[Spaceships] simply fuel math...

[TGLS]

Originally Posted by hal

if you have 5 and 2/3rds of a tank, does this get the full 1.2 modifier? If you have 8 and 2/3rds of a tank, do you get the full 1.4 multiplier?

OK, if you want something more accurate, but more fiddly, then I think this is right. Take the natural logarithm of 20 divided by 20 minus the number of fuel tanks and divide by 0.05 (ln(20/(20-tanks))/0.05). This gives you the effective number of fuel tanks for that particular drive, so calculate your delta V from there.

Aside: The multipliers given in the book exist to approximate the rocket equation's effect on Delta V (i.e. higher proportion of propellant, higher delta V). However, they do seem to error on the low (but occasionally the high). For example, 19 tanks would have a multiplier of 3.15 according to my equations, but it gets a multiplier of three. On the other hand, 6 tanks should have a multiplier of 1.18 according to my equations, but it gets a multiplier of 1.2.