One fact of interest to flesh out a setting is the number of starships flying around, both military and civilian. Of course, I could simply make up some numbers, but for Traveller, something a little bit more number based is appropriate.
I came up with a 3-step process:
1) Calculate GDP from UWP
The GDP of a planet depends on the tech level (TL), the trade code, and the population:
TL: Base GDP
0: 10,
1: 25,
2: 50,
3:100,
4:200,
5:400,
6:800,
7:1600,
8:3000,
9:3600,
10:4300,
11:5200,
12:6200,
13:7500,
14:9000,
15:10800
Trade code: modifier
"Ag": 1.2,
"As": 0.5,
"De": 0.7,
"Hi": 1.4,
"Lo": 0.6,
"Ga": 1.75,
"Ic": 0.8,
"In": 1.3,
"Na": 0.8,
"Ni": 0.7,
"Po": 0.5,
"Ri": 1.5,
"Oc": 0.8,
"Va": 0.6
GDP = base GDP times all applicable trade code modifiers times population
2) Calculate fleet size
The percentage of the GDP that is spent on the fleet depends on government type, starport type, and the interstellar situation:
Government type: fleet percentage
0: 0.4%
1: 0.8%
2: 1.0%
3: 0.9%
4: 0.85%
5: 0.95%
8: 1.1%
9: 1.15%
A: 1.2%
B: 1.1%
C: 1.2%
D: 0.75%
starport type: modifier
A: 1
B: 0.9
C: 0.8
D: 0.7
E: 0.6
X: 0.0
Interstellare situation: modifier
peace: 1
tension: 2
conflict (or conflict foreseeable): 10
total war: 50
Fleet budget = GDP times fleet percentage times starport modifier times situation modifier
Maintenance costs 10% of the new ship price per year, so after a long period without losses, a world can have 10 times the yearly fleet budget worth of ships.
3) Civilian trade volume
Potential trade volume depends on GDP and starport type
starport type: modifier
A: 2
B: 1
C: .8
D: .5
E: .1
X: 0
Potential trade volume (in dton per year) = GDP (in MCr) times 10 times trade volume modifier
Actual trade volume depends on whether there is a trade partner within a 4-hex radius.
Applying those numbers to a small political entity, the Democratic League of Progress (DLP):
Weblaan 0106 C676846-7 Ga Lo G
Pencearg 0107 C7B0646-8 Wü Dü Lo
Eegan 0109 C5A0646-9 S Wü Dü G
Ystaculien 0110 B9F9946-C R Li Hi Ni G
Lamess 0206 B263746-9 F Ni G
Gilrad 0207 D676646-3 S Ga Dü G
Mette 0208 D8E7646-7 Li Lo Ni G
Juger 0307 D6D6746-7 Li G
Trade of world Weblaan with trade potential: 8736000.0
Import:
Juger : 27660.0
Lamess : 267410.0
Pencearg : 5125.0
Ystaculien : 8435110.0
Gilrad : 137.0
Eegan : 281.0
Mette : 276.0
Export:
Juger : 17012.0
Lamess : 184842.0
Pencearg : 4103.0
Ystaculien : 8529379.0
Gilrad : 106.0
Eegan : 301.0
Mette : 256.0
Trade of world Pencearg with trade potential: 45864.0
Import:
Juger : 143.0
Lamess : 1291.0
Ystaculien : 40319.0
Gilrad : 2.0
Eegan : 3.0
Weblaan : 4103.0
Mette : 3.0
Export:
Juger : 73.0
Lamess : 823.0
Ystaculien : 39829.0
Gilrad : 2.0
Eegan : 13.0
Weblaan : 5125.0
Mette : 5.0
Trade of world Eegan with trade potential: 55036.8
Import:
Juger : 77.0
Lamess : 200.0
Pencearg : 13.0
Ystaculien : 54436.0
Weblaan : 301.0
Gilrad : 1.0
Mette : 9.0
Export:
Juger : 10.0
Lamess : 45.0
Pencearg : 3.0
Ystaculien : 54697.0
Weblaan : 281.0
Gilrad : 0.0
Mette : 3.0
Trade of world Ystaculien with trade potential: 338520000.0
Import:
Juger : 272963.0
Lamess : 1125290.0
Pencearg : 39829.0
Weblaan : 8529379.0
Eegan : 54697.0
Gilrad : 2662.0
Mette : 21443.0
Export:
Juger : 285366.0
Lamess : 1207068.0
Pencearg : 40319.0
Weblaan : 8435110.0
Eegan : 54436.0
Gilrad : 2654.0
Mette : 21286.0
Trade of world Lamess with trade potential: 1404000.0
Import:
Juger : 11078.0
Pencearg : 823.0
Ystaculien : 1207068.0
Gilrad : 55.0
Eegan : 45.0
Weblaan : 184842.0
Mette : 89.0
Export:
Juger : 9506.0
Pencearg : 1291.0
Ystaculien : 1125290.0
Gilrad : 81.0
Eegan : 200.0
Weblaan : 267410.0
Mette : 222.0
Trade of world Gilrad with trade potential: 2866.5
Import:
Juger : 22.0
Lamess : 81.0
Pencearg : 2.0
Ystaculien : 2654.0
Weblaan : 106.0
Eegan : 0.0
Mette : 0.0
Export:
Juger : 12.0
Lamess : 55.0
Pencearg : 2.0
Ystaculien : 2662.0
Weblaan : 137.0
Eegan : 1.0
Mette : 1.0
Trade of world Mette with trade potential: 21840.0
Import:
Juger : 66.0
Lamess : 222.0
Pencearg : 5.0
Ystaculien : 21286.0
Gilrad : 1.0
Eegan : 3.0
Weblaan : 256.0
Export:
Juger : 20.0
Lamess : 89.0
Pencearg : 3.0
Ystaculien : 21443.0
Gilrad : 0.0
Eegan : 9.0
Weblaan : 276.0
Trade of world Juger with trade potential: 312000.0
Import:
Lamess : 9506.0
Pencearg : 73.0
Ystaculien : 285366.0
Weblaan : 17012.0
Eegan : 10.0
Gilrad : 12.0
Mette : 20.0
Export:
Lamess : 11078.0
Pencearg : 143.0
Ystaculien : 272963.0
Weblaan : 27660.0
Eegan : 77.0
Gilrad : 22.0
Mette : 66.0
As can be seen, Ystaculien is the top importer/exporter, and can use only a small fraction of its trade potential because there are not enough trade partners.
Nonetheless, there are around two 10,000dton kilofreighters a day going in/out for Weblaan, and two per week for Lamess.
The total fleet budget is 65,000 MCr/year (it's peace).
Assuming no losses, the DLP has ships for 650,000 MCr.
This could be something like:
2 battleships (200,000dton, 150,000 MCr each) for 300,000 MCr
4 heavy cruisers (75,000dton, 50,000 MCr each) for 200,000 MCr
4 light carriers (15,000dton, 15,000 MCr each) for 60,000 MCr
10 escort ships (5,000dton, 3,000MCr each) 30,000 MCr
60,000 MCr worth of support ships and planetary defense ships
As far as volume of trade goes, GURPS Far Trader has the most commonly accepted answer among the Traveller Community. Far Trader used a gravity trade model where each world has a World Trade Number which you can use to calculate a series of Bilateral Trade Numbers. It pretty straightforward and generates reasonable maps (http://wiki.travellerrpg.com/images/2/2a/Spinward_Marches_Sector.pdf).
The World Trade Number calculation is found on page 11 of GURPS Far Trader. It based on adding two factors based on TL and Population. The TL factor can range from -.5 to 1.5 and the Population Factor can range from 0 to 4. Then there another chart which generates a number based on the type of starport in the system. This can range from +1.5 to -5.
The Bilateral Trade Number is based on adding the two world's WTN, and modified by distance. Trade Codes have a slight effect when it comes to Ag versus Na, and In versus Ni. It factors more at the cargo level.
As for economic output, Traveller 5 has defined Resource Units which measure the economic output of the world. It found on page 404.
Quote from: estar;935216As far as volume of trade goes, GURPS Far Trader has the most commonly accepted answer among the Traveller Community. Far Trader used a gravity trade model where each world has a World Trade Number which you can use to calculate a series of Bilateral Trade Numbers. It pretty straightforward and generates reasonable maps (http://wiki.travellerrpg.com/images/2/2a/Spinward_Marches_Sector.pdf).
I suspected that, but my GURPS Traveller stuff is in a box somewhere in the basement... ;)
Quote from: Pyromancer;935218I suspected that, but my GURPS Traveller stuff is in a box somewhere in the basement... ;)
Just buy the Far Future CD-Rom (http://www.farfuture.net/FFE-CDROMs.html) for $35. You want GURPS-2.
Or buy for it for $10 from Warehouse 23 (http://www.warehouse23.com/products/FFE30-6606).
Isn't all this covered in Trillion Credit Squadron?
Quote from: Xanther;935546Isn't all this covered in Trillion Credit Squadron?
Unfortunately, no.
I took inspiration from it, though, as well as from Striker.
TCS doesn't take TL into account, which is silly, and doesn't codify the adaptions for interstellar situation.
Hmmm probably why I once ginned up some rules myself. I recall using the US GDP and military spending to get an idea for what 300 million wealthy people could do. It's been a few years.
I don't know if I got it from a Traveler book or just made it up, but I took into account TL through currency, constant TL 12 credits.
Have you also tried the Citizens of the Imperium website? These questions have been raised and various answers provided over the years.