Planetary Size

Planetary Size: Worlds are classified according to their physical size.

• Only Mainworlds (worlds or planets) of interest are recorded.
• e.g. Gas Giants are simply classified as Small (SGG) or Large (LGG).

Description (Specifications)

Planetary density and size are two primary factors when determining a planet's gravity.

Planetary Size Data

The following table outlines the UWP codes for the size of a body:

Planetary Size

Code	Description	Diameter (Km)	Horizon (meters)	Expected Gravity	Remarks
R	Planetary Ring	Multiple < 1	—	Microgravity (0.01 G or less)	Planetary Ring, Planetoid
D	Debris	1+ < 200	tens (maximum)	Microgravity (0.01 G or less)	Debris Field, Planetoid
0	Asteroid / Planetary Belt	Multiple < 200	tens (maximum)	Microgravity (0.01 G or less)	Planetoid Belt, Planetoid
S	Very Small	200-799	hundreds	Very Low Gravity (400 km, 0.02g - 0.03g)	Very Small World
1	Small	800-2399	2000	Very Low Gravity (1,600 km, 0.05g - 0.09g)	Small World
2	Small (e.g. Luna)	2,400-3,999	2500	Low Gravity (3,200 km, 0.10g - 0.17g)	Small World
3	Small (e.g. Mercury)	4,000-5,599	3000	Low Gravity (4,800 km, 0.24g - 0.34g)	Small World
4	Medium (e.g. Mars)	5,600-7,199	3600	Low Gravity (6,400 km, 0.32g - 0.46g)	Meso World
5	Medium	7,200-8,799	4000	Standard Gravity (8,000 km, 0.40g - 0.57g)	Meso World
6	Medium	8,800-10,399	4400	Standard Gravity (9,600 km, 0.60g - 0.81g)	Meso World
7	Large	10,400-11,999	4800	Standard Gravity (11,200 km, 0.70g - 0.94g)	Macro World
8	Large (e.g. Venus / Terra)	12,000-13,599	5100	Standard Gravity (12,800 km, 0.80g - 1.08g)	Macro World
9	Large	13,600-15,199	5400	Standard Gravity (14,400 km, 1.03g - 1.33g)	Macro World
A (10)	Huge	15,200-16,799	5700	Standard Gravity (16,000 km, 1.14g - 1.48g)	Big World
B (11)	Huge	16,800 - 18,399	6000	High Gravity (17,600 km, 1.49g - 1.89g)	Big World
C (12)	Huge	18,400+	6300	High Gravity (19,400 km, 1.9g - 2.0g)	Big World
SGG	Small Gas Giant (no further codes)	40,000-120,000	—	Macrogravity (2.01 G or higher)	Gas Giant
LGG	Large Gas Giant (no further codes)	120,000-240,000+	—	Macrogravity (2.01 G or higher)	Gas Giant

• NOTE-1: The size code D ( Debris ) is non-standard. It is included to cover such cases as Comet Mid-Rift (Deneb 3234), which are less than 200Km, but not part of an asteroid belt, yet important enough to have mention.
• NOTE-2: The gravity values are estimations based on a standard planetary density. Planets with less or more dense cores may have very different values from the suggested average.

History & Background (Dossier)

When the UWP was created, any number of planetological figures were considered for inclusion. Initial discussion led to 16 and 32-factor descriptive chains, but these were too many, especially for a Universal Code. Eventually the UWP was pared down to just eight factors. Of those eight factors, one of the most disputed was Planetary Size.

Size included many, many factors including:

• Gravity
• Physical measurement parameters
• Planetary density
• Tectonics
• Vulcanism
• etc.

See also

Universal world profile

§ == ( Please refer to the following AAB Library Data for more information: ) == §

• Main world
• Hex Number
• Universal World Profile
  • Starport (Sp)
  • Planetary Size (S)
  • Atmosphere (A)
  • Hydrosphere (H)
  • Population (P)
  • Government (G)
  • Law Level (L)
  • Tech Level (TL)
• Trade classification & Sophont Codes
• Importance Extension (Ix)
• Economic Extension (Ex)
• Cultural Extension (Cx)
• Nobility
• Bases
• Travel Zone
• PBG - Population, Belts, Giants
  • P: Population Multiplier
  • B: Belts
  • G: Gas Giants
• Worlds
• Allegiance Code
• Stellar Data
• COG Sequence
  • C: Climate
  • O: Orbit
  • G: Gravity

References & Contributors (Sources)

This list of sources was used by the Traveller Wiki Editorial Team and individual contributors to compose this article. Copyrighted material is used under license from Far Future Enterprises or by permission of the author. The page history lists all of the contributions.

• Marc Miller. Worlds and Adventures (Game Designers Workshop, 1977), 10.
• Marc Miller. Scouts (Game Designers Workshop, 1983), 47.
• Marc Miller. Referee's Manual (Game Designers Workshop, 1987), 22.
• Geir Lanesskog. World Builder's Handbook (Mongoose Publishing, 2023), 52-53,60-63.Joe Fugate, J. Andrew Keith, Gary L. Thomas. World Builder's Handbook (Digest Group Publications, 1989), 52-53,60-63.
• Terrance McInnes, Dave Nilsen. World Tamer's Handbook (Game Designers Workshop, 1994), 87.
• Jon F. Zeigler. First In (Steve Jackson Games, 1999), 57-58.
• Paul Elliott. The Universal World Profile (Zozer Games, 2016), .
• Marc Miller. T5 Core Rules (Far Future Enterprises, 2013), 409,413.
• Matthew Sprange. Core Rule Book (Mongoose Publishing, 2016), 216-217.
• Contributor: Lord (Marquis) and Master of Sophontology Maksim-Smelchak of the Ministry of Science