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On Space TravelEdit
Isaac Newton turned the world of physics upside down when he observed his first law of motion:
A body in motion will tend to stay in motion at a constant velocity unless acted upon by an outside force.
This was earth-shattering stuff when he introduced the notion. Several hundred years ago.
The average writer for science fiction TV shows, however, is a little behind the times, because he doesn't quite get it.
Basically, goes the misconception, if your engine breaks down in space, you are boned. The ship will very quickly slow to a complete stop. Your helm officer will say "We're adrift." This means something between, "We're moving at a random (low) speed and direction," and "We're not moving at all, practically speaking."
Writers do this because if the engine in your car breaks down, you come to a stop, and if the engine in your boat breaks down, you drift at a random low speed at the whims of the currents. Based on these experiences, it feels intuitive to write that spaceships will act this way.
However, the reason these things happen is friction. On a straight road, with good tires, you can coast quite a long way on even a slight downgrade. In space, where there is no friction with the road or the air to contend with, you can coast forever, or until you hit something, which, given how big space is, is astronomically unlikely. Which means that if your engine stops working in space at top speed, it's not going to give you any trouble getting to your destination. In fact, space vehicles spend most of their time outside the atmosphere with their engines off in this fashion. Stopping when you get there, of course, is another matter.
Note that there is some friction in interstellar space, due to hydrogen particles. However, these are dispersed enough that they'd really only matter over huge distances - huge even by astronomical scales.
For that matter, the entire notion of "We only have enough fuel to get so far," is a little suspect: if you've got enough fuel to reach top speed, you've got enough fuel to go anywhere; once you reach top speed, you can just shut the engine off and coast. Of course, it would become a problem if you don't have enough fuel to stop at the end - or if, for whatever reason, you have to turn somewhere, or if your engine fuel doubles as power generator fuel, which would cause a black-out in your ship (which, if it comes up in a Space Friction plot, generally means the crew has a few hours to restore power before running out of air). None of this should be a problem if you know your situation before you set out and can plan accordingly (being boned in the event that you lose your fuel supply en route is possible, but then the problem is that you're either going to miss your destination... or you're going to hit it).
Heck, when it comes right down to it, there's also not really any such thing as "top speed", other than the speed of light; earth-bound vehicles have a top speed only because there's a speed at which the engine can no longer out-perform friction, and there's a point at which the environment will break the vehicle. Space ships won't shake apart from going too fast (though they might be obliterated by interstellar dust or irradiated by blue-shifted cosmic background radiation).
In science fiction movies and TV, asteroids are never anywhere near as thinly spread as they are in reality.
Unmanned space probes routinely go through the real asteroid belt. If the scientists can squeeze some extra money out of the budget, they'll nudge the probe a bit so they can take some pictures of an asteroid—because a random trajectory that isn't specifically planned to see an asteroid won't. (This actually happened with the Cassini mission, which didn't have the budget to nudge the probe. During its trip through the whole belt, it saw one asteroid as a point of light at a distance of 1.6 million kilometers.) The asteroid belt could actually be reasonably accurately described as an "asteroid vacuum".
Sci-fi asteroids, on the other hand, form a vast, hyperkinetic obstacle course. Small nimble spacecraft can slalom through, if skilfully piloted, but capital ships must plough straight through the dense-packed rocks, if they can't shoot them out of the way.
In real life, large solid asteroids don't even rotate more than once every few hours; otherwise centripetal force pulls them apart. In sci-fi, enormous rocks spin like tops and whiz around all over the place, and frequently even run into each other.
This process ought to leave the sci-fi asteroid field as uniform gravel after a few years, but has apparently been going on for millions of years without a pause.
On Surviving in SpaceEdit
Outer space is not friendly. Woe betide anyone foolish enough to step into it unprotected (or unfortunate enough to get thrown out the airlock): they'll pop like a turkey with a grenade up its backside.
Well, that's the movie version. In fact, as unfriendly as the vacuum of space is, the body's made of stern enough stuff to stay in one piece. When you step outside, you've got about 15 seconds before you pass out from anoxia (which is, of course, less time than most people can go between breaths if pressed; vacuum is a very efficient de-oxygenator of blood), a couple of minutes at best until you die from the same, and all sorts of nasty decompression injuries and having exposed areas swelling up and ohmygosh the water just boiled off my eyes in between, but you never quite go boom: remember, technically speaking, your blood is not in a vacuum: it's in you, so swelling and boiling blood only occurs toward your squishiest, outermost layer. Incidentally, holding your breath would be worse than useless; the difference in pressure would cause you to exhale anyways, except probably mess up your throat in the process. Worse, for breathing the chest and lungs work on the principle that the pressure inside the lungs and outside the chest is roughly the same. Lacking the outside pressure while air is contained in the lungs they can overinflate and rupture, killing you even after you may be rescued.
A classic piece of Hollywood Science; in fact this is so widespread that audiences are outraged when it doesn't happen (see The Coconut Effect and Reality Is Unrealistic). Discussed in detail here.
This one can happen in real life if you get a really high pressure gradient - from above-normal pressure down to atmospheric pressure, say. If you're interested, google for the "Byford Dolphin".
The term "Explosive Decompression" is legitimate, but it refers to the speed at which the decompression occurs, not the result or cause.
Freezing In SpaceEdit
Space is cold, right? We hear Speculative Fiction writers blather about "the cold depths of space" or "the freezing void." If you get thrown into space, you're going to freeze straight away, assuming you don't explode.
An unfortunate inversion of Convection Schmonvection is the widely held assumption that space is objectively "cold." Although what little matter there is between the stars is extremely cold, it can only make other matter cold by coming in contact with it. There's so little matter floating around out there that the odds of hitting enough of it to actually absorb the heat from you are very, very, very low.
The physics behind this are quite simple. Heat transmission can occur in three basic ways: convection, conduction and radiation. In the near-perfect vacuum of space, convection and conduction are, if not completely out of the question, not going to happen nearly often enough to make a noticeable difference. This makes heat exchange vastly more difficult. The biggest difficulty in designing modern spacecraft is in cooling them, not heating them; observe vacuum flasks, which use vacua specifically for insulation.
Changes in the temperature of an object in a vacuum depend on whether it radiates more energy than it absorbs from cosmic radiation. This means that a human body in interstellar space will eventually freeze, but it will take a very long time. Note that near a star (or other energy-emitting Negative Space Wedgie), an object in space is likely to gain far more heat than it loses.
However, the idea that anything exposed to space will instantly freeze has some basis in reality, though for different reasons. The vacuum of space will cause any water to immediately boil, robbing the object of heat quickly — energy has to be absorbed to change from a liquid to a gas. This evaporative cooling will likely cause some freezing on a person Thrown Out The Airlock — the eyes and mouth, for instance — but will just make their death slightly more horrible (and blurry), rather than instantly turning them into a Human Popsicle.
As well, slightly more technically-inclined people may get confused by the so-called cosmic microwave background radiation, energy which permeates the known universe at a temperature of about 3 kelvins. A common simplification of this concept is to say that the temperature of space is 3 kelvins — which many take to mean that you'll freeze down to 3 kelvins if you go out there.
"Cold Space" is a near-universal trope in Speculative Fiction, to the point that, when aversions appear, they meet with disbelief.
First off, there are two broad classes of sensors: passive and active. Passive sensors just detect any emissions from the target, i.e., they passively look for the target. Passive sensors include telescopes and heat sensors. Active sensors emit various frequencies and detect their reflection off the target, i.e., they actively "shine a light" on the target. Active sensors include radar and lidar/ladar.
Active sensors are much better at detection, but have the annoying side effect of virtually placing a huge flashing neon sign on your ship that says: "LOOK AT ME! I'M HERE! SHOOT ME, SHOOT ME!!" . This not only lets all hostiles (detected and undetected) know where you are, but also gives their deadly radar-homing missiles some radar to home in on.
Passive sensors, on the other hand, are more blind but are undetectable. Much better if you are trying to hide. Passive sensors also generally can detect objects at a much greater range than active sensors.
Why? An active sensor emits "pings" of electromagnetic radiation in order to illuminate the target, the sensor "sees" the target if the energy returned by reflecting off the target is high enough to be detected. If the target has a small dimension compared to the angular and range resolution of the active sensor, the strength of the return signal is proportional to the inverse fourth-power of the distance to the target (i.e., signal fall-off is 1/r4). Why this fall off is 1/r4 instead of the 1/r2 you'd expect from the inverse square law is explained here and here. Basically only a fraction of the initial pulse energy is reflected back. So the target acts as if it was an active sensor emitting pings with a strength of 1/r2 of the original pulse. These pseudo-pings travel back to the original ship, suffering a further loss of 1/r2. This combines to make an effective loss of 1/r4.
Wargames like GDW's STAR CRUISER describe interplanetary combat as being like hide and go seek with bazookas. Stealthy ships are tiny needles hidden in the huge haystack of deep space. The first ship that detects its opponent wins by vaporizing said opponent with a nuclear warhead. Turning on active sensors is tantamount to suicide. It is like one of the bazooka-packing seekers clicking on a flashlight: all your enemies instantly see and shoot you before you get a good look. You'd best have all your sensors and weapons far from your ship on expendable remote drones.
Well, that turns out not to be the case.
The "bazooka" part is accurate, but not the "hiding" part. If the spacecraft are torchships, their thrust power is several terawatts. This means the exhaust is so intense that it could be detected from Alpha Centauri. By a passive sensor.
The Space Shuttle's much weaker main engines could be detected past the orbit of Pluto. The Space Shuttle's manoeuvering thrusters could be seen as far as the asteroid belt. And even a puny ship using ion drive to thrust at a measly 1/1000 of a g could be spotted at one astronomical unit.
This is with current off-the-shelf technology. Presumably future technology would be better.
~+~My Comments on this and explanations as to why Stealthcraft exist~+~ Stealthcraft, when running "Invisible", store all their heat in specialized torpedoes, which, when fired, will used that heat to melt through the hull of an enemy ship and then blow up inside. :)
Rockets Don't Got Windows
Spacecraft have no need of windows or portholes, for much the same reason as a submarine. (No, the Seaview doesn't count. Strictly science fiction. There are no panoramic picture windows on a Trident submarine). Windows represent structural weakness, and there really isn't much to see in any event. Unless the spacecraft is orbiting a planet or docking with another ship, the only thing visible is the depths of space and the eye-searing sun. And unlike submarines, windows on a spacecraft also let in deadly radiation.
Star Trek, Star Wars, and Battlestar Galactica to the contrary, space battles will NOT be fought at a range of a few feet. Directed energy weapons will force ranges such that the enemy ships will only be visible through a telescope. Watching a space battle through a port hole, you will either see nothing because the enemy ships are too far away, or you will see nothing because a reflected laser beam or nuclear explosion has permanently robbed you of your eyesight.
The navigation room might have an astrodome for emergency navigation. But for the most part windows will be omitted in favor of radar, telescopic TV cameras, and similar sensors.
On Space CombatEdit
Apparently when humans eventually move out into space their knowledge of guided weaponry will not go with them. Space fighters of the future will bristle with all manner of laser and particle cannon but, with few exceptions, none will have hardpoints for mounting guided missiles.
This does not make a whole lot of sense. Given the speeds possible and realities of Newtonian motion once constraints like gravity and atmosphere are removed, getting close enough to an enemy fighter to hold it in your gunsights is going to be very difficult at best. Especially if that fighter can simply pivot and bring you under its guns. Destroying it at long range with a guided weapon becomes much more desirable and much more effective.
But darn, dogfighting looks so cool!
Of course, even missiles (and fighters) don't really make much sense in an extraterrestrial setting filled with directed energy devices and weaponized mass projectors. Given the fact that your weapons move at or near the speed of light and have practically infinite range, the simplest way to wage war would be to stand off as a dot at a distance of lightseconds and hammer your targets with weapons they couldn't even detect coming until it was already too late (although at that distance, dodging becomes much easier due to lightspeed delay, and it's not possible under Real Life physics to hide your warship's approach). Since this would be far too much like real modern naval warfare (i.e.: not as exciting, although "Backfire" raids would be interesting), it's almost never depicted. Instead, most space combat, whether at the capital ship or fighter scale, is generally fought at near-spitting distance.
It's present in way too much science fiction to list (movies, TV shows, games), but Star Wars is the obvious first one. Of course, the decision there was to consciously imitate WW1 and WW2 dogfights, using air combat war footage and movies like Battle of Britain as inspiration. Since then most movie makers have been copying Star Wars.
Rockets Are Not Fighter Planes
I don't care how the X-wing and Viper space fighters maneuvered. It is impossible to make swooping maneuvers without an atmosphere and wings.
You also cannot turn on a dime. The faster the ship is moving, the wider your turns will be. Your spacecraft will NOT move like an airplane, it will act more like a heavily loaded 18-wheeler truck moving at high speed on a huge sheet of black ice.
There is also some question of whether space fighters make any sense from a military, scientific, and economic standpoint.
Rockets Are Not Arrows
Spacecraft do not necessarily travel in the direction their nose is pointing. During an engine burn the thrust will be in the direction of the nose. But once the thrust is off, the ship can turn to any orientation. It can fly "sideways" through space if it wants. This can be important during space combat, in order to get your ship's weapons to bear on the enemy.
So all those scenes from Star Wars and the old Battlestar Galactica where a hapless space fighter cannot shake the enemy on their tail are utter bilge. All they have to do is spin on their short axis and blast the tail-gater. (For a good example watch the Babylon 5 episode "Midnight on the Firing Line")
Weapons used on an atmosphere-bearing planet (like the one you live on) will suffer air resistance, gravity and other restricting factors. In space, there's no such thing. However, the word "maximum range" will frequently pop up in space battles, which makes no sense. All weapons in space have virtually unlimited range. This can be especially jarring if laser beams are immediately cut off when they reach maximum range, which happens frequently in video games.
A related concept is that a laser weapon/particle beam weapon doesn't lose power over great distances, which happens because of diffraction or "blooming". Laser beams will, however, gradually lose their coherence in a vacuum, widening their focal point as range increases. They impart the same total energy, but may not cause enough localized heating to do damage at ranges of many light-seconds.
Of course, weapons having a maximum effective range makes sense, since at very far distance, lasers are less powerful, projectiles takes time to cover longer distances and so are easily dodged.
As far as most TV writers are concerned, space is flat, like a great big tabletop. A few who have actually seen an airplane fly allow that space may have a third dimension as large as five or ten miles high, but not much more than that. There's just enough up-and-down to allow for dogfights between fightercraft and clever one-time-only attacks from above during battles between space warships. Otherwise, vessels approach each other as if they were floating on the sea and attempt broadside or bow-to-bow shots almost exclusively.
Maneuvering is also shackled to the X-axis most of the time. Very rarely will sci-fi shows and writers take advantage of the lack of "up/down" in real space by having ships attack each other at odd angles or vectors, which would offer something visually and tactically fresh. Even outside of battle, when two ships approach each other, no matter where they come from, they will always be oriented the same way; you never see a ship flying "upside down". (On rare occasions, an exception will be made for derelicts. Then again, upside-down derelicts can be found in the ocean, too.)
Perhaps as a corollary to the above, two (or more) starships, when involved in a standoff situation, will inevitably position themselves literally nose to nose in classic stare-down posture. This can be justified depending on the ships' weapons placements, but as often as not it's just a metaphor for the situation. The flip side of this is that, when two friendly ships are together, they will always be traveling side by side — that is, shoulder to shoulder. Not unlike escorts, even when they're not escorting. Abandoned ships may list visibly to one side as if sinking.
Needless to say, nobody will ever think of bypassing a planar asteroid belt or similarly hazardous feature by simply going above or below it. It's also possible to wall off part of the universe by placing a barrier that spans the full ten-mile height from top to bottom.
By extension, and by analogy to earth-bound geography, every major location in space is at a fixed position. A planet may turn on its axis (if you're lucky), but its place relative to its sun and other planetary neighbors never changes. Think of a model solar system made of balls on a table. All distances and travel times are static; all positions are permanent and unchanging. Orbits simply don't happen — if two planets are X units apart on the left side of their sun, they'll always be X units apart and on the left side of the sun.
Now, all of this is bogus, of course, but the kind of hack writer who used to churn out television scripts for SF shows usually had no more clue about physics and astronomy than the family dog does, and sometimes less. As far as they were concerned, space was just like the surface of the earth, only bigger. In recent years, more scientifically-aware writers — and actual hard-science writers as well — have taken up the mantle, and space on TV is starting to look more like the real thing. But even they won't often let facts get in the way of the plot.
It isn't necessarily a mistake on the writer's parts, either; two-dimensional strategies are simply easier to show and explain, and much easier for most viewers to grasp (since that's how we're used to thinking.)
George William Herbert says a nuke going off on Terra has most of the x-ray emission is absorbed by the atmosphere, and is transformed into the first fireball and the blast wave. There ain't no atmosphere in space so the nuclear explosion is light on blast and heavy on x-rays. In fact, almost 90% of the bomb energy will appear as x-rays behaving as if they are from a point source (specifically 80% soft X-rays and 10% gamma), and subject to the good old inverse square law (i.e., the intensity will fall off very quickly with range). The remaining 10% will be neutrons.
When it comes to the dreaded EMP created by nuclear detonations, matters become somewhat complicated.
Most SF fans have a somewhat superficial understanding of EMP: an evil foreign nation launches an ICBM at the United States, the nuke detonates in the upper atmosphere over the Midwest, an EMP is generated, the EMP causes all stateside computers to explode, all the TVs melt, all the automobile electrical systems short out, all the cell phones catch fire, basically anything that uses electricty is destroyed.
This is true as far as it goes, but when you start talking about deep space warfare, certain things change. Thanks to Andrew Presby for setting me straight on this matter.
First off, the EMP I just described is High Altitude EMP (HEMP). This EMP can only be generated if there is a Terra strength magnetic field and a tenuous atmosphere present. A nuke going off in deep space will not generate HEMP. Please be aware, however, if a nuke over Iowa generates a HEMP event, the EMP will travel through the airless vacuum of space just fine and fry any spacecraft that are too close.
First, consider a uniform slab of material subject to uniform irradiation sufficient to cause an impulsive shock. A thin layer will be vaporized and a planar shock will propagate into the material. Assuming that the shock is not too intense (i.e., not enough heat is dumped into the slab to vaporize or melt it) there will be no material damage because of the planar symmetry. However, as the shock reaches the back side of the slab, it will be reflected. This will set up stresses on the rear surface, which tends to cause pieces of the rear surface to break off and fly away at velocities close to the shock wave velocity (somewhat reduced, of course, due to the binding energy of all those chemical bonds you need to break in order to spall off that piece). This spallation can cause significant problems to objects that don't have anything separating them from the hull. Modern combat vehicles take pains to protect against spallation for just this reason (using an inner layer of kevlar or some such).
Now, if the material or irradiance is non-uniform, there will be stresses set up inside the hull material. If these exceed the strength of the material, the hull will deform or crack. This can cause crumpling, rupturing, denting (really big dents), or shattering depending on the material and the shock intensity.
For a sufficiently intense shock, shock heating will melt or vaporize the hull material, with obvious catastrophic results. At higher intensities, the speed of radiation diffusion of the nuke x-rays can exceed the shock speed, and the x-rays will vaporize the hull before the shock can even start. Roughly speaking, any parts of the hull within the diameter of an atmospheric fireball will be subject to this effect.
In any event, visually you would see a bright flash from the surface material that is heated to incandescence. The flash would be sudden, only if the shock is so intense as to cause significant heating would you see any extra light for more than one frame of the animation (if the hull material is heated, you can show it glowing cherry red or yellow hot or what have you). The nuke itself would create a similar instant flash. There would probably be something of an afterglow from the vaporized remains of the nuke and delivery system, but it will be expanding in a spherical cloud so quickly I doubt you would be able to see it. Shocks in rigid materials tend to travel at something like 10 km/s, shock induced damage would likewise be immediate. Slower effects could occur as the air pressure inside blasts apart the weakened hull or blows out the shattered chunks, or as transient waves propagate through the ship's structure, or when structural elements are loaded so as to shatter normally rather than through the shock. Escaping air could cause faintly visible jets as moisture condenses/freezes out - these would form streamers shooting away from the spacecraft at close to the speed of sound in air - NO billowing clouds.
First off, the weapon itself. A nuclear explosion in space, will look pretty much like a Very Very Bright flashbulb going off. The effects are instantaneous or nearly so. There is no fireball. The gaseous remains of the weapon may be incandescent, but they are also expanding at about a thousand kilometers per second, so one frame after detonation they will have dissipated to the point of invisibility. Just a flash.
The effects on the ship itself, those are a bit more visible. If you're getting impulsive shock damage, you will by definition see hot gas boiling off from the surface. Again, the effect is instantaneous, but this time the vapor will expand at maybe one kilometer per second, so depending on the scale you might be able to see some of this action. But don't blink; it will be quick.
Next is spallation - shocks will bounce back and forth through the skin of the target, probably tearing chunks off both sides. Some of these may come off at mere hundreds of meters per second. And they will be hot, red- or maybe even white-hot depending on the material.
To envision the appearance of this part, a thought experiment. Or, heck, go ahead and actually perform it. Start with a big piece of sheet metal, covered in a fine layer of flour and glitter. Shine a spotlight on it, in an otherwise-dark room. Then whack the thing with a sledgehammer, hard enough for the recoil to knock the flour and glitter into the air.
The haze of brightly-lit flour is your vaporized hull material, and the bits of glitter are the spallation. Scale up the velocities as needed, and ignore the bit where air resistance and gravity brings everything to a halt.
Next, the exposed hull is going to be quite hot, probably close to the melting point. So, dull red even for aluminum, brilliant white for steel or titanium or most ceramics or composites. The seriously hot layer will only be a millimeter or so thick, so it can cool fairly quickly - a second or two for a thick metallic hull that can cool by internal conduction, possibly as long as a minute for something thin and/or insulating that has to cool by radiation.
After this, if the shock is strong enough, the hull is going to be materially deformed. For this, take the sledgehammer from your last thought experiment and give a whack to some tin cans. Depending on how hard you hit them, and whether they are full or empty, you can get effects ranging from mild denting at weak points, crushing and tearing, all the way to complete obliteration with bits of tin-can remnant and tin-can contents splattered across the landscape.
Again, this will be much faster in reality than in the thought experiment. And note that a spacecraft will have many weak points to be dented, fragile bits to be torn off, and they all get hit at once. If the hull is of isogrid construction, which is pretty common, you might see an intact triangular lattice with shallow dents in between. Bits of antenna and whatnot, tumbling away.
Finally, secondary effects. Part of your ship is likely to be pressurized, either habitat space or propellant tank. Coolant and drinking water and whatnot, as well. With serious damage, that stuff is going to vent to space. You can probably see this happening (air and water and some propellants will freeze into snow as they escape, BTW). You'll also see the reaction force try to tumble the spacecraft, and if the spacecraft's attitude control systems are working you'll see them try to fight back.
You might see fires, if reactive materials are escaping. But not convection flames, of course. Diffuse jets of flame, or possibly surface reactions. Maybe secondary explosions if concentrations of reactive gasses are building up in enclosed (more or less) spaces.
Say that the habitat module of your combat starship gets penetrated by an enemy laser beam. What happens? Luke Campbell and Anthony Jackson have the straight dope:
That depends on the parameters of the beam.
A single pulse with a total energy of 100 MJ would have the effect of the detonation of 25 kg of TNT. Everyone in the compartment who is not shredded by the shrapnel will have their lungs pulverized by the blast.
That same 100 MJ delivered as 1,000,000 pulses of 100 J each could very well drill a hole. The crew see a dazzling flash and flying sparks. Some may be blinded by the beam-flash. Anyone in the path of the beam has a hole through them (and the shock from the drilling of that personal hole could scatter the rest of them around the crew compartment). Everyone else would still be alive and would now be worrying about patching the hole.
Although it occurs to me that the jet of supersonic plasma escaping from the hole being drilled could have the combined effect of a blowtorch and grenade on anyone standing too close to the point of incidence, even if they are not directly in the beam. The effect would probably be similar to the arc flash you can get in high power, high voltage electrical systems, where jets of superheated plasma can cause severe burns from contact with the plasma, blast damage from the shock waves, blindness from the intense light produced, and flash burns from the radiated heat.
A continuous beam could have enough scattered and radiant heat to cause flash burns to those near the point of incidence, along with blinding those who are looking at the point of incidence when the beam burns through. If it burns a wide hole, people die quickly when the compartment explosively decompresses, throwing everyone into deep space. If it burns a narrow hole, the survivors who can see can just slap a patch over the hole to prevent the escape of their air.
Kinetic Kill WeaponsEdit
(Wysp: This is what was mentioned eariler when Efren saw the battleship that he soon after sunk, for reference.)
Kinetic Kill weapons are unguided missiles that have no warheads. Bullets and artillery shells in other words. They can be a simple as a bucket of rocks dumped in the ship's wake. Since they are basically solid lumps of matter they are much cheaper than a missile. They cannot be jammed, but by the same token they do not home in on the target. The damage they do depends upon the relative velocity between the kinetic lump and the target ship.
A rail gun is two highly charged rails. When a conducting projectile is introduced into the breech, it strikes an arc between the rails, and is accelerated down the barrel by Lorentz force. The projectile can be composed of anything, as long as the base will conduct electricity. Sometimes a non-conducting projectile is accelerated using a conducting base plate called a sabot or armature. The maximum velocity of the projectile is about six kilometers per second, which is pretty freaking fast. This would give the projectile about 3.8 Ricks worth of damage, e.g., a ten kilogram projectile would have as much striking power as thirty-eight kilograms of TNT.
Coil guns or mass drivers are a series of donut shaped electromagnetic coils (Philip Eklund calls it a "centipede gun", in the Traveler role playing game they are called "gauss guns") A projectile composed of some ferromagnetic material is introduced into the first coil. The coil is energized so it repels the projectile and the next coil is energized so it attracts the projectile. When the projectile reaches the second coil, the second switches to repulsion and the third starts attracting, and so on. Advantages are a much lower power consumption than an equivalent rail gun. Disadvantages are the massive power switches required. Each individual coil needs bracing, as they are under tremendous force trying to expand the coil.
Missiles, and why they are usually the Weapon of ChoiceEdit
Missiles are small drone spacecraft that chase enemy ships and attack them with their warheads. It can have its own propulsion unit, or be launched by a coilgun and just use small guidance jets. It can carry a single warhead, or be a "bus" carrying multiple warheads. Or multiple mini-missiles. Go to The Tough Guide to the Known Galaxy and read the entry "MISSILE"
One of the big advantages of missiles over directed energy weapons is that missiles do not generate huge amounts of waste heat on the firing ship. A missile can be pushed off with springs or cold gas. Once clear of the ship, the missile's propulsion system ignites. But then all the waste heat is the missile's problem, not the ships.
By the same token, the disadvantage is that missiles are expendables, unlike laser bolts (as Anthony Jackson puts it: "If you're willing to have expendables, you can also have expendable coolant."). When the missile magazine runs dry, the launcher will just make clicking noises. But a laser cannon can fire as long as it has electricity.
The second advantage of missiles over directed energy weapons is that (depending upon the warhead) most missiles are not subject to the inverse square law. Laser bolts grow weaker with distance but a nuclear warhead has the same strength no matter how far the missile travels. However, laser bolts cannot be neutralized by point defense.
Armor is a shell of strong material encasing and protecting your tinfoil spacecraft. Unfortunately as a general rule, armor is quite massive, so it really cuts into your payload allowance.
Basically, the energy requirement to damage a surface is measured in joules/cm2. If you exceed that value, you do damage, otherwise you fail. Keep in mind that a Joule is the same thing as a watt-second.
There are three ways that weapon energy damages a surface: thermal kill, impulse kill, and drilling.
Thermal kill destroys a surface by superheating it. Impulse kill destroys a surface by thermal shock. In the calculations for the SDI, the amount to thermal kill a flimsy Soviet missile is about 1 to 10 kilojoules/cm2 (100 MJ/m2) deposited over a period of a second. The same energy deposited over a millionth of a second is required for an impulse kill. Since the laser beam tends to be meters wide, the beam energy is in the hundreds of megaJoules.
However, neither thermal kill nor impulse kill works very well with armor. So we use the third method: drilling. The amount of energy required to drill through an object is within a factor of 2 or so of the heat of vaporization of that object. There are also two other limits: the maximum aspect ratio of the hole is usually less than 50:1, and the actual drilling speed, for efficient drilling, is limited to about 1 meter per second (depending on the material).
Therefore, the best anti-laser armor will be that material with the highest vaporization energy for its mass. The best candidate is some form of carbon, at 29.6 kilojoules/gram. You do not want a form that is soft or easily powdered, or the vapor action under laser impact will blow out flakes of armor, allowing the laser to penetrate much faster. Steel has a higher vaporization energy, but it masses more as well.
In the real world, defensive force fields do not exist. But if they did it would make things so much easier.
There are a couple of remotely possible real-world "force fields". Dr. Geoffrey Landis speaks of magnetic fields to ward off positively charged particle radiation. More on the fringe are cold plasmas, which could ward off microwaves and particle radiation. But they have a long way to go before they can stop weapon-grade particle beam weapons.
But there isn't anything like E.E."Doc" Smith's electromagnetic radiation stopping "ray-screens", nor his matter stopping "repellor screens."
There is a very good in-depth analysis of the science and issues of force fields at the alway authoritative Stardestroyer.net website here and here.
As always when dealing with rubber science, the smart move is to nail down the ground rules for the item in question, think out all the logical consequences and implications, and stick to them.
If the force field blocks incoming laser fire, will it block your outgoing fire as well? In Isaac Asimov's "Black Friar of the Flame", a ship has to drop its field entirely in order to fire its weapons. This lead to chain reactions, ship A drops and fires, then it is hit by ship B who drops and fires, who is hit by ship C who drops and fires... In Larry Niven and Jerry Pournelle's The Mote in God's Eye, the Langston Field can have temporary holes opened to allow egress of your laser fire. In other novels, the field is on stroboscopically, that is, it flickers. It will be on, say, 80% of the time, and off for 20%. If your lasers flicker in synch with your field, 100% of their energy will penetrate. But since your opponent's lasers will probably not be in synch, only 20% of their energy will penetrate. However, if your opponent manages to match your synch rate, you'll be clobbered.
Point Defenses and why it is ImportantEdit
Point Defense is a fancy name for all the short ranged weapons and anti-missile missiles used to shoot at incoming enemy missiles. They are analogous to anti-aircraft guns.
A low powered weapon would do for defense against nuclear warheads. John Schilling says that nuclear weapons are rather complex and fragile devices, and it doesn't take much to put them out of action. And they do not undergo sympathetic detonation, i.e., they don't go boom just because you hit them real hard. So if your point-defense system can score a solid hit, the nuke is effectively useless.
Noise in SpaceEdit
Whenever a satellite or space vessel of any kind is shown, there will be either a beeping in time with one of the lights (for satellites) or the sound of the engines, which is usually a low rumble. Whenever weapons are fired, there will always be an accompanying sound, especially with "laser" weapons (which do not produce any kind of sound anyway, parodied in the Internet line "PEW PEW PEW!"). Whenever there is an explosion, it will be clearly audible.
This is mostly due to The Coconut Effect, but can sometimes be taken to extremes.
Very rarely will characters who find themselves outside of the ship require the use of the one way to talk to somebody in space without radio - going up to them and touching your helmet to theirs, allowing the vibrations to transmit directly from your suit to theirs. Even when distance, stellar activity, jamming, etc. are present, which would normally render most, if not all, radio communication impossible.
It is standard cinematic convention that sound is always subjective - you hear what the characters are hearing. If a scene cuts from an establishing shot to a close up while someone is speaking, the sound never changes in volume, even though the new camera might be a tenth as far away from the speaker as the old one. Since the ship can hear itself, and there is nothing else in the scene, it is natural to include audio from the ship's point of view. Deleting audio would only be correct if a character was somewhere able to see, but not hear, the ship.
Another more 'technical' explanation has more to do with the rules of television production: a silent space battle is supposedly incredibly boring, and unlikely to attract viewers that have just tuned in. Of course, those who have tried generally found the above untrue, but trying requires a certain amount of creativity many creators lack. A music track often serves just as well.
Space is also an excellent medium for carrying whalesong.
In Real Life, the inside of a spaceship is often noisier than the same machinery would be on the ground, because sound tends to echo a lot with nowhere to go.
A tangentally related phenomenon is filmmakers' frequent disregard of the speed of sound in action films. Regardless of how far away the camera and characters may be from an explosion, artillery piece, etc, the sound of the blast is usually heard at exactly the same time as it is seen. Compare this to, say, fireworks, or lightning.
Some viewers can ignore this patent unrealism by calling it just another Translation Convention for the benefit of the audience. Others just can't get over it at all.
War and its effect on the MindEdit
If there is one thing that I have always had an issue with in the fantasy/science fiction genre, it is the way that many writers seem to gloss over the devastating psychological affects of killing. Characters in fantasy stories often seem to make the transition from the simple, every-day farmboy who couldn’t harm a fly to the Supreme General of the Resistance who has killed hundreds of thousands of men without any readily apparent affects on their psyche. While the fantasy genre is not at all the most realistic of genres, this is a gross problem and one that must be rectified immediately.
So let me say it bluntly: killing is a lot harder than most people think. Now, don’t get me wrong, I don’t talk from experience, but this is a well-documented fact. Take a look at statistics throughout the years. In World War II, only fifteen to twenty percent of American soldiers ever fired a shot at an enemy in front of them. Boiling it down, that means that one in five Americans actually shot at a Nazi when they saw one. Or consider the fact that in the Civil War the numbers were often times much smaller, between ten to fifteen percent of Civil War soldiers shot at a Yankee or a Confederate when they saw one.
It seems strange, doesn’t it? I mean, Americans in World War II had been conditioned since boot camp to believe that the Nazi soldiers were the epitome of evil that stood against truth, justice, and the American way. Why didn’t they fire? The reason is simple: in the animal kingdom, most animals will not kill another member of their species except in VERY rare circumstances, and humans are no exception.
“But wait!” I hear you say. “What about the fighter bomber who can indiscriminately bomb thousands of civilians without any great affects upon his emotional and psychological state?”
Here we come to the crux of the psychology of killing, the truth that so few fantasy writers seem to grasp: distance matters. A fighter bomber is able to kill thousands of people without any lasting affects because he cannot see their despair, cannot hear their screams, cannot smell their blood as it is shed. To the pilot of a fighter bomber the people that are being bombed are, for the most part, abstracts, concepts.
However, if we take a look at what a soldier on a field goes through, the situation changes dramatically. Now, not only is the enemy soldier visible, but you can see that he is just like you. You can see that he is sweating and shaking with fear, just like you. You can look into his eyes and see his agony and terror. You realize that he has a family, has hopes, has dreams, has a life just like you do. Now you tell me how hard it is to pull the trigger that will send him to eternity and take away all of that.
It must be said that there are ways around that. In World War II the problems that many soldiers faced was the fact that they had trained to kill paper targets, but met a flesh-and-blood human being on the field. This was rectified in the Vietnam War and all wars thereafter, the training targets were and are now more realistic, so that the act of killing on the battlefield becomes an instinct. Oftentimes a soldier in a modern-day war will pull the trigger before he can rationalize what he is doing. Of course, this can sometimes have a greater psychological affect on him: he did it despite his desire not to, despite the fact that all of his morals screamed to him, “No don’t do it!”
There are other methods to overcoming the desire not to kill, as well. Cultural indoctrination works wonders: Nazi soldiers were bred believing that Jews and blacks were subhuman animals that had to be exterminated, and because of this had an easier time on the battlefield. Idealogical morals also can overcome the fight or flight instinct, this is why Catholic soldiers in the Crusades and Muslim extremists today can kill the infidels who stand against their God.
So we can all clearly see that killing is a much more complex and devastating thing than most writers (especially those in Hollywood) make it out to be. The reality of this is a sharp contrast to the characters of writers such as Christopher Paolini and (setting all bias aside) even Tolkien. Perhaps this is because both authors wished to minimalize the faults in their characters; fear and self-doubt being things that would detract from the image of a nearly all-powerful mega-warrior. However, our generation is moving away from the trend of perfect characters. Gone are the Luke Skywalkers and the Frodo Bagginses, and quickly moving in are nittier, dirtier, darker characters who demand that they be taken seriously.
While I understand that fantasy as a whole is a genre in which writers can explore the depths of their creativity and create things that could not be in the real world, human nature cannot be ignored. War – whether it be on a battlefield in the Middle East or in the pages of a novel – is not about armies, guns, or battles; it is about people, and writing of any genre should reflect this.