Physical Sciences

Assessing Energetic-Ion Effects Using Energetic Protons Only

Two reports describe a method of assessing the susceptibility of digital electronic equipment to upsets (bit errors) caused by impingement of energetic ions (both protons and heavier ions) in outer space. The method, which is applicable at the single-component, circuit-board, box, and totalsystem levels, involves terrestrial testing by use of 200-MeV protons only. Unlike in a prior method that involves lower-energy heavier ions, one need not place a test article in a vacuum or remove it from its normal packaging. One of the reports discusses the origin of the present method, describes the procedure for exposing various parts of a test article to an energetic-proton beam and analyzing the resulting test data to obtain radiation susceptibilities, and summarizes the experience gained by use of the method since its inception in the year 1995. The other report discusses mathematical modeling and development of software to estimate the effects of energetic heavier ions on the basis of testing by use of energetic protons only. Among the conclusions reached in this development is that the heavy-ion error rate can be estimated as an orbital-altitudedependent fraction of the proton error rate.

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Slab-Waveguide Interferometer for Sensing Ammonia in Wet Air

Ammonia changes the pattern of interference between TM0 and TM1 waveguide modes. The figure depicts a single-arm, slabwave- guide interferometer that has been demonstrated to be useable as a means of sensing ammonia in wet air. The slabwaveguide portion of this device comprises a 2-μm-thick film of poly(methyl methacrylate) [PMMA] on a substrate of fused quartz. The PMMA layer acts as a waveguide because its index of refraction is greater than the indices of refraction of both the fused quartz on one side and the ambient air on the other side. The PMMA film is doped with bromocresol purple — an indicator dye that causes the index of refraction of the film to vary with the amount of ammonia that diffuses into the film from the ambient air. The remaining basic features of design and operation, as described below, are devoted to enhancing and measuring the change in an optical phase difference attributable to the change in the index of refraction and thus to the presence of ammonia.

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Aircraft Anti-Icing Heaters Made From Expanded Graphite

These heaters could be lightweight and inexpensive enough to be practical for small aircraft. Improved electrical resistance heaters for preventing the accum- ulation of ice on aircraft surfaces are undergoing development. The primary intended market for these heaters is that of small single- and twin-engine airplanes and helicopters, most of which have not been equipped with anti-icing heaters because the weights and costs of such heaters have made them impractical. The improved heaters are expected to add very little to the weights of aircraft and, when massproduced, to cost about half as much as do anti-icing systems of prior design. The aircraft could be equipped with high-output alternators to supply the additional electric power needed for the heaters.

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Regulating Pressure-Volume Control of a Gas Blanketing Liquid R-124

A system for storing and circulating a refrigerant liquid [R- 124 (chloro- tetrafluoroethane)] includes a reservoir and a subsystem that regulates the pressure of nitrogen gas in the head space of the reservoir. The purpose of the pressurization is to prevent cavitation in a pump that circulates the liquid. It is necessary to keep enough nitrogen in the system to keep the pressure high enough to prevent cavitation even when the liquid is at its coldest and thus at its smallest volume. It is also necessary to satisfy a competing requirement to, when the refrigerant is at its warmest and thus at its greatest volume, prevent the pressure from exceeding the level at which a relief valve opens and vents the head-space gaseous mixture of refrigerant vapor and nitrogen to the atmosphere. The pressure-control subsystem includes a supply of nitrogen at a pressure of 80 psig (gauge pressure of 552 kPa), a commercial electronic pressure regulator, a programmable-logic controller, and pressure and temperature sensors in the reservoir. The pressure-control subsystem adjusts the nitrogen pressure to the optimum value for the sensed temperature, thereby preventing both cavitation and venting.

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Improved Capacitive Quality Meter for a Two-Phase Fluid

Features include a better electrode configuration and several hardware improvements. A previously developed quality/flow meter has been redesigned to improve its performance as a device for mea- suring the quality (but not the flow) of two-phase (liquid + vapor) oxygen or nitrogen flowing in a pipe. As used in engineering disciplines concerned with two-phase flows, “quality” denotes, loosely, volume fractions of liquid or gas. Like some other quality meters, the previously developed meter and the present meter are based on a capacitance-measurement concept: The fluid flows through a space between electrodes, the capacitance between the electrodes is measured, and the volume fractions of liquid and gas are estimated from the effective permittivity, using the known relationships (a) between the effective permittivity and the capacitance and (b) between the volume fractions and the effective permittivity. The estimate of quality can be refined by use of additional data from pressure and temperature sensors.

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Ellipsoidal Collecting Horns for Ultrasonic Leak Detectors

Ellipsoidal reflectors have been proposed as collecting horns for ultrasonic leak det- ectors. Exploiting the classical focusing characteristics of ellipsoids, these ref- lectors would facilitate and enhance the detection of leaks in situations in which it is possible to bring leak-detecting sensors to within distances of the order of centimeters from leaks, but not closer. Leak detectors based on this concept could complement commercially available ultrasonic leak detectors equipped with paraboloidal reflectors for focusing over much longer distances. In a typical application, an ultrasonic receiving transducer would be positioned at one of the two foci of an ellipsoidal reflector. At the end opposite the transducer, the reflector would be truncated to provide an opening for the entry of sound and for positioning the reflector near a leak. When the reflector-and-transducer assembly was positioned to make the leak (or, for that matter, any other small source of ultrasound) lie at the other focus of the ellipsoid, the maximum amount of radiated ultrasound would be focused onto the transducer, resulting in maximum detector response. The principle of operation has been verified in experiments.

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Electrohydrodynamic Conduction Pumps

Pumping is achieved without moving parts and without direct charge injection. Electrohydrodynamic (EHD) conduction pumps have been investigated in theo- retical and experimental studies. In general, EHD pumps contain no moving parts. They generate pressure gradients and/or flows in dielectric liquids via any of a variety of inter- actions between (1) applied electric fields and (2) free and/or bound electric charges in the liquids. Like a related prior device denoted an EHD iondrag pump, an EHD conduction pump exploits interactions with free charges in liquids, but unlike an ion-drag pump, a conduction pump functions without direct injection of electric charges into the liquid. In the absence of direct injection, EHD conduction pumps are the only EHD devices that can pump isothermal liquids. EHD conduction pumps could be suitable for use as compact, low-power-consumption pumps to enhance flows and thus heat-transfer rates in heat pipes and capillary-pumped loops.

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