Idea for FTL

[VarrusTheEthical]

Good Evening SSD.Net.

Long time lurker, first time poster.

Anyway, for the last year now, I've been working on a relatively hard military sci-fi novel and I am now finishing up the last bit of editing before trying to get the novel published. What I wanted to do was post how my FTL drive works to see what people think, I may post more details if people are interested.

FTL is creatively called FTL in my setting. It's broadly similar to a warp drive in that you can flying at FTL speeds from anywhere to anywhere, but with many important limits.

The first major limitation is that it is relatively slow, with a speed of 100 times the speed of light, about two weeks to get to Alpha Centauri from Sol. Just as important is that there is no FTL "throttling", if you're going FTL you're going 100c. No faster, no slower.

Second is that massive objects like stars create zones of space where the FTL drives do not work, and the radius of that zone is directly proportional to the mass of the object. For example, Sun would have and FTL exclusion zone of 7.5 billion kilometers or 50 AU in radius, basically the outer edge of the Kuiper belt. A star that's double the mass of the sun, like Sirius, would have an FTL exclusion zone double the radius of Sol.

Now FTL drives themselves are made of an form of (made up) exotic matter that can only be made by directly converting energy to exotic matter. Naturally this requires massive energy collection capabilities to allow for production of FTL drives.

My setting's FTL has other properties as well. A ship traveling at FTL is completely blind. . All that you can see while inside and FTL field is a white light at the front, gradually moving down the visible light spectrum until you see complete blackness behind you. You can't turn FTL, if you want to change direction, you have to drop out into normal space first. FTL ships cannot be detected or tracked while in FTL, but do create very detectable flashes in the EM spectrum when leaving FTL. Entering FTL is less detectable but still noticeable. A ship leaving FTL for whatever reason has zero velocity leaving FTL relative to the nearest massive object, usually a star. If you fly into an FTL exclusion zone at FTL, you just fall out of FTL. If your ship loses power, you drop out of FTL. Also, if your FTL drive needs to make up at least one-percent of your ship's total mass, otherwise you don't go anywhere. Ships traveling at FTL cannot be directly interacted with by objects that don't have enough mass to create an FTL exclusion zone, so dust and small rocks are not a threat. Large asteroids and rogue planets can still pull you out of FTL if you get close enough.

I hope people find this interesting and I'm open to any ideas that others may have.

[Batman]

Sounds a lot like Wars EU hyperdrive to me, except it's massively slower. And if you're going for hard Sci-Fi, I'd call that-misty, at best. The moment you have FTL, you threw hardSciFi out the window.
So why, exactly, does the influence objects have on ships underway on your stardrive depend on the aforementioned object's mass?

[VarrusTheEthical]

Sounds a lot like Wars EU hyperdrive to me, except it's massively slower. And if you're going for hard Sci-Fi, I'd call that-misty, at best. The moment you have FTL, you threw hardSciFi out the window.
So why, exactly, does the influence objects have on ships underway on your stardrive depend on the aforementioned object's mass?

When I say relatively hard sci fi, I was aiming for the same ball park as Mote in God's Eye, at least where starships are concerned. As for why massive objects prevent FTL operation? Because among other things, I wanted travel within systems to be restricted to using standard reaction drives. The best way I can explain the FTL exclusion zone is that massive opjects create a kind of reverse Alderson point, only on a colossal scale. If you're inside it and charge up you FTL drive, you just burning energy without anything happening. When you outside and you charge up your FTL drive, your star ship starts moving at 100c in the direction it's pointed.

[Stofsk]

It's ok as ideas go. So long as you work this out and keep things consistent, you should be fine. Some of it reminds me of Traveller, which had the 'can't/shouldn't jump within 100 diametres of a gravity well' quirk, because Bad Things May Happen.

[Number Theoretic]

I agree on the "it's ok as long as you keep it consistent" view. I found a good example of a consistent "handwavium technology" on Atomic Rockets: the Langston field, which offers protection against lasers and missiles, but needs time to radiate the absorbed energy of the impacting weapons away. Which implies, that ships can be destroyed by oversaturating their Langston fields.

Concerning your drive, i have a question: How much time does one of your FTL drives need to charge, before you can enter FTL? Because, depending on that, it might be possible to steer a ship with any effective velocity below 100c: just turn the drive on and off, with any frequency desired. The higher the frequency, the closer to 100c you are and it allows your astrogation computers to make course adjustments while the ship is in the non-FTL phase.

[StarSword]

Question: Are FTL communications possible (ansibles, HoloNet, subspace comm, whatever)?

[Starglider]

100c is a suspiciously round number for a physical constant.

[VarrusTheEthical]

I agree on the "it's ok as long as you keep it consistent" view. I found a good example of a consistent "handwavium technology" on Atomic Rockets: the Langston field, which offers protection against lasers and missiles, but needs time to radiate the absorbed energy of the impacting weapons away. Which implies, that ships can be destroyed by oversaturating their Langston fields.

Concerning your drive, i have a question: How much time does one of your FTL drives need to charge, before you can enter FTL? Because, depending on that, it might be possible to steer a ship with any effective velocity below 100c: just turn the drive on and off, with any frequency desired. The higher the frequency, the closer to 100c you are and it allows your astrogation computers to make course adjustments while the ship is in the non-FTL phase.

A good idea, sounds like the stutter warp drive from Traveller 2300. Ships will drop out of FTL to make course corrections for long jumps, but but you're not going to be able to rapidly enter a leave FTL because the cooldown between jumps can take between several seconds to several minutes depending on the size of the ship. Say thirty seconds for a 50,000 ton Destroyer and then minutes for a 10,000,000 ton battleship.

Question: Are FTL communications possible (ansibles, HoloNet, subspace comm, whatever)?

There's no ansible or subspace radio in my setting. Only starships and unmanned FTL courier drones, which are basically an FTL drive with fuel tank and a computer, can carry messages at FTL speeds. There is no realtime communication over interstellar, or even interplanetary, distances. With the exception of starships themselves, c is still the speed limit.

100c is a suspiciously round number for a physical constant.

Makes the math easier.

[Batman]

Unsurprisingly. It also makes for really long travel times even on a very limited interstellar scale (at 100c, even Proxima Centauri-the closest real world star to our solar system-is several month's travel away).
And I think what Starglider was getting at was..., well, what he said, that its a suspiciously round number for a law of physics limit, as opposed to an engineering one.

[Losonti Tokash]

That's actually just a little over two weeks at 100c. Did you forget a zero? Plus it's pretty obvious when he says it makes the math easier, he's talking about for himself, not for his in-universe engineers.

At any rate, sounds very much like Mass Effect's, with the main difference of being useless in-system. Do they just push themselves around with reaction drives once they're actually there? Is it something you can just boot up once you get to the edge or does it take a lot to get ready?

[VarrusTheEthical]

That's actually just a little over two weeks at 100c. Did you forget a zero? Plus it's pretty obvious when he says it makes the math easier, he's talking about for himself, not for his in-universe engineers.

At any rate, sounds very much like Mass Effect's, with the main difference of being useless in-system. Do they just push themselves around with reaction drives once they're actually there? Is it something you can just boot up once you get to the edge or does it take a lot to get ready?

Yes, the 100c is to make the math easier for me. FTL is magic as far as modern sciences is concerned, why not make it easy magic?


Once in system, ships use extremely potent Deuterum/He3 fusion drives to get around. Typical warships have a detla V of 20,000kps, so they can get around following Brachistochrone trajectories. Also, once you're outside the radius of the FTL exclusion zone, you can just switch on the drive and wait for it to charge up. As mentioned earlier, bigger ships require a longer charging time.

[Batman]

I didn't forget a zero, I just said Proxima Centauri when I was actually thinking Vega.
And of course he's talking about making the math easier for himself. My point was that the speed (apparently the only speed) being 100c makes a lot more sense as an engineering issue rather than a laws of physics one. 9.81 mps^2 for a g, whatever c in a vacuum is (something not quite 300,000 kps), and so on. The only times our units fit neatly with what happens in the actual universe is when we designed them to.

[VarrusTheEthical]

btw, I don't think it's really any easier to work with because of the units conversions between years and days anyway. At 100 times the speed of light, how long does it take to cross one light year? Well, 1/100 of a year... but how many days is that? 365 / 100 = 3.65. Great, but it's not a pretty number anymore.

What if it's eight light years? 3.65 * 8 = .... well, about 29, but I know that more thanks to the fact that I'm a hyperintellect entity with an integrated arithmetic co-processor, rather than because the 100 kept the numbers simple...

True, there's still room for mathematical messiness, but 100c works well for me because I wanted a relatively small setting. 100c opens up a lot relatively close star-systems, but the Galaxy as a whole will still be out of reach. It also means that interstellar governments will be relatively small, only able to control a handful of systems, if at all.

[Ariphaos]

Expressing the limits of FTL travel as a multiple of c makes no logical sense. Under which frame of reference? You can't lock it to Sol's - that means the majority of the Universe gets ridiculous values for it. You can lock it to an external frame, and that opens up all of the possibilities that an external frame imposes - specifically that your limit is bunk. Your other limits strike as being arbitrary, as well. One percent of the ship's mass. Exclusion zone exactly 50 AU per 1 solar mass. You basically eliminate all of the tactical features of FTL travel by rule of fiat when this has been part and parcel of every other mode of travel. Your exclusion zone does not actually grant any appreciable defense against creative attacks - sunshine and happiness wins again, as usual.

Your system is a giant jumble of "you can't"s, all to get around one other "you can't". You're not growing your Universe appreciably compared to the guy who wrote his setting around a light sail network. What story is this FTL system going to permit you that requires it and these arbitrary values?

[VarrusTheEthical]

FTL in fiction is always going to be dictated by arbitrary limits and author fiat. Or, a giant jumble of "you can'ts" as you put it. Unless your FTL is just a plot drive like in BSG or Star Trek.

As for what kind of story do I need these limit's for? One where I can have the characters go from on star system to another without having to deal with decades of travel or the inconvenient affects of time-dilation. I also want interstellar government, which is frankly, not possible in a non-FTL setting. I also want ships with powerful reaction drives, which you don't need if they can just jump straight to low orbit. And I have thought about the tactical and strategic implications of such a system, it's part of what drives the plot.

I would highly recommend vising Atomic Rockets FTL section. That's pretty much the guidebook I used when designing my setting's FTL. http://www.projectrho.com/rocket/fasterlight.php

[VarrusTheEthical]

Why do you want interstellar government?

It's just something I wanted to incorporate. The issues involved in having a government control more than one star system creates great potential for conflict.

[Feil]

Shouldn't your exclusion zone go as square root of mass, not the mass?

[Feil]

Addendum: what other people are getting at is that fixed values aren't necessary if the characters and readers are unaware of them - and, in fact, they'll just get in your way when you're plotting scenes. And if the characters and readers /are/ aware of them, then they need to make some level of sense, which means that you're going to have to build an entire, completely bogus field of physics around them to support them that doesn't break any important physical laws that you don't mean to break. Which is really really hard.

In real life, the people that work big, complicated, high-tech machines neither know nor care about the physics behind them. The person you want safeguarding your nuclear submarine's reactor is a nuclear reactor engineer, not a nuclear physicist. Knowledge of the process is irrelevant. All anybody needs to know is how to fix it if it breaks, when the engines cannae take the strain, and how long you can keep going when she's givin' it all she's got, captain.

Fixed values can be useful as benchmarks to help you build scenes and keep your universe consistent. But keep your characters and readers ignorant of them, and don't feel beholden to them. You don't, for instance, have any reason to calculate the masses of your ships and FTL machines. All you, your characters, and your readers ever need to know is that a big ship has a big FTL machine, and a little ship can get by with a smaller one.

[VarrusTheEthical]

Addendum: what other people are getting at is that fixed values aren't necessary if the characters and readers are unaware of them - and, in fact, they'll just get in your way when you're plotting scenes. And if the characters and readers /are/ aware of them, then they need to make some level of sense, which means that you're going to have to build an entire, completely bogus field of physics around them to support them that doesn't break any important physical laws that you don't mean to break. Which is really really hard.

In real life, the people that work big, complicated, high-tech machines neither know nor care about the physics behind them. The person you want safeguarding your nuclear submarine's reactor is a nuclear reactor engineer, not a nuclear physicist. Knowledge of the process is irrelevant. All anybody needs to know is how to fix it if it breaks, when the engines cannae take the strain, and how long you can keep going when she's givin' it all she's got, captain.

Fixed values can be useful as benchmarks to help you build scenes and keep your universe consistent. But keep your characters and readers ignorant of them, and don't feel beholden to them. You don't, for instance, have any reason to calculate the masses of your ships and FTL machines. All you, your characters, and your readers ever need to know is that a big ship has a big FTL machine, and a little ship can get by with a smaller one.

Oh get don't me wrong, I'm not trying to invent a field FTL physics or anything. What I listed with the effects of the FTL drive as any character would see them. I don't really explain the causes beyond "switch the extremely expensive piece of machinery to ON". But I need FTL to behave consistently because that behavior is going to dictate the kind of universe I can logically build.

Also, I don't explain to the reader all the details that I have listed, everything is largely "under the hood". But characters traveling on a starship are still going to spend weeks or months totally cutoff from the rest of the universe, since they are traveling faster than any message can reach them. As such, I have to consider how that would affect them.

One effect of the FTL exclusion zone is that ships need to burn fuel (propellant) to move from the edge of the exclusion zone to the interior. Now since FTL also burns fuel, that means than you're not going to have a full fuel load upon entering a system. For a merchant starships, this means that you will likely have to stop at a station at the edge of the exclusion zone to refuel, or hand off your cargo to intra-system freighters.

Now in terms of warfare, it would dictate both the composition any fleet and its likely strategic objectives. A typical fleet would likely consist of not only you typical combatants like cruisers and battleships, but also logistics vessels like tankers and mining vessels. Say I jump into a hostile system after burning a third of my fuel? I would likely want to first secure a sources of fuel for my thirsty starships, particularly Helium 3. If the objective system has an ice-giant similar to Neptune, then that would likely be the first thing I would want to secure. Not only would the fuel likely be needed for me to accomplish my objectives, but it would help assure that I had enough fuel to retreat to a friendly system should things turn sour.

So to reiterate, I'm just focusing on the effect side of the FTL drive rather than the magic that makes it work. I want a small universe, so the FTL is slow. I want long duration, high acceleration voyages in normal space, so I have the FTL exclusion zones. I want FTL to be expensive, so the drives need to be made of out off exotic stuff that has to be synthesized via energy-to-mass conversions, essentially the unobtanum of my setting. In other words, I made up the FTL working backwards, starting from the kind of universe I wanted.

[Number Theoretic]

And as far as i can tell, it worked for you. Because FTL is magic, you can pretty much design anything you want. Just don't throw too many constraining effects at once at the reader, because it provokes them to ask questions. But i can imagine, that this effect can be mitigated if you merely hint at possible explanations and if you keep the whole thing consistent. If i would design an FTL drive, i would also concentrate on the effects.

One more question: How does navigation work, while your fleet is in interstellar space? The constraint, that you cannot see anything of the space around you, while in FTL and the other constraint, that you also cannot adjust your course and speed leaves just 2 possibilites:

• Your ships need extreme steering accuracy in order to "aim" at your destination system.
• You "stutter", just with a low frequency. For example 1 day of FTL cruise followed by 20 minutes of position determination, course adjustment and reactivation of the FTL drive.

edit: I assume, you go with the second option but i'm not sure though

[StarSword]

One more question: How does navigation work, while your fleet is in interstellar space? The constraint, that you cannot see anything of the space around you, while in FTL and the other constraint, that you also cannot adjust your course and speed leaves just 2 possibilites:

• Your ships need extreme steering accuracy in order to "aim" at your destination system.
• You "stutter", just with a low frequency. For example 1 day of FTL cruise followed by 20 minutes of position determination, course adjustment and reactivation of the FTL drive.

edit: I assume, you go with the second option but i'm not sure though

I think he said earlier that they drop out of hyperspace* periodically for navigational checks, so yes, he goes with the second option.

* Just using the terms I'm used to.

[Number Theoretic]

I think he said earlier that they drop out of hyperspace* periodically for navigational checks, so yes, he goes with the second option.

* Just using the terms I'm used to.

Ok, then i wasn't paying attention, sorry.

[VarrusTheEthical]

And as far as i can tell, it worked for you. Because FTL is magic, you can pretty much design anything you want. Just don't throw too many constraining effects at once at the reader, because it provokes them to ask questions. But i can imagine, that this effect can be mitigated if you merely hint at possible explanations and if you keep the whole thing consistent. If i would design an FTL drive, i would also concentrate on the effects.

One more question: How does navigation work, while your fleet is in interstellar space? The constraint, that you cannot see anything of the space around you, while in FTL and the other constraint, that you also cannot adjust your course and speed leaves just 2 possibilites:

• Your ships need extreme steering accuracy in order to "aim" at your destination system.
• You "stutter", just with a low frequency. For example 1 day of FTL cruise followed by 20 minutes of position determination, course adjustment and reactivation of the FTL drive.

edit: I assume, you go with the second option but i'm not sure though

I will make the point that fleets need to "stutter" more often than lone ships. A lone ship just needs to be accurate enough to hit the target star system. Fleets on the other hand have to worry about maintaining formation. This is particularly important if you're attacking since you obviously want to concentrate your fire power.

[Batman]

With a peak speed of 100c, I don't think it's much of a problem. I mean a trip to Proxima Centauri is going to take two and a half weeks, leave alone distances actually worth mentioning. Coming out of stardrive every couple days or maybe once a week to get your bearings should work fine.

[Ariphaos]

FTL in fiction is always going to be dictated by arbitrary limits and author fiat. Or, a giant jumble of "you can'ts" as you put it. Unless your FTL is just a plot drive like in BSG or Star Trek.

Hardly.

There are plenty of ways to cheat the system that leads to an overall reduction in headache rather than the increase you are inviting. There is, for example, a solution to FTL, Causality, and Relativity where you can pick all three: Wormholes with endpoints that are fixed with respect to each other. Time travel cannot be instigated because relativistic travel deforms the face of the wormhole. There are still other problems with it (potential energy differences, propagation of gravity, etc.) but you solve the worst of the problems. Though, technically, either causality or relativity is being violated. It just isn't necessarily possible to figure out which, which can be a fun thing to impose on a setting.

As for what kind of story do I need these limit's for? One where I can have the characters go from on star system to another without having to deal with decades of travel or the inconvenient affects of time-dilation.

Why take it as a given that either is a problem in a science fiction setting? Has every other aspect of humanity remained stagnant save for space travel?

I also want interstellar government, which is frankly, not possible in a non-FTL setting.

A loose federation is perfectly possible in a non-FTL setting - necessary, even, in order to allow light-sail exchanges and regulate the use of sunshine and happiness on interstellar scales.

Your version of FTL does not change this. In order to have an interstellar government where one star system rules another star system that actually has some slight control over its host star (or stars), it must be necessary for attacking ships to be able to somehow deal with that. Nothing short of Star Wars and WH40k in established fiction is capable of such a feat. But being able to throw around that sort of power would make such governments just as possible in a non-FTL setting.

I also want ships with powerful reaction drives, which you don't need if they can just jump straight to low orbit. And I have thought about the tactical and strategic implications of such a system, it's part of what drives the plot.

Put any invasion fleet up against the power of solar statites capable of directing a fraction of a percent of the energy of the system's host star. Until you have done so, the answer is no, you have not.

I would highly recommend vising Atomic Rockets FTL section. That's pretty much the guidebook I used when designing my setting's FTL. http://www.projectrho.com/rocket/fasterlight.php

I've written my own article on FTL travel too. You will find that many of the discussion regarding most science fiction topics here on SD.net far surpasses anything on Atomic Rocket. Here, the author is just another member. It grants them no special privileges. Though yes, it is annoying to see people who think we don't know of the place. It is not the final word on any subject.

As I referenced in my first post, and in my two-year old blog post, there, using a multiple of c as an FTL speed is nonsensical. Especially since you state you want high-speed reaction drives. It's really quite jarring, and as a general rule, rather unnecessary and best avoided. It's often better to make a starmap - "It takes this long to get from star A to star B and slightly longer back."

One of Project Rho's greatest flaws in its FTL section is it does not go over the implications of imposing a special frame as you have.

Relativity mandates that there is no special frame. However, observations so far are constrained to the Universe, and we lack any sort of FTL observations. This means that you can in fact have in-Universe relativity, causality, and FTL travel, if you posit a special frame that is outside of the Universe. You are simply breaking Relativity on scales outside the scope of our current ability to empirically test.

But in that case, your FTL drive is not going to have a constant speed. It's going to depend on how fast the local star is moving with respect to the true special frame. As a general rule, this will be fairly constant from the perspective of any star in a galaxy, but there might be a slight advantage in moving one direction over another (e.g. the Milky Way is moving at ~600 km/sec with respect to the local interstellar medium. Ships moving at relativistic speeds, however, as yours do, are going to see a huge difference.