David Walker; Flew 4 Space Shuttle Missions

David M. Walker, an astronaut who made four space shuttle flights, including the 1989 flight that launched a probe that mapped the surface of Venus, died Monday of cancer. He was 56.

Walker died at the M.D. Anderson Cancer Center in Houston, NASA spokeswoman Eileen Hawley said.

Among the first group of space shuttle astronauts chosen by NASA in 1978, Walker flew as a pilot aboard the shuttle Discovery in 1984 and went on to command three shuttle missions, in 1989, 1992 and 1995.

Flying in space, Walker once said, is “the most spectacular human experience that I’ve been involved in.”

A native of Columbus, Ga., Walker graduated from the Naval Academy with a bachelor of science degree in 1966. He was designated a naval aviator after receiving flight training in Florida, Mississippi and Texas, and flew F-4 Phantoms aboard the carriers Enterprise and America. He was selected by NASA in January 1978 and became an astronaut that August. Walker logged more than 725 hours in space.

His career at NASA suffered a setback in 1990, when he was temporarily grounded for flight rule infractions. They included a 1989 incident in which the NASA T-38 jet trainer he was flying came within 100 feet of a Pan Am jetliner outside Washington.

Walker had flown to Washington for White House ceremonies honoring the crew of the space flight he had just commanded. The crew launched the Magellan probe that went on to map the surface of Venus.

As he prepared to return to space flight in 1992, Walker said, “I think had I decided I wanted to leave the space program some time back, I probably could have done so with at least some people probably happy to see me go. But I didn’t and . . . the opportunity to fly again is satisfying for me.”

He left NASA in 1996 to become vice president of sales and marketing for NDC Voice Corp. in Southern California, and then moved to Idaho, near Boise, Hawley said.

Astronaut Jim Voss, currently aboard the international space station Alpha, flew twice in space with Walker and was a good friend. The men spoke on Sunday via radio hookup, said station flight director John Curry. Mission Control planned to notify Voss and the other astronauts in orbit about Walker’s death on Monday, Curry said.

Walker is survived by his wife, Paige, and two sons. Funeral arrangements were incomplete.