Ships sizes. When is big too big?

[gigabytelord]

Someone on DeviantArt Compiled a fairly interesting list of spaceships from a huge number of different Sci-Fi universes, And while looking at it an interesting question popped into my head.

Linkage

When is big too big? I mean take a look at that list and it seems as though everyone is in a race to write the biggest ship into existence. As a wannabe Sci-fi writer myself I sometimes wonder just how far can you plausibly go before things start to get absurd.

On the other end of the spectrum is it even an issue at all? Does it even matter as long as the story itself is worth reading?
Just looking for opinions.

[Grandmaster Jogurt]

In a visual medium, one thing that's important is some sort of sense that the size matches the appearance. Several of the ships on there, especially from 40k and EVE, are absolutely huge but look like ships that should be much smaller, like a tenth of the length, and this detracts from the whole thing. It lessens the sense of scale and takes you out of the picture for a moment. Or maybe that's just me?

One thing that's probably inarguably bad as an example is the Dominion ships seen there where you have one 1.5km long and one 4.5km long... and they look identical. It's something that's very obvious and easy to point out but it's the same situation as before.

In a purely textual medium, it's probably a lot easier to not worry about little details like that. In all situations it's a case where "if what you're trying to tell us is good that's what matters", but there's fewer options to make things niggle I guess.

[FTeik]

As long as you stay within the context of your story and the vessel you describe needs the size for what it is supposed to do I see no problem.

For example the DS with a diameter of 160 km works, because it is supposed to destroy a planet with one shot and be a mobile fleet and its base in one hull.

However I would draw the line for battlestations of doom or intergalactic colony-ships at 1,000 kilometers for reasons of practicality and spatial sense. Anything larger should be relatively stationary. And you also have to make sure, that the surface-structures reflect the size. Visible weapons-turrets or sensor-domes on a structure of hundred kilometers or larger can be problematic.

[Jerry the Vampire]

Of course it gets absurd when you have ships that would affect the climate below due to their gravitational pull.

[Batman]

I'm don't think there is an arbitrary line on what is and isn't too big. Wars Executors are perfectly fine for Wars, seriously out of line for the Trek AQ powers or B5's younger races, a 'weird shape for a starship' for a lot of the Perryverse and possibly a 'why is this ship so tiny' for the Culture. As has been said before, it all depends on context. If the cultures in your story habitually build Dyson spheres as a way of colonizing a new star system bigass starships are going to be a lot less of a problem than they'd be if, say, your protagonists are on their very first foray out of their home system and only developed FTL a few years ago and are still in the process of colonizing/utilizing their home system lesve alone have magitech like artificial gravity or shields.

[Formless]

Too big? To start with, I think we can agree that once a ship starts to have significant gravitational pull on planetary bodies, generally it should no longer be called a ship. There is no proper term in existence yet for what that is.

That doesn't mean that such "ships" are a no go area for sci-fi. Gurren Lagann has mecha the size of galaxies and I hear its great fun.

[Simon_Jester]

Amusingly, the very first "giant mobile battlestation" I am aware of, the Skylark of Valeron from Doc Smith, was a thousand miles across, hopped galaxies casually, besieged entire interstellar empires in battles fought across galaxy-sized distances, and could be controlled by one man sitting in a control chair with a direct neural interface to the Skylark's mechanisms and central computer... originally published in 1934.

Ah, the Golden Age.

Anyway, more seriously, general guidelines:

1). The physical size of ships should be in keeping with the physical size of a culture's civil engineering undertakings.

In any given era of history, the largest ships have been build on roughly the same scale as the largest buildings which could be constructed for practical engineering purposes, as distinct from self-consciously monumental architecture. If the largest immobile structures in your setting are space stations a mile long, it is highly unlikely that anyone could build a mobile platform a mile long and fire up the engines without bits falling off. Which, come to think of it, leads to...

2) The physical size of ships should scale roughly with the energies and material technologies of the society that made it

There is a reason no one ever made ten thousand ton ships in the Age of Sail- wood isn't strong enough. A ship of such length and weight will flex so much that parts of it start to break up. Steel is stronger, but there are still limits. One obvious benchmark is that a ship must be able to support its own weight. A starship the size of a skyscraper, with an engine that propels it with an acceleration of one gravity, would need roughly the same kind of structural bracing a skyscraper uses to hold up under one gravity, or its own engines will compress it into a pancake. Increase the acceleration and the problem becomes more serious.

Build the ship ten miles long out of atomic-age materials technology, and give it engines powerful enough to accelerate it at one gravity, and... well, bits will probably start to fall off, because the engines are so powerful it might be impossible to build a framework strong enough to hold them in place. The engines fire up and promptly begin pushing themselves straight through the hull, smashing and burning everything in their path.

[I have done no precise calculations; I simply want to illustrate the issue]

Force fields that exert uniform force on all parts of the ship (i.e. artificial gravity) can sidestep this problem. But as a rule, if your technology involves forces being exerted on the ship, it needs a structural framework capable of withstanding those forces. Likewise it might be a serious problem generating the forces required to make the necessary movements- consider that to move a spacecraft of several thousand tons, and accelerate it at one gravity or better, people have seriously considered exploding nuclear bombs, at a rate of roughly one per second, as a propulsion mechanism.

Giving a billion ton ship (volume probably a cubic kilometer or less) similar acceleration would probably involve something a lot more drastic and energetic than exploding nuclear bombs. Do you feel like this is in keeping with your society's capabilities?

3) Thematically, ships should have a size which matches well with their purpose in the story.

Ships used by individuals for transportation will be much smaller than bulk cargo haulers. Dedicated warships will probably range somewhere in between the two (unless your society's need for killing exceeds its need for cargo transportation).

Personal 'shuttles' or whatever you call them have several reasons to be small. It's not just that the ship's living quarters will be scaled to what one person needs for comfort. It's that if they're built to gigantic scale, it becomes impractical for an individual being to move about the ship and see to its functioning.

A very large personal transport also needs an extreme amount of space to take off and land (or dock), which makes it less flexible: something the size of a helicopter can take off from the roof of a building, but a helicopter the size of an ocean liner would basically have to land at a very large airport with a very large tarmac.

On the other hand, a freighter needs to be large enough to carry the cargoes it's realistically expected to move; if you look at the way the Millenium Falcon is portrayed, there's no way Han could fit more than a few dozen tons of cargo aboard because there's no place to put it. Which, given that he's in a fast blockade runner, is probably all right. Serenity from the show Firefly has a real, serious cargo bay capable of holding a herd of cattle or other reasonably large volume of goods, by contrast... but is correspondingly larger and is clearly designed around its own cargo bay.

[gigabytelord]

Interesting answers. This wasn't a question so much for my story directly I suppose just about the plausibility of really large ships in general. I've always had the idea that you don't need to build 12km or 30km long ships to be able to achieve certain goals. Particularly for warships, in fact I've always had the idea that right around 2km was the perfect length for most larger warships and my own work tends to reflects this, obviously there will be exceptions in the cases of industrial and commercial ships and the like or even supercarrier equivalent vessels.
Maybe it's just that I don't see the point in going much larger in most instances.

I love discussions on the topic regardless.

Ninja edit: Simon give me a little while to respond to you, as I'm a terribly slow poster :p

[Batman]

There is no such thing as the general plausibility of huge starships. The questions are a) does your setup have the technology to build those ships to begin with and b) are they likely to build them even if that is the case. A lot depends on how the underlying technology scales and what the limits of it are, and let's not forget the question of whether or not they actually need those big honking megawarships.
Technological limitations or not, your navy isn't going to be allowed to spend all that much money on battleships and up if all they ever actually DO is commerce protection.

And I'd really like to know how you arrived at the conclusion that 2km is the perfect length given that again, the size of your warships is going to be heavily dependent on what your technology can do withing a given spaceframe and the kind of spaceframe you need to allow the technology available to you to do what you expect to be your warship's job.

[gigabytelord]

There is no such thing as the general plausibility of huge starships. The questions are a) does your setup have the technology to build those ships to begin with and b) are they likely to build them even if that is the case. A lot depends on how the underlying technology scales and what the limits of it are, and let's not forget the question of whether or not they actually need those big honking megawarships.

Just a quick answer. Yes in this setting the powers that be generally do have the technical capabilities to build big honking warships but generally don't. In fact it's common to see massive space borne refineries, colony ships, transports and the like.
However, military vessels rarely exceed the unspoken in universe 2-3km in length rule, and the vast majority of warships are much shorter than that. I suppose that I have setup some sort of mental block that I'll have to get around. Basically the navies of the day prefer to out number rather than have

Technological limitations or not, your navy isn't going to be allowed to spend all that much money on battleships and up if all they ever actually DO is commerce protection.

And I'd really like to know how you arrived at the conclusion that 2km is the perfect length given that again, the size of your warships is going to be heavily dependent on what your technology can do within a given spaceframe and the kind of spaceframe you need to allow the technology available to you to do what you expect to be your warship's job.

I suppose I didn't imply it properly. There's a word I'm trying to think of to describe it. Damn it, it's right on the tip of my tongue!
Basically I'm aware that it's irrelevant but 2km seems to be the best length to balance internal transport systems, storage, armament and armor. Sometimes I've noticed that some writers don't make any attempt to address one very large issue that comes into play when you have massive ships of any kind. How do you move the damned crew around quickly? Yes with non-military ships this is less of an issue but on a warship you may have to get from point A to point B quickly. Most people will say but that's not really an issue just install elevators and internal transport. Ok, but what if the power goes out and now your repair crews have to make a 30km trip on foot? while in the middle of battle? It just bothers me on certain level and I realize that it's not really important, but it's just one of those little nagging things you know?

Hence the reason for me starting this thread. I wanted to see what others would have to say regard some of the less thought about issue regarding large ships.

[Forgothrax]

A sufficiently sizable ship would probably be decentralized to a degree to avoid problems like you're suggesting. However, any civilization sufficiently advanced to build a ship 30km in size is probably sufficiently advanced to automate a lot of crew functions, if not most of them.

[Simon_Jester]

Interesting answers. This wasn't a question so much for my story directly I suppose just about the plausibility of really large ships in general. I've always had the idea that you don't need to build 12km or 30km long ships to be able to achieve certain goals. Particularly for warships, in fact I've always had the idea that right around 2km was the perfect length for most larger warships and my own work tends to reflects this, obviously there will be exceptions in the cases of industrial and commercial ships and the like or even supercarrier equivalent vessels.

Several points:

For industrial, commercial, and military contexts, a ship is designed to fit a mission. Think about the mission first, the stuff going through the builder's mind before he draws up the blueprints, and you'll often get some information about the size.

For example, suppose a ship is designed as a dedicated passenger liner. How many people is it intended to carry? If you want an experience like that of a real life ocean liner, the answer should be limited to "a few thousand."

If you have tens or hundreds of thousands of passengers on the manifest, you can still tell interesting stories, but you're faced with the reality that there must be several layers of bureaucracy between the average passenger and, say, the captain or chief engineer of the ship. Think about how much effort or emergency it takes an ordinary citizen to get in to see the mayor of a large city, and you'll have an appreciation for the scope of the issue. You also have to confront points like the fact that if you pick two passengers at random they have almost certainly never met each other, at any given time on the voyage. Even if you've been underway for weeks, odds are you still won't recognize 95-99% of the passengers by sight.

But if the ship only carries a few thousand people... the living quarters won't be much bigger than a real ocean liner, unless the liner's service includes "give everyone as much space as a penthouse apartment." Life support and machinery spaces and fuel tankage will add more volume, but you're still talking about a ship that is built to roughly the same scale as a modern skyscraper, unless those extra machinery things take up a LOT of space, like several times as much as the passenger accomodations.


Similar calculations apply to a freighter. I often wonder exactly what those six million ton bulk freighters in the Honorverse carry, which can be profitably carted over interstellar distances, in that kind of volume. It gets even worse with multi-kilometer freighters, unless you have massive megalopolis-worlds or habitats with populations in the trillions whose demand for physical goods is that large.


For warships, the main reason to think about this is if:

1) You have some kind of well-defined scaling that starts with the size of a small object (a missile or fighter, say) and runs up to big battlewagons. For example, in the last SF universe I thought about seriously, I had a pretty clear picture of how big an antiship torpedo was (roughly the size of an ICBM), and certain ships of mine had their overall bulk and design dictated by the need to be able to physically carry two of the beasts.

2) Your ship carries a well-defined contingent of things that have a known size, such as X-Wings, tanks, or soldiers. That maps back to the issues with freighters and passenger ships.

3) Plotwise, you find yourself forced to ask why it wouldn't be more cost-effective to just fill a Ship of Unusual Size (whatever is 'big' in your universe) with [whatever is needed] and throw it at the enemy. For example, why bother finding a magic MacGuffin weapon to blow up a planet, when you could load down a billion ton freighter with several hundred million tons of H-bombs (theoretical explosive yield limit of several kilotons per kilogram) and carpet-bomb the planet into a sea of fire?

Basically I'm aware that it's irrelevant but 2km seems to be the best length to balance internal transport systems, storage, armament and armor. Sometimes I've noticed that some writers don't make any attempt to address one very large issue that comes into play when you have massive ships of any kind. How do you move the damned crew around quickly? Yes with non-military ships this is less of an issue but on a warship you may have to get from point A to point B quickly. Most people will say but that's not really an issue just install elevators and internal transport. Ok, but what if the power goes out and now your repair crews have to make a 30km trip on foot? while in the middle of battle? It just bothers me on certain level and I realize that it's not really important, but it's just one of those little nagging things you know.

I understand, and it shows a healthy attention to detail.

Also, thinking about this detail yields interesting results in the context of a case where the ship really NEEDS to be that large (i.e. the Death Star, where the huge size of the battlestation is mandated by the huge size of the weapon it's designed to carry). Crew accomodations would necessarily be decentralized, and people assigned to one 'block' of the ship might never even meet people from another 'block.'

Also, bear in mind that the huge volume of the ship will also lead to designers building stupidly massive redundancies into the hull- if the ship has to be a kilometer wide, there is no good reason to have only one personnel transfer tube running along the spine of the ship, when you could construct dozens of them running in parallel. In real life ships are quite volume-limited. If you're building a death star, or a ship that has to find things to put into a 2 km wide hull that MUST be 30 km long because of its moon-busting spinal main weapon... you will see huge blocks of the ship filled with redundant systems and spare parts and so on which nobody ever uses.

Because having such things contributes to the fighting efficiency of the ship and prevents the massively expensive startup investment from becoming worthless due to a single case of bad luck.

[chornedsnorkack]

3) Thematically, ships should have a size which matches well with their purpose in the story.

Ships used by individuals for transportation will be much smaller than bulk cargo haulers. Dedicated warships will probably range somewhere in between the two (unless your society's need for killing exceeds its need for cargo transportation).

Or unless the benefits of scale are different. The battleships and carriers were appreciably bigger than Liberty ships. Not because USA did not have large needs for cargo transportation - they did, and accordingly launched 2700 Liberty ships of 14 000 tons each. Whereas the carriers and battleships were only a few tens total. USA had swarms of smaller cruisers as well. But a big carrier or battleship could do something that a swarm of smaller cruisers could not... whereas USA did not have any mission for a few big cargo ships.

Personal 'shuttles' or whatever you call them have several reasons to be small. It's not just that the ship's living quarters will be scaled to what one person needs for comfort. It's that if they're built to gigantic scale, it becomes impractical for an individual being to move about the ship and see to its functioning.

A farmhouse can be a tiny hovel - but the air is free out of the window. Feeding the resident and his family, however, may involve long walks to backbreaking work in outlying field plots, and possibly hunting trips with camping in the forests for several days. The size of an enclosed habitat to provide breathable air and good quality food for one family can be quite large - but would it ever repay the costs of building the enclosure out of artificial materials?

A very large personal transport also needs an extreme amount of space to take off and land (or dock), which makes it less flexible: something the size of a helicopter can take off from the roof of a building, but a helicopter the size of an ocean liner would basically have to land at a very large airport with a very large tarmac.

Or if it is amphibian, it may require a suitably large and deep body of water... with optional requirements on shelter from waves and currents.

For example, suppose a ship is designed as a dedicated passenger liner. How many people is it intended to carry? If you want an experience like that of a real life ocean liner, the answer should be limited to "a few thousand."

If you have tens or hundreds of thousands of passengers on the manifest, you can still tell interesting stories, but you're faced with the reality that there must be several layers of bureaucracy between the average passenger and, say, the captain or chief engineer of the ship. Think about how much effort or emergency it takes an ordinary citizen to get in to see the mayor of a large city, and you'll have an appreciation for the scope of the issue. You also have to confront points like the fact that if you pick two passengers at random they have almost certainly never met each other, at any given time on the voyage. Even if you've been underway for weeks, odds are you still won't recognize 95-99% of the passengers by sight.

There actually, positively were ships designed as dedicated passenger liners, which did have tens of thousands of passengers on the manifest. Queens Mary and Elizabeth were designed for about 2200 passengers.
They were converted to troopships - and although the crossing from USA to Europe still took several days, they managed to carry over 15 000 passengers. The record is in the name of Queen Mary, from December 1942, and stands at 16 082.

Similar calculations apply to a freighter. I often wonder exactly what those six million ton bulk freighters in the Honorverse carry, which can be profitably carted over interstellar distances, in that kind of volume. It gets even worse with multi-kilometer freighters, unless you have massive megalopolis-worlds or habitats with populations in the trillions whose demand for physical goods is that large.

US oil imports in 2012 are quoted at 10,6 million barrels per day - which is about 1,7 million cubic m per day, or 600 million cubic m per year. The biggest single supplier is Canada, so that could be overland, but Persian Gulf region is quoted at 2,1 million barrels per day, which is about 330 000 cubic m, or about 260 000 tons per day. You could fill the 6 million ton freighter in 23 days, which is in the same order of magnitude as the travel time Persian Gulf to USA.

There are technical reasons why the existing tankers are not actually 6 million tons, and the largest (of about 600 000 tons?) have actually been all scrapped. The biggest remaining tankers, TI class, carry about 440 000 tons.

Also remember that you do not need to have "trillions" in a single world. That is going to depend on the exact scaling of the ship technology. If you are trading between one end of galaxy and the other, you might have your physical goods reloaded to swarms of smaller ships which reach tens of thousands of nearby planets. So, how will your technology scale with range? Is a spaceship good to travel 500 light years appreciably different from a spaceship whose mission is 25 000 lightyears?

[gigabytelord]

Eh... Simon first then.

Several points:

For industrial, commercial, and military contexts, a ship is designed to fit a mission. Think about the mission first, the stuff going through the builder's mind before he draws up the blueprints, and you'll often get some information about the size.

For example, suppose a ship is designed as a dedicated passenger liner. How many people is it intended to carry? If you want an experience like that of a real life ocean liner, the answer should be limited to "a few thousand."

If you have tens or hundreds of thousands of passengers on the manifest, you can still tell interesting stories, but you're faced with the reality that there must be several layers of bureaucracy between the average passenger and, say, the captain or chief engineer of the ship. Think about how much effort or emergency it takes an ordinary citizen to get in to see the mayor of a large city, and you'll have an appreciation for the scope of the issue. You also have to confront points like the fact that if you pick two passengers at random they have almost certainly never met each other, at any given time on the voyage. Even if you've been underway for weeks, odds are you still won't recognize 95-99% of the passengers by sight.

But if the ship only carries a few thousand people... the living quarters won't be much bigger than a real ocean liner, unless the liner's service includes "give everyone as much space as a penthouse apartment." Life support and machinery spaces and fuel tankage will add more volume, but you're still talking about a ship that is built to roughly the same scale as a modern skyscraper, unless those extra machinery things take up a LOT of space, like several times as much as the passenger accomodations.


Similar calculations apply to a freighter. I often wonder exactly what those six million ton bulk freighters in the Honorverse carry, which can be profitably carted over interstellar distances, in that kind of volume. It gets even worse with multi-kilometer freighters, unless you have massive megalopolis-worlds or habitats with populations in the trillions whose demand for physical goods is that large.

I can't really answer some of these question without going into details which I'd rather not go into. However, The scale of the civilizations in this setting are both galactic and extragalactic. There are many hundreds of millions of inhabited worlds in this universe. The vast majority of which are artificially habitable, ie. large space stations, moons, barren worlds that either required extensive terraforming or need permanent climate control facilities in order to remain habitable. Few have populations which exceed a few tens of millions. This means that the vast majority of liners and general transports are comparatively small, there's just a crap load of them. Small meaning low single digit thousands. This can obviously change when one reaches the higher populated regions of the galaxy.

1) You have some kind of well-defined scaling that starts with the size of a small object (a missile or fighter, say) and runs up to big battlewagons. For example, in the last SF universe I thought about seriously, I had a pretty clear picture of how big an anti-ship torpedo was (roughly the size of an ICBM), and certain ships of mine had their overall bulk and design dictated by the need to be able to physically carry two of the beasts.

The setting doesn't really have torpedos per-say it does use massed produced combat drone systems which fill the same roles, (5-10 meters) and are equipped with various weapons systems for different foes.

2) Your ship carries a well-defined contingent of things that have a known size, such as X-Wings, tanks, or soldiers. That maps back to the issues with freighters and passenger ships.

3) Plotwise, you find yourself forced to ask why it wouldn't be more cost-effective to just fill a Ship of Unusual Size (whatever is 'big' in your universe) with [whatever is needed] and throw it at the enemy. For example, why bother finding a magic MacGuffin weapon to blow up a planet, when you could load down a billion ton freighter with several hundred million tons of H-bombs (theoretical explosive yield limit of several kilotons per kilogram) and carpet-bomb the planet into a sea of fire?

For the first, I'm not great at math and even if I was I wouldn't be able to calculate the proper measurements for many things in this setting because unlike Star Wars many of the things you listed aren't yet well-defined. They're getting there but while working on the story I really haven't seen fit to lay everything down just yet. The only reason why I'm wondering about this stuff now is because I've started working on an RPG to go along with the graphic novel.

For the second, while I understand what you mean, and I can't really go into details. Instances like that aren't that unusual in the grand scale of things, but it's usually less militarily or economically powerful entities that aren't capable of regularly producing 'planet busting' weapons who are prone to cramming a bunch nukes onboard on cargo ship and slamming it into a planet, and of course if you're going to talk about what is essentially a terrorist act then you would have to acknowledge the political and diplomatic reactions to such an attack especially in light of past conflicts in this universe and the numerous treaties and diplomatic commitments made by the various parties. Long story short it's extremely complicated.

Also, thinking about this detail yields interesting results in the context of a case where the ship really NEEDS to be that large (i.e. the Death Star, where the huge size of the battlestation is mandated by the huge size of the weapon it's designed to carry). Crew accomodations would necessarily be decentralized, and people assigned to one 'block' of the ship might never even meet people from another 'block.'

Also, bear in mind that the huge volume of the ship will also lead to designers building stupidly massive redundancies into the hull- if the ship has to be a kilometer wide, there is no good reason to have only one personnel transfer tube running along the spine of the ship, when you could construct dozens of them running in parallel. In real life ships are quite volume-limited. If you're building a death star, or a ship that has to find things to put into a 2 km wide hull that MUST be 30 km long because of its moon-busting spinal main weapon... you will see huge blocks of the ship filled with redundant systems and spare parts and so on which nobody ever uses.

Because having such things contributes to the fighting efficiency of the ship and prevents the massively expensive startup investment from becoming worthless due to a single case of bad luck.

That's certainly something I'm going to think about.

A sufficiently sizable ship would probably be decentralized to a degree to avoid problems like you're suggesting. However, any civilization sufficiently advanced to build a ship 30km in size is probably sufficiently advanced to automate a lot of crew functions, if not most of them.

I've taken that into consideration but because of in-universe restrictions many things require either direct or indirect human involvement. Again it's complicated politics and all that.

Ninja Edit: If I missed something feel free to point it out to me.

[Simon_Jester]

3) Thematically, ships should have a size which matches well with their purpose in the story.

Ships used by individuals for transportation will be much smaller than bulk cargo haulers. Dedicated warships will probably range somewhere in between the two (unless your society's need for killing exceeds its need for cargo transportation).

Or unless the benefits of scale are different. The battleships and carriers were appreciably bigger than Liberty ships. Not because USA did not have large needs for cargo transportation - they did, and accordingly launched 2700 Liberty ships of 14 000 tons each. Whereas the carriers and battleships were only a few tens total. USA had swarms of smaller cruisers as well. But a big carrier or battleship could do something that a swarm of smaller cruisers could not... whereas USA did not have any mission for a few big cargo ships.

Thank you for coming up with a smarter explanation of the situation that I poorly covered with "unless your society's need for killing exceeds its need for cargo transportation." I should have said something like "unless your society's need for warships of the greatest possible size exceeds its need for large cargo carriers."

Personal 'shuttles' or whatever you call them have several reasons to be small. It's not just that the ship's living quarters will be scaled to what one person needs for comfort. It's that if they're built to gigantic scale, it becomes impractical for an individual being to move about the ship and see to its functioning.

A farmhouse can be a tiny hovel - but the air is free out of the window. Feeding the resident and his family, however, may involve long walks to backbreaking work in outlying field plots, and possibly hunting trips with camping in the forests for several days. The size of an enclosed habitat to provide breathable air and good quality food for one family can be quite large - but would it ever repay the costs of building the enclosure out of artificial materials?

If the answer is "no," then you will never see individual space habitats, and may never see personal space-transports. Which is okay... but we should take that into account when writing our story. If we base our story on analogies to the world we've known in real life, there will be no equivalent of the space-motorboat for individuals, there will be the space-ocean liner.

My point is not that any one set of assumptions (practical single-person space transports) should rule, it's that the assumptions should be checked to see whether they are plausible and work with the story.

A very large personal transport also needs an extreme amount of space to take off and land (or dock), which makes it less flexible: something the size of a helicopter can take off from the roof of a building, but a helicopter the size of an ocean liner would basically have to land at a very large airport with a very large tarmac.

Or if it is amphibian, it may require a suitably large and deep body of water... with optional requirements on shelter from waves and currents.

Yes, but this is rarely more convenient than having to set down on an airport. At least on an airport, you don't need to be wearing water wings when you step out the door of your vehicle.

There actually, positively were ships designed as dedicated passenger liners, which did have tens of thousands of passengers on the manifest. Queens Mary and Elizabeth were designed for about 2200 passengers.
They were converted to troopships - and although the crossing from USA to Europe still took several days, they managed to carry over 15 000 passengers. The record is in the name of Queen Mary, from December 1942, and stands at 16 082.

Ah, excuse me. When I say "tens of thousands" I am typically thinking "several tens of thousands," not "1.5 tens of thousands when crowded well beyond their original design intentions."

Let's not lose sight of the point I'm trying to get across: scale of a ship is related to its intended function.

Similar calculations apply to a freighter. I often wonder exactly what those six million ton bulk freighters in the Honorverse carry, which can be profitably carted over interstellar distances, in that kind of volume. It gets even worse with multi-kilometer freighters, unless you have massive megalopolis-worlds or habitats with populations in the trillions whose demand for physical goods is that large.

US oil imports in 2012 are quoted at 10,6 million barrels per day - which is about 1,7 million cubic m per day, or 600 million cubic m per year. The biggest single supplier is Canada, so that could be overland, but Persian Gulf region is quoted at 2,1 million barrels per day, which is about 330 000 cubic m, or about 260 000 tons per day. You could fill the 6 million ton freighter in 23 days, which is in the same order of magnitude as the travel time Persian Gulf to USA.

Yes, the real question is what there might be, equivalent to oil, that could profitably be shipped over interstellar distances- i.e. cannot be more profitably had closer to home. I'd consider container ships a better model for this, and they cap out at about half or a third the size of the T1 tankers.

I'll grant it's very much possible to imagine economic circumstances where individual ships carrying several million tons of cargo would be profitable. It is nevertheless interesting, and in the Honorverse very vague as to exactly what those circumstances are.

Also remember that you do not need to have "trillions" in a single world. That is going to depend on the exact scaling of the ship technology. If you are trading between one end of galaxy and the other, you might have your physical goods reloaded to swarms of smaller ships which reach tens of thousands of nearby planets. So, how will your technology scale with range? Is a spaceship good to travel 500 light years appreciably different from a spaceship whose mission is 25 000 lightyears?

Ah. This is an interesting thought. Compare and contrast with Heighliners from Dune.

[Simon_Jester]

I can't really answer some of these question without going into details which I'd rather not go into. However, The scale of the civilizations in this setting are both galactic and extragalactic. There are many hundreds of millions of inhabited worlds in this universe. The vast majority of which are artificially habitable, ie. large space stations, moons, barren worlds that either required extensive terraforming or need permanent climate control facilities in order to remain habitable. Few have populations which exceed a few tens of millions. This means that the vast majority of liners and general transports are comparatively small, there's just a crap load of them. Small meaning low single digit thousands. This can obviously change when one reaches the higher populated regions of the galaxy.

Fine by me- and by implication this is clearly a pretty space-operatic setting, so it's fair to assume that the machinery needed to sustain a spacecraft's operation doesn't take up a volume too disproportionate compared to the cargo capacity of that craft.

The setting doesn't really have torpedos per-say it does use massed produced combat drone systems which fill the same roles, (5-10 meters) and are equipped with various weapons systems for different foes.

Details really don't matter- the point is, if you have a ship that carries one thousand "blahs," it must be physically large enough to store a thousand "blahs." That's the kind of error people notice. Correspondingly, if your ship is huge with room for millions of "blahs," and having plenty of "blahs" is a vital necessity, you're going to look pretty silly if your ship only carries a few dozen of the things.

3) Plotwise, you find yourself forced to ask why it wouldn't be more cost-effective to just fill a Ship of Unusual Size (whatever is 'big' in your universe) with [whatever is needed] and throw it at the enemy. For example, why bother finding a magic MacGuffin weapon to blow up a planet, when you could load down a billion ton freighter with several hundred million tons of H-bombs (theoretical explosive yield limit of several kilotons per kilogram) and carpet-bomb the planet into a sea of fire?

For the first, I'm not great at math and even if I was I wouldn't be able to calculate the proper measurements for many things in this setting because unlike Star Wars many of the things you listed aren't yet well-defined.

Well, you only use this on a rough level- for example, if passenger ships only move a thousand people at a time, clearly the passenger accomodations need not be bigger than, oh... a hotel that can accomodate one thousand people.

They're getting there but while working on the story I really haven't seen fit to lay everything down just yet. The only reason why I'm wondering about this stuff now is because I've started working on an RPG to go along with the graphic novel.

If anything, you need physical sizes more for a graphic novel. Think about it- you have ships fighting killdrones, killdrones in one scene stored in a hangar where human beings are looking at them, and dialogue about how the ship carries thousands of the things.

Suddenly it becomes important to know the relative scale of a killdrone and a ship.

For the second, while I understand what you mean, and I can't really go into details. Instances like that aren't that unusual in the grand scale of things, but it's usually less militarily or economically powerful entities that aren't capable of regularly producing 'planet busting' weapons who are prone to cramming a bunch nukes onboard on cargo ship and slamming it into a planet, and of course if you're going to talk about what is essentially a terrorist act then you would have to acknowledge the political and diplomatic reactions to such an attack especially in light of past conflicts in this universe and the numerous treaties and diplomatic commitments made by the various parties. Long story short it's extremely complicated.

I'm not demanding answers, I'm asking questions. You don't NEED to tell me the answers- just to have them.

Also, bear in mind that the huge volume of the ship will also lead to designers building stupidly massive redundancies into the hull- if the ship has to be a kilometer wide, there is no good reason to have only one personnel transfer tube running along the spine of the ship, when you could construct dozens of them running in parallel. In real life ships are quite volume-limited. If you're building a death star, or a ship that has to find things to put into a 2 km wide hull that MUST be 30 km long because of its moon-busting spinal main weapon... you will see huge blocks of the ship filled with redundant systems and spare parts and so on which nobody ever uses.

Because having such things contributes to the fighting efficiency of the ship and prevents the massively expensive startup investment from becoming worthless due to a single case of bad luck.

That's certainly something I'm going to think about.

The big limiting factor on Very Big Ships isn't so much volume as it is surface area. For example, consider a weapon system which stores missiles/drones/whatever deep inside the hull and fires them out through a "gun" that launches them out through a single portal in the surface. For a very large ship, that may be preferable to 'conventional' hangar bays. Because while it takes up a lot of volume in the interior, it does not require very much surface area on the hull, which means more room for defensive weapon mounts, sensor installations, and big heavy locked-into-place slabs of armor plate to protect the ship.

[Eternal_Freedom]

The only thing I can think of that would be worthwhile to transport in multi-million tonne quantities across interstellar distances is something comparable to oil or grain or LNG. Basically some highly useful but (comparatively) rare mineral or ore or liquid. Perhaps a naturally occurring room-temperature superconductor that is onyl found on one planet in a hundred or so.

[chornedsnorkack]

There are many hundreds of millions of inhabited worlds in this universe. The vast majority of which are artificially habitable, ie. large space stations, moons, barren worlds that either required extensive terraforming or need permanent climate control facilities in order to remain habitable. Few have populations which exceed a few tens of millions.

Compare Australia - 23 million people, and all foreign travel is overseas.

This means that the vast majority of liners and general transports are comparatively small, there's just a crap load of them. Small meaning low single digit thousands. This can obviously change when one reaches the higher populated regions of the galaxy.

Australia currently has about 30 million international air passengers per year - close to 15 millions each way. The sea passengers are presumably few in number. Obviously handling that region of flows can be made by relatively small ships... that 15 millions is aquivalent to 40 000 each day.

But are these small, artificial settlements also dominant in terms of population? I mean, when you do encounter a planet fortunate enough to be naturally habitable, it can support several milliards of people (and accommodate much more than that). So if a habitable planet has 100 times the population of an uninhabitable one, then 10 uninhabitable planets taken together would still have just 10 % the population of the inhabitable motherland. But if there are 1000 uninhabitable planets per one habitable planet then these uninhabitable planets still have 90 % population.

But are the naturally habitable planets concentrated in the higher populated regions of the galaxy, or scattered randomly all around galaxy?

3) Plotwise, you find yourself forced to ask why it wouldn't be more cost-effective to just fill a Ship of Unusual Size (whatever is 'big' in your universe) with [whatever is needed] and throw it at the enemy. For example, why bother finding a magic MacGuffin weapon to blow up a planet, when you could load down a billion ton freighter with several hundred million tons of H-bombs (theoretical explosive yield limit of several kilotons per kilogram) and carpet-bomb the planet into a sea of fire?

For the second, while I understand what you mean, and I can't really go into details. Instances like that aren't that unusual in the grand scale of things, but it's usually less militarily or economically powerful entities that aren't capable of regularly producing 'planet busting' weapons who are prone to cramming a bunch nukes onboard on cargo ship and slamming it into a planet, and of course if you're going to talk about what is essentially a terrorist act then you would have to acknowledge the political and diplomatic reactions to such an attack especially in light of past conflicts in this universe and the numerous treaties and diplomatic commitments made by the various parties. Long story short it's extremely complicated.

For example, fireships are an old tactic since ancient times. They were usually old ships. But in 17th century, navies used fireships so widely that they undertook to build and store dedicated fireships in appreciable numbers. Then in 18th century, manned sailing ships got better at dodging fireships, and dedicated fireships were gradually abandoned.

Regarding the social effects of big ships: the armies on Earth have got to several millions of men, but these were units spread over thousands of km of war theatres. But in sieges, there have been several occasions with over 100 000 men defending an area a few km across... and then they relied mostly on walking to get around.

[Sky Captain]

One setting with unreasonably large ships is Mutineers Moon. IIRC it was never explained why Fourth Empire needed Moon sized warships when their enemy used much smaller 20 - 40 km ships that were still FTL capable so you can't argue the FTL drive is so large or power hungry that only Moon sized ships can fit it. They also lacked ships sized somewhere between their battlemoons and comparably tiny aircraft carrier sized sublight warships. You would think there are plenty of missions where battlemoon is ridicolous overkill, and something smaller but still FTL capable would be more reasonable.

[Ahriman238]

It seems to have been a limit of Imperial FTL drive that the Achuultani got around. One way the Achuultani had superior technology, despite being far slower than Imperial. This is consistent with Mutineer's Moon and the theme where Imperial and Achuultani tech are better than the other in certain ways, and more limited in others.

[Simon_Jester]

The only thing I can think of that would be worthwhile to transport in multi-million tonne quantities across interstellar distances is something comparable to oil or grain or LNG. Basically some highly useful but (comparatively) rare mineral or ore or liquid. Perhaps a naturally occurring room-temperature superconductor that is onyl found on one planet in a hundred or so.

The problem is that the Honorverse doesn't actually use much unobtainium. Everything is apparently made of the same chemical elements we know and love; the technomagic is almost entirely in the form of gravity manipulation, and the machinery that does that.

One setting with unreasonably large ships is Mutineers Moon. IIRC it was never explained why Fourth Empire needed Moon sized warships when their enemy used much smaller 20 - 40 km ships that were still FTL capable so you can't argue the FTL drive is so large or power hungry that only Moon sized ships can fit it. They also lacked ships sized somewhere between their battlemoons and comparably tiny aircraft carrier sized sublight warships. You would think there are plenty of missions where battlemoon is ridicolous overkill, and something smaller but still FTL capable would be more reasonable.

The Empire had some weapons and systems the Achuultani never used, which might explain the scale difference... but there are other possible reasons.

For example, the Achuultani ships were very much designed to be manipulated and controlled from a central base- the idea of losing that base was unthinkable, so it was okay that ships would routinely need to return to the base for reservicing. The Fourth Empire already represents the third time human civilization has been wiped out by the Achuultani and rebuilt from the rubble, so they are painfully aware that if the Achuultani win the war, human civilization may need to rebuild from scratch yet again.

[Come to think of it, this is exactly what happens, although not because of the Achuultani. The Fourth Imperium is wiped out, and the sole survivors with any chance of rebuilding and defeating the Achuultani again are the descendants of the crew of a single war planetoid]

So they may build their ships to contain all the facilities to maintain themselves indefinitely, and to have enough redundancy that their systems won't fail. Which makes them proportionately larger than an Achuultani ship of equivalent fighting power- because Achuultani ships aren't designed to last for millenia without returning to their home port for maintenance.


Yet another explanation is that the Empire may have wanted to build ships far larger than any individual Achuultani fighting unit because their doctrine revolved around strategic superiority. If they wanted ships that could survive the wonkier gravitonic/warp/whatever weapons in use in the series, said ships would have to be big.

[gigabytelord]

I'll try to reply to everything as soon as I can, but I'm a little busy today. Just so you know I'm going to respond to ya'll.

[Ahriman238]

One setting with unreasonably large ships is Mutineers Moon. IIRC it was never explained why Fourth Empire needed Moon sized warships when their enemy used much smaller 20 - 40 km ships that were still FTL capable so you can't argue the FTL drive is so large or power hungry that only Moon sized ships can fit it. They also lacked ships sized somewhere between their battlemoons and comparably tiny aircraft carrier sized sublight warships. You would think there are plenty of missions where battlemoon is ridicolous overkill, and something smaller but still FTL capable would be more reasonable.

The Empire had some weapons and systems the Achuultani never used, which might explain the scale difference... but there are other possible reasons.

For example, the Achuultani ships were very much designed to be manipulated and controlled from a central base- the idea of losing that base was unthinkable, so it was okay that ships would routinely need to return to the base for reservicing. The Fourth Empire already represents the third time human civilization has been wiped out by the Achuultani and rebuilt from the rubble, so they are painfully aware that if the Achuultani win the war, human civilization may need to rebuild from scratch yet again.

[Come to think of it, this is exactly what happens, although not because of the Achuultani. The Fourth Imperium is wiped out, and the sole survivors with any chance of rebuilding and defeating the Achuultani again are the descendants of the crew of a single war planetoid]

So they may build their ships to contain all the facilities to maintain themselves indefinitely, and to have enough redundancy that their systems won't fail. Which makes them proportionately larger than an Achuultani ship of equivalent fighting power- because Achuultani ships aren't designed to last for millenia without returning to their home port for maintenance.


Yet another explanation is that the Empire may have wanted to build ships far larger than any individual Achuultani fighting unit because their doctrine revolved around strategic superiority. If they wanted ships that could survive the wonkier gravitonic/warp/whatever weapons in use in the series, said ships would have to be big.

The Imperium had largely mythic/archaeological evidence for the Achuultani, that and all the planets that had rocks dropped on them. Hence why it was so hard to plan for Achuultani capabilities and so easy to disbelieve in their existence.

Half of Dahak's internal volume is explicitly taken up by the FTL drive and power systems, largely the core tap which is the only thing they have powerful enough to sustain FTL. The same holds true for later Fourth Empire planetoids, but they can fit in both hyper and Enchanach drives. Also keep in mind that while Achuultani ships managed hyper in a far smaller hull, that hull is still a 20 km cylinder, and they could managed only 50 c. That's a fair bit larger than Dahak's parasites, the largest of which was about 80% the mass of an aircraft carrier.

Which does raise another issue. Atomic Rocket deals with it at some length, and far more eloquently IIRC, but the thrust of it is that however much mass a ship has, it will have to dedicate a certain percentage of that to power, to drives, to life support, to sensors, radiation shielding, to human passengers (unless automated, obviously) and depending on the ship and it's intended role, to cargo space, armor and/or weapons. In real life, fuel storage is a huge consideration and so we work hard to keep the mass of spacecraft down to save on it. It's unthinkable that something like the Millenium Falcon could achieve orbit, but lots of sci-fi handwaves the issue. My point is, there are good reasons for wanting a larger ship, so you have everything you need. There are likewise good reasons for smaller craft. A lot depends on the context of the fictional universe you're creating.

[Scrib]

Of course it gets absurd when you have ships that would affect the climate below due to their gravitational pull.

Which is only really a problem if they don't affect said climate. Is the Death Star problematic because it had this ability?

[lPeregrine]

One interesting constraint on ship sizes is that by the time you have the ability to build a super-ship you may not have the need to build one. For example, the Culture could very easily build bigger warships, but consider it an act of tasteless narcissism (though "make myself as huge as possible" is a popular ship fantasy in simulations). Presumably Culture weapons and defenses don't really depend on physical size like a "conventional" warship (and obviously a freighter is just pointless), so building a swarm of independent ships is far more useful than building a single big ship just for the sake of being big.