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Thermogravimetric Analysis With Laser Heating

A thin specimen is radiantly heated from both sides.Laser thermogravimetric analysis (laser TGA) is a technique that yields time-resolved data on the thermal decomposition of a specimen of a solid material exposed to a heat flux comparable to the heat flux in a typical rocket engine. Like the technique described in the preceding article, laser TGA involves heating the specimen with a continuous-wave laser beam to obtain the required high heat flux. The utility of laser TGA is not restricted to rocket-engine materials; laser TGA could be used to study high-heating-rate thermal decomposition of almost any high-temperature insulating material.

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Ultralight Balloon Systems for Exploring Uranus and Neptune

A report proposes ultralight balloon systems to carry a 10-kg payload, including scientific instruments for exploring the atmospheres of Uranus and Neptune. The system masses to be transported to those planets would be kept low by not transporting balloon-inflating gases. Each system would include an upper balloon about 4 m in diameter (0.5 kg) connected via a small port (about 0.25 m in diameter) to a lower balloon about 15 m in diameter (6.4 kg). Through an opening in the lower balloon, the balloons would become filled with low-molecular-weight atmospheric gas (which has little methane content) during initial descent through the upper atmosphere. At some point in the descent, the opening would be closed. Thereafter, the collected gas would provide buoyancy in the higher-molecular-weight atmosphere (methane content ≈2 percent) in the exploration altitude range below the methane-cloud tops, and the lower balloon (used for collection only) would be dropped. The altitude could be held constant or could be regulated by alternately venting gas and dropping ballast, as is done on balloons in the terrestrial atmosphere.

Posted in: Briefs, TSP

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Field-Reversed Magnetic Mirrors for Confinement of Plasmas

The mirror magnetic-flux density needed for confinement would be reduced. A field-reversed configuration (FRC) has been proposed for a magnetic mirror — a solenoidal electromagnet configured and operated in such a way as to effect at least partial confinement of a plasma. Magnetic mirrors had been investigated for potential use as plasma-confinement devices in nuclear fusion reactors, and had been largely rejected for that use because, as explained below, they allow too much plasma to escape. The proposed FRC is intended to increase the degree of confinement achievable by a mirror magnetic field of a given flux density and/or to reduce the flux density needed to obtain a given degree of confinement. (Whether the increase in effectiveness of confinement would be sufficient to justify the use of magnetic mirrors in fusion reactors remains to be seen.)

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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

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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.

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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

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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.

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