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Mongoose Traveller SRD

World Creation

World Occurrence: There is a basic one-half chance normally that a world (and its attendant stellar system) will be in a hex. Systematically check each hex on the subsector map, throwing one die and marking the hex with a circle if the result is a 4, 5, or 6. This indicates that a world is present; otherwise, leave the hex blank.

The Referee may elect to alter the normal chances of worlds, making them more frequent or less frequent to correspond to specific regions of the galaxy. A 50% density (no DM) is appropriate for the spiral arms of the galaxy. Apply a –2 DM for ‘rift sectors’, a –1 DM for sparse sectors and a +1 DM for densely populated sectors.

Starport Type: Many worlds have starports, their presence being essential to interstellar trade and commerce.

Bases: Stellar systems may have bases for military forces, the navy, the scouts, or for other arms of interstellar government.

Bases will also help determine political boundaries in the sector. An interstellar government will place bases along its borders to guard against aggression from rival states, or to control local systems. The presence of multiple bases within a few parsecs might indicate a contested border, or a mighty stronghold.

Gas Giants: A star system may have one or more gas giant planets. The presence of a gas giant allows starships equipped with fuel scoops to refuel by skimming; this eliminates fuel cost for the vessel and increases profit. It also allows refuelling at systems that do not have starports. Refuelling in this fashion requires 1–6 hours per 40 tons of fuel.

Gas giants are relatively common. For each system throw 10+ on 2d6 for at least one gas giant not to be present in the system.

Travel Zones: Most worlds are assumed to be civilized, or at least amenable to travellers and visitors. Some, however, are caught in the throes of war, plagued by disease, or simply not ready for interstellar visitors. Such worlds are classified by travel zones to denote such status. In most cases, the Referee should indicate travel zones based on the information available. Two such zone types exist: amber and red.

Polities: Worlds may be independent, or part of a larger polity that spans a system or more. Polities range from loose confederations of a few worlds with common trade or defence policies or cultural links, to vast star empires containing thousand of systems and trillions of citizens. Polity borders should be drawn on the map. Note that larger polities will usually have sub-domains, which should also be marked.

Communications Routes: Within the subsector, local governments will have established communications routes connecting some (but not all) worlds. These routes serve as a conduit for messages between businesses and between governments as well as between people.

Communications routes should be carefully drawn so as to avoid making all parts of the subsector accessible; a subsector should have some areas as backwaters for exploration and adventure. Communications routes are drawn as single lines connecting hexes on the subsector grid.

Trade Routes: Trade routes link worlds that have strong commercial ties. Consult the table below – if any pair of worlds matching the two columns are within four parsecs of each other, and there is a Jump–1 or Jump–2 route between them, then mark a trade route connecting those two worlds.

Column 1Column 2
Industrial or High TechAsteroid, Desert, Ice Capped, Non-Industrial
High Population or RichAgricultural, Garden, Water World

World Creation

The basic planetary characteristics are Size, Atmosphere, Hydrology, Population, Government, Law Level, Technology Level, Starport and Bases, and are generated using two-dice throws, with DMs applied based on other characteristics. These characteristics establish the basic identity of a world, and are referred to as the Universal World Profile (UWP). Additional information can be generated, and should be, to more fully describe a world.

Size (top)

The Size characteristic for inhabitable worlds ranges from 0 to 10, and is determined by rolling 2d6–2.

Size Table
DigitWorld SizeSurface Gravity (gs)
0800 kmNegligible
11,600 km0.05
23,200 km0.15
34,800 km0.25
46,400 km0.35
58,000 km0.45
69,600 km0.7
711,200 km0.9
812,800 km1.0
914,400 km1.25
10 (A)16,000 km1.4

High and Low Gravity Worlds

Worlds where the gravity is 0.75 or less are low-gravity worlds. Common features include improbable-looking rock formations, thin and spindly life forms and flying as a common form of locomotion (assuming the atmosphere is thick enough to support flyers). Humans tend to find life on low-gravity worlds to be initially pleasant, but regular exercise regimes and medicinal supplements are required to prevent bone and muscle degradation. Those who spent too long on low-gravity worlds cannot tolerate higher gravities. Characters on low-gravity worlds suffer a –1 DM to all skill checks until they acclimatise, a process which takes 1d6 weeks. Characters with the Zero-G skill at level 0 or better acclimatise instantly.

High-gravity worlds have a gravity 1.25 times or more than of Earth. They tend to be extremely dense worlds; common features include wide rocky plains, squat, muscular creatures, and plant life that spreads out like lichen instead of growing up. Crawling, burrowing or swimming are the commonest forms of locomotion. Humans find high-gravity worlds unpleasant. Especially high-gravity worlds require the use of pressured or powered suits to support the human frame. Characters on high-gravity worlds suffer a –1 DM to all skill checks until they acclimatise, a process which takes 1d6 weeks.

Atmosphere (top)

A planet’s Atmosphere is generated by rolling 2d6–7 and adding the planet’s Size.

Atmosphere Types

Tainted: Tainted atmospheres contain some element that is harmful to humans, such as an unusually high proportion of carbon dioxide. A character who breathes a tainted atmosphere without a filter will suffer 1d6 damage every few minutes (or hours, depending on the level of taint).

Exotic: An exotic atmosphere is unbreathable by humans, but is not otherwise hazardous. A character needs an air supply to breath in an exotic atmosphere.

Corrosive: Corrosive atmospheres are highly dangerous. A character who breathes in a corrosive atmosphere will suffer 1d6 damage each round.

Insidious: An insidious atmosphere is like a corrosive one, but it is so corrosive that it attacks equipment as well. The chief danger in an insidious atmosphere is that the toxic gases will destroy the seals and filters on the character’s protective gear. An insidious atmosphere worms its way past protection after 2d6 hours on average, although vigilant maintenance or advanced protective gear can prolong survival times.

Atmosphere Table
DigitAtmospherePressureSurvival Gear Required
0None0.00Vacc Suit
1Trace0.001 to 0.09Vacc Suit
2Very Thin, Tainted0.1 to 0.42Respirator, Filter
3Very Thin0.1 to 0.42Respirator
4Thin, Tainted0.43 to 0.7Filter
5Thin0.43 to 0.7 
7Standard, Tainted0.71–1.49Filter
8Dense1.5 to 2.49 
9Dense, Tainted1.5 to 2.49Filter
10 (A)ExoticVariesAir Supply
11 (B)CorrosiveVariesVacc Suit
12 (C)Insidious VariesVacc Suit
13 (D)Dense, High2.5+ 
14 (E)Thin, Low0.5 or less 
15 (F)UnusualVariesVaries

Dense, High (D): These worlds have thick N2/O2 atmospheres, but their mean surface pressure is too high to support unprotected human life (high pressure nitrogen and oxygen are deadly to humans). However, pressure naturally decreases with increasing altitude, so if there are highlands at the right altitude the pressure may drop enough to support human life. Alternatively, there may not be any topography high enough for humans to inhabit, necessitating floating gravitic or dirigible habitats or sealed habitats on the surface.

Thin, Low (E): The opposite of the Dense, High atmosphere, these massive worlds have thin N2/O2 atmospheres that settle in the lowlands and depressions and are only breathable there – the pressure drops off so rapidly with altitude that the highest topographic points of the surface may be close to vacuum.

Unusual (F): An Unusual atmosphere is a catchall term for an atmosphere that behaves in a strange manner. Examples include ellipsoidal atmospheres, which are thin at the poles and dense at the equator; Panthalassic worlds composed of a rocky core surrounded by a water layer hundreds of kilometres thick; worlds wracked by storms so intense that that the local air pressure changes from dense to thin depending on the current wearther; and other planets with unusual and hazardous atmospheric conditions.

Hydrographics (top)

Hydrographic percentage is obtained by rolling 2d6–7 and adding the planet’s Size, modified by the planet’s atmosphere or size as described below:

Size 0 or 1Hydrographics 0
Atmosphere 0, 1, A, B or C–4

If the planet’s atmosphere is not D (or a kind of F that is thick enough to retain water) then also apply DMs for temperature:

Hot Temperature –2
Roasting Temperature–6

Hydrographics Table
DigitHydrographic PercentageDescription
00%–5%Desert world
16%–15%Dry world
216%–25%A few small seas.
326%–35%Small seas and oceans.
436%–45%Wet world
546%–55%Large oceans
766%–75%Earth-like world
876%–85%Water world
986%–95%Only a few small islands and archipelagos.
10 (A)96–100%Almost entirely water.

Population (top)

Population is generated by rolling 2d6–2:

Population Table
DigitPopulation RangeDescription
1Few1+A tiny farmstead or a single family
2Hundreds100+A village
4Tens of thousands10,000+Small town
5Hundreds of thousands100,000+Average city
7Tens of millions10,000,000+Large city
8Hundreds of millions100,000,000+ 
9Billions1,000,000,000+Present day Earth
10 (A)Tens of billions10,000,000,000+ 
11 (B)Hundreds of billions100,000,000,000+Incredibly crowded world
12 (C)Trillions1,000,000,000,000+World-city

If a world has a population of 0, it is uninhabited and so has a Government, Law Level and Technology Level of 0.

Government (top)

The Government characteristic is determined by rolling 2d6–7 and adding the planet’s Population.

Government Table
0 None
1 Company/Corporation
2 Participating Democracy
3 Self-Perpetuating Oligarchy
4 Representative Democracy
5 Feudal Technocracy
6 Captive Government
7 Balkanisation
8 Civil Service Bureaucracy
9 Impersonal Bureaucracy
10 (A) Charismatic Dictator
11 (B) Non-Charistmatic Dictator
12 (C) Charismatic Oligarchy
13 (D) Religious Dictatorship

Rivals, Factions, Connections and Colonies

Roll 1d3 to determine how many factions there are on the planet, with a DM of +1 if the government type is 0 or 7, and a DM of –1 if the government type is 10 or more. Determine what ‘mini-government’ each faction uses on the government table. In cases where the faction type is the same as the current government type, then it is a splinter faction within the ruling government. In cases where it is radically different, then the faction is a rebel group or movement.

Roll 2d6 to determine the strength of each faction:

Faction Strength Tabl
RollRelative Strength
1–3Obscure group – few have heard of them, no popular support
4–5Fringe group – few supporters
6–7Minor group – some supporters
8–9Notable group – significant support, well known
10–11Significant – nearly as powerful as the government
12Overwhelming popular support – more powerful than the government

Law Level (top)

Law level is determined by rolling 2d6–7 and adding the Government characteristic.

Law Level Table - Illegal Possessions
0No restrictions.
1Poison gas, explosives, undetectable weapons, WMDHighly addictive and dangerous narcoticsIntellect programsDangerous technologies such as nanotechnologyVisitors must contact planetary authorities by radio, landing is permitted anywhereDangerous talents must be registered.
2Portable energy weapons (except ship-mounted weapons)Highly addictive narcoticsAgent programsAlien technologyVisitors must report passenger manifest, landing is permitted anywhereAll psionic powers must be registered; use of dangerous powers forbidden.
3Heavy weapons Combat drugsIntrusion programs TL 15 itemsLanding only at starport or other authorised sitesUse of telepathy restricted to government-approved telepaths
4Light assault weapons and submachine guns Addictive narcoticsSecurity programsTL 13 itemsLanding only at starportUse of teleportation and clairvoyance restricted
5Personal concealable weaponsAnagathicsExpert programsTL 11 itemsCitizens must register offworld travel, visitors must register all business Use of all psionic powers restricted to government psionicists
6All firearms except shotguns and stunners; carrying weapons discouragedFast and Slow drugsRecent news from offworld. TL 9 itemsVisits discouraged; excessive contact with citizens forbiddenPossession of psionic drugs banned
7ShotgunsAll narcoticsLibrary programs, unfiltered data about other worlds. Free speech curtailed.TL 7 itemsCitizens may not leave planet; visitors may not leave starport Use of psionics forbidden
8All bladed weapons, stunnersMedicinal drugsInformation technology, any non-critical data from offworld, personal media.TL 5 itemsLanding permitted only to imperial agentsPsionic-related technology banned
9+Any weaponsAll drugsAny data from offworld. No free press. TL 3 itemsNo offworlders permitted All psionics

The Law and Travellers

In each of the following situations, roll 2d6, add the listed modifiers, and if the total is lower than the planet’s Law Level, the characters are investigated or challenged by agents of planetary law enforcement.

First approach to a planet+0Check
Offworlders wandering the streets of a city (once per day)+0Check
Offworlders acting suspiciously –1Check
Bar fight–1Combat
Shots fired–2Combat
Breaking and entering–2Investigate
Firefight involving armoured characters and military weapons–4Combat
Murder and carnage–4Investigate

Check means that the characters’ travel documents and identities are checked, either by a police officer or guard, or by electronically by querying the characters’ comms. A successful Admin or Streetwise roll can allay suspicion but if this check is failed the planetary authorities move on to Investigation.

Investigate means that a detective or bureaucrat probes deeper into the characters’ backgrounds. If the characters have a ship, it will be searched. They may be followed, or have their communications tapped. They may also be questioned closely.

Finally, Combat means that the police show up ready for a fight. Their response will generally be proportional to the threat posed by the player characters; if the characters are just making trouble in a bar, then most police forces will just use batons, stunners, tranq gas and other non-lethal weapons. On the other hand, if the characters are in Battle Dress and firing PGMPs at the palace of the planetary duke, then the police will show up with the best weapons and armour available at the planet’s TL (or even a few levels higher).

Characters arrested for a crime will face punishment, determined by rolling 2d6+DMs on the Sentencing table. For crimes involving smuggling banned goods, the DM is equal to the difference between the planet’s law level and the banned goods in question. Other crimes have a set DM:

AssaultLaw level –5
Destruction of PropertyLaw level –3
False IdentityLaw level –2
ManslaughterLaw level –1
MurderLaw level +0

A character with the Advocate skill may attempt to reduce the severity of sentencing by making a check. If successful, reduce the Sentencing DM by the Effect of the check.

Sentencing RollSentence
0 or lessDismissed or trivial punishment
1–2Fine of 1d6 x 1,000 credits
3–4Fine of 2d6 x 5,000 credits
5–6Exile or a fine of 2d6 x 10,000 credits
7–8Imprisonment for 1d6 months or exile or fine of 2d6 x 20,000 credits
9–10Imprisonment for 1d6 years or exile
11–12Imprisonment for 2d6 years or exile
13–14Life imprisonment

A result of Exile means that the character must leave the planet immediately and never return. Fines for smuggling goods are per ton of goods seized – gun running can be an extremely risky proposition.

Starport (top)

To determine the level of a starport on a planet, roll 2d6:

Starport Table
RollStarport Class
2 or lessX

Technology Level (top)

The Technology Level of the planet is determined by rolling 1d6 and adding DMs as follows:

Starport ValueDM Size ValueDM Atmosphere ValueDM
0  0+2 0+1
1  1+2 1+1
2` 2+1 2+1
3  3+1 3+1
4  4+1 4 
5  5  5 
6  6  6 
7  7  7 
8  8  8 
9  9  9 
10 (A)+6 10 (A)  10 (A)+1
11 (B)+4 11 (B)  11 (B)+1
12 (C)+2 12 (C)  12 (C)+1
13 (D)  13 (D)  13 (D)+1
14 (E)  14 (E)  14 (E)+1
15 (F)  15 (F)  15 (F)+1
X–4 X  X 

Hydro ValueDM Population ValueDM Government ValueDM
0+1 0  0+1
1  1+1 1 
2  2+1 2 
3  3+1 3 
4  4+1 4 
5  5+1 5+1
6  6  6 
7  7  7+2
8  8  8 
9+1 9+1 9 
10 (A)+2 10 (A)+2 10 (A) 
11 (B)  11 (B)+3 11 (B) 
12 (C)  12 (C)+4 12 (C) 
13 (D)  13 (D)  13 (D)–2
14 (E)  14 (E)  14 (E)–2
15 (F)  15 (F)  15 (F) 

Bases (top)

Naval: A naval base is a supply depot, refuelling station, repair yard or fortress of the Navy. Naval vessels can obtain refined fuel and supplies here.

Scout: A scout base offers refined fuel and supplies to scout ships.

Research: A Research base is dedicated to a particular field of research.

Consulate: A consulate is an administration office for various departments such as commerce, justice and foreign affairs. Characters wishing to report significant crimes or obtain various permits will need to visit a consulate.

Pirate: The presence of a pirate base in a system indicates that a group of thieves is active in the area. Pirates are unlikely to be operating out of the starport itself (except on a Law Level 0 world), but no doubt have agents at the port on the look-out for likely prey.

Travel Codes (top)

There are two travel codes – Amber and Red. An Amber world has been deemed dangerous, and travellers are warned to be on their guard. Amber worlds are often undergoing upheaval or revolution, or else are naturally hazardous environments.

Red worlds are interdicted and travel to them is forbidden. A world might be Red because the world is too dangerous to allow visitors. Interdictions are enforced by the Navy.

A world with an Atmosphere of 10+, a government of 0, 7 or 10, or a Law Level of 0 or 9+ should be considered for Amber status. Red codes are given out at the discretion of the Referee.

Variations (top)

The preceding world creation system is geared towards the default Traveller setting of the Third Imperium. Interstellar empires are centrally planned and locally managed, travel between worlds take days rather than minutes or years, and life is everywhere with just enough intelligent alien species to be interesting.

However, there are two other common milieus for science fiction roleplaying: ‘space opera’ and ‘hard science’. Space opera campaigns tend to focus on fewer key worlds and so randomly generated worlds are less likely to be habitable. Hard science campaigns tend to require a rugged individuality and a frontier spirit; slower travel times bleed over to require more generally self-sufficient worlds. In hard science settings, starports are typically built, owned and operated by the host world rather than some central governing power.

Space Opera World Creation

When generating a mainworld for a space opera setting, generate Size and Atmosphere as normal then consult the following if Size is 4 or less:

  • If Size is 0–2, Atmosphere is set to 0. The world is too small to retain an atmosphere.
  • If Size is 3–4 and Atmopshere is 0–2, set Atmosphere to 0.
  • If Size is 3–4 and Atmosphere is 3–5, set Atmosphere to 1.
  • If Size is 3–4 and Atmopshere is 6+, set Atmosphere to A.

Hydrographics is also affected. Apply the following DMs to rolls on the Hydrographics Table:

  • If Size is 3–4 and Atmosphere is A the DM is –6.
  • If Atmosphere is 0–1 the DM is –6.
  • If Atmosphere is 2–3, B or C the DM is –4.

Hard Science World Creation

Hard science worlds use the space opera modifiers above, plus additional Dice Modifi ers to Population based on the Size and Atmosphere as follows:

  • If Size is 0–2 (low gravity world) then the DM is –1.
  • If Size is A (high gravity world) then the DM is –1.
  • If Atmosphere is not 5, 6 or 8 then the DM is –1.
  • If Atmosphere is 5, 6 or 8 then the DM is +1.

In addition, the population of a world has an affect on the class of the local starport. Instead of rolling 2d6 on the Starport Table, roll 2d6–7 and add the Population value.

Trade Codes (top)

Trade Codes Table
AgriculturalAg 4-94-85-7   
BarrenBa   000 
DesertDe 2+0    
Fluid OceansFl 10+1+    
GardenGa 5+4-94-8   
High PopulationHi   9+   
High TechnologyHi      12+
Ice-CappedIc 0-11+    
IndustrialIn 0-2, 4, 7, 9 9+   
Low PopulationLo   1-3   
Low TechnologyLt      5-
Non-AgriculturalNa 0-30-36+   
Non-IndustrialNi   4-6   
PoorPo 2-50-3    
RichRi 6, 8 6-8   
Water WorldWa  10    
VacuumVa 0