Resupplying big badass starships

[Feil]

Assuming an absence of replicator type stuff that magically transforms rocks into food, fuel, parts, condoms, and so on, would it be more efficient for really big huge starships like Star Destroyers, 40k ships, Death Stars, and so on to take on raw materials, finished goods, or a combination of the two? I would imagine one always wants finished goods, since every device to make something is probably going to take a lot more room than the things it's supposed to be making....

[Vehrec]

The advantage to bringing your own tooling and mining your supplies or otherwise acquiring raw materials. On the other hand, this is rather silly. Let your tenders bring the tooling. But a few small units that make common parts? Yeah, I can see that easily.

[Darth Ruinus]

Assuming an absence of replicator type stuff that magically transforms rocks into food, fuel, parts, condoms, and so on, would it be more efficient for really big huge starships like Star Destroyers, 40k ships, Death Stars, and so on to take on raw materials, finished goods, or a combination of the two? I would imagine one always wants finished goods, since every device to make something is probably going to take a lot more room than the things it's supposed to be making....

I guess it would be like today, though, if the ship or space stationis big enough,then I guess you could always spare some room for some kind of factory?

[Vehrec]

The problem of course is that warships are under strict preformance limits imposed by their mass, volume and other factors. We can't just go around adding a 100,000 tonne tooling shop to an Executor that will allow it to fabricate replacement engine parts. These abilities come at a cost to the ships war fighting ability, albeit one that may be offset by the ability to field-repair.

[Junghalli]

With realistic drives mass is going to be a major concern for spacecraft. The more payload you have the more reaction mass you need to carry, so future spacecraft designers will generally try to make ships as light as possible, like NASA does today (did you know they stopped painting the external fuel tank on the shuttle because they found out they were wasting fuel on lifting the paint?).

Of course, the only way to get viable giganto-ships is probably with some sort of nuclear pulse drive like Orion or the ICF system that was designed for the Daedalus, in which mass isn't as much of a problem (Orion, for instance, needs to be pretty much built like a tank just to survive firing its own drive system). But more payload = more reaction mass still holds true, so I tend to think minimizing payload will still be a goal, especially in high-performance ships like warships. Generally, engineers will probably consider it better to minimize the amount of stuff the ship carries as much as they can get away with and still have the ship effectively fulfill its function.

A major wild-card here, of course, is Clarketech like reactionless drives or the unrealistically high-performance engines used in Star Wars and 40K. But as long as the relationship between power consumption and payload holds I think the impetus will be toward minimizing payload.

[Cykeisme]

But as long as the relationship between power consumption and payload holds I think the impetus will be toward minimizing payload.

Yeah, this is a key point, and doubly so for warships.

Even if a fictional universe has drives with unrealistically high-performance engines, if everyone in that universe has that sort of technology (particularly your enemies), you're going to have to optimize your mass to thrust ratio to remain competitive in war.

That means no carrying factories around on the ships!


Furthermore, with the speed of interstellar travel, resupply is easy. You can just pick up what you need.

[Junghalli]

It would make sense for long-range exploration ships in universes with no or slow FTL. They're going to have to carry everything they need for a voyage that lasts years, maybe decades or centuries, so the ability to resupply themselves "off the wilderness" can definitely be useful.

For anything else, they're probably going to try to shift as much of the logistical burden as possible off the spacecraft itself.

Heh, at the farthest extreme of this there are even proposed drive systems that shift the power generation itself from the ship to the base, like laser thermal drives. Think of it as running your ship on the universe's largest extension cord. In a universe with easy long-distance teleportation you might get classes of ships that have all their fuel, power, and supplies beamed over from their bases, carrying only limited emergency supplies and power systems of their own.

[Typhonis 1]

Interestingly enough life support could also furnish food and recycle water on long voyages. The more you can do on the ship the less you have to have delivered and also as was mentioned ion the Atomic Rocket site ration containers could be made of eddible materials thus they could also be eaten.

Plants can be used to filter the air and water. Protein can come from soy. Chickens can be fed tablescraps and they also can lay eggs.

[Zixinus]

There are two obvious categories that need to be resupplied:

1. Consumables. That includes water, air, food and other equipment such as clothing or even "luxury" goods like entertainment DVDs, condoms, magazines and the like. I put it in commas because on a isolated starship with in hierarchical command where discipline is standard, a porn magazine might be more important then it normally would be. This could also include ammunition, DVDs for backuping logs, etc.

Propellent could also be included if we are talking about a rocket engine of some kind (even if the starship can gather its fuel from the solar wind, it is better to have a full tank of examined propellent that is ready for use). Fuel for the reactors is obvious.

2. Hardware. This includes components that are not meant to be consumed and are to stay but are likely to get damaged anyway. Anything ranging from screws and bolts to key components of the hyperdrive. Replacement parts essentially.

Now, the task is to reduce necessity of extra stuff. Porn magazines and other media can be digitalized.

Is it worth to be able to replicate hardware and produce consumables? Yes, although not at the front line starship's expense. Having other ships that produce parts, like solar wind farmers or greenhouse ships might have its advantages.

What I would put in, is a simple forge that can do simple parts, like screws and bolts. You can always run low on screws and bolts, and producing more of any size can be ridiculously vital for damage control. You can't weld everything.
Also producing common parts, like pipes or wire material might be also tremendously useful.

If we are talking about sci-fi, some sort of superglue might also be very useful for a variety of purposes, to seal hull breaches if nothing else. If it could act as an insulator as well and react well to fire ("well" in this context mean "not burn and stop it from burning"), the better.

[Nyrath]

The old bromide is that in military matters, amateurs talk about tactics while the pros talk about logistics.

Supplying one's star fleet may be boring and unglamorous, but it is a major factor in winning battles and a problem of nightmarish complexity.

[Vehrec]

The biggest thing that might be a driver for collection capacity on a ship would be fuel. It's not hard to envision dreadnoughts of futuristic starfleets carrying mobile refueling stations that chew into comets or gas giants for Hydrogen. The sheer amount of fuel such ships would use, for fusion and reaction mass, would be a major factor in their design. Why make 90% of the ships tonnage storage when you can just make it 20% fuel bunkers and 15% hydrogen cracking facilities? Admitably, this has its problems, but it makes for some madcap scenes where your heros are trying to wrestle an Cometoid into bay 1 before the enemy catches up to them.

[Zixinus]

Well said.

Well, that would depend on the capacities of the starship, no? If we are talking about Rocketpunk-type ships, then propellent must be supplied at almost every stop. If we are talking about Star Wars-like ships, then lesser consumables and hardware is the primary supplies.

Which very much impact on what we may end up with. I am not overly familiar with any star fleet's type of ships and what supplies they require.

Space stations are an obvious refuelling point for any occasion.

However, space stations themselves have to be supplied as well, on which we can began a line of reasoning.

The source is the matter. Propellent has to come from somewhere, planetside or from space itself. Solar wind farming is rather expensive if you consider the energy required and the care of the equipment that surely will not like the constant bombardment of charged particles and the associated radioactivity.

Then there are lunar colonies and Terran colonies (Terran as in a terraformed, inhabited world, I do not know the possibilities of non-terraformed but non-lunar worlds).

We know have a source and a target distributor. What now?

The most simple and cost-effective method is to use space's vector nature. More specifically, use magnetic launching to deliver the supplies. Guess launching rings maybe? The possibility of using solar sails and laser-guided sails is there as well.

Routes must cleaned and regularly checked, as well as possible constant calibrations to adopt to changes in orbit. Complicated and not safe but automatic and fast.

Then there are manned transports. Boring but safer and less possibility of being intercepted.

Anybody any idea how routes and vector plots would look like?

[Zixinus]

Arg, why is there no edit button here?

The biggest thing that might be a driver for collection capacity on a ship would be fuel. It's not hard to envision dreadnoughts of futuristic starfleets carrying mobile refueling stations that chew into comets or gas giants for Hydrogen. The sheer amount of fuel such ships would use, for fusion and reaction mass, would be a major factor in their design. Why make 90% of the ships tonnage storage when you can just make it 20% fuel bunkers and 15% hydrogen cracking facilities? Admitably, this has its problems, but it makes for some madcap scenes where your heros are trying to wrestle an Cometoid into bay 1 before the enemy catches up to them.

Problem is, is it possible that it may take more resources to get the propellent and possible fuel then to go away anyway? Intercepting a cometoid or whatever is rather difficult and dangerous, unless in the ring of a gas giant or a asteroid field.

There is also the possibility of harvesting the solar wind. Rather expensive energy-wise, but it can be useful as a last resort.

[The Duchess of Zeon]

The biggest thing that might be a driver for collection capacity on a ship would be fuel. It's not hard to envision dreadnoughts of futuristic starfleets carrying mobile refueling stations that chew into comets or gas giants for Hydrogen. The sheer amount of fuel such ships would use, for fusion and reaction mass, would be a major factor in their design. Why make 90% of the ships tonnage storage when you can just make it 20% fuel bunkers and 15% hydrogen cracking facilities? Admitably, this has its problems, but it makes for some madcap scenes where your heros are trying to wrestle an Cometoid into bay 1 before the enemy catches up to them.

In the TGG, the largest Taloran dreadnoughts I have designed have a metallic hydrogen bunkerage of 165 million metric tonnes; and that's with a reactionless drive; that's for the engines alone. Metallic hydrogen has two huge advantages, the first being that as a fuel source it achieves volume efficiency comparable to anti-matter for its energy yield (meaning that it can be stored in a compact, armoured hull), and that it is naturally present in gas giants and therefore can be mined. Another advantage is that it's volatile, but not as volatile as anti-matter. That may not seem like an advantage, but it lets you surround the hull of your ship with metallic hydrogen tanks, creating an ERA (explosive reactive armour) system. Also remember that continuous combat duration can be quite short; Taloran ships only have the fuel for 15 days at maximum energy usage, but that includes keeping the shields up at full power and firing the main batteries every 15 seconds, and nobody is in a battle continuously firing their main guns for 15 days non-stop while simultaneously accelerating at full power and continuously recharging the shields.

[montypython]

Anti-matter generally won't explode if the ratio of matter/anti is different from 1:1, rather radiation scouring would be more problematic. Anti-matter can be stored as a non-reactive precursor that transmutes into anti-deuterium via radiation bombardment, saving both space, complexity and headaches.

[HRogge]

Anti-matter generally won't explode if the ratio of matter/anti is different from 1:1, rather radiation scouring would be more problematic.

If you have more matter than antimatter in the container the antimatter part will detonate with the same amount of matter... if it's the other way around you get similar results, only that there is matter left.

Don't try to store 1 kg of antimatter by mixing them with 100 kg of matter...

Anti-matter can be stored as a non-reactive precursor that transmutes into anti-deuterium via radiation bombardment, saving both space, complexity and headaches.

And you would need too much energy for this "radiation bombardment" to make the antimatter usable as an energy source.

[Sea Skimmer]

Mile long warships would almost certainly have foundries and other heavy industrial fabrication capability, for making repair parts and patching. However you should have no reason NOT to simply stock up the ship will all the consumables it needs on a regular basis. If you can afford that mile long ship then you ought to have hoards of freighters of equal or greater size and a huge industrial base to support them. Trying to have a high level of onboard manufacturing will just drive up the size of the ship, and its certainly not going to be more economical then big facotiries that aren’t supposed to survive enemy weapons fire.

I suppose by the time you reached Death Star levels of ship size, then you would start to have the space and weight margin to have a complete onboard economy, but its still unlikely to be something you’d bother with.

[Junghalli]

In the TGG, the largest Taloran dreadnoughts I have designed have a metallic hydrogen bunkerage of 165 million metric tonnes; and that's with a reactionless drive

If that's 15 days fuel purely for the reactor, and it uses deuterium fusion that comes out to 7.8 X 10^16 watts. I imagine they must use some kind of serious technobabble to get rid of all the waste heat that must generate.

[Sea Skimmer]

If that's 15 days fuel purely for the reactor, and it uses deuterium fusion that comes out to 7.8 X 10^16 watts. I imagine they must use some kind of serious technobabble to get rid of all the waste heat that must generate.

Even space ships employing plain old nuclear reactors on the scale of those powering current warships would have serious heat dissipation issues; but the only technobabble you need to deal with the problem really is a device that converts heat into neutrinos.

[Adrian Laguna]

Mile long warships would almost certainly have foundries and other heavy industrial fabrication capability, for making repair parts and patching.

Indeed, real life warships have very well stocked machine shops, larger ships have larger machine shops with bigger tools and in greater quantity. It only makes sense that when you have a warship the size of a few city blocks its industrial facilities would also be very impressive.

[The Duchess of Zeon]

In the TGG, the largest Taloran dreadnoughts I have designed have a metallic hydrogen bunkerage of 165 million metric tonnes; and that's with a reactionless drive

If that's 15 days fuel purely for the reactor, and it uses deuterium fusion that comes out to 7.8 X 10^16 watts. I imagine they must use some kind of serious technobabble to get rid of all the waste heat that must generate.

The power output is 5.5 x 10^19 watts, actually--they use a rather esoteric form of solid-state fusion with very limited anti-matter enrichment (in a second stage of the process). The answer is that though the reactor output is limited in fusion to low percentages of efficiency relative to anti-matter, capture and use of waste-heat is subject to innumerable levels of sophisticated effort to try and bring utilization of power up to reasonable efficiencies. Also notice that the figure assumes the shields in static maintenance mode most of the time, or even dropped and automatically rising again in response to incoming attacks, and numerous other automated efficiency measures to squeeze as much power out as possible.

The "continuous combat" figure of 15 days yields a practical operational duration of a Taloran month--73 days--in wartime before the ship's fuel has been drained to the point that they must be refueled (but probably still have tankage; everyone keeps safety margins).

So in short the obvious answer is that if you have reactionless drives (based off of Heim theory, here), waste heat capture and recycling is much, much less of a problem than it is in real life. Unrealistic? Certainly; but my goal was internal consistency, not hard SF realism, with enough of a grounding that things actually make sense (i.e. avoiding such egregious ideas as Weber's ships-of-styrofoam masses). It DOES, however, show the immense amounts of fuel required by an uber-powerful star dreadnought without simply resorting to handwavium. One TGG-equivalent of a metallic hydrogen supertanker with a capacity of 376 million metric tonnes is required to go to the front, refuel two dreadnoughts, and go back home. At least there is no need to manufacture fuel, and you can establish fueling stations at every single Jupiter-type gas giant in the Empire.

[RedImperator]

Is it worth to be able to replicate hardware and produce consumables? Yes, although not at the front line starship's expense. Having other ships that produce parts, like solar wind farmers or greenhouse ships might have its advantages.

What I would put in, is a simple forge that can do simple parts, like screws and bolts. You can always run low on screws and bolts, and producing more of any size can be ridiculously vital for damage control. You can't weld everything.
Also producing common parts, like pipes or wire material might be also tremendously useful.

You're looking at it backwards. Screws and bolts require specialized equipment to manufacture with any kind of efficiency (you could turn them individually on a lathe, but that would be a ridiculous waste of time, and you'd still need to manufacture the rods), and are lightweight enough that you should be able to carry all you could conceivably need between resupply. Likewise wire and piping require specialized equipment and probably aren't worth manufacturing on board unless this is an extremely long duration voyage.

What a machine shop should be for is manufacturing replacement parts out of blanks, sheet metal, uncut pipe, etc., and possibly casting plastic parts. The main purpose of the machine shop should be to supply parts for emergency repairs. Unless you're going to be in the field for a long time, you're better off carrying a supply of replacement parts for routine maintenance and anticipated routine breakdowns, since they can be manufactured to much tighter tolerances under controlled factory conditions where there's no mass penalty for specialized equipment. Where you might need the machine shop is if critical widget X had a manufacturing defect that caused it to break down 5000 hours before it was supposed to, and you need to make a replacement to restart the engine for an upcoming burn.

Overall, I don't think very highly of schemes for a spaceship designed to do other things to "live off the land". Some ships may have to do this--say, interstellar ships going to virgin territory in a no-FTL universe--and all bets are off if there's magical matter-duplicating Clarketech afoot, but there's a reason aircraft carriers don't sail around the world with foundries and manufacturing plants on board, and that goes triple in a situation where every gram counts.

[The Duchess of Zeon]

Seriously. I mean, just establishing fueling posts along your military frontiers. If you advance, then just install more. Use prefabricated atmospheric tapping stations for gas stations, and bring more in each time you advance into enemy territory, with more rapid, long-distance actions relying on a fleet train of metallic hydrogen tankers. The stuff is everywhere that you have big gas giants, and there are a lot of big gas giants in the galaxy.

[Junghalli]

Indeed, real life warships have very well stocked machine shops, larger ships have larger machine shops with bigger tools and in greater quantity. It only makes sense that when you have a warship the size of a few city blocks its industrial facilities would also be very impressive.

I don't think sea ships are a very good analogy here, because sea ships aren't subject to the punishing payload-fuel correlation that spacecraft are; they get to ride around on a giant supply of free propellant mass, while spacecraft have to bring it all with them. As I said earlier, every extra ton of stuff you put on a spacecraft means a proportionate increase in the fuel it has to carry, so I think with most (halfway realistic) drives there's going to be a very strong push to lighten the ship as much as possible, which means shifting as much of the logistical burden as possible off it. It's rather telling that in some RL proposed designs, like laser thermal propulsion, this even extends to shifting the main power plant itself to the base.

Granted you're not going to get a giganto ship at all without something like Orion, for which the restrictions are less stringent.

On ships with uber reactors, it occurs to me that as long as they have force shields it can be done fairly easily. You set up one of those shields around the inside of the engine block, and the waste heat all gets carried away with the expelled propellant. This is probably how it's done in settings like Star Wars and 40K.

[Vehrec]

Seriously. I mean, just establishing fueling posts along your military frontiers. If you advance, then just install more. Use prefabricated atmospheric tapping stations for gas stations, and bring more in each time you advance into enemy territory, with more rapid, long-distance actions relying on a fleet train of metallic hydrogen tankers. The stuff is everywhere that you have big gas giants, and there are a lot of big gas giants in the galaxy.

The Covenant took this philosophy to it's logical extreme when they started building things like the Unyielding Heirophant. Prior to a planned assault on Earth, they resupplied over 500 ships, mostly fleet carriers and cruisers from that one station. That they had just moved into position. Once you start building orbitals, you might as well just stick FTL on them and take them with you seems to be their opinion. Of course, you have to shield the fuck out of such a vulnerable linchpin of your attack in order to make it worth your while.

This is not to say however, that this is always the way to do things. Your tech level might be so high that you don't need to putter around with mundane transmutation of lighter elements into heavier ones to produce energy. Or you might be waging a war with relativistic ships that need to refuel every 10 years of acceleration. In both cases, the supply situation is radically different from the one we were discussing. So I guess the real lesson to take away from this is 'it all depends on how you do it.'