Salvage ships and Jumping calculations

[PsiTraveller]

Basic question for the board because I cannot find the simple description of how the jump drive works.

Assume TL 15 ship so Drop Tanks do not get destroyed and no minus on Jumping with a Tank.

This is on page 13 of Highguard:
The fuel tankage needed for a jump drive is related to the size of the ship and the length of the jump, as follows;
10% of the total tonnage of the ship, multiplied by the maximum jump score of the drive
The result of this is the number of tons that needs to be dedicated to jump fuel

Question 1:
First question is easy. I am looking for the description of how Jump drives work when Jumping a shorter then max distance.
Example: A 1000 ton ship with a J1 engine needs 100 tons of fuel to Jump 1 parsec. And 25 tons of engine (2.5%) + 5 tons
A 1000 ton ship needs a J4 engine and 400 tons of fuel to jump 4 parsecs, and 105 tons of engines (10 % of hull) + 5 tons.

How much fuel does the J4 engine need to Jump 1 parsec? Is it 400 tons as per the maximum Jump score of the Drive as the line in Highguard seems to indicate, or would it be 100 tons of fuel as a J1 ship would use?

Question 2: Can you build oversize Jump 1 Jump Drives?
The salvage ships and ships with grappling arms grab a ship and then Jump the ship back to whatever repair dock is available. Combined tonnage of the ship is the factor when doing calculations. So if a ship with J1 engines at only 30 tons of engine volume grabs a big ship it cannot jump since the percentage is below 2.5 %. So can you build a 1000 ton ship with 100 tons of internal fuel storage with 100 tons of Jump Drives? Fuel usage for the j1 Jump would still be 100 tons of fuel even though the Jump engines are bigger.


Question 3: What happens if a J4 ship with 400 tons of internal fuel storage and a Docking Clamp arm grabs a ship and wants to Jump?
page 45 Highguard
Docking Clamp
A docking clamp allows a spacecraft to carry another vessel on the exterior of its hull, typically a small craft such as a ship’s boat or fighter. This permits a ship to carry auxiliary craft without consuming valuable interior space.
A ship’s Thrust and jump capability must be recalculated when another ship occupies its docking clamp, using the combined tonnage of both ships. This will likely mean the manoeuvre drive will be operating at a lower Thrust and the jump capability may be reduced.

J4 requires the engines be over 10 percent of the tonnage. So if the ship had a 400 ton ship in its Docking Clamp the tonnage would be 1400 tons and the percentage of engines to total tonnage would be 7.5%, which would give a J3 capacity. So spending 400 tons of fuel would let the 1400 ton ship jump 3 parsecs.

But what if the ship only wanted to Jump 1 parsec? How much fuel would it need to use? Would the fuel needed be 140 tons? of 100 tons

Question 4:

A 1000 ton J1 Salvage ship wants to Jump 1. The salvage ship only has 100 tons of internal fuel. If the J1 salvage ship grabs the 200 ton ship can it jump? does it use 100 tons of fuel or does it need 120 tons of fuel somehow?
The 30 tons of drives the J1 ship would have would be able to move 1200 tons of cargo (30 tons is 2,5% of 1200), but would the ship need to get 20 extra tons of fuel from somewhere?

Question 5: Drop Tanks
Assume the 1000 J4 with 800 tons of Drop tank attached (yes it will look bloated, it is a rift crossing concept.
Using 400 tons of fuel for max Jump the 1800 tons of volume vs the engines would be 7.5% and allow a J3. This seems in line with how the old docking clamps worked in 1st edition, comparing engine size to Jump ratio. This seems different in 2nd in that the 10% or hull times max fuel usage would seem to show the ship would need 540 tons of fuel to Jump 3. This makes Salvage ships a problem because they would need some extra fuel depending on what size ship they were carrying.

Question 6 : Pushing limits.
Assuming 400 tons of fuel into a J4 engine lets you move tonnage until you fall below 2.5%. (that is, assuming salvage ships just use up their max jump rating of fuel and compare tonnage moved to engine percentage.)
Does this means a 1000 ton J4 salvage hauler could attach 3200 tons of ship, use 400 tons of fuel and Jump 1 parsec (105 tons of J Drive / 2.5%)

Does this mean that a 1000 ton J1 salvage ship could be built with 1000 tons of J1 engine and move the same tonnage J1 for 100 tons of Jump fuel?

 

[PsiTraveller]

And I am looking at ships in first edition like the Vulture Class armed salvage hauler (traders and gunboats pg 66), with 30 tons of engine and 108 tons of Jump fuel for a J2 jump, or the labourer class salvage ship on pg 64 with 55 tons of engine and 240 tons of fuel for a Jump 2

How would they function in a 2nd edition universe?

 

[AndrewW]

Jump drives use the fuel needed for the jump. So if you are jumping 1 just calculate the fuel for the total tonnage for J1, even if the drives can do jump-4 or whatever.

You can make the jump drive whatever size is needed for the job. If you need 400 tons of jump drive for the ship + whatever it is carrying go ahead, even if only 300 tons is needed for the ship without anything attached.

Grappling Arms only support 2 tons, or 6 for the Heavy Grappling Arms, so you aren't going to be grappling a very big ship with those and then jumping.

 

[PsiTraveller]

My mistake on saying grappling arms, I meant, and copied the text from Docking Clamp. Will go edit in the correct words

 

[AnotherDilbert]

Ha, this is funny. I think most of us "know" the answers so haven't looked for them or noticed their absence. I'll try to answer according to RAW.

Q1: Only thing I could find is:

Jumps of less than one parsec (less than three light years, or one hex) are possible, and count as jump-1 for the purposes of Astrogation checks and fuel expenditure.

So microjumps are defined, but fuel consumption for short jumps are not.

10% of the total tonnage of the ship, multiplied by the maximum jump score of the drive
The result of this is the number of tons that needs to be dedicated to jump fuel.

This is only a tank requirement, it does not really define how much fuel is expended in any given jump.


Q2:

Select the jump score you wish your ship to have and use the figure below as the percentage of the ship’s hull that the jump drive will consume, then add 5 tons.

It would seem you can only choose the Jump rating, then the tonnage is fixed. So, no?


Q3: A J-4 1000 dT ship attaches a 400 dT vessel. All calculations are now based on a ship of 1400 dT. Together they have J-4 * 1000 / 1400 ≈ 2.8. Together they cannot achieve J-3, but can achieve J-2. (J-3 would require 1400 * 7.5% + 5 = 105 + 5 = 110 dT jump drive.) 1400 dT and J-2 would require 1400 * 20% = 280 dT tankage.
The amount of fuel for J-1 is Q1 and the answer is undefined.


Q4:The jump capability is recalculated for 1200 dT. It needs bigger jump drive and bigger tanks. If you do not have an oversized jump drive you cannot jump. You would need 1200 * 2,5% + 5 = 35 dT jump drive. You should need more fuel, but since the fuel required or expended to jump is not defined anywhere, that is undefined. You still require bigger tanks according to p13.


Q5:A 1000 dT hull + 800 dT drop tanks is a 1800 dT ship for thrust and jump purposes. A J-4 drive for a 1000 dT hull is 1000 * 10 % + 5 = 105 dT. A J-3 drive for 1800 dT is 1800 * 7.5% + 5 = 140 dT. A J-2 drive for 1800 dT is 1800 * 5% + 5 = 95 dT. You can achieve J-2 without dropping tanks.


Practically salvage ships are not a problem. You need oversized drives, which you can achieve by choosing a big jump rating (if your TL allows it). You must install tanks correspondingly. Notice that p13 does not give you a choice, you need a specified amount of tankage.
So a 1000 dT J-4 ship has 105 dT jump drive and 400 dT fuel tanks.
If you grab a 333 dT object, you would need a 1333 * 7.5% +5 = 105 dT jump drive and 1333 * 30% = 400 dT tankage to achieve J-3.
If you grab a 1000 dT object, you would need a 2000 * 5% +5 = 105 dT jump drive and 2000 * 20% = 400 dT tankage to achieve J-2.
If you grab a 3000 dT object, you would need a 4000 * 2.5% + 5 = 105 dT jump drive and 4000 * 10% = 400 dT tankage to achieve J-1.
If your jump drive can make the jump your internal tanks are sufficient.


Edit, fixed a quite-tag.

 

[AnotherDilbert]

Jump drives use the fuel needed for the jump. So if you are jumping 1 just calculate the fuel for the total tonnage for J1, even if the drives can do jump-4 or whatever.

Yes, of course, but where in the rules is that stated?

You can make the jump drive whatever size is needed for the job. If you need 400 tons of jump drive for the ship + whatever it is carrying go ahead, even if only 300 tons is needed for the ship without anything attached.

Yes, of course, but where in the rules is that stated?

 

[AndrewW]

My mistake on saying grappling arms, I meant, and copied the text from Docking Clamp. Will go edit in the correct words

Any jump drive and fuel requirements are calculated on the total combined tonnage, doesn't matter if it's all one ship, docking clamps, drop tank or whatever. So if it's 1,000 tons of ships, that's how much fuel you need, if you have a 1,000 ton ship with another ship on a docking clamp that's 300 tons, calculate the jump fuel requirement for 1,300 tons.

 

[AnotherDilbert]

Jump drives use the fuel needed for the jump. So if you are jumping 1 just calculate the fuel for the total tonnage for J1, even if the drives can do jump-4 or whatever.

Yes, of course, but where in the rules is that stated?

I'm sorry Andrew, but I think this is somewhat important. I'm not trying to nitpick but how are new players to know these things if the rules don't tell them?

 

[PsiTraveller]

Fuel needed for a Jump depends on the size of the ship and the length of the Jump and is calculated as 0.1 tonnage Jump distance. A single Jump of that distance consumes that much fuel.

That is First edition page 107 Core book. I do not see that sentence in the second book. The description in the 2nd edition books could be read as a J4 ship needed to use its full amount of fuel every jump and not a lesser amount for shorter jumps. It is a minor sentence, and everyone who has played the game knows the calculations to figure out jump fuel, but it is not explicitly spelled out in 2nd edition.

And the editors may want to put in that fuel used is .1 total tonnage times the distance Jumped.
They may also want to add in the calculations for how far a ship carrying more then its normal tonnage can jump. 1st edition had the chart on page 108. Now you have the percentage chart in Highguard on page 11. Spell it out. Does the 5 tons added onto your Jump drive total mean that a 200 ton ship can carry 400 tons at Jump 1? Or do you calculate the engine percentage score after you deduct the 5 tons?

They may want to put in a section on overbuilding engines for increasing carrying capacity. A 1000 ton ship, 500 tons of which is Jump 1 Drive. Normally you would only need 3o tons (25+5). The extra tonnage is used to attach 4500 ton habitat and fuel modules to for 5000 ton totals to jump across a rift using 500 tons of fuel at a time. This could be how lower tech colonies make it across a rift. They build lower tech engines large enough to move the fuel they need to carry to make it across a rift.

I am just saying to spell the options out so newcomers who have never played can find the examples in the rules. I have 2 new players in my group and they do not have the years of old school Traveller to fall back on.

 

[AndrewW]

I'm sorry Andrew, but I think this is somewhat important. I'm not trying to nitpick but how are new players to know these things if the rules don't tell them?

I agree it needs to be in there.

 

[phavoc]

Agreed. The zeal for brevity often comes back to bite you on the ass. I still ja entry yet discerned the needs to "cut down" on the descriptions that 2nd edition seems to be heading towards. If anything the trend has been to ADD to the texts of gaming systems because electronic publishing has no real limitations on length, and the dead tree versions sell well enough at the 50 to 60 price points. Other gaming systems have no problem selling 400 plus page core books in hardback at this price point.

 

[PsiTraveller]

An example of common events in the rules gives readers a chance to see what happens in a game. An example of each calculation is good since it shows how the rule is used.

As for 400 page books we may not want to go that far, but an example of things online could be very useful. Roll up an example character for each profession. Give an example of psionic powers being used.
For spaceships give an example of ship design. Have a collection of user submited ships that have been checked for rules compliance.

I am running a game with a couple of folks who have never played Traveller before. So all the things that are in older versions are not known to them. They are looking at the game and not finding things as we try to shift from first to second edition.

 

[AnotherDilbert]

I am running a game with a couple of folks who have never played Traveller before. So all the things that are in older versions are not known to them. They are looking at the game and not finding things as we try to shift from first to second edition.

This is perfect as a beta test. Please note and tell Mongoose what they miss.