#### PsiTraveller

##### Cosmic Mongoose

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?