Tech Briefs

Rapid-Chill Cryogenic Coaxial Direct- Acting Solenoid Valve

A commercially available cryogenic direct-acting solenoid valve has been modified to incorporate a rapid-chill feature. In the original application for which this feature was devised, there is a requirement to ensure that at all times, the valve outlet flow consists entirely or mostly of liquid; that is, there is a requirement to minimize vaporization of cryogenic liquid flowing through the valve. This translates to a requirement to chill interior valve surfaces in contact with the flowing liquid.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Cooling, Valves

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Variable-Tension-Cord Suspension/Vibration-Isolation System

Cord tensions are adjusted to optimize vibration-isolation properties. A system for mechanical suspension and vibration isolation of a machine or instrument is based on the use of Kevlar (or equivalent aromatic polyamide) cord held in variable tension between the machine or instrument and a surrounding frame. The basic concept of such a tensioned-cord suspension system (including one in which the cords are made of aromatic polyamide fibers) is not new by itself; what is new here is the additional provision for adjusting the tension during operation to optimize vibration-isolation properties.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Suspension systems, Performance upgrades, Vibration

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Techniques for Connecting Superconducting Thin Films

Junctions can be tailored to obtain desired levels of electrical resistance. Several improved techniques for connecting superconducting thin films on substrates have been developed. The techniques afford some versatility for tailoring the electronic and mechanical characteristics of junctions between superconductors in experimental electronic devices. The techniques are particularly useful for making superconducting or alternatively normally conductive junctions (e.g., Josephson junctions) between patterned superconducting thin films in order to exploit electron quantum-tunneling effects.

Posted in: Briefs, Manufacturing & Prototyping, Fastening, Joining, Conductivity

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Versatile Friction Stir Welding/Friction Plug Welding System

A single system could perform any FSW or FPW operation. A proposed system of tooling, machinery, and control equipment would be capable of performing any of several friction stir welding (FSW) and friction plug welding (FPW) operations. These operations would include the following:

Posted in: Briefs, TSP, Manufacturing & Prototyping, Electronic control systems, Manufacturing equipment and machinery, Welding

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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, Physical Sciences, Battery cell chemistry, Lithium-ion batteries, Electrolytes, Performance tests

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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, Physical Sciences, Downsizing, Rocket engines, Spacecraft

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Miniature Electrostatic Ion Thruster With Magnet

A miniature electrostatic ion thruster is proposed that, with one exception, would be based on the same principles as those of the device described in the previous article, “Miniature Bipolar Electrostatic Ion Thruster” (NPO-21057). The exceptional feature of this thruster would be that, in addition to using electric fields for linear acceleration of ions and electrons, it would use a magnetic field to rotationally accelerate slow electrons into the ion stream to neutralize the ions. This work was done by Frank T. Hartley of Caltech for NASA’s Jet Propulsion Laboratory.

Posted in: Briefs, TSP, Physical Sciences, Downsizing, Magnetic materials, Rocket engines, Spacecraft

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