 Mj.

For high frequency ultraviolet, wavelength about 10^-6 cm we find:

A focal array diameter of 1/2 a cm (laser rifle) can only deliver 200 j/cm^2.

A 50 cm array can deliver 2 Mj/cm^2.

This sounds good doesn't it. Half a metre doesn't sound that bad. We are however using a laser of the highest frequencies short of x-rays. Let switch down to lower frequency UV, just above visible light. Wavelength 10^-5 cm.

A focal array of 50cm can deliver 0.2 Mj/cm^2. OOPS!

A 200 cm array can deliver 3.2 Mj/cm^2. 2 metres, well still not bad. Don't be confused by 3.2 being higher than 2. It doesn't mean we have miraculously created energy from nowhere, only that we can hold the spot size down to _less_ than a square cm, if we wish to.

Finally, let's get to visible light. This is what the general public perceives as a real laser after all. How good are they.

Our 50 cm array can deliver 0.9 j/cm^2. Awful!!!

Even our 200 cm array can only manage 14 j/cm^2.

Lets go to 2000 cm, 20 metres. Nope, only 1.4 Kj/cm^2.

100 metres! It enormous, surely it'll work! 35.6 Kj/cm^2.

800 metres! Nearly a kilometre across. 2.3 Mj/cm^2. At last!

Low frequency sucks in space! Explains why only the laser mastering Hyach use the maser. Microwaves have a lower frequency than light. Don't be confused by the bouncing of lasers off the moon. In this case the energy density is not relevant and the spot size need not be very tight.


From the above, we can see that there are several areas where the technology level of the builder influences the capability of the laser. Further, much of the technology is fundamental, preventing its use by more primitive races. Let's look at some of these.


. All the lasers used in B5W use capacitors to store the energy needed to fire. Capacitors capable of holding the required energy can get very large. The development of room temperature superconductors is a big advance here as it makes higher discharge energies much more feasible. Note that contrary to the rules, large capacitors are dangerous! If overcharged, they explode. If damaged their capacity to hold charge is reduced, often to nearly zero. IRL, damage to a charged laser capacitor should be capable of causing explosions.

General efficiency.

The more efficiently a race can turn input energy into output discharge, the smaller the capacitors and energy point requirement needed to produce a set amount of damage. Again, use of superconductors is a big help here.

Vibration reduction

We have mentioned that vibration at the wrong time can cause our nice focused spots to be diffused to the point of uselessness. Vibration is the bane of lasers. The better the ability to compensate for it, the longer range the laser and the more reliable the damage. Gravitic technology affords a big advantage here.

Focal array technology

We have touched on how important this is when it comes to accuracy. There is another issue. Most focal arrays will require some kind of reflector, a mirror if you will. No mirror is 100% effective. Some small portion of the energy of the laser will be absorbed by the mirror. This will be dealt with, otherwise the heating caused will cause the mirror to lose it's reflective properties. Even a slight degradation will mean that the absorbed energy destroys the reflector. Cooling technology will be very important. Yet again, gravitic technology scores as gravitic lenses are not vulnerable in this way.

One thing you will note is that gravity manipulation is a massive advantage. So are room temperature superconductors. No accident then that the Centauri and Minbari have the best lasers, and that races with a more primitive technology base just cannot field these weapons.

Variable damage

Many have advanced the theory that laser damage is too variable and is unrealistic. We can now see that this is not necessarily so, as vibration and uncompensated movement of the target result in an unpredictable number of the pulses being diffused to the point they have reduced or no effect.

Raking Mode

This is fairly easy. The natural tendency of the pulse to strike different locations on the target is turned into an advantage by deliberately crawling the stream of pulses over the hull.

Sustained mode

Sustained mode is easy. All you need is a double (or more) size capacitor. Doubling the energy input, as B5W does, accounts for this perfectly. In reality, it would be possible to charge for a sustained shot in another way, doubling the charging time, but we will hand wave this. I cannot explain why some lasers have no sustain mode. (Well it's game balance).

Piercing mode

Piercing is a little trickier. The best model is that advanced (gravitic) focusing allows the pulses to be held on or around a point, counteracting the tendency for pulses to scatter about the hull. This allows the series of pulses to punch deep into the ship.


The Light and Medium lasers are most likely Static or primitive free electron lasers. This does not explain why they cannot be sustained. Without gravitic focussing, they cannot pierce.

The Heavy Laser may be a primitive Free electron laser, producing high ultraviolet or low x-ray frequencies. Without gravitic focusing, it cannot pierce. Enlarged capacitors allow it to sustain.

The Battle laser is likely an advanced free electron laser capable of high x-ray frequencies. It uses gravitic technology to bend the electrons to a sufficient degree. Gravitic technology also allows high accuracy with a combination of gravitic focusing, gravitic beam pointing and gravitic vibration compensation.

The Neutron Laser may be a 'Free Neutron Laser' capable of gamma Ray frequencies. Gravitic focusing allows it to pierce. Enlarged capacitors allow it to sustain. Gravitic technology gives it many of the same advantages as the Battle Laser.

The spinal laser is most likely an enormous free electron laser producing high frequency x-rays. No gravitic focusing. The fixed mount, and massive size are a consequence of using non-gravitic techniques to make this monster, and are just a bit beyond EA capabilities. I imagine superconductors are required for this.

The blast laser can be easily rationalised. Many have pointed out that instead of raking, it does standard damage and have advanced doubts as to the 'realism' of this. What if the blast laser fires a few large pulses rather than 500 smaller ones? We would tend to see damage caused

to one location on the ship, rather than a series of smaller explosions that we can track across the hull. Standard damage. I propose that the blast laser fires a small number of single pulses, it even accounts for the name, producing a single blast at the target rather than a chain of explosions. It is most likely a free electron laser.

The Pulse laser arrays most likely are the appropriate laser but share the capacitors and some fire control elements with a pulse cannon, hence the double barrels and associated maintenance problems.

The Maser, is a microwave frequency laser. As we all know, microwaves do not penetrate metal well, but fry electronics and flesh. (Think microwave oven). As a low frequency laser, it has a short range. I hope you now all see why I was so keen to get the name changed from 'Gamma Laser', as it isn't one.

The Combat Laser.

This appears to be a variant of the battle laser, optimised for piercing fire only.

The Ion Laser.

I'm a bit stuck on this one. Any ideas would be appreciated. My only thought is that if it were some kind of gas laser, the dangerous by products would help account for it's unpopularity.


Challenge Magazine (GDW), esp. #71.

JTAS Magazine (GDW).

Fire, Fusion & Steel 1st ed. (GDW).

GURPS: Vehicles 2nd ed. (SJG).

GURPS: Space 3rd ed. (SJG).

Guns! Guns! Guns! 3rd ed.

Striker 1st ed. (GDW).

2300AD (GDW).





My thanks to those that helped in the production of this document. You know who you are.