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In situ return journey propellant production has been a key element of Robert Zubrin's "Mars Direct" proposal: http://en.wikipedia.org/wiki/Mars_Direct http://e
by alex_stoddard 13y ago
In situ return journey propellant production has been a key element of Robert Zubrin's "Mars Direct" proposal: http://en.wikipedia.org/wiki/Mars_Direct http://en.wikipedia.org/wiki/Mars_Direct