There are a lot of systems for generating other solar systems and worlds out there, both as game rules and as web sites. However, I wasn't that happy with them. Many are good for space-opera settings, but not for hard SF. Other were limited in scope (only "garden" worlds) or out-dated. So I decided to put this together myself, more as a collection of ideas than anything else.


I do not claim for this document to be scientifically correct. Many generation formulae include a random component, for instance, and others are constructed just to make "decent" results as I see it. The ideas are a collection of various sources from literature to news articles, and as always they may not be correct or interpreted correctly. Also, there may be problems with the equations I haven't noted. Several of the formulae are however just ordinary physics, calculating the scale height or surface gravity is a straightforward thing.

There is a foundation in science, though. It may be simplified or skewed, or based upon inaccurate background data, but the intention has been "realism". If you don't like any of the charts or equations, change them by all means. And if you find any errors or strange things, do contact me.


Part I is in many ways designed as a "manual". There are steps in the beginning of each section, which can be followed to generate a system. Often some of the generation isn't necessary, if you already have background data or an idea you can use it just to flesh things out a bit. References to "1d10" and "1d100" and so on are relating to a random number from 1 to the number after the "d", as symbolized by rolling a die. Most calculators and computer math programs are capable of generating random numbers. If you intend to generate several systems I suggest you make a simple spreadsheet program to speed up things. The steps are often involving a lot of math. Unbelievably as it may seem, things could be made even more complex than they are, but it you prefer a simpler version there are a lot of steps that can be ignored or simplified.

Part II is more of a descriptive section, and as such is mainly for inspiration about how planets work and what should be considered. There are also some templates which can be useful for planetary and system mapping.


I have included a reference list at the end of the document, which contains many of the works that has served as inspiration for this document. Any misinterpretations of such works are entirely my own fault. Also, I'd like to thank Peter Trevor in particular and Even Sorgjerd for their many valuable suggestions, corrections and questions, and Andy Goddard for his assistance with the Coordinate Systems section (5.2).

Written by Tyge Sjöstrand

This document may not be distributed, modified or copied without the permission of the author. This document is for non-commercial use only.

Terrain scenes made in Terragen, copyright M.P. Fairclough, Planetside Software

If you have any corrections, questions and/or suggestions, or if you find the document useful, mail me: [email protected]

This incomplete version of the document is dated 2000-08-06