Sysgen Topics*: Stellar Disks (day 3)

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Sysgen Topics*: Stellar Disks (day 3)

Postby Cralis on Wed 12 Aug 2009 04:23

Yesterday's topic was a quick diversion back to ULTRA, but today we continue with day 3 of the complex sysgen topics. Today's topic is about stellar disks. In ULTRA STARFIRE the stellar disk is not considered a separate object of interest and is only indirectly considered, with only two types: empty disks and planetary disks.

They can be soooo much more. And they can affect everything from the placement of system bodies to how far WP can be from the star. It all depends upon how you treat them.

Even more so as we delve deeper, these charts are being converted for ULTRA so they may not always make the most sense. There are still some missing or incomplete parts which will be noted. So any ideas are welcome!!


There are essentially four kinds of disks: empty disks, bare disks, asteroid disks, and planetary disks. The chances of each and the maximum size of the disks is dependent upon the stellar class (color):

Blue01-5051-95NA96-00160050% (-5 terrain type roll)
White01-4041-7071-7576-00140010% (-3 terrain type roll)
Infrared Giant01-85NA86-9091-0011001%
White Dwarf******1%
Black Dwarf******0%
Radio Pulsar******100%

WD = white dwarf, BD = black dwarf, IR = infrared giant, Radio = radio pulsar
* Roll an original star type, that is the star when the disk was fully formed. Use that data. Then make the minimum disk size depend upon how big the star got, all planets and asteroids in radius destroyed, max disk size is assumed 200, as below:
WD was red giant
BD was red giant
Pulsar, Radio Pulsar, and Neutron Star have no disk and have a max disk size of 100.

Modifiers to Disk Type Roll:

Modifiers to Max Disk Size:
Super-giants+25% size
Giants+10% size
Sub-dwarf-20% size

Poly-star systems still limit disks as per the ULTRA STARFIRE rules (1/3 limit, 1/4-1/3 is turned to asteroid belts)

NO-DISK: This simply means an empty disk. Skip everything and go straight to WP.

BARE DISK: This simply means that nothing here is large enough to be an asteroid or a planet. It is "bare" of system bodies.
01-33Proto-disk (treat as reflective nebula)
34-66Dust disk (treat as dark nebula)
67-00Unformed Planetary Disk (treat as dark nebula, but roll planetary orbits. the orbits are clear of nebula)

ASTEROID DISK: Whether through gravitational disturbances, or simply too many collisions, this disk is full of asteroid belts and little else. Roll orbits as normal, but roll below for each orbit:

massis planetis beltis nothing

PLANETARY DISK: Ah, the planet-filled disk of joy. I haven't settled on a good way to do "large gas planets" like we see, so I'm going to ignore that for now. Krenshala has a method that might work, so maybe he'll present it here.

Orbits are done with the Titus-Bode Relation: R = A (B * 2^n) where A is the first orbit in LM, B is the second orbit minus the first in LM, and n is the orbit sequence - 2 (so you start with orbit 3 to get n = 1).

Tidelock zones are pre-calculated because there is a wide disagreement about how much luminosity affects the tidelock effects of a star. I haven't found any real agreement so have used some fixed values:

Blue5 LM14 LM45 LM260 LM
White0 LM4 LM6 LM52 LM
Yellow0 LM1 LM3 LM20 LM
Orange0 LM1 LM2 LM11 LM
Red0 LM1 LM2 LM10 LM

Infrared Giant uses Red Giant (2 LM)

Later in planet generation we will see that I use luminosity to calculate the black body temperatures of each planet to determine its type. Here we will use generic values to get a feel for the rocky, gas, and ice zones.

Rocky => 0 to gas zone
Gas => 200 K = 1110 * (sum * (L / (4 * a ^ 2))) ^ 0.25 to Ice
Ice = > 60 K = 1110 * (sum * (L / (4 * a ^ 2))) ^ 0.25 to the end of the disk

where L = luminosity of the star, a = orbit radius in LM, and sum = number of stars.

NOTE: Later for poly star systems you'll see that I add up all the luminosities and average the distance from the orbits to each of the stars. This gives us the average temperature. For extremes simply use the average of the closest distance to all the stars, and the average of the furthest distance.

Now we need to find out what size of planets, etc.

01No System Body at the orbit*
02-04Asteroid Belt *
05-29Mass 1 Planet
30-85Mass 2 Planet
86-00Mass 3 Planet

* in the case of alternate development, if this planet has a predetermined size or distance then ignore this result

modifiers: blue star +8, white star +3, red star +4, rocky zone -5, gas zone +10, ice zone +5

Before we can do anything else, we need to determine if gas giants turned any of the planets into belts. If the previous orbit is already a belt, or is nothing, then ignore. Start with the outer most gas giant and work inwards.

mass 1: 1% chance
mass 2: 8% chance
mass 3: 12% chance
mass 4: 20% chance

From here we have the disk type, any orbits and their composition, and the chance of terrain. From here we will dive into terrain and then planet generation.

Thoughts? Comments?
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Re: Sysgen Topics*: Stellar Disks (day 3)

Postby Crucis on Wed 12 Aug 2009 10:43

How's about using a "CODE" block for those multi-column tables to make their format readable?
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Re: Sysgen Topics*: Stellar Disks (day 3)

Postby Cralis on Wed 12 Aug 2009 12:52

I match your [.CODE], raise the stakes with [.TABLE] and CALL. Whatcha got? :mrgreen:

PS. For anyone who wants to try and use these, ABSOLUTELY make sure you do it right.
Code: Select all
The table BBCodes use comments. YOU ABSOLUTELY MUST enclose your tables with the table tags or you will booger up the display of your entire post, and I will probably be forced to delete it.

[table][/table]   <-- MUST enclose all tables with this
[r][/r]           <-- row tags, start and end
[c][/c]           <-- column elements, start and end

If you miss a column or row ending tag your table will look funny. If you miss a table ending tag, your post will probably get deleted as everything after the table will be commented out (the entire web page). So use with caution :)
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Re: Sysgen Topics*: Stellar Disks (day 3)

Postby BillW on Wed 12 Aug 2009 19:13

I know this is just one picky detail out of a large post, but... Under Bare disk one of the possibilities is "Unformed Planetary Disk (treat as dark nebula, but roll planetary orbits. the orbits are clear of nebula)". It seems to me that if something is sweeping the nebula clear in the "planetary" orbits then there should be some sort of proto-planet there. Probably not much good for colonization, but maybe they could be mined like an asteroid?
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Re: Sysgen Topics*: Stellar Disks (day 3)

Postby Cralis on Wed 12 Aug 2009 21:46

Of course there is a proto-planet, but that is something I had not thought about. They would essentially be hot balls of gas and half-formed rock, but I imagine there is probably something to mine out of them - if nothing else hydrogen and organic compounds. But they wouldn't be livable in any way...
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