Short Article: Laser Weapons Won’t be Good for Space War
September 3, 2010 1 Comment
There is a good technical mistake, often committed whenever we are going to pioneer space war. In various games like Star Cruisers, it is vigourasly shown that to knock your opponent down what you have to do is, just beam your laser weapon to metallic spaceship and all the stuff is over. Is is drastically and technically correct? With all this frightfulness flying at your ship, you’d want some kind of defense, besides just hoping they’ll miss. As mentioned before, advances in effectiveness of weapon lethality and defensive protection are mainly focused on the targeting problem. That is, the weapons are generally already powerful enough for a one-hit kill. So the room for improvement lies in increasing the probability that the weapon actually hits the target. And the the probability that the weapon actually hits the target. And the room for improvement on the defensive side is to decrease the probability of a hit. Weapons can be improved two ways: increase the precision of each shot(precision of fire), or keep the same precision but increase the number of shots fired(volume of fire). Precision of fire is governed by
[a]the location of the target when the weapons fire arrives,
[b]the flight path of the weapons fire given characteristic of the shot and the environment though which the shot passes, and
[c]the weapon’s aiming precision. Volume of fire is governed by
[d]the weapon’s rate of fire and
[e]the lethality of a given shot.
A defense can interfere with the[a] location of the targetby evasive maneuvers. There isn’t really a way to interfere with [b] the characteristics of a shot, short of inserting a saboteur into the crew of the firing ship. A defense can interfere with the environment through which the shot passes by such things as jamming the weapon’s homing frequencies or clouds of anti-laser sand(which may work in the Traveller universe, but not in reality). There isn’t really a way to directly interfere with [c] the weapon’s aiming precision(again short of a saboteur), though one can indirectly do so by decreasing the target’s by decreasing the target’s signature, increasing the range or jamming the firing ship’s targeting sensors and degrade their targeting solution. Finally, while one cannot do much about the [d] weapon’s rate of fire, the [e] lethality of a given shotcan be effectively reduced by rendering harmless shots that actually hit. This is done by armor, point defense, and science-fictional force fields.
But our weapons are really good? Generally, laser weapons or beam weapons like high energy electron beam weapons are suggested as best proponents for space war. Kinetic weapons are not good for space war. Why? Consider a spaceship with a rest mass of say 20 tons and moving at a speed of twenty miles/second. Now a missile having mass two or three tons is fired say at a thirty miles/seconds. Now apply the law of conservation of momentum and tell me by which amount your spaceship is get deflected(ignore the special relativity since velocity is not considerable against c)? It is obvious that ship would get unbalanced and it won’t be able to fire the weapons continuously.
Like a beam of high velocity electrons, a laser beam is also capable of producing very high power density. Perhaps which is why science fiction finds it excellent especially in space war. I also find it excellent against kinetic weapons since it is precise and accurate in targetting the opponent and one hit kill as it would travel at a speed of c which is very high compared to kinetic weapon’s speed. It also diminish the inertial effects as which were very large in the case of kinetic weapons. How effective laser weapons are, it would depend upon following factors:
1. Interaction of laser beam with spaceship’s material(here I’ll assume it as to be metal in order to get better stealth)
2. Heat conduction and temperature rise
3. Melting, vaporization, and ablation.
Destroying power of laser weapons depend on the thermo-optic interaction between spaceship’s outer metal(or say material) and the beam. So, it’s obvious that the crew surface should reflect back too much to get better stealth or use ceramic material with very high temperature resistance. So what if opponent ship has a relatively thick layer of ceramics( as most of space shuttles do have)? The absorbed light propagates into the medium and its energy is gradually transferred to the lattice atoms in the form of heat. It follows the Lambert’s law here which is (Intensity at a depth)/(initial intensity)= exp(absorption cofficient*depth)
it is pretty clear from the above law that most of the laser’s power would be consumed just to vaporize a very thin outer layer(0.01micrometer) which won’t be effective much against the crew. Not only that laser’s efficiency is very low and providing a nearly hundred percent reflective armor would be excellent against laser weapons. I’ll make it more clear in upcoming articles.