Explorer I Engineer Was 91

It is with sadness Aero-News learned this week Homer J. Stewart, an aerospace engineer who helped develop the first successful US satellite, died May 26 at his home in Altadena, CA at the age of 91.

An early pioneer of rocket research, Homer Joseph Stewart was born in Lapeer, MI, the son of a physicist. After graduating from the University of Minnesota, the Dubuque, IA native came to the California Institute of Technology for graduate study in 1936, and became interested in the early pioneering rocket research that was being carried out at the time by a small group of Caltech engineers and scientists -- chief among them Theodore von Kármán.

Stewart, von Kármán, and others began testing rockets in a rugged foothill area of the San Gabriel Mountains forming the nucleus of the research group that would evolve into the Jet Propulsion Laboratory, according to CalTech.

In 1938, Stewart joined the Caltech faculty, teaching both aeronautics and meteorology; but for many years divided his time between his faculty duties and research at JPL. As chief of the research analysis section, he participated in many rocket projects, including the WAC Corporal, the Corporal, the Sergeant, and the Jupiter C.

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, the first artificial satellite launched by the United States

His research interests included rocket exhaust velocity requirements for maintaining the exact trajectories of spacecraft. He also conducted research in wind-driven energy, using his knowledge of fluid flow to construct with von Kármán a turbine known as "Grandpa's Knob."

Built in the mountains of Vermont in the late 1930s, the machine generated up to a megawatt of power and operated through World War II in cooperation with a local electrical company. The project was abandoned after the war, in part because of the easy availability of cheap fossil-fuel energy.

In the late 1950's, Dr. Stewart worked as the director of planning and evaluation for the rookie agency, National Aeronautics and Space Administration. He was in charge of research analysis and calculating rocket exhaust velocities.

In 1959, he joined German rocket pioneer Wernher von Braun in testifying before a Senate panel which included then-Senator Lyndon B. Johnson. In their testomony, both scientists asserted Russian space technology was a good 12-20 months ahead of the US -- and that the USSR's missile guidance systems were far along enough to strike an American city from 5,000 miles away.

This prompted the senate panel to order a "national approach" to aerospace technology, according to The New York Times.

Stewart served continuously on the Caltech faculty from 1938 until his retirement in 1980.

FMI: www.caltech.edu, www.jpl.nasa.gov, http://history.nasa.gov/sputnik/expinfo.html