his spacecraft tests, Schirra tested his ability to use controls in a zero-gravity environment without sight. Throughout his mission, Schirra demonstrated the ability to act as a backup to automatic controls and manually fly the spacecraft. After six orbits, Schirra manually aligned his spacecraft over Africa and performed retrofire. Sigma 7 landed from the recovery ship, the aircraft carrier , in the central Pacific Ocean. Once Sigma 7 was on deck, Schirra activated the explosive hatch to egress the spacecraft, and received a large bruise, proving that Grissom had not intentionally opened his hatch on Liberty Bell 7. After Schirra returned to the US, he and his family were invited to the Oval Office at the White House to meet President Kennedy on October 16. Project Gemini At the beginning of the Gemini program, Alan Shepard was assigned to command Gemini 3 with Tom Stafford as the pilot, but they were replaced by a backup crew after Shepard was diagnosed with Ménière's disease, a disorder of the inner ear. Schirra and Stafford became the backup crew for the new Gemini 3 crew, Gus Grissom and John Young, and were subsequently scheduled for the Gemini 6 primary crew. Gemini 6 was originally scheduled to perform the first orbital docking with an Agena target vehicle. The Agena vehicle exploded during its launch into orbit on October 25, 1965, while Schirra and Stafford waited in their spacecraft to lift off. Program managers decided that rather than wait for a replacement Agena to be available, they would revise the mission, calling it Gemini 6A and having it attempt a rendezvous with Gemini 7, to be flown by Frank Borman and Jim Lovell. On December 4, 1965, Gemini 7 lifted off to begin its two-week mission. Gemini 6A prepared to launch on December 12, but its engines shut down less than two seconds after ignition. Despite protocols calling for the astronauts to eject from the spacecraft in the event of an engine shutdown, Schirra chose not to activate his and Stafford's rocket-powered ejection seats, saving them both from probable injuries and a further delay and possible cancellation of the mission. Gemini 6A lifted off on December 15 and successfully rendezvoused with Gemini 7 after five hours of flight. The two spacecraft maneuvered to within one foot of each other and kept station for 5 hours. Following the rendezvous, Gemini 6A deorbited on December 16 and