Flexible Far Traders?

[BigDogsRunning]

Aside from the economics, and a case can be made there, Is there a reason you couldn't build something like a Far Trader with a Jump-4, and use collapsible fuel bladders for any jumps further than Jump 1?

This would give you the ability to do rapid delivery of passengers and cargo up to Jump 4, yet you could economically work the mains at Jump-1, or anything in between.

I don't see any technical limitations that prevents using fuel stored in collapsible bladders for jump. Although I would suggest replacing the bladders after every (insert number here) trips to reflect wear an tear, but with high-tech materials, it might reasonably last a year or more.

 

[Annatar Giftbringer]

Only one problem... looks at High Guard, p.36:

Fuel cannot be pumped directly from these tanks to the jump drive, and so a ship must complete a jump before it can use fuel stored in collapsible tanks.

There is, however, an item in the Deep space explorer’s handbook (from the Great Rift box set) that basically does what you want: the fuel/cargo container.

 

[Reynard]

I looked over the fuel/cargo container and realized it should be part of most early space faring civilizations constrained by Jump 1. Just being able to cross two parsecs would be a tremendous leap in exploration, colonization and trade. I rebuilt the Free Trader so 21 tons of its cargo area is a F/C container doubling its range and endurance for crossing to other mains and clusters. Once in the new area, they have all the cargo space available. Big advantage for commercial ventures.

 

[BigDogsRunning]

Only one problem... looks at High Guard, p.36:

Fuel cannot be pumped directly from these tanks to the jump drive, and so a ship must complete a jump before it can use fuel stored in collapsible tanks.

There is, however, an item in the Deep space explorer’s handbook (from the Great Rift box set) that basically does what you want: the fuel/cargo container.

Thanks Annatar Giftbringer. That's exactly what I was looking for.

 

[Condottiere]

You need a collapsible hull/tank.

The percentage ratio would then readjust, permitting longer subsequent jump.

Dumping a modular hull/tank/cargo-fuel bladder would be an alternative.

 

[BigDogsRunning]

If you can use the drop tank to fuel a jump, why couldn't you use a collapsible, and why couldn't you couldn't use a collapsible external bladder in place of a drop tank?

You burn the fuel, pull the deflated bladder inside, then jump.

 

[baithammer]

Its basically a fuel bladder and doesn't have the pumps required to directly fuel a jump. ( Kinda like a fuel can that can be collapsed.)

 

[Condottiere]

I'm not the only one who considered the blood eagle.

However, there are two unknowns, the effect of acceleration, and the effect of corrosion in a jump bubble.

The two knowns are that you can't use the fuel in a bladder for the immediate jump, and that transferring it to the main fuel tank would cause instability to the point of a misjump, since the volume changes while in hyperspace.

 

[BigDogsRunning]

I'm not the only one who considered the blood eagle.

However, there are two unknowns, the effect of acceleration, and the effect of corrosion in a jump bubble.

The two knowns are that you can't use the fuel in a bladder for the immediate jump, and that transferring it to the main fuel tank would cause instability to the point of a misjump, since the volume changes while in hyperspace.

Are we assuming a jump bubble? Or, are we assuming a Lanthanum grid?

There seem to be elements that point in each direction. The Jump Net seems to point at the Lanthanum grid model of Jump, and other references point at a hydrogen filled Jump Bubble.

If it's a jump bubble, why can't fuel from a fuel bladder, either internal or external be used to fill the jump bubble. Apparently you can use drop tanks to fill the bubble, then drop them, then enter jump.

If it's a Lanthanum grid, as implied by the Jump Net, why can't you pull the net in as you deflate the fuel bladder by rapidly burning fuel to charge your Zuchai crystals, to energize your Lanthanum grid, to initiate the jump?

I'm just unclear on why you can't use a fuel bladder to fuel a jump, but you can use a drop tank. Is it a plumbing issue? I'm not satisfied by "that's what it says in the rulebook" I'm looking to actually examine it a little bit.

 

[phavoc]

I'm not the only one who considered the blood eagle.

However, there are two unknowns, the effect of acceleration, and the effect of corrosion in a jump bubble.

The two knowns are that you can't use the fuel in a bladder for the immediate jump, and that transferring it to the main fuel tank would cause instability to the point of a misjump, since the volume changes while in hyperspace.

Are we assuming a jump bubble? Or, are we assuming a Lanthanum grid?

There seem to be elements that point in each direction. The Jump Net seems to point at the Lanthanum grid model of Jump, and other references point at a hydrogen filled Jump Bubble.

If it's a jump bubble, why can't fuel from a fuel bladder, either internal or external be used to fill the jump bubble. Apparently you can use drop tanks to fill the bubble, then drop them, then enter jump.

If it's a Lanthanum grid, as implied by the Jump Net, why can't you pull the net in as you deflate the fuel bladder by rapidly burning fuel to charge your Zuchai crystals, to energize your Lanthanum grid, to initiate the jump?

I'm just unclear on why you can't use a fuel bladder to fuel a jump, but you can use a drop tank. Is it a plumbing issue? I'm not satisfied by "that's what it says in the rulebook" I'm looking to actually examine it a little bit.

Good points. A turbopump similar to what they use on rockets today is small and would provide all the necessary pumping capability. The rule is more arbitrary than backed by common sense.

 

[AnotherDilbert]

I believe a fuel bladder is just a water ballon (or LHyd ballon). It has to be used in an enclosed space, there is no chance is would survive acceleration or micrometeorites outside the ship.

It would be difficult to maintain an absolute steady flow of fuel from the bladders as they are extremely rapidly emptied, wobbling with pressure fluctuations. That is at least how I rationalise it, hence jump fuel must come from a rigid tank.

 

[phavoc]

I believe a fuel bladder is just a water ballon (or LHyd ballon). It has to be used in an enclosed space, there is no chance is would survive acceleration or micrometeorites outside the ship.

It would be difficult to maintain an absolute steady flow of fuel from the bladders as they are extremely rapidly emptied, wobbling with pressure fluctuations. That is at least how I rationalise it, hence jump fuel must come from a rigid tank.

Nah. Fuel bladders work just like rigid fuel tanks. The pump pulls the fuel from it via a vacuum process (or you put your fuel channels at the bottom, just like toothpaste). As the fuel leaves the bladder collapses, but that doesn't matter as the fuel is still able to be pulled out. We never had any issues using fuel bladders in the military. Lhyd at low temp is a liquid and flows no different than Mogas or JP8 (that's military fuel jargon).

 

[AnotherDilbert]

Only if you empty the bladder very slowly.

If you want to transport 100 - 1000 m³/s (to empty the tanks of a starship in a few minutes) there will be extremely large pipes or extremely high pressures involved. The problem is that our starships don't really have the space for extremely large pipes everywhere, and LHyd turns into a solid if we increase the pressure.

Lhyd can only exist within a narrow range of temperature and pressure:

This is not like refuelling a car, more like trying to refuel a destroyer in a few seconds...

To transport the hydrogen that quickly I suppose we have to flash heat it so it turns into gas (basically explode it) so that it can be pushed to the power plant.


The LOX pump in the F-1 rocket engine in the Saturn V pumped about 1.5 m³/s and that is much, much simpler since LOX can withstand high pressures. A turbopump works by building pressure, such a pump applied to LHyd would seize immediately as the LHyd turned into a solid inside the pump.

 

[paltrysum]

The two knowns are that you can't use the fuel in a bladder for the immediate jump, and that transferring it to the main fuel tank would cause instability to the point of a misjump, since the volume changes while in hyperspace.

Condottiere makes the key point: bladders are just for fuel transfer into the main tank. Bladders are for storage only and cannot be used as the conduit that a starship fuel tank or drop tank can.

Are we assuming a jump bubble? Or, are we assuming a Lanthanum grid?

There seem to be elements that point in each direction. The Jump Net seems to point at the Lanthanum grid model of Jump, and other references point at a hydrogen filled Jump Bubble.

If it's a jump bubble, why can't fuel from a fuel bladder, either internal or external be used to fill the jump bubble. Apparently you can use drop tanks to fill the bubble, then drop them, then enter jump.

If it's a Lanthanum grid, as implied by the Jump Net, why can't you pull the net in as you deflate the fuel bladder by rapidly burning fuel to charge your Zuchai crystals, to energize your Lanthanum grid, to initiate the jump?

I'm just unclear on why you can't use a fuel bladder to fuel a jump, but you can use a drop tank. Is it a plumbing issue? I'm not satisfied by "that's what it says in the rulebook" I'm looking to actually examine it a little bit.

The key word is "seems." There's nothing concrete that indicates that a jump net is conducive to the lanthanum grid model. We can throw that out anyway since MgT2 specifically subscribes to the idea of an LHyd bubble. The bladder doesn't work for the bubble regardless because the rules say so. You can extrapolate from the rules and try to make your own argument work, but if you want to adhere to the rules as written, you need to interpolate instead of extrapolate. Bladders don't work like drop tanks or internal tanks in the rule set. Why? We can only speculate since it isn't specifically stated, but I would assume that there is machinery in either the fuel tank or drop tank that serves as a conduit for fuel during the engagement of a jump drive. This machinery is not present in the bladder since it's essentially just a polymer balloon or something.

The long and the short of it is you can do it however you want in your game, but if you want to play it as written, bladders are not fuel tanks (or drop tanks). So to answer one of your questions: Yes, it's the plumbing.

Also for a far trader specifically, the economics of a jump-4 drive make it prohibitive. It costs MCr15 more for the drive with nominal increases in the power plant as well. It's already difficult for travellers to make their mortgage without the additions to the ship's sticker price for a drive that probably won't get used to its fullest extent most of the time. Better to put in a bladder and just make two jump-2s. Metaphor: Those old guys you see driving their 2018 Porsche Carrera on the highway going 60mph—they aren't utilizing the engine they paid for.

 

[BigDogsRunning]

The two knowns are that you can't use the fuel in a bladder for the immediate jump, and that transferring it to the main fuel tank would cause instability to the point of a misjump, since the volume changes while in hyperspace.

Condottiere makes the key point: bladders are just for fuel transfer into the main tank. Bladders are for storage only and cannot be used as the conduit that a starship fuel tank or drop tank can.

Are we assuming a jump bubble? Or, are we assuming a Lanthanum grid?

There seem to be elements that point in each direction. The Jump Net seems to point at the Lanthanum grid model of Jump, and other references point at a hydrogen filled Jump Bubble.

If it's a jump bubble, why can't fuel from a fuel bladder, either internal or external be used to fill the jump bubble. Apparently you can use drop tanks to fill the bubble, then drop them, then enter jump.

If it's a Lanthanum grid, as implied by the Jump Net, why can't you pull the net in as you deflate the fuel bladder by rapidly burning fuel to charge your Zuchai crystals, to energize your Lanthanum grid, to initiate the jump?

I'm just unclear on why you can't use a fuel bladder to fuel a jump, but you can use a drop tank. Is it a plumbing issue? I'm not satisfied by "that's what it says in the rulebook" I'm looking to actually examine it a little bit.

The key word is "seems." There's nothing concrete that indicates that a jump net is conducive to the lanthanum grid model. We can throw that out anyway since MgT2 specifically subscribes to the idea of an LHyd bubble. The bladder doesn't work for the bubble regardless because the rules say so. You can extrapolate from the rules and try to make your own argument work, but if you want to adhere to the rules as written, you need to interpolate instead of extrapolate. Bladders don't work like drop tanks or internal tanks in the rule set. Why? We can only speculate since it isn't specifically stated, but I would assume that there is machinery in either the fuel tank or drop tank that serves as a conduit for fuel during the engagement of a jump drive. This machinery is not present in the bladder since it's essentially just a polymer balloon or something.

The long and the short of it is you can do it however you want in your game, but if you want to play it as written, bladders are not fuel tanks (or drop tanks). So to answer one of your questions: Yes, it's the plumbing.

Also for a far trader specifically, the economics of a jump-4 drive make it prohibitive. It costs MCr15 more for the drive with nominal increases in the power plant as well. It's already difficult for travellers to make their mortgage without the additions to the ship's sticker price for a drive that probably won't get used to its fullest extent most of the time. Better to put in a bladder and just make two jump-2s. Metaphor: Those old guys you see driving their 2018 Porsche Carrera on the highway going 60mph—they aren't utilizing the engine they paid for.

With regards to Mongoose 2e, as I indicated, I got my answer early on from Annatar Giftbringer, the fuel/cargo container from the Deep Space Explorers Handbook. Thanks again.

I just had more questions:

As Condottiere says, why would "transferring it to the main fuel tank would cause instability to the point of a misjump, since the volume changes while in hyperspace."
Why would your volume reduction once in jump affect your jump? Everything else seems to say that once you're in jump, nothing you do can really have any effect on the Jump. Curiously, in spite of being completely isolated from the regular universe, you can be bumped out of jump from the outside, by intersecting a gravity well, but you can't do anything to collapse the Jump Bubble from the inside. If you get smaller inside an already established Jump Bubble, why should that matter?
For that matter, if you really needed to, for some bizarre reason, why couldn't you drop your drop tanks once already inside the Jump Bubble, if you're willing to lose them. You seem to stand a greater chance of misjump by interference from the drop tanks mass being too close you your jump entry point. According to various writings (not sure what is canon for Mongoose, since apparently that is a thing now), it will impact the Jump Bubble and be destroyed, or pass through and be destroyed, depending on which interpretation you take.

Getting fuel out of the bladder is easier than pumping out of a fixed fuel tank, you just constrict the bladder. It's a big balloon. You just start reeling in the restraining net and sploosh, all your LHyd goes squirting out the giant nozzle into the power plant, or through a giant heater/vaporizer to inflate your Jump Bubble.

The Jump Net seems to directly contradict the Jump Bubble paradigm. If the Jump Bubble is generated by your Jump Drive, not a hull carried grid, and carries everything inside it along, then you don't need special field cables to extend your vessels Jump Field. Why not just a cargo net, and be done with it? The only canon I've seen describing the Jump Bubble in any detail is the short description in T5, which describes a 200+ foot diameter jump bubble for a 100 ton ship. (there is a formula to calculate how large the Jump Bubble is)

If you're going to use bladders to make 2 J-2's, why not use another few tons, looks like about 13 for a 200 ton ship, and now be able to take a bunch of cargo J-1, or a little bit of cargo J-4, or anything in between, allowing the ship to take jobs requiring fast delivery of cargo and passengers. What are the economics of long legged ships? It's hard to make a go with a ship purpose designed for Jump4, but what if you've got more flexibility to take more cargo for shorter trips. It looks like longer jumps pay quite a bit more, and even, or perhaps especially, on the mains, you're going to find people who want to get their cargoes to planets 3 and 4 parsecs away. You know, right before the corporate Mega-Freighter arrives with 20000 tons of whatever you've arrived early to sell?

Lastly, regarding the economics of a more flexible design. If the Free Trader is seemingly designed to be barely able to generate enough income to pay for itself, why is the Free Trader used at all? Wouldn't someone change the design up to make it more competitive? Seems like the first thing most crews do with their Free Traders is start modifying them. If you know that your competitor just left with a hold full of advanced electronics bound for a world 3 parsecs away, where there is a good sale price, and they have to make 2 jumps to get there, and you only need one. Who wins?

 

[Condottiere]

1. My estimate for bang for buck is jump three and two fuel loads, plus drop tanks with one fuel load that's discarded.

2. The external pumps to suck the water melon bladder dry so that they'll flop along like spaniels' ears exist, you can repurpose them from the drop tanks.

3. The original intent of the writer(s) was clear, they don't want the fuel bladders to be used to facilitate the immediate jump; I'm not a materials engineer, so can't comment if that fast transfer was feasible in such flexible material in the likely rather short time frame.

4, Astrogation is based partially on the volume of the transference, and the distance travelled; I'd have gone with the volume and shape of the bubble created; alter that, the equation changes, creating a different environment, so instability. And we know misjumping is an inherent feature.

 

[PsiTraveller]

Bulk Hauler (Oukhaha class) Aslan book 1st edition page 125
Oukhaha-class freighters are the backbone of many corporations in the Hierate. The Hauler consists of a central ‘drive spine’ to which cargo
pods are attached using mechanical clamps. Fuel is stored in long fin-shaped tanks that can be collapsed and withdrawn into the central
spine when empty, to make it easier for shuttles to access the cargo pods. The freighter is unarmed by default but a common modification
is to add turrets to the prow and stern. The normal crew consists of a captain, pilot, navigator, purser, assistant purser, small craft pilot, 3
engineers and 4 cargo hands.
The freighter carries a single cargo shuttle with it, to service worlds without their own shuttle fleet.


A flexible volume ship is incredibly efficient. Hopefully I can finish up my module and publish my version of a ship: The 'Origami'' class ship that has a variable volume capability.
A collapsible fuel tank, and collapsible shipping container arrangement that can decrease ship volume to save fuel.

 

[phavoc]

Only if you empty the bladder very slowly.

If you want to transport 100 - 1000 m³/s (to empty the tanks of a starship in a few minutes) there will be extremely large pipes or extremely high pressures involved. The problem is that our starships don't really have the space for extremely large pipes everywhere, and LHyd turns into a solid if we increase the pressure.

Lhyd can only exist within a narrow range of temperature and pressure:

This is not like refuelling a car, more like trying to refuel a destroyer in a few seconds...

To transport the hydrogen that quickly I suppose we have to flash heat it so it turns into gas (basically explode it) so that it can be pushed to the power plant.

The LOX pump in the F-1 rocket engine in the Saturn V pumped about 1.5 m³/s and that is much, much simpler since LOX can withstand high pressures. A turbopump works by building pressure, such a pump applied to LHyd would seize immediately as the LHyd turned into a solid inside the pump.

The LOX pumps for the F-1 engines on the Saturn 5 could pump 94,000 liters of LOX per minute. LOX is also 16x heavier than LHyd. The space shuttle main tank had 380,000 gallons of LHyd, and it could be filled in under 3hrs. The main lines were 17" in diameter (for both LHyd and LOX).

The same question would apply to Traveller starships - how do they overcome these same pump/pressure issues? Larger ships have big, thirsty jump engines, and they are able to pump ginormous amount of fuel quickly (nearly instantaneously).

So I don't think the emptying of the bladder is an issue. If we can rapidly empty a shuttle external tank with 1980s tech we probably have figured out how to do the same in the future. Or else there's more handwavium here. I don't believe there is a model in place that explains all these issues in a relatively logical constant. I think a method was simply selected, and then other rules were selected without putting a baseline in place that explained them all.

 

[BigDogsRunning]

Only if you empty the bladder very slowly.

If you want to transport 100 - 1000 m³/s (to empty the tanks of a starship in a few minutes) there will be extremely large pipes or extremely high pressures involved. The problem is that our starships don't really have the space for extremely large pipes everywhere, and LHyd turns into a solid if we increase the pressure.

Lhyd can only exist within a narrow range of temperature and pressure:

This is not like refuelling a car, more like trying to refuel a destroyer in a few seconds...

To transport the hydrogen that quickly I suppose we have to flash heat it so it turns into gas (basically explode it) so that it can be pushed to the power plant.

The LOX pump in the F-1 rocket engine in the Saturn V pumped about 1.5 m³/s and that is much, much simpler since LOX can withstand high pressures. A turbopump works by building pressure, such a pump applied to LHyd would seize immediately as the LHyd turned into a solid inside the pump.

The LOX pumps for the F-1 engines on the Saturn 5 could pump 94,000 liters of LOX per minute. LOX is also 16x heavier than LHyd. The space shuttle main tank had 380,000 gallons of LHyd, and it could be filled in under 3hrs. The main lines were 17" in diameter (for both LHyd and LOX).

The same question would apply to Traveller starships - how do they overcome these same pump/pressure issues? Larger ships have big, thirsty jump engines, and they are able to pump ginormous amount of fuel quickly (nearly instantaneously).

So I don't think the emptying of the bladder is an issue. If we can rapidly empty a shuttle external tank with 1980s tech we probably have figured out how to do the same in the future. Or else there's more handwavium here. I don't believe there is a model in place that explains all these issues in a relatively logical constant. I think a method was simply selected, and then other rules were selected without putting a baseline in place that explained them all.

Good thoughts phavoc. I'm still trying to figure out what is happening with all that fuel in that short period of time. The jump-drive can't be fusing it that quickly, if it could, regular powerplants would be much smaller.

I was looking at the jump field being generated by gravitically compressing the hydrogen to create a tiny black hole, feeding all of that hydrogen into the black hole, then grabbing and stretching it into a hole to push the ship through. That level of gravity control doesn't seem to be out of the question, since such things as Meson screens, and Nuclear Dampers are around, and they control two of the other fundamental forces. Maybe it requires control of all three forces mucking with space on a very small scale to pop open a hole in space to enable a jump.

I'm just looking to examine it a find an internally consistent way to answer some of these questions. I'm just looking to increase immersion for myself, and understanding will enable rational explanations for issues that players might have.

 

[baithammer]

Collapsible Fuel Tank

1.) Collapsible fuel tanks (also called fuel bladders) are
large flexible bladders which expand when filled with
hydrogen fuel.

2.) Fuel cannot be pumped directly
from these tanks to the jump drive, and so a ship
must complete a jump before it can use fuel stored in
collapsible tanks.

FUEL/CARGO CONTAINERS

1.) Dedicated fuel/cargo containers present an alternative,
allowing space to be switched between uses without a
lengthy remodelling of the ship’s interior.

2.) Containers can also be built in such a manner as to retain
accessibility, including accessways, hatches and heavyduty
partitions that make them part of the ship rather
than a component that must be added or removed as
necessary.

3.) Swapping from fuel tankage to cargo space
requires little more than flushing the tanks, then loading
with cargo as needed.

There are no pumps builtin to either item, the collapsible tank is just a bladder and requires the ships pumps to transfer to internal storage to be used while the Fuel / Cargo Containers allow you to perform cargo hold janga in order not to lose access ways.

Neither can independently fuel a jump drive and which is borne out by the mechanics presented.