Captain Joy wrote:
Thomas Thrien wrote:
> First I am used to Roman digits for the planets of a star.... Greek
> letters are usually used for naming the stars in a multi-star
> system.... also
> ... name the main star with Major and the second with
> Minor.
I will immediately adopt this convention.
Please repost with the changes.
All of the above should be pretty easy to include, except for the
atmospheric composition and seasonal variation. Can anybody offer
advise on how to randomly generate realistic atmospheric compositions
and realistic seasonal variations in actual °C (or °F). Using our own
Solar System, GURPS: Space Atlases, and GURPS: Prime Directive as
models, I think I'll be able to come up with something; but if anybody
has any other suggestions, I'm all ears.
See if you can get your hands on "GURPS Traveller: First In"; it is
the immediate predecessor of GURPS Space's world design sequence. It
might be difficult to acquire, though; according to the SJGames
website, it's out of print.
The latest edition of Star Hero is also worth checking out for
inspiration; it has a planetary design system that falls somewhere
between the one found in GURPS Space and the one found in First In.
You can go to DriveThruRPG.com and pick up a digital copy of the
Traveller: New Era supplement "World Tamer's Handbook", which provides
some (rather sketchy) details about determining temperature
variations. The main thing to get from it, though, is the sorts of
topics addressed: the effects of orbital eccentricity, the effects of
latitude, seasonal variation, and day/night cycles.
The effects of orbital eccentricity are easy to determine, in theory:
figure out the planet's closest and farthest distances from the star;
recompute blackbody temperature for each of those distances, and
adjust the planet's climate accordingly. This can be simplified: to
find the planet's maximum blackbody temperature, divide the given
blackbody temperature by sqrt(1-E), where E is the eccentricity; to
find its minimum blackbody temperature, divide by sqrt(1+E).
Seasonal variation ought to be tied to the effects of latitude; after
all, what's really going on is that a given region of the planet has a
lower effective latitude (relative to the sun) during Summer than it
does during Winter. As such, figure out the temperature variations by
latitude for spring and fall using an as-yet undetermined system, and
determine seasonal variation by adding or subtracting the axial tilt
from the given latitude.
I'm not quite sure how to handle the latitudinal variations; IIRC,
First In had a system for that which might be adaptable to GURPS
Space.
As for Day/Night variations: Something needs to be hacked together for
this. You do have a starting point to work with, though: the
temperature variation due to the day/night cycle will be less than the
dayside/nightside variation that an equivalent tidal-locked world
would have. How much less, I'm not sure.
For atmospheric composition: the World Types table is based on the
notion of the competition between the world's gravity and the
atmosphere's temperature: high gravity and cool temperatures tend to
retain lighter elements in the atmosphere, while low gravity and warm
temperatures tend only to retain heavier elements. There's a way to
compute the minimum molecular weight retained from the planet's
surface gravity and blackbody temperature, although I don't know the
formula off the top of my head; with that and a list of possible
atmospheric gasses and their molecular weights, you have a potential
breakdown of atmospheric compositions. Tweak the figures by looking
at potential chemical interactions that would remove certain gasses
from the atmosphere, as well as including possible sources of
replenishment. Star Hero is a good source of material for this sort
of thing, although World Tamer's Handbook also addresses it.
I'd limit such details to non-Garden worlds, as GURPS Space already
has a fairly robust system for determining the atmospheric composition
of Garden worlds.
--
Jonathan "Dataweaver" Lang
_______________________________________________
GurpsNet-L mailing list <[email protected]>
http://mail.sjgames.com/mailman/listinfo/gurpsnet-l
