Jeff Zeitlin asks about mass in starship designs. Others have adequately
covered the "real world" aspect of needing to ensure that the thrust is
through the center of mass, so I won't go over that again. As to the question
of how thrusters work--I've always assumed that they _really_ work on
F=ma, and that the drive ratings are simple approximations of what per-
formance would be expected with a typical weight on a given hull size.
However, given that the TL9 antigrav drive unit is the same size and has
the same power input as 650 tons of thrust worth of grav units from the
vehicle part of the deisgn sequence, I always calculate a "true acceleration"
based on 650 tons/drive unit. I've found that with ships carrying little
or no extra armor, the resulting number is usually within 20% of the "drive
rating" number. For thrusters I continue to assume 650 tons per unit, with
the extra power required going to account for whatever magic makes them
work in deep space.
In practice, I've never really bothered to recalculate accelerations with
varying cargoes during a game, but it wouldn't be prohibitively difficult,
as long as you peg the thrust of a drive unit at some set value. I have
recalculated acceleration for a ship with a disabled power plant that had
to jury rig some power for the thrusters using a portable fusion plant from
the cargo during a game, but I seem to recall that I just used the default
"loaded weight" for the calculation.
Rob Dean
[email removed]