...Hey, I like Grav! I liked watching Luke Skywalker "drive"
his landspeeder around in Star Wars; I liked all the flitting around in
contra-gravity ships in H.Beam Piper's books (not to mention in Perry
Rhodan...); I accepted as part of the background the "grav sleds"
(probable ancestor of the air/raft) in Andre Norton's books (I note that
her ships land with rockets firing, though.) The inconsistencies in MT
between vehicle use of gravitics and spaceship use of them bothered me,
so I came up with *my* (not warranted to work in your campaign)
explanation of why they worked the way they did. I suspect the
physicists out there could pick holes in it, but -- it beats the "eighth
ray of propulsion" explanation! (10 pts to whoever remembers where that
comes from!)
How Gravitics & Thrusters Really Work
Both spaceship drives and vehicle propulsion modules work on the
same principle -- that of a gravity warp. This is an artificially
generated gravitional field that can be used for propulsion by "gravity
planing" -- that is, changing the vector of the artificially generated
field to "play off" the local natural gravity field to obtain the
"thrust" vector desired.
Spaceship Drives - the warp encloses the entire volume of the
ship; this has the advantage that the ship's mass does not affect the
size and power requirements for the maneuver drive. It has the
disadvantage that a very strong, shielded hull is required because of
the stresses created at the boundary of the warp; for safety reasons,
the boundary of the warp must be within the thickness of the hull. A
badly adjusted warp field, whose boundary is at or near the surface of
the hull can result in some spectacular electromagnetic effects.
(Classic UFO effects on nearby electronics).
Vehicle Propulsion Modules - The warp encloses a small slug of
high-strength material inside the module, that is anchored to the
module. Whatever thrust vector the "slug" has, pulls the vehicle along
with it. Advantages: Vehicle does not require a reinforced hull; and
standard propulsion module designs have sufficient safety margins that a
badly tuned warp field will not manifest outside the module.
Disadvantages: Since the warp only encloses the slug, performance is
dependent on the vehicle's mass.
-- Cynthia