Chris Kraft: He was instrumental in establishing NASA's Mission Control operation. He originally joined NACA, NASA's predecessor. Assigned to the flight operations division, Kraft became NASA's first flight director.

He was on duty during such historic missions as America's first human spaceflight, first human orbital flight, and first spacewalk. Kraft served as flight director during all six of the manned Mercury missions. During the Gemini program, Kraft's role changed again, now being the head of mission operations, in charge of a team of flight directors, although still also serving as a flight director himself.

During the sixties, Kraft was a household name in America. He appeared on the cover of the August 27, 1965 issue of Time Magazine. Kraft had originally been surprised at Time Magazine's decision to put him on the cover, telling the NASA public affairs officer that "they've got the wrong guy. It should be Bob Gilruth ... not me." However, he eventually came to terms with the idea, and the portrait that was painted for the cover became one of his prized possessions.

At the beginning of the Apollo program, Kraft retired as a flight director to concentrate on management and mission planning. In 1972, he became director of the Manned Spacecraft Center (later Johnson Space Center).

Kraft retired from NASA in 1982 and after leaving, served as a consultant for a variety of companies. In 2001, he published his autobiography, Flight: My Life in Mission Control. It dealt with his life up until the end of the Apollo program. Age: 88.

Gene Krantz: He is best known for his role in directing the successful Mission Control team efforts to save the crew of Apollo 13 (he was played by Ed Harris in the Apollo 13 movie).

He is also noted for his trademark close-cut flattop hairstyle, and the wearing of dapper white "mission" vests (waistcoats), of different styles and materials made by his spouse, Marta Kranz, during missions for which he acted as Flight Director.

During the Apollo 13 mission, Kranz never actually used the phrase "Failure is not an option," which was created for the Ron Howard Apollo 13 movie. However, he so liked the way the line reflected the attitude of mission control, that he used it as the title of his 2000 autobiography.

Kranz would continue as a Flight Director through Apollo 17, when he worked his last shift overseeing the mission liftoff, and then was promoted to Deputy Director of NASA Mission Operations in 1974, becoming Director in 1983.

He retired from NASA in 1994 after the successful STS-61 flight that repaired the optically flawed Hubble Space Telescope in 1993. He flies an aerobatic aircraft and serves as a flight engineer for a restored B-17 Flying Fortress. Kranz's vest and pin from the Apollo 13 mission are currently on display in the National Air and Space Museum. In a 2010 Space Foundation survey, Kranz was ranked as the #2 most popular space hero. Age: 79.