@magiimice
I think the term "gravity wave" is a misnomer it should actually be called as the centrifugal force instead.
and i suppose what you meant was "the gravity of the star(centrifugal force on your ship) would be so high, and non-damaging for your ship that it will propel it through space..:)

well the idea is good,
i faintly remember that the Voyager satellite, did actually use that principle to propel itself by using the gravity of jupiter..:) so its practically possible if the calculations go correct:)