The National Aeronautics and Space Administration (nasa) has been interested in returning to the moon and establishing permanent bases there since the 1980s, and one of its Web sites reports that in March 2009 the Lunar Reconnaissance Orbiter will be dispatched to scout out the best possible landing sites tor manned spacecraft, which nasa hopes to launch in 2020. But NASA hopes not just to land on the moon but also to establish longer-term bases tor astronauts, and to accomplish this the astronauts will need to be able to build structures using resources that are readily available on the lunar surface. The structures will need to be able to withstand the harsh lunar environment, and for this reason concrete appears to be a suitable building material. Traditional concrete comprises a binder-cement and water-mixed with aggregates, but water will presumably be unavailable on the moon. To address the deficiency, astronauts could turn to a new type of waterless concrete that uses lunar regolith as the aggregate and sulfur as a binder.
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