A quick clarification. In standard Aurora there are Military Jump Drives and Civilian Jump Drives. In Newtonian Aurora there is just one type of FTL Drive but there is a multiplier you can use to increase the size of the drive (without affecting cost/crew) which ranges from 1x to 10x. The 'penalty' for larger multipliers was intended to create the same military vs civilian dynamic with a range in-between. The whole point of the Military/Civilian distinction in Standard Aurora was to prevent cheap large jump drives for huge military ships while allowing them for lower cost civilian vessels and I carried that principle into Newtonian Aurora. I also transferred the principle that jump drive cost is based on the square of the hull size, so 2x size = 4x cost (actually Size^1.75 for Newtonian Aurora rather than Size^2).

After reading John's comments, I looked again at my base assumptions. Newtonian Aurora is a very different game where FTL travel is essential and there is no easily available jump gate alternative for very large ships. Which means the small military vs large civilian FTL drive concept is no longer valid and therefore I don't really need the multiplier. I could just allow players to build larger jump drives based on a linear cost increase, regardless of whether the ship is military of civilian. However, civilian ships tend to be much larger than military ships of similar cost because the ratio of cost vs size of the components involved in civilian ships tends to be much lower. This means that jump drives for civilian ships would likely be a much greater proportion of their total cost, which isn't a good thing. Therefore John's second suggestion, which is to lower the cost of jump drives on a per ton basis as they get larger, would work well. Yes, this would allow very large military ships to have a much cheaper jump drive as a proportion of their total cost than in Standard Aurora, but very large military ships are expensive anyway so an Empire would be spending a lot of money to take advantage of this 'cheaper' option.

So lets look at some new numbers for calculating jump drive size and cost. Firstly, lets remove the whole concept of the multiplier. Secondly, the base cost can be calculated using square roots. After some playing around, I am considering:

FTL Drive Cost = (Sqrt(FTL Drive Size) * Sqrt(FTL Speed Multiplier) * Sqrt(FTL Squadron Size)) / 50

A few examples, using generally level 4 tech, which is FTL Drive Efficiency 8, Minimum Drive Size 500 tons, Speed Multiplier 10,000 and Squadron Sizes up to 7. The crew requirement is based on sqrt(Size)

**Survey Ship Drive**

Max Ship Size: 4,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x

Jump Engine Size: 500 tons Efficiency: 8 Jump Engine HTK: 2

Cost: 89 Crew: 22

Materials Required: 17.8x Duranium 71.2x Sorium

Development Cost for Project: 890RP

**Destroyer Drive**

Max Ship Size: 8,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x

Jump Engine Size: 1,000 tons Efficiency: 8 Jump Engine HTK: 4

Cost: 126 Crew: 32

Materials Required: 25.2x Duranium 100.8x Sorium

Development Cost for Project: 1260RP

The next two examples are the same size drive but with squadron sizes of four and seven respectively

**Cruiser Drive**

Max Ship Size: 16,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x

Jump Engine Size: 2,000 tons Efficiency: 8 Jump Engine HTK: 8

Cost: 179 Crew: 45

Materials Required: 35.8x Duranium 143.2x Sorium

Development Cost for Project: 1790RP

**Command Cruiser Drive**

Max Ship Size: 16,000 tons Max Squadron Size: 7 FTL Speed Multiplier: 10,000x

Jump Engine Size: 2,600 tons Efficiency: 8 Jump Engine HTK: 10

Cost: 270 Crew: 51

Materials Required: 54x Duranium 216x Sorium

Development Cost for Project: 2700RP

Next is a drive for a colony ship plus the same size drive with the minimum speed multiplier. I think the latter would probably only be worth it for journeys that involved relatively long in-system time and short FTL trips.

**Colony Ship Drive**

Max Ship Size: 20,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x

Jump Engine Size: 2,500 tons Efficiency: 8 Jump Engine HTK: 10

Cost: 200 Crew: 50

Materials Required: 40x Duranium 160x Sorium

Development Cost for Project: 2000RP

**Slow Colony Ship Drive**

Max Ship Size: 20,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 2,500x

Jump Engine Size: 2,500 tons Efficiency: 8 Jump Engine HTK: 10

Cost: 100 Crew: 50

Materials Required: 20x Duranium 80x Sorium

Development Cost for Project: 1000RP

Now progressively larger drives.

**Battleship or Freighter Drive**

Max Ship Size: 40,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x

Jump Engine Size: 5,000 tons Efficiency: 8 Jump Engine HTK: 20

Cost: 283 Crew: 71

Materials Required: 56.6x Duranium 226.4x Sorium

Development Cost for Project: 2830RP

**Large Freighter Drive**

Max Ship Size: 80,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x

Jump Engine Size: 10,000 tons Efficiency: 8 Jump Engine HTK: 40

Cost: 400 Crew: 100

Materials Required: 80x Duranium 320x Sorium

Development Cost for Project: 4000RP

**Huge Freighter Drive**

Max Ship Size: 160,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x

Jump Engine Size: 20,000 tons Efficiency: 8 Jump Engine HTK: 80

Cost: 566 Crew: 141

Materials Required: 113.2x Duranium 452.8x Sorium

Development Cost for Project: 5660RP

The above costing system will support the concept that really large freighters and colony ships will be more economical, whereas in Standard Aurora the advantage of building ultra-large commercial ships isn't very great. Commercial ships will generally become more expensive but this is a very different game with longer timescales for the building up of distant colonies so I don't think that is a significant problem.

Steve