Yep… the early US manned space program used military missiles to launch the manned capsules.

Two types of rockets were used for Project Mercury. The first two of the six flights with an astronaut on board used a Redstone rocket. The four manned flights that orbited Earth used an Atlas rocket. Both of these rockets were originally designed as missiles for the United States military.

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 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 man-rate it, the structure and systems were modified to improve safety and reliability.

The PGM-11 Redstone was the first large American ballistic missile. A short-range surface-to-surface rocket, it was in active service with the U.S. Army in West Germany from June 1958 to June 1964 as part of NATO’s Cold War defense of Western Europe. It was the first missile to carry a live nuclear warhead, first detonated in a 1958 Pacific Ocean weapons test, with two tests occurring over a period of 12 days.

A direct descendant of the German V-2 rocket, the missile was the foundation for the Redstone rocket family, It was developed by a team of predominantly German rocket engineers relocated to the United States after World War II as part of Operation Paperclip. Redstone’s prime contractor was the Chrysler Corporation.[1]

For its role as a field artillery theater ballistic missile, Redstone earned the moniker “the Army’s Workhorse”. It was retired by the U.S. in 1964, though in 1967 a surplus Redstone helped launch Australia’s first satellite.

The Atlas LV-3B, Atlas D Mercury Launch Vehicle or Mercury-Atlas Launch Vehicle, was a man-rated expendable launch system used as part of the United States Project Mercury to send astronauts into low Earth orbit. It was derived from the SM-65D Atlas missile, and was a member of the Atlas family of rockets.

Nine LV-3Bs were launched, two on unmanned suborbital test flights, three on unmanned orbital test flights, and four with manned Mercury spacecraft.

The SM-65 Atlas was the first intercontinental ballistic missile (ICBM) developed and deployed by the United States. It was built for the U.S. Air Force by Convair Division of General Dynamics at the Kearny Mesa assembly plant north of San Diego, California. Atlas became operational as an ICBM in October 1959 and was used as a first stage for satellite launch vehicles for half a century. The Atlas missile’s warhead was over 100 times more powerful than the bomb dropped over Nagasaki in 1945.

Even before its military use ended in 1965, Atlas had placed four Project Mercury astronauts in orbit and was becoming the foundation for a family of successful space launch vehicles, most notably Atlas Agena and Atlas Centaur.

Today Lockheed Martin and ULA support a new Atlas rocket family based on the larger “Atlas V” which still uses the unique and highly efficient Centaur upper stage. Atlas V stage one is powered by a Russian RD-180 oxygen/kerosene engine and uses conventional aluminum isogrid tankage rather than the thin-wall, pressure-stabilized stainless steel tanks of the original Convair Atlas. Payload weights have increased along with launch vehicle weights over the years so the current Atlas V family serves many of the same type commercial, DoD, and planetary missions as earlier Atlas Centaurs.