Question One, How do they work?
I would suggest that Gravitics (broadly speaking) is actually some type of "pseudo-gravity" and not a manipulation of actual gravity, for the reasons that Mike Wightman notes above.
This could possibly be:
- Some heretofore undiscovered force or spin-off effect of an existing force or forces (perhaps related to the underlying principles of a Unified Field Theory or hyper/jumpspace physics in some way) that acts upon mass; or
- Some heretofore undiscovered force or spin-off effect of an existing force or forces (perhaps related to the underlying principles of a Unified Field Theory or hyper/jumpspace physics in some way) that acts upon or reacts to other fields or particles that virtually all matter internally possesses (such as the Strong Force / Gluon Fields, etc).
- An entirely new force acting upon something as yet undetermined that most masses seem to possess (again, perhaps related to the underlying principles of a Unified Field Theory or hyper/jumpspace physics in some way).
As noted below, there are both "
Lifters" which are not a significant thrust-agency (but may provide a limited amount of lateral motion in addition to "rise-and-hover"), and then there are various "
Drives" which are actually action-reaction propulsion systems.
Question Two, How many flavors of grav vehicles are there?
I would also suggest that there is potentially a difference between the following (although they may simply be different applications of the same physics/engineering principles):
- L-Drive (Lifter) (Contragrav/Null-grav) : Simply nullifies gravity, but does not otherwise produce thrust, or merely produces a minimal directional bias/motion along a gradient. Normally an additional thrust agency is required for any significant lateral motion or velocity. In T5, they are limited in use to 1.0 D from a massive body.
- G-Drive : An actual Grav-Thruster which reacts against mass/gravity (action-reaction) to produce thrust (note that it might be effectively non-functional when null-grav/contragrav is in concurrent use - or they may tunably act together in unison (one scaling up as the other scales down). In T5, they are limited in use to 10.0 D from a massive body, beyond which they drop to 0.01 efficiency.
- M-Drive : A more advanced type of G-Drive that (based on prior rulesets) may incorporate other operating principles as well (see MT / T-Drive Thruster below). Again, note that it might be effectively non-functional when null-grav/contragrav is in concurrent use - or they may tunably act together in unison (one scaling up as the other scales down). In T5, they are limited in use to 1000.0 D from a massive body, beyond which they drop to 0.01 efficiency (although many choose to modify or ignore this stipulation).
- N-Drive (NAFAL) : A highly focused M-drive that gains significant operational radial performance range at the sacrifice of lateral performance. In T5, they are limited in use to ~1/8 lightyear from a massive body along a direct radial trajectory, beyond which they drop to 0.01 efficiency.
Also, some might choose to mention here the "
Thruster" (
T-Drive), which in T5 seems to be described like a Dean-drive (mechanical/non-gravitic), but in MT, TNE-FF&S, and T4 was another name for the
M-Drive. The T4-Thruster had the 1000.0 D stipulation as in T5 above, but the MT-Thruster did not, and was described as a spin-off of both pseudo-gravity and the Strong Nuclear Force and was truly "Reactionless" with no maximum range specified (at least under normal usage conditions).