Why is refined fuel so expensive?

[rust]

An electrolysis system requires a lot of power, but it is a rather
simple system and does not require a lot of volume. The system
to remove the impurities from gas giant atmosphere or water is
only a little more complex and also does not require much volu-
me. I think the entire "refinery" would have approximately the
size of one of the smaller systems used to turn sea water into
drinking water on many real world ships - considerably less than
1 dton. As for the price, a real world system comparable to Tra-
veller's fuel processor should cost not much more than about
25,000 USD.

 

[BFalcon]

To be honest, guys, you have to remember that the Starports book already says that the majority of starports are run by the Star Ports Authority, a part of the Imperial Beaurocracy, not the locals. Therefore, all the claims of them needing to be competitive have no basis... since the prices are already subsidised. A private port would probably need to charge a fee to help cover the costs of running and maintaining the port and an independant port would probably be taxed as an extra source of planetary income, including fuel.

When I said about ecological damage before, it is true that it might be minimal, but some governments might take the longer view and be worried about what will happen in a few hundred years, or (more likely) will use it as an excuse to tax fuel sources.

As for the unrefined fuel no longer being available, I'd say that it would be true for Class A and B - the Starports book says that Class C ports can run out of refined fuel every so often, so I'd say that unrefined fuel would likely be available as a safeguard.

As for refinery equipment being on ships, I can understand it for frontier ships, like Free Traders and on smaller military ships (and possibly on fleet auxilleries), but not every ship would want to waste the tonnage when a lot of ships (larger cargo ships especially) waste money on essential downtime (such as cycling life support and waste systems and refuelling in general), making an extra 200Cr per ton of cargo isn't that hard (remember that a company won't need to find a buyer or seller for cargo while the ship is docked - they'd have either a company broker to do that already or have a retained broker on their books). Having extra cargo space would reduce that and make the whole ship more profitable in general without adding tonnage or removing any facilities on board (other than requiring the ship to purchase refined fuel). Just to put it in perspective, mid-range machine parts cost 10,000 per unit. To cover refined vs unrefined fuel, would cost 220Cr per cargo unit for a superfreighter. 5% of that 10,000Cr comes to 500Cr per unit, so you wouldn't lose much in the way of profit, but you'd also lose the 2 days it takes to refine the fuel (even assuming you can do all essential maintenance in just 1 day on one of the power plants (assuming 2 here) so that you have one online at all times to power the 850 tons of refining equipment. If you didn't need to refine, I'm assuming that you could either attach a small power-generator to maintain life support or work in vacc suits while maintaining all power systems - if docked, then you wouldn't have a problem. For most of this, I assumed that such a large vessel may not be able to dock at the highport, so would be in a holding orbit while the modules were swapped and the cargo from the bay also swapped over.

Regarding the size of the refineries, rust, bear in mind that they'd need to filter out impurities like silt or biological contaminents before being able to start the refining process - then you have to be able to deal with ammonia and non-hydrogen-based substances, not just water, so I'd suggest that it would need to be able to act as a mass-spec for quality-control as well as being able to seperate off the non-hydrogen elements, especially those not suitable for other ship-board applications. I would actually like to see refining of fuel done while the fuel is being scooped - it would make more sense to flush the impurities while pumping in the water or scooping the gases from the gas giant. Hydrogen does, after all, have the smallest molecule size in the periodic table, doesn't it? It only makes sense that impurities will take up valuable room, even in smaller quantities, being that much bigger.

Another thing to ask is this: Is unrefined fuel actually available for sale to the public on High Ports or is it purely for small craft belonging to the port and for refining into fuel (a much more valuable commodity)? If the government (seperate from the SPA) doesn't allow visitors, don't assume that it's got no ships of its own or that the system navy will ignore your landing on their planet without permission to syphon off "fuel". That government may well choose not to see the difference between refined and unrefined fuel when they come to enforce the law and arrest the "fuel thieves" (governments tend to only worry about lost taxes and revenues - and guess who would be selling the "fuel" to the SPA...). And remember that those non-jump-capable System Navy ships are going be tougher, ton for ton, than the PCs' ship...

Incidently, according to the Starports book: Independant starports who are around or on hot or cold planets would need to charge 5-50% more for fuel. Frozen or Roasting planets pretty much have to ship in fuel from elsewhere, if there's a Gas Giant, then it's 5-10% more... if not, then they need to ship it in from outside the system, charging 50-100% more. SPA ports (ie most) have these costs subsidised to the usual 100/500 we're used to (which is why the prices don't vary from system to system)... it makes sense that they'd like to claw back a little profit on the refined fuel...

 

[rust]

Incidently, according to the Starports book: Independant starports who are around or on hot or cold planets would need to charge 5-50% more for fuel. Frozen or Roasting planets pretty much have to ship in fuel from elsewhere, if there's a Gas Giant, then it's 5-10% more...

I do not quite understand why a cold or frozen planet's starport should have
problems with the fuel. Turning water ice into water is not exactly magic, and
compared to the power required to separate water into hydrogen and oxygen
the power requirements for turning ice into liquid water are negligible ? :?

 

[BFalcon]

Incidently, according to the Starports book: Independant starports who are around or on hot or cold planets would need to charge 5-50% more for fuel. Frozen or Roasting planets pretty much have to ship in fuel from elsewhere, if there's a Gas Giant, then it's 5-10% more...

I do not quite understand why a cold or frozen planet's starport should have
problems with the fuel. Turning water ice into water is not exactly magic, and
compared to the power required to separate water into hydrogen and oxygen
the power requirements for turning ice into liquid water are negligible ? :?

I think it's because you'd need to effectively mine the ice and you'd have all sorts of problems with equipment freezing, you'd need to pick up the blocks and ship them to a facility and so on - I would presume that it would also be possible to "deep mine" the ice by drilling down to a deep enough layer where the ice is liquid through pressure and use a heated hose to just pump it up... but it all costs more than just running pumped water over an omosis filter (or a few thousand) and collecting the purified water at the other end.

Edit: there may also be an element of "if it's this hard to get at, *you* can't just land and pump it into your ship, so we may as well charge more". The fuel increase is for independant ports, after all...

 

[zozotroll]

Just a comment on the eco damage from fueling. it would seem that if a port provides fuel, it will almost certasinly come from the same place that you would pick it up yourself.

You have very different player's than I've seen

In my experience it would be just the opposite. The port will almost certainly be getting it from somewhere behind dtons of red tape well vetted for ecological and economic impact, possibly even imported from the GG. The characters on the other hand are likely to not give a frak where they scoop and dash from, as long as they don't get caught...

...a pristine alpine glacier lake, perfect, remote and nobody to catch them.

...the rooftop swimming pool of the local TAS lodge, perfect, nice and handy on the way out from the starport.

...the fire suppression system of the starport landing pads, perfect, just drop our hose while we're here, they'll refill it before there's a need for it, everybody does it.

...etc. etc.

...but generally the middle of any big lake or ocean without a care to check the weather, shipping, or anything. Just land, dip, leave.

Probably didnt say that well. Although nobody has tried the TAS pool yet. but what I more or less meant was that the water n the TAS pool came from the same watertable that the PCs would raid. On a planet with plenty of people, they would indeed have a hard time doing it on the sly, and would at least be charged something for a permit to dip.

In my current group we certainly would do stuff like that, only we have a good broker, and are making so much money the fuel cost is just not worth worrying about.

Owen

 

[phavoc]

For MTU I came up with what I think seems to be a simple and elegant solution to fuel. At the local gas giant you have a a collection station with smaller tanker craft that do nothing but skim raw fuel and bring it back to the collection station. Then when enough fuel is collected it's loaded into large barges (for lack of a better term). Booster craft then connect to the barge and begin a ballistic trajectory. It's then boosted for about 8-10hrs and then released to drift to the target. During the ballistic trip the hydrogen is typically refined in transit (or not, depending on the needs). The barge is equipped with basic thrusters utilizing the onboard hydrogen as fuel, as well as basic navigation equipment to warn other ships of its trajectory.

At the receiving point its met by booster craft about 12hrs out from the target. They dock, and then fire their engines and bring it to the station that needs the fuel. The fuel is off-loaded, and then the booster ships send the tank back towards the collection station to be reloaded.

With a system like this you are going to constantly have fuel barges in transit. Since its relatively cheap to build fuel tanks in orbit, there's typically going to be a large reserve available due to the 30-45 day transit time for each tank. But once the system gets up and running, keeping up with demand should not be an issue at all. And it should be cheaper to drop ship fuel in such a manner instead of going down into the gravity well of a planet to collect it.

This sort of concept works for systems that don't have gas giants too. Except now the gathering stations would have to be located wherever hydrogen is available, even as far as the oort cloud. Though it may take years before the first fuel shipments start due to vast distances.

I've been meaning to actually put pen to paper and get the designs of all this, just haven't done that yet.

 

[DFW]

For MTU I came up with what I think seems to be a simple and elegant solution to fuel. At the local gas giant ...

I love it. Great idea.

 

[far-trader]

For MTU I came up with what I think seems to be a simple and elegant solution to fuel.

Could/should also lead to an accurate cost for fuel at the Starport once you factor in the cost of the infrastructure. Then you just need to set a profit margin and recalculate how much a shipboard refinery should cost so that it doesn't undercut the volume producers...

...so much for simple, or at least easy Might be a fun project though. Keep us apprised if you do it. Could even be a good article for a fanzine or other publication.

 

[Rick]

Heh - the return journey (empty) wouldn't be very cost effective? Perhaps they send bulk waste on the return leg to be dumped into the gas giants gravity well?

 

[rust]

I once used a similar system in a setting, but it sent only chunks of
ice asteroids towards the main world, not barges which would have
to make a return journey.

A mining platform with some drone ships at the asteroid belt captu-
red suitable ice asteroids and turned them into manageable chunks,
added a navigation beacon to warn other traffic, and accelerated it
towards the main world's trojan point.

Once it arrived there, the drone ships of a processing platform cap-
tured it and moved it to the platform, where it was turned into wa-
ter and processed into fuel, which was distributed by a small fleet of
tankers.

 

[BFalcon]

For MTU I came up with what I think seems to be a simple and elegant solution to fuel. At the local gas giant you have a a collection station with smaller tanker craft that do nothing but skim raw fuel and bring it back to the collection station. Then when enough fuel is collected it's loaded into large barges (for lack of a better term). Booster craft then connect to the barge and begin a ballistic trajectory. It's then boosted for about 8-10hrs and then released to drift to the target. During the ballistic trip the hydrogen is typically refined in transit (or not, depending on the needs). The barge is equipped with basic thrusters utilizing the onboard hydrogen as fuel, as well as basic navigation equipment to warn other ships of its trajectory.

At the receiving point its met by booster craft about 12hrs out from the target. They dock, and then fire their engines and bring it to the station that needs the fuel. The fuel is off-loaded, and then the booster ships send the tank back towards the collection station to be reloaded.

With a system like this you are going to constantly have fuel barges in transit. Since its relatively cheap to build fuel tanks in orbit, there's typically going to be a large reserve available due to the 30-45 day transit time for each tank. But once the system gets up and running, keeping up with demand should not be an issue at all. And it should be cheaper to drop ship fuel in such a manner instead of going down into the gravity well of a planet to collect it.

This sort of concept works for systems that don't have gas giants too. Except now the gathering stations would have to be located wherever hydrogen is available, even as far as the oort cloud. Though it may take years before the first fuel shipments start due to vast distances.

I've been meaning to actually put pen to paper and get the designs of all this, just haven't done that yet.

A good system just 5 potential issues/problems I can see...

1) If something should happen to the tender at either end, the barge/pod would end up crashing into something... aiming behind each planet would help to minimise that threat though. Each pod would need an on-board power system, most likely a battery, so that they can keep a warning beacon running the whole time (to aid in "catching" the pod and to prevent an incoming ship from missing it).

2) As said before, you'd need a two-way system. Maybe a garbage run in the other direction, maybe make each pod collapsable and use a ship to bring them back. Maybe have a contract with a cargo hauler for low-cost cargo (wood, etc) to be sent back the same way for collection and loading aboard a cargo ship at the other end. Sending supplies for the small fleet of tankers and the orbital station back the same way would also be essential too, so a gas-tight cargo pod would be a good addition to the pod supply as a percentage - if nothing else, collapsable gas pods could be stored in such pods for the return trip, making fewer "catches" necessary at the gas giant end.

3) Would such a system allow visiting ships to refuel at the gas giant? After all, having strange ships flying around would pose a threat of collision? If not, they'd essentially maintain a monopoly over the fuel supply in the system.

4) I wouldn't refine the gas in transit - a station refinery can handle 500 tons per day of fuel, so would be much more sensible to keep the facilities either there or at the main port. Not sending completely purified fuel back to the main planet would make most sense - less likelyhood of pirates intercepting the pods in transit - a pure product would be more tempting than an impure one. Also, shipping back as hydrocarbons would be a good plan - any oxygen in the refined mix would be useful, but any carbon could be made into industrial diamonds, making a useful side-product. Not adding refining equipment also keeps the costs per pod down to a minimum. The only costs for the refining at the port is fuel tanks (which would be needed anyhow) and as many refining modules as needed (usually one or two). That way any destroyed pod would be a minimal loss (mainly the cargo rather than the pod). Using the Small Craft rules, a 100-ton cylindrical hull would cost 2MCr as it is... so it's not something you'd really want to risk adding cost to since there'd be no way of preventing their loss if someone wanted to eliminate them.

5) You'd probably need a mass of storage on the collection depot and main starport - for when the star gets too close to the flight path and (eventually) blocks it completely. That way collection can continue while unable to send the fuel "home", but the main starport won't run out either. When the flight path clears (probably before the planet is even visible past the sun, given the flight time), overtime on crews would allow additional pods to be sent to quickly make up the shortfall. The Tug or the Recovery Ship (Starports) would be the two stock ships to use, but I'd design a custom ship to recover them in my opinion, with the grapples (Starports) and use the towing rules (basically, you'd want a M-Drive that will give the desired thrust rating of double the ship's size, if the towing ship is the same size as the towed ship/pod).

 

[DFW]

3) Would such a system allow visiting ships to refuel at the gas giant? After all, having strange ships flying around would pose a threat of collision?

Space is FAR too large for this to be a collision threat.

 

[BFalcon]

DFW: space, yes... but when the gas giant has multiple ships in the atmosphere at all times, particularly if the gases block or hamper sensors, there does exist a risk.

I'm not an idiot*, thanks DFW, I do know that hitting a craft even in a gas giant is remote, but I also know how governments tend to over-worry.

I'd suggest that they would either put a total ban on gas giant skimming (financial reasons (monopoly) to improve their own profit margin) or a ban on skimming within a certain range of the station (thus preventing any risk of collision with its own skimming operations). It might instead assign "lanes" for skimming ships to again practically eliminate the risk of collision.

Phavoc: Rather than using tankers, could you not use pipes instead? Incoming gas would be pumped up and any waste gases would be pumped back (although, to be fair, any waste gases would probably be refined in their own way and the products sold as chemicals or similar.

* OK, so that's debatable...

 

[DFW]

DFW: space, yes... but when the gas giant has multiple ships in the atmosphere at all times, particularly if the gases block or hamper sensors, there does exist a risk.

We've already dumped TL 6 probes into GG atmosphere. It wouldn't block high powered transponders that were in the upper reaches... No problem unless someone was suicidal enough to skim with their electronics turned off.

 

[BFalcon]

True, but I know *I* don't know every substance that could be in any given gas giant and I'm pretty sure that even the best NASA scientists don't either... :wink:

 

[DFW]

True, but I know *I* don't know every substance that could be in any given gas giant and I'm pretty sure that even the best NASA scientists don't either... :wink:

The physics of it narrows it down to few choices in the upper reaches. None of them able to wipe it out.

 

[BFalcon]

My point is, that we've only just begun to analyse the universe - and our understanding of physics is limited to just one planet and what we've observed thus far of the rest... There's no reason I can see why there could not be a compound thrown up into the upper atmosphere that may be radioactive or which may refract radar signals - possibly thrown up by atmospheric disturbance or (unlikely in a gas giant) volcanic activity. Our sample of evidence is just too small for us to be 100% certain.

Besides, I know what a bi*** fate and GMs are.

 

[phavoc]

A good system just 5 potential issues/problems I can see...

1) If something should happen to the tender at either end, the barge/pod would end up crashing into something... aiming behind each planet would help to minimise that threat though. Each pod would need an on-board power system, most likely a battery, so that they can keep a warning beacon running the whole time (to aid in "catching" the pod and to prevent an incoming ship from missing it).

Not really. There would be multiple tugs at both ends to catch an incoming fuel barge. And the trajectory of each barge would be to miss the planet if the catch didn't happen. Incoming barges would be picked up about 12hrs out, even though it would only take about 8hrs to decelerate. Also each pod could easily be equipped with remote-control detonation charges to blow it apart if necessary. The hull is only strong enough to retain the fuel and take the acceleration/deceleration, as well as ward off light debris strikes. Should be easily created using more advanced materials. And yes, the onboard systems would require batteries of some sort to power them. Again, not an issue. They would not require that much power to receive a signal, or squawk a transponder ever 10 minutes or so.

2) As said before, you'd need a two-way system. Maybe a garbage run in the other direction, maybe make each pod collapsable and use a ship to bring them back. Maybe have a contract with a cargo hauler for low-cost cargo (wood, etc) to be sent back the same way for collection and loading aboard a cargo ship at the other end. Sending supplies for the small fleet of tankers and the orbital station back the same way would also be essential too, so a gas-tight cargo pod would be a good addition to the pod supply as a percentage - if nothing else, collapsable gas pods could be stored in such pods for the return trip, making fewer "catches" necessary at the gas giant end.

You could, but sending empties back would not be a big deal. While its nice to send something back as payload, the goal is a continuous supply of fuel, delivered as cheaply as possible. Today we send empty containers back to Asia, though sometimes they are loaded with electronic waste or something else. But the trip back is essentially "free" because the ship needs to go back anyway. It would be easy to attach payloads to the barges to send back to the station - though it would be faster to just put it on a freighter going that way and have it delivered.

3) Would such a system allow visiting ships to refuel at the gas giant? After all, having strange ships flying around would pose a threat of collision? If not, they'd essentially maintain a monopoly over the fuel supply in the system.

Sure. A gas giant is a huge place. And a fueling station can easily say "the red spot is for us alone. You can refuel anywhere else on Jupiter". I don't see any risk to accidental collisions (stupidity is always present though). And signals (even if they are short-ranged at say 50 - 100 km) would alert neaby craft to a skimmer.

4) I wouldn't refine the gas in transit - a station refinery can handle 500 tons per day of fuel, so would be much more sensible to keep the facilities either there or at the main port. Not sending completely purified fuel back to the main planet would make most sense - less likelyhood of pirates intercepting the pods in transit - a pure product would be more tempting than an impure one. Also, shipping back as hydrocarbons would be a good plan - any oxygen in the refined mix would be useful, but any carbon could be made into industrial diamonds, making a useful side-product. Not adding refining equipment also keeps the costs per pod down to a minimum. The only costs for the refining at the port is fuel tanks (which would be needed anyhow) and as many refining modules as needed (usually one or two). That way any destroyed pod would be a minimal loss (mainly the cargo rather than the pod). Using the Small Craft rules, a 100-ton cylindrical hull would cost 2MCr as it is... so it's not something you'd really want to risk adding cost to since there'd be no way of preventing their loss if someone wanted to eliminate them.

I haven't run the number as far as that goes. You are correct that it might be cost-prohibitive. The barges have to be cheap to justify the costs. Though I don't plan on using the ship design rules as written. These are essentially like the shuttle external tank. There is a fabrication and electronics cost (that'll have to be swagged), but the hulls aren't starship class, and the electronics are very basic, and not up to starship needs.

5) You'd probably need a mass of storage on the collection depot and main starport - for when the star gets too close to the flight path and (eventually) blocks it completely. That way collection can continue while unable to send the fuel "home", but the main starport won't run out either. When the flight path clears (probably before the planet is even visible past the sun, given the flight time), overtime on crews would allow additional pods to be sent to quickly make up the shortfall. The Tug or the Recovery Ship (Starports) would be the two stock ships to use, but I'd design a custom ship to recover them in my opinion, with the grapples (Starports) and use the towing rules (basically, you'd want a M-Drive that will give the desired thrust rating of double the ship's size, if the towing ship is the same size as the towed ship/pod).

Yeah, flinging the tanks across the system would have to take into account orbital mechanics. Since I'll not know the layout of any particular system, my 'fix' for that is to simply have the boost ships alter their trajectories. So when there are no planets or stars in the way, they just boost and dump the barge 8hrs or so out from the gas giant. But in other times they may have to boost for like 10hrs above/below the system plane of the eliptic, and then begin their boost phase. A few million kilometers difference at the lauching point can mean a massive trajectory change for the destination. And, of course, orbital mechanics means everything is in motion all the time, so all that has to be taken into account. But all the course plotting would be done at the station and the boost ships are just engines with a small crew compartment attached. They aren't meant to be 'real' spaceships, just dumb ones with basic sensors to boost and pick up tanks and then bring them back to the station.

But you raise some really good points. Thanks for the feedback!

 

[BFalcon]

But you raise some really good points. Thanks for the feedback!

No problems...

With regards to the hulls - agreed - I think the collapsible hull idea would be the best, to be honest - minimise the traffic going back and forth - you'd need little more than a big foil bag with a beacon on in any case... probably safer to build it like that to be honest - any collision and it's the unmanned pod that'd die and not a manned ship. Also, the lighter the hull, the less gravity will affect its trajectory for any given velocity and the less it'll slow down the tugs (or the more it can catch in one outing). As for spares - anything needed urgently, I agree, but who cares if the tanker spares your crew wants is shipped up or put in a pod - if you have plenty of cargo space on the station then it won't make much difference for 99% of the time.

Yes - stupidity, lack of training or penny-pinching on the maintenance schedule of any given craft... (usually financial reasons, but possibly time-constraints - most likely financial though, if the ship's skimming for fuel).

I would consider having a "half-year holiday" and storing the fuel in the tanks or having a relay station for those times - constant 10-hour burns are going to eat up fuel which could otherwise be shipped and sold... have you considered a mass-driver/railgun? One large enough to load the pod might be able to get it up to speed a lot easier than a ship could... the pod would then just become a large "bullet" to be caught by ships at the other end and harvested. The magnetic induction could, I guess, also charge the battery for the beacon, but I'm less sure of that.

You could have a second station on another gas giant with stationed tugs to act as the relay if need be, but I'll leave the exact details for your version to you.

If you don't mind, I'll add this one to my file of "interesting ideas for a system to make it unique"...

 

[phavoc]

No problems...

With regards to the hulls - agreed - I think the collapsible hull idea would be the best, to be honest - minimise the traffic going back and forth - you'd need little more than a big foil bag with a beacon on in any case... probably safer to build it like that to be honest - any collision and it's the unmanned pod that'd die and not a manned ship. Also, the lighter the hull, the less gravity will affect its trajectory for any given velocity and the less it'll slow down the tugs (or the more it can catch in one outing). As for spares - anything needed urgently, I agree, but who cares if the tanker spares your crew wants is shipped up or put in a pod - if you have plenty of cargo space on the station then it won't make much difference for 99% of the time.

Possibly. But the fuel barge is essentially moving at a relatively slow rate, and it would be equipped with basic thrusters to alter its course as necessary if an object was in its path. And any ship under power can easily avoid it. I'm thinking that anything too light would run the risk of being ruptured by a stray meteroid. As far as spares being shipped on the barge. Well, these aren't shielded at all, so any cargo would have to be able to be exposed to space and radiation. A differnt sort of barge would be needed for true cargo - but the elements are the same however.

I would consider having a "half-year holiday" and storing the fuel in the tanks or having a relay station for those times - constant 10-hour burns are going to eat up fuel which could otherwise be shipped and sold... have you considered a mass-driver/railgun? One large enough to load the pod might be able to get it up to speed a lot easier than a ship could... the pod would then just become a large "bullet" to be caught by ships at the other end and harvested. The magnetic induction could, I guess, also charge the battery for the beacon, but I'm less sure of that.

The gas giant is going to offer unlimited fuel, and the receiving station would need to catch the inbounds and boost outbounds. But that could be factored into the operations. Since they would own the fuel, the actual cost is much less than regular starship operations. But something to consider.

You could have a second station on another gas giant with stationed tugs to act as the relay if need be, but I'll leave the exact details for your version to you.

I had thought about that, but the vagaries of orbital mechanics kind of make the station hard to justify. It would have to be placed far enough away from the gas giant to always hit the intended targets. Plus my idea of the fueling station would satisfy not just one planet, but any planet in the system that required fuel. That's why there will be multiple sizes of tanks. The booster craft will be able to boost 50k - 100k Dtons by theirself (yes, big engines), but for larger tanks, they'll pair up (or triple, or quad up) and boost it that way. A very busy station is going to need a LOT of fuel, and 100Dtons every 8hrs may or may not be sufficient for all their needs. So they may need much larger tanks to ensure they have plenty of fuel available. Plus the primary world could consome 100k Dtons of fuel every day, while smaller stations might only require that much fuel every month. So I figure the existing system allows the maximum flexibility for all scenarios. The drawback being that it may take 20-30 days to get where its going... so interruptions can be annoying.

If you don't mind, I'll add this one to my file of "interesting ideas for a system to make it unique"...

Sure! I'll post the final one and you (and anyone else) is free to snag that as well.