Special Coverage

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
Vibration Tables Shake Up Aerospace and Car Testing
Supercomputer Cooling System Uses Refrigerant to Replace Water

Templates for Deposition of Microscopic Pointed Structures

These structures can be used as field emitters in plasma television screens.

Templates for fabricating sharply pointed microscopic peaks arranged in nearly regular planar arrays can be fabricated by a relatively inexpensive technique that has recently been demonstrated. Depending on the intended application, a semiconducting, insulating, or metallic film could be deposited on such a template by sputtering, thermal evaporation, pulsed laser deposition, or any other suitable conventional deposition technique. Pointed structures fabricated by use of these techniques may prove useful as photocathodes or field emitters in plasma television screens. Selected peaks could be removed from such structures and used individually as scanning tips in atomic force microscopy or mechanical surface profiling.

Posted in: Briefs, TSP, Manufacturing & Prototyping, Microscopy, Microscopy, Fabrication

Quench Crucibles Reinforced With Metal

Specimens can be quenched rapidly, without cracking ampules.

Improved crucibles consisting mainly of metal-reinforced ceramic ampules have been developed for use in experiments in which material specimens are heated in the crucibles to various high temperatures, then quenched by, for example, plunging the crucibles into water at room temperature. A quench crucible of the traditional type intended to be supplanted by the improved crucibles consists mainly of a ceramic or graphite ampule inside a metal cartridge, with a gap between the metal and the cartridge, as shown on the left side of the figure.

Posted in: Briefs, Materials, Containers, Ceramics, Metals, Test equipment and instrumentation

Adjustable Membrane Mirrors Incorporating G-Elastomers

Lightweight, flexible, large-aperture mirrors of a type being developed for use in outer space have unimorph structures that enable precise adjustment of their surface figures. A mirror of this type includes a reflective membrane layer bonded with an electrostrictive grafted elastomer (G-elastomer) layer, plus electrodes suitably positioned with respect to these layers. By virtue of the electrostrictive effect, an electric field applied to the G-elastomer membrane induces a strain along the membrane and thus causes a deflection of the mirror surface. Utilizing this effect, the mirror surface figure can be adjusted locally by individually addressing pairs of electrodes.

Posted in: Briefs, Materials, Mirrors, Calibration, Electronic control units, Electronic control units, Elastomers

High-Temperature Crystal-Growth Cartridge Tubes Made by VPS

Mechanical properties and maximum useful temperature exceed those of tungsten-alloy tubes.

Cartridge tubes for use in a crystal-growth furnace at temperatures as high as 1,600°C have been fabricated by vacuum plasma spraying (VPS). These cartridges consist mainly of an alloy of 60 weight percent molybdenum with 40 weight percent rhenium, made from molybdenum powder coated with rhenium. This alloy was selected because of its high melting temperature (≈2,550°C) and because of its excellent ductility at room temperature. These cartridges are intended to supplant tungsten/nickel-alloy cartridges, which cannot be used at temperatures above ≈1,300°C.

Posted in: Briefs, Materials, Fabrication, Manufacturing equipment and machinery, Spraying, Alloys, Heat resistant materials

Hall-Effect Thruster Utilizing Bismuth as Propellant

A laboratory-model Hall-effect spacecraft thruster was developed that utilizes bismuth as the propellant. Xenon was used in most prior Hall-effect thrusters. Bismuth is an attractive alternative because it has a larger atomic mass, a larger electron- impact- ionization cross-section, and is cheaper and more plentiful.

Posted in: Briefs, Materials, Propellants, Spacecraft fuel, Rocket engines, Performance tests

Coated Glass for Transparent Heating Elements

This coated glass can be used in high-humidity and high-altitude applications such as architectural and aircraft windows.

Applying an electric current to specially coated glass results in radiant heat energy. This process creates a transparent heating element with near- uniform surface temperatures. Manufacturing the heating element requires an ordinary pane of float glass. A fluorine-doped tin oxide coating (SnO2:F) measuring 0.25 micron thick is applied to one surface of the glass during fabrication. The coating conducts electricity, has a very tightly controlled resistance, has no appreciable color or structure, and is quite transparent. The coating has low emissivity properties that help contribute to the efficiency of the heated glass.

Posted in: Briefs, Materials, Heat transfer, Heat transfer, Fabrication, Coatings Colorants and Finishes, Coatings, colorants, and finishes, Conductivity, Glass

Deep-Sea Hydrothermal-Vent Sampler

This apparatus collects hydrothermal-plume samples uncontaminated by surrounding water.

An apparatus is being developed for sampling water for signs of microbial life in an ocean hydrothermal vent at a depth of as much as 6.5 km. Heretofore, evidence of microbial life in deep-sea hydrothermal vents has been elusive and difficult to validate. Because of the extreme conditions in these environments (high pressures and temperatures often in excess of 300°C), deep-sea hydrothermal- vent samplers must be robust. Because of the presumed low density of biomass of these environments, samplers must be capable of collecting water samples of significant volume. It is also essential to prevent contamination of samples by microbes entrained from surrounding waters. Prior to the development of the present apparatus, no sampling device was capable of satisfying these requirements.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Water, Bacteria, Test equipment and instrumentation, Marine vehicles and equipment

Mars Rocket Propulsion System

A report discusses the methane and carbon monoxide/LOX (McLOx) rocket for ascent from Mars as well as other critical space propulsion tasks. The system offers a specific impulse over 370 s — roughly 50 s higher than existing space-storable bio- propellants. Current Mars in-situ propellant production (ISPP) technologies produce impure methane and carbon monoxide in various combinations. While separation and purification of methane fuel is possible, it adds complexity to the propellant production process and discards an otherwise useful fuel product. The McLOx makes such complex and wasteful processes unnecessary by burning the methane/CO mixtures produced by the Mars ISPP systems without the need for further refinement.

Posted in: Briefs, Mechanical Components, Mechanics, Carbon dioxide, Methane, Propellants, Spacecraft fuel, Rocket engines

Two-Stage Passive Vibration Isolator

The design and testing of a structural system were implemented to hold the optics of the planned Space Interferometry Mission (SIM) at positions and orientations characterized by vibrational translation and rotation errors of no more than a few nanometers or a few milliarcseconds, respectively. Much of the effort was devoted to a test bed for verifying the predicted behavior of a vibration-isolation structural subsystem working together with an active control system for positioning and orienting the SIM optics.

Posted in: Briefs, Mechanical Components, Mechanics, Calibration, Optics, Optics, Vibration, Vibration, Mountings, Spacecraft

Altimetry Using GPS-Reflection/Occultation Interferometry

A Global Positioning System (GPS)- reflection/occultation interferometry was examined as a means of altimetry of water and ice surfaces in polar regions. In GPS- reflection/occultation interferometry, a GPS receiver aboard a satellite in a low orbit around the Earth is used to determine the temporally varying carrier-phase delay between (1) one component of a signal from a GPS transmitter propagating directly through the atmosphere just as the GPS transmitter falls below the horizon and (2) another component of the same signal, propagating along a slightly different path, reflected at glancing incidence upon the water or ice surface.

Posted in: Briefs, Physical Sciences, Altimeters, Global positioning systems, Global positioning systems (GPS), Altimeters, Global positioning systems, Global positioning systems (GPS), Weather and climate, Satellites

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