Walter M. "Wally" Schirra, one of the original Mercury 7 astronauts who later commanded a dramatic two-man Gemini mission and the first shakedown flight of an Apollo command module, has died of natural causes, his family told NASA. He was 84.

With Schirra's passing, only two of the Mercury 7 astronauts remain - former Sen. John Glenn and Scott Carpenter.

"With the passing of Wally Schirra, we at NASA note with sorrow the loss of yet another of the pioneers of human spaceflight," NASA Administrator Michael Griffin said in a statement. "As a Mercury astronaut, Wally was a member of the first group of astronauts to be selected, often referred to as the Original Seven."

Griffin said "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. 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."

NASA biography: http://www.jsc.nasa.gov/Bios/htmlbios/schirra-wm.html

Schirra's website: http://www.wallyschirra.com/

Schirra, Glenn, Carpenter, Alan Shepard, Donald "Deke" Slayton, Virgil "Gus" Grissom and Gordon Cooper were named America's first astronauts in April 1959. Shepard and Grissom were the first Americans in space, making suborbital up-and-down flights, before Glenn and then Carpenter flew into orbit.

Carpenter ran out of fuel and landed off course after attempting a series of science experiments, prompting internal criticism and a vow by Schirra to make the fifth Mercury mission an engineering test flight. He did just that and in the process, strengthened the role of the test pilot in the NASA astronaut hierarchy at the expense, some would claim, of science.

Schirra is the only Mercury astronaut to fly in all three of NASA's initial manned spacecraft, the single-seat Mercury capsule, the more sophisticated two-seat Gemini spacecraft and the three-seat Apollo command module.

He first blasted off aboard the Sigma 7 Mercury capsule on Oct. 3, 1962, completing six orbits in a flight lasting nine hours and 15 minutes, landing in the Pacific Ocean northeast of Midway Island.

Schirra then was named commander of Gemini 6, a flight originally designed to dock with an unmanned Agena Target Vehicle. But the Agena failed shortly after launch and the Gemini 6 flight was canceled. NASA managers then decided to let Schirra and crewmate Tom Stafford test rendezvous techniques using the manned Gemini 7 capsule as a target.

In a dramatic launch attempt eight days after Gemini 7 roared into orbit, Schirra's renamed Gemini 6A mission suffered a launch pad abort when the Titan's first-stage appeared to ignite and then shut down. Making a split-second decision by the seat of his pants, Schirra opted not to eject and three days later, he and Stafford thundered safely into orbit and successfully rendezvoused with Gemini 7.

Schirra then served as commander of the first Apollo command module, rocketing into orbit atop a Saturn 1B rocket with Walter Cunningham and Donn Eisele on Oct. 11, 1968. The flight followed a catastrophic 1967 launch pad fire that killed the original Apollo 1 crew of Grissom, Ed White and Roger Chaffee.

Schirra and his crewmates accomplished the primary goals of the shakedown mission, putting the command module through its paces in low-Earth orbit. But the commander caught a cold and grew quite testy during the flight, refusing to carry out some tasks and angering colleagues on the ground. Christopher Kraft, the man who created mission control at the Johnson Space Center in Houston, reportedly vowed that Schirra and his crewmates would never fly again.

"There was some real bickering back and forth between Wally and the ground," Cunningham said in a 1999 NASA interview. "I, frankly, have never felt like I had any kind of a problem with the ground, with going over the onboard tapes and air-to-ground and what have you. Donn, a little bit. But Wally was still demonstrating that it was Wallyıs flight and Wally was in charge."

In any case, at the conclusion of the Apollo 7 mission, Schirra had logged 295 hours and 15 minutes in space. He later served as a consultant for CBS News, pursued a variety of business interests and appeared in television commercials for the cold medicine Actifed.

He lived in Rancho Santa Fe, Calif., and is survived by his wife Josephine, his daughter Suzanne and son Walter Schirra III.

"We shared a common dream to test the limits of man's imagination and daring," Schirra once wrote. "Those early pioneering flights of Mercury, the performances of Gemini and the trips to the moon established us once and for all as what I like to call a spacefaring nation. Like England, Spain and Portugal crossing the seas in search of their nations' greatness, so we reached for the skies and ennobled our nation."