"Realistic" FTL

[Darth Raptor]

"Realistic" in this context does not mean "plausible", but rather something closer to "believable". For these purposes I am not so concerned with mechanics as I am with aesthetics. For a setting in which virtually everything else is (to my limited understanding) well within the realm of theoretical possibility, the only fantastic element is the FTL. And while it's powered by pure handwavium, I want to do everything I can to make it seem like it's not so it fits the setting. So what tricks are there, if any, to make FTL propulsion/communication schemes more believable? Imagine if there were some way to cheat around the light barrier and give relativity the finger, what would the machine look like?

So far my thoughts begin with the obvious: Give the technology clearly defined capabilities and limitations and stick to them, but that's true for any fantastic element. What about beyond that? Operating from basic assumptions (the process in question is complicated and energy intensive), I have a machine that is massive, intricate and extremely power hungry. But is that enough? Should I give the FTL staggeringly inconvenient limitations? Should I make it dangerous and/or unreliable? Should it pollute the timeline wherever it goes?

[Stark]

The trick is to stop being a pompous cockflap about how HARD or PLAUSIBLE or REALISTIC your story is. If it has FTL it's unrealistic. Just internalise that and move on. Making it 'inconvenient' isn't making it 'more plausible' - reality isn't like balancing a fucking MMO. You could have the most limited, crazy-fuelled, maths-driven FTL drive ever and it's still a pile of handwaving. So why bother aside from intellectual pride?

[Darth Raptor]

I'm mostly curious as to what people would find the least surprising if it were actually possible. I'm disinclined to make it wonky because it draws attention to it, but it occurred to me that something that's feasible now might be pedestrian in the future, whereas something that's "impossible" now might be pretty buggy in the first few centuries after its discovery. More to do with the idea that "A is harder than B" than trying to achieve some kind of karmic balance.

[Stark]

That style issue of whether it'll be 'pedestrian' in the future is what I mean; who cares? If it performs the story role of moving people about, is treated consistently and isn't given chapters of ridiculous infodump, who cares?

I mean, I've read try-hard scifi with like 3 types of communcations for different roles, two types of very limited FTL and a reliance on wierd psycho-squids but all that didn't make it more 'plausible' - it was just try-hard because it was consistent.

[Patrick Degan]

I'm mostly curious as to what people would find the least surprising if it were actually possible. I'm disinclined to make it wonky because it draws attention to it, but it occurred to me that something that's feasible now might be pedestrian in the future, whereas something that's "impossible" now might be pretty buggy in the first few centuries after its discovery. More to do with the idea that "A is harder than B" than trying to achieve some kind of karmic balance.

The only important matter to your story is that it works and works in a consistent manner. Put as little explanation into it as possible and just get into the meat of your story, which is where you'll need to worry about plausibility.

If you must.... go with the jump drive: your ship flips from A to B in planck-time. The limitations are available energy buildup (which affects range) and accuracy of jump coordinates (which also affects range). Fuck up on the latter and you pop out inside a star or a black hole's event horizon or just in the way of an asteroid, moon, or planet. That's just off the top of my head. You don't need anything more in the way of a description than that, either; those few lines will convey your idea to the readers quite economically.

Really... Read some classic SF —especially from the 50s - 70s. I'd especially recommend Fred Pohl's Gateway for how to handle the idea of FTL in a way that doesn't get in the way of your actual story.

[Covenant]

Just be consistant with it, and don't spend a lot of time going into the science of it unless it is direly important to the story that you do so. FTL, in a story, is like a very fast horse. The more you talk about how fast and tireless this horse is, the more it stands out as unreasonable and ridiculous. If you just say "It's FTL," and move on, you've satisfied your need to have FTL and also to have space stories. The most plausible FTL engines would need to be based on a plausible and much different understanding of the way the Universe works--so in order to make it realistic, you need to make basically everything else seem strange. To just change one single thing is what makes it obviously handwaving--it's like having aerial fightercraft powered by coal fires, if you imagine yourself as a coal-era science fiction writer wanting his faster-than-sound travel (damn them and their saying it can't be done!) but not wanting to change the other criteria of the theme.

Really, if you want a hard sci-fi universe, trade your days of FTL travel for days of STL travel and realistically explore just how fucking vast a single solar system can be. The need for FTL is much decreased when you consider the amount of difficulty comprehending planetary distances, let alone distances out to the outer objects like the oort cloud. And fast STL can still make interstellar travel plausible and entirely reasonable as far as storytelling goes. Magellan's attempt to circumnavigate the globe took more than three years, which could have gotten him more than half the way to Alpha Centauri in a high relativistic ship.

You can't have proxy dickwaving via a powerful interstellar empire and hard sci-fi cred. If you wanna' write a theme, pick a power level and sit there. I've done some research into hard sci-fi themes for a game setting I've got in mind, but it's just used for color, with no pretentions towards anything but making elements of it believable, rather than the whole of it realistic. Once you admit to yourself that really nobody gives a fuck about the hardness (even this board's gravel-eating sons of bitches openly enjoy settings that rate between 'flaccid' and 'yielding' on the hardness level) outside of an intellectual exercise into it, you're free to just have fun and write what you want. If what you want is realism, then accept the reality of it and stop trying to bend it into some false conception of what it has to be. But if people like Asimov or Clarke, who really knew and cared about science, can't be bothered to explain their handwaved magic then I don't know why you should feel you have to either.

[Starglider]

When I designed an FTL mechanism for a RPG campaign, I basically assumed that the universe was a computer simulation, imagined the programming I would do to add the capabilities I wanted to the simulation, then rationalised that from an in-universe perspective. The universe wasn't actually a simulation, it's just that that was the most convenient way for me to visualise it - why bother tying yourself in knots over perceived causality and absolute reference frames, I just take the attitude 'if I know how to program it in principle, then it can exist'.

The actual mechanism created a bubble that had a different inertial relationship with the rest of the universe (en-mass) than matter usually does. The result was Elite-type space flight, and the effect went through several grades depending on the local gravity gradient and interference from nearby field generators, for non-instant approaches to targets and convenient cinematic space-battles. Conservation of energy wasn't violated, so climbing out of a gravity well required dumping energy directly into the drive to compensate for the much lower thrust. Dissipation of the field on collision and the resulting conversion to conventional inertia nullified most of the WMD potential of starships. I'm sure it wasn't fully consistent but it made for a reasonable RPG setting.

[RedImperator]

The most important thing to think through first are the tactical and strategic implications of your FTL drive, and to tweak it if it turns out you've broken your setting (as in, say, "LOL, instant jump to anywhere=defense impossible"). As for dealing with it stylistically, a jump-type drive is probably your best bet, because at least you won't be calling attention to it by hanging around in "hyperspace" or wherever.

[Sarevok]

Why even bother with infodumps in anywhere but a glossary or rpg game fluff text ? Focus on the characters and plot instead with an emphasis on realistic events and onteractions as opposed to "hardness" or "softness" of science within the verse.

[RedImperator]

Focus on the characters and plot instead with an emphasis on realistic events and onteractions as opposed to "hardness" or "softness" of science within the verse.

This is rather worthless advice to someone who has clearly stated he wishes to write realistic science fiction.

[Ariphaos]

There are two aspects to 'realistic FTL'.

One is maintaining Relativity as we know it along with causality. This is easy - have your FTL be rooted in a fixed frame outside of the Universe. There are some things to keep in mind when you do this:

1) x * c only makes logical sense where x <= 1, or if you apply it to a reference frame in a local Universal vicinity - IE, "for most of the Milky Way the Tsukoran Drive has a top speed of roughly thirteen thousand times c when viewed from the static medium frame surrounding the Galaxy."
2) Thus FTL travel can actually be slower than light in some reference frames in this Universe.
3) But letting it be slower than the maximum possible speed creates an inconsistency - meaning, the top speed needs to be faster than or as fast as light in all reference frames.
4) This only refers to how fast an external observer sees you move from point A to point B and violating the energy condition. It says nothing about how long it will take you, from your awareness. You will need to consider this independently.
5) In terms of energy costs, you also need to prevent a perpetual motion drive from being created. The 'easy' way to do this is to either state that the energy costs are astronomical, or require extremely localized travel - IE via stargates crossing several light-years at most.

There are probably others.

---

The other is 'what seems the most logical course based on our current understanding'.

We are aware of one potential faster than light mechanism - the inflationary force. Making use of it or generating it is not -completely- outside of theory. It would seem, though, that in order for it to work, it would have to eat space locally and emit it nonlocally.

So you have to
1) Generate the required energies. The inflationary force requires energies anywhere from the low ZeV range to the GUT range, meaning it would require a particle accelerator anywhere from the size of Mercury's orbit to bigger than the Kuiper belt, along with the power output of a small star.
2) Consistently create the force once you get there.
3) Somehow pick it up light-years away. You would do this by watching for the expansion of space, hopefully targeted by some magical means to a small enough location where you could detect it.

Good luck.

---

The most realistic approach for interstellar empires is, of course: Why do they need FTL at all?

[Samuel]

Make sure that it isn't extremely accurate. Alot of people have commented about materializing inside solid objects as a problem... except given the vastness of space, that is unlikely. It is a problem if you CAN choose where you re-enter reality because you can have exlosive results.

[Stark]

The most important thing to think through first are the tactical and strategic implications of your FTL drive, and to tweak it if it turns out you've broken your setting (as in, say, "LOL, instant jump to anywhere=defense impossible"). As for dealing with it stylistically, a jump-type drive is probably your best bet, because at least you won't be calling attention to it by hanging around in "hyperspace" or wherever.

It shouldn't break his setting unless he's adding it as an afterthought. So long as he realises that the type of FTL he uses will shape the setting he'll be fine.

[Junghalli]

You could try researching real world theoretical FTL concepts like the Alcubierre warp drive and then handwaving away all the realism problems with it (like the ridiculous energies required). Other than that FTL is pretty much magic so there isn't really any way to make it realistic.

One thing that does occur to me: FTL in an otherwise hard SF universe always struck me as being schizo-tech, personally. I mean, as a matter of consistency I would think if you could give relativity the finger it implies the technology to basically make reality your bitch. It just seems awfully convenient that relativity has such an easy loophole that a civilization that's otherwise restricted to realistic tech can flip the light limit the bird. I suppose strictly speaking it's no less "realistic" than any other way of doing it, but it just feels weird to me.

On that score, one possibility to play with is the idea that the FTL is a portal network left behind a very advanced race that could basically bend reality around their little fingers, and humans and any other races that may be around are just using the portals without being able to build or understand them.

If you want a totally hard SF universe, you could also try eliminating FTL altogether. Larry Niven managed space opera without FTL in the earlier portions of the Known Space timeline. It becomes a lot easier too when you consider that by this point we really should not be restricted to normal human lifespans - STL travel is a lot less problematic when a 300 year trip is something the people alive now could easily be around to see the end of.

[Havok]

I dunno... look at how Star Wars did it. It is just there. People use it. You need a computer to operate it. It can break, but you can fix it. It isn't obtrusive. It's just a means of getting around. Who cares how it actually works. Do you care how your car works? As long as it gets you from A to B and doesn't make any bad noises or any bad lights come on everything is fine right?

[RedImperator]

I dunno... look at how Star Wars did it. It is just there. People use it. You need a computer to operate it. It can break, but you can fix it. It isn't obtrusive. It's just a means of getting around. Who cares how it actually works. Do you care how your car works? As long as it gets you from A to B and doesn't make any bad noises or any bad lights come on everything is fine right?

The reader doesn't have to worry about it, but the author damn well does. Trust me, it's shitloads easier to write when you know the boundaries of your imaginary technology. Besides that, how is he expected to maintain internal consistency if he doesn't have a set of rules in mind?

[Ford Prefect]

Honestly, there's nothing wrong with coming up with rules for what is basically complete magic: look at the Langston fields in A Mote in God's Eye, for example. The Langston fields have no actual mechanism or science behind them, but they do have a codified set of hard rules which govern how they behave. This even includes a couple of concessions to drammatic necessity. Above all else, this allows for consistency, and it means you don't have to feel silly when people go 'oh, but surely they could have done abc with xyz'.

[Lord of the Abyss]

There are two aspects to 'realistic FTL''

One is maintaining Relativity as we know it along with causality.

One clever idea I ran across in one novel about maintaining casualty. It turned out that every time you went FTL, you arrived in a near identical alternate universe. Trying to use FTL to send messages into the past didn't violate casualty because it wasn't your past.

The most realistic approach for interstellar empires is, of course: Why do they need FTL at all?

To hold together and remain something close to culturally unified.

One thing that does occur to me: FTL in an otherwise hard SF universe always struck me as being schizo-tech, personally. I mean, as a matter of consistency I would think if you could give relativity the finger it implies the technology to basically make reality your bitch. It just seems awfully convenient that relativity has such an easy loophole that a civilization that's otherwise restricted to realistic tech can flip the light limit the bird. I suppose strictly speaking it's no less "realistic" than any other way of doing it, but it just feels weird to me.

Yeah, but sometimes reality works out that way. Nuclear energy used to be regarded as almost as hard; tapping it was regarded as implausible because it would require either some magictech make-atoms-disintegrate effect ( such as in Olaf Stapledon's Last And First Men ), or somehow working on each atomic nucleus one at a time. Then, it turned out that Nature has provided a far easier method of releasing nuclear energy on a mass scale in the form of chain reactions. Some similar shortcut could be found for FTL.

On that score, one possibility to play with is the idea that the FTL is a portal network left behind a very advanced race that could basically bend reality around their little fingers, and humans and any other races that may be around are just using the portals without being able to build or understand them.

Another idea is to have the drive be salvaged from a much more advanced race; I recall the novel Procyon's Promise where they got FTL, artificial gravity and tractor beams from an alien starship maintenance manual they dug from a garbage dump - and they had no clue how it all worked, they just knew what buttons to push. Or even a gift, or bought ( "Give us the right to dismantle Jupiter and we'll hand you the design for our drive" ). Or there's always the classic "discovered by accident" explanation, which has obvious uses if you want disasters ( they didn't know it would DO that ).

[Havok]

I dunno... look at how Star Wars did it. It is just there. People use it. You need a computer to operate it. It can break, but you can fix it. It isn't obtrusive. It's just a means of getting around. Who cares how it actually works. Do you care how your car works? As long as it gets you from A to B and doesn't make any bad noises or any bad lights come on everything is fine right?

The reader doesn't have to worry about it, but the author damn well does. Trust me, it's shitloads easier to write when you know the boundaries of your imaginary technology. Besides that, how is he expected to maintain internal consistency if he doesn't have a set of rules in mind?

It takes two weeks at (insert name of your lightspeed here) to get from planet X to planet G. There, I just established the boundaries of your imaginary tech. If you aren't writing a story about the beginning of the tech being discovered or about space engineers that fix it, you just treat it like a piece of technology that everyone knows. There is no point in over complicating your writing and/or boring the shit out of your readers with what is imaginary technobabble in the first place.

[Lord of the Abyss]

I dunno... look at how Star Wars did it. It is just there. People use it. You need a computer to operate it. It can break, but you can fix it. It isn't obtrusive. It's just a means of getting around. Who cares how it actually works. Do you care how your car works? As long as it gets you from A to B and doesn't make any bad noises or any bad lights come on everything is fine right?

The reader doesn't have to worry about it, but the author damn well does. Trust me, it's shitloads easier to write when you know the boundaries of your imaginary technology. Besides that, how is he expected to maintain internal consistency if he doesn't have a set of rules in mind?

It takes two weeks at (insert name of your lightspeed here) to get from planet X to planet G. There, I just established the boundaries of your imaginary tech.

A definition which leaves huge, possibly plot important holes. Can it be detected in transit ? How about upon going STL ? Can an FTL vessel be intercepted in transit ? Can the drive fit in a missile ? Does it move through another space, or this one ? In the former case, can the FTL object reappear inside solid objects ? Appear in atmosphere ? What do you see if you look out a porthole or hull mounted camera in transit ? What happens if it breaks in operation ? And so on.

Without establishing answers to such questions beforehand, you greatly increase the risk of answering them one way on page three, and another on page 50.

[Darth Hoth]

But if people like Asimov or Clarke, who really knew and cared about science, can't be bothered to explain their handwaved magic then I don't know why you should feel you have to either.

If we are mentioning hard SF examples, Asimov is not the name we want. His stories (the ones that are not obscure, at least) are about as hard as Wars or Doc Smith at his best. (And yes, this was a NITPICK!)

So far my thoughts begin with the obvious: Give the technology clearly defined capabilities and limitations and stick to them, but that's true for any fantastic element. What about beyond that? Operating from basic assumptions (the process in question is complicated and energy intensive), I have a machine that is massive, intricate and extremely power hungry. But is that enough? Should I give the FTL staggeringly inconvenient limitations? Should I make it dangerous and/or unreliable? Should it pollute the timeline wherever it goes?

If the machine needs very large amounts of energy, this might be a severely limiting factor in itself, depending on what you use for "hard" power generation and storage. Be sure to think through the consequences that being able to achieve energies for "realistic" theoretical FTLs will have on general society, and how common/rare it should be to do so. In this kind of setting, I would imagine that FTL would be fairly rare and expensive (government/military only, more or less, and used as little as possibly due to high costs).

The important thing to consider would be what feel you are aiming for; is it to be relatively small scale, with the "hyperdrive" being slow and/or unreliable, invoking an "age of sail" feel of the setting? Or would you want something larger, perhaps akin to Starship Troopers (which is fairly hard, as such things go, except for psychics and standard handwavium such as FTL)? Are there reliable FTL means of communication ("hyperwave radio") or is the multistellar polity held together by messengers and military governors like a Roman Empire?

Scientifically a realistic FTL cannot be done, so the best one can achieve is "style over substance" as far as hardness goes. Going by gut feeling alone, most people will consider an FTL drive "harder" the lousier it is, just as minimalist numbers on other matters are usually accepted as more realistic. If one looks at actual mechanisms this does not necessarily make sense (as any kind of reasonably practical FTL is impossible for all we know, and impossibility does not have degrees); it depends on the audience and their education and mindset also, I guess.

[Lord of the Abyss]

The most realistic approach for interstellar empires is, of course: Why do they need FTL at all?

To hold together and remain something close to culturally unified.

If they are going to be culturally unified, they are most likely all human. If they are all human, there is no need to bring in other planets.

Unless you want a story set on two or more planets. Or humans from Earth on a world that isn't Earth. Or a story about the difficulties in holding together a multiplanet empire. Or any number of things.

[Ariphaos]

To hold together and remain something close to culturally unified.

Some reason why they wouldn't be? A neighboring star can do a lot of damage if it goes rogue. It is in the best interests of neighborly types to make sure that doesn't happen.

Unless you want a story set on two or more planets. Or humans from Earth on a world that isn't Earth. Or a story about the difficulties in holding together a multiplanet empire. Or any number of things.

Mars, Luna, Venus, and the Galilean satellites are all terraformable. If we REALLY like rocks we can always do something insane like tow Titan and Mercury into a more respectable orbit and make Ceres into a real world. Suddenly the Solar System goes from a single inhabited planet to a dozen.

[RedImperator]

I dunno... look at how Star Wars did it. It is just there. People use it. You need a computer to operate it. It can break, but you can fix it. It isn't obtrusive. It's just a means of getting around. Who cares how it actually works. Do you care how your car works? As long as it gets you from A to B and doesn't make any bad noises or any bad lights come on everything is fine right?

The reader doesn't have to worry about it, but the author damn well does. Trust me, it's shitloads easier to write when you know the boundaries of your imaginary technology. Besides that, how is he expected to maintain internal consistency if he doesn't have a set of rules in mind?

It takes two weeks at (insert name of your lightspeed here) to get from planet X to planet G. There, I just established the boundaries of your imaginary tech. If you aren't writing a story about the beginning of the tech being discovered or about space engineers that fix it, you just treat it like a piece of technology that everyone knows. There is no point in over complicating your writing and/or boring the shit out of your readers with what is imaginary technobabble in the first place.

As Lord of the Abyss said, you didn't come close to establishing the boundaries. Here's one you didn't answer: can you turn it on anytime and anywhere you want? If that's the case, battles are going to last just long enough for one guy to realize he's losing and jump away. Unless it's possible to somehow jam or block someone from going FTL, or it takes time to activate, or it's so delicate it's the first system to fail (though in that case, people might simply avoid battle entirely unless they have a clear advantage, in which case the OTHER guy will avoid battle). And what about where you emerge from FTL? Can that be anywhere, too? Better hope not if you're writing about interstellar empires, because under those conditions, an interstellar empire will be hopeless (unless there's planetary shields or somesuch magic, but DR wanted to limit his handwavium to FTL). And then there's the whole problem of causality. How are you going to deal with that? Most writers just ignore it, but it's still something that ought to be considered.

And where's this idea coming from that if you think through your imaginary technology, you will therefore bore your readers with technobabble? How does one follow from the other? I spent months researching real-life and plausible future space technologies, astronomical facts, PLA military ranks, space elevators, spin gravity, even common recipes for pho. 90% never shows up on the page; it's in the background, informing the characters' actions without being explicitly stated. Yes, it's possible that a writer will be tempted to show off all his hard work by putting his technobabble on the page, but why are we assuming Darth Raptor is the kind of hack who would do that? And even if he slipped up and let it happen once or twice, that's what revisions are for. You can delete technobabble with hardly a thought or a worry. If it turns out a major plot development is based on a universe-breaking ability you gave your magictech without thinking, on the other hand, then you're up shit creek.

[Junghalli]

I personally second what Atomic Rocket say about FTL (and what some people here have touched on): the best approach is probably to figure out what sort of universe you want first and design your FTL around that. It's magic anyway, so the rules are pretty much always going to be arbitrary.

Be sure to think through the consequences that being able to achieve energies for "realistic" theoretical FTLs will have on general society, and how common/rare it should be to do so. In this kind of setting, I would imagine that FTL would be fairly rare and expensive (government/military only, more or less, and used as little as possibly due to high costs).

If you treat the energy needed for FTL "realistically" you logically get a society with technology that makes the Culture look wimpy by comparison. I believe the energy needed to make an Alcubierre-Van Den Broeck warp bubble is on the order of what you'd get by smashing a solar mass of matter and antimatter together. I'm not sure about wormholes but I believe they require similarly ludicrous energy.

Unless you want a story set on two or more planets. Or humans from Earth on a world that isn't Earth. Or a story about the difficulties in holding together a multiplanet empire. Or any number of things.

Those things could be done in an STL universe. Story set on two or more planets? Have them be in the same solar system, or be sure to include decades-long trips inbetween. Humans from Earth on a world that isn't Earth? Easily achieved with slowboats. Holding together an interstellar empire? That's a lot harder without FTL, but that can be part of the fun of it. One thing that'll help is that by this time period we probably won't be limited to normal human lifespans. Decades-long journeys are less onerous when everyone's immortal.

I'm working on an STL space opera universe myself.

And what about where you emerge from FTL? Can that be anywhere, too? Better hope not if you're writing about interstellar empires, because under those conditions, an interstellar empire will be hopeless (unless there's planetary shields or somesuch magic, but DR wanted to limit his handwavium to FTL).

You can get big power blocs in a MAD universe. Just look at the Cold War. Huge balls-out interstellar wars are out though, unless you're willing to go the whole hog and describe the complete collapse of civilization.

Yes, it's possible that a writer will be tempted to show off all his hard work by putting his technobabble on the page, but why are we assuming Darth Raptor is the kind of hack who would do that?

And putting technobabble on the page need not necessarily mean giant self-indulgent infodumps. The show, not tell rule can be applied here: if technobabble goes on the page, it needs to be relevant to the plot. Look at Peter Watts's work: he puts all sorts of esoteric stuff on the page that in the hands of a less skilled author would be self-indulgent infodumping, but he manages to work it organically into the story and the result is his stories are fascinating reads if you're interesting in that kind of stuff.