Cargo sizes

Ever seen a tugboat pushing barges on a river? If it is bulk or raw steel, or plates or rods, how about bundling them together and slapping a "containment field" around them, then towing them or pushing them like a barge? The smaller ship just needs enough power to get them going, and a captain with enough clever to keep them hidden from pursuers.

Good Luck!

That really depends on how powerful your engines are, how much fuel you're willing to expend, and how fast you want to get where you're going. You're going to have to decide which of those factors are most important for you.

Also remember that you need to decelerate the stuff for about as long as you spent decelerating it.

This also depends on if you're going for hard sci-fi or not. If you're working with FTL drives the the related level of technology, for instance, then you can fudge all sorts of values for whatever you require. If you're going for more of a hard sci-fi story, though, you'll have to do the math and figure out what makes sense.

Also, if this is hard scifi, piracy is going to be difficult to pull off. You need to match speeds with an extremely high velocity (and likely uncooperative) ship and you WILL be seen weeks, if not months, before you make contact with your target, so you would need to consider how those obstacles are overcome.

The Lonely One said:

<snip>Any advice? Or is this just "eh, make it up if it fits" kind of thing (I suspect it might).

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Well, i'll assume up front we're not talking about hard SF, because realistically trade (and consequently piracy) is quite unlikely in space, because the distances are just too friggin' big.

Anyway, the most important point to consider is how your drive works. From that you can infer how much shipping would cost. Ultimately, transport ships will be designed to make shipping costs as low as possible. If there's a StarTrek like society without money, it's still the same, costs would just mean energy and material required.
Anyway, transporting inert goods like steel can vary wildly. Basically, you could strap millions of tons together, give them a shove in the right direction, and just wait until they arrive. It's not like the stuff has a best before date.
If your drive works somewhat realistically (i.e. a reaction drive) that's what you'd do. A transit time of a few years (for a intrasolar distance) is not a big problem. Depending on the way you want it you'd start really big packages a few times a year, or smaller ones more often.
Because there is no friction in space, if you double the mass a freighter carries, you just cut its acceleration by half. There's no upper limit. Which is pretty much what the answer to your question boils down to i guess: No physical or technical limit, so pick a size that makes sense economically. Of course, if you're ferrying food or other time critical wares, you need a ship that is fast enough to get it to the destination in time.
And if you don't have a reaction drive, all that is out the window. Maybe some kind of warp-drive has an upper limit of mass it can warp. Or an upper limit of volume. If you can describe how your stardrive works it would make it easier to work out some details.

Why are people shipping steel across deep space? Steel is heavy and easy to make, doesn't make sense to ship it - you would only ship stuff you can't get locally.

waylander said:

Why are people shipping steel across deep space? Steel is heavy and easy to make, doesn't make sense to ship it - you would only ship stuff you can't get locally.

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Exactly. This kind of thing has always been an SF conundrum to me.

Regards "shipping" anything in space, you have to depend on readers being willing to suspend disbelief in the practicalities. You need a more or less magical source of enormous energy (dilithium crystals, for instance) and the ability to transcend the speed of light. Frankly, if you're writing this kind of thing, I wouldn't even go into the mechanisms involved; you just do it, and the readers willing to accept the premise will do so.

It really isn't much different from the real world in this respect. If I'm reading a story set on an oceanic cruise ship, for example, I really don't give a rat's what kind of fuel it uses, or even how fast it travels, unless those things are material somehow to the plot and characters.

caw

The Lonely One said:

The fact that this particular trade route passes through a nebula plays a part; it's what makes the spot attractive to pirates. There is an equivalent of light-speed travel which propels ships, perhaps I should think more on something beyond "warp" or "hyper" drives. I just didn't want to fudge a number that people would either say "psshhht, steel workers now adays haul more than that on Earth" or "that's a ridiculously large amount. Earth would never have that much steel to give in one shipment."

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Ah, that is a different kind of thing you're getting at. Let's call it perspetive.
For example, the EU has an anual output of steel of about 150 megatons. Doesn't really make sense for any economy of similar size to import steel in kilogram ranges. If you're looking for some good figures here, i'd suggest just checking out the various production statistics easily availble via google. If you see how much stuff a country realistically produces and imports/exports, you can extrapolate for planets, or asteroid nations etc. Though sine it's SF. a much higher production (per capita) is quite likely.
Of course, this does not tell you how much you'd find on a single given freighter.
On another note, nebulas in space are really really big, and really really vacuum like. It's not like when you're stuck inside a fog bank on earth. The density of the usual nebula is a lot less than the density of air on earth.

Also to note here is that freighters with pilots aren't all that useful. Since in space you always fly in straigth line, you'd just use automated freighters, if at all. Though of course, this depends on how your drive works exactly.

Also, is kilograms a good measurement? Kilotons maybe?

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Depends on the drive. Probably more like mega and gigatons.

waylander said:

Why are people shipping steel across deep space? Steel is heavy and easy to make, doesn't make sense to ship it - you would only ship stuff you can't get locally.

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Well, when we're talking realistically, there's nothing you can't get, or manufacture, locally. The distances in space just make transport much to expensive.
Though without trade, most of Space Opera wouldn't work, so you just need to assume dirt cheap spacetravel and gloss over it.

The Lonely One said:

pilot for docking and small changes/computer error at sub-light speeds, plus freighters in this universe "own" their ships and work on freelance payments with shipping companies. They'd prefer to accompany their loads, I'd think. This guy would, at least.

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The problem with taking people along is that it's incredibly expensive. Food, life support etc. You can just move the thing on autopilot most of the time, and switch to remote control close to the target (and while taking ff)

Perhaps steel could be changed to something that is Earth-specific? Any suggestions? The load isn't plot-specific so, fire away with suggestions.

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Realistically, there isn't anything earth-specific. Or alienplanet-specific for that matter. But it's okay, as long as your spacedrive is really dirt cheap to operate, even transporting steel might make sense. Well, more likely raw iron, not steel anyway. Mining asteroids would be more productive than mining on a planet, so getting the iron from the asteroids to the planets takes some flying.
though pirates wouldn't really steal something like steel, with a low value per weight/volume ratio. Even if shipping is dirt cheap. They'd go and steal gold, or deuterium or basically anything that is small and expensive. Try to sell a million tons of steel if you're a pirate. Noone but a whole planet will buy that amount, and everyone knows a chunk just that size was nicked by pirates last week.

Some rare ores - Palladium or Iridium maybe

Really, Willibee had it. The only economical way to make any significant transport would be rafting it like logs on a river. You wouldn't even have to go with the raft, just point it in the right direction and contract with midway pilots to make sure the cargo was in transit.

Of course, like everyone else said, there aren't many things you'd want to bring instead of build.

L.O. - Have you studied much astronomy/space science? The more astronomy you read, the more ideas will present themselves to you.

1. As Waylander says, you don't need to ship steel across space. Easy to make locally.
2. Lhun's points about nebulae and freight are spot on - nebulae usually aren't dense enough to provide good hiding places, and if the freight's traveling in a straight line, you don't even need a ship - just the sci-fi equivalent of a cannon to shoot it out of, and a net to pick it up.

Some possibilities-

CARGO - something that's unique to a particular planet: livestock, biological samples, irreplaceable technologies, spices, jewels, native arts and crafts. For instance, author H. Beam Piper invented a gem called the "sunstone" that was a fossilized, thermoluminescent jellyfish. Unique to its home planet, it was valuable enough to be worth transporting across light years.

LOCALE - Instead of a nebula, how about the upper atmosphere of a gas giant, or the corona of a star? Both of those make excellent hiding places - if you can survive in them.

Best of luck.

The Lonely One said:

Thanks for the feedback. An argument, albeit probably a weak one:

from a Deep Space 9 episode:
A force of 150 Jem'hadar attack ships was hidden within the Omarion Nebula to await the fleet's arrival.

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Hey, LO-

Unfortunately, quoting from TV won't get you very far. TV shows (even good ones, like DS9) are notorious for ignoring the realities of astronomy and physics.

Also, these realities aren't merely genre conventions of "hard" sf - they're actual, bona fide facts. You can write around them (for instance, by inventing a "faster than light" drive with magic technology) but you do have to acknowledge them; ignoring them for your convenience will reveal ignorance on your part to the reader. Readers and editors are more demanding than a TV audience.

If you want your pirates to be stealthy, you're going to have to rely on something other than avoiding sensor detection. Even at our current tech level we can spot a spaceship quite easily. Between radar, lidar, and passive sensors, there's really no hiding to be had. Even a ship with a refridgerated outer hull would be a great big thermal beacon against the background radiation.

A few other options you may wish to consider:

If your FTL a jump drive (IE, does it do everything in "hops"?) have your pirates use their FTL drives to jump right on top of their target, giving the target no time to defend themselves or to power up their own drives.

If your FTL is a warp drive (IE, you just run it all the time to achieve superluminal speeds ala Star Trek?), then a ship that is trying to detect inbound attackers will NOT be looking using their standard sensors, since the attackers would arrive before the radar pulses (or infrared radiation) even reached them. In order to detect such a ship, you would need another "magic" technology with faster than light detection, and perhaps THAT can be defeated somehow... you can make up the rules there!

Another option if you're utilizing a warp drive would be to have the pirates lie in wait along the target's path. A ship travelling faster than light is unlikely to be able to employ traditional sensors, so it wouldn't be able to detect the threat while the FTL is engaged. From there, you can have a few ways to ambush them... either be waiting at the spot where the FTL must be disengaged (perhaps it heats up during extended use but there's no efficient way to radiate heat while in warp?) or introduce a technology that forces a target to shut down their FTL drive (perhaps by mimicking a gravity well).

A fourth, more traditional option is to hide in plain sight. Against the background radiation of empty space, a ship is plainly visible, but against an asteroid or planet? Not so much! If your freighter is, say, using a gas giant as a gravitational slingshot to correct its course, it might pass close enough to the planet that pirates hidden in orbit could launch an attack without being immediately noticed if they took precautions to limit their profile (reduce the amount of heat they're radiating, hide in the planet's rings, etc...)

Hope that helps.

The Lonely One said:

For a ship that is in the vacuum of space all of the time, and is transporting steel from one space location to the next (stations orbiting planets) is there a reasonable limit to how much cargo is stored in the ship?

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No reason to store steel in a ship. Just bundle it up, cover it against radiation and tow/shunt it. How much you can tow depends on how hard you want to accelerate/decelerate it... which in turn depends on how quickly you want it to get there, and how cleverly you can turn energy into speed. Presumably your steel was mined and manufactured outside of any strong gravity field (e.g. in an asteroid belt)

China has been estimated to consume around 310 megatons of steel annually. To give you an idea of bang for buck, the largest nuclear device detonated was around 50Mt of TNT or 2.1 x 10^17 joules. If you imparted all that heat as kinetic energy into one big lump of Chinese steel then you'd have:
The distance from Earth to Alpha Centauri is around 4.1 × 10 ^ 16 metres, so the single big H-bomb could (at best) blast China's steel consumption so that it would take around 36 million years to reach Alpha Centauri. Ignoring relativity, you'd need around 36 million big H-bombs to spit China's steel consumption to the next solar system inside a year (and of course 36 million H-bombs to brake it too).

Lesson: don't send heavy items over large distances unless you have cunning short-cuts or stellar-levels of energy by which to send them.

The best way to hide a ship is to hide it with decoys. It'd be FAR easier to produce a 50 probes that put off radiation similar to that of a ship, than it would be to hide a ship in space. This way if you do have to worry about pirates or something, you can reduce the chances of you being intercepted substantially by moving in a "cloud" of decoys that might be a million miles apart.

waylander said:

Some rare ores - Palladium or Iridium maybe

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Well, worth transporting, maybe. Depends totally on transport costs of course. But nothing, not even rare ores are really exclusive to one location. The farthest you ever have to go to get all elements you need is the Oort cloud. The question really is if mining material elsewhere+shipping is cheaper than mining deposits that are more difficult to access locally.

The Lonely One said:

Thanks for the feedback. An argument, albeit probably a weak one:

from a Deep Space 9 episode:

Same concept in my story is presented in this example. However, is the example I've posted breaking the "rules" of hard sci-fi? Is this one of those "it's Star Trek, go with it" moments, and could I get away with it if I was convincing?

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Well, as i'Ve said many many times, and probably annoyed the heck out of anyone reading those threads by now D) there is no stealth in space. Period. That's it. Discussion ended.
But don't let that stop you, it just means you need to invent some technobabble way. If you don't intend to write Hard SF, don't get too hung up over details. Though imho it is still important to know enough background to recognize where technobabbly is necessary and where realism will do.
Anyway, for the question at hand, i most emphatically vote for cloaking devices run on applied phlebotinum instead of hiding inside a nebula. Because nebulas are real existing thing with known properties, which contradict anyone hiding in them, while cloaking devices are perfectly acceptable phlebotinum technology.
It's like the difference between the P.I. in a SF noir novel using his personal stealth field thingummy to hide from the guy he's shadowing, vs. the P.I. in a SF noir novel hiding behind a clear glass sliding door from the guy he's shadowing. The fact hat personal stealth thingummys might not work realistically is much less jarring than the fact that you can't hide behind glass.

I'm somewhat set on some kind of nebula or space dust collection being a spot where the ship would get hijacked. Popular games and stories sometimes portray a breaking of light speed by way of an engine decelerating device used by the bad guys trying to hijack. I think it's a matter of how "hard" I'm going perhaps. Not all the technology I'm using is entirely realistic given current physics, and perhaps this hijack maneuver is one such example.

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The problem here is that interstellar dustclouds and nebula only look like something from lightyears away. Close up they look pretty much like nothing. Also called vacuum. Same as with asteroid fields. Maybe you could just invent some property of your spacedrive that makes it more prone to disruption inside a nebula, even though there is no difference noticable on a normal physical level?

Though the gas giant is a good idea, I have trouble with a trade route passing through a gas planet's atmosphere or anywhere near a star.

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Good instinct. You do not realistically pay attention to stars or planets when travelling interstellar distances. The chances to hit a star by accident aren't higher than getting hit by an asteroid on the highway.

You've convinced me on steel--unless perhaps the shipping is done to a deep space station not near a planet where the steel can be produced easily? (or maybe make up a new metal alloy which only Earthlings have the ability/formula to make?).

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In the latter case you'd ship over the production facilities instead of the alloy, or rather, the necessary facilities and experts to build the production facilities (and train more people) to produce the alloys. There is pretty much nothing that could not be produced anywhere, you just have to ship the technology and know-how to where you need it.
The former case makes sense if you have cheap spacetravel. You'd produce raw materials of all kinds by mining moons and asteroids, i.e. anything out of a planetary gravity well. If you're patient enough, the costs to ship metal from asteroids to wherever you need it is cheaper than trying to lift it off a planet. You'd probably still mine the planet for the needs onground though.
Anyway, shipping iron from asteroid mines to the orbits of planets where you build ships and spacestations is not unlikely. Though in the case of ships you'd probably build those near the asteroids too.

There are various ideas which might allow me around this issue. Only catch is the guy has to be piloting the freighter, in order to end up in a situation where his death is part of the heist. They aren't using the traditional rocket fuel NASA uses nowadays. It'd be a more concentrated mixture of advanced fuels for propulsion, perhaps something found off-world.

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Well, any future scenario requires access to easy energy, which means ion drives (or fusion drives) are the way to go, unless you have far-our reactionless drives or the like. In both former cases, the fuel is not really a problem. Reaction mass can be almost anything, fuel for the reactor would depend on the reactor.
One interesting thing to consider would be that your lone freighter pilot, ferrying around megatons of steel, is literally sitting on a doomsday weapon. You might want to figure out a way your universe deals with that. I.e. a freighter that can reach interesting speeds (=does not take years for a trip from outer to inner solar system) could easily wipe out everything on the surface of a planet if the pilot crashes into it. Not likely to happen by accident, but even the slight possibility of someone doing that on purpose should make the authorities very, very nervous.

Dommo said:

The best way to hide a ship is to hide it with decoys. It'd be FAR easier to produce a 50 probes that put off radiation similar to that of a ship, than it would be to hide a ship in space. This way if you do have to worry about pirates or something, you can reduce the chances of you being intercepted substantially by moving in a "cloud" of decoys that might be a million miles apart.

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The problem with decoys is that they are extremely expensive. To be convincing they need to output the same amount of radiation as the ship they're mimicking, which requires the same reactor output. Even if it's only short-term, the decoys will have to produce a hell of a lot of energy. For warships they'd be totally impractical because of that, you could far better use that energy for weapons.

The Lonely One said:

Very extensive ideas. I see what you all are saying about nebulae (nebulas?). I'd either have to invent a previously unknown collection of fog or dust or particles or gas pockets--any of these possible?

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Very unlikely. Any gas has an inside pressure, while vacuum. Well, has not. So the gas cloud will expand until it is too thin to still be called a cloud. Works the same for dust.
If the density is high enough to keep it together, it will condense into a planet, or star, if there's enough gas.

--or find another way. One thing I don't want to lose is the pirate group's ability to nest in this area. Open space isn't quite their bag, I'd suppose.

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Put them on a planet? Maybe a rogue planet?

Also did I mention the freighter does not land on planets? It operates entirely in space, thus avoiding the troubling cost of liftoff and landing such a large hunk of ship .

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No spaceship will be designed to land on a planet. The requirement to operate in an athmosphere and overcome the planets gravity are so different from the requirements of deepspace flight, that it makes no sense at all to built a ship that can land. Spaceships and shuttles are completely different in purpose. You might even have orbital elevators or other methods to get stuff into orbit that replace shuttles.

Though allegedly Newtonian physics plays a part in all this, I must suppose.

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Not so much newtonian physics as simple design requirements. I.e. spaceships are designed for an environment of 0 bar outside pressure. Atmospheres are different. Spaceships do not need to be designed aerodynamically. Spaceships require massive radiator panels to stay cool in space. Would burn of when entering an atmosphere. (or you'd have to enter really, really, slowly) Etc. pp. and so on.

Who woulda thunk writing a paragraph in SF would rely on so much background? A burden of the genre, eh?

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Well, as any medieval weapons reasearch thread shows, you can need at least as much research in fantasy too. Writing about worlds you're not familiar with because you live in them is always more difficult. But a lot more fun too imo.