Would this work?

[The Thing]

It's amazing that a jump drive takes up so little space on a ship, really. I mean, a jump3 drive takes up 4% of a ships volume, that's only twice as much as a jump1 and gives triple the jump range.

The bear is the fact the jump fuel takes 10% of the volume per parsec, so a jump3 engine with fuel takes up 34% of a ship's volume as opposed to the 12% that a jump 1 takes...

Anyway, I was thinking of a ship with some special modifications to it that took advantage of a jump drive's really tiny volume need.

Now picture this with me here: We have what appears to be a beyowulf class ship, but she has a jump3 engine. Her cargo holds are modified to allow the crew to quickly convert them from cargo to fuel in a few hours.

So for a jump1 run, no problem, use the ship as is.

Have someone who needs cargo delivered at jump2 and is willing to pay for it? Convert one section of the modified hold to a fuel tank and you're a jump2 ship.

Someone needs desperately to get somewhere at jump3 and has an imperial credit voucher? Convert both modified hold sections to fuel tanks and plot a jump3 course.

This might cost a bit, but it could give a regular beyowulf some serious flexibility that could give it an edge. The problem I see is that if it were feasible and cost effective every freaking beyowulf in the galaxy would have been converted over to it, so I have to wonder why they haven't.

Any ideas on why? Or was this just a great idea the game writers missed and a player picked up?

 

[Icosahedron]

Isn't this what collapsible fuel tanks do?

 

[Andrew Boulton]

Yup. Standard option since MT.

 

[Captain Midnight]

Isn't this what collapsible fuel tanks do?

I thought it was "demountable" fuel tanks, instead of "collapsible" ones; I know GT makes the distinction. The difference is that the demountables come with enough pumps and structural supports and everything else needed to allow their tankage to be included with the integral ship's tankage, and they are a pain to install and remove. With collapsibles, you have to pump it over to the main tankage before it can be used, so you wind up having enough fuel to do a second jump, but you have to do it as two jumps of shorter length instead of a single longer jump.

There's also the question of whether the additional flexibility is going to justify the loss of revenue from the space required for the bigger jump drive and the folded-up tanks, in addition to the initial cost of the tanks and drives. Increasing the jump by 1 for a 200-ton ship takes two more tons of jump drive, and even after discounts for standardization and quantity, that's going to run you at least an extra 7 MCr.

The GM gets to decide if there is enough call for extra jump capability to economically justify the decision, but if there's that much demand, I'd expect J-3 shipping to already exist.

 

[Plankowner]

CT allowed both versions. Book 5 I believe

Collapsable tanks took up cargo space but didn't add to ship volume.
Demountable (drop) tanks did not take up cargo space but added to ship volume and you lost it at the time of jump.

 

[Andrew Boulton]

CT only offered drop tanks.

MT added dismountable and collapsible tanks.

 

[Captain Midnight]

CT allowed both versions. Book 5 I believe

Collapsable tanks took up cargo space but didn't add to ship volume.
Demountable (drop) tanks did not take up cargo space but added to ship volume and you lost it at the time of jump.

There's actually three different options, if you include drop tanks. There's the "collapsible" option, which you'd have to pump the fuel out of separately; there's the "interior demountable" option, which takes up cargo space, but can be included in the fuel required for a longer jump; and then there are "drop tanks", which are carried external to the hull and get emptied and dropped before going into jump.

 

[G. Kashkanun Anderson]

CT only offered drop tanks.

MT added dismountable and collapsible tanks.

I'm pretty sure that Trillion Credit Squadron added the collapsible tank option, although I don't have my book collection handy at the moment to make certain of that.

But assuming that's true, then collapsible tanks count as a CT offering, too.

Although when you think about it, it would be an incredible feat of nanotechnology to create a material pliant enough to be collapsible and yet impermeable enough to keep all that hydrogen from leaking everywhere.

 

[fredofmars]

CT only offered drop tanks.

MT added dismountable and collapsible tanks.

Actually it was CT. Trillion Credit Squadron (Adventure 5) added dismountable and collapsible tanks (as well as percentage based fuel purifiers).

 

[Captain Midnight]

Although when you think about it, it would be an incredible feat of nanotechnology to create a material pliant enough to be collapsible and yet impermeable enough to keep all that hydrogen from leaking everywhere.

Especially when you consider the efforts required to keep it in a liquid state, not to mention the low temperatures. Slamming it into a HeftyBag isn't going to get the job done.

 

[aramis]

CT only offered drop tanks.

MT added dismountable and collapsible tanks.

CT has demountable tanks install inside the cargo bay. See "In Search of Longer Legs" in the Traveller Adventure.

Bk5 allows external (fixed size) drop tanks.

 

[Hal]

The thing to remember - with regards to the original poster's first post...

When using a Jump-3 engine in a ship that routinely makes a J-1 run, you will discover that you've added on the extra cost of the jump drive you rarely get use out of. Put another way? You're paying for a jump 3 engine regardless of whether you use it in Jump-1 mode or Jump-3 mode. The real issue there isn't whether or not you can use collapsable tanks or not - but whether you can make the payments or not.

 

[R_Chance]

It's amazing that a jump drive takes up so little space on a ship, really. I mean, a jump3 drive takes up 4% of a ships volume, that's only twice as much as a jump1 and gives triple the jump range.

The bear is the fact the jump fuel takes 10% of the volume per parsec, so a jump3 engine with fuel takes up 34% of a ship's volume as opposed to the 12% that a jump 1 takes...

I thought that would be 33% for a jump 3 and 11% for a jump one, assuming the power plants were rated at 3 and 1 respectively... most of the jump drive is storage for the energy derived from burning the jump fuel anyway. If I remember you could store incoming energy from hostile fire in your jump capacitors in High Guard if you had a black globe generator. I always figured you could jump with the energy your enemy was kind enough to "send" you... leading me to ponder powering up a ship (with a black globe) for a jump by firing on it and allowing it to keep it's fuel supply intact or even allowing for jump ships which didn't need huge fuel tanks

 

[far-trader]

...If I remember you could store incoming energy from hostile fire in your jump capacitors in High Guard if you had a black globe generator. I always figured you could jump with the energy your enemy was kind enough to "send" you... leading me to ponder powering up a ship (with a black globe) for a jump by firing on it and allowing it to keep it's fuel supply intact or even allowing for jump ships which didn't need huge fuel tanks

Won't work though, High Guard specifically stated that you still needed the fuel to jump. Presumably all the Black Globe will do is allow you to jump with a damaged or dead power plant. If it's dead it'll be a long, cold, dark, week in jumpspace hoping the emergency power holds out long enough (1D days in CT) to keep you alive.

 

[R_Chance]

Won't work though, High Guard specifically stated that you still needed the fuel to jump. Presumably all the Black Globe will do is allow you to jump with a damaged or dead power plant. If it's dead it'll be a long, cold, dark, week in jumpspace hoping the emergency power holds out long enough (1D days in CT) to keep you alive.

If I recall correctly (from the MT Starship Operators Manual from DGP) much of the fuel is used as coolant for the fast burning fusion plant at the heart of the jump drive. No fast burning plant, no need for coolant. The rest is just energy expenditure. The energy is pumped into the jump grid which is in the hull of the ship in a specific pattern for the jump distance / direction.

 

[Maccat]

I find the added cost and how hard it is to have profitable ships usually means no-go on the extra capacity. I think there were (somewhere) dismountable/collapsables that would act as regular tankage, could be dismounted and collapsed/stored at 1/4 tonnage. sounds like what you're suggesting.
Nearest thing to what you describe to my mind is a "tug" concept (or LASH? some variant thereof), where there's a high jump capacity vehicle, and it carries others (at reduced jump capabilty) One big reason for that w/ LBB2 is crew requirements, and say a 400&600t hull are cheaper than a pure 1000t one. The idea is that "alone" the tug has high power drives, when combined with other hulls, or say a buncha 30t cutter modules, it's added tonnage reduces the drive capacity, so it becomes say J1@ 600t cargo, J2@ 400t cargo, etc. The jump tug or cargo thing in fighting ships is that, loses 1xJn per 1kt module. Alone is J6. Or the Nostromo <s>
The capacitators if used alone i always thought they needed to power the ship "through" the jump also, and in the black globe stuff it stated that they can be drained at a rate equal to the power plant, so for J4 one would have a P2 and then capacitators to equal P2 (for a week, is 16.7t/EP for a week, verrrry expensive and heavy) but there's a lot of controversy it seems to me on that anyhow. I kinda like the idea for the XBoats at least, personally.

 

[Icosahedron]

The idea is that "alone" the tug has high power drives, when combined with other hulls, or say a buncha 30t cutter modules, it's added tonnage reduces the drive capacity,

This reminds me of a problem I've wrestled with on a number of occasions - non-jump tug boats (or dirtside grav cargo vehicles) need high-G M-drives to move their loads, but when unloaded they are capable of ridiculous speeds. Today's tugs/fork trucks are limited by gearing to low speeds - what could limit G-vehicles? I really don't want tugs and fork trucks running around at fighter velocities IMTU. Any ideas?

 

[rancke]

I thought that would be 33% for a jump 3 and 11% for a jump one, assuming the power plants were rated at 3 and 1 respectively... most of the jump drive is storage for the energy derived from burning the jump fuel anyway. If I remember you could store incoming energy from hostile fire in your jump capacitors in High Guard if you had a black globe generator. I always figured you could jump with the energy your enemy was kind enough to "send" you... leading me to ponder powering up a ship (with a black globe) for a jump by firing on it and allowing it to keep it's fuel supply intact or even allowing for jump ships which didn't need huge fuel tanks

ISTR that you needed the fuel anyway, but I could be wrong. The various ship-building rules are not compatible, and unless you assume that each set describes a whole different universe, there are a lot of the very early CT material that you have to cherry-pick. Many book 2 designs, would be illegal under HG rules if it wasn't for the rule tucked in somewhere in HG that grandfathered Book 2 designs (a really bad idea, IMO).

My approach is to say that there's one and only one OTU, and that the various Traveller rule sets are different, imperfect, simplifications of the OTU "reality". So when most of the rules sets say that jump fuel requires 10% of volume per jump number, I use that to 'conclude' that MT is wrong about jump fuel. Likewise, TNE is wrong about the standard maneuver drive, HG is wrong about power plant fuel consumption, QSDS is wrong about tonnage for carried subcraft, etc, etc. Obviously, this only works if you start with the assumption that there is only one "real" universe to describe.


Hans

 

[G. Kashkanun Anderson]

Won't work though, High Guard specifically stated that you still needed the fuel to jump. Presumably all the Black Globe will do is allow you to jump with a damaged or dead power plant. If it's dead it'll be a long, cold, dark, week in jumpspace hoping the emergency power holds out long enough (1D days in CT) to keep you alive.

I'm going to briefly put on this smelly old Rules Lawyer wig and point out that High Guard doesn't necessarily specify a need for jump fuel, just enough fuel. A fairly iffy argument could be made that the rule in question is simply pointing out that a ship without even enough fuel to run its power plant is going to wind up with a crew of dessicated popsicles when it comes out of jump a week later. Or, less ghoulishly, it can't even keep the computers on long enough to plot a jump.

I do agree, however, that it's more likely that the authors of High Guard intended the rule to be interpreted your way. I admit that I use this jump technique in a limited and very specific capacity IMTU, but I don't believe it was ever intended for the Generic TU. And then there's the anomalous existence of the Annic Nova, a ship which is capable of collecting enough jump energy solely through the use of its solar collectors.

But even with that, there aren't any official CT rules on how to build a ship like it. And that loophole is closed by the time MT rolls around, as far as I know.

 

[Captain Midnight]

This reminds me of a problem I've wrestled with on a number of occasions - non-jump tug boats (or dirtside grav cargo vehicles) need high-G M-drives to move their loads, but when unloaded they are capable of ridiculous speeds. Today's tugs/fork trucks are limited by gearing to low speeds - what could limit G-vehicles? I really don't want tugs and fork trucks running around at fighter velocities IMTU. Any ideas?

Other than traffic-control regulations? Not much, really.

The issue with spacecraft in Traveller is that they have acceleration, which is defined as a change in velocity. They accelerate until they decide to stop accelerating (which makes actual rocket scientists green with envy), and given the incredibly high capabilities of Traveller's "reactionless thrusters", they can get up to some amazing speeds in a fairly short period of time. You can start worrying about the risks of collision with some sort of floating micrometeoroid, or radiation hazards, or something else like that, but the inevitable consequence of big drives and comparatively low mass is high velocities and accelerations.

(Edited to add discussion of atmospheric limitations) This will be different in atmosphere, of course. There's a top speed at which the motive force is balanced out by the drag force (which increases proportionally to the SQUARE of the velocity), and there will also be stability issues to deal with. Couple that with governors put into control systems to prevent your grav-forklift from being operated in a fashion deemed "unsafe" by the manufacturer or whatever government has jurisdiction, and there's your justification for low-speed trucks. It's not a theoretical limit so much as an administrative one, but unless you can figure out a way to override it, that won't matter.