Special Coverage

Technique Provides Security for Multi-Robot Systems
Bringing New Vision to Laser Material Processing Systems
NASA Tests Lasers’ Ability to Transmit Data from Space
Converting from Hydraulic Cylinders to Electric Actuators
Automating Optimization and Design Tasks Across Disciplines
Vibration Tables Shake Up Aerospace and Car Testing
Supercomputer Cooling System Uses Refrigerant to Replace Water
Computer Chips Calculate and Store in an Integrated Unit
Electron-to-Photon Communication for Quantum Computing

Composite-Matrix Regenerators for Stirling Engines

One can exploit the properties of composites to reduce thermal and flow losses.

A prototype Stirling-engine regenerator containing a matrix made of carbon-fiber-based composite materials has been developed. The concept underlying this development effort is one of exploiting the properties of composite materials (e.g., the anisotropy of thermal conductivity of carbon fibers and the tailorability of composite materials and structures) to reduce thermal and flow losses below those of previously developed regenerators containing metal matrices.

Posted in: Briefs, TSP, Materials, Composite materials, Fibers, Stirling engines

Fabry-Perot Fiber-Optic Temperature Sensor

This is a prototype of rugged sensors for use in advanced engines.

A class of developmental photonic temperature-measuring systems is based on the use of miniature, fiber-optic-coupled Fabry-Perot interferometers as temperature transducers. These systems are intended for monitoring and control of advanced aircraft engines, conventional and nuclear powerplants, industrial plants, and other systems in which conditions could be too severe for electronic temperature sensors (thermocouples, thermistors, and bimetallic devices). Unlike electronic temperature sensors, these and other photonic temperature sensors do not pose a sparking hazard and are insensitive to electromagnetic interference at suboptical frequencies.

Posted in: Briefs, Electronics & Computers, Electromagnetic compatibility, Fiber optics, Lasers, Heat resistant materials, Thermal testing

Luneberg Lenses Made of Open-Cell Polyurethane Foams

Advantages would include light weight and ease of fabrication.

A Luneberg lens is a microwave lens consisting of a series of concentric shells of differing dielectric constants. The highest dielectric constant, or refractive index, resides at the core and the lowest, at the outer shell. Microwaves passing through this arrangement of shells are focused in the same manner as light passing through a glass lens.

Posted in: Briefs, TSP, Electronics & Computers, Optics

Evaluation of Exhaust Flows From Thrust-Vectoring Nozzles

A unique dual-flow cold-jet facility supports flight research programs.

A unique dual-flow, cold-jet facility has been developed and operated by California Polytechnic State University (Cal Poly) at San Luis Obispo for NASA Dryden Flight Research Center. The facility supports flight research on thrust-vectoring nozzles and thrust-vector control systems. To date, the facility has completed tests on subscale nozzles of the F/A-18 High Alpha Research Vehicle (HARV), the X-31 airplane, and the F-15 Advanced Control Technology for Integrated Vehicles (ACTIVE).

Posted in: Briefs, Physical Sciences, Nozzles, Test facilities

Monolithic Electrostatic Sector for Miniature Mass Spectrometers

The cost of fabrication is reduced considerably.

An improved miniature electrostatic sector has been designed for a miniature double-focusing mass spectrometer (see figure). Miniature mass spectrometers are essential components of high-performance, miniature, low-power instruments that are being developed for use in analyzing chemical compositions of small amounts of substances (e.g., toxic chemicals in the environment) in scientific laboratories, in industrial settings, and in the field.

Posted in: Briefs, TSP, Physical Sciences, Spectroscopy

Hollow Shaft Actuators with Harmonic Drive Gearing

They can be used in demanding applications such as industrial robots and servo systems.

Harmonic drive gearing is recognized by designers for its zero backlash, high gear ratios, and compact design features. A recent development by HD Systems incorporates a large hollow shaft through the actuator, offering many benefits to the machine designer. The FHA hollow shaft actuator series allows cables, shafts, or tubing to be passed concentrically through the center of the actuator. Through this innovation, the series provides precision motion control and high torque capacity in very compact packages.

Posted in: Briefs, Mechanical Components, Mechanics, Sensors and actuators

Photochromic Image-Plane Filter Extends Dynamic Range of CCD

The material of self-adjusting sunglasses enables CCD imaging of high-contrast scenes.

Figure 1. A High-Contrast Scene cannot readily be imaged in full detail on a CCD. Depending on the optical and electronic camera settings, the image tends to be either overexposed in the bright areas or underexposed in the dark areas.A simple technique for extending the dynamic range of a charge-coupled-device (CCD) video camera involves the use of photochromic material — the same material used in self-adjusting sunglasses. The dynamic range of an image is the ratio between the maximum and minimum brightness levels in the image. The dynamic range of a CCD is the ratio between an overexposure brightness level (above which the image becomes saturated or "washed out") and an underexposure level (below which details disappear into the darkness). The dynamic range of a CCD is less than that of the human eye; for example, a human observer can often see both shadowed and unshadowed features in a scene illuminated by sunlight, whereas a CCD cannot capture details simultaneously in both the brightest and darkest parts of the scene (see Figure 1).

Posted in: Briefs, TSP, Electronics & Computers, Charge coupled devices, Optics, Performance upgrades

Single-Event Latchup Protection of Integrated Circuits

A new technology shows much promise in recovering from single-event upsets.

Many commercially available advanced-technology CMOS and bipolar integrated circuits are susceptible to single-event latchup (SEL) effects caused by heavy ions or protons from cosmic rays or solar flares, making them unsuitable for satellite applications. Remanufacturing the integrated circuits in an inherently SEL-immune process has been an expensive and technically difficult option, as is the alternate option of incorporating latchup protection and recovery circuitry in the spacecraft system's electronics.

Posted in: Briefs, Electronics & Computers, Failure modes and effects analysis, Architecture, Avionics, Integrated circuits, Satellites

Inverse Rectennas for Two-Way Wireless Power Transmission

Suitable rectennas under reverse bias can be made to act as transmitters.

The term "inverse rectenna" may seem like an oxymoron at first glance. However, preliminary experiments have demonstrated that a rectenna of suitable design can be made to operate in an inverse mode, in which radio-frequency (RF) power is generated in the rectenna rectifier circuits and radiated by the rectenna antenna elements.

Posted in: Briefs, TSP, Electronics & Computers, Antennas, Wireless communication systems, Product development

Laser Anemometer Measures Flow in a Centrifugal Compressor

High-resolution data are representative of flows in practical centrifugal compressors.

Detailed measurements of complex flow fields within the NASA Low Speed Centrifugal Compressor (LSCC) have been acquired. The measurement data provide insight into the fundamental physics of flow in centrifugal compressors, and can be used to assess computational fluid dynamics codes and to develop flow-physics models. The resultant benefit is better predictive computational tools and shorter design cycle times.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Computational fluid dynamics, Measurements, Compressors, Test equipment and instrumentation

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