The Mercury-Redstone Launch Vehicle, designed for NASA's Project Mercury, was the first American manned space booster. It was used for six sub-orbital Mercury (Spacecraft) flights from 1960–61; culminating with the launch of the first, and 11 weeks later, the second American (and the second and third humans) in space.
A member of the Redstone rocket family, it was derived from the U.S. Army's Redstone ballistic missile and the first stage of the related Jupiter-C launch vehicle; but to make it man-rated, its structure and systems were modified to improve safety and reliability.
The four subsequent Mercury manned flights used the more powerful Atlas booster to enter low Earth orbit.