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PostPosted: Mon Apr 03, 2017 3:04 am 
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Thank you!


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PostPosted: Mon Apr 03, 2017 3:11 am 
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I was in the middle of posting about playability when EDG posted, the gist of what I was saying is most Traveller games I've played in pay little heed to the worlds around them and have very little adverse environments to challenge players. It's a very shirt-sleeve universe.

For the sake of having fun and well, playing Traveller, that works fine but if you want to use a harder setting I think you need to invest some time in finding where your setting ideas meet realism. It's not everyone's idea of fun to deal with 40 degrees kelvin or methane seas and even when you find an oxygen rich atmosphere, you're still wearing an environment suit because you don't yet know every little bacteria or virus that's floating around unseen...


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PostPosted: Mon Apr 03, 2017 11:19 pm 
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Sir Chaos wrote:
So... sorry. I´m pretty sure working with orbital resonances as you originally suggested would create great (and quite possibly more realistic) planetary systems than what I settled on, but the complexity of the math involved puts it beyond the scope of what I want to do.

It needn't be too bad, though whether it meets your criteria is a matter of how good the user is at mental arithmetic. Two digit by three digit multiplications ought to be good enough.

Start at the innermost planet and work outward, or at the outermost and work inward, or at the most important one and work both ways. Roll dice. Consult at table, which will tell you what resonance is next and give you an orbital radius factor. Multiply the current orbit's radius by the factor off the table to get the radius of the next orbit, rounding up. Very like what GURPS Space 4th ed. does (Step 22, pp108–109), except that having radius factors of 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0 you have factors corresponding two the 2/3 power of common small-integer ratios: 1.21 (4:3 resonance), 1.31 (3:2 resonance), 1.37 (8:5 resonance), 1.41 (5:3 resonance), 1.45 (7:4 resonance), 1.48 (9:5 resonance), 1.59 (2:1 resonance), 1.76 (7:3 resonance), 1,84 (5:2 resonance), 2.08 (3:1 resonance).

You can master a lot of difficult calculations with table look-ups.

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PostPosted: Mon Apr 03, 2017 11:38 pm 
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EDG wrote:
I'd say "playability" doesn't really matter. If you're a GM making worlds then you're doing that beforehand in your own time, and all you're doing in play is presenting whatever information is relevant to the players.

If generating content that will be presented to the players were the only goal we would all be using some sort of script or program, because everyone has a computer now. Those of us — and others — who are still interested in procedures that are executed by a human are so interested because world and sector generation by manual methods is a kind of solo game that they enjoy doing. They don't want implausible results, but they are interested in the process and not just in the results.

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PostPosted: Tue Apr 04, 2017 9:51 am 
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My question concerns migrating gas giants. As a gas giant migrates towards the inner orbits, what happens to any rocky planets that are already there? For example, if a giant migrates to .3au, can another planet be in any orbits beyond that unless it too migrated from the outer system? How can a planet migrate upwards out of the gravity well without disrupting other worlds by pullimg them down or out of the system? Under what conditions would it lead to the creation of a belt and under what conditions would it sweep a belt away?

We should keep in mind that we are only taking a snapshot of a relative instant in the life time of a system.

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PostPosted: Tue Apr 04, 2017 4:35 pm 
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Agemegos wrote:
Sir Chaos wrote:
So... sorry. I´m pretty sure working with orbital resonances as you originally suggested would create great (and quite possibly more realistic) planetary systems than what I settled on, but the complexity of the math involved puts it beyond the scope of what I want to do.

It needn't be too bad, though whether it meets your criteria is a matter of how good the user is at mental arithmetic. Two digit by three digit multiplications ought to be good enough.

Start at the innermost planet and work outward, or at the outermost and work inward, or at the most important one and work both ways. Roll dice. Consult at table, which will tell you what resonance is next and give you an orbital radius factor. Multiply the current orbit's radius by the factor off the table to get the radius of the next orbit, rounding up. Very like what GURPS Space 4th ed. does (Step 22, pp108–109), except that having radius factors of 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0 you have factors corresponding two the 2/3 power of common small-integer ratios: 1.21 (4:3 resonance), 1.31 (3:2 resonance), 1.37 (8:5 resonance), 1.41 (5:3 resonance), 1.45 (7:4 resonance), 1.48 (9:5 resonance), 1.59 (2:1 resonance), 1.76 (7:3 resonance), 1,84 (5:2 resonance), 2.08 (3:1 resonance).

You can master a lot of difficult calculations with table look-ups.


I don´t have linear radius factors in the current line of thought - I have logarithmic ones, currently leaning towards calling them "orbital shells": Shell 0 is at 1/128 AU, a bit less than 1.2 million km, and Shell 70 is 1 AU. A distance of 10 shells doubles radius. So with 1d6+4 shells between two occupied orbits, we´d be at 1.41, 1.52, 1.62, 1.74, 1.87 and 2.0 approximately.

The advantage I see in these is that, with luminosity and black body temperature also abstract values on a logarithmic scale, and the change of energy received over distance subject to the inverse square law, black body temperature decrease from shell to shell is nicely linear: -1 per shell.

On the other hand, using the ratios you supplied, calculating black body temperature change from one occupied orbit to the next is going to awkward. At the distance for a 2:1 orbital resonance, the difference in black body temperature would be about -6.69 on the logarithmic scale, or about -60.4% energy received.

Although... we could always call those radii approximate numbers. A shell isn´t really a narrow circle with an exact radius, it´s a region of space extending about 3.6% in either direction (each shell is about 7.2% further out from the star than the previous one).

Let´s say you roll 1d6 and check the result on a table:
1 - 3 shells (factor 1.23 - close to the 4:3 resonance)
2 - 4 shells (factor 1.31 - 3:2 resonance)
3 - 5 shells (factor 1.41 - 5:3 resonance)
4 - 7 shells (factor 1.62 - close to the 2:1 resonance)
5 - 8 shells (factor 1.74 - close to the 7:3 resonance)
6 - 9 shells (factor 1.87 - close to the 5:2 resonance)

This way, I can continue to use my shells, (abstract) black body temperature continues to be easy to determine, and the orbits are close enough to being scientifically justified for a layman´s work.

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PostPosted: Tue Apr 04, 2017 6:47 pm 
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I've taken down the worldgen temporarily as I figure out how or whether to Cepheus-ize it. I'm just not really convinced it's worth the time and effort to do more with, since it's likely only a handful of people would care about it anyway so I might just put it back up as is.

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PostPosted: Tue Apr 04, 2017 7:50 pm 
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EDG wrote:
I've taken down the worldgen temporarily as I figure out how or whether to Cepheus-ize it. I'm just not really convinced it's worth the time and effort to do more with, since it's likely only a handful of people would care about it anyway so I might just put it back up as is.


For what it´s worth, I think your worldgen would work well as the Cepheus equivalent to the rules in the CT Scouts book.

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Space isn't remote at all. It's only an hour's drive away if your car could go straight upwards. Sir Frederick Hoyle
Earth is the cradle of humanity, but one cannot live in a cradle forever. Konstantin Tsiolkovsky
Man has earned the right to hold this planet against all comers, by virtue of occasionally producing someone completely bat**** insane. xkcd #556
Just like people, stars can be very important without being terribly bright. Phil Plait, "Bad Astronomy"


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PostPosted: Tue Apr 04, 2017 9:02 pm 
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EDG wrote:
I'm just not really convinced it's worth the time and effort to do more with, since it's likely only a handful of people would care about it anyway ...

You could be wrong. The Cepheus System seems to do very well, and what DTRPG currently has to offer concerning star system generation also seems to do well - at least well enough to reach the "Best Copper Seller" level. Of course, this is not a reliable prediction of a success, but I think it would have a good chance to be worth the effort.


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PostPosted: Tue Apr 04, 2017 9:06 pm 
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Sir Chaos wrote:
Agemegos wrote:
You can master a lot of difficult calculations with table look-ups.


I don´t have linear radius factors in the current line of thought - I have logarithmic ones, currently leaning towards calling them "orbital shells": Shell 0 is at 1/128 AU, a bit less than 1.2 million km, and Shell 70 is 1 AU. A distance of 10 shells doubles radius. So with 1d6+4 shells between two occupied orbits, we´d be at 1.41, 1.52, 1.62, 1.74, 1.87 and 2.0 approximately.

The advantage I see in these is that, with luminosity and black body temperature also abstract values on a logarithmic scale, and the change of energy received over distance subject to the inverse square law, black body temperature decrease from shell to shell is nicely linear: -1 per shell.

On the other hand, using the ratios you supplied, calculating black body temperature change from one occupied orbit to the next is going to awkward. At the distance for a 2:1 orbital resonance, the difference in black body temperature would be about -6.69 on the logarithmic scale, or about -60.4% energy received.

Although... we could always call those radii approximate numbers. A shell isn´t really a narrow circle with an exact radius, it´s a region of space extending about 3.6% in either direction (each shell is about 7.2% further out from the star than the previous one).

Let´s say you roll 1d6 and check the result on a table:
1 - 3 shells (factor 1.23 - close to the 4:3 resonance)
2 - 4 shells (factor 1.31 - 3:2 resonance)
3 - 5 shells (factor 1.41 - 5:3 resonance)
4 - 7 shells (factor 1.62 - close to the 2:1 resonance)
5 - 8 shells (factor 1.74 - close to the 7:3 resonance)
6 - 9 shells (factor 1.87 - close to the 5:2 resonance)

This way, I can continue to use my shells, (abstract) black body temperature continues to be easy to determine, and the orbits are close enough to being scientifically justified for a layman´s work.

Very good! You can also tame a lot of fiddly calaculations using logarithms!

Given this approach I would be rather inclined to do thing a bit like the way the ForeSight planet generator did. Don't make the orbitals a fixed radius: make them a fixed blackbody temperature. That is, start with shell 0 without committing to what radius it has. At the end of the process add a constant and the log of the star's bolometric luminosity to each of the shell numbers to get the log of orbital radius.

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My SFRPG setting, Flat Black

© My posts on SFRPG must not be reproduced beyond the board except with explicit permission from me.


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