Mneme World Generator
Mneme World Generator
The Mneme World Generator is a set of variant rules for the Cepheus Engine tabletop RPG system, designed to generate detailed solar systems, worlds, inhabitants, and societies for science fiction settings. It is derived from the Traveller System Reference Document and other Open Gaming Content.
Authors: Justin Cesar Aquino, Niccolo Salonga
Proofreading: Niccolo Salonga
Art: Niccolo Salonga
World Generation Spreadsheet: John Karol Abayan, Lloyd Reyes, Ranz Sapinit, Michael Ibanez, Christine Melody Taa
Supporting Material
- World Generator Spreadsheet (Automatic Solar System Generation)
- How to use the World Generator Spreadsheet
- OGL Document (Google Drive)
Legal Notice
Cepheus Engine and Samardan Press are trademarks of Jason "Flynn" Kemp.
This product is derived from the Traveller System Reference Document and other Open Gaming Content made available by the Open Gaming License. These are Variant Rules, specifically called the Mneme Variant Rules. Please credit the Mneme Variant Rules when deriving content from this work.
Core Rulebook
| # | Chapter | Description |
|---|---|---|
| 0 | Front Matter & Credits | Credits, acknowledgements, legal notices, and supporting links |
| 1 | Chapter 1: Definitions | Earth-centric and Mneme definitions, stellar classifications, world types, size classes, atmospheres, and all key terms |
| 2 | Chapter 2: Minor Mechanics | Advantage/Disadvantage rules and other minor mechanical variants |
| 3 | Chapter 3: Mneme World Generator Overview | Introduction to the world generation system |
| 4 | Chapter 4: Determine Star | Stellar class, mass, luminosity, companion stars, zones, limits, and tech level tables |
| 5 | Chapter 5: Determine Main World | World type, habitat worlds, dwarf planets, terrestrial worlds, gravity determination |
| 6 | Chapter 6: Determine Habitability | Atmospheric pressure, temperature, hazards, biochemical resources, habitability modifiers |
| 7 | Chapter 7: Determine Position (Main World) | Terrestrial world qualities, main world position tables |
| 8 | Chapter 8: Determine Inhabitants | Population, wealth, power structures, development, governance, sources of power, travel zones, starports |
| 9 | Chapter 9: Determine Planetary System | Full planetary system generation, planetary positions, disk zones, asteroid types, gas world types |
| 10 | Appendix | Administrative rolls, legal rolls, influencing attitudes, credit values, radiation exposure, vacc suits, hazmat suits, technology level definitions (TL0–TL16), culture table, hex map instructions |
| 11 | Open Game License (OGL) | Full Open Game License text and Section 15 copyright notices |
Supplemental Documents
| Document | Date | Description |
|---|---|---|
| Ships & Star Systems – Master Equation Sheet | Oct 2025 | Master reference sheet covering ship and star system equations and calculations |
| World Generator PWA v04 | Oct 2025 | Progressive Web App design document for the Mneme World Generator, version 04 |
| World Generator PWA (Dec 2025) | Dec 2025 | Updated PWA specification and notes, December 2025 |
| PWA Challenges & Notes | Jan 2026 | Known challenges and design notes for the World Generator PWA |
| Logic Specification (Feb 02 2026) | Feb 2026 | Detailed logic specification for Mneme World Generator implementation |
| Logic Specification (Feb 22 2026) | Feb 2026 | Latest revision of the Mneme logic specification |
Future Changes (260222)
- Source
- Mneme_World_Generator_260222
- Status
- Active — to be incorporated into the next version
- Version
- Draft 2.1
- Philosophy
- Simulationist, Recursive, Modular
Proposed New Chapter Structure
The next version reorganises the rulebook into these top-level chapters:
- Introduction — Credits, Key Definitions, Core Philosophy, Required Tools
- Level 1: Stellar Generation — System Budget, Primary Star, Multiple Stars, Barycenters, Rule of Five
- Level 2: Inras (IntraStellar) Systems — Generation Pool, Gravitational Waterfall, Mutual Hill Radius, Orbital Zones
- The Prime Inras (Main World) — Main World Type, Habitability Waterfall Algorithm
- Civilisation & World Development — HDI, Gini Coefficient, SOC, Effective Standard of Living
- Technology & Hard Sci-Fi Mechanics — Mneme Tech Level System, Tech Distribution, Delta-V Map
- Economics & Infrastructure — Credit Recalibration, Starport Generation, Port Value Score
- Environments & Equipment — Environmental Systems, Artificial Habitats, Procedural Vacc Suits
- Appendices — Traveller/CE Integration, PWA, D66×D6 Tables, Glossary, OGL
New Four-Level Orbital Hierarchy
| Level | Name | Components |
|---|---|---|
| 1 | Stellar & Barycenters | Stars, Companion Stars, Barycenters (centres of mass) |
| 2 | Inras (IntraStellar) Systems | Gas Giants, Terrestrials, Dwarf Planets, Asteroid Belts, Circumstellar Disks |
| 3 | Sub-Systems | Moons, Ring Systems, Co-orbitals (Trojans/Greeks), Lagrange Point Clusters |
| 4 | Details & Surface | Continents, Biomes, Craters, O'Neill Cylinders, Surface Centrifuges ("Magicians") |
- "A moon orbiting a planet uses the same physics engine class as a planet orbiting a star."
New Orbital Zone Formulae (Replaces Zone Table)
Snow Line:
D_snow = 2.7 × √L_Star
Habitable Zone:
HZ_center = √L_Star HZ_inner = 0.95 × HZ_center HZ_outer = 1.37 × HZ_center
| Zone | Range | Description |
|---|---|---|
| Infernal Zone | 0.0 – 0.1 AU | Hot Jupiter territory |
| Inner Zone | 0.1 AU – HZ_inner | Too hot for liquid water |
| Habitable Zone | HZ_inner – HZ_outer | Goldilocks zone |
| Outer Zone | HZ_outer – D_snow | Asteroid Belt usually forms here |
| Frozen Zone | D_snow – 100 AU | Gas/Ice Giant territory |
| Scatter Disk | > 100 AU | Kuiper Belt, Oort Cloud |
Mutual Hill Radius — New Core Formula
Defines the gravitational reach of two planets and determines minimum safe orbital spacing:
R_H = ((a₁ + a₂) / 2) × ∛((m₁ + m₂) / (3 × M_Star))
| Variable | Definition |
|---|---|
| a | Semi-Major Axis in AU |
| m | Planet Mass in Earth Masses |
| M_Star | Star Mass (massive stars compress Hill Radii) |
Mneme Stability Standard (K Values):
| K Value | Meaning |
|---|---|
| K < 3.5 | Chaos Limit — Unstable |
| K < 5 | Mneme Forbidden Zone (Rule of Five) |
| K ≈ 8 | Relaxed System (Sol-like baseline) |
Gravitational Queue Placement (Replaces Position Table)
- Sort all objects by Mass (highest to lowest)
- Place heaviest object first (Gas Giant at Snow Line)
- Calculate its Forbidden Zone using the Mutual Hill Radius
- Each next object must sit at
Δa > 5 × R_Hfrom existing objects - If conflict: The Shove — push outer planet to safe distance:
a_outer_new = a_new + (5 × R_H) + Variance - Ripple Effect — repeat down the chain until no conflicts remain
- Far Outer Exception: Objects in the Scatter Disk (>100 AU) are never moved; the intruder is ejected instead
Habitability Waterfall Algorithm (Replaces Habitability Table)
| Step | Factor | Logic |
|---|---|---|
| 1 | Mass & Gravity | Low mass → Disadvantage on Atmosphere. High mass → Advantage |
| 2 | Orbital Position | Inner Zone → Adv on Temperature, Disadv on Biochem. Outer Zone → reverse |
| 3 | Composition | No volatiles → caps Atmosphere. Abundant volatiles → Dense atmosphere modifiers |
| 4 | Hazards | High hazards can immediately disqualify world from "Garden" class |
| 5 | Atmosphere | Derived from Mass + Volatiles. Acts as Greenhouse Effect multiplier on Temperature |
| 6 | Temperature | Final state from Position (Step 2) × Atmosphere (Step 5) → Habitability Rating |
Updated Civilisation Mechanics
New rolls and formulae:
- HDI Roll — 2D6 → determines Human Development Index (Underdeveloped to Very Developed) and World Average SOC
- Gini Coefficient Roll — determines Inequality Rating (Low to Extreme)
- Elite Ratio:
Elite Ratio = (1 / (Gini Score + 1)) × 10% - Effective SOC:
Effective SOC = Individual SOC + (World Average SOC - 7)
Tech Divide Access Logic:
| SOC Level | Access |
|---|---|
| High SOC (Elites) | Full access to Setting TL |
| Mid SOC (Citizens) | Access to Standard TL |
| Low SOC (Subsistence) | Restricted to Scavenged / Archaic Tech |
Updated Starport Generation
PVS (Port Value Score) replaces the table roll:
PVS = (Habitability / 4) + (TL - 7) + Wealth Modifiers
Social Standing — Doubling Power Scale
SOC retooled to a Base-2 logarithmic scale — every +1 SOC = 2× increase in Income, Wealth, and Resource Access.
| SOC | Meaning |
|---|---|
| 10–11 | "Billionaire" / Head of State |
| 14+ | Stellar Elite (owns Habitats / Megacorps) |
Companion Star Cap Multiplier (New)
Ensures companion is never more massive/luminous than the primary:
- Convert Primary's Class/Grade to a 0–100 linear value
Cap Multiplier = Primary Value / Max Possible Value- Roll for Companion normally, multiply result by Cap Multiplier
Planned Supplemental Materials
- Procedural Vacc Suit Blender File — Justin and Nicco to create procedural geometry nodes file for randomised Vacc Suit designs by Tech Level
- PWA goals — Offline-capable, IndexedDB storage, CSV/JSON export, nested sortable stellar data UI (see Mneme World Generator/PWA (Dec 2025) and Mneme World Generator/PWA Challenges)