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Building Bridges

One appealing aspect of Traveller has always been the freedom for a small band of intrepid characters to strike on their own independent adventures. A key aspect of this freedom is the availability of a small starship – just the right size for a band of adventurers. The ships that are generally available to characters are all in the 100-200 ton range, notable Scout/couriers and Free Traders.

In the Book 2 design sequence (and High Guard, for that matter) a ship requires a bridge occupying 2% the total ship mass, with a minimum size of 20 tons. It makes sense that there be some lower limit – this tonnage presumably entails more than just the physical volume needed for the bridge, but also include items such as the ship's avionics and other control features. Unfortunately, this minimum increasingly penalizes ships below 1000 tons – the very ships that serve as the focus for so many adventures. And the 20 tons seems an odd and arbitrary lower limit. A 100 ton scout ship with a crew of 1 requires the same volume of control systems (including bridge space) as a 1000 ton, jump 5, craft, with its 205 tons of drives and the requirement for a pilot, navigator, medic, and 6 engineers.

Trading computing power for bridge size

At one point I designed a small ship with a large jump capability, thus necessitating a large computer. This made me pause to consider - if I have such a large computer, why can't it help with some of the control requirements? MegaTraveller addressed this to one degree by introducing Control Points, and allows quality equipment to reduce the number of required crew. My approach uses larger computer sizes to reduce the minimum required bridge size.

To compute the required minimum bridge size, simply divide 20 by the square root of the computer model number, rounding to the nearest whole number.

Computer Factor  1  2  3  4  5  6  7  8  9
Minimum Bridge  20  14  11  10  8  8  7  7  6

Notes: The determining factor is the actual computer model number, not the variant. So a model/1, model/1bis, and model1/fib are identical for this consideration.

So what does this accomplish? It gives a little breathing room to small ships that try push the envelope, which tend to be the ones most interesting to player characters, as well as those most punished by this design limit. This flexibility comes at a high cost – but this is a cost that has other benefits (like driving a larger jump drive), and can justify this reduction. This never surpasses the requirement that 2% of total mass be allocated to the bridge, so as a ship approaches 1000 tons, any potential benefit from this method fades away.


Our intrepid band of adventurers has been quite successful, and are looking to upgrade their scout/courier ship - for discussion sake let's assume they own the ship and can therefore do what the wish with it. For 9 MCr they can purchase and install a model/2 computer to replace the model1/bis that came standard. The model/2 computer takes an additional ton of space on the ship. But by installing this larger computer, the new required minimum bridge size is now 20*1.41 (square root 2) or 14 tons. The adventurers have a more capable ship, and have recovered 5 tons of space as well. Anyone who tells you that a scout/courier, with its paltry 3 tons of cargo space, can't find a use for this extra space isn't being serious.


Computers are expensive! The maximum tonnage reclamation on a computer replacement is 8 tons – replacing a model/1 (one ton + 20 ton bridge) with a model/5 (8 ton bridge + 5 ton computer), for the cost of 45 MCr! Slightly higher reclamation rates are available by applying the bridge reduction to existing designs.

In order to claim the bridge reduction, the existing bridge must be rebuilt, for the normal cost of MCr .5 per 100 tons of hull - the smaller bridge is more advanced, so it's cost is still computed on the total hull tonnage. This refit will probably take a month or two at a class A or B starport. Once completed, there is no going back to a smaller computer without restoring the larger bridge. Of course, there is no requirement to reclaim space with a reduced bridge size, but the refit cost is insignificant next to the cost of the computer.

Impact on standard book 2 designs

Type S scout/courier
No effect, as it mounts a model/1bis.
Type A free trader
No effect, as it mounts a model/1.
Type R subsidized merchant
No effect, as it mounts a model/1.
Type M subsidized liner
The model/3 computer permits a bridge reduction to 11 tons. Since 2% of 600 tons is 12 tons, that is the minimum bridge size, to the Type M is able to recover 8 tons of bridge space.
Type Y yacht
No effect, as it mounts a model/1. Type C mercenary cruiser – the model/5 computer permits a bridge reduction to 8 tons, but the ship's 800 ton displacement requires a bridge no smaller that 16 tons, permitting only 4 tons of bridge reclamation.
Type T patrol cruiser
The patrol cruiser's Model/3 computer equates to an 11 ton bridge. This is larger than 2% of the ships mass (8 tons), so this ship qualifies for the full bridge reclamation of 9 tons.

Benefits of computer size

There are several benefits to a larger computer. The first and most obvious benefit is a computer can only control a jump equal to the computer rating (/bis models can control a jump one level higher than their rating.)

The second benefit to a larger computer is it will make their ship more effective in combat. If using high guard for combat, remember that the difference in firer and target computer levels is used as a die-modifier (DM). When using book 2 combat, most combat DMs come from having specific computer programs loaded – so a larger computer permits more beneficial DMs. Remember that the model1/bis (runtime capacity 4/storage 0) on a scout/courier has 4 spaces worth of programs loaded and active for the entire duration of a combat turn. The model/2 computer has 9 spaces worth of programs loaded, with any 3 active at a time, and these 3 can altered every _phase_ - permitting much greater flexibility in offensive and defensive actions. In general, larger combat DMs come from larger computer programs, which in turn require larger computers.

The third benefit of a larger computer fits into the role-playing aspects – Book 2 makes the briefest mention of the "Library" program, which contains local information. This should be a beneficial resource for any group of adventurers – and is a useful mechanism for a referee to feed clues and information to players.

Of course, this is strictly "by the book" computer use, but if you have thrown out the basic computer capacity rules, then hopefully you have replaced them with something that still acknowledges that a bigger computer is better – in which case the premise, if not every detail, still applies.