Question: Which Mercury Seven astronaut waited 16 years to make his first spaceflight?
Answer: Deke Slayton. One of the original seven astronauts picked in 1959, Slayton was set to fly the second American orbital mission until doctors found an irregular heartbeat and grounded him in 1962. He spent the next decade running NASA’s astronaut office and picking the crews for Gemini and Apollo, then was cleared to fly in 1972. He finally reached orbit in July 1975 on the Apollo-Soyuz mission, the first joint flight with the Soviet Union, and spent nine days in space at age 51.
