Rappolee interstellar low energy transfer trajectories
My Hypothesis is that a world ship needs less energy to slow at its destination if the voyage is made as the target star is making a close approach and is veering away from the home star system.
To the world ship it would appear as if we were coming up from behind the stars line of flight and we come up alongside the target star.
*** By FrancescoA (File:Near-stars-past-future-de.svg) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)%5D, via Wikimedia Commons
Indeed the Rappolee transfer trajectory could have implications for panspermia in that meteorites with a higher incoming speed would be more likely to destroy life a to an interstellar meteorites incoming at slower speeds from a star moving away from us after lose encounter
EDIT 26 December 2014
A new paper on ballistic Mars capture orbit,fly a ballistic orbit to a future point in space where Mars will be, would apply to my idea for future lose approaches by stars?
EDIT 4 Jan 2015
additional paper found on Centauri Dreams