[Crazy Idea Time] Folding Starship

[FallingPhoenix]

Assuming you can use a drop tank of fuel to run a jump drive, then your ship uses all of the fuel right at jump, and not over the course of the trip.

A jump drive's fuel use and range is based on the volume of the jumping ship.

So...pump the fuel by compressing the entire fuel tank, thus collapsing it at the same time. Presto! Your 200 ton with 70 tons of fuel can now go 5 parsecs instead of 3 because it's compressed down to 130 tons!

 

[Condottiere]

I've played around with the idea.

But I doubt that you can collapse it, because the chances are that within the timeframe of the transition, the volume would be too unstable for the computer to control the jump.

At the moment, I think the piston variant, with the controlled reduction of the volume might work.

 

[phavoc]

The idea is interestimg, but remember the tank is full of liquid hydrogen and it must be strong enough to maintain the rigidity required to make it a tank and not just a balloon.

I'd also say it was trying to game the system too much against how volume is calculated for fuel consumption.

 

[Sigtrygg]

If you can collapse a tank down while fuelling the jump drive then why not just use hoses from a tanker or station to fuel the jump drive and you don't even need the collapsing tank.

 

[Condottiere]

Extrapolating from drop tanks, I'd say you have to directly be connected, and from balloons, can't be flexible, except to fill up the primary tanks, probably after the jump.

 

[ShawnDriscoll]

If you can collapse a tank down while fuelling the jump drive then why not just use hoses from a tanker or station to fuel the jump drive and you don't even need the collapsing tank.

If a hose is connected when the bubble is formed... it would make for a nice one-shot game, with lots of panic.

 

[Sigtrygg]

You could say the same for the collapsing tanks not being collapsed or drop tanks not being far enough away

The problem I have with drop tanks or other types of immediate use jump fuel storage (such as the proposed collapsing tank of the OP) is that internal pumps and conduits must be able to get the fuel from the tank to the jump drive within the timeframe of jump prep. So why not put that machinery on a tanker and remove the necessity to have fuel tanks at all? Have a fuelling station at the jump point.

 

[ShawnDriscoll]

You could say the same for the collapsing tanks not being collapsed or drop tanks not being far enough away

I make my bubbles huge. Scout ships can fit inside them.

The problem I have with drop tanks or other types of immediate use jump fuel storage (such as the proposed collapsing tank of the OP) is that internal pumps and conduits must be able to get the fuel from the tank to the jump drive within the timeframe of jump prep. So why not put that machinery on a tanker and remove the necessity to have fuel tanks at all? Have a fuelling station at the jump point.

That's the majick part of Traveller (included with the majick part about creating the bubble without killing all the crew). Most good role-play comes from such moments.

 

[FallingPhoenix]

You could say the same for the collapsing tanks not being collapsed or drop tanks not being far enough away

The problem I have with drop tanks or other types of immediate use jump fuel storage (such as the proposed collapsing tank of the OP) is that internal pumps and conduits must be able to get the fuel from the tank to the jump drive within the timeframe of jump prep. So why not put that machinery on a tanker and remove the necessity to have fuel tanks at all? Have a fuelling station at the jump point.

If I remember the last description I read about drop tanks, there's a significant chance of damaging the drop tank after you drop it, so a separate refuelling station that close would take a lot of repairing.

 

[Condottiere]

A kilometre long hose will not have enough pressure and will lag anyway.

If the tanker is parked right next to the jumper, it will cause interference in the transition.

 

[Sigtrygg]

So handwave handwave handwave
a drop tank can work but a hose pipe can't.

You can have a big balloon on the hull for liquid hydrogen that collapses down to next to nothing before jump (where does the pressure come from to force the hydrogen... oh never mind I already know the answer... handwave hamdwave handwave)

The oiler has 20 minutes to get out of the way before jump transition.

 

[Reynard]

If they could make drop tanks from fuel bladders, then Traveller would never use drop tanks. There is a reason fuel bladders aren't external fuel tanks. Flexible collapsible tanks would be fighting the vacuum of space and make them highly inefficient for quick evacuation to the jump.. A solid, rigid tank has no such issue. another issue is you are dragging around the tonnage of a collapsed tank. Using the internal fuel bladder as example, you have 1% the bladder fuel tonnage flapping around in zero g that must be included in a ship's total tonnage until removed. Since Mongoose use a bubble jump field, we'll be kind an say it won't make contact with the jump horizon.

 

[Tenacious-Techhunter]

So handwave handwave handwave
a drop tank can work but a hose pipe can't.

You can have a big balloon on the hull for liquid hydrogen that collapses down to next to nothing before jump (where does the pressure come from to force the hydrogen... oh never mind I already know the answer... handwave hamdwave handwave)

The oiler has 20 minutes to get out of the way before jump transition.

You seem to be misunderstanding the difference between a handwave and physical constraints.

A Handwave is a made-up excuse not dependent upon anything but the GM’s insistence.

A Physical Constraint is a property of physics that cannot be arbitrarily bypassed by mere technology.

 

[PsiTraveller]

One or two more steps and you have the Jump Pusher. This is a ship that has large jump engines and creates a Jump field and pushes the ship that wants to travel into the Jump Bubble, then the pusher ship acts as a Drop Tank and gets out of the way of the Jump bubble and the 2nd ship makes the Jump. This would allow SDB's to be pushed from system to system without having Jump engines themselves.

The next step is a Jump Gate that creates a Jump Bubble and the ship moves into the bubble and Jumps away.

It all depends on what sort of jump physics you want to allow in your game. How far from the standard jump engine do you want to go?

RAW collapsible tanks are not connected to the Jump engine. Demountable tanks can be, so can Drop Tanks. Compressing Hydrogen may result in you shifting over to metal hydride storage, not sure if that can be handwaved into working for you.

 

[Tenacious-Techhunter]

Your “Jump Pusher” idea omits the means by which the Jump Bubble is maintained through the length of the trip... it has to be kept open with additional hydrogen. As such, I don’t think it would work, given current descriptions of Jump Drive technology.

 

[PsiTraveller]

If additional hydrogen was needed how do Drop Tanks work? They inflate the bubble of hydrogen and then jettison away. No extra hydrogen is available for the bubble, or there may not be, some ships may have some hydrogen in them (fuel for power plant ), but not the hundreds of tons needed at the start of the Jump.


e.g. 1000 ton ship Jump 4 needs 400 tons of hydrogen. If it has an empty fuel tank, aside from say 20 tons to run the power plant, and uses a 400 ton Drop Tank to start the jump, what fuel will it have to add to the Jump bubble?

 

[Condottiere]

Current rules are empty tanks; new ones indicate the jump drives consume no power during transition.

In theory, you could have a pusher; in practice, I think it would destabilize the transition.

 

[Reynard]

Mongoose is detail light on things such as the operation of the jump drive. The descriptor in the Core Book cites the power plant must create tremendous power for the jump drive. Drop tanks have pumps to feed the reactor and drive at normal rate just like the internal pumps. Soon after the jump is charged and contains the hydrogen component, moments before the jump activation, the tanks are blown clear. The hydrogen/energy field forms and the ship leaves real space. Highguard Page 38-39 describes the penalties using a drop tank and why it's normally a military assault option. Also, the navy has retrieval vessels for all the surviving drop tanks, your imperial tax dollars at work.

The drop tanks have nothing to do with the jump bubble. They, like the internal tank, deliver the fuel to the plant and drive and nothing more thereafter. Jump isn't instantaneous after the machines receive fuel which makes tank jettison possible but still hazardous as they must clear as the bubble forms. There is no need for more hydrogen once the bubble has formed.

A 1000 ton ship, J4 with 20 ton fuel in its 420 ton internal tank and a 400 ton loaded drop tank has enough fuel for one (1) jump. It will need to refuel the internal tank (the drop tank has been dropped) at the destination to jump again. If the internal was filled at the last system, it could jump again when prepped for another jump.

This is not a casual option for Travellers except in dire circumstances and those tanks have to be customized since no one outside the military normally requisitions them. The purpose is to have a fully operational jump ready at the destination. Seriously, what Traveller can afford to lose 4% of their internal volume for drop tank gear then have to buy a new set of the actual drop tank every other jump?

 

[PsiTraveller]

Sorry for the big block of text. I am pondering several ideas over the Drop Tank idea.

Reuse of Drop Tanks:
It depends on the Tech level of the drop tank. At TL 14+ the Drop Tank survives the Jump and can be reused. (pg 44 Highguard 1st edition), pg 39 of March version of Highguard in 2nd edition, the page number may have changed but I do not have the latest 2nd edition Highguard. So you definitely want to use higher tech gear. Losing a Drop Tank is very expensive.

Reynard:
Your example of the 1000 ton ship with 420 tons of internal storage space and a 400 ton Drop would have enough fuel for 2 Jumps, not 1, assuming both the internal and the Drop Tank were full in the dirst system. The first jump would use the Drop tank and the ship would be able to Jump 4 hexes. Once it arrived at the destination it would have the 420 tons of internal tank fuel left inside the tank (minus whatever the power plant used) and could jump again using the fuel from the internal tank. The Drop Tank would have been left behind in the first system. This is the useful part of Drop Tanks. You can cross rifts, or jump into a system with enough fuel to fight and not have to attack a gas giant as the first step in order to have the strategic fuel to run away, or you could jump again and bypass the system completely. Arriving with your fuel tanks full gives you options.

If the tank was <TL14 then you roll 2D and the tank survives on an 8+. If you roll less than 8 the tank is destroyed. This is the same for 1st and second edition. After TL 14 the Drop Tank survives and can be reused.

If your ship has large enough Jump engines you could take the Drop Tank through with you and not detach it. The added tonnage would be calculated as to what range you could actually jump. So the 1000 ton ship would calculate a Jump as having 1400 tons of volume and then calculate what jump the engines could actually Jump make. This quickly gets messy in terms of calculating jump rate and fuel usage. There may be a problem in trying to jump Drop tanks without having extra fuel on board.

example for 1st edition: 1000 ton ship wanting Jump 4 would use type P engines. If you used Drop tanks this would mean a 400 ton Drop Tank. If you wanted to Jump with the Drop Tanks still attached the chart says Type P engines can jump 3 at 1400 tons. But 1400 tons times 3 is 520 tons of fuel, which means the 400 tons of Drop Tank would not be enough fuel to take the Drop Tanks along. You could go with Type R engines that gives Jump 4 at 1000 and 1400 tons, but the 520 tons of fuel seems problematic.

the same problem seems there for 2nd edition. You take the percentage of engine vs tonnage to give maximum jump distance for the engine size. The problem is getting enough fuel.
You could go to Jump 2 and take 280 tons of fuel from the Drop Tank and take the tank with you. (1400 tons *10 percent is 140 tons times 2 for 280 tons needed to Jump 2).

The moral of the story is to make sure you have enough fuel capacity on the ship to feed the 10 percent of total volume you want to move times the distance you want to move it.

The merchant applications of this are even better than the military applications. This is especially true in 2nd edition. With any luck I will be using the JTAS to publish exactly this. Stay tuned.

 

[Reynard]

"but I do not have the latest 2nd edition Highguard."

June edition: "When a drop tank is used and jettisoned, roll 2D. On 8+, the tank survives the ejection process and can, in theory, be retrieved and reused. Otherwise, it is destroyed by the expanding jump bubble or warped by the jettison explosion."

"Your example of the 1000 ton ship with 420 tons of internal storage space and a 400 ton Drop would have enough fuel for 2 Jumps, not 1, assuming both the internal and the Drop Tank were full in the dirst system."

Your example mentions there's only 20 tons fuel (maneuver) internal but the drop tank is full. That's my reference. I was elaborating on what you described. The ship would only have enough for one jump and fuel to maneuver once at the destination.

"If your ship has large enough Jump engines you could take the Drop Tank through with you and not detach it"

Drop tanks are in addition to the ship's tonnage not part of the overall tonnage. However, the tonnage for the pumps and couplings are actually permanent and internal to the ship. A ship can maneuver with drop tanks at a lower thrust but the tanks make the Jump impossible unless you intentionally add the tonnage of those tanks as part of the original design which is silly because you might as well add that much more fuel internally. And why would someone add a larger Jump drive just to carry external fuel permanently?

This is why fudging the design system is ludicrous.