>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.
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