Editing Mars Direct (section)

===Mars Semi-Direct===

[[File:Mars design reference mission 3.jpg|thumb|350px|Artist's rendering of Mars Semi-Direct/DRA 1.0: The Manned Habitat Unit is "docked" alongside a pre placed habitat that was sent ahead of the Earth Return Vehicle.]]

Zubrin and Weaver developed a modified version of Mars Direct, called Mars Semi-Direct, in response to some specific criticisms.<ref>{{cite conference | first1 = Robert M. | last1 = Zubrin | first2 = David B. | last2 = Weaver | title = Practical methods for near-term piloted Mars missions | citeseerx = 10.1.1.23.1915 | conference = AIAA93-2089,29th AIAA/ASME Joint Propulsion Conference | location = Monterey CA, United States | date = June 28–30, 1993 | doi = 10.2514/6.1993-2089 }}</ref> This mission consists of three spacecraft and includes a "Mars Ascent Vehicle" (MAV). The ERV remains in Mars orbit for the return journey, while the uncrewed MAV lands and manufactures propellants for the ascent back up to Mars orbit. The Mars Semi-Direct architecture has been used as the basis of a number of studies, including the NASA Design Reference Missions.

When subjected to the same cost-analysis as the [[NASA 90 Day Study|90-day report]], Mars Semi-Direct was predicted to cost 55 billion dollars over 10 years, capable of fitting into the existing NASA budget.

Mars Semi-Direct became the basis of the [[Design Reference Mission]] 1.0 of NASA, replacing the [[Space Exploration Initiative]].