By FORD BURKHART
Victor Szebehely. a theorist ot celestial mechanics whose work in the 1950's provided the tools still used to chart the orbits of spacecratt, died on Sept.13 at his home in Austin, Tex. He was 76.
The cause was cancer, said his wife, Jo Betsy Lewallen.
At the Center for Space Research at the University ot Texas, and at the National Aeronautics and Space Administration, Dr. Szebehely studied Earth-toMoon trajectories, one aspect of a branch of engineering known as orbital mechanics.
It was delicate guesswork, as he himself said, involving the interactions of huge bodies in space and a vessel moving through their gravity fields. "You cannot do it precisely " he once said, "only approximately:"
Dr. Szebehely (pronounced SEB-ah-hay) trained a generation of experts in his calculations.
"He could apply the science of mechanics with great imagination to a specific problem," said Hans Mark, former chancellor at the university and former deputy administrator at NASA. "His work got us to the Moon."
Before Dr. Szebehely's work, orbits were calculated using theory from two sources, Newton's work in the 17th century and Einstein's general relativity theory of the early 20th century, said Dr. Raynor L. Duncombe, an emeritus professor of aerospace engineering at the University of Texas and a colleague of Dr, Szebehely since the 1950's.
"Then high-speed computers came along and opened up the whole field again," Dr. Duncombe said.
"The space age hit us all of a sudden.We had to have people cognizant of orbital mechanics, and there weren't any around."
Dr. Szebehely helped produce models of a broad range of forces that act upon the orbit of a spacecraft and that can help a ground crew figure where the vessel is headed, Dr. Duncombe said.
In Washington, Dr. Szebehely worked for the Navy in the 1950's then carried out space-related research at General Electric before Yale University hired him as an associate professor of astronomy in 1962. He moved to Texas in 1968, where he held the Richard B. Curran Centennial Chair of Engineering and was chairman of the department of aerospace engineering.
He also taught at Virginia State University, the University of Maryland and George Washington University.
Born in Budapest, he received his Ph.D. in engineering at the University of Budapest in 1948, doing research on how the gravity of two planets could affect orbiting spacecraft. He came to the United States the next year.
He was elected to the National Academy of Engineering in 1982. He was knighted by Queen Juliana of the Netherlands in 1957 and received the tirst Brouwer Award given by the American Astronomical Society, and the General Electric Senior Research Award. Earlier this year, he received the international prize of Italy's Accademia Nazionale Del Lincei for his career achievements in mathematical physics. He wrote or edited 18 books; including "Theory of Orbit" and "Adventures in Celestial Mechanics."
His first marriage, to Eva Szebehely, ended in divorce, as did his second to Patti Gill Szebehely.
In addition to his wife, he is survived by a daughter from his second marriage Julia Agnes Szebehely of Webster, Tex.