My post uses the current Table numbering system.
I would put Table X-2 first with some wording about determining whether the system has multiple stars. For the sake of sanity, I would limit functional star to three with any leftovers automatically being sub-stellar dwarfs. This allows the wide swings of variety you want without bogging down the creation process.
I did that after your first comment. I'll also make it clear that there is no need to detail portions of the solar system that don't affect the adventure.
Keeping in that vein, I would dump planets and belts for the sub-stellar dwarfs for much the same reason.
I would modify Table X-1 to lump all the "sun-like" stars into the same group (K, G and F) to speed up the process. That gives us a range of 3-16 or 70% with a "sun-like" star. Since we live with a "sun-like" star nearby - - we can all relate to what that looks like and know how to describe it.
Will do. There just isn't much difference unless you're talking about either a red dwarf or an A sub-giant.
I would automatically roll for planets on all appropriately sized stars. It just speeds things up. The Ort cloud or something like it is pretty likely to exist within any solar system of note, so I wouldn't include a roll for things like them. Further, I would simplify the asteroid belt rolls to something simple, like 1d4 -1, perhaps less.
Kk. I tried upping the chance of planets but I'd really like this to be a less than 10 minute process. That it took 30 minutes for you is completely unacceptable. I'm also explaining (and looking for ways to simplify) placing planets.
Essentially, table X-9 is as much detail as I think is needed. I'll write some verbiage to go along with it.
Then, we need something to distinguish rocky planets (from Mercury up through super-Earths) from the gas giants.
Only the gas giants should have moons (mini-planets really) capable of supporting a biosphere. While Ganymede - Jupiter's largest moon - is bigger than Mercury, it is still only a fraction of the size of Earth. For the sake of argument, it has about 17% of Earth's surface area, about 7% of the mass (leaving it with only a fraction of the gravity) and only trace amounts of oxygen for an atmosphere. Thus we need really BIG moons to get habitable planets.
Slight disagreement here. Titan would be the counter example. It's in between Mercury and Mars in size with surface gravity lower than the moon's (.14g vs .16g) but it has an atmosphere 1.4 times as dense (and 1.2 times as massive) as Earth's. Titan is an ice ball with a rocky core which complicates matters but it might well retain enough atmosphere to be habitable if it were in a stable orbit of earth. Mars may have also been habitable for the first billion years. If our solar system had been richer in volitiles, or if Earth hadn't formed, it might still be today.
(As I understand it, current theory is that you need enough heat to allow liquid water, enough mass to hold water vapor, and enough water to prevent excess weathering of carbonate rocks, to act as a lubricant to keep plate techtonics going, and it may even be involved in keeping the core rotating so that you have a protective magnetic field. Venus baked because there wasn't enough water to keep the carbon dioxide out of the atmosphere once plate techtonics stopped. Mars loses some of its water vapor to space every time water gets into the atmosphere.)
On top of that, I have a couple of ancient species who spent a lot of time terraforming every surface they could. I'd like to have weirdo systems with two earthlike planets orbiting each other once a week and gas giants that host a dozen habitable moons. But I need the system to be clear. Is this a clarity issue or a credulity issue? Would an explanation help or hurt?
The above lends itself to a re-write of sorts for Table X-6 which should be placed immediately after Table X-2 and a reformed Table X-1. Tables X-3, 4 & 5 are great, as is, but should be moved to the of the system generation section.
Ok. First thing I'm thinking is that X-6 can be simplified. Ice dwarfs and rocky sub-earths are mutually exclusive. They're small planets on either side of the snow line. Likewise, Ice giants aren't really that much different than gas giants (they lack large amounts of hydrogen and helium which makes them smaller) so I can drop the table to subearth, earthlike, superearth, and gas giant.
I'll definitely split the adventure section from the physical section.
I'd simplify Table X-7 just because having a high pressure effect on a low mass planet doesn't make much sense to me. High temperature and toxic environments are fine.
Pressure hazards can be high pressure or low pressure. Do I need to separate them out? (Although Titan is just short of having a high pressure I hazard) Clarity is better than compactness in this case.
I didn't get to Tables X-8 or 9 in my run through, so I don't have any comments on those. Table X-10 looks fine as is.
Hopefully that is of use to you. I'd be happy to run through another building session when you come up with new rules.
X-8 is largely fluff. One of my favorite paintings was a night scene of a young world that orbited a very young blue ringed gas giant. It just struck me how alien that world would be.
X-9 should probably be with the planetary placement section. Although given the ready availability of space suits, how habitable a planet is doesn't matter that much to players except that it gives them alien monsters to fight.
Thanks again for the comments. I'll post up a version 2 in a couple days.