High risk low cost Mars missions scenarios

Manned mars missions have been the subject of considerable study during the last ten years. Most of the early SEI (Space Exploration Initiative) studies have concentrated on minimizing the IMLEO (Initial Mass in Low Earth Orbit), but most studies generally considered missions where the entire spacecraft would go into orbit about Mars before the landing. Other scenarios utilized a direct landing on Mars, with in-situ propellant production, and a dash to Mars by the crew coupled with a hyperbolic rendezvous, at Mars, with the slower transit vehicle. Both proposals present more risk but promise a significant reduction in IMLEO, and a subsequent reduction in cost. An intermediate set of missions that combines a free return trajectory and a dash to Mars, but nearly the same IMLEO is proposed. The various mission scenarios are compared on a risk vs. cost basis.