Starship Construction in Mongoose Traveller

ONE aspect of the Classic Traveller RPG that I love is the ship construction rules. Not only can you build a ship for roleplaying adventure but one could even build fleets of ships. The Classic Traveller adventure Trillion Credit Squadron lets players design and build whole fleets.

In keeping with Traveller technology rules, different tech levels (TL) limit what one can build. I have been searching the Mongoose Traveller (MgT) rules for rules that limit the size of ships by TL. Thanks to a discussion over on the Mongoose Traveller Forum, I finally found it. Alas, the limits are not EXPLICITLY laid out and putting it all together is not easy and requires cross-referencing not only several rules but looking across several books too.

The MgT Core Rulebook (CRB) is useful for creation of Adventure-class ships (ACS); i.e. those used by a band of adventurers. ACS are ships from 100-2,999 tons. The CRB has examples of small craft (craft under 100 tons) but no design sequence. The Spacecraft Design chapter allows creation of starships and spacecraft ranging from TL7 to TL15. Within this system, there is no limit to ship size based on TL. However, since all ships need a computer and the Model 1 is not available until TL7 (CRB p. 108) it effectively means that a spacecraft cannot be built before that TL.

MgT Book 2: High Guard (HG) expands on the ship design sequences in the CRB and introduces Capital Ship (over 3,000 tons) and Small Craft design sequences. In typical form for Mongoose Publishing, one must also make sure they have the latest errata to correct the published book. The errata in this case is key because it clarifies the Computer Table on pg. 65 which gives us our ship size construction limits.

The Computer Table on p. 65 includes the columns “Ship Size Minimum” and “Jump Maximum.” The errata clarifies that the designer is to “select the core computer based on the size of the ship or jump requirements, whichever is higher.” Looking strictly at the ship size portion gives us our ship size limits by TL (Read TL; Computer Core Model; MAXIMUM ship size that can be built using this model):

  • TL 9; Core/3; 3,000-5,000 tons
  • TL10; Core/4; 5,001-10,000 tons
  • TL11; Core/5; 10,001-50,000 tons
  • TL12; Core/6; 50,001-100,000 tons
  • TL13; Core/7; 100,001 tons and up

Later computer models add jump capability and computing power but do not affect the size of a ship that can be built. So if one wants to build a 75,000 ton cruiser, one must use AT LEAST a Core/6 computer which is not available until TL12.

Note that ships of 100-2,999 tons can be built at any TL from 7-15; the primary limitation comes from what computer model can be installed. For ships larger than 3,000 tons, the computer Core model limits your size. Restated another way, TL limits the maximum size of ships greater than 3,000 tons that can be built:

  • TL7-8 up to 2,999 tons (use Computer Model 1)
  • TL9 up to 5,000 tons (use computer Core/3)
  • TL10 up to 10,000 tons (use computer Core/4)
  • TL11 up to 50,000 tons use computer Core/5)
  • TL12 up to 100,000 tons (use computer Core/6)
  • TL13-15 any hull over 100,001 tons (use computer Core/7 or greater)

For example, my perennial favorite developing planet, Arden (Arden/0201 Vilis/Spinward Marches) is a TL8 planet on the verge of TL9. What can Arden build indigenously without external assistance? Taking together all the technology limits one gets:

TL 8 Spacecraft Design Limitations

  • Hull Size: Up to 2,999 tons (cost 80%; 1 Hull/90 tons) (HG p. 65, 52, errata)
  • Armor: Titanium Steel (TL7) (HG p. 41)
  • Maneuver Drive max 5G (6G at TL-1) (HG p. 53)
  • No Jump Drive (Jump-1 at TL-1) (HG p. 53)
  • Powerplant – Fusion: 125% tonnage (HG p. 53, 63)
  • Computer – Model 1 (CRB p. 108)
  • Standard Sensors (CRB p. 108)
  • Weapons – Single or Double Turrets (CRB p. 111)
  • Turret Weapons – Pulse Laser, Particle Beam, Missile (HE/Nuclear/Smart/Shockwave/Ortillery), Sandcaster (CRB p. 111, HG p. 48, 50)
  • Weapons – Particle Barbettes (HG p. 50)
  • Weapons – 50-ton Bays (Missile Bank, Particle Beam, Torpedoes [Basic/Nuclear/Ortillery]) (CRB p. 112, HG p. 48)
  • Weapons – 100-ton Bays (Missile, Particle Beam) (HG p. 48)
  • Weapons – Spinal Particle A (HG p. 66) [Note that this spinal mount requires 5,000 tons whereas the TL limited ship size is 2,999 tons; obviously a planetary or station-mount only at TL8]
  • Options limited by TL – Compact Bridge, Aerofins, Docking Clamp, Grappling Arm, Solar Panels, Briefing Room, Standard Hanger, Library (HG p. 47)



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