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Steady-State Thermal Test Methodology

This method allows the production of multiple test points from a single test. John F. Kennedy Space Center, Florida This innovation provides the following thermal properties data from a single steady-state test run: the effective thermal conductivity value (ke) for the full temperature difference, and multiple thermal conductivity values (λ) for intermediate temperatures. The test specimen (or material) is instrumented with one or more intermediate temperature sensors to allow the calculation of the multiple λ data points within the material and through its thickness. The methodology is particularly effective when coupled with any of the cryogenic boil-off calorimetry instruments (cryostats) developed by the Cryogenics Test Laboratory at NASA-KSC.

Posted in: Physical Sciences, Briefs, TSP

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Silicon Carbide Power Processing Unit for Hall Effect Thrusters

Prototype achieved 96.5% peak efficiency. John H. Glenn Research Center, Cleveland, Ohio A high-efficiency, rad-hard, 3.5-kW SiC power supply was developed for the power processing unit (PPU) of Hall effect thrusters. This work specifically targets the design of a PPU power supply for the HiVHAC (High Voltage Hall Accelerator) thruster. The PPU power supply under development utilizes components that were irradiated under TID (total ionizing dose) conditions to greater than 3 Mrad with little to no change in device performance.

Posted in: Physical Sciences, Briefs, TSP

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Intensity-Calibrated Hydrogen Flame Spectrum

Knowing the intensity spectrum of a hydrogen fire helps in evaluating fire detection methods. John F. Kennedy Space Center, Florida The National Aeronautics and Space Administration (NASA) uses large quantities of liquid hydrogen and has expended significant effort in the development, testing, installation, and maintenance of hydrogen fire detectors based on ultraviolet, near-infrared, mid-infrared, and/or far-infrared flame emission bands. Yet, prior to this work, there was no intensity-calibrated broadband hydrogen-air flame spectrum in the literature, making it difficult to compare the merits of different radiation-based hydrogen fire detectors.

Posted in: Physical Sciences, Briefs, TSP

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Exciting and Detecting Electromagnetic Energy in a High-Temperature Microwave Cavity

This weak-coupling approach can be used by industry for temperature-dependent dielectric measurements of high-value materials. NASA’s Jet Propulsion Laboratory, Pasadena, California There is a need to perform accurate, high-temperature, complex dielectric constant measurements at microwave frequencies on materials, such as those on the surface of Venus (surface temperature 460 °C). One approach is to excite and detect a TE10n mode resonance in a waveguide cavity heated in a high-temperature furnace. The standard way is to use commercial high-temperature transition adapters attached to cavity end plates containing small iris holes that weakly couple microwave energy into and out of the cavity. These high-temperature transition adapters are not simple to make, and are rather large in size. The addition of the transition adapter units to the waveguide cavity leads to a long combined system that in many cases makes it difficult, if not impossible, to insert in conventional high-temperature furnaces.

Posted in: Physical Sciences, Briefs, TSP

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Hollow aErothermal Ablation and Temperature (HEAT) Sensor for Tracking Isotherm Through TPS Material

This sensor can “see” through insulation. Ames Research Center, Moffett Field, California The Hollow aErothermal Ablation and Temperature (HEAT) sensor is a multifunction sensor designed to track an isotherm by making an independent transient measurement at a defined location in the sensor that is equal to the temperature at which its constituent materials char. By this same operating principle, the HEAT sensor tracks the transient char depth progression within a thermal protection system (TPS) material. In the case of a material that sublimes (such as Teflon), or when the aerothermal environment induces steady-state ablation, the HEAT sensor measures material ablation directly.

Posted in: Physical Sciences, Briefs, TSP

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Preparation, Planning, and Concept Demo of a Technique to Find ≈7-to-10-m Near Earth Asteroids

A paper describes a new technique designed to increase significantly the sensitivity for finding and tracking small, dim, and fast-moving near Earth asteroids (NEAs). The technique relies on a combined use of a novel data processing approach and a new generation of high-speed CCD cameras. These new cameras have very low readout noise (≈le–) and allow taking short exposures of moving objects at high frame rates, effectively “freezing” their motion on the CCD. A long-exposure image is synthetically created as if the telescope were tracking the object with a significantly higher SNR — an approach called “synthetic tracking.” By changing the shift/add vector, multiple dim objects moving in different directions can be detected in the same data set.

Posted in: Physical Sciences, Briefs, TSP

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Strobing to Mitigate Vibration for Display Legibility

Blur is eliminated with appropriate strobing frequency. Ames Research Center, Moffett Field, California This method mitigates the motion blur introduced when a display, and/or the operator reading it, is undergoing vibration (e.g. during the launch phase of spaceflight). If both the operator and the display are undergoing vibration, their respective impulses need not be in phase. This mitigation occurs when the display is illuminated at a strobing rate that corresponds with the frequency of the vibration. This can be done either by strobing the ambient illumination in the environment (e.g., if the operator is reading a reflective surface display), or by strobing the display itself (e.g., strobing the LED backlighting of an electronic display).

Posted in: Physical Sciences, Imaging, Briefs, TSP

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