CAMARILLO, Calif., March 27 Robert A. Rushworth, a retired Air Force major general who test-flew the pioneering X-15 rocket plane, died March 17 at his home here, the Air Force Association announced this week. He was 68.

He died of a heart attack, the organization said.

The X-15 paved the way for the nation's space program by testing unknowns like the effect of heat on an aircraft during re-entry.

General Rushworth, who was born in Madison, Me., flew a record 34 test flights in the X-15, traveling at six times the speed of sound in some cases. He won his astronaut rating in 1963 when he took the fixed-wing craft 54 miles high, just over halfway to outer space.

In 1990 he was inducted into the National Aviation Hall of Fame in Dayton, Ohio.

A lifelong pilot with 6,500 flying hours, he flew C-47 transports over the Himalayas into China in World War II, fought in the Korean War and flew 189 combat missions in Vietnam.

He was promoted to major general in 1975 and retired in 1981 as vice commander of the Aeronautical Systems Division at Wright-Patterson Air Force Base, Ohio.

He is survived by a daughter, Cheri Cox, of Ramstein Air Force Base in Germany, and two grandchildren.