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A Ton is both a measure of volume and a measure of mass or weight with two primary meanings:

A Displacement Ton (abbreviated as dTon or dT), a unit of volume is equal to between 13.5 and 14.0 cubic meters. It is derived from the volume of a ton (mass) of liquid hydrogen, the most common fuel used by starships.

A Ton (or tonne) (abbreviated as T) is a unit of mass equal to one thousand kilograms.

Additional Nomenclature[edit]

The foundation of the starship is the hull, into or onto which all other components are placed. Hulls are identified by their mass displacement (...expressed in tons; one ton equals approximately 14 cubic meters) and by their configuration.[1]

Ships may be very large and for convenience have their masses measured in kilotons (abbreviated to Ktons), a unit equal to 1,000 standard tons. Ships of at least a megaton (or Mton), which is 1,000,000 standard tons, are rare enough that "megaton" is not commonly used. "Gigaton" (or Gton), being 1,000,000,000 standard tons, and higher units are almost unheard of when describing ships. Typically when talking about objects in space of a megaton or more (and not talking about moons, planets, stars, or larger objects), one is talking about planetoids instead of ships. These prefixes derive from the pre-spaceflight Terran International System of Units as expressed in Anglic (which also gives tera for 1,000,000,000,000, peta for 1,000,000,000,000,000, exa for 1,000,000,000,000,000,000, zetta for 1,000,000,000,000,000,000,000, and yotta for 1,000,000,000,000,000,000,000,000). Most human races have ten fingers, so most of their mathematical systems use base 10, thus their native languages have exact translations of these prefixes, which has helped drive their adoption.

In the USP, a Tonnage Code is given. This is a power of ten of the tonnage; 0 = up to 1 ton, 1 = up to 10 tons, 2 = up to 100 tons, 3 = up to 1000 tons, and so forth.

Many Kinds of Tons[edit]

Ever wondered why ship entries often have wildly different tonnage measures? Here's why:

  1. Assay Ton
  2. Deadweight Ton
  3. Displacement Ton (dTon)
  4. Dry Ton
  5. Explosive Ton (Ton of TNT)
  6. Freight Ton
  7. Gigaton (Gton)
  8. Gross Register Tonnage (GRT)
  9. Gross Tonnage (GT)
  10. Harbour Ton
  11. Hydrogen Ton
  12. Imperial Ton
  13. Kiloton (Kton)
  14. Long Ton
  15. Longweight Ton
  16. Measurement Ton
  17. Megaton (Mton)
  18. Metric Ton (T)
  19. Net Register Tonnage (NRT)
  20. Net Tonnage (NT)
  21. Refrigerant Ton
  22. Register Ton
  23. Short Ton
  24. Shortweight Ton
  25. Water Ton

History & Background (Dossier)[edit]

The creation of starship deck plans is based on the assumption that one ton of mass displacement equals fourteen cubic meters. The standard displacement ton used for these calculations is derived from the volume of liquid hydrogen, the fuel source for most standard star faring vessels.[2]

The square grid scale used on most deck plans is 1.5 meters on a side. Clearance between decks is normally 3 meters. This means that two floor squares, extended floor to ceiling, equals four 1.5 meter cubes or nearly 14 cubic meters (four lots of 1.5 m x 1.5 m x 1.5 m = 13.5 cubic meters), or one ton. A 100 dTon starship would thus contain approximately two hundred grid squares within.[2]

Allowances of approximately + or - 10% were made in most areas to allow for better representation of specific parts of the ship and to cover various anomalies. For example, crew quarters call for four tons per sophont: the actual tonnage allocated on many plans is often less than that, but additional area is devoted to communal areas such as galley, mess, wardroom, and recreation areas.[2]

Also, a limited volume of passages has been added to some starships. Passages and access ways which have no other use may be safely added to a ship without affecting volume or displacement for construction purposes. These additional passages should amount to no more than an additional 10% of the ship's total volume.[3]

References & Contributors (Sources)[edit]

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