How powerful could a hard sci-fi civilization be?

[Feil]

Is there a particular reason why the Rebellion can't smuggle in a handful of experts and start mass-producing FTL communication on one of ten million friendly planets with tremendous established resources and infrastructure? As I recall, the Rebels were operating a reasonably successful insurgency out of some ancient ruins on a deserted moon, against an Empire that wasn't trying to fight a galaxy-spanning civilization at the time.

[RogueIce]

Is there a particular reason why the Rebellion can't smuggle in a handful of experts and start mass-producing FTL communication on one of ten million friendly planets with tremendous established resources and infrastructure? As I recall, the Rebels were operating a reasonably successful insurgency out of some ancient ruins on a deserted moon, against an Empire that wasn't trying to fight a galaxy-spanning civilization at the time.

Because then it's no longer "random scifi franchise with FTL" going against "made up and wanked out 'hard sci-fi' galaxy" anymore? Kinda like how you don't routinely see the Rebel Alliance fighting alongside the Federation in SW vs ST?

[Jub]

If the FTL civ exists in the same universe as the STL civ, then what's stopping them from discovering FTL travel? If they're in different universes why does FTL suddenly work when an outside civilization introduces it to a universe where it was impossible before?

[sirocco]

Probably because in hard SF setting, understanding then building a FTL cannot be done overnight. For all we know, the hard SF scientists did not discover FTL. They did discover a non STL civilization and inferred that they were using FTL. That's not enough.

[RogueIce]

If the FTL civ exists in the same universe as the STL civ, then what's stopping them from discovering FTL travel?

What was stopping them from inventing it the previous 10 million years or however long they were expanding through the cosmos and building their super death coil guns and shit? And why would this suddenly change as soon as they happen to meet up with a civilization that has FTL?

By this logic I could go into the SWvsST forum and start saying the Federation will reverse engineer Death Stars, because obviously they work since the Empire has them. And every other piece of tech either side has until neither force is even remotely recognizable and the whole 'debate' has long since lost any meaning.

[Jub]

If the FTL civ exists in the same universe as the STL civ, then what's stopping them from discovering FTL travel?

What was stopping them from inventing it the previous 10 million years or however long they were expanding through the cosmos and building their super death coil guns and shit? And why would this suddenly change as soon as they happen to meet up with a civilization that has FTL?

By this logic I could go into the SWvsST forum and start saying the Federation will reverse engineer Death Stars, because obviously they work since the Empire has them. And every other piece of tech either side has until neither force is even remotely recognizable and the whole 'debate' has long since lost any meaning.

The only thing that should be stopping them is the OP's poorly thought out scenario. Of course by the wording of the OP you could have FTL as long as science thinks that in might someday be possible...

[RogueIce]

The only thing that should be stopping them is the OP's poorly thought out scenario. Of course by the wording of the OP you could have FTL as long as science thinks that in might someday be possible...

That's like saying the only thing stopping the Federation from mass use of warp strafing or the Empire not having millions of ISDs is poor writing...oh wait.

[Jub]

The only thing that should be stopping them is the OP's poorly thought out scenario. Of course by the wording of the OP you could have FTL as long as science thinks that in might someday be possible...

That's like saying the only thing stopping the Federation from mass use of warp strafing or the Empire not having millions of ISDs is poor writing...oh wait.

Well, then we already know exactly how this turns out. The STl force can crush certain soft sci-fi and not rest. Where you draw the line between what it can and can't beat is where it gets interesting and I've already said that I think it's above Trek but below Star Wars.

[RogueIce]

The only thing that should be stopping them is the OP's poorly thought out scenario. Of course by the wording of the OP you could have FTL as long as science thinks that in might someday be possible...

That's like saying the only thing stopping the Federation from mass use of warp strafing or the Empire not having millions of ISDs is poor writing...oh wait.

Well, then we already know exactly how this turns out. The STl force can crush certain soft sci-fi and not rest. Where you draw the line between what it can and can't beat is where it gets interesting and I've already said that I think it's above Trek but below Star Wars.

Yeah probably. Trek is pretty young as far as interstellar activites go so it's not a surprise. Wars is more mature but depending on how far back the history goes may still be pretty young by the "10 million years of expansion" STL galaxy standard. Though they certainly have lots of toys to show for it...

But yeah, how do you define it? I mean how do we even know how much of what's been put into this thread really is practical and possible. And then there's what Connor said about the politics and all: let's face it, the STL government spread across the galaxy is going to resemble semi- to more-or-less de facto independent nation states than anything cohesive like an FTL galactic power. So how do you know half of them won't, as an example, throw in with the FTL side in exchange for all those technological goodies they'd have to offer?

Nevermind the obvious advantage you get when you get to pretty much define your side to be the maximum of it's abilites and then pit them against an established setting that...well, likely wasn't created with the idea to maximize their capabilities in the first place. If you were, for example, to define the "FTL side" as, I don't know, soft sci-fi setting that's expanded as much as the STL side but also has the goodies like FTL, artifical gravity, hard shields, transporters and other bits of soft sci-fi goodness...well things are definately going to be different, aren't they?

[lPeregrine]

By this logic I could go into the SWvsST forum and start saying the Federation will reverse engineer Death Stars, because obviously they work since the Empire has them. And every other piece of tech either side has until neither force is even remotely recognizable and the whole 'debate' has long since lost any meaning.

Not really. The Federation couldn't build a death star (at least fast enough to matter) because they don't have the industrial base to compete with the Empire. You could tell them exactly how to build one and it wouldn't make a difference, they wouldn't even be capable of building the physical shell of it on any reasonable time scale.

The HSF civilization, on the other hand, does have the kind of industrial base needed to compete. Since FTL works in the HSF universe the best explanation is that the HSF civilization simply, by act of plot, wasn't able to discover the required principles to build a FTL engine. If they gain that knowledge there's nothing stopping them from putting it into mass production, and when you have millions or billions of settled systems it's inevitable that someone is going to survive long enough to build a FTL fleet.

Now, this is still arguably a concession of defeat since it's no longer hard scifi, but it's a lot more realistic to think that the HSF civilization is going to be able to produce FTL than it is to suggest that the Federation can build a war-winning star destroyer fleet.

Nevermind the obvious advantage you get when you get to pretty much define your side to be the maximum of it's abilites and then pit them against an established setting that...well, likely wasn't created with the idea to maximize their capabilities in the first place. If you were, for example, to define the "FTL side" as, I don't know, soft sci-fi setting that's expanded as much as the STL side but also has the goodies like FTL, artifical gravity, hard shields, transporters and other bits of soft sci-fi goodness...well things are definately going to be different, aren't they?

Except that's the entire point of the thread. It's not "hard vs. soft at full power", since, as you said, that's going to be a boring and one-sided match. The question here is which soft scifi civilizations could the hard scifi civilization defeat. IOW, at what point does their sheer size and development become enough of an advantage to make up for the lack of FTL and similar magic.

[bilateralrope]

What IS the theoretical limit on those? We're talking about a fully-developed hard scifi civilization here, so we can assume that technology will allow detection of planets at the theoretical limit.

I don't know the answer. That's why I asked.

Aiming the 20AU gun is probably going to be harder though.

Some form of guidance on the projectile does make things easier, unless the target planet has enough warning to try and fool its sensors.

Exactly. Why throw a lump of rock when you can throw a lump of rock with engines and a load of guided submunitions that will be deployed shortly before impact to ensure you also get any ships/stations/etc in the system?

A guided weapon has three problems:
1 - The guidance system needs to survive the launch acceleration.
2 - Any mass used to change course is mass not used for impact. Meaning you have very limited delta-v, so corrections need to be made well in advance. Forget about hitting anything that isn't in a stable orbit.
3 - If someone duplicates the signature of whatever it's trying to hit, or masks the signature of the target, then the guidance becomes useless. For example, lets say they program it to look for radio signals to identify inhabited targets, because everyone the hard civilization knows uses them. Problem is, the Federation doesn't. But they know how to make them, so if they know about it looking for radio signals, they just create powerful radio beacons elsewhere in system. Now even the projectiles that were correctly aimed will miss.

If they could somehow accelerate it at 1,000,000g, then it would only be 3 gigameters long. Or ten light-seconds. Which is still massive. And it would heat up like all hell breaking loose.

The more it heats up, the more likely it is to melt something important after the first shot. Making the second shot less likely.

Which brings us to politics: How many of these guns are going to be politically viable to build ?
Limited number of shots. Their sheer size makes aiming them a problem.

Also, you don't want to put habitats on these things. I wouldn't want to be near one of these things, god forbid living on one. If that projectile does not align with the ring you are on, dead instantly. If the radiators fail you burn up. Heck, arrange things the wrong way in your room when it fires, and you could be impaled by you cutlery set as the electromagnets power on.

And with the amount of effort put into this gun, you can build massive laser arrays that can keep you safe from any invader, or even other relativistic weapons, and detection systems to actually see such weapons being fired.

What's the range of Federation beam weaponry against stationary targets ?
Because it sounds like it would be very vulnerable to a fed ship dropping out of warp at max range, firing phasers at it a few times, then warping off before the defenders can react.
Or if that doesn't work, build a weapon that consists of an antimatter warhead and a warp drive. Come out of warp on top of the gun, then detonate it. If the defenders do stop the detonation sequence, that still leaves them with a large quantity of antimatter on a collision course.

If they have a lot of RKV guns, then then the ones not pointed at Federation space are a lower priority.

[sirocco]

2 - Any mass used to change course is mass not used for impact. Meaning you have very limited delta-v, so corrections need to be made well in advance. Forget about hitting anything that isn't in a stable orbit.

So far, most of the FTL protagonists (Trek, SW, BSG, B5, SG) have most of their population on planets, which are on stable orbit. Some of them have significant space stations and fleets stationed in close orbit rather than deep space.

But well what prevents a STL civilization with enough resources from continuously bombarding their homeworlds? In most case, at least 70 to 80% of the enemy ranks will be swept away, as well as most of the leaders.



And there is another tactic that would be very effective against FTL civilizations: biological warfare.

And because they travel so fast within their galaxy, the spread and severity of the infection(s) would be tremendous and overwhelming. That's one of the factors that enabled the Black Death to wipe out most of Eurasia population during the Middle Age.

[Stark]

Aside from the amusing reinvention of Dune, there are some laughs here.

Say the HARDSCIFI SUPERIOR SUPER EMPIRE attacks a SW planet with rocks.

It takes, say, five thousand years for the projectiles to reach their targets, and they're detected and splat on a shield/intercepted/diverted/generally laughed at as space weather.

It then takes maybe forty five minutes for the counterattack to arrive. Uh oh! Talking about scale of a 'realistic' 'hardscifi' setting is one thing, but the need to translate this into laughable 'POWER LEVELS' is just sad. But I guess giving one side huge scale advantages makes people feel... smart? Or something? I'm glad people have worked out you don't need FTL to have interesting stories, but you equally don't need amazingly sad wank to have good stories.

[Sea Skimmer]

I wouldn't assume that. The Acclamators had a 250,000 LY range, but the Venators had only 60,000 LY. And the various Separatists ships had (IIRC) 30,000, 40,000 and 150,000 LY.

Venator had a very volume intensive hanger bay, none of the separatist ships are all that big volume wise; one assumes that took away space for fuel tanks. Doesn’t really matter, the Empire is going to be building new ships for this and an Acclamator stripped of its hanger and troop space could hold even more fuel tanks. In fact you could plainly triple the fuel tank capacity volume wise, though the increased mass might make the ship a damn lot slower.

On a side note, since the Death Star showed minimal fuel tankage, and most other ICS ships show none, it seems logical ton conclude that hypermatter reactors actually hold a large internal fuel supply that is not instantly consumed. This would make them a sort of hybrid in-between the way fuel supply works for a nuclear reactor vs a oil burning boilers.

And those ranges reflect full fuel supplies IIRC, so we're also talking 'max range before running empty'.

That would be the normal meaning of range for warships yes, as opposed to combat radius as typically given to describe the reach of combat aircraft. But since we only have range and peak fuel consumption specs for certain ships its impossible to come up with an actual radius of action including combat time.

Which also means that hyperdrive range can be further limited by other performance requirements (acceleration needs, offensive and defensive requirements, etc.) EG an Venator that 20K LY has 40K LY of range left, but if he has to use the max engine/shield/guns option for any lenght of time (~3 hours is what I remember being Curtis' endurance for max-power ISDs) that could be cut down dramatically (so much the ship may not even be able to make it home.) In the SW galaxy this isn't an issue, but in other scenarios its up for debate.

Doesn’t seem like a pressing problem to send out tankers. Hell, the entire fleet might be nothing but armed tankers considering the complete inability to the HSF side to force a space to space battle.

I think you're confusing what the AOTC:ICS said was involved in creating the gravitic components of repulsors with fuel. Though I'd guess they probably use 'natural' fuel sources (EG stars, or maybe black holes) to make hypermatter fuel in the same way you might use that to create antimatter.
Some vessels have run on black holes (World Devastators) though.

Yeah you’re right, still, the fact that refineries encompassing black holes can be used to make hover cars for people on backwater sand planets already gives an idea of how trivial energy production must be. Certainly we never have any indication that fueling starships is a problem at all. Whatever the source of hypermatter is it must be economical and prolific in the galaxy.

Alot of this depends entirely on the distances between the two galaxies, the political factors (how much is the SW galaxy willing to devote to achieving victory?) and the manner they go about prosecuting the war. As I said already, I kinda doubt they're just going to do nothing but build ISDs and hurl them at the enemy simply because that's all they know. If they can't reach the target with existing ship designs (or if those designs prove incapable of beating the enemy) then they'll just devise some other means of achieving it. It comes down to how much effort they need to invest to reach the galaxy, not whether or not they can do so.

The exact details of how they’d win don’t seem that important. If they are going to win, it would be more logical to debate someone who is a closer match to the HSF power, but nobody seems interested in that. Instead we get constant talk about relativistic weapons as if somehow this is an ace in the hole, when in fact not only does the Wars side have multiple means of detecting and counteracting them, its blatant that such weapons not only exist in Wars, virtually every high performance starship has the acceleration to potentially act as a relativistic weapon and indeed fractional light speed performance has been stated for mere starfighters in action. Kind of obvious that this is not the utter doom of wars.

Hell with their FTL comms ability, their automation capabilities, etc. It's quite possible they could simply just launch a bunch of expendable FTL bombs at the opposing galaxy.

World Devastators traveling along building energy plants and sun crusher drones would seem rather effective and involving little economic impact on the Wars side at all. But lame for a debate like this considering fair reason exists to consider the sun crusher lost technology.

[bilateralrope]

2 - Any mass used to change course is mass not used for impact. Meaning you have very limited delta-v, so corrections need to be made well in advance. Forget about hitting anything that isn't in a stable orbit.

So far, most of the FTL protagonists (Trek, SW, BSG, B5, SG) have most of their population on planets, which are on stable orbit. Some of them have significant space stations and fleets stationed in close orbit rather than deep space.

I was responding to lPeregrine's suggestion that the guided RKV be used to take out "any ships/stations/etc in the system".

But well what prevents a STL civilization with enough resources from continuously bombarding their homeworlds? In most case, at least 70 to 80% of the enemy ranks will be swept away, as well as most of the leaders.

If the FTL civilization is fighting the war before the RKVs launch, then the bombardment will take too long to arrive to affect the FTL civs plans, except that the FTL civilization may be less willing to negotiate surrender after the RKVs are on route. Also, hundreds of years is plenty of time to move their leadership to somewhere else.

If the FTL civilization doesn't know that the war has started, then the hard civilization has just started the war with acts of genocide that will take centuries or more to take place. Giving the FTL civ plenty of time to stumble across them, note the RKV gun and ask if it has ever been fired.

And there is another tactic that would be very effective against FTL civilizations: biological warfare.

And because they travel so fast within their galaxy, the spread and severity of the infection(s) would be tremendous and overwhelming. That's one of the factors that enabled the Black Death to wipe out most of Eurasia population during the Middle Age.

For biological warfare to work they would need to:
- Create a pathogen that works on a species they don't know much about.
- Against some settings they would have the additional hurdle of requiring it to jump species.
- Ensure it remains undetected by the soft civs medical tech long enough to spread.
- Deliver it to the soft civ somehow.

[RogueIce]

Not really. The Federation couldn't build a death star (at least fast enough to matter) because they don't have the industrial base to compete with the Empire. You could tell them exactly how to build one and it wouldn't make a difference, they wouldn't even be capable of building the physical shell of it on any reasonable time scale.

The HSF civilization, on the other hand, does have the kind of industrial base needed to compete. Since FTL works in the HSF universe the best explanation is that the HSF civilization simply, by act of plot, wasn't able to discover the required principles to build a FTL engine. If they gain that knowledge there's nothing stopping them from putting it into mass production, and when you have millions or billions of settled systems it's inevitable that someone is going to survive long enough to build a FTL fleet.

Now, this is still arguably a concession of defeat since it's no longer hard scifi, but it's a lot more realistic to think that the HSF civilization is going to be able to produce FTL than it is to suggest that the Federation can build a war-winning star destroyer fleet.

Well, I have my doubts on this though I'd admit a lot depends on what kind of scale we give to the HSF civilization (one galaxy, several galaxies, thousands of galaxies?). However I agree that, for the purposes of this thread it's more-or-less irrelevant because you'd be switching the scenario mid-game (kinda like if the Rebels side with the Federation against the Empire, it's no longer SW vs ST but SW vs ST [with SW]). I guess someone could start a seperate thread to discuss this, though.

Except that's the entire point of the thread. It's not "hard vs. soft at full power", since, as you said, that's going to be a boring and one-sided match. The question here is which soft scifi civilizations could the hard scifi civilization defeat. IOW, at what point does their sheer size and development become enough of an advantage to make up for the lack of FTL and similar magic.

Well this goes back to "how are we defining a victory" which I've discussed elsewhere. If we're doing it in the traditional Fight To The Death of VS debates, I'd argue the HSF society can't win because they simply lack the ability to launch an effective offensive against the FTL side. As Darth Tedious said over on NT, time is on the FTL power's side. Let's take the scenario of, say, the SW galaxy happening to be 15,000LY from the Milky Way and that's how all this starts. For a society restricted to STL travel, how exactly are they going to get an invasion force over in 15,000+ years (emphasis on the plus, as I doubt they'd have a galactic-scale invasion fleet ready to go on the edges of the MWG) and the Empire can't do anything about it? And even if they get over to the SWG unharmed, they still have to go so very, very slowly in taking over the Empire, giving the Imperials plenty of time to counter-attack and, if nothing else, eat away at them bit by bit as it takes decades, centuries, millenia for the HSF invasion force to get anywhere the Empire's going to care about.

Same thing with the whole Planet Killer Asteroid strategy. Even if, (and that's a very big if*) the Empire, in its current state, can't deal with PK asteroids tossed their way at STL speeds, they've got thousands upon thousands of years to A) find out about it and B) actually do something to defend themselves. You really think they won't figure something out? A society that's built multiple planet and even solar system destroying devices over its history? And of course in the meantime they're still going around conquering the Milky Way so what exactly are you winning except possibly a Phyrric victory, at best.

*Do you really think the SWG has never had to deal with naturally occuring rogue asteroids that pose a threat to inhabited planets and have no way to deal with it? Heck they run the risk of large warships crashing into a planet after a space battle - which has certainly happened before - and they find a way to manage. Pretty sure they can deal with sublight speed space rocks, as well.

At best I'd say the HSF side can hope for a draw (again, using the standard Fight To The Death of VS debates), assuming they've got the high-end multiple galaxies scale and the Empire just gives up after awhile. But I don't see how they can even hope to really counterattack in the invaded galaxy(ies) with their speed disadvantage, unless they go for a scorched earth planet strategy of tossing rocks at their own captured systems and, again, hoping the Empire can't properly defend the recently conquered planets in the decades/centuries/etc of lead time they'd have. And even then, you had the Empire withdraw after taking over half your galaxy...by destroying the half of the galaxy they had overrun.

Congratulations?

[RogueIce]

Fucksticks, meant to hit edit, my bad. Please delete.

[lPeregrine]

You're missing the point. Let me reiterate:

What is the strongest science fiction faction a socially, politically, intellectual and morally enlightened civilization, that has passed all significant threats of extinction, defeat?

Note bolded. And the STL civilization (I despise the term 'hard' sci fi, since it evokes imagery of precisely of dick waving.) seems to be focused solely on hurling relativistic genocide packages across the galaxy to destroy anyone who MIGHT be a threat. Why not go whole hog and envision the Hard sci fi version of the Imperium of man? Why wait for them to come to you and just throw them out the minute you could start building them!

A few comments:

1) The scenario sets it up as a matter of power, not influence. By act of plot the armed conflict must start, just like the old SWvST debate doesn't assume that the Empire decides to accept a peaceful solution and freely offer enlightenment to their more primitive cousins. And, like it or not, military force in a hard scifi universe is likely to include (or even be dominated by) the use of planet killers.

2) Why are you assuming that such a civilization would be "enlightened" by the standards of 2012 human morality? Who knows where all of that could go over millions of years of divergence. For example, a civilization functioning as a single entity across multiple galaxies couldn't exist as a civilization of humans as we know them. Could beings evolved to exist on the absurdly long time scales where waiting a million years to hear a reply to a message is reasonable even relate to such a different civilization? Or would the "genocide" be considered merely the removal of an invasive pest species from the host body?

3) The use of relativistic planet killers isn't the point, it's the existence of them. You have them because other people have them, and you want to force a MAD stalemate where nobody is willing to use theirs against you. When the FTL invasion fleet arrives it's met by an offer: yes you can win any conventional battle with no risk, but we can retaliate by ending your civilization. Now go away and leave us in peace.

=======================================

If the FTL civilization is fighting the war before the RKVs launch, then the bombardment will take too long to arrive to affect the FTL civs plans, except that the FTL civilization may be less willing to negotiate surrender after the RKVs are on route. Also, hundreds of years is plenty of time to move their leadership to somewhere else.

Again, the successful arrival of the planet killers isn't the point, the existence of them is. "We have a billion planet killers on their way to each planet in your galaxy, if you go away and leave us alone we'll give the self destruct command." Is the FTL civilization really going to be so determined to fight to the death that they're willing to risk entire inhabited planets on the assumption that their defenses are 100%, and not 99.9999% effective?

=======================================

Well this goes back to "how are we defining a victory" which I've discussed elsewhere. If we're doing it in the traditional Fight To The Death of VS debates, I'd argue the HSF society can't win because they simply lack the ability to launch an effective offensive against the FTL side.

Which pretty much states the obvious. If it has to be a fight to the death where the only victory is the complete conquest or destruction of the other side, the discussion is over with the first post. "No FTL, no way to invade, nothing more to say".

So, any interesting scenario has to have victory conditions that represent strategic objectives either side could reasonably have. Since by definition the non-FTL side can't invade their only reasonable strategic objective would be to survive the war with their civilization intact. A defensive victory that avoids meaningful losses is the best they can do, so it should be considered a success.

As Darth Tedious said over on NT, time is on the FTL power's side.

I'd actually disagree with that point. Time is against the FTL power. Imagine the time scales a civilization would have to operate on to act as a unified entity across multiple galaxies. If you're used to measuring civilization-level events in millions of years the entire history of Star Wars passes unnoticed in a moment. In that sense, if the HSF civilization simply surrenders each planet as the invasion fleet arrives all they have to do is wait an imperceptibly short time for the invading civilization to age and die, long before the invaders can conquer any meaningful percentage of their territory.

[lPeregrine]

The exact details of how they’d win don’t seem that important. If they are going to win, it would be more logical to debate someone who is a closer match to the HSF power, but nobody seems interested in that.

Well, I did originally propose the planet killer attack for a general case, as a way of deciding which FTL civilizations could win the war (those that can effectively stop the planet killers and ignore the MAD threat). Somehow it turned into focusing on the Empire as the only opponent, and I'm not sure where.

[bilateralrope]

Again, the successful arrival of the planet killers isn't the point, the existence of them is. "We have a billion planet killers on their way to each planet in your galaxy, if you go away and leave us alone we'll give the self destruct command."

Or they could respond by saying: Either you give us the codes right now, along with the launch time and trajectory of every RKV you have launched so we can get the signal to them faster, or we will burn your entire system.
The FTL civilization can complete their genocide before the hard civs RKVs start hitting anywhere.

Of course, this requires that the RKV missiles actually have a self destruct function. Along with an explosive and detonator that will survive the intense g forces of launch without exploding, but still be functional after centuries in space. Is such an explosive compound even possible ?

Also, please convince me that it's possible to aim an unguided RKV to hit a planet across hundreds of light years.

* Even if I assume they can make a 20 AU+ long launcher that is straight enough to fire, I don't see how it can take energy weapons fire without the heat from them causing it to warp until it's no longer functional. I've already questioned how many times each RKV can fire before the heat from firing warps it to a non-functional state.

Sure, rocks might be cheap. Straightening a 20AU gun is not.

Is the FTL civilization really going to be so determined to fight to the death that they're willing to risk entire inhabited planets on the assumption that their defenses are 100%, and not 99.9999% effective?

It sounds better than believing the people who attempted genocide are telling the truth about giving the self destruct code, when proof of the code functioning won't exist until the signal catches up with the RKVs.

Also, both sides should be smart enough to realize two things:
- After the hard civ has attempted genocide, there is no way they will be allowed to keep their RKV launchers intact.
- Once the self destruct signal has been sent, there is nothing stopping the FTL civ from coming back.

[lPeregrine]

Or they could respond by saying: Either you give us the codes right now, along with the launch time and trajectory of every RKV you have launched so we can get the signal to them faster, or we will burn your entire system.
The FTL civilization can complete their genocide before the hard civs RKVs start hitting anywhere.

That's why it's a MAD scenario, the RKVs can't stop the other side from committing their own genocide campaign, but that's why:

1) They'd be used as a threat initially, not an unprovoked first strike. "Stop trying to conquer us or we'll make you pay".

2) They'd be used in response to a scenario the HSF civilization can't win. If you have FTL fleets launching hit and run attacks that you can't respond to you have two choices: surrender and hope they're merciful rulers, or attempt to force a MAD stalemate that makes the price of continuing the invasion too high to accept.

Since "the Empire sends scout ship and offers FTL and all that other nice stuff in exchange for a token promise of loyalty to the Emperor" isn't a very interesting scenario, we have to assume that the terms of surrender (if they're even offered) are unacceptable, and the HSF civilization has to use some kind of force to achieve an acceptable resolution to the conflict. And if you know you're doomed anyway the threat of being even more doomed if you don't give up your retaliation isn't a very compelling one.

Of course, this requires that the RKV missiles actually have a self destruct function. Along with an explosive and detonator that will survive the intense g forces of launch without exploding, but still be functional after centuries in space. Is such an explosive compound even possible ?

It doesn't have to be a literal self destruct, just fire the engine off-course and it misses the target.

Also, please convince me that it's possible to aim an unguided RKV to hit a planet across hundreds of light years.

Why? I already said it can be a rock with an engine, and predicting a planet's exact position in the future is not really a difficult challenge.

[fusion]

Since the op never really specified that the Soft-Sci society had to defeat the Hard-Sci society, I am going to go on a bit of a tangent compared to the rest of the thread.

The biggest problem a Hard-Sci has with the Soft-Sci society would be mobility and the application of power. Since we are assuming that nothing can go faster than the speed of light for the Hard Sci society, they would have trouble dealing with any Soft-Society that are nomadic in nature, like the Culture. The Culture's biggest advantages would not only be the fact that their entire society is essentially mobile (they could even move the Orbitals during the war, but just not fast enough), but also the fact they can fire nova scales of energy in fractions of a second (See Vympel's interview with Iain M. Banks), allowing them to systematically wipe out entire systems at a time. If a Hard Sci society tried to retaliate there would be no targets for the society to target. Even if they managed to hit all planets in the other galaxy (after a course of a hundred thousand years), they would not be able to even hurt a nomadic society like the Culture even if they were to fire a good fraction of the mass of galaxy.

However, even if we looked at a smaller scaled societies, like the remnant of the Colonial fleet (if we were to call that a society). Such society would still be near impossible for the Hard-Sci society to eradicate even if the Soft-Sci society could not do much to the Hard-Sci society.

So, therefore to answer the OP's question, it depends on weather or not the Soft-Sci is nomadic. If they are, then even a civilization less advance and of a smaller scale than the Federation could with stand the brunt of Hard Sci Society. However, if they are not nomadic, it may take a civilization with a scale even larger than Star Wars to not lose the war.

[the atom]

And note that even that isn't 100%. Remember, the target is moving (on the scale of hundreds or thousands of years), so if you don't know exactly when the shot was fired and how fast it's moving you won't know exactly where the target is going to be when the shot arrives. And without that knowledge you don't know the exact trajectory of the shot even on a purely ballistic course.

You're assuming an advanced FTL civilization can't do basic math?

An FTL capable society could probably also sent FTL probes to the home system of the aggressive STL society and observe the construction, aiming, and firing of the weapons directly without having to detect the individual projectiles from scratch. Though so far we've constrained the discussion to Type II civilizations. How would an FTL empire deal with a fully exploiting STL society that already occupies a substantial portion of the galaxy?

Depends on the civilization, but wanky franchises like Stargate, Starwars, or Star Trek would shred through such a civilization like a hot chainsaw through a really big stick of butter.

On a less related note, this would make for an absolutely fantastic premise for a fanfic.

[lPeregrine]

And note that even that isn't 100%. Remember, the target is moving (on the scale of hundreds or thousands of years), so if you don't know exactly when the shot was fired and how fast it's moving you won't know exactly where the target is going to be when the shot arrives. And without that knowledge you don't know the exact trajectory of the shot even on a purely ballistic course.

You're assuming an advanced FTL civilization can't do basic math?

Err, what? That's not at all what I'm saying. The point is that there are multiple valid paths between point A and point B, depending on how fast the planet killer is moving (since the target will be in a different location depending on how long it takes the shot to get there), when exactly it was fired, if the planet killer has engines it can use to take an indirect path instead of a purely ballistic one, etc. It's not as simple as just drawing a line between point A and point B and placing a shield somewhere on that line, you have to sweep a potentially huge volume of space to find the planet killer.

[bilateralrope]

After writing this post, I'm starting to question if RKV spam is viable against an unsuspecting hard sci-fi civilization. Let along a soft one.

That's why it's a MAD scenario, the RKVs can't stop the other side from committing their own genocide campaign, but that's why:

1) They'd be used as a threat initially, not an unprovoked first strike. "Stop trying to conquer us or we'll make you pay".

If the RKV's haven't been fired when the soft civ starts fighting, then the RKV guns are going to be priority targets for hit and run attacks. They don't need to destroy the gun. They could melt through the barrel with the aim of blocking it up with molten metal, they could take out the power supply or they could target the thrusters used to aim it*. Either way, the gun will need intensive repairs.

So they aren't going to get off many shots, especially with the difficulties of aiming the guns at anything.

If the hard civ does manage to fire the gun after the soft civ is in system, the soft civ will know enough information to plan an intercept.

The friction of the projectile against the sides of the barrel is going to be nasty. I feel justified in asking how hot the projectile will be once it exits the gun.
Hot enough to melt the guidance systems ?
Hot enough to melt the entire projectile ?
Hot enough to leave lumps of the projectile/gun lining inside the barrel for the next shot to crash into ?

*How much mass are these thrusters going to expend every time the gun is aimed?
How would you program the thruster control computers to take the ability of the FTL civ to disable thrusters without warning into account when messages will take nearly 3 hours to travel from one end of the gun to the other ?

Of course, this requires that the RKV missiles actually have a self destruct function. Along with an explosive and detonator that will survive the intense g forces of launch without exploding, but still be functional after centuries in space. Is such an explosive compound even possible ?

It doesn't have to be a literal self destruct, just fire the engine off-course and it misses the target.

That's a bit better. Though the engines and radio receiver still need to survive launch, which is something you're going to need to prove.

Also, please convince me that it's possible to aim an unguided RKV to hit a planet across hundreds of light years.

Why? I already said it can be a rock with an engine, and predicting a planet's exact position in the future is not really a difficult challenge.

Predicting the planet seems easy. Aiming the 20 AU gun isn't. An AU is 149,597,870,700 meters. Lets call that 150,000,000km for simplicities sake. So you have a 3,000,000,000 km long gun.

Lets say that you manage to get the muzzle within 1km of where it needs to be relative to the base. Which is bloody impressive given the size and mass of the gun. At 6x109 km from the base (1 gun length from the muzzle), you're within 2km, with a linear progression.

Earth has a mean radius of 6,371.0 km. So if you're aiming at the center, you need to be within 3,185.5 km when the projectile passes by. So you can only hit earth 100% of the time within 3,185 times the length of the barrel. Which is 9.555 x1012km. A light year is 9.4607×1012 km.

So you basically only get to hit Earth if you're within 1 light year. At 2 light years you have a 25% chance, as the area your shot will go through is increasing at the square of the distance. 3ly, 1 in 9 chance.

So unguided RKV spam isn't going to be reliable. Which leaves guided RKVs, which have problems:
- Any mass used to correct the course is mass not used for the impact. The more efficient the engine is at using mass, the more power it will need.
- Any guidance system needs to be robust enough to survive the launch.
- It needs to survive, and remain powered, for centuries.
- It needs sensors on it so it can find the target. Simple sensors are more robust, but also easier for the soft civ to fool once they know what frequencies the sensors are looking for.
- The sensors might not looking for a frequency that the soft civ doesn't produce. For example, they might decide to have it look for the largest concentration of radio signals. Against a hard civ that would work, as radio means populated. But the Federation doesn't use radio, making it a bad choice.

Err, what? That's not at all what I'm saying. The point is that there are multiple valid paths between point A and point B, depending on how fast the planet killer is moving (since the target will be in a different location depending on how long it takes the shot to get there), when exactly it was fired, if the planet killer has engines it can use to take an indirect path instead of a purely ballistic one, etc. It's not as simple as just drawing a line between point A and point B and placing a shield somewhere on that line, you have to sweep a potentially huge volume of space to find the planet killer.

For the RKV to have the relativistic element, it needs to be moving fast. It's also going to be a rather small projectile, meaning there isn't much mass to use as propellent. I don't see how the projectile could carry enough propellent to do anything more than correct for inaccuracy in the guns aim. Maybe it won't even be able to do that.