Physical Sciences

Cryogenic High-Sensitivity Magnetometer

Sensitivity would be about a million times that of a flux-gate magnetometer.

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Wheel Electrometer System

Two documents describe a prototype system of electrometers for measuring electrostatic fields and electrostatic responses of soils on Mars and the Moon.

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Code for Analyzing and Designing Spacecraft Power System Radiators

GPHRAD is a computer code for analysis and design of disk or circular-sector heatrejecting radiators for spacecraft power systems. A specific application is for Stirlingcycle/linear-alternator electric-power systems coupled to radioisotope general-purpose heat sources. GPHRAD affords capabilities and options to account for thermophysical properties (thermal conductivity, density) of either metal-alloy or composite radiator materials. GPHRAD also enables specification of a heat-pipe radiator design with a radial location of the embedded heat-pipe condenser section determined numerically so that minimum radiator area is obtained. Alternatively, the user can specify a radial location of the heat-pipe condenser section for easier assembly with other components. In this case, GPHRAD determines the tradeoff cost in increased radiator area for this choice. A third option is to design a radiator without heat pipes, with heat flowing radially outward from the cylindrical cold section of the Stirling power system. A major subroutine, TSCALC, calculates an equilibrium sink temperature for a radiator, taking account of the solar absorptivity and thermal emissivity of the radiator surface, the spacecraft-to-Sun distance expressed in astronomical units (AU), the angle at which solar radiation is incident on the radiator surface, and the view factor to space of the radiator surface and the infrared absorptivity-to-emissivity ratio for planetary thermal radiation, if any. The sink temperature, along with the heat source temperature and properties of the radiator material, serve as inputs to the GPHRAD code, which then calculates dimensions of, and temperature distribution within the radiator for a required heat rejection load at given heat-rejection source temperature, such as the Stirling power system “cold” side temperature. The option to specify the disk tip-to-hub thickness ratio permits investigation of mass savings achieved by trapezoidal of parabolic tapering of the disk radiator design.

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Frozen-Plug Technique for Liquid-Oxygen Plumbing

An established plumbing technique is extended to systems other than water pipes.

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Measuring Two Key Parameters of H3 Color Centers in Diamond

These parameters are needed for the further development of diamond lasers. A method of measuring two key parameters of H3 color centers in diamond has been created as part of a continuing effort to develop tunable, continuouswave, visible lasers that would utilize diamond as the lasing medium. (An H3 color center in a diamond crystal lattice comprises two nitrogen atoms substituted for two carbon atoms bonded to a third carbon atom. H3 color centers can be induced artificially; they also occur naturally. If present in sufficient density, they impart a yellow hue.) The method may also be applicable to the corresponding parameters of other candidate lasing media. One of the parameters is the number density of color centers, which is needed for designing an efficient laser. The other parameter is an optical-absorption cross section, which, as explained below, is needed for determining the number density

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Dusty-Plasma Particle Accelerator

Microparticles and nanoparticles can be accelerated to controllable kinetic energies.

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Ferroelectric Devices Emit Charged Particles and Radiation

Compact, lightweight, low-power sources could be useful in numerous applications.

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