Planet Generator

I’ve been thinking further about Stars Without Number’s planet-generating tables. I read through GURPS Space the other day, and it has a complex series of tables for determining the shape of the system (as GURPS does), but it specifically made allowances for the type of inhabited planet the GM planned to put in it. (GURPS space is a great read for anyone running a sci-fi campaign, or planning to, even if you never play GURPS in your life. It’s loaded with amazing tips on constructing a setting).

Anywho, that got me thinking again about the balance of the “character” of the place, and the physical shape of the solar system. About how to balance everything so that each generated system would be unique and fun, and at the same time fast to generate and easy to note down.

Then I gave up, and quickly did up a roll-all-the-dice table. (Note: I cribbed most of the stuff on the d20 column and some from the d12 from SWN, so I can’t claim credit for that. I just picked the good ones.)

Next, I plan to put up a roll-all-the-dice table for generating cities in D&D (as if we needed another (as if the world needed another system for generating a solar system, at that)).

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Solar System Generation revisited

I was thinking about my previous post, and I decided that there’s still too much information: when you get into the outer zone, you’re rolling for planets that are simply too cold to be habitable anyway. And it usually ends up with way more planets than our system, anyway, and that’s another source of too much information. So: a simpler solution.

Each solar system has:
1d6 Gas Giants
1d6 Lifeless Rocks
1d3 Asteroid Belts
1d6-3 Planets

Arrange them as you like: if you’re going for a Sol-like vibe, clump the Lifeless Rocks in the hot zone, and clump the Gas Giants in the cold zone. Give them moons, if you want. For each “planet”, roll 1d6 twice, once for Atmosphere, once for Temperature (see previous post for scale; alternatively, roll on the Stars Without Number tables, or anything similar), and maybe again for gravity. “Planets” can be anywhere (based on their Temperature): near the sun, in the outer rim, orbiting a Gas Giant, in an Asteroid Belt, whatever.

Now a test.

Here’s what I rolled:
5 Gas Giants
4 Lifeless Rocks
2 Asteroid Belts
2 Planets

It’s going to look like this:
3 Lifeless Rocks
Planet, A5/T5, 3 small moons
Asteroid Belt
2 Gas Giants
1 Gas Giant with a moon T1/A3
2 Gas Giants
Asteroid Belt
Lifeless Rock

Solar System Generator

A while ago, I was hoping to start a game of “Stars Without Numbers”. It never happened, unfortunately, but it got me thinking about it’s world generation system. I like it, it’s neat, and it gives you a lot of ideas to play with. My big problem is that it doesn’t generate the entire system. So I went looking for others.

First stop, obviously, was Traveller. That’s pretty much the same, only the world isn’t quite as interesting, and the system that’s generated is basically nothing, just “Gas Giant: Y/N”. After that, I decided to trawl the Interweb for other things.

My problem with all of the ones I found is this: usually they are far too detailed, some especially so. “Alternity Cosmos”, a free PDF that is a custom patch for this problem in the game Alternity (pretty system-neutral, actually), is absolutely insane in the amount of detail. This is cool, but no-one would ever use all of the info, and therefore the tables will rarely get used (plus it takes like an hour plus to generate a full system). Others, while nowhere near as bad, have a similar problem: there is a lot of detail, and for each planet, you have to roll out all of that detail before you know what the planet is like. There’s all sorts of information: temperature, radiation, atmospheric pressure, atmospheric composition, gravity, orbital eccentricity, perihelion… All I want to know is: can the PCs go down there without a suit or not?

So, I have devised a short series of tables to rectify this problem. Here you go:
Planets potentially capable of supporting life have 2 stats: Atmosphere (A) and Temperature (T). Everything else is house-ruled. (1d3* = 1-3: 1, 4-5: 2, 6: 3)

Inner Zone: 1d6 objects, -1A
Habitable Zone: 1d3* objects
Outer Zone: 2d6 objects, -1A

Object: (Inner Zone -2)
1. Asteroid (Belt): 1d6 major asteroids; no A/T
2. Dwarf Planet: 1-in-6 chance of a moon; no A/T
3. Planetoid: 1d3*-1 moons, -1A
4. Planet: 1d3 moons
5. Small Gas Giant: 1d6 moons, -1A (Bespa-style)
6. Large Gas Giant: 1d6+3 moons; no A/T

Moons
Small Gas Giants have a 2-in-6 chance for a planet-sized moon (+1 T)
Large Gas Giants have a 3-in-6 chance for a planet-sized moon (+1 T)
All other moons are dwarf planets or smaller.
Planets with at least 2 moons get +1T

Atmosphere (roll randomly; -1 in Inner/Outer Zones)
1. Crushing/None/Corrosive, need suit (short-term only)
2-3. Dense/Vaporous/Toxic, need suit
4-5.Thin/Thick/Slightly toxic, need breathing mask
6. Earth-like

Temperature (6 in Habitable Zone, -1 per step in/out)
1. Boiling steel/absolute zero, need suit (short-term only)
2-3. Dangerous (Lava, liquid nitrogen), need suit
4-5. Uncomfortable, may require appropriate clothing (desert/arctic)
6. Earth-like

So, basically, if a planet has 6/6, it’s like Earth. If there’s a 4 or 5, people need protection to go down there, but it’s not especially hazardous. If there’s a 2 or 3, people need a suit. If there’s a 1, people need a suit to survive for minutes/days/hours/whatever.

If it’s going to be relevant, here’s another table:

Gravity
1. Low Gravity (if atmosphere is not 6, it’s thin)
2-5. Normal Gravity (if atmosphere is not 6, it’s toxic)
6. High Gravity (if atmosphere is not 6, it’s dense)