Interstellar trading has to be planned well in advance.

The high cost and fairly long journey times mean that merchants cannot wait for the shipping to arrive before working out what is being traded for what. Deals and commodities are organised well in advance of the arrival of a cargo ship – the things being shipped out be waiting at the orbital station so that turn-around times are minimised – maximising profit for the shipping operator. Orbital dockside operators and specialised import-export companies are important in managing the process.

Therefore, the route and ports of call for any merchant ship must be planned for months or even years ahead.

Overheads for shipping companies are pay, ship maintenance costs and ship purchase repayments (or a leasing arrangement). Pay is significant, because each ship will have more than one crew to allow for leave, courses and the like (health an safety law requires crews to have a certain proportion of their working year planetside).

The Shipping

Merchant ships come in five main classes, based on the five main types of hyperspace drive (there are more, but this is a useful simplification based on the taxation categories used by the Imperial Revenue).

Ship Class

HS Drive

Typical Crew size


Kilo Tonnage

Operating Cost per tonne / day

Class 1000 Class 1


Smallest practical field size (small ones exist, but you can’t fit a ship capably of interplanetary journeys inside them).



Class 2000 Class 2




Class 3000 Class 3




Class 4000 Class 4




Class 5000 Class 5


Maximum field size.



Note: Tonnages are slightly changed from the rules because I’ve been playing with the sums a bit.

Operating costs vary for each class and depending on whether it is being leased or bought via a loan or is fully owned (having paid off the loan). Typically ship purchase loans are paid back over 10 years, and the vessel has an expected safe operational life of up to 24 years.

As shown above, smaller classes are slightly less cost effective than the biggest – but sometimes, especially where trade is developing, a trader can’t fill a Class 5000, so it makes sense to use a smaller ship, even if the cost per tonne is a bit higher.

This is especially so in the outer colonies, where trading corporations have complex transport logistic plans to maximise the use of their varied fleets. And for areas where the gains are more marginal, small, independent traders (who can only afford to buy the smaller ships, pick up the work).

Independent Traders are also able to cut their margins by lengthening the service life of their ships beyond the manufacturer’s recommendations, lengthening routine service and refit intervals, and pay crew higher rates (illegally) to forgo shore leave. Some even avoid paying ship tax – falsifying records by creating ‘ghost ships’ – that is more than one ship with the same registration and tax record.

So, the operational economics of shipping lines is such that they are vulnerable to crew pay fluctuations, fluctuations in ship purchase interest rates, fluctuations in refit and service costs (different systems charging different rates), fluctuation in government shipping tax, port taxes and the corner-cutting activities of semi-legal independents. Not to mention the cost of losing ships to pirates or STUFT duties.

This is covered, in many cases by the size of the multinational big shipping lines, who may own hundreds of ships, Universe-wide, and have huge financial influence and resources. Independents, obviously, go in and out of business regularly.

Some working assumptions about frequency of shipping

We assumed a while ago that the merchant starfleet was many times the size of the military one. My estimation is that there are probably around 1000 military vessels of various types. Let us say there are 30 merchants for every military, and if we assume an approximate stellar population of around 800 worlds, then there is an average of around 30-40 ships per world at any one time.

Lets assume the average journey time between worlds were 24 days – 8 days out to M25, 8 days HS transit, 8 days in from M25 and then 8 days loading/unloading (I have no idea if this is the case, but it’s in the right area).

Then, on any given day in The Universe at a given colony system:

– 10 ships in transit leaving,

– 10 ships in transit incoming,

– 10 ships in hyperspace somewhere and

– 10 ships in dock, loading / unloading.

It might be a bit less than this, because a proportion of the merchant starfleet would also be under repair or undergoing routine refits or maintenance – but it gives us a ball-park figure. It would be a quite a bit more in the Home Systems.

So..what about pirates

We have assumed that piracy is a common problem.

My assumption is that pirates operate under cover of local corruption, passing for legitimate merchants most of the time. I can’t see the economics of pirate bases out in the depths of space working (fun though they are to duff over).

When do they strike?

They have to match velocity to attack. If we assume a slight G advantage, this might be possible in a tail-chase out to the M25.

Hanging around on the M25 is pointless, since they couldn’t possibly detect an incoming merchant and intercept it in time. (A military ship might be able to do this, but not a pirate).

The best time is probably quite near an orbital station – but timing is vital if they are not to be intercepted by security forces.

So the factors are:

  • An incoming merchant is moving quite slowly and therefore easier to intercept, since it is at the end of a long decelerating burn.
  • The pirate can mask its intercept by apparently leaving the station on legitimate business.
  • If the intercept takes place, say 6-12 hours out from the station, the starguard (whose ships are no better than the pirate in agility) probably cannot get underway fast enough to catch the pirate before it reaches the M25. Also combats – boarding etc only takes 10-15 minutes – so even if the merchant gets out a signal of being under attack – the security forces couldn’t possibly intervene.
  • Of course, if the pirate had just left a station, it could be identified. Pirates might go to some lengths to disguise their ships.
  • Pirate ports are normal colony ports where a pirate can be refitted and supplied (and fence its goods) with no questions asked. These are usually corrupt places where the local authorities are in the pay of pirates. The ruling polity very probably doesn’t know that this is what is going on – because, after all, no governor is going to report his own corruption.
  • Pirates will therefore rarely attack ships leaving a pirate-friendly port, because that would make things difficult (though they might do so occasionally to maintain its cover – a system which is never attacked by pirates might be a bit obvious).
  • Pirates escaping a system might choose to take a high-risk vector to shake pursuit. Normally ships exit a system via ‘north’ or ‘south’ of the plane of the ecliptic. The closer to the POTE a course goes the greater the risk of catastrophic collision with a grain of sand. It is then a case of playing the odds – starguard will rarely risk all to chase down a pirate.
  • An important commodity for pirates would be merchant itineraries. These would change hands for large sums because it would enable pirates to do things like predict the arrival of a valuable cargo and possibly even do an M25 intercept.

Other Targets

In many colonial systems, there are also often asteroid mining operations and other things some distance from the relative safety of the colonial station. ┬áMining bases (which are usually small spinning orbitals) are permitted to carry point defences like multi-cannon – but routine interplanetary trips by miners and their cargos might be prone to raid from space pirates also. Very daring pirates might raid miner bases themselves.

Statistics – incidence of piratical attacks