P-Plant Fuel

[enderra]

Hm. Okay, even ignoring "game balance" as a reason, I get why jump drives require massive amounts of fuel (jump bubble).

But why does a p-plant need as much fuel as it does?

When I did - probably simplistic - research on the matter, I arrived at this: http://www.ccfe.ac.uk/FAQ.aspx#Day - now, Traveller ships clearly uses D-D fusion (since you can refuel 'em from any ocean), which iirc produces a lot less energy, but even so an A-class plant takes 1000 kg of fuel a week - ~143kg a day... and 1500 MW (at 1kg/day) is nothing to sneeze at.

I kind of assume that the true answer is "they made stuff up without research" but perhaps I am missing something, plus there might be an in-universe explanation. Anybody got any clues for me?

 

[rust]

I kind of assume that the true answer is "they made stuff up without research" ...

I think it is one of the cases where the authors of Classic Traveller
relied on faulty informations circulated at the time when the origi-
nal game was written, and later versions just copied the faulty da-
ta.

The exception is GURPS Traveller, where a new fusion power plant
comes with a sealed internal fuel tank which contains enough fuel
for about 200 years of operation, a much more plausible technolo-
gical assumption.

 

[enderra]

The exception is GURPS Traveller, where a new fusion power plant
comes with a sealed internal fuel tank which contains enough fuel
for about 200 years of operation, a much more plausible technolo-
gical assumption.

Yeah, that probably works better for D-D plants. Does G:T actually state what the power generation capacity of the plants are?

Thanks for the reply, I guess it could simply be a carryover (I don't have the LBBs on my shelf).

 

[rust]

Does G:T actually state what the power generation capacity of the plants are?

I do not have my GURPS Traveller material at hand, it is on
some backup disc, but I seem to remember that it does not
mention the actual power generation capacity.

 

[Jame Rowe]

The exception is GURPS Traveller, where a new fusion power plant
comes with a sealed internal fuel tank which contains enough fuel
for about 200 years of operation, a much more plausible technolo-
gical assumption.

Yeah, that probably works better for D-D plants. Does G:T actually state what the power generation capacity of the plants are?

Thanks for the reply, I guess it could simply be a carryover (I don't have the LBBs on my shelf).

This is why I am considering using the "2 weeks" or "4 weeks power plant fuel" as maneuver drive fuel, though there's a Signs & Portents article that rates consumption by tech level.

 

[Yatima]

Yeah, that probably works better for D-D plants. Does G:T actually state what the power generation capacity of the plants are?

The basic ship system in GURPS traveller just uses a single engineering module with a fusion reactor included regardless of the drives, weapons or other power using systems installed. No power output is listed.

In the advanced ship design system in GURPS Traveller Starships, modular components do have power requirements and a TL 10 Fusion plant is built out of 'power slices' that each put out 20 MW, for half a displacement ton and mass 4,000lbs. You select enough 'power slices' to meet your ship's power requirements, and figure the final size of the plant from this.

 

[F33D]

This is why I am considering using the "2 weeks" or "4 weeks power plant fuel" as maneuver drive fuel, though there's a Signs & Portents article that rates consumption by tech level.

I don't know if that would be any less nonsensical. The reactionless M-drives would be getting power from a fusion source also...

 

[enderra]

This is why I am considering using the "2 weeks" or "4 weeks power plant fuel" as maneuver drive fuel, though there's a Signs & Portents article that rates consumption by tech level.

That kind of works, yeah.

The thing, though, is that it clearly states that this is p-plant fuel, and fuel consumption is not dependent on m-drive rating (except indirectly, by requiring a p-plant of at least the same rating as the mdrive).

I haven't even dared look at m-drives. From all I can tell they are some sort of magic reactionless thrusters. If we accept that, then it's actually quite logical that they require power, not fuel.

I don't expect an rpg or rpg setting to be accurate, but I like plausibility and (internal) consistency. And playtested, for that matter. I find it surprising that I 'discover' these things five years after the game was published and there's nary an errata in sight (Not that I could do a better job, but then I am not being paid to do so.)

In the advanced ship design system in GURPS Traveller Starships, modular components do have power requirements and a TL 10 Fusion plant is built out of 'power slices' that each put out 20 MW, for half a displacement ton and mass 4,000lbs. You select enough 'power slices' to meet your ship's power requirements, and figure the final size of the plant from this.

Hm, thanks, so a fairly straight forward abstraction. 2tons of mass, 200 years of fuel included. Let's see, 200 years * 365 = 73t of fuel; divide by 75 to get to 20mw assuming that it scales directly... so just under 1 (mass) ton of fuel, though their volume is off. Too lazy to calculate if it could fit in Slush form, but they're surely cutting it close with their stats. And it ignores either the. as I understand, much lower energy efficiency of D-D, or the twelve-ish half life time of Tritium.

I don't know if that would be any less nonsensical. The reactionless M-drives would be getting power from a fusion source also...

Yeah, correct, it should be powered by the fusion plant.

 

[F33D]

Yeah, correct, it should be powered by the fusion plant.

Just for an idea. I justify the large PP fuel requirement as: 1) a small portion is actually used as fuel. 2) The majority is used as coolant to carry away the Fusion PP heat so the ship doesn't turn into a VERY hot oven.

That at least allows for use of the RAW and is plausible.

 

[GypsyComet]

Yeah, correct, it should be powered by the fusion plant.

Just for an idea. I justify the large PP fuel requirement as: 1) a small portion is actually used as fuel. 2) The majority is used as coolant to carry away the Fusion PP heat so the ship doesn't turn into a VERY hot oven.

That at least allows for use of the RAW and is plausible.

And is a fairly common solution among those who have been wondering about this question for the last twenty-odd years.

Note that TNE also dialed the power plant fuel way back (or rather, did it first), but used reaction mass for the M-Drive to make up the difference. Having to refill a big part of your hull with L-Hyd every two weeks is part of the Traveller vibe. You can change that, but something else needs to change as well, or you break the small ship economics very quickly.

 

[F33D]

And is a fairly common solution among those who have been wondering about this question for the last twenty-odd years.

Really? I've played in almost countless games over the last 30+ years on three different continents and have never seen that house rule. Good to know a few others have adopted it.

 

[dragoner]

"You can also burn hydrogen for water." (verbatim quote from Armstrong Hall propulsion engineer)

 

[GypsyComet]

And is a fairly common solution among those who have been wondering about this question for the last twenty-odd years.

Really? I've played in almost countless games over the last 30+ years on three different continents and have never seen that house rule. Good to know a few others have adopted it.

Depends on how many nuclear scientists were in your groups, I guess. The idea popped up mid-MT after a TML essay on what Traveller fusion most likely was and why it burned so much L-Hyd, followed by MT and TNE evaluations of ship thermodynamics. This led off to some of the earliest of the "can't hide in space" arguments, based on the capabilities of the VLA and Arecibo and the apparent conclusions that ships glow visibly.

(we can discuss the fallacies of "if it's on the internet then everyone knows it" at some other time.)

Personally, between using 90% of the PPlant fuel for cooling and the presence of gigantic thermos bottles on every ship (casually keeping L-Hyd in phase? Okay.) ship overheating should not be a problem.

 

[F33D]

Depends on how many nuclear scientists were in your groups, I guess.

Just one. And a JPL rocket scientist. Most of the rest being engineers of some type or another.

 

[enderra]

If you start considering cooling though, would expelling super-heated hydrogen even work - and if it does, would it cool the ships enough? The math is way too complicated for me, but I always assumed that we'd need a LOT of radiator surface for any sort of sci fi starship.

 

[F33D]

If you start considering cooling though, would expelling super-heated hydrogen even work - and if it does, would it cool the ships enough? The math is way too complicated for me, but I always assumed that we'd need a LOT of radiator surface for any sort of sci fi starship.

Radiator surface + coolant = better than just radiator surface.

 

[enderra]

Radiator surface + coolant = better than just radiator surface.

Right, but how effective can that sort of system be? And why hydrogen?

 

[F33D]

Radiator surface + coolant = better than just radiator surface.

Right, but how effective can that sort of system be? And why hydrogen?

Effective enough. Hyd because it is the most abundant element in the universe. You can pretty much always get it whether near civilization or not. You can use more efficient coolant gases. But, you can't always get them.

 

[phavoc]

Yeah, that probably works better for D-D plants. Does G:T actually state what the power generation capacity of the plants are?

Thanks for the reply, I guess it could simply be a carryover (I don't have the LBBs on my shelf).

Gurps:Traveller allows for larger and multiple power plants to be installed. Larger plants are available to offer more power to let energy weapons increase their ROF. And multiple plants to allow for combat damage that does not affect the fighting capabilities (till it reaches a threshold).

The energy weapons also have a power rating, so more powerful weapons do require more power from the powerplant.

And yes, there is a formula to calculate the Mw's produced, with higher TL plants being able to put out more power in a smaller form factor.

At least that's what I recall off top of my head.

 

[GypsyComet]

The amount of cooling needed is also tied to which set of megawatt numbers you decide to use. GT ship design has a lot of its ancestry in TNE's Fire, Fusion, and Steel, which uses MUCH lower numbers than the turret melting MegaTraveller numbers.