In 1991, a team at
Martin Marietta led by Robert Zubrin, in conjunction with NASA Ames, proposed a
revolution in Mars exploration thinking. Mars Direct envisioned a series of
space craft to be launched on a super heavy lift launch vehicle, dubbed the
Ares. The first launch would deliver an unmanned Earth Return Vehicle
(ERV) to the Martian surface. After landing an on-board production plant would
generate methane/oxygen propellants for the ERV’s return trip to Earth. The
second launch would deliver a four person crew for eighteen months of Mars
exploration. Then the crew would use the ERV to return to Earth. Because the
expedition would not have to carry all of the fuel needed to Mars, the weight,
size, and cost of the Mars ships would be greatly reduced. Zubrin has estimated
that Mars Direct, rather than costing the hundreds of billions of other Mars
expedition concepts, would cost just twenty billion dollars.
Vision for Space
Exploration
In the wake of the Columbia shuttle disaster, President George W. Bush
has proposed a Vision for Space Exploration, which would eventually include
human expeditions to Mars. How these expeditions would happen is still a work
in progress. Very likely the space craft would be powered by a nuclear thermal
rocket engine such as the NERVA. Also, Zubrin’s concept of manufacturing rocket
fuel on Mars would be used as a cost saving measure.