Weapons are instruments used to cause harm to a target. This article deals specifically with space and anti-space weaponry, in space warfare.
Weapons using kinetic energy (the energy of motion) to deal damage. The greater the velocity of the object relative to the target, the more kinetic energy it will possess. Such weapons can be as simple as rocks dropped into the path of the enemy ship or as complex as a coilgun. As solid pieces of matter, they do not home and must be directed at the target accounting for motion and potential evasive action.
In space, the effectiveness of kinetic weaponry is increased due to the vacuum environment. Without air resistance or gravity, they will continue along the path which they were propelled along until they meet another object, giving them infinite potential range. However, targetting limitations, evasion, and other factors cause them to have an effective range far lower than this. Kinetic weaponry is far superior to laser and particle beam weaponry with the same energy input in terms of lethality.
Kinetic energy can easily be calculated by the following equation (as long as the velocity does not exceed approximately 10% of the speed of light):
- KE = 0.5 x m x v2 (KE=0.5*m*v^2)
- KE = kinetic energy.
- m = mass in kilograms
- v = velocity in metres per second.
Make sure not to confuse kinetic energy with force. A force is an influence that causes an object to alter motion, direction, or shape, whereas kinetic energy is a form of energy possessed due to motion.
It is evident that an increase in velocity does more to increase kinetic energy than in increase in mass, as the velocity term is squared. Naturally, if the ship is already travelling towards the target, its effective velocity will be added to the projectile's own and it will do more damage. Inversely, if the target is receding, the damage will be lessened.
Some good general rules of thumb are that an object at 3km/s delivers kinetic energy equal to its mass in TNT and that an object at 200km/s delivers kinetic energy per kilogram approximately equal to a low-yield nuke. However, projectiles at these velocities will tend to overpenetrate and not deliver all their damage to the target, so it is wise to design them so that they will deform on impact and deliver more energy.
The main methods of propelling a kinetic weapon are through a gun, a railgun, a coilgun, or using a built-in rocket.
Conventional guns use an explosive charge to launch the projectile down a barrel towards the enemy. Modern rifles, cannon, and howitzers have a firing pin which strikes a primer charge on the cartridge, causing it to ignite. This releases a jet of burning gas which ignites the propellant charge, which then detonates. Most modern guns do not need an oxygen atmosphere due to the presence of oxygen in the charge.
Railguns use a pair of parallel charged rails through which accelerate a conductive projectile. Factors affecting the acceleration include magnetic field strength, rail seperation, railgun length, and projectile mass. Top current railguns can launch a 2kg projectile close to 4km/s with 6m long rails, but this requires a current through the rails of an enormous 6.5 million amps. Railguns are also notoriously inefficient and produce large quantities of waste heat. Projecting the projectile also causes major wear to the rails, which gets worse as velocity increases, and may result in them needing to be replaced each shot. Due to the high levels of recoil, the railgun will need major bracing to avoid being ripped out of its sockets when the gun fires. Sufficiently powerful railguns actually make a good means of propulsion, if very inefficient. A railgun placed off axis is also likely to cause the ship to begin spinning uncontrollably when it fires.
Coilguns use a series of electromagnetic coils to accelerate a ferromagnetic (think iron, steel, nickel) projectile down the barrel. They can reach higher maximum velocities than railguns (limited by magnetic saturation of the projectile), but require even more bracing as each magnet is trying to explode under the forces involved. Factors determining the rate of acceleration are similar to those for railguns. A coilgun is capable of firing faster than a railgun as more than one projectile can be accelerated at once. Modern coilguns are significantly behind railguns, though 120mm coilgun mortars have been designed by the US military.
Rocket-propelled projectiles have an inbuilt rocket that causes them to accelerate towards the enemy, like an explosive-less, non-homing missile. The gyrojet is an example. Advantages include not having to worry much about recoil, but disadvantages include ineffectiveness at close range (they're still accelerating) and cost.
Kinetic weapons are expendables and require the vessel to carry ammunition. In space, every gramme counts, so this may be a problem. They can also be dodged. However, it is extremely difficult for point-defence systems to neutralise them.
Kinetic weapons make bad anti-orbital weapons as planetary escape velocities are very high (Earth's is about eleven kilometres per second), but are effective against aerial targets as anti-aircraft weapons. As point-defence, ultra-rapid-fire CIWS weapons such as the US Navy's Phalanx are effective at intercepting missiles. However, there is a chance that even if the missile is hit and damaged, it may not be destroyed, diverted or scattered sufficiently to prevent damage. Modern anti-ship missiles also make erratic manoeuvres just prior to impact, and as the kinetic projectiles are unguided, they cannot compensate once fired.
In bombardment, the planet's own gravity will assist in bringing the projectile to Earth, increasing the kinetic energy of the weapon. If an object is dropped (not launched) from 100km up, air resistance will do little to its velocity and it will hit the ground at just over 1km/s. From further away, the projectile can reach 11km/s due to gravity (all asteroids have at least this velocity).
A missile is an unmanned vehicle that pursues targets and attacks them with its warheads. Missiles can contain a single warhead, several, or even more missiles. They usually carry their own propulsion unit, and can either be launched hot (with assistance from the spaceship) or cold (all acceleration has to be done themselves). Missiles do not cause waste heat or recoil problems on the ship and can continue to accelerate or manoeuvre so long as they have fuel.
A proposed idea is to call such weapons with acceleration capabilities similar to spaceships 'torpedoes' and those with greater acceleration capabilities 'missiles'.
Missiles will always hit unless neutralised by point defence or they run out of fuel. They can have proximity- or time-fuzes. Payloads can be nuclear, antimatter, high explosive, shrapnel, and many more.
Again, missiles are expendables, and there are mass and space limitations on how many can be carried.
They can be useful anti-orbital weapons. ICBMs travel in low-Earth orbit. Anti-satellite missiles as tested by the USA and China can take out small objects as high up as over 250km. However, enemy warships can stay (and are likely to stay) further away than this. Missiles are not so useful in bombardment due to them often being highly fragile.
Missile point-defence may be viable. The RIM-116 is an infrared homing missile system designed to destroy cruise missiles. These systems have greater range than gun-based point defence and can make course corrections in flight.
Lasers fire a beam of coherent electromagnetic radiation at a target. Lasers have different effects depending on their parameters. They can damage by thermal kill, impulse kill, or drilling.
In thermal kill, the surface upon which the laser is incident is superheated by the energy transferred. The region affected will be vaporised and expand at a very high velocity, doing physical damage to the region. Thermal kill on an unarmoured missile with a megawatt-class laser may take a second or so.
Impulse kill destroys the target by thermal shock. The structure of the affected region will fail and it is likely to explode, shattering and launching high velocity shrapnel in all directions. This would occur if megajoules of energy were deposited on a missile over the course of a few microseconds.
Drilling is possible where a series of short pulses are fired at the target. Each excavates a short way into the target, producing opaque vapour which expands away over the course of a few microseconds. Another pulse then hits the target, and so a hole is drilled. This is the best approach for dealing with good armour.
Laser effectiveness declines with distance, as the beam diffracts. The smaller the wavelength of the radiation, the greater its effective range, and the greater the size of the focussing lens, the smaller the spot size. The starting intensity of the laser is determined by its power supply. Also, due to light-speed lag, assuming the target is performing random evasive manoeuvres the maximum range of a laser is a few hundred thousand kilometres. If the target's vector is predictable, or if they are static, effective ranges are in the millions of kilometres. Future targetting systems will be more than capable of aiming at even small enemy signatures in space at this range.
Lasers are supposedly infinite-fire weapons- as long as electricity is supplied, they can continue to function. However, they are extremely inefficient, and most lasers have a useful output of less than half of the power supplied. As such, powerful lasers are likely to require heat sinks of ice, water, or other substances with high specific heat capacities. These heat sinks will get hot and the laser will become unable to fire without causing major damage to itself and the ship when they do so. Giant radiators are not tactically viable as the enemy will shoot them off.
Shuttering lasers while not in use is a good idea. If an enemy laser is incident on the lens, it will be focussed inside your ship and deal great damage to your laser's workings.
The US air force has constructed the Airborne Laser. This is a prototype chemical laser turret fixed to an aircraft. It fires a near-infared beam with a power supply of 30MW and the airforce has given figures of a three to five second beam being able to destroy an unarmoured, liquid-fuel missile from 370km. This is too long to have to keep the laser focussed on the target and the laser is currently not tactically viable.
Lasers are probably the best anti-orbital weapons. As their beams travel at the speed of light, reaching escape velocity and evasion are not problems, and they have effective ranges to around the distance from the Earth to the Moon. As they are based on the ground, they can use rock or ice as a heat sink, enabling them to be more powerful and fire more often than ship-based lasers. The atmosphere is opaque to x-rays and smaller, and also blocks several frequencies of infrared and UV (but not others).
Laser point-defence is likely to be useful against missiles, given sufficient dwell time (the time for which the laser is focussed on the missile). However, many or armoured missiles are likely to overwhelm such a system.
Particle beams accelerate electrons or ions using charged grids towards a target, such as the cathode-ray tubes in old televisions, or particle accelerators like the LHC at CERN. Particles are capable of penetration, depositing energy several centimetres into the target as well as the surface, whereas lasers cannot penetrate.
Producing weapons-grade particle beams requires massive equipment, often enormous magnetic coils. High currents and energies are required. The particles will be travelling very close to the speed of light.
Charged particle beams repel themselves (as all particles have a like charge). In space, this means they are very short-range, blooming into uselessness rapidly. However, within an atmosphere, they self-focus for this same reason and have long ranges.
Neutral particle beams (usually created by firing electrons into a charged particle beam) do not self-repel and so have similar ranges to a low-grade laser. However, they are almost useless within an atmosphere.
Particle beams are not likely to be used to cause structural damage. Instead, they are likely to be used to kill the crew and electronics on board a ship. If electron, proton, or neutral atom particle beams strike the armour, they will cause massive release of x-rays (this is how a dentist's x-ray works) and kill the things inside. They may also transmute part of the ship's hull into radioactive isotopes.
The more energetic the particles are, the more they will penetrate. The more massive the particles, the harder they will be to deflect, but the harder it will be to accelerate them.
Particle beams do not make good anti-orbital or bombardment weapons as they will have to travel through both a vacuum and an atmosphere.
You can read about what is publicly known about nuclear weapon construction and design here.
Nukes release both x-rays and neutrons when they explode. In an atmosphere, these x-rays hit the atmosphere and cause the production of the fireball and EMP, but these will not occur in space. Typical nukes release about 90% of their energy as x-rays. Alternatively, neutron bombs can be used which are about 80% neutrons and 20% x-rays.
Yields for nuclear weapons are usually measured in tons of TNT. The hiroshima bomb had a yield of about 15 kilotons (15,000 tons) of TNT. W87 thermonuclear warheads have a yield of about 475 kilotons (Trinity, 20kt). The B53 nuclear bomb had a yield of about 9 megatons (9,000,000 tonnes), and the largest ever tested nuclear device had a yield of over 50 megatons (Ivy Mike, 11 Mt, Castle Bravo, 15 Mt). As even a few tons of TNT can cause enormous damage, it is evident that these weapons are extremely powerful. A nuke detonating a few metres from a spaceship will almost certainly vaporise it, and even from several kilometres away a radiation kill is likely.
Nukes are effective at pretty much everything. They can be carried by missiles (singly or with many warheads) and make very effective ship-to-ship, bombardment, or anti-orbital weapons. They are also very delicate- hitting a nuclear bomb is almost certainly going to disable it completely.
As per e=mc^2, a gram of antimatter reacting with a gram of matter will yield around 43 kilotons worth of energy. However, not all of this is usable.
If an electron and a positron react, they release two gamma rays. If a proton and an antiproton react, a whole mess of particles are created, many of which are useless here (such as neutrinos). Within a few metres of the reaction, the pions which are the main product are capable of causing radiation poisoning or creating a fireball (if in atmosphere) but decay much further out. The explosion produced by the already reacted antimatter will also throw unreacted particles away from each other, wasting them as they shoot off into space. The gamma rays, then, are the main useful product. The efficiency of antimatter might conservatively be about 70%, though optimistically it could be 85% and pessimistically it could be 10%. This is still much more energy per kilo than a nuclear weapon.
Containing antimatter is very tricky. Given future technology, a civilisation might be able to contain a gram of antimatter in a 100kg containment device. This will be extremely fragile and require high power input, so antimatter is probably not a good missile filling. However, as a placed bomb, it could still be effective.
Comparison of weapons systemsEdit
|Name||Advantages||Disadvantages||Approx. effective range in space||Anti-Orbital capability?||Bombardment capability?|
|Conventional Kinetic||Indefinite range. High rate of fire.||Can be evaded, recoil.||10,000km||No||Yes|
|Railgun||Indefinite range. High velocity.||Waste heat, recoil, can be evaded.||50,000km||No||Yes|
|Coilgun||Indefinite range. Very high velocity.||Loads of waste heat and recoil. Can be evaded.||100,000km||Yes||Yes|
|Missile (conventional)||Indefinite range, always hits.||Can run out of fuel.||-||Yes||No|
|Missile (nuclear)||Large area of effect, indefinite range, always hits.||Fuel, fragile.||-||Yes||Yes|
|Missile (antimatter)||As above.||Fuel, very fragile, high mass.||-||No||Yes|
|Maser (microwave laser)||Good range, light speed.||Large spot size, waste heat.||300,000km||No||No|
|Laser||Great range, light speed.||Waste heat.||300,000km||Yes||Maybe|
|Charged p. beam||Good range in atmosphere. Little structural damage.||Massive accelerator. Blooms in space.||10km||No||No|
|Neutral p. beam||Good in space. Little structural damage.||Massive accelerator. Useless in atmosphere.||100,000km||Maybe||No|