Cosmic SysGen Thoughts

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Cosmic SysGen Thoughts

Postby Crucis on Tue 06 Oct 2009 01:51

I thought that I'm dump some random SysGen thoughts out for people to read and comment upon, if they wish. There may seem to be little rhyme or reason to this thread, except that it's entirely about system generation... :D


A. I have recalculated all of the planetary disk sizes (i.e. max planetary orbit by Star Type), planetary formation zones, biospheres, and tidelock zones from scratch, using all the pertinent formulas. Most of the old numbers from ISF were surprising accurate, though there were a handful of changes.

The max planetary orbit for White Stars should be about 350 LM, and for Red Dwarves, about 150 LM. The Biospheres for White, Yellow, and Orange got a smidge larger and Orange got slid outward by a LM, as it was too close to the star. The Red Star biosphere actually got slid inward by a LM, at it was a little too distant.


B. I've completely redone the number of moons table and die roll modifiers, to account for my interpretation of current planetary/moon understanding, as well as trying to embed the concept of Hill Spheres into the die roll modifier sizes for the Rocky Zone. (The Hill Sphere is the range at which a planet's gravitation influence equals that of its star. I am not actually using maximum moon orbits. Rather what I'm doing is simply using Hill Spheres for rocky planets in certain locations to produce higher negative modifiers and fewer moons.)


C. Speaking of Moons, all moons will be defined as "major" moons, as in those having a radius of 500 km or more. There are 15 such "major" moons in our Solar System (ranging from about 533 km to about 2600 km in radius), and this seems like a respectable number, as opposed to the many, many dozens upon dozens of smaller "satellites". I mention this point because it becomes extremely critical as it related to mutually tidelocking planets and moons, a topic on which I created a separate thread earlier...


D. All moons are always tidelocked to their planet. If you investigate the 15 major moons in the Solar System, you'll find that all 15 of them are tidelocked to their planet. All of them. The only moons that rotate are those that are too small and too distant from their planet to become tidelocked. However, major moons are simply too large and too close to NOT be tidelocked to the planet.
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Re: Cosmic SysGen Thoughts

Postby szurkey on Tue 06 Oct 2009 20:01

Crucis wrote:C. Speaking of Moons, all moons will be defined as "major" moons, as in those having a radius of 500 km or more. There are 15 such "major" moons in our Solar System (ranging from about 533 km to about 2600 km in radius), and this seems like a respectable number, as opposed to the many, many dozens upon dozens of smaller "satellites". I mention this point because it becomes extremely critical as it related to mutually tidelocking planets and moons, a topic on which I created a separate thread earlier...


While I don't dispute your position of planets not being tide locked to moons, your definition of "major" moon is apparently rather questionable. I stumbled across an write based on a journal article that says that Saturn could easily have a moon the mass of Earth. Now that would be a MAJOR moon. I haven't had a chance to work through the article to confirm this (and probably won't get to it for a month or two), but here's the link to the article:

http://www.iop.org/EJ/abstract/0004-637X/575/2/1087
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Re: Cosmic SysGen Thoughts

Postby Crucis on Tue 06 Oct 2009 20:17

Actually, SZ, I didn't place an upper limit on the definition of "major" moon. Only a lower limit (of 500+ km radius). The mention of 2600 km radius was only meant to indicate the largest moon in OUR solar system ... Ganymede.

Could there be moons larger than Ganymede? I suppose so...

In counter-point to your link, I thought that I read a different linked article a couple of weeks ago that postulated that moons larger than the largest ones in our Solar System were very unlikely, though I don't remember why or have the link at hand. (I'll try to find it, but I don't remember what I was searching for at the time, so re-finding it might be a bit tricky...)
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Re: Cosmic SysGen Thoughts

Postby Crucis on Tue 06 Oct 2009 20:19

BTW, do you know what the M(+) (M for mass, followed by a little circle with a plus sign within) stands for?

EDIT: I'm thinking that it indicates "M(star)", though I've not see this particular subscript before that I can recall...
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Re: Cosmic SysGen Thoughts

Postby Crucis on Tue 06 Oct 2009 20:50

On the topic of differing moon sizes...

Yes, I could do a model for differing moon sizes. It wouldn't be all that difficult at all to produce. That's not the issue for me. The issue really is that it increases the complexity of the game because differing moon sizes really only matter if they have differing population capacities. And once moons of different sizes have different population capacities, it's only logical that the same thing will have to be applied to planets of different sizes.

So, instead of having a model with two basic system body sizes, planet and moon (well, I suppose that asteroid belt might be a third, but we'll set that aside for now), you might end up with a model having around FIVE different basic body sizes: 1) small moon, 2) average moon, 3) large moon/small (mass 1) planet, 4) average (mass 2) planet, and 5) large (mass 3) planet.

While such a model might be acceptable to some people who seem to revel in every conceivable detail they can produce, I think that most people would prefer a simpler model and accept that some measure of abstraction are necessary to maintain a bearable level of complexity. In the two basic system body size model, the player is pretty much asked to assume that planets and moons have abstract average sizes. And frankly, even if you did use a five size model, even within that model, the population capacities would be abstracted averages... you will have just created a model with a somewhat greater degree of granularity at the expense of a greater degree of complexity. And I'm not convinced that the benefit in this case is worth the cost.
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Re: Cosmic SysGen Thoughts

Postby Crucis on Wed 07 Oct 2009 00:06

This is an example of what a 5 size level model might look like.

Note that the Large moon/Mass 1 planet are the same size. This is because the largest moons in our solar system area actually a bit larger than Mercury, which I roughly define as the lower limit of Mass 1 for planets.

Also note that the pop numbers for the Tiny Moon are so small because the surface areas of such moons are simply much, much smaller than even an average moon. (You might be able to argue for a couple more PU's, but not much more...)


SizeDescriptionDesolate Pop LevelExtreme Pop Level
5Mass 3 PlanetSmallna
4Mass 2 PlanetSmallna
3Large Moon/Mass 1 PlanetSettlementColony
2Average MoonColonyOutpost
1Tiny Moon2 PU1 PU



However, I should note that if one uses such a model, it would become necessary to define just how large or small a tiny moons actually is, because the result might be that you'd have to account for a lot more moons, particularly around Type G and I planets... Perhaps up to 8 or 10 (or more)... As long as the only moons that we worry about are "major" moons (those having radii of 500 or more km), the number of moons being tracked can be kept to a reasonable number (5 or less, per planet).

Of course, I suppose that one might say, "fine, then just dump the tiny moons, but keep the large moons". And I suppose that that would be doable. But then there's bound to be someone who wonder why we don't have smaller than average moons.


Another point that might be raised was referred to in that link in szurkey's post about there potentially being no size limit on moons, particularly of gas giants. That would seem to imply that they could have a Mass 2 or 3 "planet" as a "moon". But how common would that really be? And is it really, really worth the hassle? For that matter, a mass 2 or 3 Type B "moon" of a Gas Giant might be mildly interesting, but are a few extra PU (well, a settlement vs. a Colony) on a gas giant moon once in a blue moon (pardon the pun) really worth the hassle? Oh, I suppose if the Gas Giant were a Hot Jupiter orbiting in the star's biosphere, that mass 2 or 3 moon might end up being an Endor-like Type T "moon". But is that really functionally any different than if it were just a Type T planet, aside from the flavor?

I guess what it comes down to is that some people can accept a greater level of abstraction in the name of game simplicity than other people. Some people just have to have every possible bit of accuracy and to hell with what it does to complexity, while others are more forgiving or accepting of the abstractions.

Oh, well. Feel free to weigh in with your opinions...
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Re: Cosmic SysGen Thoughts

Postby Crucis on Wed 07 Oct 2009 17:13

Just for (more) yucks, here is an example of what a slimmed down 3 size level model might look like. I have merged Mass 2 and 3 planets into a single size category and have just plain dumped the "tiny moons" from the previous model.

And just as food for thought, it was suggested to me that Ultra might be viewed as having 2 size categories of moons if you look at Type mT moons as being of a different size than normal moons. I'm not sure that I agree with that perception, but one could look at it that way. Regardless, if one decides to recognize that there are 2 moons (Jupiter's Ganymede and Saturn's Titan) in our own Solar System that are actually larger than the smallest Mass 1 planet (Mercury), as well as one other moon (Jupiter's Callisto) that's only very slightly smaller than Mercury (Callisto's radius is only 30 km smaller than Mercury, at 2410 km vs. 2440 km), then one logically ends up going down a path of greater differentiation that also needs to account for differing population capacities.

Put another way, if one wants to account for larger moons, it follows that you are going to want to allow for more people (PU) to be put on them, otherwise, what's the real point in saying that (for example) Ganymede is much larger than Tethys? Unless there's a reason to account for the size difference, why does it matter? But if you differentiate between large and average sized moons (even with tiny moons ignored), you cannot help but make the same differentiation between Mass 2/3 planets and the much smaller mass 1 planets, since the comparative degrees of surface area between M2/3 and M1 planets is similar in proportion to large moons vs. average moons.

That said, at luck (or reality) would have it, those large moons and mass 1 planets just happen to share the same general sizes... so if one was inclined to desire a somewhat more accurate model, the table below might be suitable to the task without too great an increase in complexity. Note that I'm not actually so inclined to use this model, though it is a bit tempting.

On the possible question of merging Mass 2 and 3 planets into a single size, a large part of the reason is for game balance reasons. If you start recognizing serious size differentiation between Mass 2 and 3 planets, then the logic will follow that T and ST planets would arguably have different population limits, and who knows what issues that would raise, what problems that would create. It's easier to simply assume that all M2 and M3 planets have roughly similar sizes and population capacities and avoid the complexities. (Of course, I suppose that it's also worth noting that it appears that the same people who desire this sort of differentiation in moon sizes and so forth aren't exactly worried about making an already overly complex game even more complex... ;) )



SizeDescriptionDesolate Pop LevelExtreme Pop Level
3Mass 2 or 3 PlanetSmallna
2Large Moon or Mass 1 PlanetSettlementColony
1Average MoonColonyOutpost


It's also worth considering that when you keep Mass 2 and 3 planets at same size for population purposes, this entire issue appears to boil down to how one looks at large moons, average moons, and small (mass 1) planets. And mostly for Type B bodies, though I suppose that Types H (Hot) and F (Frozen) bodies could enter the mix as well. But it seems to affect Type B bodies most greatly because they already have the potential to range in size from (average) moon all the way up to Mass 2/3 planets. Even if you had a large Type H "moon", it'd still have essentially the same population capacity as a Type H planet. And if you had a large Type F "moon", it's have the same population as a (currently non-existent, but entirely do-able) Type F planet.


I suppose that there's an even simpler model ... "large moons" (particularly of Type G and I planets) might be treated as "planets" rather than moons of their normal type (Type mB for Gas giants, or Type mF for Ice giants), with the inherent increase in population capacity. However, I think that this model really still logically begs the question of if "large" moons have a greater population capacity than smaller, average moons, then why isn't the same true of, say, mass 1 vs. mass 2/3 planets? And then you're right back at a 3 or 5 size level model... as discussed above.

I guess that I tend to think that the more abstract model is the better option for a less complex game, but if there was any sort of strong desire for a slight increase in granularity in this regard, I suppose that I could see going with the 3 size level model.... It really doesn't add all that much complexity. The trick though would be in determining just how common larger moons really were. The 1% occurrence rate in Ultra is just too low, when faced with the reality that 20% of the major moons in the Solar System might qualify as "large" moons. BTW, I'm not saying that true "twin" planets of Type T/ST's should be more common, only that moons, particularly of Type G and I planets, would likely have a rather greater chance of being considered "large"...

Regardless, that's all for now. Please feel free to weigh in...
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Re: Cosmic SysGen Thoughts

Postby Dawn Falcon on Thu 08 Oct 2009 18:11

I'd tend to ignore the "chaff moons" for colonisation.

However, I'm also in favour of being able to roll for useable asteroids for AFs within a system, one of the smaller positive modifiers being "number of planets", simulating "chaff moons".
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Re: Cosmic SysGen Thoughts

Postby Crucis on Thu 08 Oct 2009 18:48

Dawn Falcon wrote:I'd tend to ignore the "chaff moons" for colonisation.

However, I'm also in favour of being able to roll for useable asteroids for AFs within a system, one of the smaller positive modifiers being "number of planets", simulating "chaff moons".


Great turn of a phrase! "chaff moon". That pretty much covers those small moons that might only be large enough for a tiny handful of PU.





As for numbers of usable asteroids for AF's, while it's certainly easy enough to simply include a die roll, it seems that the size of a "rock" need to be a decent AF isn't all that large and is probably rather common, though I will do a little bit of research to see it this is actually true.... (checking out the wiki page...) Hmmm.... according to wikipedia ( http://en.wikipedia.org/wiki/Asteroid_belt#Characteristics ), there are between 700,000 and 1.7 million asteroids with a diameter or 1 km or greater. Frankly, with THAT many rocks of that size, it's hard to see how there could be any practical limit in the number of AF-capable asteroids in any rocky AB.


One thing that does occur to me is that asteroid belts in the Ice Zone (think the Kuiper Belt in our own Solar System) may need to be reconsidered, since they are not rocky bodies, but bodies "composed mostly of ices such as water, ammonia and methane". Such belts with this sort of composition don't really seem like particularly fertile ground for mining (at least for T races). Also, if these bodies are "composed mostly of ices such as water, ammonia and methane" towing one sunward to your shipyards orbiting a Type T/ST homeworld might simply cause it to melt away.

It may be that Ice Zone asteroid belts (which in Starfire, would usually be the result of binary star interaction) simply are "chaff", to use your term, Andrew, and perhaps should be ignored.

On the flipside, in any game that included the Unusual "Ice" race, I could see an Ice race finding aF "frozen" AB's as being highly useful places, though they would still have the potential issue of "melting AF's" if they wanted to drag an "aF" belt's Asteroid Fortress sunward.
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Re: Cosmic SysGen Thoughts

Postby krenshala on Thu 08 Oct 2009 19:28

back when I was looking at the Sol system from a (GSF) Starfire perspective, I noticed that all the non-chaff moons had a mass no smaller than about 10^19 (or was it 10^17?) kg. for reference, the rocky planets (with, iirc, the exception of mercury and pluto) were 10^20 or 10^21 kg, with the gas giants a few steps higher (10^24+).

also, i *love* the table a few posts above with the 5 moon/planet sizes! that appears to be the type of thing i was trying to come up with when i first started working on my interpretation of what the sys-gen system should be. you've inspired me to make a change. thank you! :D
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