Milton W. Rosen, a rocket engineer and early NASA executive who led the United States’ first satellite venture, Project Vanguard, died Dec. 30 at a retirement community in Bethesda, Md. He was 99.

The cause was complications from prostate cancer, said a grandson, Michael Shapiro.

Mr. Rosen began his career at the dawn of Space Age, conducting research on the development of radar and missiles at the Naval Research Laboratory in Washington. At the end of 1945, he teamed with nuclear physicist Ernst H. Krause to establish the lab’s first rocket development program.

Until then, the United States was limited in its high-altitude experiments, using only a finite supply of captured German V-2 missiles to conduct research. Mr. Rosen believed the lab’s experience developing and researching missiles during World War II would be the ideal foundation for studying the utility, functionality and design of rockets.

Within months, he, Krause and other colleagues began to design and develop the multistage Viking rockets. The high-altitude rockets, which were launched between 1949 and 1955, helped demonstrate the potential of space exploration.

Milton W. Rosen, second from left, was a rocket engineer and early NASA executive. (Martin Aircraft Co. )

“I feel it’s inevitable that our youngsters will see a lot more [of space] than we have,” Mr. Rosen said in an interview on the early 1950s CBS television show “Longines Chronoscope.”

From 1947 to 1955, he served as the rocket program’s chief engineer and supervised development of the research missiles.

Mr. Rosen later was the technical director of a successor space program, Project Vanguard. More funds and attention were available to space programs after the Soviet Union launched the first satellite to successfully orbit Earth, Sputnik, in October 1957. Explorer 1 became the first U.S. satellite to do so, in January 1958.

A few months later, after a succession of launch failures, Mr. Rosen oversaw the success of Vanguard 1, the first solar-powered satellite and the second U.S. artificial satellite placed in Earth’s orbit. It remains the oldest man-made satellite in orbit.

He moved to NASA headquarters in Washington at its inception in 1958 and served as the agency’s launch-vehicle director. He became a senior scientist in NASA’s office of the deputy associate administrator for defense affairs and deputy associate administrator for what is now science mission directorate.

In the 1960s, he helped oversee the development of innovative programs, including NASA’s Apollo spaceflight program in the 1960s.

Milton William Rosen was born in Philadelphia on July 25, 1915. He received a bachelor’s degree in electrical engineering from the University of Pennsylvania in 1937. Three years later, he joined the staff of the Naval Research Laboratory. He settled in Bethesda in the 1960s.

He retired from NASA in 1974 and later served at the National Academy of Sciences as executive director of its Space Applications Board. He taught a musical-comedy class at American University’s Institute for Learning in Retirement in Washington in the early 2000s.

He was a fellow of the American Rocket Society and wrote a book, “The Viking Rocket Story” (1955). Reviewing the book in the New York Times, science writer and editor Jonathan N. Leonard wrote, “Mr. Rosen has the literary touch, rare among engineers, to build up sympathy for both men and machines.”

Survivors include his wife of 65 years, Josephine “Sally” Haar of Bethesda; three children, Nancy Shapiro of Silver Spring, Md., Deborah Elkinson of Arlington, Va., and Janet Rosen of Silver Spring; and five grandchildren.

CORRECTION: An earlier version of this story should have specified that Vanguard 1 was the second artificial satellite to be placed in Earth’s orbit by the United States. The second artificial satellite to orbit the Earth successfully was the Soviet Union’s Sputnik 2. The story has been revised.