NDE OF ROCKET NOZZLES BY GAMMA RAY BACKSCATTERING

EFFECTIVE NONDESTRUCTIVE EVALUATION (NDE) METHODS ARE NEEDED TO DETECT CRACKS, POROSITY, VOIDS, AND OTHER ANOMALIES IN ROCKET NOZZLES.NOZZLE MATERIALS HAVE DEMONSTRATED INCONSISTENT MECHANICAL PROPERTIES,FORCING RELIANCE ON LARGE DESIGN MARGINS OF SAFETY AND EXPENSIVE PROOFTESTING. OBJECTIVE OF THE PROPOSED RESEARCH IS TO REMEDY THIS WITH GAMMA RAY BACKSCATTER COUNTING. UNLIKE CONVENTIONAL RADIOGRAPHY OR RADIOMETRY, GAMMA BACKSCATTERING REQUIRES ACCESS TO JUST ONE SURFACE, AND THROUGH PROPER COLLIMATION CAN BE MADE TO IGNORE SURFACE FEATURES AND SENSE ONLY DEFECTS BURIED IN A COMPOSITE STRUCTURE. RUGGED DETECTORS AND ELECTRONICS SIMILAR TO THOSE REQUIRED FOR A HAND-HELD INSPECTION UNIT HAVE BEEN SUCCESSFULLY BOOSTED INTO SPACE. SUCCESSFULDEVELOPMENT OF THIS NOVEL INSPECTION SYSTEM WILL BENEFIT THE AIR FORCE BY PERMITTING RAPID NONDESTRUCTIVE EVALUATION OF NOZZLES NOT ONLY AT ALL STAGES OF MANUFACTURING AND ASSEMBLY, BUT ALSO IN OPERATIONAL UNITS. THIS WILL BE REFLECTED IN COST AND WEIGHT SAVINGS ARISING FROM SMALLER DESIGHN MARGINS AND FROM DISCOVERY OF FLAWED MATERIAL EARLY IN THE MANUFACTURING CYCLE, AND IN GREATER MISSION-READINESS OF DEPLOYED NOZZLES. BECAUSE GAMMA SCATTERING IS AN EASILY ADAPTED GENERAL TECHNIQUE, MODIFIED VERSIONS OF THE SYSTEM PROPOSED HERE CAN FURTHER BENEFIT THE AIR FORCE AND ITS SISTER SERVICES AS AN INSPECTION TOOL FOR RELATED TYPES OF MATERIALS WHEREVER THEY ARE EMPLOYED. PHASE I WILL EXAMINE PERFORMANCE REQUIREMENTS AND TEST FOR FEASIBILITY, WITH EMPHASIS ON DEVELOPING A VERSATILE SYSTEM CAPABLE OF CHARACTERIZING SMALL DEFECTS AT VARYING DEPTHS. PENDING THE OUTCOME OF THESE TESTS, A PROTOTYPE INSPECTION SYSTEM WILL BE DEVELOPED AND TESTED IN PHASE II.