March 2000

Briefs : Information Technology
A Method for Designing Low-Pass FIR Digital Filters

A class of finite-impulse-response (FIR) digital filters has been developed to perform certain frequency-limiting, decimation, and differentiation (with respect to time) functions on a time series of data samples. The method is implemented by use of design equations that contain parameters that...

Briefs : Materials
Computer Code Generates Two-Dimensional Unstructured Grids

TRiangular Unstructured Mesh generator by Point insEr Tion (TRUMPET) is a computer program that generates meshes that are composed of triangular cells and are bounded by complex shapes. The bounding shapes can be singly or multiply connected two-dimensional regions. The figure depicts...

Briefs : Materials
Designing Composite Repairs and Retrofits for Infrastructure

A method of analyzing and designing laminated composite-material wraps for columns, arches, domes, and other large reinforced-concrete structures involves an extension of composite-mechanics concepts and computational techniques developed previously for the analysis and design of the...

Briefs : Materials
Software for Predicting Life of Metal-Matrix Composites

LIPS (LIFE PREDICTION SOFTWARE) is a computer program for predicting the life of an object that is made of a unidirectional-fiber/metal-matrix composite (MMC) material and that is subjected to mechanical loading along the fiber direction. The program is derived from a theory formulated to...

Briefs : Electronics & Computers
Security System Based on Bragg Gratings in an Optical Fiber

The figure schematically illustrates an optoelectronic security system in which binary information on the identity of a person or object is encoded in Bragg gratings in an optical fiber. This is not the first optoelectronic security system based on fiber-optic Bragg gratings, but it is...

Briefs : Electronics & Computers
Higher-Resolution Optoelectronic Shaft-Angle Encoder

The apparatus shown schematically in the figure is an optoelectronic shaft-angle encoder that measures absolute angles with high resolution. This encoder is an improved version of the apparatus described in "High-Resolution Optoelectronic Shaft-Angle Encoder" (GSC-13543), Laser Tech Briefs,...

Briefs : Electronics & Computers
High-Power Laser Illuminator

A laser illuminator system has been developed for use in automated tracking of objects. In its original application, the system illuminates a 5° conical region expected to contain a small satellite at a distance up to 750 m from the space shuttle. If the satellite comes within this region, then a receiving...

Briefs : Electronics & Computers
Communication Controller Board for a Wind-Tunnel Model

A communication controller circuit for a wind-tunnel model is undergoing development. The circuit is intended to serve as part of a highly miniaturized, distributed, modular electronic analog/digital data-acquisition system that would be installed inside a wind-tunnel model (see Figure 1)....

Briefs : Software
Software for Simulating Progressive Fracture in Braided PMCs

GENOA-PFA is a commercial version of the Composite Durability Structural Analysis (CODSTRAN) computer program, which simulates the progression of damage ultimately leading to fracture in Polymer-Matrix Composite (PMC) material structures under various loading and environmental...

Briefs : Materials
Molecular-Sieve Type 3Å

The term "Molecular-Sieve Type 3Å" denotes a clay-based, zeolite material that revolutionizes a fluid-purification process by removing trace water and iron from nitrogen tetroxide/nitric oxide (MON-3) mixtures used as oxidizer components of spacecraft propellants. Older processes of this type removed only water or iron...

Briefs : Materials
Composite Graphite Anodes Containing Cyclic Ether Additives

Scientists have developed a type of composite graphite anode that will benefit the U.S. space program and private industry by increasing the rechargeability of lithium-ion batteries. Rechargeable lithium-ion batteries, which are used on the space shuttle and Space Station, are also used...

Briefs : Materials
Polypyrrole and Polyaniline Doped With Lignosulfonic Acid

Experiments have shown that electrically conductive polymers with water-soluble fractions can be synthesized by polymerization of pyrrole or aniline in the presence of lignosulfonic acid, which is a polymeric acid that can be derived relatively easily from the spent sulfite liquor...

Briefs : Mechanical & Fluid Systems
Leak-Free Pressurizing Valve

A leak-free valve has been proposed as a more reliable, less expensive, adaptable alternative to a one-time-opening, pyrotechnically actuated valve (pyrovalve). In the original intended application, the pyrovalve serves, before it is actuated, to isolate a pressurant gas (helium) from a propellant fluid aboard a...

Briefs : Mechanical & Fluid Systems
Afterbody Cushions for Instrumented Penetrator Projectiles

Pneumatic cushions have been proposed for protecting the afterbodies of two-body instrumented soil-penetrator projectiles. These cushions would be, essentially, doughnut-shaped miniature versions of automotive airbags, designed for rapid inflation upon impact.

Briefs : Mechanical & Fluid Systems
Ultrasonic Measurement of Bending of Bolts
Ultrasonic Measurement of Bending of Bolts

Work performed at Johnson Space Center has brought about a major improvement in the means for measuring the bending that occurs whenever stress is applied to a bolted joint. This major improvement...

Ultrasonic Measurement of Bending of Bolts
Briefs : Manufacturing & Prototyping
Improvements in Rapid Prototyping

Several improvements have been proposed for the fabrication process known as "rapid prototyping." In this process, a model or prototype of a solid object is built up by controlled ejection of molten polymeric material through programmed orifices to form patterned layers. The second layer is deposited on top of...

Briefs : Physical Sciences
Efficient Ionizer for an Array of Mass Spectrometers

An electron-beam ionizer has been designed to deliver ions to the entrance apertures of nine miniature quadrupole mass spectrometers in an array. A similar electron-beam ionizer could also be designed for an array of more or fewer mass spectrometers. Principal issues that had to be addressed...

Briefs : Physical Sciences
Analyzing Rocket Exhaust by Atomic-Absorption Spectroscopy

A computer-controlled instrumentation system has been developed for use in measuring concentrations of various atomic species in the exhaust gases of a space-shuttle main engine on a test stand. The system is based on established techniques of atomic-absorption spectroscopy (AAS)....

Briefs : Physical Sciences
Adjustable Optics for Spectral Analysis of Rocket Exhaust

The figure presents additional information on the optics of the atomic-absorption-spectroscopy (AAS) system described in the preceding article. The optics include (1) a periscopic optical subsystem for access to a measurement optical axis in a plane different from that of the input and...

Briefs : Physical Sciences
Thickness-Independent Ultrasonic Characterization of Tubes

A technique for ultrasonic characterization of plates has been extended to tubes and curved structures in general. In this technique, as explained in more detail below, one performs measurements that yield a thickness-independent value of local through-the-thickness speed of sound in a...

Briefs : Physical Sciences
Detecting Metal Ions by Voltammetry Using Diamond Electrodes

Experiments have demonstrated the feasibility of detecting multiple species of toxic metal ions and other ions of interest dissolved in water, by means of voltammetry with electrically conductive artificial diamond electrodes. Diamond is attractive as an electrode material because it...

Briefs : Information Technology
Preconditioning the Helmholtz Equation for a 2-D Duct

A preconditioning technique has been developed for numerical solution of the Helmholtz equation as applied to the steady-state propagation of sound in a semi-infinite, two-dimensional (2-D) rigid duct. As explained below, the technique involves the use of two pseudo-time parameters in a...

Briefs : Information Technology
Analytic Technique for Separation of Cochannel FM Signals

A digital processing technique for separating two cochannel frequency-modulation (FM) signals involves a partial algebraic solution that gives the phases of the two signals to within one of two possibilities, plus the use of a two-state trellis algorithm to trace the most likely correct...

Briefs : Materials
Tribological Characterization of Solid Surfaces

Reports labeled as chapters 2, 3, 4, 7, 8, 9, and 10 of a NASA technical memorandum that addresses topics in tribology have been compiled into a document that emphasizes those aspects of the subject matter that pertain to chemical-vapor-deposited (CVD) diamond and diamond-like films. The...

Briefs : Physical Sciences
Small Balloons for Local Aerial Exploration of Mars

A report proposes the use of lightweight balloon-borne instrumentation systems for exploration in the vicinity of a lander on the surface of Mars. Each system would comprise instrumentation with a mass of about 0.2 kg and a balloon with a mass of about 0.8 kg and volume of about 50...

Briefs : Mechanical & Fluid Systems
Using Electromagnetic Drag on Tethers To De-Orbit Spacecraft

Two papers propose the use of electrically conductive tethers to remove spent or dysfunctional spacecraft from orbit around the Earth in order to reduce the hazard of orbital debris. In comparison with onboard rockets, these tethers would be more cost-effective, more reliable, and...

Briefs : Physical Sciences
Apparatus and Technique for Measuring Distance Between Axles

An optoelectronic apparatus and a technique for its operation have been developed to facilitate and accelerate the measurement of distances of the order of tens of feet to within error limits of about ±1/8 in. (about 3 mm). In the original application, the distance to be measured [≈...

Briefs : Electronics & Computers
Miniature, Low-Power, Digital, Wireless Electronic Camera

A portable, battery-powered camera unit contains a programmable digital camera that is implemented on a single chip utilizing active-pixel-sensor (APS) technology, plus circuitry for digital radio communication between the camera and a base station. A laboratory-bench-top version of this...

Briefs : Materials
Improved Accelerated Corrosion Testing of Zinc-Rich Primers

An improved method of accelerated testing reduces the time needed to analyze the abilities of zinc-rich primers to protect steel substrates against corrosion in a seacoast environment. In this method, specimens are placed in racks where they are exposed to the environment. From time to...

Briefs : Photonics/Optics
Development of Multimode-Optical-Fiber Imaging Probe

A developmental electro-optical system would enable remote real-time viewing of a scene through a multimode optical fiber, as though the fiber were a conventional image-transmitting optic like a lens or prism. The system is intended to be a prototype of fiber-optic imaging probes that could...

Briefs : Manufacturing & Prototyping
Fabricating Small Apertures in Silicon-on-Insulator Wafers

Precise small apertures for a variety of optical applications can be formed in silicon-on-insulator (SOI) wafers by use of a photolithographic process developed specifically for the purpose. In comparison with the formation of apertures in standard silicon wafers by previously developed...

Briefs : Physical Sciences
Cancellation of Laser Noise in an Unequal-Arm Interferometer

A method of processing phase measurements in an unequal-arm laser Michelson interferometer makes it possible to detect phase effects much smaller than the laser phase noise. In the original application for which the method has been proposed, the interferometer, used to detect...

Briefs : Photonics/Optics
Tunable, Single-Frequency, Fiber Fabry-Perot VCSELs

The figure depicts several aspects of a unique type of vertical-cavity surface-emitting lasers (VCSELs) that incorporate fiber Fabry-Perot (FFP) optical cavities. These lasers have been designed to be compact, compatible with optical fibers, capable of single-frequency operation, and tunable....

Briefs : Photonics/Optics
Reducing the Volume of a Holographic Data-Storage System

The size of a holographic data-storage system could be reduced by a proposed design modification that calls for replacement and repositioning of some optical components and the use of some of the components to perform dual functions. The modification would enable a substantial decrease in...

Briefs : Photonics/Optics
Filterless Si-Based Ultraviolet-Selective Photodetectors

Monolithic semiconductor photodiodes that discriminate against infrared and visible light and that can be tailored to detect ultraviolet light in selected wavelength bands have been invented. These devices could serve as ultraviolet sensors in such instruments as hydrogen- and...

Briefs : Photonics/Optics
Generating Synchronized WDM Pulses in a Nonlinear Optical Fiber

Pulse shepherding (defined below) can be exploited to impress synchronized amplitude-modulation pulses, with durations of the order of picoseconds, onto beams of light with different wavelengths that propagate together along a single-mode nonlinear optical fiber. This is...

Briefs : Photonics/Optics
Improved Cross-Correlation Dynamic-Light-Scattering Method

A dynamic-light-scattering (DLS) method that reduces undesired contributions from multiply scattered photons has been invented. The method involves, among other things, cross-correlation processing of the outputs of two photodetectors aimed along intersecting, nearly parallel lines of...

Briefs : Photonics/Optics
Alloy Casting Produces New Mirror Technology

Under a Phase 1 Small Business Technology Transfer (STTR) award of $99,000 with Goddard Space Flight Center, Advanced Optical Systems Inc. (AOS) has produced a 13.5-kg/m2 6-in.-diameter mirror flat to 1 wave peak to valley (0.2 wave RMS) with no heat treatment. Many known techniques, such...