[furball4paws]

Here's an update from my physicist friend after he searched a bit more:

"OK, here is what he has done. Picture a small mass ("payload") floating at rest in space. Heading toward the small mass is a *rotating* BLACK HOLE. It is known (the "Kerr effect") that such a mass will cause the test particle to rotate about the hole ("frame dragging"). What this guy has discovered is that if the hole is moving toward the payload fast enought (1/sqrt(3) C) then the payload can be "pushed" to speeds near that of light. This is NOT anti-gravity, but is the same effect that our own space capsules get when whipping about Jupiter; they gain energy during the "collision" with Jupiters gravitational field: Jupiter is slowed somewhat, and the capsule is accelerated somewhat. That will happen here too: the black hole loses some energy, the payload gains some, but since the payload is so small it moves quickly, ie. a collision has occurred with the hole.

So, want to acclerate something near light speed, get yourself a rotating black hole with 10^5 solar masses ..."

[PatrickHenry]

Makes sense. Thanks to your friend, and thanks to you for posting his views.

[Physicist]

(the "Kerr effect")

Lense-Thirring effect, I believe, but that's just me being captious. As for the rest, I must defer to anyone who's actually read up on this paper.

[NicknamedBob]

"...since the payload is so small it moves quickly, ie. a collision has occurred with the hole."

So what we're seeing, from our frame-reference, is the payload squished on the windshield of the event horizon? Not the sort of Anti-Gravity propulsion I had in mind for space travel, thank you!

Ingrediants for high-speed land travel:
1) Bungee cord
2) Speeding locomotive
3) Insane good luck

Hmm. I don't think so ...

[spunkets]

" "Kerr effect"

That's an electromagnetic effect in birefringent materials. In this case Kerr is the name of a guy that provided a solution to some eq. Frame dragging was mentioned in that paper, but it's much smaller than the slingshot effect Felber considered. NASA uses it for space probes. The idea is that you fly past a planet in a high speed glance. The speed is too great to enter an orbit and the gravitational field whips the probe around like David's slingshot and sends it flying off with a significant amount of E. During the slingshot fling, towards the end, the probe moves away from the massive body(planet). Felber calls that "repulsion". As your post noted, it isn't repulsion.