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Miniature Bipolar Electrostatic Bipolar Electrostatic

All of the propellant molecules would be ionized. The figure presents a concept of a bipolar miniature electrostatic ion thruster for maneuvering a small spacecraft. The ionization device in the proposed thruster would be a 0.1-micronthick dielectric membrane with metal electrodes on both sides. Small conical holes would be micromachined through the membrane and electrodes. An electric potential of the order of a volt applied between the membrane electrodes would give rise to an electric field of the order of several megavolts per meter in the submicron gap between the electrodes. An electric field of this magnitude would be sufficient to ionize all the molecules that enter the holes.

Posted in: Briefs, TSP

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Mixed-Salt/Ester Electrolytes for Low-Temperature Li+ Cells

Electrolytes comprising, variously, LiPF6 or LiPF6 plus LiBF4 dissolved at various concentrations in mixtures of alkyl carbonates and alkyl esters have been found to afford improved low-temperature performance in rechargeable lithium-ion electrochemical cells. These and other electrolytes have been investigated in a continuing effort to extend the lower limit of operating temperatures of such cells. This research at earlier stages, and the underlying physical and chemical principles, were reported in numerous previous NASA Tech Briefs articles, the most recent being “Ester-Based Electrolytes for Low- Temperature Li-Ion Cells” (NPO-41097), NASA Tech Briefs, Vol. 29, No. 12 (December 2005), page 59. The ingredients of the solvent mixtures include ethylene carbonate (EC), ethyl methyl carbonate (EMC), methyl butyrate (MB), and methyl propionate (MP). The electrolytes were placed in Li-ion cells containing carbon anodes and LiNi0.8Co0.2O2 cathodes, and the electrical performances of the cells were measured over a range of temperatures down to –60 °C. The electrolytes that yielded the best low-temperature performances were found to consist, variously, of 1.0 M LiPF6 + 0.4 M LiBF4 or 1.4 LiPF6 in 1EC + 1EMC + 8MP or 1EC + 1EMC + 8MB, where the concentrations of the salts are given in molar units and the proportions of the solvents are by relative volume. This work was done by Marshall Smart and Ratnakumar Bugga of Caltech for NASA’s Jet Propulsion Laboratory.

Posted in: Briefs, TSP

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Cylindrical Piezoelectric Fiber Composite Actuators

Cylindrical actuators offer advantages over flat flexible actuators. The use of piezoelectric devices has become widespread since Pierre and Jacques Curie discovered the piezoelectric effect in 1880. Examples of current applications of piezoelectric devices include ultrasonic transducers, micropositioning devices, buzzers, strain sensors, and clocks. The invention of such lightweight, relatively inexpensive piezoceramic- fiber-composite actuators as macro fiber composite (MFC) actuators has made it possible to obtain strains and displacements greater than those that could be generated by prior actuators based on monolithic piezoceramic sheet materials. MFC actuators are flat, flexible actuators designed for bonding to structures to apply or detect strains. Bonding multiple layers of MFC actuators together could increase force capability, but not strain or displacement capability.

Posted in: Photonics, Briefs

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Curved Piezoelectric Actuators for Stretching Optical Fibers

Curved actuators produce greater displacements than do flat actuators. Assemblies containing curved piezoceramic fiber composite actuators have been invented as means of stretching optical fibers by amounts that depend on applied drive voltages. Piezoceramic fiber composite actuators are conventionally manufactured as sheets or ribbons that are flat and flexible, but can be made curved to obtain load-carrying ability and displacement greater than those obtainable from the flat versions. A curved actuator of this type can be fabricated by bonding a conventional flexible flat actuator to a thin metal backing sheet in a flat configuration at an elevated temperature so that upon cooling to room temperature, differential thermal contraction of the layers causes the laminate to become curved. Alternatively, such a curved actuator can be fabricated by bonding the layers together at room temperature using a curved mold.

Posted in: Photonics, Briefs

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Network Appliance Board (ESC Booth 2110)

VIA Technologies, Inc. (Taipei, Taiwan) has released the VIA NAB 7500 network appliance board for network security or gateway applications, including Firewall, VPN, UTM, Anti-Virus, and Intrusion Prevention System products.

Posted in: Products, Products

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Video Application Processors (ESC Booth 3028)

Renesas Technology America, Inc. (San Jose, CA) has added two new application processors to the SH-Mobile series. The SH-MobileL3V2 offers additional video formats, high-resolution video capture, and enhanced functionality to control image quality. The smallpackage SH-MobileUL is suitable for use in mainstream mobile phone models. The processors support the H.264/MPEG-4 AVC and VC-1 movingimage compression standard.

Posted in: Products, Products

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32-bit Flash Microcontrollers (ESC Booth 306)

STMicroelectronics (Mansfield, TX) has released the STM32 Family of 32- bit Flash microcontrollers based on ARM® Cortex™—M3 core. The STM32 is offered in the STM32F103 performance line, with 72 MHz clock frequency for 32- bit devices, and the STM32F101 Access line, with 36 MHz clock frequency for 16- bit devices. Both lines offer 32K to 128K of embedded Flash memory. At 72 MHz executing from Flash, the STM32 consumes only 36mA.

Posted in: Products, Products

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