Planets

>Okay boys I got a real mean question.  Has anyone figured out an easy way to
>generate the: length of day, year, and seasons of a planet created using the
>advanced rules in Scouts (Book 6), or the new MegaTraveller Rules.  I would
>greatly appreciate any help on this, since I really need to generate this
>type of information for a game I am running.
>
Brad,
  Starting on page 43 of Book 6 Scouts, under Orbital Data, all of the data
is presented to compute orbital distances and temprature.  There is some errata
that was presented in an issue of the Journal of the Travellers Aid Society.

To compute orbital period (year), you need the Mass of the Star in Solar Masses
(Interpolate value from chart on Page 45, Type D stars are VI on this chart.)
Lets assume a F8v star, its stellar mass is 1.114 (40% between G0 and F5).
Next we need the distance in AU, here you need the orbit of the world and get
the distance in AU from the chart on page 46.  For an F8v star, the habital
zone is between orbits 3 and 4, so we will place it in orbit 4, or 1.6AU.

The orbital period is  Period = (Distance**3/Mass)**0.5 or 1.917509 Terran
Years.  Then multply by 365.25 to get days.

If you want to get seasonal data, you can use the Exxentricity chart on page 48
(change Temperature to Lumiosity in these charts).

An inverse formula is given if you know period and mass to derive distance, it
is  Distance = (Mass*Period**2)**0.33  Where Period is Terran Years.

The same formulas work for satellites where Period is in lunar months (28 days)
and Mass is combined Earth Moon Masses and distance is in Earth Moon Distances.
(400,000 Kilometers)

Now for temprature,
  Temp = 374.025 * Greenhouse (1-Albedo)(Luminosity**.25)/Distance**.5

So for our example, we will use a Greenhouse effect of 10% (1.1) and an Albedo
of .3 (Earth Like reflectance)  The Luminosity is 1.326 and the Distance is
1.6AU (Now this should yeild a slightly cool planet, since the real habitable
zone is orbit 3.5 and we are in orbit 4.  We get 244.32 degrees Kelvin,  Terran
average is 288 degress kelvin, so our world is 44 degrees colder than earth on
the average.  Feel free to adjust the orbit to bring tempratures with in
tolerances.

There is a second formula that takes the temperature and gives distance.  It is
in error in Scouts, the correct formula is:

  Distance = (Luminosity**0.5)*(GreenHouse*374.025*(1-Albedo)/Temp)**2

Now as far as the day lengths go, there isn't a way presented.  I am not a
physics dude, but I would guess that the size of the planet and its orbit
control the speed of rotation.  For simplicity sake, assume that a size 8 world
rotates in 24 hours, the smaller the faster, the larger the slower.  I am sure
that a quick formula somewhere.
- --
Rob Miracle              | Bitnet   : [email removed]    CIS: [email removed]
Programmer/Analyst-II    | INTERNET : [email removed]
University of Louisville | UUCP     : ...[email removed]

This looks like it's meant to reply to the planets question.

- ------- Forwarded Message

Date: Thu, 16 Mar 89 20:03:45 EST
From: Stuart Stirling [email removed]

[... copy of Brad's message ...]
Try Scouts, pages 43 and 46; Grand Survey (Digest Group: 1986), pages 26-27.
[... signature ...]

- ------- End of Forwarded Message

>Okay boys I got a real mean question.  Has anyone figured out an easy
>way to
>generate the: length of day, year, and seasons of a planet created using
>the
>advanced rules in Scouts (Book 6), or the new MegaTraveller Rules.  I
>would
>greatly appreciate any help on this, since I really need to generate this
>type of information for a game I am running.
Unless I am mistaken a  formula for computing the length of the year is in fact
given in book 6
if there isn't a formula there The following should work:
        (r^3/2)/(m^1/2)
where r is the star-planet radius in AU and m is the stars mass in solar
(earth sun) masses. The result is given in earth years.
the length of day is highly variable and there isn't really any way to generate
it using any formula one good way might be to roll 7 dice and add them together.
This will generate results that fit roughly into an acceptable range (7 is a
little low, but is sufficiently rare) and will center around 24 hours which
seems to be a number conducive to human life
As for the seasons this is a diffucult question, as a season is really a change
in the climate. And as the climate at a given point on the surface of a given
planet is a function of a lot of variables I can't think of any way of
predicting the season without working it out on a case by case basis.
The equinoxes and solstices will however follow the same progression as they do
here being separated by 1/4 of the year.
I hope this was of some help.
        -Love Kisses and a Neutron Bomb
                -Eric the Finn
internet: [email removed]
bitnet: [email removed]

Does anyone have a copy of those pages online, the ones the guy just mentioned
only because my Scout book is 3000 miles away, and I don't find the info in the
MT rules.

Thanks.

Brad

There are some rules expanding the _Scouts_ system of world generation
published in the _Traveller_ supplements _Grand_Survey_ and/or
_Grand_Census_ (published by _The_Digest_Group_). These rules covered
local day length, possibility of locked rotation (day length same as
year length), orbital tilt (angle of polar axis) and means of computing
local (i.e. longitude and latitude) mean temprature from the other factors.

The rules (one book or the other, can't remember which) also suggested how
to create the continents of a world, how to allocate the population and
how to compute technology spread over a world (different in starport and
in the outback).

There is other things there too, that I can't remember right now, but they
expanded government and law levels, I belive. Great books for creating
consistent worlds, but that requires _some_ amount of work.