Special Coverage

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
Computer Chips Calculate and Store in an Integrated Unit
Electron-to-Photon Communication for Quantum Computing

Detecting Negative Obstacles by Use of Radar

Changes in diffraction and reflection would be used to detect abrupt downslopes.

Because such wavelengths are comparable to the characteristic dimensions of terrain features associated with negative hazards, a significant amount of diffraction would occur at such features. In effect, the diffraction would afford a limited ability to see corners and to see around corners. Hence, the system might utilize diffraction to detect corners associated with negative obstacles. At the time of reporting the information for this article, preliminary analyses of diffraction at simple negative obstacles had been performed, but an explicit description of how the system would utilize diffraction was not available.

Posted in: Briefs, TSP, Electronics & Computers, Radar, Terrain
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Simulator for Testing Spacecraft Separation Devices

A report describes the main features of a system for testing pyrotechnic and mechanical devices used to separate spacecraft and modules of spacecraft during flight. The system includes a spacecraft simulator [also denoted a large mobility base (LMB)] equipped with air thrusters, sensors, and data-acquisition equipment. The spacecraft simulator floats on air bearings over an epoxy-covered concrete floor. This free-flotation arrangement enables simulation of motion in outer space in three degrees of freedom: translation along two orthogonal horizontal axes and rotation about a vertical axis. The system also includes a static stand. In one application, the system was used to test a boltretraction system (BRS) intended for separation of the lifting-body and deorbitpropulsion stages of the X-38 spacecraft. The LMB was connected via the BRS to the static stand, then pyrotechnic devices that actuate the BRS were fired. The separation distance and acceleration were measured. The report cites a document, not yet published at the time of reporting the information for this article, that is said to present additional detailed information.

Posted in: Briefs, Test & Measurement, Test equipment and instrumentation, Spacecraft
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Apparatus for Hot Impact Testing of Material Specimens

It is not necessary to cool and reheat the furnace between tests.

An apparatus for positioning and holding material specimens is a major subsystem of a system for impact testing of the specimens at temperatures up to 1,500 °C. This apparatus and the rest of the system are designed especially for hot impact testing of advanced ceramics, composites, and coating materials.

Posted in: Briefs, Test & Measurement, Ceramics, Coatings, colorants, and finishes, Composite materials, Test equipment and instrumentation
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Instrument for Aircraft-Icing and Cloud- Physics Measurements

Data on cloud water content are deduced from hot-wire power levels.

The figure shows a compact, rugged, simple sensor head that is part of an instrumentation system for making measurements to characterize the severity of aircraft-icing conditions and/or to perform research on cloud physics. The quantities that are calculated from measurement data acquired by this system and that are used to quantify the severity of icing conditions include sizes of cloud water drops, cloud liquid water content (LWC), cloud ice water content (IWC), and cloud total water content (TWC).

Posted in: Briefs, Test & Measurement, Measurements, Icing and ice detection, Test equipment and instrumentation
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Improved Apparatus for Testing Monoball Bearings

Automated tests can be performed over wide ranges of conditions.

A desk-sized apparatus for testing monoball bearings and their lubricants offers advantages, relative to prior such apparatuses, of (1) a greater degree of automation and (2) capability of operation under wider and more realistic ranges of test conditions. The ranges of attainable test conditions include load from 100 to >50,000 lb (445 to >2.22 × 105 N), resisting torque up to 30,000 lb-in. (≈3,390 N-m), oscillating rotation through an angle as large as 280°, and oscillation frequency from 0 to 6 Hz. With addition of some components and without major modification of the apparatus, it is also possible to perform tests under environmental conditions that include temperature from −320 to 1,000 °F (−196 to +538 °C), relative humidity from 0 to 100 percent, and either air at ambient pressure, high vacuum, or an atmosphere of monatomic oxygen.

Posted in: Briefs, Test & Measurement, Bearings, Test equipment and instrumentation
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PixelLearn

PixelLearn is an integrated user-interface computer program for classifying pixels in scientific images. Heretofore, training a machine-learning algorithm to classify pixels in images has been tedious and difficult. PixelLearn provides a graphical user interface that makes it faster and more intuitive, leading to more interactive exploration of image data sets. PixelLearn also provides image-enhancement controls to make it easier to see subtle details in images. PixelLearn opens images or sets of images in a variety of common scientific file formats and enables the user to interact with several supervised or unsupervised machine-learning pixel-classifying algorithms while the user continues to browse through the images. The machinelearning algorithms in PixelLearn use advanced clustering and classification methods that enable accuracy much higher than is achievable by most other software previously available for this purpose. PixelLearn is written in portable C++ and runs natively on computers running Linux, Windows, or Mac OS X.

Posted in: Briefs, TSP, Software
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New Software for Predicting Charging of Spacecraft

The NASA/Air Force Spacecraft Charging System Analyzer Program (Nascap-2K) is a comprehensive update, revision, and extension of several NASA and Air Force codes for predicting electrical charging of spacecraft. Nascap-2K integrates the capabilities and models included in four independent programs: NASCAP/LEO for low-Earth orbits, NASCAP/GEO for geosynchronous orbits, POLAR for auroral charging in polar orbits, and DynaPAC (Dynamic Plasma Analysis Code) for time-dependent plasma interactions. While each of the earlier codes works well for the range of problems for which it was designed, by today’s standards these codes are difficult to learn, cumbersome to use, and overly restrictive in their geometric modeling capabilities. Nascap-2K incorporates these models into a single software package that includes spacecraft surface modeling, spatial gridding, environmental specifications, calculating scripting, and post-processing analysis and visualization. The provided material properties database includes values from earlier programs as well as values from recent measurements. Development of Nascap-2K continues with future capabilities to include interactions with dense plasma such as those produced by electric propulsion.

Posted in: Briefs, Software, Computer software and hardware, Vehicle charging, Prognostics, Spacecraft
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Conversion Between Osculating and Mean Orbital Elements

Osculating/Mean Orbital Element Conversion (C version) (OSMEANC) is a C-language computer program that performs precise conversions between osculating and mean classical orbital elements. OSMEANC can be used for precise design of spacecraft missions and maneuvers and precise calculation of planetary orbits. The program accounts for the full complexity of gravitational fields, including aspherical and third-body effects. In comparison with prior software used for the same purposes, OSMEANC offers greater accuracy in conversion: By virtue of inclusion of high-order gravitational and third-body effects, variations in semimajor axes are calculated to meter-level accuracy. OSMEANC is delivered as a callable shared library. It can be built for any platform with a C compiler. The user interface is via a Python-language wrapper script that can be replaced by the user. OSMEANC is mature and is the product of a significant upgrade from a Fortran version that has been in use since 1991.

Posted in: Briefs, TSP, Software, Mathematical models, Computer software and hardware, Performance upgrades
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Generating a 2D Representation of a Complex Data Structure

A computer program, designed to assist in the development and debugging of other software, generates a two-dimensional (2D) representation of a possibly complex ndimensional (where n is an integer >2) data structure or abstract rank-n object in that other software. The nature of the 2D representation is such that it can be displayed on a non-graphical output device and distributed by non-graphical means. The purpose served by this representation is to assist the user in visualizing and understanding the complex data structure or arbitrarily dimensioned object. This is the only known program that enables a programmer to map an n-dimensional data structure to a flat 2D space. This program does not depend upon the hardware characteristics of a particular output device, and can be executed on a variety of computers from different manufacturers. It can be distributed in source-code or binary-code form. It requires a Lisp compiler. It has no specific memory requirements and depends upon the other software with which it is used and application programs running in it. This software is implemented as a library that is called by, and becomes folded into, the developmental other software.

Posted in: Briefs, TSP, Software, CAD, CAM, and CAE, Computer software and hardware, Performance tests
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Cryogenic Pound Circuits for Cryogenic Sapphire Oscillators

Two modern cryogenic variants of the Pound circuit have been devised to increase the frequency stability of microwave oscillators that include cryogenic sapphire-filled cavity resonators. Invented in the 1940s and named after its inventor (R. V. Pound), the original Pound circuit is a microwave frequency discriminator that provides feedback to stabilize a voltage-controlled microwave oscillator with respect to an associated cavity resonator. Heretofore, Pound circuits used in conjunction with cryogenic resonators have included room-temperature electronic components coupled to the resonators via such inter-connections as coaxial cables. The thermo mechanical instabilities of these inter-connections give rise to frequency instabilities. In a cryogenic Pound circuit of the present improved type, all of the active electronic components, the inter-connections among them, and the inter-connections between them and the resonator reside in the cryogenic environment along with the resonator and, hence, are thermo-mechanically stabilized to a large degree. Hence, further, frequency instabilities are correspondingly reduced.

Posted in: Briefs, TSP, Semiconductors & ICs, Electronic equipment, Integrated circuits, Radar
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