Tech Briefs

Algorithms for Haptic Rendering of 3D Objects

Tactual displays provide the sensations of touching computationally simulated objects. Algorithms have been developed to provide haptic rendering of three-dimensional (3D) objects in virtual (that is, computationally simulated) environments. The goal of haptic rendering is to generate tactual displays of the shapes, hardnesses, surface textures, and frictional properties of 3D objects in real time. Haptic rendering is a major element of the emerging field of computer haptics, which invites comparison with computer graphics. We have already seen various applications of computer haptics in the areas of medicine (surgical simulation, telemedicine, haptic user interfaces for blind people, and rehabilitation of patients with neurological disorders), entertainment (3D painting, character animation, morphing, and sculpting), mechanical design (path planning and assembly sequencing), and scientific visualization (geophysical data analysis and molecular manipulation).

Posted in: Briefs, TSP, Electronics & Computers

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Prognostics Methodology for Complex Systems

Automatic method to detect and react to complex degradation and incipient faults. An automatic method to schedule maintenance and repair of complex systems is produced based on a computational structure called the Informed Maintenance Grid (IMG). This method provides solutions to the two fundamental problems in autonomic logistics: (1) unambiguous detection of deterioration or impending loss of function and (2) determination of the time remaining to perform maintenance or other corrective action based upon information from the system. The IMG provides a health determination over the medium-to-long-term operation of the system, from one or more days to years of study. The IMG is especially applicable to spacecraft and both piloted and autonomous aircraft, or industrial control processes.

Posted in: Briefs, TSP

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Shields for Enhanced Protection Against High-Speed Debris

A report describes improvements over the conventional Whipple shield (two thin, spaced aluminum walls) for protecting spacecraft against high-speed impacts of orbiting debris. The debris in question arises mainly from breakup of older spacecraft. The improved shields include exterior "bumper" layers composed of hybrid fabrics woven from combinations of ceramic fibers and high-density metallic wires or, alternatively, completely metallic outer layers composed of high-strength steel or copper wires. These shields are designed to be light in weight, yet capable of protecting against orbital debris with mass densities up to about 9 g/cm3, without generating damaging secondary debris particles. As yet another design option, improved shields can include sparsely distributed wires made of shape memory metals that can be thermally activated from compact storage containers to form shields of predetermined shape upon arrival in orbit. The improved shields could also be used to augment shields installed previously.

Posted in: Briefs, TSP

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Transparent Metal-Salt-Filled Polymeric Radiation Shields

These shields offer advantages over ones made from lead foil or leaded glass. The Quantitative and Qualitative Parameters in this table are those of three shields that give equivalent protection against ionizing radiation. "COR-RA" (colorless atomic oxygen resistant — radiation shield) is the name of a transparent polymeric material filled with x-ray-absorbing salts of lead, bismuth, cesium, and thorium. COR-RA is suitable for use in shielding personnel against bremsstrahlung radiation from electron-beam welding and industrial and medical x-ray equipment. In comparison with lead- foil and leaded- glass shields that give equivalent protection against x-rays (see table), COR-RA shields are mechanically more durable.

Posted in: Briefs, TSP

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Meshed-Pumpkin Super-Pressure Balloon Design

Masses of long-life, high-altitude balloons could be decreased substantially. An improved, lightweight design has been proposed for super-pressure balloons used to carry scientific instruments at high altitudes in the atmosphere of Earth for times as long as 100 days. [A super- pressure balloon is one in which the pressure of the buoyant gas (typically, helium) is kept somewhat above ambient pressure in order to maintain approximately constant density and thereby regulate the altitude.] The proposed design, called "meshed pumpkin," incorporates the basic concept of the pumpkin design, which is so named because of its appearance (see figure). The pumpkin design entails less weight than does a spherical design, and the meshed-pumpkin design would reduce weight further.

Posted in: Briefs, TSP

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Corrosion Inhibitors as Penetrant Dyes for Radiography

These substances now have dual uses. A Weld Crack Is More Clearly Visible in a neutron radiograph made after treatment with an LVCI. Liquid/vapor-phase corrosion inhibitors (LVCIs) have been found to be additionally useful as penetrant dyes for neutron radiography (and perhaps also x-radiography). Enhancement of radiographic contrasts by use of LVCIs can reveal cracks, corrosion, and other defects that may be undetectable by ultrasonic inspection, that are hidden from direct optical inspection, and/or that are difficult or impossible to detect in radiographs made without dyes.

Posted in: Materials, Briefs

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Explicit Pore Pressure Material Model in Carbon-Cloth Phenolic

The explicit model predicts some quantities that a prior implicit model cannot. An explicit material model that uses predicted pressure in the pores of a carbon-cloth phenolic (CCP) composite has been developed. This model is intended to be used within a finite-element model to predict phenomena specific to CCP components of solid-fuel-rocket nozzles subjected to high operating temperatures and to mechanical stresses that can be great enough to cause structural failures. Phenomena that can be predicted with the help of this model include failures of specimens in restrained-thermal-growth (RTG) tests, pocketing erosion, and ply lifting. Heretofore, an implicit formulation has been used to model the pore pressure. The differences between explicit and implicit models can be illustrated with the theoretical solution for stress and strain in an RTG test. The equations for the explicit case are:

Posted in: Briefs

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