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

Updated Multidisciplinary Optical-System-Analysis Software

Version 5.0 of the Integrated Modeling of Optical Systems (IMOS) software has been released. A previous version was described in "Software for Multidisciplinary Analysis of Optical Systems" (NPO-20536), NASA Tech Briefs, Vol. 24, No. 11 (November 2000), page 36. In both versions, IMOS is a MATLAB computer program that provides many functions for analysis of a system represented by mathematical models of its thermal, structural, control, and/or optical aspects. IMOS is unique in making it possible to perform the entire multidisciplinary analysis in one program. The new features incorporated into version 5.0 include a capability for calculating stresses in rods and beams, a utility subprogram that generates equivalent properties of laminates, a three-dimensional-viewing subprogram, a provision for temperature-dependent heat input for thermal analyses, a provision for a simulated stiffness for the drilling degree of freedom of a plate structural element, a provision for a lumped-mass formulation for a beam, a capability to orient properties of materials with respect to plate structural elements, plate-to-acoustic and beam-to-acoustic connections for statistical energy analysis, geometric stiffnesses for plate elements (for buckling analysis), subprograms for translation from the SINDA program to IMOS and from IMOS to the NASTRAN program, and greatly improved subprograms for translation from IMOS to SINDA and from NASTRAN to IMOS.

Posted in: Briefs, TSP, Physical Sciences, Analysis methodologies, Simulation and modeling, Computer software / hardware, Computer software and hardware, Optics, Computer software / hardware, Computer software and hardware, Optics
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RVSM Certification of Dryden DC-8 Airborne Laboratory

A required pressure-altitude accuracy of ±160 ft (±49 m) has been achieved.

The NASA Dryden DC-8 Airborne Science Laboratory (see Figure 1) performs research around the globe, recently in support of the SAGE III Ozone Loss and Validation Experiment (SOLVE). This experiment operated in the North Atlantic airspace region, which is subject to reduced vertical separation minimum (RVSM) requirements (see Figure 2). These requirements allow aircraft traffic to be separated vertically by a minimum of 1,000 ft (304.8 m) at altitudes between 29,000 and 41,000 ft (between 8.84 and 12.50 km) above mean sea level, in contradistinction to the usual vertical separation of 2,000 ft (0.61 km). RVSM non-group aircraft compliance requires a pressure-altitude accuracy within ±160 ft (±49 m). RVSM allows greater traffic density while maintaining safe aircraft separation.

Posted in: Briefs, Physical Sciences, Air traffic control, Certification, Aircraft
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Apparatus Would Extract Water From the Martian Atmosphere

A report proposes an apparatus that would extract water from the atmosphere of Mars and would consume little energy in doing so. The apparatus would include a set of copper plates surrounded by a thermal shield with slots through which atmospheric gas could circulate. At night, the slots would be open and the plates would be cooled to a temperature-170 K by thermally coupling them to a radiator facing the sky. Assuming that in the nighttime Martian atmosphere at ground level, the temperature is ≤200 K and the concentration of water vapor is at or near saturation, the vapor would condense and freeze on the plates. During the day, the slots would be closed and plates would be heated by thermally coupling them to a small solar collector; this would cause the ice to melt, and the water thus produced would be collected.

Posted in: Briefs, TSP, Physical Sciences, Water, Tools and equipment
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Review of Research on Supercritical vs. Subcritical Fluids

A paper reviews theoretical and experimental research on the behaviors of supercritical fluids and, for comparison, subcritical fluids. Experiments with drops, isolated or in groups, streams, shear layers, mixing layers, jets, and sprays are tabulated and discussed as a precursor to forming a concept of fluid behavior. The physics of the supercritical and subcritical regimes is discussed, and major differences between observations in the two regimes are identified and explained.

Posted in: Briefs, Physical Sciences, Research and development, Fluid power systems
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Study of Fusion-Driven Plasma Thruster With Magnetic Nozzle

A report presents a computational study of a proposed plasma thruster for a spacecraft. The behavior of the plasma was computationally simulated by use of a mathematical model of magnetohydrodynamic flow implemented in the previously developed MACH2 computer program. To increase the accuracy of modeling of the magnetic field, MACH2 was modified by providing for an arbitrary number of current loops used to generate the applied magnetic field and by splitting the total magnetic field into applied and plasma-induced components. The results of the computational simulations contribute to understanding of the appropriate parameter regimes for the electron beam, the in-flowing working fluid, and the applied magnetic field.

Posted in: Briefs, Physical Sciences, Mathematical models, Spacecraft
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Magnetostrictively Actuated Valves for Cryosurgical Probes

Probes could be made smaller and lighter, with better regulation of temperature.

In cryosurgical probes of a type now undergoing development, the flow of coolant (typically, liquid nitrogen) would be regulated by magnetostrictively actuated needle valves controlled by use of superconductive electromagnet coils. In comparison with cryosurgical probes now in use, the developmental probes would be smaller and lighter, and would afford better regulation of temperature. This concept is made feasible by two recent advances:

Posted in: Briefs, TSP, Physical Sciences, Surgical procedures, Valves, Coolants
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Remote Sensing of Electric Fields in Clouds

Radar and radiometry would provide data on bulk orientation of ice crystals.

A proposed method for remote sensing of the electric field in a cloud that contains ice crystals would exploit the relationship between (1) the polarization-dependent radiometric or radar brightness of the cloud and (2) the average or bulk orientation of the crystals as affected by the electric field. The proposed method would complement other methods now used to measure natural electric fields in efforts to forecast lightning. A major advantage of the proposed method is that a few ground-based and/or airborne instruments could quickly survey a fairly large region of the sky.

Posted in: Briefs, TSP, Physical Sciences, Remote sensing, Remote sensing, Icing and ice detection
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Improved Infrared Imaging of Bulk Defects in CdZnTe Wafers

Images would guide the "mining" of large wafers for fabricating x-ray detectors.

An improved method of infrared imaging of bulk defects in cadmium zinc telluride (CdZnTe) wafers has been developed. The method is intended primarily to be a means of identifying those portions of large CdZnTe wafers that are suitable to be "mined" for use in fabricating focal-plane arrays of photodetectors for x-ray and g-ray astronomy. Suitable portions are those that exhibit acceptably high degrees of uniformity of x-ray spectral response. The present method of infrared imaging is useful for identifying the suitable portions because, as described below, there is a correlation between (1) x-ray spectral responses and (2) infrared images of bulk defects that affect those responses.

Posted in: Briefs, TSP, Physical Sciences, Materials identification, X-ray inspections
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Image Generators With Compact Optics

These devices can be used for head-mounted, helmet-mounted, and eyeglass-mounted displays.

Compact image generators that contain illumination sources and electronically controlled spatial light modulators have been invented. Compactness is achieved by folding of the optical paths that link the illumination sources, the spatial light modulators, and the viewing regions into which images are projected. The optical configuration of a device of this type ensures that a large proportion of the light from the illumination source is directed into the viewing region; consequently, the device is unusually energy-efficient for a display device and can, therefore, be operated at a relatively low power (possibly even battery power) for a given display brightness. By virtue of their compactness and low power consumption, these image generators are suitable for head-mounted, helmet-mounted, and eyeglass-mounted displays.

Posted in: Briefs, Physical Sciences, Exterior lighting, Energy consumption, Head-up displays, Head-up displays
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Hand-Held Instrument for Imaging Hydrogen Fires

Hydrogen fires can be seen even in full daylight.

A hand-held instrument that contains two silicon-based charge-coupled-device (CCD) video cameras (see figure) has been developed for imaging hydrogen fires. This or a similar instrument is needed because the visible light emitted by a hydrogen fire is so dim that the fire cannot be seen by the unaided human eye — at least, not in bright daylight. Like some other CCD-camera-based instruments developed previously for the same purpose, this instrument is designed to operate at infrared wavelengths where hydrogen fires appear bright, relative to solar background light. One CCD camera is called the "cloudy" camera, while the other is called the "sunny" camera, to indicate the different lighting conditions under which the cameras are designed to operate. In front of the "cloudy" camera is a long-wavelength-pass filter with a cutoff wavelength of 800 nm; during overcast, this filter blocks enough background light to make a hydrogen flame appear bright against the background. In front of the "sunny" camera there is a long-wavelength-pass filter with a cutoff wavelength of 1,100 nm; this filter blocks the solar background in the presence of full sunshine, such that a hydrogen flame is brighter than the solar background. The infrared images in the cameras are converted electronically and displayed to the instrument operator as visible images on miniature cathode-ray tubes in electronic viewfinders. A switch enables the operator to select the camera depending on the current light conditions. Optionally, both cameras and their viewfinders can be used simultaneously for binocular viewing.

Posted in: Briefs, TSP, Physical Sciences, Charge coupled devices, Optics, Charge coupled devices, Optics, Hydrogen fuel, Fire
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