Atlas LV-3B

The Atlas LV-3B, also called the Atlas D Mercury Launch Vehicle or Mercury-Atlas Launch Vehicle, was the human-rated expendable launch system that carried the United States Project Mercury spacecraft into low Earth orbit. Convair manufactured it from the SM-65D Atlas missile, which was the only vehicle in the American arsenal able to put the capsule into orbit and had many test flights to learn from. Because Atlas began as a weapon whose launches often ended in explosions, engineers added an abort sensing and implementation system, extra engine sensors, tighter quality control and a separate assembly line to make it safe enough for astronauts. It first flew on 29 July 1960 with the unsuccessful Mercury-Atlas 1 test, and the United States launched it nine times, four of them with crewed Mercury spacecraft. The last launch was Mercury-Atlas 9 on 15 May 1963.