On "realistic" space combat and planetary invasions

[Number Theoretic]

I see the point. It would be strategically wise to test it on a star that was prone to go nova anyway. The perfect opportunitiy to prove the weapon works as well as to conceal it. Nobody would ever know, and that is exactly the situation now, as i understand it.

[VarrusTheEthical]

I see the point. It would be strategically wise to test it on a star that was prone to go nova anyway. The perfect opportunitiy to prove the weapon works as well as to conceal it. Nobody would ever know, and that is exactly the situation now, as i understand it.

Betelgeuse

[Number Theoretic]

Betelgeuse

For example. And if you were looking for other candidates, i would rather stay away from this star. If not, it's resulting hypernova could be seen from the entire Human Sphere.

[Rabid]

A Rough Timeline, Part 1

[all dates are in Current Era date format. Dates in-setting may follow another format]

3th Millennium : Conquest & Colonization of the Solar System. Earth as the central authority of the system until the Martian, Jovian & Main Belt revolts. Decentralized “federation” after these events.

2095 : First out-of-earth permanent human civilian settlement - “Alpha Station”, a.k.a “Gagarin”, a private space station. Projected to house 250 permanent inhabitants and 500 visitors ; technical success, commercial failure, de-orbited twenty years after completion in 2120.

2130 : First permanent civilian colony on the Moon - “Armstrong City”. Used as a shipyard & luxury resort. Initial population : 800. Twenty years after foundation : 50,000.

2143 : First permanent (non civilian) settlement on Phobos. Used as a bridgehead & spaceport for future colonization efforts of Mars.

2150 : First permanent civilian settlement on Mars, in the equatorial region.

2158 : Establishment of the first Valles Marineris' Dome City. Total population of the Martian system : 100,000 to 200,000 people, Phobos, Deimos & orbiting space stations comprised.

2184 : Inauguration of the first Venusian settlement, an “airship-city”. Is only a beach-head for the Venusian Terraformation Effort (evacuation of the atmospheric CO2 to Mars & other colonies), most of the population of the Venusian System living in orbit of the planet.

[Development & colonization of the whole Solar System]

2321 : Mars (planet) reach the symbolic threshold of One Billion inhabitants, roughly a quarter of this number living in the Valles Marineris Megacity ; the Martian System holding a population of roughly 2 billion people. By comparison, Earth (planet) has dropped back to 6 billion people, after a 12 billion spike in the end of the 21st century. The Earth-Moon System OTOH, is inhabited by 14 billion people. The human population in the Solar System is close to 25 billion people.

2405 : Mercury totally covered by solar panels. Power transmitted by High Energy Interplanetary Laser to the various colonies of the system. Is also a defence system in case of Alien Invasion.

2503-2515 : War of independence, or Revolutionary War. Mercurian Lasers used mid-conflict by Earth to severely harm the Phobos Colony. Mercurian Lasers captured by the Rebels at the end of the conflict, used to hold Earth hostage. The Nations of Earth surrender their hegemony on the Solar System and grant total autonomy to every colonies in the Solar System.

[The Solar System continue to develop. Birth of FTL theory in the 28th century]

2956 : First experiment on FTL Drives in the outer-edge of the solar system. Dramatic failure, ship destroyed. No human harmed.

Early 2963 : First “successful” experiment on FTL. Automated Test Ship 07 not returning from its journey.

Late 2963 : Radio signal from ATS-07 onboard AI, assessing mitigated success of first jump, problem coming from a drive failure (drive stopping in-flight from “excessive charge buildup”, 0.6 LY from Earth, insufficient to reach its intended target Proxima Centauri), and communicating a deviation from plotted course. Data used to correct FTL theory and drive design where necessary. ATS-07 put on standby mode, still keeping data transmissions coming just to let know that it is still functional, until corrected drive designs can be uploaded to it, for its onboard repair & manufacturing capabilities to repair & update its drive (not so much as to save the ship itself than to test the limits of the onboard AI and its autonomous self-repair capabilities)

2964 : First completely successful FTL experiment : ATS-08 reach the Proxima Centauri system in twenty days after two major and three minor deviations from its course, stay there for a week to takes pictures of the Star and try to detect any planetoid, and come back to the Solar System in twelve days after only one major and six minor deviations from its course

Late 2964 : ATS-08 is retrofitted for a search & rescue operation and sent after the projected coordinates of ATS-07 to transmit corrected drive schematics to its AI, help it rebuild its drive & to test rendez-vous capabilities in deep-space. ATS-08 come back one month after the start of the mission, assessing the successful completion its own primary missions (deliver FTL-Drive blueprints & repair bots), and is sent back to ATS-07 to monitor its progress. ATS-08 come back home five weeks after the start of its secondary mission, ATS-07 following only three weeks after -08's return due to a buggy integration of the new Drive in the ship's systems and subsequently several important navigation errors.
These missions are considered to be a testament to the resilience, autonomy and adaptability of ATS-07 & -08 AIs.


[end of Part 1 of the Timeline]

[Number Theoretic]

A quite elaborate, and almost complete line of history, so far. If i recall correctly, the Great War was due to start somewhere in the 5th Millennium and the timeline has almost reached the beginning of the 4th Millennium. So the gap spans "only" a thousand years. Considering that my own setting has a huge gap between the 4th millennium and some time set a quarter million years in the future it seems quite "complete" to me. And i like the idea of "airship-cities". The more "non-earthlike" settlements, the more interesting your setting gets. Could even be justified by the theme that earthlike planets are incredibly valuable.

Do AI exist ? Yes.
Are they sapient? Yes.
Do they think like us ? No. To be honest, to us humans their mind is totally foreign and quite beyond our capacity for empathy.
Is their intelligence superior to a human one ? It is superior in some domains, inferior in others ; incredibly good at all things mathematical or that can be reduced to pure logic, but abysmal at anything creative, or non-deterministic-but-not-quite-random (or at least the last part is the general consensus – I'm told some people like AI music...).

Concerning the role of AIs, i have a similar take on this subject. They are an integral part of every spacefaring society and most AIs simply think in completely different ways than humans. Would be interesting if an "AI fallacy" had accidentally started a war in the past. Not necessarily because the AI suddenly became evil, but more of a misconception on its side.

Minor nitpick on FTL, because i just couldn't resist: If FTL navigation was fast in theory, i would conjecture that it is not so fast in practice because either current technology doesn't meet energy requirements that could make it more "robust". To be fair, you hinted at that in the answer to my question on whether there have been adventurers travelling to other galaxies.
The only other reason why FTL isn't as fast as theory suggests could be of navigational hazards caused by the environment "galaxy". But then an intergalactic journey would be much less problematic than an interstellar one within a distinct galaxy. So, is it a energy-thing or a navigation thing that keeps FTL below its theoretical limit?

[Rabid]

So, is it a energy-thing or a navigation thing that keeps FTL below its theoretical limit?

During an interstellar travel, 3/4 - 4/5 of the time is taken by navigation calculation, and the rest is charging your drive to engage the FTL-Leap (not quite a jump...).

Your best bet to reduce time travel would be to have the best Telescopes and Sensor arrays you can imagine (and then some), in conjunction with the best AIs.

On a side note, this is one of the reason why Interstellar Carriers (mostly civilian ships without any armament whose job is facilitating Interstellar Travel) have the best and most powerful Sensor Arrays, AIs and FTL-Drives available outside of [CONFIDENTIAL DEFENSE].


... I think I'm going to draw something in order to help people understand how Interstellar Travel function...

More on the timeline tomorrow if I can manage it.

[Esquire]

I've got two brief questions, one on the Venusian 'airship cities' and another on Interstellar Carriers.

About the cities, why bother? It seems to me that designing a city to survive in an environment like the atmosphere of Venus would be both more difficult and more expensive than simply using a space station. How many cities are there? If there's just the one to serve as a terraforming base, all well and good, but if there's more, why?

The Carriers - you say they have extremely advanced equipment, and they sound like they're quite large. Both of these qualities deserve protection, so why are they unarmed? Do they travel with a military escort from whoever owns the ship?

[hermitbob]

I just want to point out something that was overlooked for planetary invasions.

Gas.

That is all.

[Patrick Degan]

I just want to point out something that was overlooked for planetary invasions.

Gas.

That is all.

Overlooked, perhaps, because it's the least reliable weapon.

[Rabid]

A quick update (sorry, I'll answer your other questions later today)

A drawing about Interstellar Travel (2-Dimensions problem simplification)
[28 KB PNG image]




The "game" in Interstellar Navigation, is to follow the trajectory with the less Rest-Points possible (longest FTL-Leaps possible) while staying as far as you can from any gravity-well.
I'll remind everyone that the FTL-Leaps themselves are nearly instantaneous at these scales for all intent and purpose (explain why Route A's 3rd projected Rest-Point is so far away)

[Rabid]

About the cities, why bother? It seems to me that designing a city to survive in an environment like the atmosphere of Venus would be both more difficult and more expensive than simply using a space station. How many cities are there? If there's just the one to serve as a terraforming base, all well and good, but if there's more, why?

At the time, there was a handful of such cities. They were primarily populated by people from the Venusian Terraformation Effort, but a significant part of their income also came from Tourism. All Airship Cities combined, their permanent population was just a bit under the million mark, including the rich eccentrics who decided on living there just for the sheer awesomeness of the thing and the bragging rights.
They had a mundane utility (permanently, safely and comfortably housing people and industry planetside) but were also a giant "fuck you !" toward Venus' Mother Nature (permanently, safely and comfortably housing people and industry planetside on the planet which most closely match the common definition of "Hell", by living in the skies).
A case of "Humanity, fuck yeah !".

The Carriers - you say they have extremely advanced equipment, and they sound like they're quite large. Both of these qualities deserve protection, so why are they unarmed? Do they travel with a military escort from whoever owns the ship?

The carriers, on their own, aren't armed. They have to rely on an escort to defend themselves
When they travel on safes routes (97% of the time) they only mount an automated defense platform which offer a token form of protection. In the other 3% of the time, they are escorted by one or several Corvette, or even Frigates when headed to a warzone. These 3%-of-the-time escorts are generally operating under the League's flag (as it is one of its main Duty, after all), or more rarely by mercenaries when people want to do something without having the League too close.
No circumstance necessitate for a carrier to have a more serious escort, because if they were to be "escorted" by heavier ships (like a Cruiser or heavier), given their mass it wouldn't be their "escort", but their primary payload.



[Ship "classes" are just indicated as a convenient parallel with Real Life Navies and the role in which they are used. It is not indicative of the final names, appearance or range of functionalities of said "classes"]

[Esquire]

Thanks very much for the response(s). I'm glad to know there's reasons for things, and that they're well-thought-out ones - such a nice change of pace from today's usual fare.

[Tierras Quemadas]

Has anyone ever tried to interdict FTL in your setting?

It seems like the fastest routes between systems are widely known and regularly traveled. Do terrorists/empires ever leave mines at common Rest-Points? Or drag asteroids around to throw off incoming traffic? Could a system completely shut itself off from FTL travel if it had the time/resources to interstellar space with big rocks?

[Esquire]

Would an asteroid have enough mass to significantly effect FTL trajectories? It sounds like the only really noticeable gravity wells are those of entire solar systems.

[someone_else]

Random stuff that I find strange, no offence intended, just nitpicking.

" How do you invade a planet when said planet has a population counting in the billions, a technological and industrial parity with you, and you want to take the planet as intact as possible and without creating hazards toward its human habitability (bioweapons, uncontrollable nanoplagues, etc...) ? "

Easy. Buy everything in sight. Systematically. Economical domination is the only way for worlds with so much population you don't want to engage in looooong knife fights.

And most habitable planets can resist easily a blockade for millenia.

We don't know exactly how, or why it happened, but one of the asteroid-colony that had been put into orbit around Earth was de-orbited, and fell into the Pacific.

I'd like to know the rationale beind the decision of moving a so big asteroid so close to Earth and leave it UNGUARDED. Especially in a setting where everyone and their dog have engines that can deorbit the gigantic rock.

the size of individual space habitats orbiting planets has been limited, to limit as much as possible the damages that could result from a colony drop.

Which would be not that much if compared to the rock that you fell on Earth, i'm inclined to think that even 3-4 km habs will shatter in reentry due to the fact that they are not designed to take the reentry loads and they are not horribly strong in the first place.

Get out of FTL, calculate the ship's position for something between a few dozen minutes to several hours, 45 minutes being what's usual. Note that if the stellar sensors (a.k.a. Telescopes) onboard the ship have been damaged and are not repaired, this phase can take whole days, or even weeks, as the ship's AI will have to use mediocre data coming from the constellation of cameras monitoring the hull status, or even the optical sensors of the robots used to repair the hull. This has the consequence of making the ship's telescopes ones of its most precious and protected elements, right after the FTL drive itself and the ship's power generator.

Star trackers are a relatively mature tech by now, I think their part of the job can be speedied up a bit.

Run a quick calculation to verify the good orientation of the ship. With functional stellar sensors, this takes generally less than ten minutes. Otherwise, that's easily another 3 hours of calculus.

If it just needs to check the current orientation, star trackers can do it in a tiny time and without human hands.

A ship in FTL generate gravitational waves which act as a Mach Cone, which in turn can allow someone with the right equipment to detect a passing ship in FTL

from what distance? consider that even a light year is shit for interstellar, but to generate a signal that can be heard from that distance you need buttloads of power. You're better off saying that other FTL drives "feel" each other's presence after a certain distance.

a great part of this history has been lost, as no other of its archives on Luna, Mars or in the rest of its local agencies throughout the Sphere were as complete.

That's kinda strange. Past history does not grow in size,while storage capacity of most digital stuff keeps rising.
Not having multiple full backups off-planet sounds somewhat strange to me.

They (carriers) are also heavily automated, much more so than other ships, and some of them have been known to make whole journeys without any human onboard ; their crew otherwise being ordinarily composed of less than ten people.

Given the timeframe, automation will easily handle the tasks of these things. What is there the crew for? Servicing the damn thing?

The Human Sphere suddenly ignited in War, as eight hundred years of hidden tensions, petty grudges and bitter resentments came back to the surface.

800 years? that's like saying we have any resentment toward whatever happened to be our enemy in the middle ages. Although UK and France can be an example of that...

so let us only say that this period of generalized Total War lasted for a hundred year

Must have been very low intensity warfare. I have troubles in imagin any modern warfare between more or less even opponents lasting more than a year...

The carriers, on their own, aren't armed. They have to rely on an escort to defend themselves

Cool, so while the main forces are zapping each other, teams of scouts and fast cruisers try to locate the enemy's carriers to destroy them and fuck up his fleet's ability to jump together.

[someone_else]

A ship in FTL generate gravitational waves which act as a Mach Cone, which in turn can allow someone with the right equipment to detect a passing ship in FTL

from what distance? consider that even a light year is shit for interstellar, but to generate a signal that can be heard from that distance you need buttloads of power. You're better off saying that other FTL drives "feel" each other's presence after a certain distance.

Another clarification: gravity waves go at lightspeed. So detecting a vessel jumping at you takes decades unless it is making the jump in your back yard. Or you change the way to allow detection.

[jollyreaper]

Big question: what are they fighting over? What are the economic interests? Sticking with strict realism, unless earth like planets are common, it will always be cheaper to build a space hab than, say, terraform mars. Need minerals? Asteroids. Need power? Look at te sun. Why would one system need to trade with another?

I'm sure there are really good answers here but most scifi just takes today's world and puts it in space. We actually see planets importing food over interstellar distances. Really???

I find myself falling in the Charlie Stross camp about interstellar empires making little sense without good justification but dumb people may give it a go anyway.

So, what could you have on your planet that's worth conquering it for?

A lot of this comes down to the tech involved as to what the answers would be. It could well prove that the homeworlds are unassailable and only border territories could be swayed one way or another. The battle could be over some philosophical or religious point like allowing slavery or cloning or immortality treatments. There's no economic incentive or maybe somehow there is.

[Guardsman Bass]

Random stuff that I find strange, no offence intended, just nitpicking.

" How do you invade a planet when said planet has a population counting in the billions, a technological and industrial parity with you, and you want to take the planet as intact as possible and without creating hazards toward its human habitability (bioweapons, uncontrollable nanoplagues, etc...) ? "

Easy. Buy everything in sight. Systematically. Economical domination is the only way for worlds with so much population you don't want to engage in looooong knife fights.

And most habitable planets can resist easily a blockade for millenia.

It's still only a single planetary system in an interstellar empire. It would be possible, if hugely resource-intensive, to launch a massive fleet invasion to destroy the planet's defense fleet and establish space superiority (which also likely involves targeting any ground-to-space weaponry). After that, you can land troops wherever you want to, or do strategic strikes from orbit on planetary targets.

You'd need a really good reason for wanting to spend those resources, though.

They (carriers) are also heavily automated, much more so than other ships, and some of them have been known to make whole journeys without any human onboard ; their crew otherwise being ordinarily composed of less than ten people.

Given the timeframe, automation will easily handle the tasks of these things. What is there the crew for? Servicing the damn thing?

The Human Sphere suddenly ignited in War, as eight hundred years of hidden tensions, petty grudges and bitter resentments came back to the surface.

800 years? that's like saying we have any resentment toward whatever happened to be our enemy in the middle ages. Although UK and France can be an example of that...

What if your overall population is near-immortal? An 800-year grievance is possible in that situation.

Sticking with strict realism, unless earth like planets are common, it will always be cheaper to build a space hab than, say, terraform mars. Need minerals? Asteroids. Need power? Look at te sun. Why would one system need to trade with another?

I'm sure there are really good answers here but most scifi just takes today's world and puts it in space. We actually see planets importing food over interstellar distances. Really???

This isn't a strictly realistic setting, so it actually might be cheaper and faster to send goods long-distance via the setting's arbitrarily-defined FTL than shorter distances using more realistic rocketry. That's happened before in real life due to technological limitations (it was cheaper to send goods 2,000 miles across the Mediterranean by ship than 100 miles over land during Roman times IIRC). Perhaps it's cheaper for the orbital shipyards to get raw materials from the asteroid belt in another solar system, then to mine them from a nearby large moon with non-negligible launch costs.

Solar power is nice, but it's also bulky. That's not a problem for relatively immobile space colonies and planets, but it would be an issue for space ships (and particularly warships that need to minimize their target area).

[jollyreaper]

I'm thinking of the cost of getting mass out of a gravity well. If it's dead cheap, why isn't recycling cheaper?

Cheap energy means we can eat salad from 3000 miles away, Romans would crap if you told them that. But if energy were 30x higher, would local greenhouses and hydroponics make more sense? Probably.

I would think it wouldn't even be possible for a planet to be a net importer of food. Then again, who would have thought the US would outsource manufacturing? Goddamn garlic at the store is from China.

[Guardsman Bass]

I'm thinking of the cost of getting mass out of a gravity well. If it's dead cheap, why isn't recycling cheaper?

Recycling usually requires energy and equipment to do it, and that may not be profitable in a setting with cheap launch costs and even cheaper interstellar shipping. For most materials today, recycling isn't profitable.

That said, I'm not sure if that actually fits with Rabid's setting. You could still have a situation where the planet is a net importer of goods and materials if sending stuff down the gravity well is cheap, though. I was mostly thinking of space colonies when I made my post.

I would think it wouldn't even be possible for a planet to be a net importer of food. Then again, who would have thought the US would outsource manufacturing? Goddamn garlic at the store is from China.

I agree. Interstellar shipping as well as shipping down the gravity well would have to be very cheap to compete with planet-side food production, even if the planet's natural environment is hostile towards farming in the open.

[Rabid]

Global response to all since my last post :

- - - - - - - - -

On FTL-interdiction :

Has anyone ever tried to interdict FTL in your setting?

It seems like the fastest routes between systems are widely known and regularly traveled. Do terrorists/empires ever leave mines at common Rest-Points? Or drag asteroids around to throw off incoming traffic? Could a system completely shut itself off from FTL travel if it had the time/resources to interstellar space with big rocks?

It is not possible for anyone to force a ship out of FTL, unless you could generate a black-hole and have the ship pass so close to it that it would surcharge its FTL drive and force an emergency shutdown. Such a distance would be something like less than 100 time the diameter of the event-horizon : it is a very small zone of space, at the scale we are talking about.
The FTL route themselves can be considered like corridor more than 0.5 LY in diameter.

Short answer : no, you can't practically interdict FTL between systems in this setting.

Would an asteroid have enough mass to significantly effect FTL trajectories? It sounds like the only really noticeable gravity wells are those of entire solar systems.

FTL-drives only begin to be noticeably perturbed by planetary-sized gravity-well, and then it will only deviate the ships from their course, not force them out of FTL.


- - - - - - - - -

Answer to Someone_Else's post :

" How do you invade a planet when said planet has a population counting in the billions, a technological and industrial parity with you, and you want to take the planet as intact as possible and without creating hazards toward its human habitability (bioweapons, uncontrollable nanoplagues, etc...) ? "

Easy. Buy everything in sight. Systematically. Economical domination is the only way for worlds with so much population you don't want to engage in looooong knife fights.

And most habitable planets can resist easily a blockade for millenia.

Economic warfare can only go so far, especially when people start to refuse being bought out.

We don't know exactly how, or why it happened, but one of the asteroid-colony that had been put into orbit around Earth was de-orbited, and fell into the Pacific.

I'd like to know the rationale beind the decision of moving a so big asteroid so close to Earth and leave it UNGUARDED. Especially in a setting where everyone and their dog have engines that can deorbit the gigantic rock.

It was there since even before the invention of FTL, a product of the hubris of the human civilization at the time ; and no one had ever tried to Colony-Drop it on Earth since then, as during the Great War (the period where someone would have been the more likely to want to drop it on Earth) it was used as a Space Fortress.

Some rumours say that what caused it to drop was sabotage, but there are no proofs. The structure being more than three thousand years old, it could have been just a terrible incident.

the size of individual space habitats orbiting planets has been limited, to limit as much as possible the damages that could result from a colony drop.

Which would be not that much if compared to the rock that you fell on Earth, i'm inclined to think that even 3-4 km habs will shatter in reentry due to the fact that they are not designed to take the reentry loads and they are not horribly strong in the first place.

Even then, it's still a great big chunk of metal falling from orbit at very high speed. And the Habitats before where far bigger than just 3-4 km : it was common for them to be larger than 10-15 km, some people even having created proto-ringworlds more than 100 km in diameter.

Star trackers are a relatively mature tech by now, I think their part of the job can be speedied up a bit.

'kay, thanks. I'll look into it. But still then, the calculations involved are complex and take some time – maybe less than I predicted, but still it is non negligible.

A ship in FTL generate gravitational waves which act as a Mach Cone, which in turn can allow someone with the right equipment to detect a passing ship in FTL

from what distance? consider that even a light year is shit for interstellar, but to generate a signal that can be heard from that distance you need buttloads of power. You're better off saying that other FTL drives "feel" each other's presence after a certain distance.

I didn't want to imply that you could sense a ship passing by on an FTL-route ; what I say is that when inside of a solar system, if a ship pass by in FTL by roughly an AU, you can sense it with the proper equipment.

a great part of this history has been lost, as no other of its archives on Luna, Mars or in the rest of its local agencies throughout the Sphere were as complete.

That's kinda strange. Past history does not grow in size,while storage capacity of most digital stuff keeps rising.
Not having multiple full backups off-planet sounds somewhat strange to me.

“History” is more than Chronicles : it is documents, battle reports, trade-contracts, etc...
The chronicles of the most important facts are still around, as are some of the more obscure chronicles ; but documents referring to what happened to some obscure part of the Human Sphere far away from Earth are either lost forever, or lost in some distant University's vaults you don't even know the existence of :
What has has been lost is the central repository of these documents, which greatly impede any research efforts on a lot historical subjects, as you have to figuratively run around the Human Sphere to gather all the necessary documents, without any central “authority” able to tell you if these documents exist in the first place.
The Moon and Mars had doubles of some of the most important stuff, but the “insignificant” documents where kept only on Earth and were they came from (if this place still existed or hadn't deleted them already). Nobody care if “transport contract #15258-A17-GHB” is lost. The problem is, it may hold information that, in context, are important ; if it is lost, we'll never know.

Also, nitpick : the “past” is ever increasing, you know ?

They (carriers) are also heavily automated, much more so than other ships, and some of them have been known to make whole journeys without any human onboard ; their crew otherwise being ordinarily composed of less than ten people.

Given the timeframe, automation will easily handle the tasks of these things. What is there the crew for? Servicing the damn thing?

Authorities feel more comfortable by leaving some humans in the loop to deal with the unexpected, even if the onboard AIs could very well deal with it on their own.
Also, yes, they do some maintenance and help with some humans aspects of the travel : when multiple ships are docked on one Carrier, for example, they “supervise” things – you don't want brawls between rival crews in the Common Quarters / watering hole of the Carrier...

The Human Sphere suddenly ignited in War, as eight hundred years of hidden tensions, petty grudges and bitter resentments came back to the surface.

800 years? that's like saying we have any resentment toward whatever happened to be our enemy in the middle ages. Although UK and France can be an example of that...

The average lifespan in the Sphere is around 200-250 years, and there are a number of people who are functionally near-immortal.

so let us only say that this period of generalized Total War lasted for a hundred year

Must have been very low intensity warfare. I have troubles in imagin any modern warfare between more or less even opponents lasting more than a year...

At the time, it wasn't really one great war. It is more that the Cold War between the two Super-Blocks slowly escalated, skirmish after ambush, in the span of a few years, after what people decided to break the Big Guns. But even with all their fire-power, the Sphere is a big place, and armies can't be anywhere at any time. So the combats were drawn on and on, strategic redeployment after strategic redeployments, campaign after campaign... People were also still somewhat reluctant to go into a real “total war” mode.
This until one Commander imposed his view for the necessity of a decisive action, which resulted in the launch of the Hundred Worlds Campaign. Its aim was simple : to totally gut the enemy of its most important worlds and colonies. This is during this Campaign that were used the World-Crackers, these FTL-Powered engine of mass destruction, only one able to destroy a world without getting in range of the enemy defenses.
With the destruction of more than one hundred worlds, the fight took a turn for the ugliest, which as the years passed and people died billions after billions shattered morales and convictions, until the two Blocks imploded.
After that, followed half a century of “political and diplomatic re-adjustment”, which was still ugly.

This only after the facts that the whole period was dubbed the “Great War”.

The carriers, on their own, aren't armed. They have to rely on an escort to defend themselves

Cool, so while the main forces are zapping each other, teams of scouts and fast cruisers try to locate the enemy's carriers to destroy them and fuck up his fleet's ability to jump together.

More or less. But generally the Carriers used in an active war-zone aren't exactly the same that those that are used in peace time. Fleets tend to prefer to use Mobile Fortresses, hollowed-out asteroids serving as dedicated military Carriers, if only for the increased capacity allowing the transportation of several Capital Ships with their escort fleet, and the on-board repair facilities of the fortresses.


- - - - - - - - -

Big question: what are they fighting over? What are the economic interests? Sticking with strict realism, unless earth like planets are common, it will always be cheaper to build a space hab than, say, terraform mars. Need minerals? Asteroids. Need power? Look at te sun. Why would one system need to trade with another?

I'm sure there are really good answers here but most scifi just takes today's world and puts it in space. We actually see planets importing food over interstellar distances. Really???

I find myself falling in the Charlie Stross camp about interstellar empires making little sense without good justification but dumb people may give it a go anyway.

So, what could you have on your planet that's worth conquering it for?

A lot of this comes down to the tech involved as to what the answers would be. It could well prove that the homeworlds are unassailable and only border territories could be swayed one way or another. The battle could be over some philosophical or religious point like allowing slavery or cloning or immortality treatments. There's no economic incentive or maybe somehow there is.

Habitable planets are rare, and the Human Sphere is heavily politically divided : a majority of the “empires” (the term isn't really adapted) do not possess any habitable planet at all. It a sign of great prestige for an empire to have a planet.
Now, wars between “empires” aren't that common, and it is rare for planets to be under siege. But it happen. Generally, it is because a planet-less empire want to acquire the planet ; or to deprive an empire from its only planet, in the hope to force its surrender.
Planetary Siege are almost always war of conquest, where the assailant want to limit collateral damage as much as it can.
If one empire menace the other of “planetary destruction”, you can safely bet that the League will step in to stop the fighting...


- - - - - - - - -

On the cost of space-travel :

I haven't totally planned things yet, I'm still working on it.

For information, nuclear fusion is widespread, and M/A reactions are used for some applications needing a lot of energy in small amount of time.
Most ship use “capacitor” banks fed by the fusion reactor of the ship to fuel the FTL-Drive ; but the bigger ships (Cruisers & up, including Carriers) instead use cartridges of antimatter.

To create antimatter, the energy efficiency of the creation process is in the ballpark of 0.1%. Same thing if you want to create matter : this explain why people are still mining asteroids instead of creating all they need from the Vacuum.

[someone_else]

It's still only a single planetary system in an interstellar empire. It would be possible, if hugely resource-intensive, to launch a massive fleet invasion to destroy the planet's defense fleet and establish space superiority (which also likely involves targeting any ground-to-space weaponry). After that, you can land troops wherever you want to, or do strategic strikes from orbit on planetary targets.

Dunno, the US has issues in trying to pacifying something the size and population of Afghanistan (with an afghanistan techlevel too), pulling off the same trick on an entire fucking world with 3-4 billion people on it (and possibly a better techlevel) sounds pretty hard to me.

The issue isn't winning the shooting contest, it's making sure they do what you want them to.

Economic warfare can only go so far, especially when people start to refuse being bought out.

You are doing it wrong. You need to buy companies, not people. Then guide these companies to reach monopoly or a cozy cartel in their area of expertise, due to sheer money you are investing into them (since the goal isn't making a profit but blowing competition out of businness).

Sounds strange, but I'm ready to bet it is more cost-effective than landing 500 million shock troopers or placing orbital doomsday platforms.
After all you can always get populations that refuse to surrender, but economy is economy, money must flow.

Some rumours say that what caused it to drop was sabotage, but there are no proofs. The structure being more than three thousand years old, it could have been just a terrible incident.

Having a so big rock that anyone can redirect in a moment and not guarding it does not sound smart thing to do.

Hell, we keep guarded long-dead satellites now.

Even then, it's still a great big chunk of metal falling from orbit at very high speed. And the Habitats before where far bigger than just 3-4 km : it was common for them to be larger than 10-15 km, some people even having created proto-ringworlds more than 100 km in diameter.

Unless it was designed to do so (and there would be little reson), it will likely break up into lots of not-so-ecosystem-threatening pieces that would carpet bomb a city or two, but not do much more than that.

Also, most habitats have a substantially low density since their interior is hollow to allow habitation. So to deal the same damage of a 100 km wide rock you need a colony much much bigger than that.

'kay, thanks. I'll look into it. But still then, the calculations involved are complex and take some time – maybe less than I predicted, but still it is non negligible.

Of course. I'm just pointing out a detail, just say the FTL requires calculations and you're ok.

I didn't want to imply that you could sense a ship passing by on an FTL-route ; what I say is that when inside of a solar system, if a ship pass by in FTL by roughly an AU, you can sense it with the proper equipment.

the light lag for 1 au is around 500 seconds or a bit more than eight minutes. In eight minutes the passing FTL ship travelled how much space?

Also, nitpick : the “past” is ever increasing, you know ?

yeah. Something like that.

The average lifespan in the Sphere is around 200-250 years, and there are a number of people who are functionally near-immortal.

Did you say this above?

Anyway, nitpicking the longer lifespans, how do you handle natality? because if every woman gives birth to say 50 individuals before dying that's a pretty damn huge population growth.
It probably requires just relative wellness for everyone and cheap condoms.
Just keep an eye on this.

the World-Crackers, these FTL-Powered engine of mass destruction, only one able to destroy a world without getting in range of the enemy defenses.

If you have really powerful engine tech like say engines that can keep thrusting at 1 gee for say 4 months can become a 30% c impactor, if it is thrusting for a full year that's around 77% c. Should not destroy a world, but sterilization is almost guaranteed.relativistic trips

[Guardsman Bass]

Dunno, the US has issues in trying to pacifying something the size and population of Afghanistan (with an afghanistan techlevel too), pulling off the same trick on an entire fucking world with 3-4 billion people on it (and possibly a better techlevel) sounds pretty hard to me.

The issue isn't winning the shooting contest, it's making sure they do what you want them to.

You just have to force a surrender without resorting to WMD-equivalents or damaging the planet, and you have the resources of multiple star systems to do it. After that, there's a whole range of governance options, some of which don't require more than token manpower on your part.

You are doing it wrong. You need to buy companies, not people. Then guide these companies to reach monopoly or a cozy cartel in their area of expertise, due to sheer money you are investing into them (since the goal isn't making a profit but blowing competition out of businness).

And if the targeted planet has limitations on foreign ownership, or predatory pricing? Most countries have those today, and if you start plowing a ton of money into a planet's economy deliberately to gain market share, you're going to end up under the eye of regulators.

[Number Theoretic]

Anyway, nitpicking the longer lifespans, how do you handle natality? because if every woman gives birth to say 50 individuals before dying that's a pretty damn huge population growth.
It probably requires just relative wellness for everyone and cheap condoms.
Just keep an eye on this.

Depends on the actual fertility of the women, which again is a cultural thing. If they are born and raised in crampy space habitats where allocation of resources and therefore birth control is a big deal, they could still end up with giving birth to 2 individuals or less in their entire life. And in certain european countries we have a low fertility rate even today, without strict resource limitations. Because of widely available contraception and the perception that children put you at risk of sliding into poverty.

[someone_else]

You just have to force a surrender without resorting to WMD-equivalents or damaging the planet, and you have the resources of multiple star systems to do it. After that, there's a whole range of governance options, some of which don't require more than token manpower on your part.

Which is why they are hard to root out. They know that you don't want to hurt the planet, so they can use its features as a gigantic meatshield and refuse to comply with your requests.

Placing orbital bombardment platforms is idiotic if both you and the enemy knows that you'll never use them. what if they say "screw you, we are gonna retreat into those cool rainforests where we can live with what Mother Nature gives us and smoke pot all day and make group sex" ? You bomb the whole rainforest?

For a slightly smarter violent way, then I don't see the issue of simply landing 5-6 billions of shock troopers with gazillions of armored divisions and artillery anywhere you want to capture, zerg the hell outta them and load people in prison ships to relocate them somewhere else. After all you aren't really dealing a lot of damage to the environment with conventional weapons. It would be hard with modern nukes as well, but that's not what most people believe.

Anyway, the main reason for deportation is that I doubt they will like you for a long time if you get there, take their shit and say "I take control of this world" or "we bring freedom", and that's an issue difficult to solve if you need them to work for you and not stab in the back your colonists. Genocide is bad for PR but moving around people isn't so bad. And staying there until they eventually like you isn't cheap (Afghanistan, Iraq).

And if the targeted planet has limitations on foreign ownership, or predatory pricing? Most countries have those today, and if you start plowing a ton of money into a planet's economy deliberately to gain market share, you're going to end up under the eye of regulators.

Of course you'll create companies named "I-WANNA-TAKE-OVER-THIS-WORLD" with their main offices based on your own homeworld.
You'll have to start using multiple locals you keep under constant threat to say they are owners of said industries. And transfer money to the future equivalent of Swiss Bank accounts. Or do some Space Finance Tricks which are done today to transfer money around without major hassles. (hint: if you want to keep this from happening you need to have an organization that keeps financial stuff in check)

And you don't need outright predatory pricing, either a reasonably cheaper price with massive ads campaigns or massive investments in R&D (none will question the R&D or ads money) that put the companies a step above everyone else. The point is that now those companies don't need to pay everything they do with their profits, so they can grow pretty damn faster than anyone else.

The postive part of this method is that people will not see you as a conqueror, but as a trade partner, and in most cases the common person won't even know their nation is dominated by you.
The official government will simply be pressured by some of your industries to do what you want when you need it (one of the first thing would be opening up preferential trade channels with your worlds), otherwise they are free to do what they please. But for them there is no way to escape from your grip without declaring communist revolution and going Soviet Russia.

It is called economic domination, and is what is still active on most african nations.
The US is a bit too nostalgic of military domination though.