Physical Sciences

Mars-Optimized Solar Cells

NASA’s Jet Propulsion Laboratory, Pasadena, California Commercial triple junction solar cell designs were modified in their junction thicknesses, contact grid densities, and anti-reflective (AR) coating thicknesses to better match the Mars surface solar spectrum. Resulting cells show up to approximately 8% relative improvement in efficiency under the Mars solar spectrum, compared to non-optimized space solar cells, in testing performed at JPL.

Posted in: Briefs, Physical Sciences, Solar energy


Alternating Magnetic Field Forces for Satellite Formation Flying

John F. Kennedy Space Center, Florida Orbiting a large number of satellites in fixed formations will be critical to many future space missions, especially large-scale interferometers, telescopes, antennas, and gravity wave detectors. Consequently, extensive research has been devoted over the last 20 years to formation flying architectures, concentrating not only on the mission objective, but also on the technologies required to achieve a stable satellite formation. Several proposals have been suggested for determining the location of the satellites, but the more difficult problem is developing a system that can hold the satellites at those desired locations and orientations. The two most common solutions are to use microthrusters, though these require propellant and will eventually be depleted, or to choose orbital patterns that minimize relative perturbations, but for highly precise positioning, this is not adequate. Neither of these approaches solves the problem for long-duration missions such as a multi-element telescope where the mirrors must be located and oriented to a tolerance less than an optical wavelength.

Posted in: Briefs, TSP, Physical Sciences, Flight management systems, Satellites


Thermal Materials Protect Priceless Personal Keepsakes

Thermal protection technology used on the shuttles keeps valuables safe from fire. Most of us cannot comprehend the task of building something to withstand temperatures over 4,000 °F, but NASA can. The space shuttles endured such temperatures when returning to Earth’s atmosphere because of aerodynamic heating, or heating due to the combination of compression and surface friction from Earth’s atmosphere. For the vehicle to survive these conditions, NASA constructed a complex thermal protection system (TPS) for the exterior of the shuttle.

Posted in: Articles, Materials, Physical Sciences, Fire


Nanosensor/Cellphone Hybrid for Detecting Chemicals and Concentrations

Based on solid-state technology, the sensor requires no reagents and can be refreshed with an ultraviolet diode. Ames Research Center, Moffett Field, California Nanosensors have been developed for chemical detection using carbon nanotubes (CNTs). Unlike other chemical sensors, this solid-state approach requires no reagents and can be refreshed with a solid-state ultraviolet (UV) diode. The sensors possess high sensitivity (ppbv), fast response (≈2 s), high selectivity, low power (μW), and very small size (1 cm2 or less based on advanced miniaturization), and they are ideally suited for integration with wireless networks or cellphone type devices.

Posted in: Briefs, Physical Sciences, Sensors, Sensors and actuators, Chemicals


Coated or Doped Carbon Nanotube Network Sensors as Affected by Environmental Parameters

Applications include medical diagnostics, gas leak detection, and homeland security and defense. Ames Research Center, Moffett Field, California Chemical sensors have been developed over the past decades to detect gases and vapors at various concentration levels for deployment in a wide range of industrial applications. The detection usually centers on a change of a particular property or status of the sensing material, such as temperature, electrical, and optical characteristics. Other types of sensors include electrochemical cells, conducting polymer sensors, surface acoustic wave sensors, and catalytic bead sensors. Sensors based on nanotechnology promise to provide improved performance on all of these sensors compared to current micro and macro sensors.

Posted in: Briefs, Physical Sciences, Sensors, Sensors and actuators, Chemicals, Gases


Regenerable Internal CO Scrubber for Hydrogen Sensors

A guard electrode would protect the sensing electrode to maintain sensor sensitivity toward hydrogen. Lyndon B. Johnson Space Center, Houston, Texas Amperometric electrochemical sensors are commonly used for the detection of carbon monoxide (CO) and hydrogen (H2) in air. The electrochemistry of heterogeneous CO and H2 oxidations is similar enough that the sensors show significant cross-sensitivities between the two gases. Thus, in applications where H2 is being monitored in the presence of CO, amperometric hydrogen sensors will produce false positive responses due to the presence of CO. This error is further aggravated by the fact that the sensor’s response to CO is typically at least twice that for hydrogen on a volumetric basis. Furthermore, chronic CO exposure will poison or fatigue the H2 sensor electrodes and reduce the sensor sensitivity toward hydrogen.

Posted in: Briefs, Physical Sciences, Sensors, Sensors and actuators, Carbon monoxide


Nanostructure Sensor Determines Presence and Concentration of a Target Molecule in Fluid

This sensing system works with resonant frequencies. Ames Research Center, Moffett Field, California Several methods are presently being developed to sense the presence of a target molecule in small or modest concentration in a fluid. However, estimation of the concentration of the target molecule is unavailable where the fluid is substantially motionless relative to the sensor, in part because the fluid in equilibrium will have substantially the same concentration everywhere.

Posted in: Briefs, Physical Sciences, Sensors, Sensors and actuators


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