Hmm... there seems to be a misunderstanding here about what a gravity wave
actually is...
But before I attempt to muddy the waters, I should point out that I am a
mathematician who has seen some of the _mathematics_ of general relativity,
have a more than passing interest in the subject, but I am by no means a
physicist and I will defer to anyone with better knowledge than mine. Also
I am posting without using any references, which is doubly dangerous. 8-)
A gravity wave is a ripple in spacetime caused by the movement of mass. A good
analogy to think of here is of a block of wood floating in a pond, the
block of wood is your mass (such as a star), the pond is spacetime. If you
bump the wood, you generate a ripple in the water which, as it propagates,
can cause other blocks of wood to move. The ripple in the water is roughly
(very roughly in fact 8) ), analogous to a gravity wave.
Gravity waves have nothing to do with black holes per se (although black
holes can generate them if they're accelerating), and the reason that light
can't escape from black holes is due to the nasty things which happen at
the event horizon, not gravity waves pulling the light in. To extend the
above analogy, if you imagine the black hole as a drain hole with water
draining out (in the traditional funnel shape), then the water can be very
smooth (ie. no gravity waves), but can still pull objects into it, even if
they are moving away from the drain (ie. light can't escape). This is an
even worse analogy than above, but it does get across the difference: the
light can't escape because of the shape of the spacetime.
The problem with finding gravity waves (and particles, which are the same
thing) is that they are extremely weak in virtually all cases, and hence
are hard to detect. So hard that no one has done it. But I think most
physicists consider them to exist. As to there speed of propagation, all I
can say is that that's what you get out of the equations (and I can't
recall if I have seen such a derivation), but on a heuristic sense, it
makes sense that they move at the speed of light, since gravitons (gravity
particles) are zero rest mass particles (like light), so they should move
at the same speed.
In addition if gravity waves were to travel faster than the speed of light,
you would have a means for FTL communication (it would work along the lines
of: two people have two large masses. One person wobbles their mass, and
the other watches the way their mass wobbles once the gravity waves from
the first reach it). Instantaneous propagation of gravity waves would allow
instantaneous communication, which contradicts the "no communication faster
than speed of travel" background of Traveller for a start ( 8) ), and if it
were possible in the real world, I think there would be a lot of research
into trying to make it practical...
Enough of that. What about black globes? No, you couldn't make a perpetual
motion machine out of one, at least not by the method suggested, because a
planet doesn't radiate gravity waves as seems to be being assumed. I would
think that what would happen in the situation described would be that the
black globe would fall towards the surface of the planet exactly as would
the ship it contains. If a black globe hit a gravity wave, I would expect
that it would behave exactly as would its contents (ie. it would follow the
same trajectory), but it would buffer its contents against the effects of
the acceleration caused by the wave, absorbing the energy of the wave into
the energy sinks.
This would allow some neat things to be done by ships using black globes,
though. For instance, I would expect that a ship protected by a black globe
could go (briefly) into areas with strong tidal forces (such as around
neutron stars) where they would normally be torn apart. Also, they could
undergo accelerations while within a black globe that would normally leave
the crewmembers splattered across the floorpanels. These two ideas would
allow some pretty neat gravitational slingshot manoeuvres. Not that they
really are needed when you have 6G thrusters and inertial compensators, but
I'm sure that a good ref could tie in those uses of black globes.
I hope this has cleared some things up. For more information, check either
a good popular science book (sections of "A Brief History of Time" by
Hawking or "The Emperor's New Mind" by Penrose spring to mind as possible
sources), or try the rec.arts.sf.science or sci.physics newsgroups.
See ya 'round.
Corran
PS. About 2300AD: On of the rumours about Traveller: Then New Era is that GDW
will produce a 2300AD sourcebook which will allow the new Traveller rules to
be used in the 2300AD universe. This would be a Good Thing IMHO, since I
really liked the 2300 universe (and as you can probably tell by the above
waffle, I like my sf fairly hard).