Mercury-Atlas 7  Mercury-Atlas 7, launched May 24, 1962, was the fourth crewed flight of Project Mercury. The spacecraft, named Aurora 7, was piloted by astronaut Scott Carpenter. He was the sixth human to fly in space. The mission used Mercury spacecraft No. 18 and Atlas launch vehicle No. 107-D. The flight was for three Earth orbits, essentially a repeat of John Glenn's Mercury-Atlas 6. However, a targeting error during reentry took the spacecraft off-course, delaying recovery of Carpenter and the spacecraft for an hour. Carpenter was held responsible, at least in part, for the landing error. Carpenter left NASA for the Navy SEALAB program in 1964. The original prime crew for Mercury Atlas-7 was to have been Deke Slayton, with Schirra as his back-up. However Slayton was removed from all flight crew availability after the discovery of cardiac dysrhythmia during a training run in the "g"-loading centrifuge. Slayton had chosen the name "Delta 7" for the spacecraft, as this would have been the fourth crewed flight and Delta (Δ) is the fourth letter in the Greek alphabet. Instead of using Schirra who was backup, it was decided to give the mission to Carpenter, who was the backup crew for Mercury-Atlas 6, had trained with John Glenn, and was considered the best-prepared astronaut. When Carpenter was given the mission, he renamed it "Aurora 7" for the open sky and the dawn, symbolizing the dawn of the new age. The number Seven was also chosen for the Mercury 7 astronauts. In addition, Carpenter's home address in his childhood was the corner of Aurora and Seventh Avenues in Boulder, Colorado, although at a talk he gave at the Boulder Theater in 2003, Carpenter admitted that he never made the connection between the "Aurora 7" spacecraft and his old address until friends pointed it out to him after he made the flight. Mercury spacecraft No. 18 was delivered to Cape Canaveral, Florida on November 15, 1961. While under checkout, the crew changed the periscope and also worked on the drogue parachute, to prevent it from firing prematurely as happened during the previous flight. In addition, a device known as a [446] "low-level commutator" was added, to measure the temperature around the capsule, recording temperature data from 28 positions on the spacecraft. The Atlas vehicle 107D was rolled out of the Convair factory in San Diego, California on February 25, 1962.