Faster Than Light
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The Trouble With StarDrives
I wasn't going to put this section in, but I have to. I wanted to keep the website as free from handwavium as possible. However, while Faster-Than-Light travel is about as handwavium as you can get, it is unfortunately the sine qua non of interstellar space opera. Space opera with no StarDrive is like chocolate cake without the chocolate. FTL is sometimes called "superluminal". In vintage SF, the propulsion was commonly termed "hyperdrive", since the starships evaded Einstein by entering a dimension called "hyperspace" where there was a higher speed limit. Star Trek has its "warp drive" that reduces the distance to be traveled by warping space. The RPG Traveller has its "jump" drive that teleports the ship from point A to point B. In his "Lucky Starr" novels, Isaac Asimov uses the term "Hyperatomic spaceships", presumably since the spacecraft had both a faster-than-light Hyperspace engine and a more conventional atomic engine. Go read the "Faster Than Light" entry in Wikipedia.
Fred Kiesche says that a faster than light starship should have a license plate that reads "ME = MC2"
FTL. Faster than light. This is by far the most important item of HANDWAVIUM technology in Space SF, and is absolutely necessary for the communications, TRADE, and WARFARE of the KNOWN GALAXY. No one, after all, wants to take decades or centuries to get anywhere. For this reason, even HARD SF usually makes an exception for FTL. You just can't leave home without it.
TECHJARGON terms include Hyperspace, Subspace, and a host of meaningless names - such as my own Ashikaga Jump, named for its purported inventor. Warp was old-fashioned even when classic Trek used it, and is hardly encountered any more. (Interestingly, though, it is one piece of Techjargon that has entered the everyday language; people who never heard of FTL know that warp speed means "really, really fast.")
FTL is primarily a form of rapid transit for space vehicles, needed to literally move the plot along. FTL radio is also common (the most frequent Techjargon term is Ansible), but is sometimes left out as not entirely necessary - you can always send a ship with a message, and the resulting haphazard communications are a rich source of plot complications. Perversely, Ursula Le Guin has things the other way around - Ansibles, but no FTL drive. I'm going to be sexist and say that this is a woman thing: you can yak on the phone, but creeps can't get to you to break in and rape you.
FTL requires Handwavium because of that damned speed-of-light barrier to travel in normal space. Over the years, SF writers have grasped at any conceivable loophole in the laws of physics that might theoretically allow them to speed things up. The physicists have actually been - very marginally - helpful in this regard, what with wormholes, quantum tunneling, and so forth. Basically, though, FTL remains sheer Handwavium, in that its properties are wholly arbitrary. (Unlike, say, a matter-antimatter DRIVE, for which you can at least calculate energy-to-thrust ratios and the like.)
Broadly speaking, FTL environments fall into two classes, those that you "fly" through and those that you "jump" through. The first type allows you to actually navigate - change course, or even fight battles - while in FTL. It also favors artsy semi-streamlined spacecraft designs, a la Trek, presumably to slide cleanly through whatever it is you go through in FTL.
In contrast, "jump" FTL is a sort of rabbit hole that you hop through to get where you're going. Navigation is all done beforehand, in normal Space, as you line up to make the jump. Once you make it you have no further control till you pop back out, hopefully where you wanted to go. Jump FTL often limits movement to specific JUMP POINTS.
Both types of FTL often require some kind of intuitive skill for successful navigation. This is a convenient way to make automated drone STARSHIPS impossible, forcing them all to have crews.
Trek, of course, had a fly-through FTL, but on the whole the fashion in Space SF has been leaning toward jump FTL. This is for a couple of reason. The semi-demi-plausible wormhole and quantum-tunneling concepts seem to imply a jump. More important, though, jump FTL is less intrusive in stories.
This is desireable, because most Space SF writers - myself included - are basically guilt-ridden about FTL. We would like to make our stories seem plausible, and may go to a great deal of effort to research, say, what stars are likely to have HABITABLE PLANETS, how much thrust a fusion Drive can generate, or the economics of interstellar Trade. But right at the heart of the whole damn thing is what amounts to magic. So far as genuine scientific plausibility goes, a ship's FTL Drive might just as well be a pretty woman in a white dress who lights some candles and flips tarot cards while chanting in Welsh.
So the only decent thing to do with FTL is make it as inconspicuous as possible, act as if stars are really just a little farther apart than planets, and hope against hope that the physicists eventually turn up something solid. Till then? Keep chanting in Welsh, babe.
The important point is to keep the fracture under control. Hack writers will assume that "if we have to break a few laws of physics for FTL, why not just throw all the laws out the window?" Don't give in. Omitting physics will degrade your novel to a pathetic lack of accuracy worse than an average Space Ghost cartoon.
What to do? Keep all the physics you can. And when you break the laws for your FTL drive, at least establish some limitations and rules. Then stick to them! Internal self-consistency is better than nothing.
The general rule is what physicists call the correspondence principle or the Classical limit. This states that any new theory must give the same answers as the old theory where the old theory has been confirmed by experiment. Newton's laws and Einstein's Relativity give the same answers in ordinary conditions, they only give different answers in extreme conditions such as near the speed of light, refining the accuracy of the GPS system, or calculating the orbit of Mercury (none of which Newton could confirm by experiment).
The point is: you, as a science fiction author inventing a FTL drive, have to explain why current scientific theory didn't discover FTL travel decades ago. Harry Turtledove turned the problem on its head and turned the explaination into the plot of the short story.
As a general rule, a given science fiction novel has one faster than light method. Two notable exceptions are The Halcyon Drift by Brian Stableford and Startide Rising by David Brin. Both of those novels have half a dozen stardrives used by various races and factions, each with different capabilities and limitations.
There are two main dodges. You may remember from Physics 101 that travel time = distance / rate of travel. For example, if you have to travel 100 miles, and you maintain a speed of 50 miles per hour in your automobile, the travel time will be two hours. The laws of physics forbids any rate of travel faster than the speed of light. Since the distances between stars are so astronomically huge, this means the travel time will be measured in decades or centuries. This is unacceptable in a fast-paced science fiction novel.
Dodge #1 is to handwave some technobabble way of increasing the starship's rate of travel to faster than light. From the equation you can see this will reduce the travel time. In Geoffrey Landis' Canonical List of StarDrives, this includes Continuous Drives and Modifying the Universe: Modify the speed of light.
Dodge #2 is to handwave some technobabble way of reducing the distance to the starship's destination. From the equation this also reduces the travel time. This includes stardrives that warp or fold space. Taken to extremes, the distance can be reduced to zero along with the travel time. These are "jump" or teleportation drives where the ship vanishes at point A and instantly appears at point B. In the Landis list, this includes Discontinuous Drives and Modifying the Universe: Modify distance in space. Sometimes a jump drive is a machine inside a starship, sometimes it is an external installation called a "jumpgate" or "stargate".
Why do these dodges violate the laws of physics? Well, that is complicated, but there are two main problems: the Light-speed barrier and Causality. This is explained with some depth at Jason Hinson's authoritative "Relativity and FTL" website, so I'm just going to give a short summary. Refer to Hinson for details.
It is unclear if reducing the distance is allowed or not, and nobody is sure how to warp space on a commercial level. Suggestions generally involve gravity fields of intensities only found around black holes and/or wormholes (aka Einstein-Rosen bridge). Warping the fabric of space would seem to require astronomical amounts of energy, and heaven help any solar systems that got wadded up in the warp.
The Light-Speed Barrier
That old spoil-sport Einstein ruined FTL travel when he created his theory of General and Special Relativity.
Now according to common sense (and as codified by Isaac Newton), velocities will add to each other. If you are travelling at twenty kilometers per hour due north, and you add five kilometers per hour northward to your velocity, you should now be travelling at twenty-five kilometers per hour due north. Everybody (including Newton) knows that 20 + 5 = 25.
Unfortunately for us, Einstein is not everybody. In Special Relativity, no matter how fast you are moving, a beam of light appears to be moving at exactly the speed of light (the technical term is The Principle of Invariant Light Speed). One of the unobvious consequences is that velocities do NOT add. At least not when one gets close to the speed of light. Only a percentage of the new velocity is actually added.
What percentage? Well, the faster you go, the lower the percentage. And at the speed of light, the percentage is zero. So in theory, once you are at light speed, no matter how much velocity you try to add, the amount actually added is zero. Which means you can never exceed lightspeed.
Almost every single FTL drive you read about in science fiction is based on some clever way to avoid the light speed barrier.
The basic assumption of special relativity, which is most strongly confirmed by observation, is that lightspeed is the same for every observer. So, as you speed up, lightspeed stays as far away from you as it ever was. Your time and distance coordinates distort to allow lightspeed to be equally far away from people moving with respect to each other, but the point remains, no matter how much you accelerate, you can never even approach lightspeed, let alone exceed it.
Even if you completely ignore things like mass and energy, and consider simply velocity, adding more velocity can never get you to lightspeed, no matter how much you add.
The tricksy parts are the "coordinates distort" things. But the basic concept is relatively simple; approaching lightspeed is worse than a red queens race. It takes all the speed possible to just stay the same distance away from it.
Note that in special relativity, velocities do not add. Instead, rapidities add. The velocity is the speed of light times the hyperbolic tangent of the rapidity. At low rapidities, the rapidity times the speed of light is almost the same as the velocity. However, no matter how high your rapidity gets, the hyperbolic tangent maxes out at 1 for very large rapidities so that your velocity can never be higher than the speed of light.
So imagine someone in a starship. As he burns propellant, the (delta-V) / (c) consumed adds to his rapidity. If he has a lot of delta-V, he can get a very high rapidity, but when you look at the velocity, it is always less than the speed of light.
Interestingly, the time dilation and length contraction factor is the hyperbolic cosine of the rapidity.
However, very few SF novels deal with the second problem. The aphorism at rec.arts.sf.written goes "Causality, Relativity, FTL travel: chose any two."
Your average physicist holds Relativity quite strongly. It has been tested again and again with an accuracy of many decimal places. They hold onto Causality even tighter. Without Causality the entire structure of physics crumbles. Causes must preceed effects, or it becomes impossible to make predictions. If it is impossible to make predictions, it would be best to give up physics for a more profitable line of work.
Therefore, they chose to jettison FTL travel.
Please note that as far as Causality is concerned, FTL communication is every bit as bad as FTL travel.
Why only two? Relativity proves that FTL travel is identical to Time travel (to help your research, the technical term for time travel is "Closed timelike curve"). Time travel makes Causality impossible, since it can be used to create paradoxes. So if you have Relativity and FTL, Causality is impossible. If you do not have Relativity, FTL is not Time travel, so you can have Causality. Or more mundanely you can have Relativity and Causality, but no FTL/Time travel (the latter is the opinion of physicist Stephen Hawking, he calls it the chronology protection conjecture).
Clever readers will have already spotted a possible loop-hole. What if there was some law of physics that prevented Time travel from creating paradoxes?
The classic Time-travel paradox is the so-called "Grandfather paradox" (though it actually should be called the "Grandmother paradox"). Boris Badenov sneaks into Mr. Peabody's Wayback Machine (actually the WABAC machine, but who cares?) and travels back in time to when Boris' grandfather was a baby. Boris then gives his infant grandfather a lit stick of dynamite then cackles evilly as his grandfather is blown to bits. Bah-hah-hah!
But wait! Boris' grandfather is now smithereens, he'll never grow up, beget Boris' father, who will beget Boris. In other words, Boris will never exist.
But if Boris never exists, then he will never travel back in time to assassinate his grandfather. In which case grandpop will beget Poppa Boris, who will beget Boris. Start back at the beginning and repeat.
Does Boris' grandfather get blown up? Both Yes and No! A paradox.
Hinson shows there are four ways of enforcing a "no-paradox" rule for time travel. Parallel Universes, Consistency Protection, Restricted Space-Time Areas, and Special Frames. In some ways Special Frames is the best, though it directly contradicts part of Relativity (the first postulate of special relativity is that there are no special frames, "no privileged inertial frames of reference"). Oh well. For details, you'd best read the Hinson article.
The latter three are examples of the Novikov self-consistency principle.
In some late-breaking news, physicists Daniel Greenberger and Karl Svozil have shown that the laws of quantum mechanics enforces Consistency Protection. You can read their paper here, but it makes my brain hurt. Translated into English, they maintain that time travellers going back into the past cannot alter the past (i.e., the past is deterministic). This is because quantum objects can act sometimes as a wave. When they go back in time, the various probabilities interfere destructively, thus preventing anything from happening differently from that which has already taken place.
As a side note, those interested in the various ways time-travel seems to work in SF novel should run to the Guide To SF CHRONOPHYSICS.
Why have you not read about this in any science fiction novel?
It is absent from some because the authors do not know enough relativity theory to spot the FTL equals Time Travel implication.
It is absent from the rest because of those who do know enough relativity, practically no author (who just wants a quick way to get their hero from star to star) wants to deal with the huge squirming can of worms opened by time travel.
This is why the time travel connection is the dirty little secret of science fictional FTL travel.
Time was slippery. The way Pirius understood it, it was only the speed of light that imposed causal sequences on events.
According to the venerable arguments of relativity there wasn't even a common "now" you could establish across significant distances. All that existed were events, points in space and time. If you had to travel slower than lightspeed from one event to the next, then everything was okay, for the events would be causally connected: you would see everything growing older in an orderly manner.
But with FTL travel, beyond the bounds of lightspeed, the orderly structure of space and time became irrelevant, leaving nothing but events, disconnected incidents floating in the dark. And with an FTL ship you could hop from one event to another arbitrarily, without regard to any putative cause-and-effect sequence.
In this war it wasn't remarkable to have dinged-up ships limping home from an engagement that hadn't happened yet; at Arches Base that occurred every day. And it wasn't unusual to have news from the future. In fact, sending messages to command posts back in the past was a deliberate combat tactic. The flow of information from future to past wasn't perfect; it all depended on complicated geometries of trajectories and FTL leaps. But it was good enough to allow the Commissaries, in their Academies on distant Earth, to compile libraries of possible futures, invaluable precognitive data that shaped strategies -- even if decisions made in the present could wipe away many of those futures before they came to pass.
A war fought with FTL technology had to be like this.
Of course foreknowledge would have been a great advantage -- if not for the fact that the other side had precisely the same capability. In an endless sequence of guesses and counterguesses, as history was tweaked by one side or the other, and then tweaked again in response, the timeline was endlessly redrafted. With both sides foreseeing engagements to come for decades, even centuries ahead, and each side able to counter the other's move even before it had been formulated, it was no wonder that the war had long settled down to a lethal stalemate, stalled in a static front that enveloped the Galaxy's heart.
She paused and smiled. "I have heard," she said conversationally, "the voice of the President of our Galaxy, in 3480, announcing the federation of the Milky Way and the Magellanic Clouds. I've heard the commander of a world-line cruiser, traveling from 8873 to 8704 along the world line of the planet Hathshepa, which circles a star on the rim of NGC 4725, calling for help across eleven million light-years -- but what kind of help he was calling for, or will be calling for, is beyond my comprehension. And many other things.
Since FTL drives are ruled more or less impossible by current science, you have to invent your own. In such cases, the best way to start is to focus on effects instead of causes. Many novice SF novelists and game designers make the mistake of inventing a cause first and may not even try designing the effects.
An example of an effect is "The star drive can move the ship at ten light-years per hour". An example of a cause is "The Mason Field is generated by the amplification of the interaction of the Alpha and Omega sub-particles contained in the Xanthe crystal when bombarded by pseudo electron valients in a charged hydrogen field."
Effects help you avoid unintended consequences, and define the implications of your drive. Causes are fluffy technobabble explanations that a good SF story might avoid all together. As Gene Roddenberry noted, in a police TV show a policeman does not explain to the viewers how the primer of the bullet ignites the main charge propelling the lead slug down the barrel every time he shoots his handgun. Neither should Captain Kirk explain the operating principles of his phaser weapon, the fact that it is some species of sidearm is enough for the viewers.
Causes can also get you into trouble if your explanation implies new effects that you did not intend. They also give more weak points that a scientifically minded reader can use to poke holes in your theory.
The important things are the effects. Here are a few examples: How big a ship can be moved? How much faster than light is the ship? Does it require large intricate starships, or can you just mount it in a submarine? Does it require huge amounts of energy? Does it require the ship to be outside any planetary or solar gravity wells? Can the ship only enter FTL flight at special locations ? ("jump points") Does each FTL "jump" require days of tedious mathematical calculations? Can a ship in FTL flight be detected by another ship also in FTL flight? Can a ship in FTL flight be detected by another ship not in FTL flight? Does FTL flight make the crew vomit, hallucinate, have epileptic fits? Is the supply of FTL drive units limited due to a tight monopoly on their manufacture, or due to the fact that they can no longer be manufactured at all? Does it require rare and hard to get materials? (the Traveller RPG required Lanthanum, H. Beam Pipers' ships required Gadolinium. Both of these are rare earth elements, emphasis on the "rare")
These are just off the top of my head, you can find more by reading SF novels, or from your imagination.
The effects have implications in the SF universe you are creating:
If the only ships that can be moved are ones smaller than a Greyhound Bus, one implication is that you will not have titanic ships the size of Star Wars Imperial Star Destroyers, much less any Death Stars.
If your ship is twice as fast as the speed of light, it can go 100 light years in a mere 50 years. Therefore most of the action in your universe will take place close to Sol, if the average interstellar journey is two years. On the other hand if your ship is 36,500,000 times as fast as the speed of light, your ship can cross the Galaxy the long way in about one single day. The action in this universe will therefore be galactic in scope.
If there are only large intricate starships, they will be few in number and crewed by the cream of the crop. If any fool can build an FTL drive from plans downloaded from the internet and convert a septic tank into a starship, there will be zillions of starships crewed by a wide range of eccentric people.
If ships require huge amounts of energy for their FTL drives, you have to decide upon the source of said energy. Antimatter fuel implies antimatter factories or antimatter "mining." There is also the unintended consequences of a given starship containing enough energy to, say, vaporize Greenland. The further implication is that starship captains will be on a very short leash (John's Law). If on the other hand a starship can run on one AAA battery, you start having problems with FTL missiles the size of bullets.
Ships that can only enter/exit FTL flight at special locations make those locations into military choke points. Ships that can exit FTL flight anywhere coupled with ships that cannot be detected while FTL will open the possibility to genocidal interstellar wars that last all of five minutes.
In John Maddox Roberts novels Space Angel and Spacer: Window of the Mind, the "Whoopee Drive" makes the crew suffer projectile vomiting, violent diarrhea, and hallucinations. Before each jump they have to attach a barf bag over their mouth, strap themselves on to a toilet, and try to ignore the paisley Peter Max metal termites eating the hull. Naturally this made troop ships a nightmare. In Gordon Dickson's The Genetic General, closely spaced FTL jumps made without a recovery period in between would rapidly incapacitate the crew.
In David Lynch's movie adaptation of Frank Herbert's novel DUNE, mutated Guild Steersmen move starships between stars with their psychic abilities. Thus the spacing guild has a monopoly on starships. In John Brunnner's Interstellar Empire and Frederik Pohl's Heechee novels (Gateway et al) the starships are artifacts from some long lost alien race, humans can fly them but cannot construct them. In SPI's game Freedom in the Galaxy all stardrives are manufactured by the Empire, and contain thermonuclear self-destruct devices to discourage hackers from attempting to engage in reverse-engineering.
Designing Your Drive
If you want to do the job right, work backwards. Decide what type of universe you want for your book, figure out what implications it must have, then figure what constraints on the FTL will create the desired implications. Finally add a bit of colorful technobabble to describe the cause.
If you want to explore uncharted terrain, work forwards. Create a few unusual constraints, spend some time deducing some implications from the constraints, and see what sort of SF universe flows from the implications. You might stumble over an interesting universe for your next novel and/or game.
Larry Niven and Jerry Pournelle took the bull by the horns. Before they wrote their award-winning classic The Mote in God's Eye, they went to physicist Dan Alderson. Niven and Pournelle gave Alderson a list of things they wanted the proposed FTL to allow, and things to forbid. Dr. Alderson then custom designed a mostly plausible FTL drive to spec, but with additional limits. Niven and Pournelle kept within those limits, and the novel was improved as a consequence.
(interesting description of the physical basis of the Alderson drive omitted)
Travel by Alderson Drive consists of getting to the proper Alderson Point and turning on the Drive. Energy is used. You vanish, to reappear in an immeasurably short time at the Alderson Point in another star system some several light-years away. If you haven't done everything right, or aren't at the Alderson Point, you turn on your drive and a lot of energy vanishes. You don't move. (In fact you do move, but you instantaneously reappear in the spot where you started.)
That's all there is to the Drive, but it dictates the structure of an interstellar civilization.
To begin with, the Drive works only from point to point across interstellar distances. Once in a star system you must rely on reaction drives to get around. There's no magic way from, say, Saturn to Earth: you've got to slog across.
Thus space battles are possible, and you can't escape battle by vanishing into hyperspace, as you could in future history series such as Beam Piper's and Gordon Dickson's. To reach a given planet you must travel across its stellar system, and you must enter that system at one of the Alderson Points. There won't be more than five or six possible points of entry, and there may only be one.
Star systems and planets can be thought of as continents and islands, then, and Alderson Points as narrow sea gates such as Suez, Gibraltar, Panama, Malay Straits, etc. To carry the analogy further, there's telegraph but no radio: the fastest message between star systems is one carried by a ship, but within star systems messages go much faster than the ships.
Hmm. This sounds a bit like the early days of steam. Not sail; the ships require fuel and sophisticated repair facilities. They won't pull into some deserted star system and rebuild themselves unless they've carried the spare parts along. However, if you think of naval actions in the period between the Crimean War and World War One, you'll have a fair picture of conditions as implied by the Alderson Drive.
If the Drive allowed ships to sneak up on planets, materializing without warning out of hyperspace, then there could be no Empire even with the Field. There'd be no Empire because belonging to the empire wouldn't protect you. Instead there might be populations of planet-bound serfs ruled at random by successive hordes of of space pirates. Upward mobility would consist of getting your own ship and turning pirate.
The Alderson Drive or "jump point" drive has been used in many SF starship combat games, for the same reason Niven and Pournelle used it: unlike most other FTL, it allows the possibility of interstellar battles. Most other FTL is a "fly anywhere" kind of propulsion, which generally does not allow battles to occur except by mutual consent. Often a planet cannot even detect an enemy invasion fleet until it suddenly pops out of hyperspace. Interstellar wars only last long enough for your hyperspace bombers to fly to the enemy's planets, then a brief emergence to spit out a hellburner, a planet-wrecker nuclear bomb, a planet-sterilizing torch warhead, a planet-cracker antimatter warhead, or a planet-buster neutronium-antimatter warhead. Then they fly home, only to discover that the enemy's bombers were on a similar mission. Go to The Tough Guide to the Known Galaxy and read the entry "SLAG"
These start-anyway go-anywhere drives play merry Hell with concepts like 'distance', 'remoteness', 'proximity', 'adjacency', 'line of communication', 'border', and 'defence', while reinforcing such concepts as 'trade', 'concentration of force', and 'first strike'. Give me a setting in which the map still matters.
Please note that there is a second FTL situation that can allow interstellar combat. Ships travel faster-than-light taking some time to travel the distance (i.e, travel is NOT instantaneous). But there must also exists some kind of faster-than-light radar that can detect the invading ships far enough in advance that the defenders have time to do something about it. Something like wet navy combat in the Pacific ocean in the period after the time the navy was equipped with radar, but before the advent of orbital spy satellites that can see every ship on the ocean. This is more or less the situation in the Star Trek TV show(s).
(As a side note, SF Author Colin Kapp often had ships armed with "Diffract Meson" warheads, presumably based on an as-yet undiscovered scientific principle. I always thought that there was some room for a warhead type in between the 10% efficient thermonuclear warhead and the 100% efficient antimatter warhead. Say Diffract Meson warheads are 50% efficient.)
With jump points, you have choke points that can be defended. Battles occur because the enemy has no choice but to invade though the jump point. Though it does become difficult and fuel intensive for the defenders, since Alderson points do not orbit their primary star, while planets, orbital fortresses, anti-ship mines and blockading tasks forces have to. The defending forces must constantly be thrusting for the entire tour of duty just to maintain their position. In The Gripping Hand, sequel to The Mote in God's Eye, there is some mention of a constant stream of tanker ships travelling between the defending forces and the gas giant fuel sources. And there are only blockading spacecraft, orbital fortresses and mines are impractical.
Well, maybe not totally impractical. For mines a possibility is Dr. Robert Forward's statite concept. This uses a carefully angled solar sail to generate the constant thrust required to keep the mine stationary. I haven't done the math, but my gut feeling is that if the jump point is too far from the primary star the solar flux will be so low that even for low mass miles the sails will have to be huge. However, I am quite proud of making the jump point/statite connection, since this is actually an original idea by me (unlike almost all of the rest of this website).
While I haven't done the math on statites, David Harris did! Here is his analysis:
There is actually a very simple method to find the "thrust" on an object due to the solar flux radiating on it. The intensity of light per square meter divided by the speed of light has the same units (after some manipulation) as a pressure. So, very simply, to find this solar pressure, divide the intensity of light (in Watts per meter squared) by c (in meters per second). You get a pressure (in Newtons per meter squared). This pressure equates to light impacting on a surface, but if you have a mirror, the light also bounces off. This actually doubles the pressure on a mirror.
At 1 AU from the sun, the solar intensity is 1400W/m2. Dividing by c = 3x108 m/s and multiplying by two, we find that the pressure on a 1 square meter mirror should be 9.3x10-6 Newtons.
Now, if you want your mirror to float stationary at a certain point in space (like a non-orbiting "Jump Point"), the light pressure must counterbalance the gravitational force of the sun at that point. A quick check through a high-school physics book (bring a calculator) will show that the force on a 1 kg object at 1AU from the sun is a mere 0.00590 N. With this, it is easy to show that a 1 kg statite needs a solar sail 632m2 in area, or a square 25m on a side.
Now here cones something interesting: Solar intensity falls off as a 1/r2 law (inverse square), meaning if you increase the distance by a factor of three, the intensity falls by a factor of nine. Gravity also follows a 1/r2 law, meaning if you increase the distance by a factor of three, the gravitational force falls by a factor of nine. The math is easy, but it is excruciating to type, so I will leave it as an exercise for the reader to show that, since both forces are governed by a 1/r2 law, the size of the sail does not change as you change your distance from the sun. No matter how far you are from the sun, a 1 kg statite will always need a sail 25m on a side.
Now, what fun things can we go and do with this? Perhaps we can start with a simple minefield. We can arbitrarily assume that each mine is 1 megaton. Adding on detonators, sensors, etc., assume that the whole mine is one tonne. A one tonne mine needs a sail 794 meters on a side, or 632,000m2. Since the statite mine field will be located away from a planet, let us also arbitrarily decide that we will be defending a volume of space equal to the volume of the Earth. I really do not know how big the Jump Points or Crazy Eddie Points are, so this is pure guess work.
Assume we set our mines to detonate when a ship is 1km away. If a ship flew straight through the center of our minefield, I would hope that it would get within 1 km of at least one mine. If we assume one mine per 37,680 cubic kilometers, this gives us a 50/50 chance of a ship traveling through the center of our minefield coming within 1 km of a mine. Again, the tedium of algebra manipulation in ASCII prevents me from showing how I came to this figure. At one mine per 37,680 km3, we need 24 million (!) mines. That's 15 million square kilometers of solar sails!
With that many mirrors, you could do more damage with the reflected light than with the nuclear mines themselves! 15 million kilometers of solar sails adds up to 2.1x1016 watts of reflected light at 1 AU. That's 5 megatons of energy every second. In less than two months, the solar energy delivered by these mirrors would do more than the nuclear mines they are supporting.
ClaysGhost's points out that the magnitude of the constant thrust problem depends upon how far the jump points are from the primary star.
The acceleration due to the Sun's gravity acting on a mass at the orbital distance of Jupiter is about 0.2mm/sec2. Even for a 100 tonne vehicle you need a counter-force of only 20N to keep your station.
This will make stealth difficult for a minefield. Even such low thrust from a rocket will be readily detectable, and a statite sail will be large enough to be hard to hide.
A very common limit is that the FTL drive can only be entered if the ship is "not too deep in a gravity well", that is, farther than a certain distance from either a planet or the primary star. Again keep in mind that if ships can only enter or leave FTL at about Pluto's orbit, the ships will either require unreasonably powerful normal-space rocket drives that run afoul of Jon's Law, or the ships will take years to travel between Earth and the FTL take-off point.
StarForce Alpha Centauri
Another FTL system that was carefully crafted in order to force a specific situation was the one created by Redmond Simonsen for the wargame StarForce: Alpha Centauri (keep in mind this is a paper-and cardboard tabletop game, not a computer game). In the game, starships or "TeleShips" are jumped or "shifted" instantaneously from one location to another several light-years away by teams of women with psionic powers. Shifting cannot be done by a machine, it has to be done by a person. The supply of psionic or "telesthetic" women is limited. There is no way to genetically engineer them, they naturally occur at the rate of one First Order Telesthetic per million females. Energy is cheap, any ore or element can be synthesized, any material good can be manufactured. So the only valuable interstellar commodity are telesthetic women.
This has several implications. In interstellar warfare, there are no carpet bombings of planetary populations with mass destruction weapons. This would destroy the only valuable item the planet has: a population that can produce more telesthetic women. Obviously, there are no restrictions placed on population growth, and large families are encouraged by the planetary governments.
Since the population of telesthetics is so limited, they sort of know each other. They are also all members of the same Telesthetics Guild. Therefore, in ship-to-ship combat, weapons are not designed to kill.
Instead, the anti-ship weapon is sort of a telepathic command to the enemy teleship to make an uncontrolled interstellar shift into a random location. Such a shift can be up to five times the distance of a safe shift, so a teleship will take a while to crawl back to the battle. And in any event, a teleship that can jump between the stars is not going to have any difficulty avoiding something as sluggish as a laser beam.
Against planetary populations, teams of telesthetics can create the so-called Heissen Effect. This sedates the inhabitants, sending them to sleep. The ships then land squads of StarSoldiers in gravity sleds to take control. The inhabitants later wake up with migraine headaches.
Teleships have a maximum safe shift limit of five light years. If a friendly teleship does nothing but sit stationary and telesthetically "enhance" its location, another friendly can do a safe shift to that enhanced location from up to ten light years.
Attempting to shift a distance greater than the safe limit is called "over-shifting." There is a small chance that the shift will go as planned. There is a greater chance that the shift will malfunction. A bad shift will be either a "mirror shift" where the teleship moves in the exact opposite vector, or a "randomization" where the teleship appears in a random location within twenty light-years of Sol.
A "Star Gate" is a nine kilometer ring of chanplastic, crammed with telesthetics intimately familiar with the fabric of local space. A teleship starting at a star gate and shifting to an unenhanced location has a safe range of ten light-years, fifteen light-years to an enhanced location. Shifting from one star gate to another has a safe range of twenty light-years.
Since telesthetics are at a premium, there are no warships or orbital fortresses. Instead, merchant ships and star gates are modified for warfare.
You see the basic effect that flows from the FTL drive is that wars are relatively bloodless. The secondary effect is that pressures were created that caused wars. The latter effect is desirable, since a wargame simulation requires wars to simulate.
The Solar Government was to expend several trillion Labor Credits before it discovered that...(a) the discontinuity window could not reliably be produced on or near a planetary mass; (b) only 139 people out of 19 billion could produce the effect; (c) they were all women; (d) they were all powerfully telesthetic (i.e., clairvoyant), and mildly telekinetic; (e) a window could only be created between two positions in space that the Telesthetic was "comfortable" in and felt she "knew"; (f) a Gnostech initiated by the using Telesthetic was required; (g) bionic/electronic techniques could be used to amplify and refine the effect, but no pure-machine system could create it; (h) the range of the effect was theoretically unlimited but its accuracy was subject to degradation with the square of the distance.
Psionic linking techniques and the Telesthetics founding of the Telesthetic Guild was the response. It is probably the heavy use of empathetic bridging in these techniques that explains the remarkable fact that no member of the Guild, even while on opposing combat teams, has ever deliberately caused another member's death.) This solidarity of Telesthetics was almost totally responsible for the virtually bloodless conduct of the Intra-Specific Wars of Autonomy in the 25th Century.
In a sense the Outleap itself was responsible for the Wars of Autonomy: it dispersed and enlarged the human community into a multi-system race which was heavily dependent upon one socioeconomic factor, one resource that could not be synthesized by technology — the Telesthetics. The number of Telesthetics available to a given system was almost purely a function of how much population was contained within or controlled by that system.
The freedom from birth-controls in the colonized systems did have the desired effects of providing the population basis for "home-grown" Telesthetic crews to operate the Star Gates and the increasing number of Teleship.
It also, however, had several counter-productive side effects: (a) The vastly increased and dispersed human population became ungovernable by the institutions of the Solar Hegemony, (b) the "frontier" societies tended to produce divergent eco-political systems that either wanted independence, or worse, attempted to impose their provincial "solutions" on the rest of humanity.
All these factors conspired to produce a number of essentially pointless wars.
Web and Starship
We must not forget the masterful selection of FTL limitations which created the fascinating tactical situation in the wargame Web and Starship (keep in mind this is a paper-and cardboard tabletop game, not a computer game). The game designer (the legendary Greg Costikyan) wanted to create the world's first balanced three-player game. Up until now, all three player games in practice tend to devolve into two players ganging up on the third player (i.e., they are unbalanced). Mr. Costikyan wanted to design a game that avoided this. The mechanism depended upon the constraints of the FTL system.
The situation starts with two alien races: the Gwynhyfarr (hereafter referred to as "Birds") and the Pereen (hereafter referred to as "Moles"). Each has a totally different type of FTL transport system. And, as will become an important point later, neither can use or even comprehend the others FTL system.
The Birds have FTL starships that can travel anywhere in the universe at will. No special launch or landing sites are required. The trouble is that the starships are expensive to build (i.e., there are not many of them), and each has a limited cargo capacity.
The Moles have FTL teleportation devices. A teleporter unit must be present both at the start and at the destination. Teleportation is instantaneous. Unfortunately in order to teleport to a new planet, a teleporter unit must by shipped to the planet by a Slower-than-light robot ship. This of course takes years. The advantage of teleporter units is that they have huge cargo capacities. The Moles can move entire armies through a teleporter in a matter of hours.
When the Bird Empire and the Mole Empire expanded to the point where their borders contacted each other, war was inevitable, but futile. Both empires wanted to destroy the other and take over the enemy's habitable planets. Unfortunately, due to the limitations of their respective FTL, war was impossible.
Say the Birds want to invade a Mole planet. The Bird starships can go anywhere, so the Birds load up their limited number of starships with the few numbers of solders each ship can carry, and invade the Mole planet. Whereupon the Moles use their teleporters to instantly transport in the planetary armies of all the other Mole planets, and the combined Mole armies turn the pathetically small Bird invasion force into a smoking crater.
Say the Moles want to invade a Bird planet. The Moles load a teleport unit into a STL robot ship, aim it at the Bird planet to invade, and wait a few years for it to arrive. Years later, as it approaches the Bird planet, it is noticed by Bird space patrols, who promptly shoot it to pieces.
Until one fine day both the Birds and the Moles notice radio waves being emitted by a small planet set right in between the two empires. A planet called Earth.
Naturally both empires want to conquer Earth. It is in a very strategic position and it has an industrial base that can produce war material once the population has been enslaved. And since Earth has no empire (or even FTL capability of any kind), it should be an easy conquest.
However, Earth has a few things in its favor. For one, it knows that one empire cannot attempt to conquer it without the other empire trying to prevent it. Earth has limited diplomatic contact with both empires, so it can make deals and otherwise try to keep the two empires off balance. And in the long term, Earth has a wild card. Unlike the two empires, Earth can comprehend and eventually produce both types of FTL system. In fact, they can eventually produce the game-changing "Web Starship". This is a Bird style starship which ferries a Mole style teleport unit to strategic locations.
So as you can see, careful selection of the limits on ones FTL drive can force the desired situation to come to pass.
Terrans invented the radio in the early part of the 20th century. At first, it was a toy, suitable for very limited uses; spark-gap radio provided very little band-width over which to transmit messages. But it rapidly became one of Terra's most important tools. By the 1930's, hundreds of radio stations were broadcasting news, stories, music and innumerable other programs. It became the primary medium for military messages, for local communication with mobile cabs and cars, for long distance broadcasts, for global communication. In the 1950's, television became important, and soon whole new sections of the broadcast spectrum were used to transmit messages.
At the speed of light, Terra's earliest messages flew starward. At first they were ignored, for the universe is vast and radio noise common, and receivers are not always listening for odd phenomena. Too, advanced civilizations use radio very little—planetary communications are carried via cable, or narrow-beamed to transmission satellites, while long-distance communications can be beamed via hyperwave or through the Web.
But modulated radio noise is the first sign of an emerging technological civilization, and sooner or later a radio astronomer was bound to turn his telescope to that obscure G-class star in the Carina arm....
Two great civilizations faced each other across the arm. The Gwynhyfarr, proud descendants of an aerial race, roamed the stars in mighty quantum-leap vessels. The Pereen, the children of burrowing animals, linked their worlds together with the Web. The two found each other incomprehensible. Their mathematics were incompatible, their languages based on different principles, their psychologies entirely at variance. They could not live with each other, and yet they must. Neither was sufficiently mighty to conquer its foe.
But more than this: technologies have military implications. The Gwynhyfarr ships could travel light-years in weeks, could dart from star to star and drive deep into enemy territory. They could also carry only small numbers of troops. Transporting even an infantry division required huge ships in large numbers. In a space battle, the Gwynhyfarr had no match. But the Pereen did not travel space.
The Pereen knew how to conquer intervening distance. Two points could be "gated" together, linked so that one object could pass from one point to another without travelling through the intervening space. Once a gate was constructed on a new world, it was linked via other gates to every world in the Pereen hegemony. The Web permitted instantaneous transmission of huge quantities of materiel from one world to another. The Gwynhyfarr might land a division on a Pereen world—but the Web would immediately transmit an army to that world to defeat its enemies.
But to open a gate, the Pereen must transport the necessary machinery to a new world to make the link to the Web. And the Pereen do not understand Gwynhyfarr faster-than-light travel, and have no such system of their own. Instead, sublight Pereen probes must drone their weary way across space-time toward their targets. When a target is reached, a new world can be added to the Web.
But sublight probes are small and defenseless; they cannot be otherwise, because moving anything at sublight speeds from one star to another requires a tremendous investment in energy and time. Only small objects can affordably make the trip. If a Pereen probe enters a Gwynhyfarr world, its fusion flare will almost certainly be identified.by enemy starships, and the probe destroyed.
And so, for decades, the two races bided their time in armed hostility, watching each other across the Carina arm. Limited by their technologies and systems of war, neither could defeat the other.
Then came the radio signals from Terra...
To the Pereen, Terra meant only one thing: a possible forward base from which to launch probes at the enemy; a base, moreover, with a well-advanced technology.
To the Gwynhyfarr, too, Terra meant only one thing: an industrial world where starships could be based and constructed and from which an attack on the enemy could be more easily launched.
Terra would be a valuable ally—or, failing that, a valuable slave planet.
The war began in earnest.
Stardrives in Science Fiction
Fuller still looked puzzled. "See here; with this new space strain drive, why do we have to have the molecular drive at all?"
"To move around near a heavy mass — in the presence of a strong gravitational field," Arcot said. "A gravitational field tends to warp space in such a way that the velocity of light is lower in its presence. Our drive tries to warp or strain space in the opposite manner. The two would simply cancel each other out and we'd waste a lot of power going nowhere. As a matter of fact, the gravitational field of the sun is so intense that we'll have to go out beyond the orbit of Pluto before we can use the space strain drive effectively."
But he had not eyes for it. To the west where avenue and buildings ended was the field and on it space ships, stretching away for miles — fast little military darts, stubby Moon shuttles, winged ships that served the satellite stations, robot freighters, graceless and powerful. But directly in front of the gate hardly half a mile away was a great ship that he knew at once, the starship Asgard. He knew her history, Uncle Chet had served in her. A hundred years earlier she had been built out in space as a space-to-space rocket ship; she was then the Prince of Wales. Years passed, her tubes were ripped out and a mass-conversion torch was kindled in her; she became the Einstein. More years passed, for nearly twenty she swung empty around Luna, a lifeless, outmoded hulk. Now in place of the torch she had Horst-Conrad impellers that clutched at the fabric of space itself; thanks to them she was now able to touch Mother Terra. To commemorate her rebirth she had been dubbed Asgard, heavenly home of the gods.
Her massive, pear-shaped body was poised on its smaller end, steadied by an invisible scaffolding of thrust beams. Max knew where they must be, for there was a ring of barricades spotted around her to keep the careless from wandering into the deadly loci.
"Mmm . . . you seem to know about such things. Could you tell me just what it is we do? I heard the Astrogator talking about it at the table but I couldn't make head nor tail. We sort of duck into a space warp; isn't that right?"
"Oh no, not a space warp. That's a silly term—space doesn't 'warp' except in places where pi isn't exactly three point one four one five nine two six five three five eight nine seven nine three two three eight four six two six four three three eight three two seven, and so forth—like inside a nucleus. But we're heading out to a place where space is really flat, not just mildly curved the way it is near a star. Anomalies are always flat, otherwise they couldn't fit together—be congruent."
She looked puzzled. "Come again?"
"Look, Eldreth, how far did you go in mathematics?"
"Me? I flunked improper fractions. Miss Mimsey was very vexed with me."
"Miss Mimsey's School for Young Ladies, so you see I can listen with an open mind." She made a face. "But you told me that all you went to was a country high school and didn't get to finish at that. Huh?"
"Yes, but I learned from my uncle. He was a great mathematician. Well, he didn't have any theorems named after him—but a great one just the same, I think." He paused. "I don't know exactly how to tell you; it takes equations. Say! Could you lend me that scarf you're wearing for a minute?"
"Huh? Why, sure." She removed it from her neck.
It was a photoprint showing a stylized picture of the solar system, a souvenir of Solar Union Day. In the middle of the square of cloth was the conventional sunburst surrounded by circles representing orbits of solar planets, with a few comets thrown in. The scale was badly distorted and it was useless as a structural picture of the home system, but it sufficed. Max took it and said, "Here's Mars."
Eldreth said, "You read it. That's cheating."
"Hush a moment. Here's Jupiter. To go from Mars to Jupiter you have to go from here to here, don't you?"
"But suppose I fold it so that Mars is on top of Jupiter? What's to prevent just stepping across?"
"Nothing, I guess. Except that what works for that scarf wouldn't work very well in practice. Would it?"
"No, not that near to a star. But it works fine after you back away from a star quite a distance. You see, that's just what an anomaly is, a place where space is folded back on itself, turning a long distance into no distance at all."
"Then space is warped."
"No, no, no! Look, I just folded your scarf. I didn't stretch it out of shape! I didn't even wrinkle it. Space is the same way; it's crumpled like a piece of waste paper—but it's not warped, just crumpled. Through some extra dimensions, of course."
"I don't see any 'of course' about it."
"The math of it is simple, but it's hard to talk about because you can't see it. Space—our space—may be crumpled up small enough to stuff into a coffee cup, all hundreds of thousands of light-years of it. A four-dimensional coffee cup, of course."
She sighed. "I don't see how a four-dimensional coffee cup could even hold coffee, much less a whole galaxy."
"No trouble at all. You could stuff this sheer scarf into a thimble. Same principle. But let me finish. They used to think that nothing could go faster than light. Well, that was both right and wrong. It . . ."
"How can it be both?"
"That's one of the Horst anomalies. You can't go faster than light, not in our space. If you do, you burst out of it. But if you do it where space is folded back and congruent, you pop right back into our own space again—but a long way off. How far off depends on how it's folded. And that depends on the mass in the space, in a complicated fashion that can't be described in words but can be calculated."
"But suppose you do it just anywhere?"
"That's what happened to the first ones who tried it. They didn't come back. And that's why surveys are dangerous; survey ships go poking through anomalies that have been calculated but never tried. That's also why astrogators get paid so much. They have to head the ship for a place you can't see and they have to put the ship there just under the speed of light and they have to give it the gun at just the right world point. Drop a decimal point or use a short cut that covers up an indeterminancy and it's just too bad. Now we've been gunning at twenty-four gee ever since we left the atmosphere. We don't feel it of course because we are carried inside a discontinuity field at an artificial one gravity—that's another of the anomalies. But we're getting up close to the speed of light, up against the Einstein Wall; pretty soon we'll be squeezed through like a watermelon seed between your finger and thumb and we'll come out near Theta Centauri fifty-eight light-years away. Simple, if you look at it right."
She shivered. "If we come out, you mean."
"Well . . . I suppose so. But it's not as dangerous as helicopters. And look at it this way: if it weren't for the anomalies, there never would have been any way for us to reach the stars; the distances are too great. But looking back, it is obvious that all that emptiness couldn't be real—there had to be the anomalies. That's what my uncle used to say."
"But we will not do it all at once," Mrs. Whatsit comforted them. "We will do it in short stages." She looked at Meg. "Now we will tesser, we will wrinkle again. Do you understand?"
"No," Meg said flatly.
Mrs. Whatsit sighed. "Explanations are not easy when they are about things for which your civilization still has no words. Calvin talked about traveling at the speed of light. You understand that, little Meg?"
"Yes," Meg nodded.
"That, of course, is the impractical, long way around. We have learned to take short cuts wherever possible."
"Sort of like in math?" Meg asked.
"Like in math." Mrs. Whatsit looked over at Mrs. Who. "Take your skirt and show them."
"La experiencia es la madre de la ciencia. Spanish, my dears. Cervantes. Experience is the mother of knowledge." Mrs. Who took a portion of her white robe in her hands and held it tight.
"You see," Mrs. Whatsit said, "if a very small insect were to move from the section of skirt in Mrs. Who's right hand to that in her left, it would be quite a long walk for him if he had to walk straight across."
Swiftly Mrs. Who brought her hands, still holding the skirt, together.
"Now, you see," Mrs. Whatsit said, "he would be there, without that long trip. That is how we travel."
Charles Wallace accepted the explanation serenely. Even Calvin did not seem perturbed. "Oh, dear," Meg sighed. "I guess I am a moron. I just don't get it."
"That is because you think of space only in three dimensions," Mrs. Whatsit told her. "We travel in the fifth dimension. This is something you can understand, Meg. Don't be afraid to try. Was your mother able to explain a tesseract to you?"
"Well, she never did," Meg said. "She got so upset about it Why, Mrs. Whatsit? She said it had something to do with her and Father."
"It was a concept they were playing with," Mrs. Whatsit said, "going beyond die fourth dimension to the fifth. Did your mother explain it to you, Charles?"
"Well, yes." Charles looked a little embarrassed. "Please don't be hurt, Meg. I just kept at her while you were at school till I got it out of her."
Meg sighed. "Just explain it to me."
"Okay," Charles said. "What is the first dimension?"
"Okay. And the second dimension?"
"Well, you'd square the line. A flat square would be in the second dimension."
"And the third?"
"Well, you'd square the second dimension. Then the square wouldn't be flat any more. It would have a bottom, and sides, and a top."
"And the fourth?"
"Well, I guess if you want to put it into mathematical terms you'd square the square. But you can't take a pencil and draw it the way you can the first three. I know it's got something to do with Einstein and time. I guess maybe you could call the fourth dimension Time."
"That's right," Charles said. "Good girl. Okay, then, for the fifth dimension you'd square the fourth, wouldn't you?"
"I guess so."
"Well, the fifth dimension's a tesseract. You add that to the other four dimensions and you can travel through space without having to go the long way around. In other words, to put it into Euclid, or old-fashioned plane geometry, a straight line is not the shortest distance between two points."
For a brief, illuminating second Meg's face had the listening, probing expression that was so often seen on Charles's. "I see!" she cried. "I got it! For just a moment I got it! I can't possibly explain it now, but there for a second I saw it!"
"Ladies, gentlemen! We are ready for our first Jump. Most of you, I suppose, know, at least theoretically, what a Jump is. Many of you, however—more than half, in point of fact—have never experienced one. It is to those last I would like to speak in particular.
"The Jump is exactly what the name implies. In the fabric of space-time itself, it is impossible to travel faster than the speed of light. That is a natural law, first discovered by one of the ancients, the traditional Einstein, perhaps, except that so many things are credited to him. Even at the speed of light, of course, it would take years, in resting time, to reach the stars.
"Therefore one leaves the space-time fabric to enter the little-known realm of hyperspace, where time and distance have no meaning. It is like traveling across a narrow isthmus to pass from one ocean to another, rather than remaining at sea and circling a continent to accomplish the same distance.
"Great amounts of energy are required, of course, to enter this 'space within space' as some call it, and a great deal of ingenious calculation must be made to insure re-entry into ordinary space time at the proper point. The result of the expenditure of this energy and intelligence is that immense distances can be traversed in zero time. It is only the Jump which makes interstellar travel possible.
"The Jump we are about to make will take place in about ten minutes. You will be warned. There is never more than some momentary minor discomfort; therefore, I hope all of you will remain calm. Thank you." The ship lights went out altogether, and there were only the stars left.
It seemed a long while before a crisp announcement filled the air momentarily: "The Jump will take place in exactly one minute." And then the same voice counted the seconds backwards: "Fifty...forty...thirty...twenty... ten...five...three...two...one..."
It was as though there had been a momentary discontinuity in existence, a bump which joggled only the deep inside of a man's bones.
In that immeasurable fraction of a second, one hundred light-years had passed, and the ship, which had been on the outskirts of the solar system, was now in the depths of interstellar space.
Someone near Biron said shakily, "Look at the stars!"
In a moment the whisper had taken life through the large room and hissed itself across the tables: "The stars! See!"
In that same immeasurable fraction of a second the star view had changed radically. The center of the great Galaxy, which stretched thirty thousand light-years from tip to tip, was closer now, and the stars had thickened in number. They spread across the black velvet vacuum in a fine powder, back-dropping the occasional brightness of the nearby stars.
The warp theory of my esteemed colleagues (and I am sure they will correct me if I am wrong) is based on the principle that two separate units of anything cannot exist in the same place at the same time; nor can they coexist without each having an effect upon the other. When the units are energy fields, the effect is supposed to be spectacular. (The effect is spectacular —I will admit that. As my esteemed colleagues have already so admirably demonstrated, the effect is certainly spectacular... though I somewhat doubt that this was the specific effect they had hoped for.)
Theoretically —at least, as their theory says —when two continuous fields are overlapped, it will cause a wrinkle in the fabric of existence. Unfortunately, the continuous energy field is only a myth —a mathematical construction. It is a physical impossibility and cannot exist without collapsing in upon itself.
Of course, there are still some members of this learned academy who insist on remaining doggedly skeptical of this fact of life. It is almost pitiful to watch them continue these attempts to generate an energy field that is both continuous and stable. So far, the only thing that they have succeeded in doing is to convert several million dollars' worth of equipment, buildings, and surrounding property into so much slag. (Oh, and incidentally, in doing so, they have also proven me correct.)
DR. J. JOSEPH RUSSELL, PH.D., M.A.. etc.,
comments to the Board of Inquiry into the Denver disaster
Insufferable old windbag!
ANONYMOUS "ESTEEMED COLLEAGUE"
Dammit! It's like trying to stack soap bubbles!
DR. ARTHUR DWYER PACKARD, remark overheard by lab. assistant and quoted by Duiy Hirshberg in "Packard —Behind the Myth"
In light of events, it would be criminal to let them continue.
DR. J. JOSEPH RUSSELL, comment to newsmen after appearing before the Board of Inquiry
Actually, they were on the wrong track to begin with. The problem was not to create a continuous and stable energy field at all —but only to overload a section of space. Once they began thinking of it in those terms, the. solution was obvious —and even practical, considering the then existing technology.
The answer lay in the use of a series of interlocking noncontinuous fields. The noncontinuous field gives the illusion of continuity, but like a strobe light, the field is actually a very rapid series of ons and offs. Several noncontinuous fields working in phase can create a stable continuous field. Each of the separate noncontinuous energy fields fills in the gaps of the others.
Three noncontinuous fields can dovetail their functions to make one continuous one, and two continuous energy fields can be overlapped to generate the much sought after warp.
When six field generators are working in phase and all on the same section of space, a great pressure quickly builds up. Something has got to give. Usually space does.
HOWARD LEDERER, Encyclopedia of 1,000 Great Inventions
Dammit! Why didn't I think of that?!!
Remark attributed to DR.ARTHUR DWYER PACKARD
Because, I did.
Remark attributed to DR. J. JOSEPH RUSSELL
The warp has no relation at all to normal space. It is a bubble, or miniature universe. Within it a ship still obeys all the known laws of physics, but it is totally separated from the outer universe.
The bubble, or warp, is made up of great energies locked together in a titanic embrace. The potential power inherent in that embrace is far greater than the sum of the component energy fields —not just because the bubble is a stable construct, but because it is a dimple in space itself. The very structure of existence is pressing against it, trying to restore itself to a condition of minimum distortion. With such an infinite store of unexpressed force to draw upon, the potential power of the system is almost unlimited. (In practice the limit is the size of the ship's generators.)
If a secondary set of fields is superimposed across this point of pressured space —that is, the warp —it acts to liberate some of this great power and simultaneously provides a focus for it. As every second sees the warp restored to stability, the bubble cannot collapse; but this continued release of energy must be somehow sublimated —and it is; the effect is the introduction of a vector quantity into the system.
Because the shape of the secondary fields can be controlled, they can be used to produce a controllable velocity in any direction. The warp can be made to move at velocities many times the speed of light.
The Einsteiniun time-distortion is neatly sidestepped, as the ship is not really traveling faster than light—only the warp is. The ship just happens to be inside it. It is the warp that moves, the ship moves within the warp and is carried along by it. Consequently, a starship has two velocities, one is the realized faster-than-light velocity; the other is the inherent normal space velocity....
... For maneuvering within a planetary system, inherent velocity is an important resource; but unless it is compensated for, it can cause havoc to a ship in warp....
JARLES "FREE FALL" FERRIS, Revised Handbook of Space Travel
"We first began picking it up on the cosmic ray monitors at 16:12, shortly after the start of Second Watch. The monitors kept insisting that they had spotted a diffuse source of cosmic rays somewhere out beyond Neptune. We ran the usual maintenance checks and found nothing, so I ordered the neutrino scopes and X-ray equipment to take a look. They can see it, too."
"What makes you think it's a ghost then?"
"Because there isn't anything out there! Besides which, the source is moving."
"Yes, sir. Moving fast. It appears to be traveling radially outward from the Sun."
"Have you asked Aeneas to do a parallax measurement?"
"Yes, sir. Two-and-a-half hours ago. I expect their reply momentarily." As though to punctuate Bartlett's comment, several readout screens chose that moment to begin displaying data. The half dozen people in the Operations Center turned to watch."
"Well, I'll be damned!" Bartlett muttered incredulously a few seconds later. "They see it too."
"Have you got a velocity vector yet?" Gruenmeier asked.
The watch astronomer nodded, and then hesitated as he read the figures silently. He looked up at Gruenmeier and gulped. "It says here that the radiation source is moving directly away from the sun, toward Canis Minor, sir. The exact coordinates are: right ascension, 07h 39m; declination, plus 05° 18'. And get this. Whatever it is, it's moving at exactly the speed of light!"
Gruenmeier blinked. "It's moving away from the sun?"
Gruenmeier turned to Chala Arnam. "Get me a top priority line to Earth. I will be sending a coded message to the Board of Trustees in about ten minutes.
He turned back to Bartlett. "Get that data reduced fast. I want everything you can deduce about the source in the next five minutes. I will need it for my squirt to Earth. I also want every instrument we have focused on this contact. Aeneas, too. Understood?"
Gruenmeier stopped, suddenly aware of the expressions of his subordinates. "What's the matter with you two? Hop to it!"
Chala frowned. "What's the matter, Julius? What is it?"
"Don't you see? We have a phantom source of high-energy particles moving away from the sun at 300,000 kps on a vector straight toward Procyon. That can mean only one thing."
"They're back, damn it. They're back!"
The younger man leaned forward, rested his arms on the table. "Earlier today, Kiral Papandreas approached Advisor Vischenko concerning a source of radiation SIAAO’s Achilles Observatory first observed some twelve hours ago. When first sighted, the source was on the outskirts of the solar system. Since that time, it has been moving outward from the sun in a straight line on a vector towards the star Procyon. The astronomers are convinced that we are seeing the wake of an object traveling faster than light."
"You said the source was moving away from the sun?" Jutte Schumann asked.
"Merely an optical illusion, Jutte," Kiral Papandreas said from across the table. He quickly reviewing the theory of superluminal shock waves, ending with: "So you see, as it travels through space, a starship will excite the interstellar medium quite vigorously. It will do so over vast distances in essentially zero time. Yet, the resulting radiation propagates only at the speed of light, taking a finite time to arrive where our instruments can observe it. Those particles with the shortest distance to travel arrive first, those from farthest away, last. Thus, it appears as though the source is receding from the observer at the speed of light."
"One minute to Breakout. Stand by." The voice belonged to Promise’s computer, a direct descendant of the original SURROGATE. After a short pause, the computer spoke again. "Thirty seconds. Shields going up."
A series of wedge shaped sections rose from out of the metal hull at the perimeter of the viewdome and quickly converged at the apex to shut off the blackness overhead. All over the ship, similar shields were sliding into place.
Like any other vehicle, Procyon’s Promise displaced the medium through which it traveled. In Promise’s case, that meant a vacuum thin mixture of hydrogen, cosmic dust, and primitive organic molecules. Had the ship been moving at less than superluminal velocity, its progress through the void would have been marked only by an undetectably small warming of its hull plates as it pushed the detritus of stellar evolution aside.
However, once Promise cracked the light barrier, things changed markedly. At FTL velocities, each hydrogen atom became a significant obstruction. As the ship bored its narrow tunnel through space, the interstellar particles refused to be pushed. It was the classic case of the Irresistible Force meeting the Immovable Object. In a situation analogous to the supersonic flight of an atmospheric craft, the confrontation resulted in a shock wave of high energy Cherenkov radiation.
Nor was Promise’s wake the friendly upwelling that follows any watercraft. It was a ravening storm intense enough to fry an unprotected human within seconds. Yet, the very speed that created the phenomenon also protected the starship from harm. Since the radiation of its wake was limited to the mere crawl that is light speed, Promise left its deadly wake far behind in the instant of its creation.
There was a time, however, when Procyon’s Promise would lose its immunity to the titanic forces that its speed had unleashed. For, as soon as the ship slipped below light speed, the trailing wake would wash over it like a wave over a hapless surfer. In that instant, the starship would be engulfed in radiation equivalent to that encountered during a Class I solar flare.
"Everyone ready for breakout?" Braedon asked over the command circuit. Around him, a dozen crewmen were monitoring the ship’s subsystems against the day when they might have to fly home without the computer’s assistance.
"All ready, Captain," Calver Martin, Braedon’s executive officer answered from his console on the starboard side of the bridge.
Braedon nodded. Several seconds later, the computer began the countdown. "Ten seconds ... five ... four ... three ... two ... one ... breakout!"
Braedon felt a tiny lurch. That was all. There was a moment of silence, followed by two hundred voices cheering over the ship’s intercom system.
"Breakout complete. Secure from breakout stations.
"All Department Heads report status and damage." Braedon reached out and touched a control on his instrument panel. A green status light lit up immediately, and the voice that had so recently echoed from the annunciators spoke quietly in his ear.
"We seem to have made it, PROM. What’s our status?"
The computer answered almost before he had finished the question. "We are green across the board. I am still calculating a precise breakout point. Initial observations place us approximately six billion kilometers from Sol. We will need twelve hours to achieve intrasystem velocity."
"How fast are you applying the brakes?"
"I am holding deceleration at 7000 meters-per-second-squared. Do you wish to order a change?" Braedon hesitated momentarily. The figure cited was 650 times the force of gravity on Alpha. Should the internal compensators fail, two hundred crewmembers would be turned instantly to a thin red paste spread evenly over every interior surface facing Sol. Unfortunately, that was an unavoidable hazard. To back down from light-speed at one Alphan gravity would take most of a year.
"No change in programmed deceleration," he said.
"Understood," PROM answered.
"Is it safe to unshutter?" Braedon asked one of the technicians seated directly in front of him.
"The radiation storm peaked five seconds ago and is now declining as predicted, Captain," the man said without taking his gaze off his instruments. "Stand by..." There was a ten second period of silence, followed by: "It is now safe to unshutter."
There are a few semi-plausible FTL methods out there. One of the most famous is Dr. Miguel Alcubierre "Warp Drive", along with Chris Van Den Broeck's improvement. Dr. Alcubierre specifically set out to make a warp drive similar to the one in Star Trek, but obeying the laws of physics. The ship is enclosed in a highly distorted bubble of spacetime. The ship technically is not moving faster than light, the warp bubble is and the ship is carried along for the ride. Problems include: it requires more energy than is contained in the entire universe to set it up, the ship inside cannot see where it is going, the ship inside cannot release the warp bubble and is thus permanently trapped without outside help, quantum mechanics says the bubble will rapidly fill up with deadly Hawking radiation and will otherwise be very unstable, and when the bubble is stopped all the interstellar particles swept up will be emitted as a planet-destroying burst of gamma-rays and high energy particles in the direction of travel.
There are others at Dr. John Cramer's Alternate View archives, Edward Halerewicz, Jr.'s Warp Physics site, Marcelo B. Ribeiro's Warp Drive Theory site, Lawrence H. Ford and Thomas A. Roman's Scientific American article Negative Energy, Wormholes and Warp Drive, David Waite's Modern Relativity site (if you can understand the math), and NASA's Warp Drive When?
More on the fringe is Burkhard Heim and his theory of everything. If the theory describes reality, it could give a form of FTL travel with an artifical gravity propulsion system at no extra charge. You can read a PDF file of the research paper here and the expanded version here.
The Canonical List of StarDrives
If you want to roll your own, you might find the following useful. Noted physicist and Hugo & Nebula award-winning SF author Geoffrey A. Landis has created a catalog of every kind of StarDrive that has ever existed in science fiction. It appears here with Dr. Landis' permission.
- [1.0] Discontinuous Drives ("teleport-like")
- [1.1] Flash gates
- [1.2] "Door" gates
- [1.3] "Permanent" gates (Wormholes)
- [1.4] Teleportation (aka "jump")
- [1.5] "Fold" drive (Teleportation/variant)
- [2.0] Continuous Drives
- [2.1] "Railroad" drives
- [2.2] "Non-railroad" drives
- [2.2.1] Real space drives
- [188.8.131.52] Newtonian space drives
- [184.108.40.206] Post-relativistic space drives
- [220.127.116.11] Tachyonic travel
- [18.104.22.168] Modified local speed of light
- [22.214.171.124] Modified regional speed of light
- [126.96.36.199] Modified universal speed of light
- [188.8.131.52] Tachyonic teleportation
- [184.108.40.206] Other real drives
- [220.127.116.11] "Bubble" drives
- [2.2.2] Alternative space (non-real space drives)
- [18.104.22.168] Alternative space with fixed nodes
- [22.214.171.124] Alternative space without fixed nodes
- [3.0] Modifying the Universe
- [1.0] Discontinuous Drives ("teleport-like"). Discontinuous drives are ones in which the traveler does not traverse the space between origin and destination.
- [1.1] Flash gates. Devices in which the object transported disappears from point X and reappears at point Y.
- [1.1.1] Transmitter to receiver. Teleport in which a discrete transmitter and a receiver are needed. May require a ship, or may not.
- [1.1.2] Transmitter to anywhere. Teleport in which a transmitter is needed, but a receiver is not; the transporter can select the target location ("Beam me down" is the most well-known example)
- [126.96.36.199] Transmitter to anywhere /variant. Transmitter can be transported with the teleportation. See also [188.8.131.52] "Single jump/variant".
- [1.1.3] Anywhere to receiver. Teleport in which a receiving unit is needed, but a transmitter is not. ("Beam me up" is an example of this.)
- [1.1.4] Distant transmitter. A teleport system in which a fixed unit is needed, but this unit can teleport you from a place to another place. (The "point to point" use of the transporter in Trek is an example.)
- [1.2] "Door" gates. Gates in which an opening is made between point X and point Y which exists for some finite time; the object transported then moves though the gate.
- [1.2.1] Portal to portal. A transmitting device to act as the "out" door and a receiving device to act as the "in" door are both required. (e.g. Poul Anderson, The Enemy Stars.)
- [1.2.2] Portal to anywhere. Here the transmitting door opens a receiving door without requirement for any device at the receiving end. ('Tak Halus' (pseud. of Steven Robinette) did a series of stories in Analog in early 70s with this premise)
- [1.2.3] Anywhere to portal. The same as [1.2.2] "Portal to anywhere", but traveling in the opposite direction.
- [1.2.4] Distant portal. Anywhere to anywhere, device located elsewhere. Here "door" opens from X to Y by use of a device at a third location C. The 'door' equivalent of [1.1.4] "Distant transmitter".
- [1.3] "Permanent" gates (Wormholes). "Permanent" here means that these stay open without the requirement of a device, that is, they are a path from X to Y without being energized. There are a wide variety of subsets of this. Recently the most talked-about are Lorentzian wormholes, which are apparently allowed by the general theory of relativity if the presence of negative matter is permitted. General relativity variants include Morris-Thorne spherical wormholes, Visser portals, Kerr ring-wormholes, Einstein-Rosen bridges (nb: which actually collapse before allowing you to traverse them), Tippler rotating cylinders (nb: which don't actually serve as bridges, but at least one SF writer, Poul Anderson, wrote a book which assumed that they did). A non-relativity version is the "mirrors" used in Wolfe's New Sun series of books.
- [1.4] Teleportation (aka "jump"). Here I use "teleportation" to imply something that can transport itself without a fixed transmitter or receiver. Reference to quantum "tunneling" is often made. Some books imply that humans can do this unassisted (Tyger, Tyger/The Stars My Destination). Many more use ships which can "jump" with some device. Here I use 'jump' or 'teleportation' only for the case that physical travel is not required in some alternate version of space, in distinction to some SF writers who use the term or a variant for cases where a ship 'jumps' to some 'hyperspace' (jumpspace, subspace, etc) where it can travel FTL.
- [1.4.1] Single jump. A ship (or person) who can jump from place to destination in a single step, and can select the target.
- [184.108.40.206] Single jump/variant. In the variant, this only works at selected places, and takes you only to selected spaces (The Mote in God's Eye). This type of variant in general can be considered a version of the [1.1] "Flash-gate" discussed above.
- [1.4.2] Multiple-connection. The ship can engage a "jump" drive, which will connect your location in space-time with another location in space-time that is fixed by the universe (may depend on your state of motion in some variants). The connection will vary from place to place, so to go to a given destination you need a "map" of where to go in space to find the place that jumps to the right spot. The analogy is of the universe to a crumpled sheet of paper. An ant can cross from one place on the paper to another where the paper touches itself. (Heinlein, Starman Jones). For some locations, a long trip moving from one place to another to take multiple jumps may be necessary.
- [1.4.3] Multi-jump (Stutter). A ship can jump from place to place, but not far enough to travel in a single jump. Thus, the ship travels by a series of short jumps. In the limit of very short jumps, the ship "appears" to be traveling through space at a "pseudo" velocity without actually having any momentum. (This shades into [1.4.1] "Single jump" as the length of jump gets longer).>
- [1.4.4] Hopscotch drive. Use of any version of a gate or portal to accomplish self-motivated teleportation by having a transmitter transmit a transmitter, so that a ship "bootstraps" across space by continuously beaming itself incremental distances. (Such a drive is somewhere in the fuzzy region between a [2.0] "Continuous" and a [1.0] "Discontinuous drive").
- [1.4.5] FTL by time travel. In FTL by time travel, faster than light travel is achieved by traveling to the destination at ordinary slower-than-light speed, then teleporting backward in time to arrive at the same time you started (e.g. Roger MacBride Allen, The Depths of Time).
- [1.5] "Fold" drive ( Telportation/variant ). A "fold" drive appeals to the "folded space" concept of [1.4.2] "Multiple-connection", but now assumes that the ship can intentionally "fold" space to produce the direct connection between point X and point Y required. Since this categorization is by how the drive appears, and not how it functions, "fold" variants are identical to actual teleport (or "portal") variants, cf. [1.2] "Door gates")
- [2.0] Continuous Drives. Continuous drives are ones in which the traveler does traverse the space between start and finish. A ship gets from point X to point Y by traveling rather than by an instant "jump", although the travel is not necessarily in "real" space. The word "ship-like" is a little fuzzy, since many SF writers use 'ships' to accomplish what is actually teleportation-like travel. This is, I think, because ships are such a great story device.
- [2.1] "Railroad" drives
- [2.1.1] Fixed trail. A "railroad" drive is one in which it is assumed that some physical structure connects two points, and that FTL travel is possible, but only traveling along this structure (as railroad travel is only possible along a railroad). One might appeal to the concept of a cosmic string, or some other astrophysical object. The railroad is in some ways a conceptual link between wormhole-like drives and ship-like drives. If the travel is actually instantaneous, with an object leaving one end appearing at the same time at the other end, the railroad drive becomes a variant of [1.3] "Permanent gate". (e.g. Glen Cook, The Dragon Never Sleeps.)
- [2.1.2] Consumable trail. In a consumable trail, some structure must be put in place between a and b, and the drive consumes this material as it travels in order to produce FTL. Some versions of the Alcubierre drive, for example, require that a structure of negative energy be put in place along the path from x to y, and the ship can then travel between the two points, but destroys the structure as it travels.
- [2.2] "Non-railroad" drives. This section covers continuous drives (that is, drives where the ship traverses space to get to the place desired) which do not require a structure in place in space.
- [2.2.1] Real space drives. Real space drives assume that faster than light travel is possible in physical space. In terms of appearance, all of these drives apparently operate the same way (you go faster than light), and so if I were to keep to my strict classification, these would all be in the same category. The main difference between the drives is how they talk around relativity.
- [220.127.116.11] Newtonian space drives (EMF classification: fakedrive). This version of a FTL drive simply ignores relativity. The ship goes faster than light merely by speeding up to a velocity which is faster than light. (e.g. E.E."Doc" Smith, The Skylark of Space.)
- [18.104.22.168] Post-relativistic space drives (EMF classification: fakedrive). This is a minor variant [22.214.171.124] "Newtonian space drive"; the drive assumes that there is some (yet unknown) "correction" to relativity such that the speed of light is not, in fact, a barrier. Often this correction will be some added term which applies only very close to the speed of light.
- [126.96.36.199] Tachyonic travel. Tachyonic travel notes that faster than light speeds are in fact permitted by relativity for bodies of imaginary rest mass, and assumes that there is some way to reach the faster than light state (often invoking "tunneling") from slower than light states without leaving "real" spacetime. (nb: tachyonic FTL travel still has causality paradoxes in special relativity).
- [188.8.131.52] Modified local speed of light. Drive assumes that the speed of light in the vicinity of the ship can be modified by the drive system in some way, so that although the ship does not exceed the speed of light, it nevertheless can travel faster than 300,000 kilometers per second.
- [184.108.40.206] Modified regional speed of light. Assumes that the speed of light is greater than 300,000 kilometers per second in some places in the universe. Faster speeds can be achieved in other places in the universe.
- [220.127.116.11] Modified universal speed of light. A scientist discovers a way to change the speed of light in the entire universe, and does so. Now any ship can go faster than (what used to be) the speed of light.
- [18.104.22.168] Tachyonic teleportation. The ship and/or person is converted into a stream of tachyons and beamed across space, then reconstituted at the receiver. Actually a variant of [22.214.171.124] "Tachyonic travel" and/or [126.96.36.199.1] "Hyperspace with transmitter and receiver"; listed separately because it is significant that the ship does not travel as a cohesive unit. Other variant names can be used for the particles, which can travel either through real space or some alternative space.
- [188.8.131.52] Other real drives. This covers other ways of dealing with relativity problems without leaving real space. (Usually this involves employing doubletalk and bafflegab.)
- [184.108.40.206] "Bubble" drives (EMF classification: warpdrive). "A bubble of different space is projected around the ship so that the ship can travel faster-than-light while still in realspace." This is listed last, since it is an intermediate step between "real space" drives and alternative space drives, with some nature of both. (This seems to be the FTL system used on Star Trek.)
- [2.2.2] Alternative space (non-real space drives). In SF parlance, often called hyperspace, hyper, jumpspace, FTL space, and other such words. EMF classification: "Type I; hyperdrive: The ships enters some different space during the trip, whether or not time passes for the crew while in this space."
- [220.127.116.11] Alternative space with fixed nodes. Like teleport systems, a alternative space drive may require a fixed station.
- [18.104.22.168.1] Hyperspace with transmitter and receiver. A fixed station boosts the ship into hyperspace; another station is needed to retrieve the ship out of hyperspace. In some variants, only specific locations are nodes which can be used to access hyperspace.
- [22.214.171.124.2] Hyperspace with transmitter. A fixed station boosts the ship into hyperspace. (Babylon-5?)
- [126.96.36.199.3] Hyperspace with receiver. A ship can enter hyperspace on its own, but needs a receiver to get back into real space. Another one I've never seen in SF.
- [188.8.131.52.4] Hyperspace with distant transmitter. In this variant, a fixed machine is needed to access hyperspace, but the machine need not be at either the original location or the destination. I've never seen this in SF; included for completeness.
- [184.108.40.206] Alternative space without fixed nodes.These are the variants of the classic SF hyperdrive. There are probably more examples of this in SF than all other of the drive types combined, and hence it is possible to make very fine divisions within the type. EMF classification: "Type I; hyperdrive: The ships enters some different space during the trip, whether or not time passes for the crew while in this space." The space is often explained away as being a dimension different from the four dimensions we currently can perceive (this explanation typically advanced by people who seem to have only a foggy idea what a "dimension" is). There are many variants based on the supposed "theory" of how the drive works, including entering a space where the speed of light is faster, entering a space which maps onto real space with a mapping such that points far apart in real space are closer in the alternative space, entering a space where the ship expands and then contracts to a different place, entering a space where everything moves at the same FTL speed, etc. Likewise, there are a long list of "conditions" which hyperspace drives are imagined to require. A common one is that the FTL space cannot be entered when "in the gravitational well of a massive body," (Niven, Ringworld series) or that your ship must have a high velocity in real space before you can enter FTL space (Niven, World of Ptavvs, O'Donnell, Fire on the Border) These two are convenient for sf writers, because they explain why spaceships are required. Important questions for hyperspace concepts are whether ships can see and/or dock with each other in hyperspace, whether all ships travel the same speed, and whether a ship can navigate while in hyperspace. These questions can also be asked of [220.127.116.11] "Hyperspace with fixed nodes". I will take this last to be the question used for subdivisions.
- [18.104.22.168.1] "Jump" hyperspace. The destination is fixed when the ship enters the alternative space, either as a function of its position and velocity entering, or else by some settings in the drive. After a ship enters the alternative space, there is no way for it to change the destination. (e.g. GDW's "Traveller" RPG)
- [22.214.171.124.2] Direction hyperspace. A ship's direction is fixed when the ship enters hyperspace (often, but not always, fixed by the direction the ship was traveling when it entered). How far it travels, however, is a variable that can be changed. Usually the distance is proportional to time spent in hyperspace, but may be a more complicated function. The ship may or may not be able to calculate its position in real space while in hyperspace.
- [126.96.36.199.3] Navigable hyperspace. The ship is able to completely navigate in hyperspace. It may or may not be able to calculate its position in real space while in hyperspace. Sometimes the hyperspace may have geography or dangers which must be navigated around.
[3.0] Modifying the Universe. A final category of FTL, not precisely fitting in elsewhere, requires modifying the universe. Some items in this category also could be made to fit other categories.
- [3.1] Modify distance in space. Remove or shrink the space between two points.
- [3.2] Modify the speed of light. Change the value of the speed of light in the region where travel is desired (see [188.8.131.52] "Modified universal speed of light")
- [3.3] Universal parameter change. Gain access to the parameters that describe the universe, possibly by hacking into the operating system that the universe runs. Find the parameters which describe your location. Rewrite these parameters to put you in the place you want to be. (e.g. Greg Bear, Moving Mars)
The EMF (Erik Max Francis) classification
- Type 0; realdrive: A drive which uses tricks of spacetime geometry (a la general relativity) to travel faster than light.
- Type I; hyperdrive: The ships enters some different space during the trip, whether or not time passes for the crew while in this space.
- Type II; warpdrive: A bubble of different space is projected around the ship so that the ship can travel faster-than-light while still in realspace.
- Type III; jumpdrive: The ship travels from one point to another, possibly in multiple jumps, without occupying the intervening space and without the use of a different space to assist the travel.
- Type X; fakedrive: Assume that special relativity or general relativity are incorrect in part or in whole, or just ignore them. Now you can just accelerate at constant gravity until you go faster than light.