Originally posted by Ghunkugoe:

** Can you post the spreadsheet somewhere that we can al grab it? Or at least post here the petinent formulae?**

Thanx

Spreadsheet is unreadable without much interpretation.

Tide = 2*G*M/R^3 (Calculate tidal forces)

G=6.67E-11 (Gravitational Constant)

Me= 5.98E+24 (Mass of earth)

Ms= 1.99E+30 (Mass of Sun)

Mw = (Density * Diameter(kMi)^3 / 2750)* Me (Mass of world is Density * Diameter cubed * Mass of Earth) in Kg.

Some sources give stars masses in terms of solar messes which is where Ms comes in useful.

Density varies from 0.7-1.3 for gas giants and about 2-7.7 for planets.

Diameter is given on p375 of the T20 book. The formula above assume diameter is in miles however and you will have to convert.

Tide = 4E-13 (Force at safe distance)

T/2G = 3E-3 (Tidal force / 2 * G, a constant)

As stated above, the tidal force is calculated so the force around an average density planet comes out at about 100 diameters. To calculate the safe distance for a given world of size D and density R

Distance = cube root (Mass / T/2G)

This distance is in meters from the center of mass. You will have to convert to your favorite units.

In reality tidal force is G * M1 * M2 * L / r^3, that is it depends upon both masses, the distance between them, and the distance from the center of gravity of the object you are measuring. In the plane perpendicular to the vector between the two masses, the force in toward the center of the mass, along the vector the force is either toward or away from the other mass. We assume for the purposes of this disussion that M2 and L are both one, since we want unit quantities for the Tidal forces.

The reason to use Tidal force is because it is a measure of the rate of change caused by gravity. That is, how much is the local planet or star warping space in the vicinity of the starship.