Interesting take on it...
MadScientistMatt said:
If they worked by a backwards gravitational effect, they would affect things in proportion to their mass. So most of the force below them would be applied to the planet, and very little of it would actually affect soldiers below them.
Seems reasonable.
This "backwards gravitational effect" would be dependent on the gravity well it's operating in (in this case, the planet below).
The consequence: the power of the lift would drop dramatically as the force of gravity faded. Depending on sensitivity, such a craft would be virtually paralyzed outside a strong gravity well – in essence, making the gravitics float with dynamics akin to a balloon.
Could be fun to play with the idea, though it limits the SF to either LEO or really slow interplanetary travel (Earth to Mars Express, or similar). It might be fun writing about such a craft trying to break out of a planetary gravity well and the turbulence they endure as they transition to the stellar gravity well.
Might even be able to use it for really, really,
really slow interstellar travel. Another fun plot point: aiming for the target system and having to aim straight for the star to decelerate (or some variation thereof). I could see potential for some high drama.
MadScientistMatt said:
The biggest problem with that is that we have no evidence that such a negative gravity effect is possible.
True – but that caveat covers half of gravitic technology (a third if we consider "nullification" it's own flavor). In a way, now that I think about it, the craft you describe modifying it's mass in proportion to the gravity well might actually lean toward "nullification" (though we're so deep in speculation right now that you could argue just about anything).
As for evidence of a "negative gravity effect":
good news for SF writers. You could consider "dark matter/dark energy" (in the cosmological sense) as a possible hook. Dark Energy demonstrates a type of "negative pressure" – a repulsive force against gravity's attractive force. More than an enough ammunition for SF writers to co-opt it for their own.
MadScientistMatt said:
Laurence Kraus had an interesting take on some of the trouble with large hovering objects. He noted that if the flying saucers in Independance Day stayed up by any sort of rocket power, jet engines, or other pressure-based propulsion, they would have crushed Washington, DC simply by flying over it without even bothering to fire their weapons.
Potentially, yes – and that
could apply to any type of propulsive gravitics as well,
especially those that rely on suspending a craft a surface-based column of downward force. IIRC, the Martian invaders in "War of the Worlds" used that principle (the 1953 movie version, not original Wells story).
On the bright side, we really don't have a clue to how gravitic propulsion would actually work. When people think "
thrust", they usually apply known rocket rules. With gravitics, though, it's a whole new paradigm: you're looking at field effect,
possibly closer to how magnets generate magnetic fields. Imagine a gravitic "thruster" where equivalent mass flow rate was huge but velocity negligible. The decay of the field might be measured in feet... and on a dark night, those below would never know what was floating above.
if they can name what bit of modern mythology claims to see these effects already.
I think you've about nailed it!
