Manned expedition to Mars in 2004

"The primary objective of the 1989 Mars Expedition case study was to determine how to accomplish a single human expedition to the surface of Mars as early in the 21st century as practical. The preferred option was now an "all-up" approach in which the crew and all the cargo were dispatched on one vehicle. The 1989 Mars expedition case study ground rules included: a single expendable vehicle would be launched to low Earth orbit; a zero-gravity vehicle would be used; three crew members would descend to the surface for 20 days; and aerobraking would be used at Mars."