Project Mercury was the first manned spaceflight program of the then new US Space Agency NASA. The astronauts were called "Mercury 7". After Alan Shepard's (MR-3) and Gus Grissoms (MR-4) suborbital ballistic spaceflights, astronaut John Glenn became the first US citizen to orbit the earth (MA-6 in 1962). After six manned successful flights, the Mercury Program ended in 1963.
