Saying that an object is shielded by gravity (whether by a physical barrier, energetic barrier, or by emission of anti-gravitons, or whatever) is not synonymous with saying that it has zero mass.
It might have its mass removed from interaction with gravity by some field or barrier, but that doesn't meant that its mass no longer calculates into inertia and kinetic energy equations.
It might be defying gravity by emission of antigravitons which cancel the gravitons being emitted by nearby objects. This says nothing about its effective mass for things like kinetic energy and inertia.
Let me give one example of a real world attempt at antigravity: Mach's principle. There's a guy (Woodward?) who is trying to use Mach's principle to create reactionless thrust. It works by using an electric field to manipulate the mass of a system so that its effective mass is a negative value, and then oscilating two such devices which are themselves varying between positive and negative masses. You end up with a pulsating device that produces a net thrust in one direction, but without ejecting reaction mass (at least, not conventional reaction mass ... at a quantum mechanical level you might _have_ to consider it ejecting (anti-)gravitons or something). There's no indication in his experiments that the device's negative mass (or even artificially reduced mass) has less inertia or kinetic energy than the base device ... in terms of those things, (from what I've been reading) its mass is what you'd expect. It's only in terms of how the device interacts with gravity that its effective mass is changing.
Further, even if the device, when canistered into an engine, ends up having less inertia when operating than it did while turned off, there's still the inertia of the entire rest of the vehicle (the "tank" part). The entire vehicle doesn't have a net zero mass. Instead, the engine is generating an upward force which balances against the downward force of gravity. The rest of the vehicle is still a positive mass with normal inertia and kinetic energy.
Unless the Traveller setting specifies which is the actual technique, you can't conclude that a grav-tank automatically has zero-mass (or incredibly small mass) for inertia and energy (and therefore for colissions) considerations.
(note: I'm not claiming woodward's work will pan out, I'm more pointing out that just because something is overcoming gravity doesn't mean it reduces its inertia and kinetic energy, nor does it mean anything in terms of the rest of the vehicle's inertia even if the engine's mass is doing wonky things)
It might have its mass removed from interaction with gravity by some field or barrier, but that doesn't meant that its mass no longer calculates into inertia and kinetic energy equations.
It might be defying gravity by emission of antigravitons which cancel the gravitons being emitted by nearby objects. This says nothing about its effective mass for things like kinetic energy and inertia.
Let me give one example of a real world attempt at antigravity: Mach's principle. There's a guy (Woodward?) who is trying to use Mach's principle to create reactionless thrust. It works by using an electric field to manipulate the mass of a system so that its effective mass is a negative value, and then oscilating two such devices which are themselves varying between positive and negative masses. You end up with a pulsating device that produces a net thrust in one direction, but without ejecting reaction mass (at least, not conventional reaction mass ... at a quantum mechanical level you might _have_ to consider it ejecting (anti-)gravitons or something). There's no indication in his experiments that the device's negative mass (or even artificially reduced mass) has less inertia or kinetic energy than the base device ... in terms of those things, (from what I've been reading) its mass is what you'd expect. It's only in terms of how the device interacts with gravity that its effective mass is changing.
Further, even if the device, when canistered into an engine, ends up having less inertia when operating than it did while turned off, there's still the inertia of the entire rest of the vehicle (the "tank" part). The entire vehicle doesn't have a net zero mass. Instead, the engine is generating an upward force which balances against the downward force of gravity. The rest of the vehicle is still a positive mass with normal inertia and kinetic energy.
Unless the Traveller setting specifies which is the actual technique, you can't conclude that a grav-tank automatically has zero-mass (or incredibly small mass) for inertia and energy (and therefore for colissions) considerations.
(note: I'm not claiming woodward's work will pan out, I'm more pointing out that just because something is overcoming gravity doesn't mean it reduces its inertia and kinetic energy, nor does it mean anything in terms of the rest of the vehicle's inertia even if the engine's mass is doing wonky things)
