Human Missions to Mars, Enabling Technologies for Exploring the Red Planet, Rapp D., 2008.
Human missions to Mars represent the pinnacle of solar system exploration for the next half-century. In addition to providing a means of exploring Mars, such missions would represent an inspiring engineering achievement and create a new era of expansion of humanity into space. Because such missions would require a major technological effort as well as very large expenditures, they remain for the moment as futuristic concepts embodied in paper studies by visionaries, advocates, and enthusiasts.