"American manned Mars expedition. Study 1960. The first NASA study of a manned Mars expedition outlined an opposition-class, nuclear thermal rocket powered spacecraft that would take seven astronauts to the planet's surface for 40 days."
In 2000s a Mars One project was established. It claims to take humanity to Mars in 2023, to establish the foundation of a permanent settlement from which we will prosper, learn, and grow. Before the first crew lands, Mars One will have established a habitable, sustainable settlement designed to receive astronauts every two years. To accomplish this, Mars One has developed a precise, realistic plan based entirely upon existing technologies. It is both economically and logistically feasible, in motion through the integration of existing suppliers and experts in space exploration.