Using lunar swingbys and libration-point orbits to extend human exploration to Mars

This paper will concentrate on one mission profile of particular interest, a manned mission to Mars. Specifically, the study will explore the use of HEOs whose line of apsides can be rotated using lunar swingbys to approximate the V_∞ vector necessary for such a mission, reducing the required energy cost of such a mission. The HEO also provides a convenient and relatively fast location for rendezvous with crew, or to add propulsion or cargo modules, a technique that we call "Phasing Orbit Rendezvous." From a HEO, a propulsive maneuver, considerably smaller than that needed from a circular low-Earth orbit, can be applied at the right perigee to send the spacecraft on the appropriate departure asymptote. A propulsive maneuver at perigee can be used to re-capture the spacecraft into a loosely-bound orbit at the return, perhaps assisted by a lunar swingby. Earth-Moon (and possibly Sun-Earth) libration point orbits and double-lunar swingby orbits will be used, along with time to change the orbital orientation between missions. There might be wait times of several months to years between missions, when the interplanetary spacecraft could be "parked" in a small-amplitude Lissajous orbit about a libration point, similar to that flown by the WMAP mission.