Tech Briefs

Making a Metal-Lined Composite-Overwrapped Pressure Vessel

The metal liner reduces loss of gas by diffusion without adding much weight.

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High-Temperature, High-Load-Capacity Radial Magnetic Bearing

Speed and temperature limits of rollingelement bearings can be exceeded.

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Fabrication of Spherical Reflectors in Outer Space

Process takes advantage of vacuum.

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Relative-Motion Sensors and Actuators for Two Optical Tables

Relative motions can be suppressed or imposed on demand. Optoelectronic sensors and magnetic actuators have been developed as parts of a system for controlling the relative position and attitude of two massive optical tables that float on separate standard air suspensions that attenuate ground vibrations. In the specific application for which these sensors and actuators were developed, one of the optical tables holds an optical system that mimics distant stars, while the other optical table holds a test article that simulates a spaceborne stellar interferometer that would be used to observe the stars.

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Improved Position Sensor for Feedback Control of Levitation

In this application, an incandescent light bulb is preferable to a laser. An improved optoelectronic apparatus has been developed to provide the position feedback needed for controlling the levitation subsystem of a containerless processing system. As explained below, the advantage of this apparatus over prior optoelectronic apparatuses that have served this purpose stems from the use of an incandescent lamp, instead of a laser, to illuminate the levitated object.

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Diffusion-Cooled Tantalum Hot-Electron Bolometer Mixers

Lower TC s should translate to lower noise and lower required local-oscillator power. A batch of experimental diffusion-cooled hot-electron bolometers (HEBs), suitable for use as mixers having input frequencies in the terahertz range and output frequencies up to about a gigahertz, exploit the superconducting/normal-conducting transition in a thin strip of tantalum. The design and operation of these HEB mixers are based on mostly the same principles as those of a prior HEB mixer that exploited the superconducting/ normal-conducting transition in a thin strip of niobium and that was described in “Diffusion-Cooled Hot-Electron Bolometer Mixer” (NPO-19719), NASA Tech Briefs, Vol. 21, No. 1 (January 1997), page 12a.

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Electron-Spin Filters Based on the Rashba Effect

Filters would be made from nonmagnetic semiconductors and operated without applied magnetic fields. Semiconductor electron-spin filters of a proposed type would be based on the Rashba effect, which is described briefly below. Electron-spin filters — more precisely, sources of spin-polarized electron currents — have been sought for research on, and development of, the emerging technological discipline of spintronics (spin-based electronics). There have been a number of successful demonstrations of injection of spin-polarized electrons from diluted magnetic semiconductors and from ferromagnetic metals into nonmagnetic semiconductors. In contrast, a device according to the proposal would be made from nonmagnetic semiconductor materials and would function without an applied magnetic field.

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