DEVELOPMENT OF ADVANCED MATERIALS FOR RAM ACCELERATOR PROJECTILES

THE RAM ACCELERATOR IS A RAMJET-IN-TUBE CONCEPT FOR ACCELERATING PROJECTILES TO A VERY HIGH VELOCITIES. IT USES PROPULSIVE CYCLE SIMILAR TO THAT OF A CONVENTIONAL RAMJET. THE RAM ACCELERATOR CAN OPERATE IN SEVERAL REGIONS: THERMALLY CHOCKED SUBSONIC, AND TWO OBLIQUE DETONATION MODES. THE IGNITION OF THE FUEL/OXIDATION MOISTURE IS ACHIEVED BY FORCING THE MIXTURE THOUGH A SENES OF SHOCKWAVES THAT INCREASE ITS TEMPERATURE UNTIL THE FUEL REACHES ITS IGNITION TEMPERATURE. THE TYPICAL RAM ACCELERATOR PROJECTILE IS FABRICATED FROM MAGNESIUM WITH MASSES IN THE RANGE OF 45 TO 70 GRAMS. THESE PROJECTILE HAVE OBTAINED VELOCITIES UP TO 2500 NI/S (4): HOWEVER, VELOCITIES OF UP TO 12 KM/SEC. ARE THEORETICALLY POSSIBLE. ONE OF THE POTENTIAL LIMITING FACTORS OF CURRENT RAM ACCELERATORS IS INCREASED MASS DUE TO THE USE OF MONOLITHIC METALS. ADVANCED GRAPHIC/EPOXY OR METAL MATRIX MATERIALS OFFER INCREASED SPECIFIC STRENGTHS OF 3, TO 5, THAT OF MAGNESIUM. A SIGNIFICANT PROJECTILE MASS REDUCTION WOULD ALLOW HIGHER VELOCITIES AT THE CURRENT THRUST LEVELS WHICH ARE ACHIEVABLE EXISTING LAUNCH FACILITIES. IN THIS PROGRAM, SPARTA WILL INVESTIGATE THE FEASIBILITY AND PAYOFF OF DESIGNING RAM ACCELERATOR PROJECTILES USING ADVANCED HIGH SPECIFIC STRENGTH COMPOSITE MATERIALS. SPARTA WILL ALSO INVESTIGATE THE USE OF HIGH PERFORMANCE THERMAL COATINGS; TO REDUCE THE NOSETIP AND LEADING EDGE ABLATIONS SEEN IN CURRENT FLIGHT TEST. THE USE OF ADVANCED MATERIALS AND COATINGS OFFERS THE POTENTIAL TO GREATLY INCREASE THE EFFICIENCY CURRENTLY ACHIEVABLE IN RAM ACCELERATOR FIRINGS.