Walter “Wally” Schirra Jr., who followed his barnstorming parents into the sky as a Navy combat pilot and the only astronaut to fly in the Mercury, Gemini, and Apollo space programs, has died. He was 84.

Schirra, who had been suffering from cancer, died early yesterday in La Jolla, Calif., according to Paul Parker, an investigator with the San Diego County medical examiner. The former astronaut died of a heart attack at Scripps Green Hospital, said Ruth Chandler Varonfakis, a longtime family friend and spokeswoman for the San Diego Air & Space Museum.

” 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.

A Naval Academy graduate credited with shooting down at least one enemy jet during the Korean War, Schirra was chosen as one of America’s seven original Project Mercury astronauts.

On October 3, 1962, he lifted off from Cape Canaveral in the Sigma 7 space capsule for America’s fifth manned space mission and third orbital flight.

Other than the temporary failure of a cooling system, the six-orbit Mercury flight went smoothly. Limiting maneuvering in a successful exercise to conserve fuel, he splashed down on target in the Pacific Ocean less than four miles from the carrier Kearsarge.

He pronounced himself “healthy as a bear” and “happy as a lark,” according to NASA.

Schirra visited President Kennedy in the White House and was awarded NASA’s Distinguished Service Medal. NASA administrator James Webb told him: “No one has flown better than you.”

In 1965, Schirra and fellow astronaut Thomas Stafford were selected to fly the Gemini 6 mission, the first attempt to rendezvous in space with another orbiting spacecraft. After several postponements because of a rocket failure and technical problems, Schirra and Stafford were launched from Cape Kennedy — the temporarily renamed Cape Canaveral — on December 15, 1965. Schirra’s assignment was to maneuver Gemini 6 close to the orbiting Gemini 7, which had been launched 11 days earlier and carried astronauts Frank Borman and James A. Lovell Jr.

Six hours after liftoff, Schirra brought Gemini 6 to within 6 to 10 feet of Gemini 7, close enough to see the other astronauts’s faces.

“It was done to perfection,” Schirra said later. “Until then, we came in second to the Soviets. But they had never done a rendezvous, and they didn’t do that kind of rendezvous for another 10 years.”

Schirra brought Gemini 6 down in the Atlantic, near the waiting carrier Wasp. Gemini 7 landed two days later.

“You have all moved up one step higher on the highway to the moon,” President Johnson telegraphed Webb.

Three years later, in October 1968, Schirra and fellow astronauts Donn Eisele and Walter Cunningham orbited the Earth in Apollo 7. The flight went well, but all three men came down with severe head colds. Schirra was the first person to take Actifed in space, much to the delight of the product’s manufacturer, Burroughs Wellcome.

Schirra, who said he grew up knowing he would be a pilot, soloed at 16, and in 1942, the year after the United States joined World War II, he was accepted into a three-year, accelerated course at the United States Naval Academy at Annapolis, Md.

Graduated and commissioned in 1945, he was assigned to the cruiser Alaska, but the war ended before he got to his ship. A year later, before completing flight training at Pensacola, Fla., Schirra married Josephine Cook Frasier, the stepdaughter of retired Navy Admiral James L. Holloway. On 1949, Schirra was assigned to the 154th Fighter Bomber Squadron, flying low-level bombing and strafing runs over Korea. Rated an outstanding pilot, he was awarded the Distinguished Flying Cross and two Air Medals.

In 1959, Schirra was selected as a Project Mercury astronaut. His responsibility, in addition to training for space flights, was the development and testing of the astronauts’s life-support systems.

Schirra got up and back three times, once each during the Mercury, Gemini, and Apollo programs. Despite the danger, the banter never stopped.

“There seems to be a lot of traffic up here,” Schirra radioed from Gemini 6 after one particularly close maneuver.

“Call a policeman,” Mr. Borman retorted from Gemini 7.

“I can see your lips moving,” the Gemini 7 pilot, Mr. Lovell, told Schirra.

“I’m chewing gum,” Schirra replied.

In 1969, after receiving the Collier trophy, the nation’s highest honor for achievement in aviation, Schirra left NASA and the Navy. He became a commentator for CBS News and often teamed with anchorman Walter Cronkite on space coverage.

He held executive positions with Regency Investors Inc., the ECCO Corp., Sernco Inc., the Johns-Mansville Corp., Goodwin Companies Inc., and Kimberly Clark, retiring from the business world in the late 1970s.

“I look back on those missions and I remember looking at the spaceship Earth,” he told a reporter in 1998. “It’s the most beautiful thing I’ve ever seen. We need to take care of it.”