Donald Kent Slayton better known as Deke Slayton, was an American World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 pilot and later, one of the original NASA

NASA

The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 Mercury Seven

Mercury Seven

Mercury Seven was the group of seven Mercury astronauts selected by NASA on April 9, 1959. They are also referred to as the Original Seven and Astronaut Group 1...

 astronaut

Astronaut

An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft....

s.

After joining NASA, Slayton was selected to pilot the second U.S. manned orbital spaceflight, but was grounded in 1959 by a heart murmur

Heart murmur

Murmurs are extra heart sounds that are produced as a result of turbulent blood flow that is sufficient to produce audible noise. Most murmurs can only be heard with the assistance of a stethoscope ....

. He then served as NASA's director of flight crew operations, making him responsible for crew assignments at NASA from November 1963 until March 1972.