astroengine writes "The idea of slingshotting a manned spacecraft around Mars isn't a new one. In the 1960's, NASA carried out a feasibility study into an 800-day flyby mission to the Red Planet. And it would have been awesome. AT&T/Bellcomm mathematician A. A. VanderVeen was working for NASA in 1967 and came up with 5 possible launch opportunities between 1978 and 1986 — two windows in 1979 and 1983 provided the shortest transit time between the planets. But launch mass and fuel requirements were a constant issue. So VanderVeen turned to physics to find an elegant, and scientifically exciting, solution: add a Venus flyby to the Mars trip. Mars, Earth, and Venus align with the sun five times every 32 years, but Venus and Mars alignments happen more frequently making double (Earth-Venus-Mars-Earth) or even triple (Earth-Venus-Mars-Venus-Earth) flybys a viable mission. Unfortunately, the flyby never happened."