Mark,
I wrote a paper about this that I published throught the "Journal of the British Interplanetary Society". I now consider that original paper to be flawed but still believe in its basic premise. That premise was to colonize Mars over a twenty year period using a single cycler spacecraft travelling on an Aldrin "up" escalator orbit. The cycler spacecraft would be a stretched version of the ISS. It would achieve orbit using nuclear electric propulsion (VASIMIR drive). Colonist entry to Mars would be direct from heliocentric orbit using aerocapture with biconic entry vehiclea trimmed for high lift entry. The original biconic aeroshell would then be jettisoned with the colonists making their final entry in 70 degree sphere-cone aeroshells (this approach keeps decelleration loading under 5 gravities).
Significant cost reduction can be achieved by using a single cycler vehicle that was slowly built up by every wave of colonists (they'd come every two years with each wave size growing geometricly). The colonists would go one way to Mars with no option of return. Elimination of the return option offers huge reductions to program costs making it comparable in cost to establishment of a conventional Mars base of say 20 people with return option.
Gary
Space/Science » in reply to Sounds Too Cheap & Too low
Cycler orbit colonization