Re: Ahead, Warp Factor...
Someone on Slashdot, who apparently read the article more closely than I did, said that the 57% c figure is the velocity where the 'forward' gravity reaches zero. By the time the antigravitational bow shock pushes the payload to 57%c in the launch vehicle's inertial reference frame, thrust has reached zero. So your launch vehicle will have to not only be massive enough to generate a powerful gravity field, but be moving quickly enough to still be going 57%c relative to the payload when the payload reaches interstellar velocity. Additionally, the payload will have to be very agile to dodge something closing at more than 57%c that's big enough and close enough to be generating strong gravity. Velocity based DCV perhaps?