A 69-year-old NASA engineer who suffered a heart attack after watching the shuttle Challenger explode has died.

Elmer Andrew Thomas of Titusville died Thursday at Jess Parrish Memorial Hospital in Titusville from an aneurysm in an artery leading to his heart, his wife, Pauline, said Friday.

Mr. Thomas, a mechanical engineer with the National Aeronautics and Space Administration for 18 years, was hospitalized Tuesday afternoon with chest pains after watching the launch from a NASA viewing room. He was moved out of the intensive care unit Thursday morning and died that afternoon.

He worked in NASA`s propellant department and helped load 385,000 gallons of liquid hydrogen into the shuttle`s 15-story external fuel tank, said his brother, Raymond Thomas of Ft. Lauderdale.

''I was afraid this would hurt him emotionally,'' Raymond Thomas said.

''But I thought he would just be in an emotional rut or something, not die from it.''

Mrs. Thomas said her husband had been in good health and had no previous heart problems. ''It was just a terrible shock for him,'' she said.