[Space] System Generator

[Pomphis]

Originally Posted by Agemegos

Right. Here is the very latest sample output.
(snip)
Give it some thought.

a) I assume "infinite" solar day means "Tidelocked" ?
I would prefer Tidelocked then, as that´s the term used in the RAW (index) and the one I would google for.

b) Earth has HI 8. If earth is the gold standard, one could argue that HI 8 should get a seperate color. I don´t really see HI 3 as being habitable. HI 4 can be a breathable atmosphere but with no surface water and extreme climate, so I see HI 4 as the lowest interesting level. Which would mean HI 8, HI 6,7, HI 5,4, would each get a color.

c) The other color-coding would be chrome. Atmosphere, Hydrographics, Temperature are spelled out, and are short enough that a color doesn´t really save time reading. OTOH color might be used for other information: a red dot after world type could indicate high volcanism, a color code for Hydrographics could be used to indicate presence and complexity of native life for example.

d) Even if it would be an exemption: the world type row has enough space after "asteroid belt" to add the resource level. As that´s pretty much the only thing of interest in a belt, how about showing it ?

[Pomphis]

Originally Posted by Agemegos

But in the case of tide-locked worlds there is a problem. The rules tell you to 'adjust pressure accordingly', but provide no no way of determining by how much atmospheric mass is reduced. I cannot calculate the actual pressure for tide-locked worlds using the rules as written.

I'm not averse to having the number as well as the category—that is what I do for temperature, after all. But I am reluctant to axe the category because that is what has effects in terms of game rules. This is a game aid (although it masquerades as a game-world document), and I like to save the GM one step in working out the game-mechanical effects on characters. This way, they need neither memorise nor find and look up the pressure categories.

a) Space p.125 gives no change for Standard to Superdense. None is 0, Trace is less than 0.01. The only problem is the Thin to Very Thin change. Thin is 0.51-0.8, Very Thin is 0.01-0.5. How about simply subtracting 0.4 ? We don´t really know anyway, and I would much rather have a possible error of about 0.1 in this one special case than not to know whether I have 1.6 or 9 atms for example.

b) I would prefer both. I only mentioned the possibility to use the number instead of the category if some other change would make space that sparse. But right now the atmosphere row has enough space for both.

[zorg]

Originally Posted by Pomphis

Which would mean HI 8, HI 6,7, HI 5,4, would each get a color.

That leaves us with one color un-used - perhaps for HI 3 and below?

I find that color-coding not only makes a table easier to read, but also more pleasing for the eye (unless you use bright neon colors, obviously). I vote for using as much color coding as possible.

[Captain Joy]

Originally Posted by Agemegos

Those two large close moons are a problem, though. I haven't implemented the spacing of moons correctly, because the RAW amount to 'do it over until the moons are spaced out', which I can't do with a spreadsheet. My plan to address this is to roll a distance for the first moon and then apply the orbital spacing rules to space the others.

Oh ya, I remember having to deal with that. IIRC (my computer is not with me) I did something like generating random relative spacings, then converted the relative spacings into actual distances. Then, you can calculate tidal forces.

Originally Posted by Agemegos

There will remain the problem that the tidal interactions that slow the planet ought also to move the moons to higher orbits.

Who's to say the moons weren't closer a few billion years ago? I.e. The effect of random placement is much greater than the effect of tide locking increasing the orbit.

Originally Posted by Agemegos

I would be open to an argument that the initial periods of gas giants ought to be more centrally peaked than those of asteroids on which I based my mechanics for planetary rotation.

What? This sounds as if you didn't use the RAW to generate the planetary rotation parameters?

Originally Posted by Agemegos

No, but it seems like common sense. Atmospheric pressures in gas giants are ludicrously high. And gas giant atmospheres contain ammonia, IIRC.

I've considered adding the actual atmospheric composition to all planets in general. E.g.

Sol III: N2 78%, O2 21%, Ar 1%
Sol V:   H2 90%, He 10%, CH4 0.07%
Sol VIa: N2 92%, Ar 6%, CH4 2%

Generating random planetary atmospheres was something I wish was included in GURPS Space.

[Captain Joy]

Originally Posted by Agemegos

Here's sample output for the world data sheet.

I'm intrigued by the "daily ±" for surface temperature. I'd be interested in a "seasonal ±" as well. How are you planning on determining these?

And I see you've only got one line for "main gases". It will be difficult to list the main gases and their % abundance in such a small space. Shall I assume this was a simple oversight and will be promptly corrected? :)

Getting back to how you calculate rotation period. You're using a corrected RAW, no? I know GURPS Space is in dire need of an errata update. But, you know what the errata should be, and you've applied it, and that is how you got your rotation periods, right?

[Rupert]

Originally Posted by Agemegos

Commentary on the content and layout of teh left-hand column, please.

Oxygen partial pressure or percentage would be nice, if it's available.

[Captain Joy]

Originally Posted by Rupert

Oxygen partial pressure or percentage would be nice, if it's available.

Oxygen partial pressure is an excellent idea in a human-centric universe. In fact, oxygen partial pressure in Earth partial pressure units would be perfect.

[Rupert]

I think it's useful even without any humans in the universe at all. For one thing, if the intelligent species use oxygen it'll still be useful, and for another, the amount of oxygen available in the air has a major impact on the maximum size animals are likely to grow to, and on how big things like insects that rely on gas diffusion rather than lungs can grow.

[Captain Joy]

Originally Posted by Agemegos

I am more tempted to write out the names of the compounds to remain accessible to people who don't know what NOx and NH3 are.

You could use the shorter notations in the table, and then add a key as a footer or something. E.g. O2 = oxyger, N2 = nitrogen, etc.

Originally Posted by Agemegos

It would. I'd also like to have the boiling point of water at the surface. Neither is available.

The partial pressure of O2 is just: partial pressure of O2 = mole fraction of O2 * total pressure. So, the

partial pressure of O2 on a planet in earth normal units 
= (mole fraction of O2 on planet * atmospheric pressure on planet)
     / (mole fraction of O2 on earth * atmospheric pressure on Earth)
= (% by molar content/volume of O2 by number on planet * atmospheric pressure on planet in atm)
     / (21% * 1 atm)

Maybe if/when you start determining the actually abundances you could add this feature.

The boiling temperature of water is a function of pressure. You could use a good water phase diagram to approximate what that function is.

Originally Posted by Agemegos

I think I had better add escape velocity.

and mass?

Originally Posted by Agemegos

Is pressure in bar alright, or should I add kPa (and eventually p.s.i)?

Bars is alright. Btw, what's the difference between the units bars and atmospheres?

[Rupert]

Originally Posted by Agemegos

I think I had better add escape velocity.

Is pressure in bar alright, or should I add kPa (and eventually p.s.i)?

I'm fine with bar.