Tech Briefs

Counterrotating-Shoulder Mechanism for Friction Stir Welding

The weights and costs of fixtures for holding workpieces could be reduced.

A counterrotating-shoulder mechanism has been proposed as an alternative to the mechanism and fixtures used in conventional friction stir welding. The mechanism would internally react most or all of the forces and torques exerted on the workpiece, making it unnecessary to react the forces and torques through massive external fixtures.

Posted in: Briefs, Manufacturing & Prototyping, Adaptive control, Manufacturing equipment and machinery, Welding
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Strain Gauges Indicate Differential-CTE-Induced Failures

Failures are indicated by changes in slopes of strain versus temperature.

A method of detecting mechanical failure induced by variation in temperature at an adhesive bond between two materials that have different coefficients of thermal expansion (CTEs) involves monitoring of strain-gauge readings. This method can be regarded as an exploitation of the prior observation that the readings of strain gauges commonly used in tensile and compressive testing of material specimens include features indicative of incremental failures in the specimens. In this method, one or more strain gauges are bonded to either or both of the two materials near the bond between the materials. (The adhesive used to bond the strain gauges would not ordinarily be the same as the one used to bond the two materials). Then strain-gauge readings are recorded as the temperature of the materials is varied through a range of interest. Any significant discontinuity in the slope of the resulting strain-versus- temperature curve(s) is taken to be a qualitative indication of a failure of the bond between the two materials and/or a failure within one of the materials in the vicinity of the bond.

Posted in: Briefs, TSP, Manufacturing & Prototyping, Failure modes and effects analysis, Joining, Adhesives and sealants, Composite materials, Test equipment and instrumentation, Thermal testing
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Antibodies Against Three Forms of Urokinase

These antibodies can be used to measure small quantities of three molecular forms of urokinase.

Antibodies that bind to preselected regions of the urokinase molecule have been developed. These antibodies can be used to measure small quantities of each of three molecular forms of urokinase that could be contained in microsamples or conditioned media harvested from cultures of mammalian cells. Previously available antibodies and assay techniques do not yield both clear distinctions among, and measurements of, all three forms.

Posted in: Briefs, Bio-Medical, Medical, Biological sciences, Diseases, Test procedures
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Understanding and Counteracting Fatigue in Flight Crews

The materials included in the collection of documents describe the research of the NASA Ames Fatigue Countermeasures Group (FCG), which examines the extent to which fatigue, sleep loss, and circadian disruption affect flight-crew performance. The group was formed in 1980 — in response to a Congressional request to examine a possible safety problem of uncertain magnitude due to transmeridian flying and a potential problem due to fatigue in association with various factors found in air-transport operations — and was originally called the Fatigue/Jet Lag Program. The goals of the FCG are: (1) the development and evaluation of strategies for mitigating the effects of sleepiness and circadian disruption on pilot performance levels; (2) the identification and evaluation of objective approaches for the prediction of alertness changes in flight crews; and (3) the transfer and application of research results to the operational field via classes, workshops, and safety briefings.

Posted in: Briefs, Bio-Medical, Medical, Mental processes, Reaction and response times, Aircraft operations, Personnel
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Dual-Beam Atom Laser Driven by Spinor Dynamics

A Bose-Einstein condensate is adiabatically compressed to drive coherent spin-mixing evolution.

An atom laser now undergoing development simultaneously generates two pulsed beams of correlated 87Rb atoms. (An atom laser is a source of atoms in beams characterized by coherent matter waves, analogous to a conventional laser, which is a source of coherent light waves.) The pumping mechanism of this atom laser is based on spinor dynamics in a Bose-Einstein condensate. By virtue of the angular- momentum conserving collisions that generate the two beams, the number of atoms in one beam is correlated with the number of atoms in the other beam. Such correlations are intimately linked to entanglement and squeezing in atomic ensembles, and atom lasers like this one could be used in exploring related aspects of Bose-Einstein condensates, and as components of future sensors relying on atom interferometry.

Posted in: Briefs, TSP, Physical Sciences, Architecture, Lasers, Product development, Pumps
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Active Correction of Aberrations of Low-Quality Telescope Optics

Relatively inexpensive optical components could be used in free-space optical communications.

A system of active optics that includes a wavefront sensor and a deformable mirror has been demonstrated to be an effective means of partly correcting wavefront aberrations introduced by fixed optics (lenses and mirrors) in telescopes. It is envisioned that after further development, active optics would be used to reduce wavefront aberrations of about one wave or less in telescopes having aperture diameters of the order of meters or tens of meters. Although this remaining amount of aberration would be considered excessive in scientific applications in which diffraction-limited performance is required, it would be acceptable for free space optical-communication applications at wavelengths of the order of 1 μm.

Posted in: Briefs, TSP, Physical Sciences, Mirrors, Calibration, Optics, Sensors and actuators, Wireless communication systems
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Rugged, Tunable Extended-Cavity Diode Laser

This laser is relatively insensitive to vibration.

A rugged, tunable extended-cavity diode laser (ECDL) has been developed to satisfy stringent requirements for frequency stability, notably including low sensitivity to vibration. This laser is designed specifically for use in an atomic-clock experiment to be performed aboard the International Space Station (ISS). Lasers of similar design would be suitable for use in terrestrial laboratories engaged in atomic-clock and atomic-physics research.

Posted in: Briefs, TSP, Physical Sciences, Lasers, Vibration, Mountings, Reliability, Spacecraft
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Balloon for Long-Duration, High-Altitude Flight at Venus

A document describes a 5.5-m-diameter, helium-filled balloon designed for carrying a scientific payload having a mass of 44 kg for at least six days at an altitude of about 55 km in the atmosphere of Venus. The requirement for floating at nearly constant altitude dictates the choice of a mass-efficient spherical super-pressure balloon that tracks a constant atmospheric density. Therefore, the balloon is of a conventional spherical super-pressure type, except that it is made of materials chosen to minimize solar radiant heating and withstand the corrosive sulfuric acid aerosol of the Venusian atmosphere.

Posted in: Briefs, TSP, Physical Sciences, Test equipment and instrumentation
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Wide-Temperature-Range Integrated Operational Amplifier

A document discusses a silicon-oninsulator (SOI) complementary metal oxide/ semiconductor (CMOS) integrated- circuit operational amplifier to be replicated and incorporated into sensor and actuator systems of Mars- explorer robots. This amplifier is designed to function at a supply potential ≤5.5 V, at any temperature from –180 to +120 °C. The design is implemented on a commercial radiationhard SOI CMOS process rated for a supply potential of ≤3.6 V and temperatures from –55 to +110 °C. The design incorporates several innovations to achieve this, the main ones being the following:

Posted in: Briefs, TSP, Electronics & Computers, Amplifiers, Architecture, Integrated circuits, Sensors and actuators, Robotics, Spacecraft
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Dual-Beam Atom Laser Driven by Spinor Dynamics

A Bose-Einstein condensate is adiabatically compressed to drive coherent spin-mixing evolution.

NASA’s Jet Propulsion Laboratory, Pasadena, California

An atom laser now undergoing development simultaneously generates two pulsed beams of correlated 87Rb atoms. (An atom laser is a source of atoms in beams characterized by coherent matter waves, analogous to a conventional laser, which is a source of coherent light waves.) The pumping mechanism of this atom laser is based on spinor dynamics in a Bose-Einstein beam running-wave dipole trap that has been formed by focusing of a CO2-laser beam. By a technique that is established in the art, the trap is loaded from an ultra-high-vacuum magneto-optical trap that is, itself, loaded via a cold atomic beam from an upstream two-dimensional magneto-optical trap that resides in a rubidium-vapor cell that is differentially pumped condensate. By virtue of the angular-momentum conserving collisions that generate the two beams, the number of atoms in one beam is correlated with the number of atoms in the other beam. Such correlations are intimately linked to entanglement and squeezing in atomic ensembles, and atom lasers like this one could be used in exploring related aspects of Bose-Einstein condensates, and as components of future sensors relying on atom interferometry.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Architecture, Lasers, Product development, Pumps
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