Newbie question - Jump travel and fuel consumption.

[Marikir]

Silly little question I just thought of.

Jump travel consumes 0.1 x tonnage x Parsecs travelled in fuel tonnage. This lasts for one week in Jump Space.

During that week, is the fuel for the ship's powerplant also consumed? Meaning that the actual fuel consumption for a jump is Travel + Half of the power plant's rated consumption for 2 weeks?

I'm assuming that this is what's meant, since the rules mention needing a minimum of 2 weeks of powerplant fuel for a Jump capable ship. Just wanting to clarify.

Thanks in advance. You guys have been pretty helpful for a Traveller newbie GM.

 

[tneva82]

Wow. Something I have managed to overlook. Yeah since I figure ship isn't frozen or something while in transit yes they would need fuel for the power as well so if there's fuel for 2 weeks better make sure you get to jump point and to refuel within week...

 

[hdan]

That's right - and it's another reason that misjumps can be so devastating. If your misjump lasts more than three weeks, you might not survive, or be able to make your way to a fuel source on the other side.

Of course if you misjump, you're likely to have bigger problems....

 

[tneva82]

That's right - and it's another reason that misjumps can be so devastating. If your misjump lasts more than three weeks, you might not survive, or be able to make your way to a fuel source on the other side.

Of course if you misjump, you're likely to have bigger problems....

Hum. Does the misjump take longer then? Say you make maximum misjump of 36 parsecs. Would that take 36/J-rating weeks? Or is the time random? (could it actually be shorter for some bizare reason?).

 

[Marikir]

That's right - and it's another reason that misjumps can be so devastating. If your misjump lasts more than three weeks, you might not survive, or be able to make your way to a fuel source on the other side.

Of course if you misjump, you're likely to have bigger problems....

Hum. Does the misjump take longer then? Say you make maximum misjump of 36 parsecs. Would that take 36/J-rating weeks? Or is the time random? (could it actually be shorter for some bizare reason?).

There's mention of a misjump lasting trillions of subjective years...so I'm assuming that this means that misjumps can cause time to pass for much longer inside the jump bubble during transit.

 

[kristof65]

Hum. Does the misjump take longer then? Say you make maximum misjump of 36 parsecs. Would that take 36/J-rating weeks? Or is the time random? (could it actually be shorter for some bizare reason?).

Somewhere in the old CT or MT material, there is buried some sort of random die roll for how long a mis-jump will typically last. Most of the time, it's a couple days longer than a regular jump.

However, there are lots of mentions of mis-jumps that have various effects, and as far as I'm concerned, give a GM justification to have a mis-jump last as long or as short as he/she needs it to.

 

[GypsyComet]

The "eternal jump" is also a representation of the Ghost Ship phenomonon. The old "Spacewreck" TTA book (among others) translated this to spacecraft, with the new ship full of people who jumped out for their destination, and arrived on time, but as a lifeless, worn, and ancient wreck.

Note that the Abyss Rift, sitting astride Vilis and Lanth subsectors, is noted for lost ship tales, ghost stories, and other horror stories.

 

[Infojunky]

Silly little question I just thought of.

Jump travel consumes 0.1 x tonnage x Parsecs travelled in fuel tonnage. This lasts for one week in Jump Space.

During that week, is the fuel for the ship's powerplant also consumed? Meaning that the actual fuel consumption for a jump is Travel + Half of the power plant's rated consumption for 2 weeks?

Well yes and no. Considering while in jump most of your big power eating systems are shut down, there really isn't any reason to run the plant at much above idle. Life-support and other basics yes, but they really don't eat that much power.

I'm assuming that this is what's meant, since the rules mention needing a minimum of 2 weeks of powerplant fuel for a Jump capable ship. Just wanting to clarify.

Needing two weeks for a safe jump does make sense, even with powering down during jump, you need to account for the time it takes to move from port to the jump point and back again, this can eat most of a ships fuel margin.

 

[kristof65]

Well yes and no. Considering while in jump most of your big power eating systems are shut down, there really isn't any reason to run the plant at much above idle. Life-support and other basics yes, but they really don't eat that much power.

When it comes down to it, there are really only two ways to look at it:

1. Power Plant consumes fuel at it's stated rated 100% of the time, whether you're in jump or not.

2. The jump fuel cost actually includes the time to run the power plant for that week.

Pick one that works for YTU.


There is the consideration of whether or not the powerplant consumes fuel based on power output, or at a constant rate. Many generators, for example, will burn the same amount of gas in an hour, regardless of whether or not you're running a transistor radio or an arc welder off of them. High end generators can reduce their fuel consumption based on current draw, but not completely. Which type do fusion reactors model?

Irregardless of what the fusion reactors do, you still are down to one of those two choices - all you're doing is fiddling with the explaination of why it's that way. IE, let's say a fusion reactor does have variable fuel use dependant on load. To "justify" #1 - constant fuel use - you only have to say that the J-drive uses all it's fuel to open the jump portal(s), but the power plant provides the power needed to maintain the jump bubble.

 

[Marikir]

Well yes and no. Considering while in jump most of your big power eating systems are shut down, there really isn't any reason to run the plant at much above idle. Life-support and other basics yes, but they really don't eat that much power.

When it comes down to it, there are really only two ways to look at it:

1. Power Plant consumes fuel at it's stated rated 100% of the time, whether you're in jump or not.

2. The jump fuel cost actually includes the time to run the power plant for that week.

Pick one that works for YTU.


There is the consideration of whether or not the powerplant consumes fuel based on power output, or at a constant rate. Many generators, for example, will burn the same amount of gas in an hour, regardless of whether or not you're running a transistor radio or an arc welder off of them. High end generators can reduce their fuel consumption based on current draw, but not completely. Which type do fusion reactors model?

Irregardless of what the fusion reactors do, you still are down to one of those two choices - all you're doing is fiddling with the explaination of why it's that way. IE, let's say a fusion reactor does have variable fuel use dependant on load. To "justify" #1 - constant fuel use - you only have to say that the J-drive uses all it's fuel to open the jump portal(s), but the power plant provides the power needed to maintain the jump bubble.

Those 2 choices were basically what I came up with in my head as being the crux of the matter.

I guess I'm going to have to decide how I want my TU to work. I'm leaning towards constant fuel drain. I guess I'm curious as to how others have looked at/dealt with the issue.

 

[Zowy]

I use option #2

 

[tneva82]

Needing two weeks for a safe jump does make sense, even with powering down during jump, you need to account for the time it takes to move from port to the jump point and back again, this can eat most of a ships fuel margin.

Well if you are looking to jump to Sol and move from there you are looking about 6h transit time with 1G acceleration...

 

[Valarian]

There's mention of a misjump lasting trillions of subjective years...so I'm assuming that this means that misjumps can cause time to pass for much longer inside the jump bubble during transit.

Now there's an adventure idea ... a ship arrives in-system after a week in jump with everyone dead of extreme old age.

 

[Infojunky]

Needing two weeks for a safe jump does make sense, even with powering down during jump, you need to account for the time it takes to move from port to the jump point and back again, this can eat most of a ships fuel margin.

Well if you are looking to jump to Sol and move from there you are looking about 6h transit time with 1G acceleration...

I only gave a supposition, jump masking can significantly increase this time, as can jumping to the closest GG to the main world for refueling.

I know Jump Masking isn't in the TMB, but is is discussed in numerous other places in the vast publication history of Traveller that I feel that it is a viable consideration.

 

[DPSteve]

Well yes and no. Considering while in jump most of your big power eating systems are shut down, there really isn't any reason to run the plant at much above idle. Life-support and other basics yes, but they really don't eat that much power.

When it comes down to it, there are really only two ways to look at it:

1. Power Plant consumes fuel at it's stated rated 100% of the time, whether you're in jump or not.

2. The jump fuel cost actually includes the time to run the power plant for that week.

Pick one that works for YTU.


There is the consideration of whether or not the powerplant consumes fuel based on power output, or at a constant rate. Many generators, for example, will burn the same amount of gas in an hour, regardless of whether or not you're running a transistor radio or an arc welder off of them. High end generators can reduce their fuel consumption based on current draw, but not completely. Which type do fusion reactors model?

Irregardless of what the fusion reactors do, you still are down to one of those two choices - all you're doing is fiddling with the explaination of why it's that way. IE, let's say a fusion reactor does have variable fuel use dependant on load. To "justify" #1 - constant fuel use - you only have to say that the J-drive uses all it's fuel to open the jump portal(s), but the power plant provides the power needed to maintain the jump bubble.

Sorry, that's something that just drives me nuts Irregardless is a double negative :twisted:

Ok, useless griping over, back to the topic at hand:

I don't agree that it boils down to those two options. It boils down to playability vs realism.

If we assume (and it is an assumption, with all the pitfalls included) that in Traveller powerplant technology is sufficiently advanced to throttle fuel consumption based on power draw, then there are more than options than your presented binary solution. The ship could very well use less power and therefore less fuel during jump. There's at least anecdotal evidence that suggests as much based on the tradition of Jump Dimming.

Having established the possibility of using less than 100% fuel consumption during jump, the question then becomes: how much book keeping do you want to do?

Do you make a list of all the various systems and note power usage, as a percentage of the whole, per system? Assign a basic percentage of fuel used during jump (85%? 90%? 50%?)

At some point the PCs will try to account for every drop of fuel in very innovative ways (I know, I'm one who would ). The easiest solution is to leave fuel consumption modifiers in the hands of the GM, who should be open to creative ideas.

 

[kristof65]

I don't agree that it boils down to those two options. It boils down to playability vs realism.

In the end, you still have the same basic choices - but you're right, there are actually three, rather than two like I originally stated.

1. The power plant draws it's stated rate 100% of the time, whether you're in jump or not

2. The power plant fuel draw needed during jump is drawn from the jump fuel

3. Somewhere in between those.

Options 1 & 2, no matter how you justify them, are the simplest solutions. Option 3 is going to require more decisions, and probably paperwork, while it is probably the most exploitable.

 

[Infojunky]

I don't agree that it boils down to those two options. It boils down to playability vs realism.

In the end, you still have the same basic choices - but you're right, there are actually three, rather than two like I originally stated.

1. The power plant draws it's stated rate 100% of the time, whether you're in jump or not

2. The power plant fuel draw needed during jump is drawn from the jump fuel

3. Somewhere in between those.

Options 1 & 2, no matter how you justify them, are the simplest solutions. Option 3 is going to require more decisions, and probably paperwork, while it is probably the most exploitable.

No there is at least one more, the one I postulated, the power plant draws at a much reduced rate when the big items are off. It is not as binary as you would like it.

 

[GypsyComet]

You have to increase complexity of the design system by a step (to have discrete numbers on power needs and generation) to have consistent numbers to apply to a "reduced usage" model. These don't have to be "real" numbers; an abstract measure as seen in CT HG is enough, but it has to be extended (even if the numbers are mostly zeros) to life support and similar. If you know your powerplant generates 36 EP at full blast, but the ship only needs 2 EP in jump (since the maneuver drive, screens, and weapons aren't in use), fuel usage in jump becomes easily figurable.

 

[kristof65]

No there is at least one more, the one I postulated, the power plant draws at a much reduced rate when the big items are off. It is not as binary as you would like it.

No, that's covered under option 3. It doesn't matter how much or how little you're changing the current draw, its still needs more complexity than option 1 or 2. It's not completely binary - you have an ON, OFF and SOMEWHERE IN THE MIDDLE choice. Each of those choices does lead to more choices, yes, but the option three probably has more choices in the chain that follows it.

In the end, for a GM, it still comes down to picking one of the three options I listed, then explaining the specifics.


I'm an Electronics Tech by trade, I deal with current draw, voltages, resistance, etc, on a daily basis. I know how complex it can get. I also do tech support, which means I also know that sometimes you need to distill things down to the simplest explainations to begin with. I got a little too simple in my first attempt with only two choices, but three pretty much covers everything.

 

[EDG]

I don't agree that it boils down to those two options. It boils down to playability vs realism.

If you want realism, then throw the whole "two weeks of fuel for the powerplant" idea out of the window - realistically, one ton of liquid hydrogen will run the power plant for years (if not decades). That being the case, the only reason you'd use hydrogen in large amounts over very short timescales must be because the Jump Drive itself requires it (to create and maintain the jump bubble for example).

There's been some discussion on the SJG boards about this: http://forums.sjgames.com/showthread.php?t=44453