Straybow
SOC-14 1K
The Last Step, Long Delayed
We've had lengthy threads discussing stateroom sizes, life support costs, passenger rates, freight rates, and almost every matter of instellar trade and traffic (eg: Price-Fixed Travel, Far Trader cargo/Freight manifest questions). Almost, that is, except the mass vs volume problem.
LBB2 was obviously not written with the difference between displacement and mass taken into account at any point. In later supplements a standard measure was introduced at 14m³ per ton of hull, with the reasoning that 14m³ is the volume of a ton of liquid H2. That way fuel tankage is conserved from LBB2 design specs.
But setting the tonnage as LH2 displacement does mean all other ship features needed to be refigured, something that was never done. Some supplements and later versions of Traveller made a polite nod towards the duality of mass and volume, but still fell short of tackling the whole issue. Engine performance is based on dT hull size, not mass. An empty ship does not gain acceleration or jump advantages over fully loaded specs except by house rules. An overloaded ship isn't even considered because the rules assume that 1 dT cargo space is always the absurdly low 1 ton mass when fully loaded.
It isn't much of a problem when the focus is on adventuring funded by irregular speculative trading. Here we have people who are trying to make economic sense of the Traveller universe and it isn't working. Most standard ship designs are dreadfully unprofitable. The shipping model and commodities table in LBB2 don't fit the revised volumetric standard. No CT supplement or subsequent T version has introduced new trade values based on volume or new standards based on mass. Revising to account for mass is going to make every standard design profitable, even without per-parsec pricing on generic cargo lots.
Back in the 19th or 18th century the British decided to standardize certain shipping terms, and the ton was set at 100 cubic feet. The standard is still applied today, at least in the USA: the bed of a one ton pickup is roughly 8x6x2 ft; the bed of a "deuce-and-a-half" is about 250 ft³. The typical 53' US highway freight trailer is roughly 3100 ft³ and normally loads 30 tons.
Note that 100 ft³ per ton is intended as an average with allowance for dead space in typical loads. Almost anything can be packed in far more densely. A seaship captain will not endanger his seaworthiness by loading much above the rated total cargo capacity. An overloaded highway freight truck is at risk of tipping or internal load shifting, not to mention regulatory charges or fines.
One can hardly claim that the 14m³ "ton" is a convenient measure for use outside starship design specs. One hundred cubic feet works out to slightly under 3 m³ per ton. A 2.8m³ (0.2 dT) palette is going to be far easier to deal with. Note this would also explain why most shipment lots are multiples of 5 palettes. We can further assume that cargo bays are not simply open spaces of arbitrary dimension, but designed to accomodate standard palettes, braced stacks of 1dT, and standardized containers of some larger size (20/21st cen Earth containers are about 4dT).
With this concession to the consequences of the odd standard used for ship design we introduce access and stabilization overhead as a percentage of cargo space. Access is required for inspections, for damage control, and for situations where only a partial load is to be transfered. Stabilization is required to insure loads do not shift at any time, including emergency maneuvers without inertial compensation.
The less compact the design, the higher the overhead must be. A narrow cylinder might have less than 12.5% overhead, with the penalty that close inspection requires unloading the palettes. A wide open space might require 25% overhead, but allow easy inspection and less finicky loading. Large objects such as ATVs or oddly shaped items such as aircraft would incur additional overhead due to bulkiness not reflected in raw mass and volume figures.
A ship designed to handle containers will have internal gantries for loading, placing and unloading the containers. This is necessary even if the ship transfers cargos in orbit. Mid-sized cargo haulers will have light gantries or booms to handle palettes and the occasional container. Smaller ships may depend on portside longshore service, or acquire powered equipment and operators (necessary for planets with inadequate facilities). All equipment will take up space in the cargo hold, and detailed ship designing will require reasonable figures for mass and volume, load limits, and speed of operation.
With this increase in cargo capacity LBB2 freightage is at least double what the market will bear, and almost any standard design can be profitable at one third the listed freight charge with less than full loads.
We've had lengthy threads discussing stateroom sizes, life support costs, passenger rates, freight rates, and almost every matter of instellar trade and traffic (eg: Price-Fixed Travel, Far Trader cargo/Freight manifest questions). Almost, that is, except the mass vs volume problem.
LBB2 was obviously not written with the difference between displacement and mass taken into account at any point. In later supplements a standard measure was introduced at 14m³ per ton of hull, with the reasoning that 14m³ is the volume of a ton of liquid H2. That way fuel tankage is conserved from LBB2 design specs.
But setting the tonnage as LH2 displacement does mean all other ship features needed to be refigured, something that was never done. Some supplements and later versions of Traveller made a polite nod towards the duality of mass and volume, but still fell short of tackling the whole issue. Engine performance is based on dT hull size, not mass. An empty ship does not gain acceleration or jump advantages over fully loaded specs except by house rules. An overloaded ship isn't even considered because the rules assume that 1 dT cargo space is always the absurdly low 1 ton mass when fully loaded.
It isn't much of a problem when the focus is on adventuring funded by irregular speculative trading. Here we have people who are trying to make economic sense of the Traveller universe and it isn't working. Most standard ship designs are dreadfully unprofitable. The shipping model and commodities table in LBB2 don't fit the revised volumetric standard. No CT supplement or subsequent T version has introduced new trade values based on volume or new standards based on mass. Revising to account for mass is going to make every standard design profitable, even without per-parsec pricing on generic cargo lots.
Back in the 19th or 18th century the British decided to standardize certain shipping terms, and the ton was set at 100 cubic feet. The standard is still applied today, at least in the USA: the bed of a one ton pickup is roughly 8x6x2 ft; the bed of a "deuce-and-a-half" is about 250 ft³. The typical 53' US highway freight trailer is roughly 3100 ft³ and normally loads 30 tons.
Note that 100 ft³ per ton is intended as an average with allowance for dead space in typical loads. Almost anything can be packed in far more densely. A seaship captain will not endanger his seaworthiness by loading much above the rated total cargo capacity. An overloaded highway freight truck is at risk of tipping or internal load shifting, not to mention regulatory charges or fines.
One can hardly claim that the 14m³ "ton" is a convenient measure for use outside starship design specs. One hundred cubic feet works out to slightly under 3 m³ per ton. A 2.8m³ (0.2 dT) palette is going to be far easier to deal with. Note this would also explain why most shipment lots are multiples of 5 palettes. We can further assume that cargo bays are not simply open spaces of arbitrary dimension, but designed to accomodate standard palettes, braced stacks of 1dT, and standardized containers of some larger size (20/21st cen Earth containers are about 4dT).
With this concession to the consequences of the odd standard used for ship design we introduce access and stabilization overhead as a percentage of cargo space. Access is required for inspections, for damage control, and for situations where only a partial load is to be transfered. Stabilization is required to insure loads do not shift at any time, including emergency maneuvers without inertial compensation.
The less compact the design, the higher the overhead must be. A narrow cylinder might have less than 12.5% overhead, with the penalty that close inspection requires unloading the palettes. A wide open space might require 25% overhead, but allow easy inspection and less finicky loading. Large objects such as ATVs or oddly shaped items such as aircraft would incur additional overhead due to bulkiness not reflected in raw mass and volume figures.
A ship designed to handle containers will have internal gantries for loading, placing and unloading the containers. This is necessary even if the ship transfers cargos in orbit. Mid-sized cargo haulers will have light gantries or booms to handle palettes and the occasional container. Smaller ships may depend on portside longshore service, or acquire powered equipment and operators (necessary for planets with inadequate facilities). All equipment will take up space in the cargo hold, and detailed ship designing will require reasonable figures for mass and volume, load limits, and speed of operation.
With this increase in cargo capacity LBB2 freightage is at least double what the market will bear, and almost any standard design can be profitable at one third the listed freight charge with less than full loads.
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I'm trying to figure out what kind of guns you are buying for CR3000/ton. Supersoakers? 
Good one (not to detract from the serious bit). Super Soakers are my preferred weapon for fighting Evil Witches and small children, and if loaded properly Vampires and other undead, oops, wrong multiverse, we now return you to your regular game...
