Physical Sciences

Floating Ultrasonic Transducer Inspection System for Nondestructive Evaluation

Langley Research Center, Hampton, Virginia

This floating ultrasonic transducer inspection system is based on a “momentary touching” scheme wherein the ultrasonic transducer is in contact with the structure being scanned for a relatively short time while performing the measurement. A vibrating element is a fundamental component, allowing the probe to lift up and down quickly over the surface being scanned. The measurement duty cycle would be long enough to acquire the data. Using this configuration reduces the coefficient of friction significantly by more than 95% based on the measurement duty cycle.

Posted in: Briefs, Physical Sciences, Sensors, Inspections, Non-destructive tests
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Multiplexer for Multiple Sensors in a Vacuum Chamber

The multiplexer reduces the number of required feedthroughs and ports.

John F. Kennedy Space Center, Florida

Vacuum chamber testing at large facilities can require hundreds of instruments, necessitating even more feedthroughs. The number of instruments and sensors that can be fed into a vacuum chamber is limited by the number of feedthrough ports dedicated to instrumentation. Thus high-pin-count, mil-spec-style feedthroughs have been developed, but these are all custom-made and also expensive to make and replace. The high-pin-count feedthroughs also make it much harder to troubleshoot individual wires in case of a problem. By using a multiplexer within the vacuum chamber, the number of wires required per instrument can be reduced to much less than one. The multiplication of wires from within a vacuum chamber allows a drastic increase in sensor and instrumentation channel count, while using the same number of sensor ports and feedthroughs within an existing vacuum system.

Posted in: Briefs, TSP, Physical Sciences, Sensors, Sensors and actuators
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Miniaturized Schottky Diode Sensors for Hydrogen and Hydrocarbon Detection at High Temperatures

The sensors have application in fuel leak detection, environmental monitoring, fire detection, security monitoring, and engine emission monitoring.

John H. Glenn Research Center, Cleveland, Ohio

A miniaturized Schottky diode hydrogen and hydrocarbon sensor with the structure of catalytic metal-metal oxide-silicon carbide (SiC) has been developed. The major innovation of this work is the use of the metal oxide, palladium oxide (PdOx), as a barrier layer between the catalytic metal and the SiC in the gas-sensing structure. A major advantage of adding a PdOx barrier layer between the gate metal and the SiC is to prevent and alleviate chemical reactions between the gate metal and the SiC. Without the PdOx barrier layer, the gate metal and the substrate can easily form metal silicides at high temperature, leading to diode structure disruption. The metal oxide barrier layer can be incorporated into a gas-sensing structure by standard deposition techniques in a controlled manner. This oxide naturally forms with Pd in Pd-based gas sensor systems and can disrupt the gas sensor structure when formed in situ in an uncontrolled manner. However, purposely including this oxide in the Schottky barrier structure produces a stable barrier layer that enables a stable and sensitive gas sensor structure.

Posted in: Briefs, Physical Sciences, Sensors, Sensors and actuators, Exhaust emissions, Fire detection
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Analog Ceramic Isolated Voltage Sensor

John H. Glenn Research Center, Cleveland, Ohio

Galvanic isolated monitoring of voltages for launch vehicle, missiles, and space-deployed systems can be very challenging. Radiation exposure makes use of optics-based sensors difficult, as they can latch-up and become corrupted by the radiation environment; such devices can moreover be thermally challenged. Magnetic transformer-based methods of isolated voltage measurement require shielding to prevent stray magnetic interference from degrading or corrupting the readings; moreover, magnetic-based solutions are unable to measure voltages down to DC levels.

Posted in: Briefs, TSP, Physical Sciences, Sensors, Sensors and actuators, Ceramics, Launch vehicles, Missiles
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Flexible and Erectable Magnetic Field Response Sensors

Langley Research Center, Hampton, Virginia

The means to make a flexible and/or erectable magnetic field response sensor, a geometrically fixed capacitor mounting frame, a wireless dipstick, and an elastically flexible capacitor support have been developed. Either the capacitor mounting frame or the flexible, erectable magnetic field response sensor can be developed to take measurements in hazardous conditions, or in containers with environmentally harmful contents, such as a gasoline storage tank.

Posted in: Briefs, TSP, Physical Sciences, Sensors, Sensors and actuators
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Miniature Amperometric Solid Electrolyte Carbon Dioxide Sensor with Low Detection Limit

This sensor is applicable to fire detection, personal health monitoring, and environmental monitoring.

John H. Glenn Research Center, Cleveland, Ohio

A miniaturized amperometric electro-chemical (solid electrolyte) carbon dioxide (CO2) sensor using a novel and robust sensor design has been developed and demonstrated. Semiconductor microfabrication techniques were used in the sensor fabrication, and the sensor is fabricated for robust operation in a range of environments. The sensing area is 1.0 × 1.1 mm. The sensor is operated by applying voltage across the electrodes and measuring the resultant current flow at temperatures from 450 to 600 °C. Linear responses were achieved to the CO2 concentrations from 1% to 4%, and to the natural logrithmic concentrations of the CO2 from 0.02% to 1%. This CO2 sensor has the advantage of being simple to batch-fabricate, small in size, low in power consumption, easy to use, and fast with response time.

Posted in: Briefs, Physical Sciences, Sensors, Sensors and actuators, Carbon dioxide
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Improved Light Injection and Detection Methods for fNIRS Headgear for Use in Avionics and Astronautics

The benefits of the innovation allow the technique to move out of the controlled laboratory and into clinical and operational environments.

John H. Glenn Research Center, Cleveland, Ohio

Measuring hemoglobin concentration changes in the brain with functional near infrared spectroscopy (fNIRS) is a promising technique for monitoring cognitive state to optimize human performance during both aviation and space operations. The detection and prevention of performance decrement is also relevant to safety-critical operational tasks such as monitoring for air traffic control, performing surgery, and driving. Advances in optical instrumentation for fNIRS have been conceptualized and integrated into several new headgear prototypes designed for use by operators in the real world.

Posted in: Briefs, TSP, Physical Sciences, Avionics, Test equipment and instrumentation
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A High-Cross-Polarization-Isolation, Multi-Frequency Antenna for Cloud and Precipitation Research

Goddard Space Flight Center, Greenbelt, Maryland

The Global Precipitation Mission (GPM) has an immediate need for a matched-beam Ku-band/Ka-band antenna system that can be used as a component of a ground validation radar. Retrieval techniques based on both polarization and differential absorption at the two wavelengths can be used to provide additional insight into precipitation type and particle size distribution over a 10- to 40-km spatial domain. These measurements can then be compared with long range radar, such as the WSR-88D, and in situ sensors to provide a comprehensive dataset for evaluating and improving satellite-based precipitation estimates.

Posted in: Briefs, TSP, Physical Sciences, Antennas, Radar, Sensors and actuators
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External Magnetic Field Reduction Technique for Advanced Stirling Radioisotope Generator

New generators can be configured for very low magnetic emissions so as not to interfere with sensitive instrumentation.

John H. Glenn Research Center, Cleveland, Ohio

Linear alternators coupled to Stirling power converters are promising candidates for high-efficiency heat-to-electricity power conversion in space. Presently, the external magnetic field emissions of such converters may exceed the allowed emission limits for use with certain sensitive scientific instrumentation. This invention, based on concepts of magnetic moment balancing, can reduce such field emissions sufficiently to enable use of the space power Stirling converters in sensitive instrumentation missions.

Posted in: Briefs, Physical Sciences, Emissions, Electric power
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Advanced P-Band Spaceborne Radar System

A new imaging approach can overcome the fundamental limitations of conventional radar systems.

Goddard Space Flight Center, Greenbelt, Maryland

Low-cost, flexible spaceborne radar architectures are needed to provide critical data for Earth and science applications. An instrument concept was developed for an advanced spaceborne radar system that can measure terrestrial biomass (woody mass per unit area), ecosystem structure (height and density), and extent on a global scale. The PNTB band polarimetric radar architecture employs advanced techniques to increase the science value of the measurements while achieving it at a lower cost. The spaceborne radar concept leverages the existing airborne L-band digital beamforming synthetic aperture radar (DBSAR) and the new P-band digital beamforming (DBF) polarimetric and interferometric EcoSAR (ESTO IIP) architectures that employ DBF and reconfigurable hardware to provide advanced radar capabilities not possible with conventional radar instruments.

Posted in: Briefs, TSP, Physical Sciences, Architecture, Radar, Test equipment and instrumentation
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