Robert R. Gilruth; Oversaw Mercury, Apollo Space Flights, Led Johnson Space Center

Robert R. Gilruth, a key engineer and scientist in the American space program who headed the Johnson Space Center in Houston during the Apollo missions that put a man on the moon, has died.

Gilruth died Thursday of Alzheimer’s disease at a long-term care facility in Charlottesville, Va., the National Aeronautics and Space Administration announced in Washington. He was 86.

“There is no question that without Bob Gilruth there would not have been a Mercury, Gemini or an Apollo program,” the late George Low, who served as director of NASA’s manned space flight program, once said of Gilruth.

“Gilruth’s management style developed the best minds in the space program into the finest organization of its time,” Christopher C. Kraft Jr., his successor as director of the space center, said in an obituary of Gilruth in the New York Times on Friday. “Personally, I had a higher regard for Gilruth than any other person in my lifetime.”

A retiring man who inspired intense loyalty among young engineers, Gilruth was visibly uncomfortable in the public spotlight. In 1962, he froze speechless after President John F. Kennedy pulled him up to the microphone after a White House ceremony.

Gilruth was born in Nashwauk, a small town in the Iron Range of northern Minnesota. His father was the superintendent of schools and his mother taught mathematics. As a boy, Gilruth was interested in model boats and airplanes and would often write the National Advisory Committee for Aeronautics in Washington for technical data.

Gilruth went on to the University of Minnesota, where he graduated with a bachelor’s degree in 1935 and obtained his master’s the next year.

In 1937 he joined the staff of the National Advisory Committee for Aeronautics at Langley Field, Va., as a flight research engineer. His early work was in aircraft stability and control characteristics. From that he developed close associations with pilots that would later give him insights into man-machine relationships in space flight.

In 1945, he was put in charge of building a new research missile range at Wallops Island, Va., and of developing and directing its research program.

“I think it would have been hard to picture a better background for putting a man in space,” Gilruth later said of his time at Wallops Island.

When NASA was established in 1958, Gilruth was named to lead the team that created the basic design for Project Mercury, the program that put the first American into space.

His team of fewer than 10 engineers came up the everything from the design of the Mercury capsule to decisions on astronaut qualifications.

In 1961, Gilruth took his team to Houston, where they built and staffed the Manned Spacecraft Center, now the Johnson Space Center.

During his tenure as head of the center, Gilruth directed 25 manned space flights, including the first Mercury flight in 1961 and the first Apollo moon landing in 1969.

Gilruth was in charge of the development and operation of the Gemini spacecraft, a two-man craft used to perfect techniques for the control, rendezvous and linking of spaceships in Earth orbit.

He is credited with helping to conceive the method used to put astronauts on the moon and return them safely to Earth.

Instead of flying directly to the moon from Earth, Gilruth and his team created a strategy of flying to an orbit around the moon with a command ship and a lander linked together. The lander, carrying two astronauts, then separated from the command ship and descended to the lunar surface. Later, the moon explorers would rocket back into lunar orbit and rejoin their crew mate aboard the command ship for the trip back to Earth.

“His courage to explore the unknown, his insistence on following strict scientific procedures, and his technical expertise directly contributed to the ultimate success of the Apollo program and the landing of a man on the moon,” Daniel S. Goldin, the current NASA administrator, said on learning of Gilruth’s death.

After retiring from NASA in 1973, Gilruth spent his days sailing near his home in Kilmarnock, Va., and occasionally working at the Smithsonian Institution, which has his papers.

He is enshrined in the National Space Hall of Fame and received numerous honors, including the President’s Award for Distinguished Federal Civilian Service and the prestigious Collier Trophy from the National Aviation Club.

After the Challenger disaster in January 1986, Gilruth noted that “It’s very, very difficult, flying in space, particularly flying men in space. It’s not easy to do and you can’t say much more than that.”

He is survived by his wife, Georgene Evans Gilruth, of Charlottesville, a daughter and a stepson.

The family plans no funeral or memorial service.