Dyer Brainerd Holmes, who directed NASA’s manned space flight program in the early 1960s and who was instrumental in developing the plan that sent the first astronauts to the moon, died Jan. 11 at a hospital in Memphis. He was 91.

He had complications from pneumonia, said a stepson, Pierce Ledbetter.

Mr. Holmes was a multi-talented engineer who had designed missiles and radar systems before taking charge of NASA’s manned space flight program in 1961. He was entrusted with a formidable task outlined by President John F. Kennedy in a speech on May 25, 1961:

“I believe that this nation should commit itself to achieve the goal, before this decade is out, of landing a man on the moon and returning him safely to the Earth.”

Under Mr. Holmes’s short but crucial tenure at NASA, John Glenn became the first U.S. astronaut to orbit the Earth, the Gemini and Apollo manned flight programs were developed, and the basic model for the spacecraft that took Neil Armstrong and Edwin E. “Buzz” Aldrin to the moon was designed.

Dyer Brainerd Holmes, head of manned space flight at NASA in the early 1960s, poses for a portrait on October 6, 1961. (NASA)

“When a great nation is faced with a technological challenge, it has to accept or go backward,” Mr. Holmes said in a 1962 cover story in Time magazine. “Space is the future of man, and the U.S. must keep ahead in space.”

Mr. Holmes was considered both a brilliant thinker and a strong administrator who could organize complex engineering and construction programs. While at RCA in the 1950s, he had a major role in developing the Talos antiaircraft missile and the electronic systems of the Atlas missile.

He also managed a federally sponsored project to design and install the Ballistic Missile Early Warning System, which was intended to detect Soviet missiles launched toward the United States. The monumental enterprise included the installation of football field-sized radar reflectors in Alaska, Greenland and England.

At NASA, Mr. Holmes oversaw the Mercury program when Glenn captivated the nation by circling the Earth on Feb. 20, 1962. There were also space flights by other astronauts in the original “Mercury Seven”: Alan B. Shepard Jr., Virgil I. “Gus” Grissom, Scott Carpenter, Walter Schirra and Gordon Cooper. (The seventh member, Donald K. “Deke” Slayton, was grounded at the time by a heart condition.)

Perhaps the greatest challenge facing Mr. Holmes was figuring how to accomplish Kennedy’s goal of reaching the moon. Three kinds of spacecraft were considered before NASA officials decided on a three-man mission in which a lunar module would fly around the moon while two astronauts descended to the surface in a smaller landing craft.

“We have to choose some plan,” Mr. Holmes told Time magazine in 1962, “or we’d better pack up and go home.”

In 1963, long before the first moon launch, Mr. Holmes abruptly resigned his position, reportedly because of meddling by NASA administrator James E. Webb. His departure was seen as a serious blow, but the Apollo program continued without him.

By the time Armstrong and Aldrin landed on the moon on July 20, 1969, Mr. Holmes looked on as something of a proud father.

“Perhaps when we hear the tired old cliche that America is getting soft,” he wrote in an essay in the New York Times, “we should remember such endeavors as these, and know that when given a challenge Americans today can be as hard, as aggressive and as brave as the men who founded this land.”

Dyer Brainerd Holmes was born May 24, 1921, in Brooklyn and grew up in East Orange, N.J. He graduated from Cornell University in 1943 with a degree in electrical engineering, then served in the Navy during World War II. He worked for Western Electric and the renowned Bell Laboratories in New Jersey before joining RCA in 1953.

After his NASA tenure, Mr. Holmes became an executive at Raytheon and eventually became president of the defense contracting and electronics giant before his retirement in 1986. He lived in Wellesley Hills, Mass., and was visiting relatives in Memphis when he died.

His first marriage, to Dorothy Bonnet Holmes, ended in divorce. His second wife, Roberta Donohue “Bobbie” Holmes, died in 1999.

Survivors include his wife since 2002, Mary Margaret England Wilkes Holmes of Wellesley Hills; two daughters from his first marriage, Katherine Kobos of Concord, Mass., and Dorothy “Pixie” Kather of Los Altos, Calif; three stepchildren from his third marriage, Scott P. “Pierce” Ledbetter and Baylor Ledbetter Stovall, both of Memphis, and Margaret Ledbetter Weaver of Hickory Valley, Tenn.; 11 grandchildren; and seven great-grandchildren.

During his two years at NASA, Mr. Holmes fended off naysayers — including congressmen and former president Dwight D. Eisenhower — who believed it was foolhardy to spend billions of dollars to send people to the moon. But Mr. Holmes believed the scientific and military credibility of the United States depended on the space program.

“We have plenty of skeptics,” he said in 1962. “They’re all over the place, and loud. But the head of the project can’t be a skeptic.”