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

Plasma Window Technology for Propagating Particle Beams and Radiation from Vacuum to Atmosphere

Vacuum and atmosphere are separated by a plasma window to facilitate nonvacuum electron-beam welding and nonvacuum material processing.

Plasma windows can separate vacuum and atmosphere, or regions of high and low vacuums, in a way which facilitates transmission of various particle beams and/or radiation from low- to high-pressure regions. In a prototype device, a stabilized plasma arc was properly configured to function as a nonsolid plasma window. Since charged particles can be focused by these arcs, focusing of such beams is a secondary function of this device.

Posted in: Briefs, Electronics & Computers, Windows and windshields, Waveguides, Waveguides, Gases

Bounceless Switch/Monostable Multivibrator

Monostable circuit debounces a switch while allowing for the monostable circuit to be activated by an electronic circuit.

A circuit has been designed to debounce a mechanical switch, which is used to activate a digital circuit. Contacts tend to make and break connections several times until the switch contacts settle out. The repetitive activity plays havoc with digital circuits because more than one state condition could be activated by the switch as it bounces around between state conditions.

Posted in: Briefs, Electronics & Computers, Integrated circuits, Switches, Integrated circuits, Switches, Vibration, Vibration

Advanced Cryogenic Insulation System for Graphite/Organic Resin Composite Cryogenic-Tank Structures

Foam-filled honeycomb cores withstand tensile strain test in cryogenic conditions.

Engineers at Rockwell International Corporation's Space System Division have developed a new method of insulating composite structural material that will stand up to the harsh environment of space. The new liquid-hydrogen cryogenic tankage proposed for advanced launch systems — such as the Reusable Launch Vehicle and the X-33 — will be made from a graphite/epoxy material. Although this composite material will produce a lighter-weight cryogenic insulation tank, current cryogenic insulation materials did not endure rigorous stress testing.

Posted in: Briefs, Materials, Containers, Composite materials, Graphite, Insulation, Resins, Lightweighting, Spacecraft

Deflection of Stretched Circular Membrane Under Pressure

Previously reported equations are generalized to account for a stretch preload.

Equations have been derived to describe the deflection of a circular membrane under both in-plane and transverse loads. More specifically, the equations describe the radial (in-plane) and perpendicular-to-the-plane deflections for the case of a circular membrane that has been stretched at its periphery with a uniform preload to keep it taut, then clamped rigidly at its periphery, and then subjected to differential pressure.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Mathematical models, Test procedures

Impedance-Based Cable Tester

Short and open circuits can be located relatively easily.

The figure illustrates the major functional blocks of an impedance-based cable-testing apparatus that can locate an open or short circuit in a cable. There is no need to disconnect the cable from all other equipment in preparation for a test – an advantage in a system in which cable connections are located in places that are not readily accessible.

Posted in: Briefs, Electronics & Computers, Electric cables, Electric cables, Product development, Non-destructive tests, Test equipment and instrumentation

Controlled-Orientation Short-Fiber Composite Bodies

Microstructurally controlled composite properties mimic biomaterials.

A technique for depositing materials into position using a positive-displacement extruder to build up a body has been developed. This technique also includes a process to prepare composite materials through a solid free-body forming process containing directionally aligned short-fiber reinforcement and ceramic-particulate reinforcement (of which at least a portion is derived from an alkoxide precursor).

Posted in: Briefs, Manufacturing & Prototyping, Forming, Composite materials, Fibers

Transmitting Data Signals via Fiber-Optic Power Lines

Optical power carrier signals are modulated with data signals.

Data signals can be transmitted via the same optical fibers that are used to transmit power from base stations to remote stations containing sensors and associated circuitry. [A prototype system based on fiber-optic transmission of data and power is described in "General-Purpose Optically Powered Sensor and Control System" (NPO-19604), which is the first of two articles preceding this one.] The implementation of the present data-transmission/power-transmission concept involves the choice of one of several possible modulation schemes (see figure); the choice of a scheme for a specific system depends, in part, on whether the power-supply optical signal is steady or is modulated as described in the immediately preceding article, "Transmitting Power to Sensor Circuitry via Modulated Light" (NPO-19603).

Posted in: Briefs, TSP, Electronics & Computers, Data exchange, Electric cables, Fiber optics, Sensors and actuators, Data exchange, Electric cables, Fiber optics, Sensors and actuators

Oscillating-Flow Heat-Transfer and Pressure-Drop Test Rig

Test specimens are plugs of material representative of regenerator matrices of Stirling engines.

The figure illustrates an apparatus for measuring heat-transfer and pressure-drop characteristics of porous plug specimens in oscillating flows. The apparatus is built around an oscillating-flow test rig that was originally designed for pressure-drop (but not heat-transfer) measurements and has since been modified and refined. The flows and specimens are chosen to be representative of those encountered in the regenerators of Stirling engines.

Posted in: Briefs, TSP, Physical Sciences, Heat transfer, Heat transfer, Stirling engines, Test equipment and instrumentation

Adjacent-Pair Imaging Shearography Using Bacteriorhodopsin

In a developmental technique of real-time adjacent-pair imaging shearography, a thin film of bacteriorhodopsin is used to record shearograms in argon-laser light for immediate readout in helium/neon-laser light. Unlike conventional silver-halide-based photographic film, bacteriorhodopsin can be used as a real-time recording medium because it yields an image immediately upon exposure and is optically erasable. Bacteriorhodopsin also offers the advantage of resolution as high as 5,000 lines/mm — comparable to the resolutions of silver-halide-based films and much greater than the 80 lines/mm typical of the charge-coupled-device video cameras used heretofore in real-time shearography. Issues to be addressed in subsequent development include the difficulty of recording over a previously recorded image at the recording wavelength, the need for Fourier-transform optics for readout, the need to optimize the optics to realize the full potential for high resolution, and the relative insensitivity of bacteriorhodopsin film (about a tenth of that of silver-halide-based film).

This work was done by Colleen Fitzpatrick of Rice Systems, Inc., for Kennedy Space Center. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com under the Physical Sciences category, or circle no. 161 on the TSP Order Card in this issue to receive a copy by mail ($5 charge).

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:

Colleen Fitzpatrick
Rice Systems, Inc.
1150 Main Street, Suite C
Irvine, CA 92614
(714) 553-8768
E-mail: ricesys@prodigy.com

Refer to KSC-11838, volume and number of this NASA Tech Briefs issue, and the page number.

Posted in: Briefs, Physical Sciences, Imaging, Imaging and visualization, Lasers, Imaging, Imaging and visualization, Lasers, Bacteria, Research and development

Black-Body Evaporator Unit for a Point-Focus Solar Collector

A special coating is not necessary to ensure high solar absorptivity.

The figure illustrates a solar thermal energy system for boiling water or another liquid. The system can be used for a variety of purposes that can include drying aqueous hazardous waste, distilling pure solvent from spent solvent, purifying water by distillation, or generating steam. The principal innovative feature of this system is an absorber/evaporator unit, which is designed to absorb radiant solar energy with an effectiveness close to that of an ideal (in the black-body sense) absorber. The design is such that unlike in some other systems, it is not necessary to coat the solar-irradiated surface with a high-solar-absorptivity ("solar black") material to obtain the desired black-body characteristic. The design is also simpler than that of other absorber/evaporator units.

Posted in: Briefs, Physical Sciences, Water treatment, Solar energy, Materials properties

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