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