|
MadMcAl -> Weaponry in science fiction (11/4/2011 5:34:18 PM)
|
First, this is a direct response to Nedrear's post here.
I just don't want to clutter that thread with such a, while interesting, different discussion.
Now, Nedrear mad a interesting, if somewhat simple point.
I can't fully agree with him, but it is still at least way above the "well shoot it with the blaster"-approach (just for information, while I enjoyed the Star Wars films, books and games, I find the approach they take to the science part of scifi abhorrent).
Well, to bring Ned's (I hope it is all right to shorten the nick, if not, please pm me, and I will change it) points here, he saw basically 4 kinds of weapons in space fight.
1. Energy. From his description I think he meant direct energy weapons.
2. Heat weapons.
3. High density projectiles. The thing I normally call slug thrower.
4. Shock wave on high atmosphere fights.
Now my answer:
1. In direct energy you forgot the particle beams, that are neither coherent energy waves (LASER, MASER, GRASER and XRASER, where the ASER in each part stands for Amplification through Stimulated Emission of Radiaton, while the beginning 1 or 2 letters stand for Light, Microwave, Gamma Ray and X-Ray) nor does it belong to another group.
And just to disarm any "but that is not possible" arguments in the first spot, the particle beams already exist. They are just not weapons. Every particle accelerator, found in many high tech universities, physic labs, and of course CERN are exactly that. If you used to LHC of CERN to fire onto an armor plate instead of an experimental target you would get a severely damaged armor plate, if you can find its remains that is.
Like LASER-beams as weapon not usable ATM but a good starting point.
The damage factor of coherent electro-magnetic wave-beams (LASERs and all the other shebang I mentioned above) depends on different factors. The first and most important is the energy density at the target. As beams are not parallel but as a rule gaussian (wiki explains gaussian beams) this is THE reason why beam weapons actually have a maximum range The farther out the target is, the bigger the radius of the beam becomes. And if you double the radius of the beam, you quadruple the area of the beam, while leaving the over all energy of the beam the same. Or, in other words, you have to spread the same amount of butter over 4 times the bread.
At some time you get nothing more done than an very expensive (but long ranged) tanning booth.
The reason why there is more than just LASER's in this category is that the shorter the wavelength of the beam is, the longer is the Rayleigh length (meaning the distance from the "gun" to the point where the beam is the smallest diameter). the Rayleigh length is so important because 2 times the RL, the energy density, and such the damage, is the same as directly at the gun. And all in between it gets actually stronger. But after the 2 times the RL the diameter grows rather hard (if wished I can actually bring the math on, but only if wished).
The other major factor working on the RL is actually the aperture of the "gun" (or caliber if you want it easy).
In another discussion I actually calculated the RL of a GRASER (with a wavelength of 5 picometer) and a caliber of 1.5m. The result was... interesting.
Apparently such a GRASER has a Rayleigh length measured in astronomical units.
Or in other words, the point where the GRASER has the highest energy density is, when fired from Earth somewhere around Jupiter.
The range where there is no damage degradation is somewhere around Saturn.
The range where it has still a major amount of its damage is way beyond Neptune (with this GRASER you could actually light a nice camp fire on Pluto from Earth).
Just to make the importance of the wavelength understandable, a 1.5m BlueRay has a RL of a few thousand km.
If I lost a few here already, I am sorry [&o], but that is the basics of laser weaponry, that Ned actually talked about.
The other important factor of how a coherent EM-beam damages the target is absorption versus reflection, and of course opacity.
That is actually basic optics. A light beam of a specific wavelength is absorbed by one material, is reflected by another and runs through glass with the third.
The absorption and reflection are what gives us color in our meager lives. A panchromatic light beam (all colors) hits a object. The material of the object absorbs anything but 550 nm wavelength (that it reflects totally).
Now 550 nm are a solid yellow. The yellow light being reflected from the object hits our eye, and oh wonder, we learn the object is yellow.
That may be interesting, but in combination with weapon-grade coherent EM-beams it becomes important.
If we now have a weapon laser with 550 nm, and hit said object, then 99% of the energy you hit the object with are reflected elsewhere. The object itself becomes a little bit warm, but that is all.
A laser with lets say 400 nm on the other hand will burn through this object like through butter.
And that does not only concern visible light, but all electromagnetic waves, including GR and XR.
Now we all know that flesh is rather see through for X-Ray. That of course means that a much smaller percentage of its energy works in the flesh. Instead it goes mostly right through.
The smaller the wavelength of the EM-beam is, the lower is the energy transfer to some materials.
For GR even bones may as well not be there.
It takes denser materials to absorb these energies.
Now electromagnetic fields of sufficient strength are known to refract light beams, changing its direction. But the efficiency of the shield... ha... field depends on its own strength (in Tesla), and, who would have thought it, the wave length.
Beams of different wavelength are refracted differently, so to be most effective the field has to be designed to work against a specific wave length.
All that makes designing coherent EM-weapons so interesting.
Use GR with an enormous range, an enormous accuracy, and if the enemy has not used dense materials for his ship you could as well throw wet tissue balls, or use for example blue ray, have an way shorter range, and everything painted in this special shade of blue is invulnerable for us, but the rest gets to feel our wrath?
Decision, decisions...
Completely different for particle beam weapons.
Contrary to photons, particles have actually mass. They don't race around the neighborhood with 300,000 km/second (oh, what has the youth come down today. Speeding through the town...), and most important, contrary to the name they make no beam.
Particle weapons are to be understood at sub-atomic shot guns. With many, many many balls in the load.
They are devastating at short range, cooking armor, the air behind it, the clothes of the crew, the skin protected by those clothes and so on.
But as with every shot gun, after a distance it is all but useless.
With better choke-like technologies you can increase the effective range. But in the end it remains small compared to even a blue ray laser, not to speak about a GRASER.
Also particles are as a rule electromagnetically charged (in most cases the way they are usable as munition at all) and electro magnetic fields work exceptionally good against them.
But armor is more or less toast.
So, just to make it clear for now, the idea that armor is especially weak against lasers while em-fields are especially good is actually completely wrong.
2. What Ned calls heat weapons. I think he means the energy torpedo's like in DW. The BIG problem with energy torpedo's is the target seeking. When you have launched it, how does it change its direction?
There are a few different ideas in this place, but mostly it is that simple.
Could be a devastating slug thrower variant (encapsulate the plasma in a magnetic field and then accelerate it through a gun at relativistic speeds. Combines the kinetic effect of the slug thrower (plasma can actually be more dense than solid matter) with the slight burning you feel when you are used as practice target for the plasma burner... (actually one of the "superweapons" I mentioned in the other thread is based on that. Just imagine a 150m diameter ball of 15 million Kelvin hot plasma with a density 5 times that of steel, accelerated to 90% the speed of light. And now instead of "normal" matter use anti matter. This baby is called Ragnarök. I once took the fun and calculated the energy this thing brings into one shot. Since then I had a slight case of subtracting data processing and lost all my accumulated data of this and a few other fun toys, but IIRC it was somewhere in the range of a few dozen Exatons of TNT. With the Czar bomb Ned mentioned being the strongest explosion we ever managed with 54 Megatons, meaning the Ragnarök is 9 orders of magnitude stronger than the Czar)).
3. Slug throwers... a fun story for the whole family.
Actually Slug throwers are most probably the oldest weapon family in existence.
Why? Well, technically the proto-human that took a stone and threw it against a intended meal was the first slug thrower in human history.
Every ranged weapon we know today are either self propelled (missiles) or slugs thrown by a slug thrower.
The spear? A primitive slug.
The Arrow? A bit less primitive slug with enhanced thrower capabilities.
The Bolt? The best man portable slug primed by muscle energy and launched by elastic materials.
The gunball? The first chemically thrown slug.
The .50 BMG a self contained slug with its own chemical launch-system, needs the slug thrower "only" for aiming, directing and of course igniting it.
For scifi we need of course a few different things.
Sure, the chemical powered slug thrower is still there (the autocannon is nothing else) but for serious ship to ship combat a little bit under powered.
There are 2 primary powering modes for slug throwers.
Electromagnetic or gravitational.
With out the ability to generate gravitational fields, we are at the moment reduced to the electromagnetic method, well, mostly. One gravitational way exists. Go into orbit and let go...
So lets concentrate on electro magnetic slug throwers...
There are two major approaches to this.
The Rail-Gun and the Gauss-Gun (aka Coilgun).
The railgun is actually the more primitive variant.
2 electrical wires transporting a strong current are spanned. These wires generate a magnetic field. A strong magnetic field. Now a slug of metal will be put between the wires, touching booth of them, shortening them out. This in turn generates a magnetic field opposite poled to the one generated by the wires.
We all know what happens when we put 2 strong magnets near to each other in opposite poled direction. They are repulsed.
Same here. The wires and the slug repulse each other. Only one of them can move. The slug. As long as it touches booth wires it will be further accelerated.
As the wires work as rails, that what they are called. And that is why the gun is called rail gun.
The principle was invented 1918 by a French. The first real working on the idea was 1944 by the Luftwaffe. They actually designed an anti air gun on this principle, and where far in the design process, when they lost the war.
After the war this idea and the designs where reviewed. While the idea generally was feasible, the gun design to launch 2 slugs of 0.5kg high explosive at 2000 m/s (compared to the 880 m/s contemporary flaks had) would need enough electrical energy per shot to illuminate half of Chicago.
Even with an sufficient amount of energy available, the principle has a distinct disadvantage. The rails are called rails because the slug runs over them.
That does wear down the rails rather hard, and more important for space battles, limits the maximum muzzle speed to something that will not smelt the rails.
The coil gun on the other hand is a such simple approach that it is nearly self explaining.
You have a multitude of coils on the barrel. You load the slug in at one end, and activate the 1st coil. This generates a magnetic field drawing the slug to it.
Just before the slug reaches the coil, you shut it down, and activate the 2nd coil. The slug is drawn to coil 2.
That you do until your slug has the desired speed.
As you are already using strong magnetic fields you can as well levitate the slug magnetically in the center of the barrel, preventing it from touching actually anything.
This design has 2 very bad disadvantages.
A. The empowering and shutting down of coils takes time. A minimal amount per coil, but at some speeds the activating and deactivating of the coils becomes a hard to juggle game.
B. Materials become somehow immune to magnetism (only a short time, but again, with the speeds we are talking here a short time is enough to make it rather hard to accelerate above a distinct speed). That is called saturation.
Booth these problems seemed to make a coil gun theoretical possible but impracticable. That is the reason why in all the shooters you hear about rail guns. Or why the US Navy build a rail gun experiment and not a coil gun experiment.
But in the last few years it was found out that both these problems are actually not so big anymore if you use super conducting materials.
The limiting factor for muzzle speed became air friction. It is just a big no no when your slug burns up in your barrel (and as we are talking about ceramic compounds we are talking about really big speeds here).
Naturally that is unimportant in vacuum, and even for that a technology already exists, the plasma window.
4. What Ned called shock wave cannons, well that is a direction I actually never thought about. So I can't say much about them.
I hope, I have not bored you to much, and if the ones of you who stayed awake could wake up the ones who didn't that would be very nice.
I think that is enough for the introduction of a thread, and I refrain from the higher tech based weapons for now.
We have enough time discussing them to the extreme in the future.
|
|
|
|
