Special Coverage

Soft Robot “Walks” on Any Terrain
Defense Advanced Research Projects Agency
Using Microwaves to Produce High-Quality Graphene
Transducer-Actuator Systems for On-Machine Measurements and Automatic Part Alignment
Wide-Area Surveillance Using HD LWIR Uncooled Sensors
Heavy Lift Wing in Ground (WIG) Cargo Flying Boat
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

Using Transponders on the Moon to Increase Accuracy of GPS

Ranging to the Moon would be unaffected by the terrestrial atmosphere.

It has been proposed to place laser or radio transponders at suitably chosen locations on the Moon to increase the accuracy achievable using the Global Positioning System (GPS) or other satellite-based positioning system. The accuracy of GPS position measurements depends on the accuracy of determination of the ephemerides of the GPS satellites. These ephemerides are determined by means of ranging to and from Earth-based stations and consistency checks among the satellites. Unfortunately, ranging to and from Earth is subject to errors caused by atmospheric effects, notably including unpredictable variations in refraction.

Posted in: Briefs, Electronics & Computers, Global positioning systems, Global positioning systems (GPS), Global positioning systems, Global positioning systems (GPS), Satellites

Controller for Driving a Piezoelectric Actuator at Resonance

Unpredictable variations in resonance frequency are tracked.

A digital control system based partly on an extremum-seeking control algorithm tracks the changing resonance frequency of a piezoelectric actuator or an electrically similar electromechanical device that is driven by a sinusoidal excitation signal and is required to be maintained at or near resonance in the presence of uncertain, changing external loads and disturbances. Somewhat more specifically, on the basis of measurements of the performance of the actuator, this system repeatedly estimates the resonance frequency and alters the excitation frequency as needed to keep it at or near the resonance frequency. In the original application for which this controller was developed, the piezoelectric actuator is part of an ultrasonic/sonic drill/corer. Going beyond this application, the underlying principles of design and operation are generally applicable to tracking changing resonance frequencies of heavily perturbed harmonic oscillators.

Posted in: Briefs, Electronics & Computers, Electronic control systems, Sensors and actuators, Electronic control systems, Sensors and actuators

Coaxial Electric Heaters

These devices can be used safely where magnetic fields are not tolerated.

Coaxial electric heaters have been conceived for use in highly sensitive instruments in which there are requirements for compact heaters but stray magnetic fields associated with heater electric currents would adversely affect operation. Such instruments include atomic clocks and magnetometers that utilize heated atomic-sample cells, wherein stray magnetic fields at picotesla levels could introduce systematic errors into instrument readings.

Posted in: Briefs, TSP, Electronics & Computers, Electromagnetic compatibility, Electromagnetic compatibility, Electric power, Heating, ventilation, and air conditioning systems (HVAC), Heating, ventilation, and air conditioning systems (HVAC)

High-Density, High-Bandwidth, Multilevel Holographic Memory

Multiple terabytes could be read or written at a multigigahertz rate.

A proposed holographic memory system would be capable of storing data at unprecedentedly high density, and its data-transfer performance in both reading and writing would be characterized by exceptionally high bandwidth. The capabilities of the proposed system would greatly exceed even those of a state-of-the art memory system, based on binary holograms (in which each pixel value represents 0 or 1), that can hold ≈1 terabyte of data and can support a reading or writing rate as high as 1 Gb/s.

Posted in: Briefs, TSP, Electronics & Computers, Integrated circuits, Optics, Integrated circuits, Optics, Data management

Dual-Input AND Gate From Single-Channel Thin-Film FET

These transistors show potential as large-area, low-cost electronic circuitry on rigid and flexible substrates.

A regio-regular poly (3-hexylthiophene) (RRP3HT) thin-film transistor having a split-gate architecture has been fabricated on a doped silicon/silicon nitride substrate and characterized. RRP3HT is a semiconducting polymer that has a carrier mobility and on/off ratio when used in a field effect transistor (FET) configuration. This commercially available polymer is very soluble in common organic solvents and is easily processed to form uniform thin films. The most important polymer-based device fabricated and studied is the FET, since it forms the building block in logic circuits and switches for active matrix (light-emitting-diode) (LED) displays, smart cards, and radio frequency identification (RFID) cards.

Posted in: Briefs, TSP, Semiconductors & ICs, Architecture, Transistors, Architecture, Transistors, Product development, Fabrication, Polymers, Semiconductors

Fabrication of Gate-Electrode Integrated Carbon-Nanotube Bundle Field Emitters

Emission tips and a gate electrode are integrated into a monolithic device.

Figure 1. A Gate Electrode Overhangs a recess containing an array of bundles of carbon nanotubes (see part a). In part (b) are scanning electron micrograph (SEM) images of fabricated field-emitter devices.A continuing effort to develop carbon- nanotube-based field emitters (cold cathodes) as high-current-density electron sources has yielded an optimized device design and a fabrication scheme to implement the design. One major element of the device design is to use a planar array of bundles of carbon nanotubes as the field-emission tips and to optimize the critical dimensions of the array (principally, heights of bundles and distances between them) to obtain high area-averaged current density and high reliability over a long operational lifetime — a concept that was discussed in more detail in “Arrays of Bundles of Carbon Nanotubes as Field Emitters” (NPO-40817), NASA Tech Briefs, Vol. 31, No. 2 (February 2007), page 58. Another major element of the design is to configure the gate electrodes (anodes used to extract, accelerate, and/or focus electrons) as a ring that overhangs a recess wherein the bundles of nanotubes are located [see Figure 1(a)], such that by virtue of the proximity between the ring and the bundles, a relatively low applied potential suffices to generate the large electric field needed for emission of electrons.

Posted in: Briefs, Manufacturing & Prototyping, Fabrication, Nanomaterials

Photochemically Synthesized Polyimides

Single monomers are polymerized by exposure to ultraviolet light, without heating.

An alternative to the conventional approach to synthesis of polyimides involves the use of single monomers that are amenable to photopolymerization. Heretofore, the synthesis of polyimides has involved multiple-monomer formulations and heating to temperatures that often exceed 250 °C. The present alternative approach enables synthesis under relatively mild conditions that can include room temperature.

Posted in: Briefs, TSP, Materials, Forming, Productivity, Polymers

Hydroxide-Assisted Bonding of Ultra-Low-Expansion Glass

Preparation of bond surfaces is critical to success.

A process for hydroxide-assisted bonding has been developed as a means of joining optical components made of ultra-low-expansion (ULE) glass, while maintaining sufficiently precise alignment between. The process is intended mainly for use in applications in which (1) bonding of glass optical components by use of epoxy does not enable attainment of the required accuracy and dimensional stability and (2) conventional optical contacting (which affords the required accuracy and stability) does not afford adequate bond strength.

Posted in: Briefs, Materials, Optics, Optics, Joining, Glass

Optimized Carbonate and Ester-Based Li-Ion Electrolytes

This technology can be used in portable electronics, cell phones, and electric vehicles.

To maintain high conductivity in low temperatures, electrolyte co-solvents have been designed to have a high dielectric constant, low viscosity, adequate coordination behavior, and appropriate liquid ranges and salt solubilities. Electrolytes that contain ester-based co-solvents in large proportion (>50 percent) and ethylene carbonate (EC) in small proportion (<20 percent) improve low-temperature performance in MCMB carbon-LiNiCoO2 lithium-ion cells. These co-solvents have been demonstrated to enhance performance, especially at temperatures down to –70 °C. Low-viscosity, ester-based co-solvents were incorporated into multi-component electrolytes of the following composition: 1.0 M LiPF6 in ethylene carbonate (EC) + ethyl methyl carbonate (EMC) + X (1:1:8 volume percent) [where X = methyl butyrate (MB), ethyl butyrate EB, methyl propionate (MP), or ethyl valerate (EV)]. These electrolyte formulations result in improved low-temperature performance of lithium-ion cells, with dramatic results at temperatures below –40 °C. [See “Ester-Based Electrolytes for Low-Temperature Li-Ion Cells,” (NPO-41097) NASA Tech Briefs, Vol 29, No. 12 (December, 2005), p. 59.]

Posted in: Briefs, TSP, Materials, Optimization, Lithium-ion batteries, Lithium-ion batteries, Electrolytes, Materials properties

Ultrasonic/Sonic Impacting Penetrators

Soil can be probed relatively gently to a depth of several feet.

Ultrasonic/sonic impacting penetrators (USIPs) are recent additions to the series of apparatuses based on ultrasonic/sonic drill corers (USDCs). A USIP enables a rod probe to penetrate packed soil or another substance of similar consistency, without need to apply a large axial force that could result in buckling of the probe or in damage to some buried objects. USIPs were conceived for use in probing and analyzing soil to depths of tens of centimeters in the vicinity of buried barrels containing toxic waste, without causing rupture of the barrels. USIPs could also be used for other purposes, including, for example, searching for pipes, barrels, or other hard objects buried in soil; and detecting land mines.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Environmental testing, Soils, Tools and equipment, Drilling, Vibration, Vibration

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