[Space] System Generator

[Pragmatic]

So how does spreadsheet handle user input?

And can it create trinaries? Double planets? Two garden planets in the life zone? (It's just barely possible, with finagling hydrography and atmospheric density and stellar luminosity, to have a Warm/Cold or a Tropical/Cool pair.)

I can finagle to make the special systems like the one above (yes, it'd be a VERY special system :) ), but was dreading populating the rest of the Known Quadrant with random, generic systems. I'm very much looking forward to seeing the completed spreadsheet, and want you to know I appreciate your efforts. And I'm glad it's not ME that's doing the programming! :)

Thanks!

[Pragmatic]

I did a very minor spreadsheet that calculates orbital radius based on a range of average surface temperatures (the boundaries and midpoints from the bottom of Cold to the top of Hot), stellar luminosity (assumed to be 1.0 Sols, but can be overridden), atmospheric mass (from 0.5 to 1.5), and hydrography (each of the four possible, 01-20%, 21-50%, 51-90%, and 91-100%).

There are a total of 660 calculations showing planets within the acceptable range, with wildly varying habitability. So I highlighted prime real estate: Hydrography of 51-100% and atmospheric mass of 0.8 to 1.2.

That reduces to 150 main calculations. Then I decided to highlight further: I shade out planets that are less than 0.755*(Lumin)^0.5 or more than 1.331*(Lumin)^0.5. (Can't exactly remember why I chose those limits. I think those limits are from the blackbody temperature equation on page 113, solving for R in terms of Lumin, substituting in the Blackbody Correction equation from page 84 to get Absorption Factor, Greenhouse Factor, and Atmospheric Mass.)

So I pick out a planet I like. For example (Lumin=1.0), surface temp of 272.0 (Chilly) in the "sweet spot" range (hydrography 51-100%, atmospheric mass 0.8-1.2) has radii in the range of 0.9378 to 1.1494. The best will be 1.0885.

Next I go to the tab which computes higher and lower orbital radii. I have ratios of 1.4 to 1.9 (easy enough to add 2.0...). It only looks at "sweet spot" planets, and of these, I see I can get 307.0 (Warm) with 1.0 atmospheric mass and 91-100% hydrography at radius 0.7775.

So there's our first pair: Chilly (Lumin 1.0, 1.09 AU, 1.0 atm, 51-90% hydro) and Warm (Lumin 1.0, 0.78 AU, 1.0 atm, 91-100% hydro), an improbable 1.4 ratio.

Another pair: Tropical (Lumin 1.0, 0.76 AU, 0.8 atm, 51-90% hydro) and Cool (Lumin 1.0, 1.06 AU, 1.2 atm, 91-100% hydro), another improbable 1.4 ratio.

My spreadsheet is only focused on finding pairs of reasonably compatible worlds. Unfortunately, they all rely on the improbable roll of getting a 1.4 ratio (at least, my attempts to get Chilly/Warm and Cool/Tropical pairs). If one is willing to accept further extremes (Chilly/Tropical, Cool/Hot, Cold/Tropical, or even Cold/Hot), it's more probable. I've found that, with the limits I use (0.755*Lumin^0.5, 1.331*Lumin^0.5), it's impossible to get Normal and anything between Chilly and Tropical.

Yes, I'm rambling. :)

[Pragmatic]

Any chance of including the rules from GURPS Traveller: First In about Very Close binaries? It was one of the ways I increased the Life Zone of systems without putting in short-lived super-bright stars. :)

[Captain Joy]

Originally Posted by Agemegos

The [atmospheric composition] rules are on p. Space79. I constructed a table with world type in one column, basic atmosphere as described in another, its constituents in another, chance to have a worse atmosphere in the next, what it is if it is worse in the next and what constituents you get in the worse atmosphere in the next. The a few simple table look-ups generate the data.

I looked up the composition of gas giant atmosphere in a planetology text-book.

Oh, I saw that you'd listed trace gases for a gas giant and I thought you had some nonRAW system for generating trace gases for terrestrial planets as well. I assume then that all your gas giants will have a listing: "traces &c. NH3, H2S, HCN", correct? Terrestrial planets will have trace gases as determined by RAW.

I really would like to see percent composition rating for these atmospheres. E.g. 90% H, 10% He, trace &c. NH3, H2S, H2O. I know you would too. :)

[Pragmatic]

Originally Posted by Agemegos

Exactly so.

Please forgive me if these are REALLY stupid questions:

Would the MMWR (pg 86) have anything to do with trace gases? Or vulcanism? Age of planet (e.g., early on Earth had trace oxygen)? Type and age of star? Stellar location in galaxy?

[Pragmatic]

A suggestion: sample random creatures, appropriate to the world in question. Two or three, just to give visitors something to kill and loot. :)

After all, it's in GURPS Space 4E, as well. Yes? :)

[Pragmatic]

Originally Posted by Agemegos

I can tell that you have been following the thread very carefully.

Yup. Obvious, isn't it? :)

I come in and read the thread every few days. Unfortunately, the forum doesn't save unread posts, so I miss a few pages if I forget to visit the general GURPS forum (I'm eagerly awaiting Martial Arts, so generally check that forum and forget the rest).

I take it that is a topic which has reared its leonine head, howled at the moon, slithered around, and other animal metaphors? If it was, I either didn't see it (always a possibility; due to the "mark all threads read a day after visiting" problem has left a LOT of threads unread by me) or possibly just forgot (harder to conceive: I'm a critter fan, and my memory isn't THAT bad).

[Pragmatic]

Originally Posted by Agemegos

It never got anywhere so neat the front of the queue before. The focus group have been struggling to get me to do RVM, atmospheric composition, partial pressures of main constituents of the atmosphere, day length, atmospheric pressure on tidelocked worlds, amplitudes and frequencies of components of the tide, seasonality, and such strictly physical things.

Ah. Those are all dandy. Want me to chime in to add to the pressure? :)

The question is, are they things YOU want? Because as far as I know, you're not getting paid. There's only three reasons to do anything: love/enjoyment, money/rewards, and curiosity. The second doesn't apply, so it's either the first or the last.

What game mechanics do all those things have, by the way? If there are no game mechanics, I say fudge it: given the planet being in a certain range, it'll return a random (possibly weighted) result from a portion of a table. Or just give relative ranges (e.g., partial pressure for planets of type A for O2 might give a range of "0.8 to 1.7 widgets"--sorry, don't know the units), with some overlapping. That way, the GM can decide what value to use.

Now, critters, on the other hand, definitely have game mechanics! :)

[Pomphis]

My condolences. But even if you shoot the accountant and the electrician, hesitate and reconsider a moment before shooting the family. I believe it can take a lot longer to replace a family than to find another accountant and another electrician. Besides, many cleaning ladies don´t like that much blood.

And while I am deeply sorry for having to remind you of your duties: you _are_ The Bartender of the Faith, and therefore clearly cannot kill yourself before having found a worthy replacement and having received His blessing for resigning from this position, which is after all one of the oldest and most central offices of our faith.

[Pragmatic]

How's going the recovery effort?