One of the first seven 'original' American astronauts and the only one to fly Mercury, Gemini, and Apollo missions, Walter M. "Wally" Schirra passed away on Wednesday, after having been hospitalized for cancer.

"It's a terrible loss of a dear friend, cherished comrade and a brother," said Schirra's fellow Mercury astronaut Scott Carpenter. "Despite our good natured competition for flights into space, Wally strove to bring a smile to everyone he met and its with a smile that I will forever fondly remember him."

Schirra's first space flight came on October 3, 1962, as pilot of Mercury-Atlas 8. His spacecraft, which he named Sigma 7, made six orbits of the Earth in 9 hours and 13 minutes, proving that a pilot could carefully manage the limited quantities of electricity and maneuvering fuel that longer, more complex flights would require.

Schirra chose the name Sigma because it symbolized engineering precision, and a precisely engineered flight was the result, ending with a splashdown just five miles from the carrier Kearsage in the Pacific Ocean. True to his Navy background, Schirra elected to remain aboard the spacecraft until it was lifted to the deck of the carrier.

Schirra's second mission as command pilot of Gemini 6, was intended to perform the first rendezvous and docking between different spacecraft, a requirement for flights to the Moon. But the unmanned Agena target for Gemini 6 failed to reach orbit. Gemini 6 was removed from the pad and replaced by Gemini 7, which launched on December 4, 1965, on a planned 14-day flight.

Eight days later, Schirra and Thomas Stafford were in their Gemini spacecraft atop the Titan booster when it ignited, then shut down after only two seconds. Schirra had the option at that point of aborting, ejecting himself and Stafford, but chose to remain in the spacecraft while technicians confirmed that the booster was not going to explode.

As a result, three days later, Schirra and Stafford finally got off the ground, and less than six hours into the flight were "station keeping" just a few feet from astronauts Frank Borman and James Lovell in Gemini 7, 170 miles above the Mariana Islands.

Having made history conducting the first rendezvous in space, Schirra and Stafford returned to Earth.

Schirra's last flight in space teamed him with crewmates Donn Eisele and Walter Cunningham for the first manned mission of the Apollo spacecraft. Their 11-days on-board Apollo 7 qualified the redesigned Apollo for future flights to the Moon after the tragic fire that took the lives of the Apollo 1 crew in January 1967.

Schirra logged more than 12 and a half days in space on his three flights.

Walter Marty Schirra, Jr. was born on March 12, 1923, in Hackensack, New Jersey, and attended Dwight Morrow High School in Englewood. His father was a World War I ace who later flew in air circuses. Schirra's mother did wing-walking stunts. Despite his being around airplanes, Schirra did not solo until naval pilot training.

After high school, he spent a year at the Newark College of Engineering, then attended the U.S. Naval Academy at Annapolis, earning a bachelor of science degree in 1945. He later received honorary Ph.Ds from Lafayette College, Pennsylvania, Newark College of Engineering, and from the University of Southern California.

Schirra served in the surface Navy for a year prior to pilot training at Pensacola, Florida, earning his wings in 1948. He was a carrier pilot for three years then flew 90 combat missions in Korea as an exchange pilot with the US Air Force, shooting down two MiGs. Returning to the United States, he helped develop the Sidewinder missile while stationed at the Naval Ordnance Training Station at China Lake, California.

After a three year tour with the 124th Fighter Squadron aboard the carrier Lexington, Schirra attended the Naval Test Pilot School at Patuxent River, Maryland. He was flying as a test pilot at Pax River when chosen by NASA.

Schirra admitted later in life that he was reluctant to give up his Navy career for the space program. Nevertheless, Schirra was one of the seven astronauts chosen in April 1959. A precise pilot and engineer, Schirra also became notorious for his practical jokes.

"It was impossible to know Wally, even to meet him, without realizing at once that he was a man who relished the lighter side of life, the puns and jokes and pranks that can enliven a gathering," said NASA Administrator Mike Griffin in an e-mail to his agency's employees. "But this was a distraction from the true nature of the man. His record as a pioneering space pilot shows the real stuff of which he was made."

"We who have inherited today's space program will always be in his debt," he wrote on Thursdayof Schirra.

In addition to his three space flights, he served as back up to Scott Carpenter in 1962, and as back up command pilot for Gemini 3, the first manned Gemini mission. He and his Apollo 7 crew were originally assigned to fly the second manned Apollo flight, but were made back ups to the Apollo 1 astronauts in November 1966.

Schirra retired from the Navy as a captain and resigned from NASA on July 1, 1969, to become president of Regency Investors, a Denver, Colorado-based financial company. He served as an officer and director of several companies, eventually establishing his own consultancy, Schirra Enterprises.

As a result of developing a head cold during the Apollo 7 mission, Schirra later appeared in TV commercials for Actifed, a cold remedy. He also worked as an analyst for CBS News, teaming with Walter Cronkite on broadcasts of NASA missions.

He was active in a number of organizations and was a founding member and director of the Mercury Seven Foundation, later the Astronaut Scholarship Foundation. He served as a director of the San Diego Aerospace Museum in California, a trustee of the Scripps Aquarium and a member of the International Council of the Salk Institute.

He was awarded the Navy Distinguished Service Medal, three Distinguished Flying Crosses, three Air Medals, two NASA Distinguished Service Medals, the NASA Exceptional Service Medal and the Philippines Legion of Honor.

In 1990, he was inducted into the U.S. Astronaut Hall of Fame. Ten years later, Schirra was similarly honored with induction into the Naval Aviation Hall of Honor in 2000. In 2005, he was named a NASA Ambassador of Exploration and presented with a moon rock in his name.

In 1988, Quinlan Press published Schirra's memoirs titled Schirra's Space. In 2005, he collaborated on a second book, The Real Space Cowboys with author Ed Buckbee.

Schirra is survived by his wife Jo, daughter Suzanne and son Walter Schirra III.

In February 2002, author Francis French conducted an exhaustive interview with Schirra for collectSPACE.com:

'I worked with NASA, not for NASA'

Biographical information used in this article was adapted and excerpted with permission from Who's Who in Space: The First 25 Years by Michael Cassutt.

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