Idea for FTL

[VarrusTheEthical]

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?

Short answer: no. Long Answer: I'm not interested in writing about immortal transhuman stargods.

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.

Relativistic weapons come to mind.

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.

FTL of any kind is beyond our ability to empirically test, IMO. Now I know that my setting's FTL works is a pet peeve of yours. However, it works in providing me with exactly the kind of universe that I want. Most science fiction stories, good one even, tend to make impossible assumptions in order to tell interesting stories. This is my impossible assumption and I'm sticking with it.

[Batman]

If FTL were actually possible, it would be pathetically easy to empirically test. Jump out a lighthour, send a radio signal, jump back. If the signal arrives after you do, you went FTL. It's as simple as that.

[VarrusTheEthical]

If FTL were actually possible, it would be pathetically easy to empirically test. Jump out a lighthour, send a radio signal, jump back. If the signal arrives after you do, you went FTL. It's as simple as that.

Good point.

[VarrusTheEthical]

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.

What, specifically, did you have in mind?

What I'm getting at is a personal agenda of mine, but the solar system is big. If the trip to another star takes a mere few weeks, you can get that just by using lower level engines and doing Earth and Mars or Jupiter or whatever.

I guess the biggest difference would be communication. A week lag is different than hours lag, which is probably as bad as it will get inside the solar system. But it isn't too far different; real time isn't happening either way.

But I like the solar system.

[/quote]

The Solar system is a great place, don't get me wrong, but a solar system setting is not quite the aesthetic I want.

By having an interstellar setting, I get to use real star systems as the backdrops for my stories. Imagine for example, space pirates hiding in the colossal proto-planetary disk of Formalhaut and the difficulties any space navy would have in rooting them out.

In terms of communications there are a few big differences between hours lag and weeks lag. For one, wars can be fought for months after peace treaties is signed. A fugitive could outrun the ship carrying news of his wanted status. You could could have the leader of an interstellar government based in the Solar System completely ignorant of the 2000 ship strong invasion fleet that's overwhelming the defenders of the Alpha Centauri system.

So to put it simply, I want a scale that's larger than a Solar system setting like Exosquad or Jovian chronicles, but smaller than other interstellar settings like Star Trek or Babylon 5.

[Ariphaos]

Short answer: no. Long Answer: I'm not interested in writing about immortal transhuman stargods.

You don't need immortality, but a projected lifespan of ~2-3 centuries isn't out of the question even without advanced genetic engineering.

Relativistic weapons come to mind.

Relativistic weapons are no match for sunshine and happiness. They are slow, inefficient, far easier to detect, and have no ability to seriously damage statite swarms. And until WH40k/Star Wars levels, there isn't such a thing as a fleet that can put out a significant fraction of a star's firepower.

FTL of any kind is beyond our ability to empirically test, IMO. Now I know that my setting's FTL works is a pet peeve of yours. However, it works in providing me with exactly the kind of universe that I want. Most science fiction stories, good one even, tend to make impossible assumptions in order to tell interesting stories. This is my impossible assumption and I'm sticking with it.

You asked what people thought. I replied.

Personally, I don't believe impossible situations are required for telling most stories.

[Ariphaos]

By having an interstellar setting, I get to use real star systems as the backdrops for my stories. Imagine for example, space pirates hiding in the colossal proto-planetary disk of Formalhaut and the difficulties any space navy would have in rooting them out.

Saturn's rings are denser, and serve better.

For one, wars can be fought for months after peace treaties is signed.

You could could have the leader of an interstellar government based in the Solar System completely ignorant of the 2000 ship strong invasion fleet that's overwhelming the defenders of the Alpha Centauri system.

When I read that, the first thing I wonder is "Why is any invasion force less than fifteen digits in number a threat to Alpha Centauri?"

So to put it simply, I want a scale that's larger than a Solar system setting like Exosquad or Jovian chronicles, but smaller than other interstellar settings like Star Trek or Babylon 5.

Adding star systems and FTL does not automatically make your scale bigger. You're just dragging Alpha Centauri and friends into your back yard and playing 19th century naval conflicts in space, with similar numbers of ships, telling similar stories and presenting similar problems, giving them similar situations to deal with. Fugitives can outrun the British Navy's ability to carry messages of their status. The British Navy fights battles after treaties are signed. Wars can be joined and well underway before the British Navy is aware of them. There are certainly people interested in those stories.

But I don't get the feeling you're not presenting space as space. Space seems to be a fancy term for 'giant ocean', and star systems are suddenly islands to be fought over with no real consideration given to the vast resources they harbor.

[Darth Hoth]

When I read that, the first thing I wonder is "Why is any invasion force less than fifteen digits in number a threat to Alpha Centauri?"

Because the guy is writing military sci-fi, not "hard" science fiction with Dyson spheres, massive space infrastructure and harnessing of huge portions of the star's luminosity for military purposes. When he says "relatively hard" he means "hard" as in Honor Harrington vs Star Trek, not the kind of setting junghalli or Destructionator (among others) frequently advertise. Or at least, that is how I understand it from his posts.

Although, note to Varrus: Have you thought through the energy implications of your ships? Assuming one per cent of your 10-million-ton battleship's mass is made of exotic substances converted directly from energy to matter, that means you have invested (at the very least, assuming unrealistically small inefficiencies in conversion) roughly some e25-26 joules of energy in the construction of that one ship. If you build hundreds of these, the scale of your industry means that the civilisation would more or less have to use up rather large portions of a given star's total luminosity. Which does probably mean Dyson spheres, especially as the energy collection will not be almost-completely efficient without magic, either.

But I don't get the feeling you're not presenting space as space. Space seems to be a fancy term for 'giant ocean', and star systems are suddenly islands to be fought over with no real consideration given to the vast resources they harbor.

I actually agree with you "hard-scifi" people that most space opera settings dramatically underutilise the resources of their holdings. (One day, it might be fun to write about a "galactic empire" that is also a true Kardashev-III, and does not merely claim billions of stars while being essentially Star Trek otherwise.) However, it does indisputably contribute to scale if stars and interstellar distances are used, instead of a solar system. Solar systems feel small to people used to less than "hard" science fiction. For all that they are incredibly vast spaces otherwise.

***

To Varrus: From what I understand, you already have a somewhat firm image of the setting you want. In that case, fine; I personally tend to like "soft"/space opera sci-fi settings better than "hard" stuff (although there is good hard sci-fi, of course, only it is rare), and you should go with what you like. However, you might still find much useful in this thread; even if you choose not to adopt changes or explanations proposed here, just thinking about it will without fail improve your conception of your story.

[Ariphaos]

Wow, grammatical fail on my part, "But I don't get the feeling you're not" should be missing a don't or a not, there.

I don't think having dyson swarms preclude conflict, but at low tech levels they need a lot of clever thinking around or the nature of the conflict is different. At mid tech levels (Star Wars, WH40k) they represent a major strategic asset to the defender that must be accounted for. At high tech levels (Culture, etc) they're an eyesore if their primary purpose is power generation, but conflict in that sort of setting occurs at barely-comprehensible scales.

[VarrusTheEthical]

To Varrus: From what I understand, you already have a somewhat firm image of the setting you want. In that case, fine; I personally tend to like "soft"/space opera sci-fi settings better than "hard" stuff (although there is good hard sci-fi, of course, only it is rare), and you should go with what you like. However, you might still find much useful in this thread; even if you choose not to adopt changes or explanations proposed here, just thinking about it will without fail improve your conception of your story.

Oh, I have been thinking about what people have been saying. The stutter idea that was proposed was great, especially if I try similar FTL with much higher speeds. Also, after you pointed out the energy cost cost of building FTL drives as I have presented them, I will be going back and readjusting the values. I probably dropped a zero or ten when calculating the cost of an FTL drive. Perhaps I'll just lower the ratio of exotic stuff to normal matter within the drives themselves while keeping the drives the same size. I want starships to be expensive, but I don't want the FTL drives to be more than ~100% the cost of the rest of the ship it's self.

I will point out that a 10 megaton warship is about the mass of a fully loaded high-end capital ship. Most warships are much smaller. 100,000-500,000 for light and heavy cruisers, 30,000-50,000 tons for destroyers.

Also, let me cover myself a bit. When I said relatively hard, I mean relatively hard compared to Star Wars, Star Trek, or Babylon 5. There's no artificial gravity, shields, or FTL sensors. I was kind of aiming for Mote in God's eye level of hardness, with the exception of no Langston fields and a preference for KE over lasers. So sorry if I raised people's hackles with that one.

I am open to people's advice. As long as that advice is more than just "My solar powered deathstars trump all, Kardeshev II ROX!!!!". I don't mind suggestions to go with a solar system only setting, plenty for good science fiction of varying levels of hardness take place in only one star system. It's just not quite the scale that I want for a setting.

[Whiskey144]

I will point out that a 10 megaton warship is about the mass of a fully loaded high-end capital ship. Most warships are much smaller. 100,000-500,000 for light and heavy cruisers, 30,000-50,000 tons for destroyers.

I'm going to gently point out that, if you have, say, a fairly modest/easily realizable exhaust velocity of 200 km/s, an ~3,000 tonne ship that accelerates at 0.1 Gs has a nearly 600 gigawatt thrust plume.

This is just roughly guessing by order-'o'-magnitude, but that goes up to 60,000 gigawatts, for one of your 30,000 tonne destroyers, supposing it does a 1 G acceleration for its entire flight profile. The continuous thrust profile isn't too bad, as it makes sense given the FTL drive restrictions.

There's only one problem- that 60,000 gigawatts is just slightly less than the Hiroshima bomb. Every second.

Yeaaaaah. So you have a minor caveat in that your propulsion systems are quite possibly far superior weapon systems compared to your slugthrowers- considering they are the almost-literal equivalent of a tactical nuclear weapon.

I say this because I've had to face the same issue in my own setting- though I'd say that you'd have a much easier time getting around this considering, once again, the FTL drive restrictions you have. Though that invasion fleet heading for Alpha Centauri is most certainly not going to be in a particularly close formation.

[VarrusTheEthical]

@Whiskey.

That's actually part of the fun for me. Yes, the drives are by far the most powerful weapon that any ship carries, it's just rare for star ships to get close enough to try and burn each other with them. While a 30,000 ton destroyer could destroy a 10,000,000 ton battleship with it's drive, that destroyer would likely be smashed to bits by the battleship's guns before it got close enough. Another problem is that you cant really armor the drives, so you run the risk of exposing you most vulnerable part of your ship to enemy fire. Also, for large ships, it's going to take awhile to turn and point your drive at the enemy. Really, the best use for the drives as weapons, in my mind, is for glassing over the surface of planets. Kinda like what the Empire of Man in The Mote in God's eye did to rebellious worlds.

And as for formations, I think the important thing is to make sure that no ship is directly behind another while moving in formation. I'd imagine star ship formations looking more aerial formations, such as line-abreast or a wedge, rather than the traditional naval line formation. Which factors into my star ship design, firepower is concentrated towards the front.

[StarSword]

On formations: I was thinking along the lines of an Honorverse "wall of battle". Basically an outgrowth of a wet-navy battleship "line of battle", but in three dimensions.

[VarrusTheEthical]

On formations: I was thinking along the lines of an Honorverse "wall of battle". Basically an outgrowth of a wet-navy battleship "line of battle", but in three dimensio

Well Honorverse wall was also an outgrowth of that setting's ships armament being concentrated on the sides of the ships just like in the age of sail, as well ships being invulnerable from the top and bottom due to their wedges. My ships concentrate their weapons and armor in the front. The logic being that it it allows for the greatest amount of firepower concentrated in the smallest surface area.

The loose net setup is shaped like a sparse sphere of your ships. The idea is to ensure a group of your ships can hit the other guys individuals ships from just about any angle simultaneously. Thus, he must armor his entire ship - if he just carries a forward shield kind of thing, your buddy will shoot him in the side.

A good idea, but I wonder if such a loose formation would be vulnerable to being attacked in detail by more concentrated formations of warships. Or by missile or bomber attacks from standoff range? Would the ships be close enough to have overlapping coverage by point defenses?

[VarrusTheEthical]

I like big ships, I cannot lie.

In my setting, the typical capital ship is almost always over a million tons. Battlecruisers, which are typically 1-2 million tons and have battleship level firepower but cruiser level acceleration (~3gs) and armor. They are not really meant for fleet battles, but as independent commerce raiders or heavy escorts.

Battleships are between 3-to-15 million tons. They are usually limited to about 1g acceleration under full load, but their hulls are rarely stressed for more than 1.5 or 2gs. They have the heaviest firepower, thickest armor, and most potent point defenses.

Related to battleships are monitors, which are battleships that lack FTL. They're popular in systems that want battleship level firepower without the cost of adding FTL capability. The cost and weight savings can further be put into better weapons and armor.

Carriers are generally the same size, weight, and performance as battleships, but sacrifice armor and firepower to carry a few hundred combat smallcraft.

Fighters and bombers, which are about 150 tons, have the same Delta V as larger vessels, but are capable of 10+ G of acceleration for extended periods of time. I assume a combination of physical augmentation and the use of exoskeletons with interior gel layers to allow pilots to tolerate those conditions. Fighters are general purpose combat smallcraft, while bomber are specifically designed for attacking large capitalships.

Cruisers (100,000-to-500,000 tons) and destroyers (30,000-to-50,000 tons) exist, and the bulk of any fleet is going to be made up of these smaller vessels. In fleet battles, they basically help augment the point defenses of battleships. Outside of that they are needed for controlling space. Either regulating space traffic in friendly systems, or chasing down blockade runners in hostile ones.

Frigates, which are about 10,000 tons, also exist, but in specialist roles. For example, an escort frigate would basically be a smaller destroyer used for commerce protection and nothing else, while a missile frigate would serve to augment a fleet's firepower during missile duels, but would bug out once the range closed or their ammo was exhausted.

[VarrusTheEthical]

Space fortresses do exist in my setting, I just call them planets. From the point of view of an invading fleet, a planet is a gigantic carrier and missile battery. You could have tens of thousands of missile bases buried into the planet's mountains, and on wet ships or submarines in the oceans. Since my missiles use the same drives as starships, they have the range to pelt a fleet from a distance. And they would never run out of missiles because they could just build more. The main issue would be fueling them. The planet can also sortie fighters against the enemy, attacking either the fleet itself or it's supply line, since fighters have the range an endurance to go pretty far.

It is a massive undertaking overwhelm a well defended, industrialized planet. Usually when a fleet invades a system, it's not to do anything to the planet itself, but to establish local space superiority and the destroy as much space based industry as possible. Solar power statites, space factories, ship yards, orbital gas mining. Basically the objective being to destroy the system's ability to project interstellar power, rather than conquest itself.

Now since I'm a space fighter fanboy, in my setting I think the way they would deal with a space fortress is to use a massed fighter and bomber attack. The objective would be to try and disable the largest weapons with saturation nuclear strikes by the bombers. The fighters would work to try and suppress the point defenses of the starfortress, as well as any fighter screen it may have. Once enough of the fortress' firepower has been disabled, I would move in my battleships, using their main KE weapons to bombard the asteroid as they approach. Once I get a few battleships close enough, and felt that the starfortress' defenses were weak enough, I would have the battleships turn their drives on the starfortress, roasting it until the surface melts.

[Number Theoretic]

Another argument in favor for space fortresses is waste heat managment: the whole asteroid can be used as a heatsink, which allows you to install and operate waay more terawatt-range lasers than any battleship could afford. Because of the much bigger heatsink, it can fire the same number of lasers as a battlefleet for a longer time, before heat needs to be radiated away. And of course it can easily fire as many missiles as the whole battelfleet.

The only thing, that can be a real danger to space fortresses - well, apart from a really big invading fleet - could be a relativistic kill vehicle that flies insanely close to the speed of light. Calculating the necessary fraction of c to escape a given reaction time is left as an exercise for the reader but in theory, it could work: you only know that a laser hits you when it's too late. Which can be approximated, given that the energy necessary to shatter an asteroid is extremely high. Put into kinetic energy, the resulting kill vehicle can be unstoppable, given that the fortress does not expect the
assault from a certain direction. Becaue then, it can be averted by the interceptor drones mentioned by Destructionator.

[Purple]

Hm... a hypothetical question. How much do these missiles of yours accelerate? And what's their mass? I mean, I can't see it being pretty for the environment when millions of rockets all fire at once no mater what drive you are using.

[VarrusTheEthical]

@ Purple

Well, say the missiles are about the the size of a Delta IV rocket. 60m tall, 5m diameter. I would assume a chem rockets for the first stage to get the rocket safely out of the atmosphere before lighting its fusion drive. As for fusion drives, aneutronic reactions such as He3-deuterum would be preferable, but a dirty deuterium rocket would also work in a pinch. And to be fair, I doubt even a million rockets would be as bad for the atmosphere than say, cool-fired power plants. At least as long as you don't use the nuclear drive in the atmosphere.

I'd imagine a the fusion drive would be throttle able. If you're target is far away, 1g acceleration should be sufficient. If you keep that acceleration constant, it would be less than two hours before you crossed lunar orbit. On terminal approach, or if the enemy close at launch, start moving at up to 20-30 gs? Perhaps it could be a 3 stage missile, first stage is a chem booster, second stage is a 1g "cruising" stage, and then a third stat 20-30g terminal stage?

At the velocities such a missile could reach, you may be better served by using kinetic kill vehicles rather than nukes.

[Number Theoretic]

How about a shaped charge nuke? Your missile might then need to aim in the right direction for the shaped charge to be effective, but it reduces the danger, that your nuke gets shot down by PD before it can get into effective range.

[VarrusTheEthical]

Shaped charge nukes are the norm of my setting. The primary munition for a space bomber, for example, is a freefall space bomb with a shaped charge. A squadron of 12 bombers can drop a little less than a 150 warheads in an expanding cone, that a sluggish vessel like a battleship typically will not be able to escape. Further, because the bombs are completely passive and covered in radar absorbent materials, they would be harder for PD to detect, track, and destroy.

[VarrusTheEthical]

Note: battleships were actually pretty fast, historically. There's a lot of the same scaling factors that apply to space too - there's really no reason that a battleship needs to be slow, and there are reasons it can do better than smaller ships.

Well its not that Battleships are slow, they just don't have great acceleration and cant change their vector very fast. The logic is that with battleships, the emphasis is on the heaviest armament and armor possible at the expense of performance. One G of acceleration is considered enough because it will get you where you need to go pretty quickly and provide comfortable gravity for the crew. If you want to have a ship that's quicker on it's feet, your going to need to sacrifice either guns or armor. Which is essentially what a battle cruiser is.

Also, since battleships are the biggest warships, you're going to run into problems with scaler laws. The largest battleships are already going to be pushing the limit of my setting's material science. You have to remember that if a 10 megaton starship is accelerating at 1g, that means there's 10 million tons resting on the engines. So if you try to push the ship to higher accelerations, then run the risk of essentially having the whole ship collapse on itself. Since fighters and bomber are only about 150 tons, they can get away with 10g+ without the same issues as larger ships.

Also, the reason I need carriers is because space fighters and bombers are too small for FTL drives. In normal space, fighters have almost indefinite endurance. The pilot can be kept in hibernation during any downtime, only to be awoken during combat.

Though to be honest, I want Space Fighters because they are really cool.

[VarrusTheEthical]

In regards to space fortresses, I think that a planet has all the advantages of an asteroid based fortress, but on a far larger scale. And the atmosphere of a planets is more of an advantage than a liability to me. It's an added layer of protection against both lasers and kinetic weapons, and will help hide your land, sea, and air forces. As for sensor issues, that can be mitigated by the use of satellites, or even high flying aircraft. And if the enemy shoots down your sats? Build new ones and launch them into space with cheap chem rockets.