On February 20, 1962, John Glenn sat inside of his Freedom 7 capsule waiting for the countdown to reach zero as the Atlas rocket below him creaked and groaned. The booster's stainless steel walls were so thin that the rocket would have collapsed if its balloon fuel tanks hadn't been pressurized with nitrogen gas. This was the first manned launch for the Atlas rocket, which had a nasty habit of exploding during test flights.
Glenn had nothing to fear on this day. The Atlas rocket performed perfectly, making Glenn the first American to orbit Earth. Three other Mercury astronauts would ride the converted intercontinental ballistic missile (ICBM) into space after him.
General Dynamics' Convair Division developed the original Atlas rocket in the late 1950s. The first successful test flight took place on December 17, 1957. A year later, an Atlas rocket launched the Signal Communication by Orbiting Relay Equipment (SCORE) satellite into space with a pre-recorded message from President Dwight D. Eisenhower wishing the world a merry Christmas.
Mercury Atlas Rocket Launch
The final Mercury flight by Gordo Cooper was the final use of the Atlas rocket for manned spaceflight. The Mercury spacecraft's two-man successor, Gemini, was too heavy for the Atlas to lift. Atlas played a supporting role in that program by launching Agena target vehicles that Gemini crews docked with in orbit. Perfecting docking techniques was a crucial step on the way to the Apollo moon landings.
The Atlas rocket saw service as part of America's ICBM fleet until it was retired from active service in 1965. The boosters were converted into satellite launchers, launching Surveyor spacecraft to the Moon, and Mariner probes to Mars.
The Atlas rocket has been upgraded over the decades, with the Atlas I, II, and III boosters delivering increasingly heavier payloads into space. The Atlas III rocket dropped the balloon tank design and incorporated a Russian RD-180 engine in its first stage. All three versions of the Atlas have since been retired.
Atlas V is currently used for military, NASA, and commercial payloads. Developed under the U.S. Air Force's Evolved Expendable Launch Vehicle program, the Altas V rocket debuted in 2002. The booster includes the RD-180 engine on the first stage and an American-built RL10 in the second stage.
United Launch Alliance, which builds the Atlas V, is working with XCOR Aerospace to develop a new upper stage rocket to replace the RL10. The new engine would be cheaper to build and operate, making the Atlas V less expensive to operate and better able to compete for commercial payloads.
Fifty years after John Glen first flew the Atlas rocket, that booster's descendent is being eyed for future human space missions. Three space companies - Blue Origin, Boeing, and Sierra Nevada Corporation - have designated the Atlas V rocket as their launcher of choice for crew vehicles they are developing under NASA's commercial crew program. Those flights are expected to begin by 2017.
The Atlas rocket celebrates the 55th anniversary of its first flight on December 17, 2012. At that age, most people are looking to retire. But the Atlas is just getting started.