Physical Sciences

Graded-index-of- refraction dielectric optical microresonators have been proposed as a superior alternative to prior dielectric optical microresonators, which include microspheres (described in several prior NASA Tech Briefs articles) and microtori wherein electromagnetic waves propagate...

Two documents discuss improvements in traps for removing noncondensable gases (e.g., air) from heat-transfer liquids (e.g., water) in spacecraft cooling systems. Noncondensable gases must be removed because they can interfere with operation. A typical trap includes a cylindrical hydrophobic...

Miniaturized hydrogen- and hydrocarbon- gas sensors, heretofore often consisting of Schottky diodes based on catalytic metal in contact with SiC, can be improved by incorporating palladium oxide (PdOx, where 0≤x≤1) between the catalytic metal and the SiC.

A document discusses a proposal to incorporate holographic optical elements into solar photon thrusters (SPTs). First suggested in 1990, SPTs would be systems of multiple reflective, emissive, and absorptive surfaces (solar sails) that would be attached to spacecraft orbiting the Earth to derive small propulsive...

A report presents a concept for an instrument to be flown in outer space, where it would detect dust particles — especially those associated with comets. The instrument would include a flat plate that would intercept the dust particles. The anticipated spacecraft/dust-particle relative speeds...

A NOBOSS stands in contrast to compressed- gas and cryogenic air-supply systems. Compressed-gas systems necessarily include massive tanks that can hold only relatively small amounts of gases. Alternatively, gases can be stored compactly in greater quantities and at low pressures when they are...

A straightforward measurement technique provides for correction of thermal-electromotive- force (thermal-EMF) errors introduced by temperature gradients along the pins of non-thermocouple- alloy hermetic feedthrough connectors for thermocouple extension wires that must pass through bulkheads....

A method of compensating for or minimizing phase differences between orthogonal polarizations of light reflected from metallic mirrors at oblique incidence, as, for example, from weakly curved mirrors, is undergoing development. The method is intended to satisfy a need to maintain precise...

Electrolytes comprising LiPF6 dissolved at a concentration of 1.0 M in five different solvent mixtures of alkyl carbonates have been found to afford improved performance in rechargeable lithium-ion electrochemical cells at temperatures as low as -70° C. These and other electrolytes have...

A document proposes the development of hot-electron photon counters (HEPCs) for detecting terahertz photons in spaceborne far-infrared astronomical instruments. These would be superconducting-transition-edge devices: they would contain superconducting bridges that would have such low heat capacities that...

A recently developed data-compression method is an adaptive technique for coding quantized wavelet-transformed data, nominally as part of a complete image-data compressor. Unlike some other approaches, this method admits a simple implementation and does not rely on the use of large code tables.

Stroboscopic interferometry is a technique for measuring the modes of vibration of mirrors that are lightweight and, therefore, unavoidably flexible. The technique was conceived especially for modal characterization of lightweight focusing mirror segments to be deployed in outer space;...