Re: [ft] Orbits in Vector

On Sat, 29 Jul 2000 21:43:18 -0700, Sean Bayan Schoonmaker
<s_schoon@pacbell.net> wrote:

>Here's what I use:
>
>I place the planet on the table. Under that I have 2 cloth circles. One
is
>12" dia. and the other is 24" dia.
>
>Any ship ending its movement on the outer circle gets 1" added to the
>vector in the direction of the ship-to-planet. The inner circle does
the
>same thing, but for 2"

That's a nice, simple way to do it. But, I decided, for the heck of it,
to do
some calculations. 

I took the "unofficial" scale for FT (1 Movement Unit or MU = 1,000 km,
1 turn
= 15 minutes) and used 1 gravity (g) = 10 metres per second per second.
The
result was a calculation of 8.1 Movement Units towards a planet at it's
surface. 

Now, the surface of the earth is roughly, in this scale, 6" in diameter.
Gravity is an inverse square law. 3" out from the surface, the vector
would be
2 MUs towards the planet. 6" from the surface, it's approximately 1 MU.
This
is the same as what Sean came up with.

I just did some additional calculations. If you wanted to be more
accurate, an
Earth style planet on an FT table would be 6" in diameter. You would
then have
concentric circles out from that. The circles would be 7", 8", 9" 10",
and 12"
in diameter, and would have a vector towards the centre of 6, 5, 4, 3,
and 2
MUs respectively. Another circle, 18" in diameter, would have a vector
of 1 MU
(actually, if you're rounding off vectors to the nearest half, the
second last
circle really should be 14" in diameter, and the last circle should be
24" in
diameter). This assumes, of course, you want to keep MUs to whole
numbers.

Gravity wells for larger planets aren't really practical at this scale,
unless
you use a table edge (although doing some reading, I found that while
Uranus
would have a diameter of 26" on the table, it actually has slightly LESS
surface gravity than Earth, so you could actually have a half a gas
giant on
your table top, as long as it isn't Jupiter...).  

Allan Goodall		       awg@sympatico.ca
Goodall's Grotto:  http://www.vex.net/~agoodall

"Surprisingly, when you throw two naked women with sex
toys into a living room full of drunken men, things 
always go bad." - Kyle Baker, "You Are Here"