System Generation

[jayouzts]

I am not sure if this is a "bug" or a "feature", but I thought I would raise it.

When you Generate a star system, the largest planet you can generate is size A, which is about 16000 km, which is 25% bigger than earth.

IIRC Saturn is about three times bigger than earth. Jupiter is 11 times bigger.

Now I realize that the gravity and/or pressure of these worlds would crush any spaceship that entered the atmosphere, so it could be that these systems were omitted for playability reasons. Still, such huge planets add flavor to a system.

So was limiting planet sizes to size A intentional?

 

[Tom Schoene]

Extended World generation will create gas giants like this to be placed somewhere in the solar system. The basic world generation system just gives you the potentially habitable mainworlds.

In a few cases, the main world can actually be a moon in orbit around a gas giant, but a gas giant is never going to be the mainworld itself.

 

[jayouzts]

Thanks. Wheere do I find the Extended World generation?

 

[tjoneslo]

Follow the order of the star system generation, (no page refence because no book), but Step 5: Gas Giants Present show how many gas giants are in the system, and the text shows how to determine their size.

 

[archhealer]

For the record, I expanded the world size chart (not the rolls, these should only be placed by the ref, I imagine) to go up to about 60,000 (Plus a bit, I don't have the chart handy) km diameter. These worlds are huge, and have massively crushing gravity. They're an anomoly. But I like i tthat way! I'll post the info here at some point, when I'm able.

 

[tjoneslo]

I'd love to see a copy of your expanded world chart.

The downside of the chart is there is a tipping point, where if the planet exceeds a certian size, it becomes a gas giant. This tipping point is when the planet can hold hydrogen in the atmosphere against the star's heat and solar wind. What size this is depends upon the size and activity of the star, how far the planet formed from the star, did it have a magnetic field, and how quickly did the hydrogen accumulate, and probably a few other things as well.

If a planet has crossed this threashold, the hydrogen acculates, creating a gas giant. So for a simple planetary generation system you will have this odd gap between the largest terrestrial planets and smallest gas giants. If the rocky planets get any larger, they become gas giants.

 

[archhealer]

True, most of the time. I did it primarily to allow for really odd situations. The gravity also doesn't progress the way it likely would, as density of solid mass would gradually increase, right along with the size and gravity, therefor meaning that the gravity would be an exponential increase, if I'm not mistaken, but I kept it simple. I'll post it here as soon as I remember to bring the sheet to work with me (I don't have net at home).

I was only going to bring the planets up to size C, but then said what thh heck, I had all the math laid out in front of me, so took it all the way to Z. I hesitated, but still used R and S, even though these are special satellite size categories, because I'm pretty sure there is no possible way for a planet to have a sattelite that big... though, if you're going to allow size X or Z planets ANYHOW, why the heck not, I guess...

 

[tjoneslo]

Another interesting factor to throw into the planet size discussion. Gas Giants can't get much bigger (in terms of diameter) than Jupiter. As you add more hydrogen to the atmosphere, you'd expect it to get larger in diameter. But the increased gravity causes the core to collapse even further. The planet gets more massive, but not any larger. Until the point where the gravity pressure ignites the hydrogen fusion.