Plausible Sci-Fi FTL

[0111narwhalz]

Before starting this discussion, I'd like to make a couple things clear. Please read and comprehend these points prior to participation, as they're important to the purpose of the discussion.

1. This is a science fiction discussion. A certain "softness" of the science is expected.

2. "Plausible" is here used to mean "close enough to reality that someone who payed attention in high school physics wouldn't scoff at it."

3. FTL implies either matter transport or information transport. Some forms of plausible FTL allow both, others are exclusive to one. Both inclusive and exclusive are encouraged.

4. Don't bring the "pick two" here. We'll assume a simplified approach without the interrelations between relativity and causality. Basically, take the "don't look too close" approach.

5. If you really have to bring the "pick two" around, realize that we're positing that FTL is possible, so you'll have to drop R or C.

6. Actual explanation is far more interesting than vomits of technobabble. Try to throw something together that accurately describes the concept before resorting to nonsense.

7. Internal consistency is valued above consistency with real physics, but don't stray too far.

With that out of the way, here's the topic of discussion: 
Create a plausible method of faster-than-light travel and/or communication. You may create your own, or build upon someone else's, but don't rip people's drives apart.

I'll begin.
Spacefolder FTL drives are the familiar "wormhole" drive. They fold space in an inaccessible "fourth spatial dimension" such that origin and destination approximate the same position, then puncture a tunnel through the intervening space. Spacefolders require advanced knowledge of gravity and fourth-dimensional geometry, and may require species of matter with interesting effects on space, such as exotic matter. This FTL paradigm may allow coherent matter to transit, but it may also restrict passage to bare mass or information. This depends upon the math and the size of wormhole possible.

[Nibb31]

There is no point in this sort of conversation. Given your numbered points there, just use any magical plot device that suits your narrative and give it a cool name.

Edited August 11, 2016 by Nibb31

[KSK]

One of the more interesting 'FTL' drives I've read about is the Shapirov drive (never actually referred to as such but I need a name for it!) briefly described in Isaac Asimov's Fantastic Voyage II: Destination Brain.

For those that haven't read it, or seen it, the original Fantastic Voyage was basically a cold war novel in which the balance of power was maintained by the ability to miniaturise things rather than by nuclear weapons. An eminent scientist on one side makes a breakthrough in miniaturisation physics and defects to the other side. Unfortunately, during his extraction, he suffers a brain injury which a) puts him in a coma and b) can only be treated from inside the body. Cue, a miniaturised sub and it's crew sent in to the scientist's body for a spot of microsurgery.

Asimov wrote the book of the film but was never really satisfied with the handwavium powered miniaturisation device. Fantastic Voyage II was his own novel, based on a related premise but with, amongst other things, a much more coherent explanation of miniaturisation and its ramifications. It was pretty much a classic example of 0111narwhalz's seventh point - the physics were clearly slightly bunk but they were internally consistent and their ramifications drove a lot of the plot.

There is a point to this.

Miniaturisation in FV II was supposed to work by reducing the size of Planck's constant over a finite volume of space. It was energy intensive, inefficient and metastable which made it very dangerous for a variety of reasons. Shapirov (the Soviet scientist who developed the technique in the first place) had a theory that Planck's constant and the speed of light were linked. Decrease one and the other should increase to match. The problems with miniaturisation arose because the two constants were uncoupled. Figure out a way of coupling them and firstly miniaturisation becomes an easy, stable and energy efficient process and secondly, faster than light travel becomes possible. Or rather the speed of light becomes arbitrarily high such that a suitably miniaturised starship can travel faster than 3x10^8 m/s without violating relativity.

 

Edited August 11, 2016 by KSK

[Scotius]

Why don't you go with Alcubierre Drive? We don't know how to build one (yet), but apparently science behind it holds the water - at least theoretically.

[DDE]

My preferred self-consistent drive design is a warp drive based on advanced graviton manipulation tech. It allows a pocket of space - including the ship - to travel at FTL speeds; said pocket's cross-section in non-curved space is microscopic, eliminating the threat of FTL collisions with minor particles, while large gravitating objects cause the field to collapse; thus FTL kinetic kill systems are out. Furthermore, an FTL jump results in no change of velocity relative to normal space, thus creating the non-trivial issue of settling into a reasonable orbit. I'm basing that behavior on KSPI.

Sure, Einstein gets defenestrated, but I'm more concerned with conservation of energy.

[p1t1o]

Im a fan of the "Parallel hyperspace with compressed distance" mode - you shift your ship (either through a physical "portal" such as a wormhole or artificially induced "rent", or by "phasing" your ship via manipulation of energy and fields into the other realm) to a universe parallel to this one, where a unit of distance traveled equated to many units of distance traveled in our universe, sidestepping FTL by effectively raising the speed of light. Sortof.

[MaxwellsDemon]

Once upon a time, I started to write some science fiction stories.  I was inspired by the game 'Traveller,' Poul Anderson, Asimov, and Niven in particular, and wanted to stay as close to 'hard' science fiction as possible.

Eventually, I realized two things:   1) Almost all of what I came up with was derivative rather than original, and 2) the original stuff usually didn't end up making a whole lot of sense.   (For instance:  I had this dramatic image of a space warship suddenly surrounded by a cloud of icy particles as it vented its atmosphere prior to combat, to avoid explosive decompression.  I loved it.   But i couldn't reconcile it with the terrible waste of resources of sending out your atmosphere into the void and then having to replace it later...)  I did like playing with real and almost-real technologies like railguns, particle beams, and electro-magnetic defense shielding.  I went through a phase where my 'space marines' a la Starship Troopers were armored with mirrorlike reflective armor (think old-style Cylons) against laser attack, but then I realized that when you reflect a laser, it goes somewhere else, perhaps somewhere in your own ranks and takes out one of your buddies, so that was out...

Anyway, the "Collins Drive"* I came up with was generally along the lines of a 'stutterwarp' or phasing system like in Anderson's Flandry books, and I imagined it like a needle and thread weaving through the fabric of space-time (making the use of the term fabric particularly apt), where a vehicle in "our" space-time is not actually moving faster than light at any given point, but "skips" along at a speed that ends up being FTL.  I envisioned a generator that 'wove' through the fabric in a way that could be visualized as a sine wave, and then postulated that (a la Flandry) a warship would need to match phase with a target in order to hit it-- so, to avoid that, one could hook up several generators with varying wave patterns to make the pattern complex and harder to match; and I decided that it was reasonable that gravity would have an effect on the 'fabric,' basically making it a 'denser weave' so that you could flicker in and out of phase in any gravity field, but that it would be much less efficient, to the extent that FTL "velocities" were unattainable deep in a gravity field without a LOT of power.

It held some water storywise, anyway.  But as I said, it was basically derivative rather than original.

* Ostensibly named after the inventor, Adrienne Collins, and a bit of a nod to Apollo 11 astronaut Michael Collins.  I was elated by the coincidence of shuttle commander Eileen Collins, but that was years after I was fiddling with these stories...

[regex]

I've been a fan of Battletech's jump drive or something similar for gating access to the stars.  30LY (or similarly limited) range, fragile large-scale machinery, long power-up times, instantaneous travel.  Makes a certain amount of handwaving sense as well, save for the conservation of momentum after a "teleport".  It's interesting that if you add that back into the system you can generate near-relativistic weapons by simply making a few well-placed jumps near handy stars before jumping to the target...  Anyway, the BT jump drive is pretty cool for creating localities of government, with "borders" in interstellar space, helps drive conflict.

Honestly though, for a narrative I might write (and I probably won't), I'd lean more towards life-extension through whatever means and a beamrider network ala Orion's Arm because it's far more plausible that we as a species would go that route.  Use robotic/human supervised antimatter construction ships to build stations in strategic locations and then travel the route at some 0.7c.  I think FTL is ultimately a pipe dream and we're going to have to slog to space.

[MaxwellsDemon]

19 minutes ago, regex said:

I think FTL is ultimately a pipe dream and we're going to have to slog to space.

Literal FTL is definitely a pipe dream.  But if physics-as-we-know-it is merely a special case within a more-general field of physics, as with Einstein not contradicting Newton but rather showing Newton as a special case of a more general situation, then there might be another way to get there.  But it still won't be possible to speed up and surpass the speed of light...

[regex]

6 minutes ago, MaxwellsDemon said:

Literal FTL is definitely a pipe dream.  But if physics-as-we-know-it is merely a special case within a more-general field of physics, as with Einstein not contradicting Newton but rather showing Newton as a special case of a more general situation, then there might be another way to get there.  But it still won't be possible to speed up and surpass the speed of light...

Eh...  I still feel like we're never going to find that "special case", or it's going to require so much energy that we'll never be able to take advantage of it, but that's just me.  Unfortunately sublight isn't a super-exciting narrative device if you're talking strictly space-opera, so there's that.

[wumpus]

13 hours ago, 0111narwhalz said:

Before starting this discussion, I'd like to make a couple things clear. Please read and comprehend these points prior to participation, as they're important to the purpose of the discussion.

1. This is a science fiction discussion. A certain "softness" of the science is expected.

2. "Plausible" is here used to mean "close enough to reality that someone who payed attention in high school physics wouldn't scoff at it."

3. FTL implies either matter transport or information transport. Some forms of plausible FTL allow both, others are exclusive to one. Both inclusive and exclusive are encouraged.

4. Don't bring the "pick two" here. We'll assume a simplified approach without the interrelations between relativity and causality. Basically, take the "don't look too close" approach.

5. If you really have to bring the "pick two" around, realize that we're positing that FTL is possible, so you'll have to drop R or C.

6. Actual explanation is far more interesting than vomits of technobabble. Try to throw something together that accurately describes the concept before resorting to nonsense.

7. Internal consistency is valued above consistency with real physics, but don't stray too far.

With that out of the way, here's the topic of discussion: 
Create a plausible method of faster-than-light travel and/or communication. You may create your own, or build upon someone else's, but don't rip people's drives apart.

I'll begin.
Spacefolder FTL drives are the familiar "wormhole" drive. They fold space in an inaccessible "fourth spatial dimension" such that origin and destination approximate the same position, then puncture a tunnel through the intervening space. Spacefolders require advanced knowledge of gravity and fourth-dimensional geometry, and may require species of matter with interesting effects on space, such as exotic matter. This FTL paradigm may allow coherent matter to transit, but it may also restrict passage to bare mass or information. This depends upon the math and the size of wormhole possible.

1.  "Softness" usually works with social sciences where you argue "completely breaking established laws" is always more than 5% probable (humans are just to unpredictable and "the literature" isn't a strong base).  Relativity has a "whole-lotta-nines" of correctness.  You might be able to establish an unlikely theory (like the "Alcubierre Drive" works), but keeping the rest of the science is going to be hard (one "soft spot" would be entering and exiting the "Alcubierre bubble": I'm not sure anybody has suggested a means for that).

2.  My HS science barely covered relativity (and I had two years of physics), so this might work.  You aren't trying plausible at that level.

3.  I'm assuming information transport.  Transport matter without information and you will likely get pure energy as that would probably be the lowest form of entropy possible.  I can understand information without matter (but will likely require energy), but not matter without information (which just doesn't make sense except as background entropy).

4.  Go read any explanation of Relativity by Einstein.  Causality is central to relativity and violating C implies violating causality.  Look at how silly Star Trek is and at least they get this right.  Get it wrong and you can't even "tech the tech" right.

5.  Relativity is right, there is no question.  Causality takes a beating in quantum theory (although never quite shown to be wrong during experiments) as well, so that is the one to go.

6.  If you are going "soft" you get technobabble.  You could go with something like Alcubierre and lose casuality and have a real explanation, but getting it mostly right will be *hard*.  There is a reason the "golden age of Sci-fi is 10", because once you go deeper into (any one) science you know more about it than any writer who doesn't specialize in it.  Don't ask about Turtledove and the US Civil War buffs.

7.  Internal consistency + non-casual universes don't go too well.  Expect to wind up with something like "He built a Crooked House".

 

[Bill Phil]

Atomic rockets ftl page has a lot of good stuff in it.

Narratively, focus on the effects, limitations, and uses for the drive. The technical side of things doesn't matter so much.

[MaxwellsDemon]

6 minutes ago, wumpus said:

Don't ask about Turtledove and the US Civil War buffs.

 

Or Harry Harrison (much as I enjoyed Deathworld and the Stainless Steel Rat).

 

-- a Civil War buff

21 minutes ago, regex said:

Eh...  I still feel like we're never going to find that "special case", or it's going to require so much energy that we'll never be able to take advantage of it, but that's just me.  Unfortunately sublight isn't a super-exciting narrative device if you're talking strictly space-opera, so there's that.

I'd bet against it myself, but I'm leaving some wiggle-room since my omniscience is limited to the point of nonexistence.   

Asimov, I recall, did specifically refer to FTL drives as narrative/dramatic devices rather than being scientific ones.

[regex]

6 minutes ago, MaxwellsDemon said:

Asimov, I recall, did specifically refer to FTL drives as narrative/dramatic devices rather than being scientific ones.

And he was correct.

[MaxwellsDemon]

The Good Doctor usually was.

But, as far as the OP goes, we're talking "plausible" rather than "possible;" so, as a narrative/dramatic device, we need to first assume the possibility of a FTL drive, and then construct what would least interfere with what we know about the universe and physics... something that requires the shortest possible leap of logic, as it were.

 

(Incidentally, in my own SF ideas I referred to above, I specifically chose a method that would cause time to elapse-- for the characters at least-- during the transit, for storytelling purposes.  A sudden shift to a new location didn't fit the style of what I was going for.)

Edited August 11, 2016 by MaxwellsDemon
Additional comment

[Robotengineer]

Alcubierre Drive. It's plausible and being looked at by real scientists (Eagleworks Labs). As far as the real-life possibility of FTL, we can't definitively say it is impossible. For all we know a 'new' physics could be developed that is to relativity what relativity was to newtonian physics. 

[regex]

Curious what happens when an Alcubierre field interacts with massive object.  You're pretty much warping space.

[magnemoe]

1 hour ago, Bill Phil said:

Atomic rockets ftl page has a lot of good stuff in it.

Narratively, focus on the effects, limitations, and uses for the drive. The technical side of things doesn't matter so much.

This, also note that limitations will affect setting, Niven's hyperdrive could not be used close to stars or other bodies so you still had to reach outside Neptune in reasonable time to activate it. 
The Anderson drive in mote in the gods eye was an jump drive who had jump points this also create an obvious strategic position more so in that both humans and computers get dizzy by jumping. 
An drive who is inaccurate with en accuracy of 1 au (10x distance from earth to sun) on exit but no other restrictions would still require an decent spaceship but would be useful in the outer solar system and be very nice to get away from enemies. So if you want space pirates the Anderson drive would be perfect as you have to jump from solar system to solar system at specified points while the inaccurate drive would be hopeless. 

[0111narwhalz]

3 hours ago, MaxwellsDemon said:

we need to first assume the possibility of a FTL drive, and then construct what would least interfere with what we know about the universe and physics... something that requires the shortest possible leap of logic, as it were.

Thank you. This is exactly what I was trying to convey with the points in the OP.

4 hours ago, wumpus said:

3.  I'm assuming information transport.  Transport matter without information and you will likely get pure energy as that would probably be the lowest form of entropy possible.  I can understand information without matter (but will likely require energy), but not matter without information (which just doesn't make sense except as background entropy).

By "information" I meant data, in the form of a beam of light or something. Some FTL devices allow you to beam lasers through, others let whole ships through too, while still others disallow energy-only information (such as lasers) but let ships through. This is generally a requirement imposed purely by the author's desire to tell a specific kind of story. I realize it's unlikely that the ship-but-no-radios FTL has any deep-seated merit, but considering the territory, it's all good.

------------------------------

My personal favorite:

Since hyperdrives are so popular, I imagine a generalization and extension of the hyperdrive, known as the polyspatial drive. Rather than a single alternate space that maps to realspace, the polyspatial FTL paradigm posits a continuous series of "layers" of a hypersphere, each of which is accessible. Think of an onion. The deeper you go, the greater the ratio between realspace distance and your distance. Ships are propelled between layers via "translation drives," which have a variety of interesting effects on biology and computers. Objects have a finite thickness, which makes it so you can't fit an infinite number of vessels on a single radius. Certain "bands" are allocated to private civilian, commercial freight, and military traffic, just as radio has. For the benefit of plot, space possesses a certain amount of "spatial fluid" (Yeah, you heard me. I said it. It's basically aether.) which flows freely between layers according to something akin to gravity. In other words, deeper layers possess more spatial fluid, which manifests itself as pressure and drag. Go too deep, and your ship will become nearly immobile. Go way too deep, and your ship is crushed like a soda can under a boot. Spatial fluid can be impelled and accelerated like air. This means that you don't need inefficient reaction engines to drive around between stars; you can instead use propeller or turbine engines.

These features allow for the following characteristics:
-Ability to enter/exit FTL flight at will
-Ability to intercept and interact with vessels in FTL flight
-Technically not violating relativity, since you're covering less distance in the same time, then turning it into more, rather than actually speeding up
-Streamlined, nice-looking ships
-Large payload fractions for starships
-Shipping lanes

[StrandedonEarth]

Well, there is also the Crazy Eddie drive, aka the Alderson drive, as described in The Mote in God's Eye. 

[DDE]

12 hours ago, MaxwellsDemon said:

 

 

(Incidentally, in my own SF ideas I referred to above, I specifically chose a method that would cause time to elapse-- for the characters at least-- during the transit, for storytelling purposes.  A sudden shift to a new location didn't fit the style of what I was going for.)

If we maintain conservation of momentum, give the jumps a somewhat low accuracy, and keep the torchdrives reasonably weak, then we can pad the story due to all the sublight velocity match ops where conventional orbital mechanics are involved.

At least, that's how I made my drive.

[MaxwellsDemon]

5 hours ago, DDE said:

If we maintain conservation of momentum, give the jumps a somewhat low accuracy, and keep the torchdrives reasonably weak, then we can pad the story due to all the sublight velocity match ops where conventional orbital mechanics are involved.

At least, that's how I made my drive.

Also similar in a way to the "drive" in David Drake's Daniel Leary/Adele Mundy RCN series.  Though there the transition is not actually instantaneous-- the ships spend considerable time in the Matrix, "sailing" between universes/electrical potentials-- it's not a place where two ships can interact, so all of the action happens sub-light.

[DDE]

21 minutes ago, MaxwellsDemon said:

Also similar in a way to the "drive" in David Drake's Daniel Leary/Adele Mundy RCN series.  Though there the transition is not actually instantaneous-- the ships spend considerable time in the Matrix, "sailing" between universes/electrical potentials-- it's not a place where two ships can interact, so all of the action happens sub-light.

I wouldn't go that deep; I never even studied the wave-particle nature of light, so I'd like to avoid making a fool of myself.

Which means that it's plausible, in my universe, to conduct an FLT jump, and then fire up a hydrolox or UDMH-N2O4 sublight "drive".

[MaxwellsDemon]

5 minutes ago, DDE said:

Which means that it's plausible, in my universe, to conduct an FLT jump, and then fire up a hydrolox or UDMH-N2O4 sublight "drive".

Oh, yeah.   What I meant to stress that, in Drake's RCN series, the drives are chemical/nuclear drives inside atmosphere, and then "High Drive" (matter/antimatter) in vacuum, the explanation being that there's cumulative wear to the High Drive engines from the matter/antimatter reactions, so it's best used sparingly in a more matter-rich environment like an atmosphere.   I don't know how much scientific water that holds, but it at least sounds reasonable.   But what it does mean is that ships use three different methods-- two kinds of reaction drive and the "sailing" rig-- to get around.  (The series is consciously based on a sort of sailing-ship-era pace, with the Jack Aubrey/Stephen Maturin novels of Patrick O'Brien an obvious and acknowledged influence, so the parallels to oceanic travel are deliberate.)

Edited August 12, 2016 by MaxwellsDemon

[wumpus]

16 hours ago, 0111narwhalz said:

Thank you. This is exactly what I was trying to convey with the points in the OP.

By "information" I meant data, in the form of a beam of light or something. Some FTL devices allow you to beam lasers through, others let whole ships through too, while still others disallow energy-only information (such as lasers) but let ships through. This is generally a requirement imposed purely by the author's desire to tell a specific kind of story. I realize it's unlikely that the ship-but-no-radios FTL has any deep-seated merit, but considering the territory, it's all good.

This is the problem of sci-fi, once you change the science you change the tech.  And you have to account for the tech.  If you don't have an ansible (a magic box that sends information instantly - oh-oh, major relativity violation that goes beyond casaulity) or other sub-space network you could presumably send a probe with arbitrary amounts of data ("the bandwidth of a FedEx truck full of SDHC memory cards is relatively infinite").  Although I think the Alcubierre solutions require an impossibly huge "bubble", and presumably ship to go with it so it is unlikely that anyone would build a communication drone.

This tends to lead to the same issues about how cellphones obsolete a ton of old TV plots: if the various star systems can't communicate, there has to be a reason nobody bothered to just tell them.  Best solution if you need that: the absolute minimum for a warp drive is *huge* (no invading armadas being swallowed by a small dog here).  The *really* nasty issue: even if you can prevent planets from *instant* communications, how do you prevent simply sending a message back in time?  One possible solution: entering the Alcubierre "bubble" frees you from a specific timestream (change history and you go to a different planet: the original is still there).  To maintain coherency (and presumably enforced by laws, possibly by unknown "cops") all planets emit radio waves with frequent "station identification" this lets the helmsmen find the right planet that is uncorrupted by acasual "facts".  I suspect this *still* has a ton of issues (the information keeps corrupting planets and they keep losing coherence with every landing) but there should still be an illusion of causality.