ULTRASONIC TRANSDUCERS, DEPLOYMENT AND SIGNAL PROCESSING MEANS FOR CRYOFLUIDS

IF ONE CONSIDERS ULTRASONIC APPROACHES TO ACHIEVE THE REQUIRED BREAKTHROUGHS IN CRYOGENIC FLUID INSTRUMENTATION FOR ORBITING SPACECRAFT, PROBLEMS MUST BE SOLVED IN AT LEASTTHREE AREAS: (1) TRANSDUCERS (TO WITHSTAND LOW TEMPERATURES DOWN TO ABOUT 20K); (2) DEPLOYMENT (I.E., THE OPTIMUM LOCATION OF TRANSDUCERS, TO GENERATE AND DETECT ULTRASONIC WAVES IN A MINIMALLY-INVASIVE MANNER THAT INTERROGATES THE FLUIDS, OR INTERACTS WITH THEM, SUCH THAT THE MEASURANDS - FLOW, MASS ULLAGE, LIQUID PRESENCE OR ABSENCE - CAN BE "SENSED"; (3) SIGNAL PROCESSING (TO COMPUTE THE MEASURAND VALUES FROM THE ULTRASONIC SIGNAL'S TRANSIT TIME AND AMPLITUDE, WHILE NEGLECTING NOISE. IN PHASE I, PANAMETRICS'ANALYSIS AND EXPERIMENTS WILL CONCENTRATE ON (1) AND (2). A COMMERCIAL TRANSMITTER/RECEIVER/INTERVALOMETER WILL PROCESS THE SIGNALS FOR FEASIBILITY DEMONSTRATIONS IN WATER AND IN CRYOFLUIDS. TO SOLVE THERMAL STRESS AND HEAT TRANSFER PROBLEMS, NOVEL MAGNETOSTRICTORS AND PIEZO TRANSDUCERS WILL BE CONSTRUCTED USING MATERIALS OF NEARLY-MATCHED EXPANSION COEFFICIENTS, OF SLENDER FORM AND WITH POINT-CONTACT COUPLING. NOVEL DEPLOYMENT INCLUDES ACOUSTICALLY-ISOLATED POINT-SOURCE FLOWMETER TRANSDUCERS AND A MODIFIED H2-SLUSH DENSITY SENSOR OF 1X3 MM CROSS SECTION FOR MASS GAGING AND MASS FLOWMETERING. A NEW METHODOF REDUCING COHERENT NOISE WILL BE INVESTIGATED. IF SUCCESSFUL, THIS METHOD COULD ULTIMATELY IMPROVE THE ACCURACY OF NONINVASIVE ULTRASONIC MEASUREMENTS BY A FACTOR OF TEN IN A BROAD RANGE OF INDUSTRIAL APPLICATIONS.