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Deck Cargo: Using External Pods For Increasing Cargo Space

This is a lightly-edited version of an article that was originally posted to the pre-magazine Freelance Traveller website in 2000. This edited form appeared in the July 2013 issue.

Before spaceflight, surface ships often carried extra cargo as “deck cargo”, lashed down on the deck instead of in the hold; later “container ships” carried their entire cargo stacked up on deck in weatherproof containers. Applying this concept to Traveller starships allows for more flexibility in ship design; with external “deck cargo” pods, a high-performance ship (such as the AH3 or AH4 Express Freighters or the AM3 Fast Packet Liner) can serve as a larger freighter at a reduction in performance, allowing tailoring of ship capacity and performance to the task at hand.

Cargo pods are available in 100, 500, and 1000-ton sizes as well as custom sizes fitted to particular ship classes; major shipping lines with fast ships usually keep a few in stock for emergencies.

To carry external cargo pods, a ship must be capable of Jump-2/2-G or higher, and must have special attachment points (“podpoints”) fitted, similar to (but not capable of use as) turret hardpoints. These podpoints cost MCr0.01/ton of ship (e.g., a 2,000-ton ship would require MCr20 to equip with podpoints).

When a ship has pods attached, its tonnage is increased by the tonnage of the pods; Maneuver and Jump drive performance is recalculated for the increased tonnage, rounded down. CER is recalculated for the additional capacity and cost of the pods and the reduction in jump number. The additional tonnage cannot reduce performance below Jump-1 or 1-G. (Thus, the lower of the jump rating or maneuver rating determines the maximum pod capacity. See the table on the next page.)


Maximum Additional Tonnage Calculations for Pod Cargo for Ships of Base Displacement T
Base Performance Formula for Maximum Pod Displacement (Unstreamlined pods) for Resulting Performance of…
Jump 1 or 1 G Jump 2 or 2 G Jump 3 or 3 G Jump 4 or 4G Jump 5 or 5G
Jump 6 or 6 G T5 T2 T T2 T5
Jump 5 or 5 G T4 T32 T23 T4 0
Jump 4 or 4 G T3 T T3 0 -
Jump 3 or 3 G T2 T2 0 - -
Jump 2 or 2 G T 0 - - -

Unstreamlined pods cost MCr0.1/ton; all pod tonnage is useable. With these pods attached, a streamlined ship is unstreamlined; the pods must be jettisoned or uncoupled to restore the ship’s streamlining. Any amount of unstreamlined pods may be attached to a ship (pods attaching to other pods), provided the additional tonnage does not reduce performance below Jump-1 and/or 1-G.

Conformal (streamlined) pods cost MCr0.11/ton; only 90% of the pod’s tonnage is useable. Conformal pods do not break a ship’s streamlining. The maximum amount of conformal pods that can be attached without breaking streamlining is 50% of the ship’s base tonnage.

The ultimate expression of this principle is the “tug-and-pod” (or the “World’s largest modular cutter”), where a high-performance “tug” without much internal cargo space tows many times its own size in cargo pods, much like a riverine “towboat” pushing a string of barges. Though unstreamlined when towing pods, a streamlined tug can detach its “barge train” and leave it in orbit when skimming fuel, reattaching afterwards.

Example: A Type TJ Frontier Transport (The Traveller Adventure, c.1983) is a 2000-ton, TL15, Jump-6/6-G version of the TL11 Type TI Frontier Transport, used by the Third Imperium's intelligence services as a covert fast courier. Costing MCr816 and with only 194 tons of cargo hold, the TJ is impractical as a freighter. Unless, of course, it’s used as a tug.

As a tug, a TJ could carry 2,000 tons of pods at Jump-3/3-G, 4,000 at Jump-2/2-G, and a whopping 10,000 tons of pods at Jump-1/1-G. At destination, just detach the pods for later unloading, skim fuel, replenish stores, and pick up another “barge train” of pods for the next stop.

Specialized Pods

Fuel skim pod: This is a conformal pod with fuel scoops and refining plant built in; it is usually used combined with internal collapsible/demountable fuel tanks to allow a ship to serve as a “skim-tanker” in military or paramilitary situations to refuel unstreamlined ships in the task force/convoy. Fuel skim pods cost MCr0.13/ton and can pack 90% of the pod’s tonnage in fuel.

Racks: Military ships (not first line warships, but transports and similar auxilliaries) use a special type of pod called a “rack” to haul smaller ships/craft externally with rapid launch capability. These racks incorporate umbilicals and pressurized boarding tunnels to allow full access to the externally-carried craft. Racks break a ship’s streamlining when attached.

Small craft rack: carries up to 900 tons of small craft—fighters, shuttles, landing craft; crews bunk in the main ship. All rack-carried craft can be launched in one turn. Counts as 1000-ton pod; MCr15.

SDB rack: carries three 300-ton Torpilleur SDBs, enabling a ship to act as an SDB transport/tender; SDB crews bunk in the SDBs. Counts as 1000-ton pod; MCr10.