Traveller: My 3I: Trade Network

Trade Network


My Spinward Marches Trade Map


(courtesy of the awesome )

  • dark green routes are the hinterland routes
  • purple are the long distance routes between alpha systems – these also overlay some of the hinterland routes
  • light green routes are subsidized by the Imperium for policy reasons (e.g. building up border systems)
  • yellow circles are alpha systems (and sub-sector capitals if different)


Trade Assumptions

1) Systems represent whole solar systems so from TL9+ onwards worlds can easily be self-sufficient in raw materials.

2) Interstellar shipping costs per ton per parsec are high so

  • it’s only going to be economic to ship low value goods a short distance, say one or two parsecs, and only to systems which might have demand in excess of what the system can produce itself
  • medium value goods are restricted in a similar way, say up to six parsecs
  • high value goods: tech, luxury items, rare materials, unique planetary items etc can be profitably transported long distances but only in large amounts to systems which have a high demand for high value goods i.e. rich, high population planets



Trade in Traveller will mostly revolve around the alpha planets.

(Defined IMTU as class A star port, pop 8+, TL 12+.)

1) The alpha systems have high value tech to trade for what they want.

2) The alpha systems might have a demand for common raw materials because they have already used up the easiest sources in their system so deep mined local copper might be more expensive than copper that is open mined on a nearby system and then shipped – as long as it is nearby.

3) Assuming that an alpha planet can always grow enough food to feed their billions even if it’s in vats or on orbital stations or whatever they might still consider “natural” food items as a luxury or preference especially things like meat and fruit so I can see alpha systems having a demand for those from nearby systems – again stressing nearby.

4) The alpha planets will provide the main market for high value goods simply because their population size and TL implies they will have a large market and lots of prosperous or wealthy individuals.

So the alpha planets are the main markets and provide the hubs of trade.



If you accept the conclusion then the nature of trade in the Imperium will resolve into three main categories:

1) Hinterland Trade

Each Alpha system will have a cluster of systems around them which are tied to that Alpha’s economy. The hinterland systems will generally provide something useful for tech.

  • very short distance, 1-2 parsecs, for low value goods
  • short distance, up to 6 parsecs for medium value goods

The clusters made up of an alpha and its hinterland would once have been the core of the many pocket empires swallowed up by the Imperium as it expanded.

2) Silk Road Trade

Long distance trade between the alphas. Ships plying these routes don’t need to trade with the systems in between so these routes generally take the form of truck stops with an orbital refueling station by an outer gas giant or ice planet. The hub to hub ships just jump in, dock, refuel and do maintenance checks at the space station then jump out again. They only stop to unload when they reach the destination. Silk road truck stops will generally have a small 3I naval base for protection – like a Roman fort.

3) BackwaterTrade

Most everywhere else will have relatively low volumes of trade providing a living for Book 2 type subsidized merchants and Free Traders.



The alpha planets will often have orders of magnitude more people, GDP, tax etc than the rest of their sub-sector so not only will they both physically produce the fleets and provide the revenue to support them – so in terms of fleets – the bedrock of the Imperium – the alpha planets are what matters.

More specifically what matters in order
1) alpha planets
2) routes between the alpha planets
3) border fortress systems
4) alpha clusters
5) everywhere else

This leads to my 3I being split into three layers

  • there is a big ship universe of dreadnoughts and megacorporations comprising all the alpha systems and the silk road systems linking them
  • there is a medium ship universe in the hinterland systems of each alpha cluster
  • there is a small ship universe everywhere else where the 3I is rarely seen

(where small <= 1200-1600, medium <= 5k dtons, big > 5k dtons)


Which systems are which?

You could do it the GURPS way of giving systems a trade value based on their world stats but I think the potential self-sufficiency of systems and the consequent randomness of whether or not a system has something worth selling to an alpha makes a random element to trade value both plausible and potentially more interesting so IMTU I’m going to treat the canon star port class as the indicator of trade value i.e. if they built it there was a good reason so:

1) Alpha Systems: the alpha systems are defined as class A, pop 8+, TL 12+ (and sub-sector capitals)

2) Hinterland Systems: non-alpha systems with A or B star ports within 6 parsecs of an alpha system are assumed to have something to sell to the alpha in exchange for tech and are part of that alpha’s hinterland cluster

3) Exotic Systems: A or B systems outside of an alpha cluster (more than 6 parsecs) will generally have an exotic explanation. It could be something shady, historical or unusual like the system is being actively built up by the Imperium for some reason with regular colonist ships from the core

4) Backwater Systems: C, D and E systems are assumed to not have much anyone else needs and so have a low volume of trade serviced by Book 2 type ships

5) Silk Road Truck Stops: systems that make convenient refueling stops on the silk road.

6) Hinterland Truck Stops: systems that make convenient refueling stops on hinterland routes.


Example: Glisten sub-sector

1) Glisten is an alpha system.

2) Mertactor, Mille Falcs, Egypt, Overnale, New Rome, Aki, Weiss, Dobham are all hinterland systems and part of Glisten’s cluster

3) Romar, Bendor, Squanine, Ffudn are both hinterland systems and silk road truck stops

4) Mithras, as a prison planet is part of Glisten’s hinterland also

5) Grote is an exotic exception system – it could be a system being actively built up by the Imperium as a border fortress and link to District 268 or something odd / shady.

6) Aster, Melior, Craw, Horosho, Wurzburg, Lydia, Centry, Bicornn, Crout, Tirem, Caledonia are backwaters

7) Callia, Sorel, Tsarina, Windsor, Trane, Inthe are backwaters and hinterland truck stops

8) Marastan is a backwater and a silk road truck stop

  • systems like this are part BSU and part SSU and will generally have a commercial orbital station which services the passing merchant ships and small ships linking to the planet itself. Players jumping into the system might see lots of big silk road freighters and lots of patrolling fighters between the naval station and the jump points but very little traffic near the main planet.


Ship Encounters

Alpha Systems
  • very busy, lots of colonized planets and moons, lots of habitats, masses of internal traffic plus lots of large, medium and small interstellar traffic. Lots of planetary defenses – especially around fuel sources. Naval ships up to dreadnoughts. Silk road patrol ships.
Hinterland Systems
  • less busy, medium and small commercial ships, medium naval patrol ships.
Backwater Systems
  • quiet, small commercial ships, belters, scouts, small naval patrol ships.


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