Homer J. Stewart, the Caltech engineer who helped develop many of America's first satellites, died May 26 at his home in Altadena. He was 91.
Stewart played a key role in developing the Explorer I satellite, as well as having a hand in the development of the WAC Corporal, Corporal, Sergeant and Jupiter C rockets.
On a two-year leave of absence from Caltech, he served as director of planning and evaluation for the then-newly formed National Aeronautics and Space Administration. His specialty was analyzing the exhaust velocities required to lift a rocket into orbit and allow it to enter the correct orbit.
He also made recommendations for planning what would become the Apollo series of moon missions. NASA awarded him its Exceptional Service Medal in 1970.
Born in Elba, Mich., Stewart earned his bachelor's degree at the University of Minnesota in 1936, then came to Caltech for his graduate studies in aeronautics. In Pasadena, he joined a small group of faculty, including rocket pioneer Theodore von Karman, who began testing rockets in the foothills of the San Gabriel Mountains north of the campus.
This group was the nucleus of the research group that eventually became the Jet Propulsion Laboratory.
Stewart joined the Caltech faculty in 1938, two years before receiving his doctorate, and remained until his retirement in 1980.
He was chief of JPL's liquid propulsion systems division when JPL and the Army Ballistic Missile Agency, now the Marshall Space Flight Center, developed and launched Explorer I on Jan. 31, 1958 — the first U.S. satellite to reach orbit.
The Soviet Union had launched its own satellite, Sputnik, the previous October, kicking off what came to be known as the space race.
In 1959, Stewart and the former German rocket scientist Wernher von Braun testified before Congress that American researchers were 12 to 20 months behind the Soviets in the development of space technology.
Stewart said Soviet missiles had become sufficiently accurate to target U.S. cities from 5,000 miles away.
Stewart also recommended Cape Canaveral, Fla., as a launching site for long-range rockets and, eventually, for putting rockets into orbit. The military had originally preferred Southern California, but the Mexican government refused permission for missiles launched there to fly through its airspace.
He said the cape was "just perfect" because of the long flying corridor over the Atlantic Ocean.
Stewart also conducted research in wind-driven energy, joining with Von Karman to build a turbine on a summit known as Grandpa's Knob in the mountains of Vermont in the late 1930s. The installation generated up to a megawatt of power and operated successfully through World War II, but it was abandoned after the war because of the easy availability of cheap fossil-fuel energy.
He is survived by two daughters, Barbara Mogel of Chesapeake Beach, Md., and Kay Stewart of San Diego; a son, Dr. Robert J. Stewart of Burien, Wash.; two sisters, Mary Jane Postels of Nisswa, Minn., and Doris Larson of Chanhassen, Minn.; a brother, Robert, of Dallas; and two grandchildren.