Ken Pick wrote a fantastic article for Freelance Traveller talking about using external mounts for cargo ships in Classic Traveller. I make heavy use of this in my own small ship settings. Ken’s rules for external cargo are fairly simple – special attachment points are added to the ship when it is built at a cost of MCr 0.01/ton of ship, and that’s it. I like the flexibility of this, but it does give large traders carrying external cargo a huge advantage: Bridge sizes. Book 2 specifies a ship dedicate 2% of its tonnage (minimum 20 tons) to the bridge and avionics, at a cost of MCr 0.5 per 100 tons of hull.

This means that a 2000 ton ship designed to carry 3000 tons of external cargo carries a 20 ton bridge at a cost of MCr 10, while a 5000 ton cargo ship carries a 50 ton bridge at a cost of MCr 25. Sure, the 2000 ton ship also spends an extra MCr 20 on external fittings, but it gains 30 tons of space!

I wanted to balance this out a bit, without getting too complicated, so I decided that in addition to Ken’s cost of external fittings, a ship that carries external cargo needs to have a bridge sized appropriately for the total tonnage it will carry. This makes small ships with external attachment points somewhat more expensive than a dedicated cargo ship of the appropriate tonnage, which seems an appropriate trade off for the added flexibility.

A cheap and easy example: The Duchamp class Scout/Courier

This is one of my favorite ships from my current setting. This is a small ship, small universe set in the year 2552. The standard 4-stateroom Type-S didn’t make a huge amount of sense, but a Scout/Courier equipped for a more flexible mission did, and this is what came out of that:

The Duchamp class Scout/Courier is an older TL A design that is still commonly seen. Designed in 2448 for long duration missions with little support, the ship is well suited for communications, survey, and exploration work. The Duchamp and all its variants feature large staterooms and comfortable living spaces, as well as convenient cargo holds with large belly lifts.

It’s pretty simple – a Type-S with only 2 staterooms, with the rest of the space as cargo. The cargo bay is split into two connected sections, with the idea that the ship can accept a 5 ton multi-mission payload specific for whatever mission it is on (which can include additional living space, if that is needed for the mission).

The two things to note on this is the addition of the external cargo fittings, and the increased cost of the bridge. This allows the ship to carry a 100 ton external module, reducing its performance to Jump-1 and 1 G acceleration.