Re: B5 Ship Combat was Re: Cinematic vs. Vector movement

On Sat, Aug 30, 2003 at 11:29:54PM -0400, Laserlight wrote:

>Or 7.5 minutes.  And I think Derek suggested 100 seconds or something
>similar, which worked well.

OK. Here's my standard explanation, which I don't think I've posted here
before:

FT acceleration (in cinematic or in vector) is not realistic. When you
apply 1 thrust point, you get a speed of 1 MU/turn, which is fine - but
during the turn you apply it, you move 1 MU, which isn't. That would
only make sense if you applied all the thrust instantaneously at the
start of the turn, whereas what we generally assume is that the thrust
is applied over the entire course of the turn - what that should mean is
that you move 1/2 MU per thrust point on the turn you accelerate, and 1
MU per thrust point on each subsequence turn.

This problem is common to all space combat games I've played. Some of 
us have been playing with rules to make this work in a realistic 
manner. It's possible, but needs a lot more bookkeeping, especially in 
vector.

Anyway, that's a side issue, but explains why I'm using the working I am
here. Some variables:

g = the acceleration equivalent to "thrust 1" (in m/s/s)
T = the length of a turn in seconds
M = the length of an MU in metres
V = the speed of 1 MU per turn (in m/s)

OK. So, the speed you get by accelerating by thrust 1 for 1 turn is V:

g x T = V

but that's also a speed of "1 MU per turn":

M / T = V

so M / T = g x T

(I.e. "the speed you end up going at is equal to the acceleration
multiplied by the time for which the acceleration is applied".)

rearranging, M / g = T^2.

I'm going to assume hereafter that g is one terran gravity (9.81 m/s/s),
since that makes sense from the point of view of acceleration
compensators.

This gives a family of scales:

M	 T
1,000km  319.3s
2,000km  451.5s
4,000km  638.6s

or if you want to nail the T values:

M	   T
  882.9km  300s
3,531.6km  600s
7,946.1km  900s

or if you don't care about the precise value of acceleration but want
round numbers, set g = 11.11 m/s/s:

M	 T
1,000km  300s
4,000km  600s
9,000km  900s

Any of these scales will work. The only thing they'll affect is the size
of planets placed on the table (Earth has a 6,300km radius) and the
placement and speed of orbits (a geosynchronous orbit is about 42,000km
from the centre of Earth and involves movement at about 3,065 m/s).

Hope this helps...

Roger