Tech Briefs

Program for Computing Dynamics of Multiple Bodies

Symbolic Generator-Based Efficient Multibody Dynamics Algorithm (SOMBAT) is a program that enables speedy and accurate computations that solve equations of motion of multiple bodies. Originally intended for space-based applications (i.e., solving equations for the dynamics of a cluster of flexible bodies in orbit in real time), SOMBAT can also be applied in designing drugs, enhancing and otherwise processing images, the automotive industry, and robotics. It can also be used by the Department of Defense. Its greatest strength is its ability to reduce computation time without sacrificing accuracy. Unlike programs modeled on n3 algorithms, SOMBAT accrues time savings overruns while satisfying short-turnaround requirements. Moreover, and vitally for the U.S. Space Program, the open and expandable format of SOMBAT will enable the tailoring of this program to upgrade add-on systems for new International Space Station (ISS) modules.

Posted in: Briefs, Mechanical Components, Mechanics, Mathematical models, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware, Reliability, Reliability

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 can be adjusted to obtain the desired functionality while limiting such undesired effects as aliasing and gain ripple. The original application is processing of a time series of raw range data from the proposed Gravity Recovery and Climate Experiment (GRACE), in which microwave phase tracking between two small spacecraft orbiting the Earth would yield the time-tagged raw range data, which would be processed to extract information on the structure of the gravitational field of the Earth. The method is general enough to be applicable in other situations that involve similar signal-processing requirements.

Posted in: Briefs, TSP, Information Sciences, Mathematical analysis, Measurements, Spacecraft

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 two examples of meshes that can be generated by use of TRUMPET.

Posted in: Briefs, Materials, Mathematical models, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware

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 composite materials only. As used thus far, "composite materials" denotes polymeric matrices reinforced with polymeric or nonpolymeric fibers — e.g., epoxy reinforced with glass fibers. Wraps made of composite materials can be applied to reinforced concrete structures to repair them or as retrofits for reinforcement against loads that are expected to exceed original design loads.

Posted in: Briefs, TSP, Materials, Coatings Colorants and Finishes, Coatings, colorants, and finishes, Composite materials, Fibers, Construction vehicles and equipment

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 be consistent with the experimental observation that progressive fiber fracture (more precisely, successive fractures of different fibers) is a dominant damage mechanism that leads to failure in MMCs. This theory is fundamentally different from other theories in which the effects of broken fibers are represented by artificially reducing the moduli of the fibers. In the present theory, progressive fiber fracture is addressed via a fiber-fracture criterion based on a statistical distribution of fiber strength.

Posted in: Briefs, TSP, Materials, Statistical analysis, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware, Life cycle analysis, Composite materials, Fibers, Metals

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 the first in which such gratings constitute the basis of a key or an identification tag.

Posted in: Briefs, TSP, Electronics & Computers, Cryptography, Fiber optics, Security systems, Cryptography, Fiber optics, Security systems, Identification

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, Vol. 2, No. 2, (Spring, 1994), page 32.

Posted in: Briefs, TSP, Electronics & Computers, Measurements, Lasers, Lasers, Test equipment and instrumentation

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 optoelectronic system aboard the space shuttle actively tracks the satellite by locking onto the laser illumination reflected by small mirrors on the satellite. The laser illuminator system could be adapted to other outer-space and terrestrial applications that involve illumination with or without tracking, or could be used as a beacon on a moving platform for tracking by an optoelectronic system located on another moving or stationary platform.

Posted in: Briefs, TSP, Electronics & Computers, Mirrors, Lasers, Surveillance, Lasers, Surveillance, Reusable launch vehicles and shuttles, Satellites

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). The data-acquisition system would include pressure, temperature, angle, shear-stress, and other sensors plus analog signal-conditioning modules in clusters of as many as eight sensors. The sensors and signal-conditioning modules in each cluster would be connected to a data-acquisition-system (DAS) module, which would contain additional analog signal-conditioning circuits and analog-to-digital converters. Each DAS module, in turn, would be connected to the communication controller, which would effect all digital control and data communications (1) among the sensor modules and (2) between the sensor modules and a remote host computer.

Posted in: Briefs, TSP, Electronics & Computers, Architecture, Data acquisition and handling, Integrated circuits, Sensors and actuators, Architecture, Data acquisition and handling, Integrated circuits, Sensors and actuators, Wind tunnel tests

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 conditions. GENOA-PFA offers a number of capabilities beyond those of programs developed previously for the same purpose; these capabilities make GENOA-PFA preferable for use in analyzing the durability and damage tolerance of complex PMC structures in which the fiber reinforcements are in the forms of two- and even three-dimensional weaves and braids.

Posted in: Briefs, TSP, Software, Computer simulation, Failure analysis, Composite materials, Fibers, Polymers

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