THERMAL DIFFUSIVITY AND CONDUCTIVITY TPS ABLATOR TESTING DESCRIPTION WITH THE RECENT IMPROVEMENTS IN RAPID DATA ACQUISITION AND LABORATORY EQUIPMENT, TRANSIENT MEASUREMENT TECHNIQUES HAVE GAINED MARKEDLY IN POPULARITY. THE FLASH METHOD, HAS BEEN USED TO MEASURE MATERIALS WHOLE DIFFUSIVITIES RANGE FROM 0.001 TO 10 (A RANGE OF 10 OVER 4) OVER A TEMPERATURE RANGE FROM 80 TO 2500K (-315 TO 4050 F). THE METHOD USES SMALL EASY TO FABRICATE SAMPLES AND RESULTS CAN BE OBTAINED WITHIN SECONDS. THE FLASH METHOD WAS FIRST DESCRIBED IN 1960 BY PARKER, BUTLER, JENKINS, AND ABBOTT OF THE U.S. NAVY RADIOLOGICAL DEFENSE LABORATORY. IN THIS METHOD THE FRONT FACE OF A SMALL DISK-SHAPED SAMPLE (OFTEN ABOUT THE SIZE OF A SMALL COIN), IS SUBJECTED TO A VERY SHORT BURST OF RADIANT ENERGY. THE SOURCE OF THE RADIANT ENERGY IS USUALLY A LASER OR A XENON FLASH LAMP AND IRRADIATION TIMES ARE OF ONE MILLISECOND OR LESS. THE RESULTING TEMPERATURE RISE OF THE REAR SURFACE OF THE SAMPLE IS MEASURED AND THERMAL DIFFUSIVITY VALUES ARE COMPUTED FROM THE TEMPERATURE RISE VERSUS TIME DATA. OFTEN TIMES OF LESS THAN ONE SECOND ARE INVOLVED. THE AMBIENT TEMPERATURE MAY BE CONTROLLED BY A SMALL FURNACE TUBE OR CHILLER. NASA HAS A REQUIREMENT TO PROVIDE THE THERMAL CONDUCTIVITY, A MEASUREMENT OF THE CAPABILITY OF A MATERIAL TO TRANSFER HEAT, FOR 7 DIFFERENT FORMULAS OF A RESEARCH ABLATOR MATERIAL. THE THERMOPHYSICAL PROPERTIES RESEARCH LAB REQUIRES THE CONDUCTIVITY MEASUREMENTS AT THREE TEMPERATURES (ROOM TEMPERATURE, 250 DEGREES F, AND 500 DEGREES F) AND AT TWO PRESSURES (0.01 ATM AND 1.0 ATM). THE MEASUREMENTS WILL BE MADE BY MEASURING THE THERMAL DIFFUSIVITY OF THE MATERIAL THROUGH A TECHNIQUE KNOWS AS THE FLASH LASER DIFFUSIVITY METHOD. SMALL SAMPLES, APPROXIMATELY 0.5 INCH IN DIAMETER, ARE FLASHED WITH A SHORT PULSE LASER. THE TEMPERATURE ON THE OPPOSITE SIDE OF THE SAMPLE IS MEASURED AS A FUNCTION OF TIME. THE DIFFUSIVITY IS THE RESULTANT VALUE. TWO MORE PROPERTIES ARE NECESSARY IN ORDER TO DETERMINE THE CONDUCTIVITY OF THE SPECIMEN: DENSITY AND SPECIFIC HEAT. THE DENSITY OF THE SPECIMEN IS READILY DETERMINED THROUGH THE WEIGHT AND VOLUME OF THE SPECIMEN. THE SPECIFIC HEAT IS MEASURED IN A DIFFERENTIAL SCANNING CALORIMETER, IN WHICH THE AMOUNT OF ENERGY NEEDED TO INCREASE THE TEMPERATURE OF THE SPECIMEN A CERTAIN INCREMENT IS MEASURED. ONCE THE DIFFUSIVITY, DENSITY AND SPECIFIC HEAT OF THE SPECIMEN ARE DETERMINED, THE CONDUCTIVITY CAN BE DETERMINED THROUGH THE USE OF THE EQUATION: K = A X CP X P WHERE K = THERMAL CONDUCTIVITY A = THERMAL DIFFUSIVITY CP = SPECIFIC HEAT P = DENSITY