Partially air coupled through transmission ultrasonic inspection of large solid rocket motors

Through transmission ultrasonic inspection techniques have many advantages as a survey technique. When solid rocket motors are inspected it is highly desirable not to contact the propellant with the transducer for reasons involving safety, damage to the product, and speed of inspection. The development of air coupled ultrasonic inspection techniques for large solid rocket motors is discussed. The appropriate frequency range appears to be around 50 kHz. Transducers that performed satisfactorily at these frequencies and suggested improvements are discussed