GURPS Starships and volumetric designs...?

[Langy]

For drive systems, the acceleration in gravities is (motive thrust / engine weight) / 20.

Fuel usage in Vehicles is in gallons per hour. Multiply acceleration in gravities by 18 to get the delta-V in miles per second for a one-hour burn. Multiply the gallons per hour by the weight of the fuel then divide by 2000 to get the number of tons of fuel needed per hour of engine use.

Now we'll need to account for the size of the module - I recommend normalizing based on an SM+10 ship, which has 500 ton (1,000,000 pound) modules. That way you don't need to recalculate for every different ship size.

Delta-V per tank is: (module size in tons / fuel usage per hour in tons) * delta-V per Hour