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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

First Results of the Gasdynamic Mirror Fusion Propulsion Experiment

An experimental Gasdynamic Mirror or GDM device has been constructed at the NASA Marshall Space Flight Center to provide an initial assessment of the applicability of this technology for propulsion systems. This paper presents the first experimental results obtained from the machine and an analysis of the types of plasma instabilities likely to be encountered. It is intended that this device operate at higher plasma densities and with much larger L/D ratios than previous mirror machines. The high L/D ratio minimizes to a large extent certain magnetic curvature effects which lead to plasma instabilities causing a loss of plasma confinement. The high plasma density results in the plasma behaving much more like a conventional fluid with a mean free path shorter than the length of the device. This characteristic helps reduce problems associated with "loss cone" microinstabilities. The device has been constructed to allow a considerable degree of flexibility in its configuration thus permitting the experiment to grow over time without necessitating a great deal of additional fabrication.

Emrich, William J., Jr.↗
NASA NTRS1991

High resolution, low energy avalanche photodiode X-ray detectors

Silicon avalanche photodiodes have been fabricated, and their performance as X-ray detectors has been measured. Photon sensitivity and energy resolution were measured as a function of size and operating parameters. Noise thresholds as low as 212 eV were obtained at room temperature, and backscatter X-ray fluorescence data were obtained for aluminum and other light elements. It is concluded that the results with the X-ray detector are extremely encouraging, and the performance is challenging the best available proportional counters. While not at the performance level of either cryogenic silicon or HgI2, these device operate at room temperature and can be reproduced in large numbers and with much larger areas than typically achieved with HgI2. In addition, they are rugged and appear to be indefinitely stable.

Farrell, R.↗
NASA NTRS2013

RF Exposure Analysis for Multiple Wi-Fi Devices In Enclosed Environment

Wi-Fi devices operated inside a metallic enclosure have been investigation in the recent years. A motivation for this study is to investigate wave propagation inside an enclosed environment such as elevator, car, aircraft, and spacecraft. There are performances and safety concerned that when the RF transmitters are used in the metallic enclosed environments. In this paper, the field distributions inside a confined room were investigated with multiple portable Wi-Fi devices. Computer simulations were performed using the rigorous computational electromagnetics (CEM). The method of moments (MoM) was used to model the mutual coupling among antennas. The geometrical theory of diffraction (GTD) was applied for the multiple reflections off the ground and walls. The prediction of the field distribution inside such environment is useful for the planning and deployment of a wireless radio and sensor system. Factors that affect the field strengths and distributions of radio waves in confined space were analyzed. The results could be used to evaluate the RF exposure safety in confined environment. By comparing the field distributions for various scenarios, it was observed that the Wi-Fi device counts, spacing and relative locations in the room are important factors in such environments. The RF Keep Out Zone (KOZ), where the electric field strengths exceed the permissible RF exposure limit, could be used to assess the RF human exposure compliance. As shown in this study, it s possible to maximize or minimize field intensity in specific area by arranging the Wi-Fi devices as a function of the relative location and spacing in a calculated manner.

Hwu, Shian U.↗
NASA NTRS1988

Enclosed capillary device for low gravity management of He II

To transfer He II in space, a large tank must be drained at low gravity. This paper describes and analyzes an enclosed gallery device designed for collecting and delivering He II to a pump. The device allows most of the liquid to move about in the tank while it maintains a liquid flow to the pump. Only the liquid in the screen-covered gallery channels and in the upper and lower receivers is contained. The device operates by providing surface tension dominated liquid paths from all locations within the tank to the lower receiver, which houses the pump. Since the fluid pressure in the channels may be below the saturated vapor pressure, an analysis of He II cavitation is performed to determine if cavitation will occur. The effect of heat dissipation from the pump is examined to determine if it may result in nucleation of boiling. It is concluded that this enclosed device can meet the requirements for transfer of He II under the predicted adverse accelerations that will be encountered on-orbit.

Frank, D. J.↗
NASA NTRS1987

Mass storage systems for data transport in the early space station era 1992-1998

NASA's Space Station Program will provide a vehicle to deploy an unprecedented number of data producing experiments and operational devices. Peak down link data rates are expected to be in the 500 megabit per second range and the daily data volume could reach 2.4 terabytes. Such startling requirements inspired an internal NASA study to determine if economically viable data storage solutions are likely to be available to support the Ground Data Transport segment of the NASA data system. To derive the requirements for data storage subsystems, several alternative data transport architectures were identified with different degrees of decentralization. Data storage operations at each subsystem were categorized based on access time and retrieval functions, and reduced to the following types of subsystems: First in First out (FIFO) storage, fast random access storage, and slow access with staging. The study showed that industry funded magnetic and optical storage technology has a reasonable probability of meeting these requirements. There are, however, system level issues that need to be addressed in the near term.

Carper, Richard↗
NASA NTRS1985

Feasibility of steady-state, multi-megawatt MPD thrusters

The feasibility of operating the MPD thruster at sustained, multi-megawatt power levels for application to nuclear powered earth orbital maneuvering and outer planet orbiters is addressed by examining cathode erosion processes. The cathode is studied first since it operates in the most severe environment. Due to current, power, and geometrical constraints imposed by the need for high thruster efficiency the cathode must provide 200-400 A/sq cm at incandescent temperatures. This level must be sustained for hundreds of hours to propel a 13,000 kg payload, 5 MW vehicle from low earth orbit to say geosynchronous orbit in 7 days. The physics of thermionic emission are shown by experiment and theory to dominate the thermal balance and cathode sheath such that electron cooling keeps the cathode cool enough to avoid rapid evaporation. Experiments using a subscale MPD test device operating at continuous power levels of 10-30 kW show that cathode temperature can be kept to 2100-2200 K at the high current densities required for a full-sized, multi-megawatt thruster.

King, D. Q.↗
NASA NTRS2014

HgCdTe e-APD Detector Arrays with Single Photon Sensitivity for Space Lidar Applications

A multi-element HgCdTe electron initiated avalanche photodiode (e-APD) array has been developed for space lidar applications. The detector array was fabricated with 4.3-μm cutoff HgCdTe which covered a spectral response from 0.4 to 4.3 μm. We have characterized a 4x4 detector array with 80 μm square elements and an integrated custom cryogenic silicon read-out integrated circuit (ROIC). The device operated at 77K inside a small closed-cycle Dewar. Measurements showed a unity gain quantum efficiency of about 90% at 1.55 μm. The bulk dark current of the HgCdTe e-APD at 77K was less than 50,000 input referred electrons/s at 12 V APD bias where the APD gain was 620 and the measured noise equivalent power (NEP) was 0.4 fW/Hz1/2. The electrical bandwidth of the ROIC was about 6 MHz, which was chosen to match the laser pulse width of our CO2 lidar. Even with the relatively low bandwidth, the high APD gain and low dark current enabled the device to detect single photon events. Because the APD was biased below the break-down voltage, the detector output was linear with the input optical signal and there was no dead-time and afterpulsing. A new series of HgCdTe e-APDs are being developed with a much wider bandwidth ROIC and higher gain HgCdTe e-APD array, which is expected to give a much better performance in linear mode photon counting applications.

HgCdTe↗
NASA NTRS1979

Some limitations on processing materials in acoustic levitation devices

The spot heating of samples, suspended in an acoustic field, was investigated to determine if the technique could be used to process materials. A single axis resonance device operating in air at 25 C with an rms pressure maximum of 160 to 170 db was used in the experiments. The heat flow from a hot object suspended in a levitation node is dominated by the effects of the field, with the heat loss approximately 20 times larger than that due to natural convection. The acoustic forces which suspend the body at a node also serve to eject the heated air. The coupling between the locally heated region around the body and the acoustic field results in instabilities in both the pressure wave and force field. The investigations indicated the extreme difficulties in developing a materials processing device based on acoustic/spot heating for use in a terrestrial environment.

Oran, W. A.↗
NASA NTRS1994

Method and apparatus for removing unwanted reflections from an interferometer

A device for eliminating unwanted reflections from refractive optical elements in an optical system is provided. The device operates to prevent desired multiple fringe patterns from being obscured by reflections from refractive elements positioned in proximity to a focal plane of the system. The problem occurs when an optical beam is projected into, and reflected back out of, the optical system. Surfaces of the refractive elements reflect portions of the beam which interfere with portions of the beam which are transmitted through the refractive elements. Interference between the reflected and transmitted portions of the beam produce multiple fringe sets which tend to obscure desired interference fringes. With the refractive optical element in close proximity to the focal plane of the system, the undesired reflected light reflects at an angle 180 degrees opposite from the desired transmitted beam. The device exploits the 180-degree offset, or rotational shear, of the undesired reflected light by providing an optical stop for blocking one-half of the cross-section of the test beam. By blocking one-half of the test beam, the undesired offset beam is blocked, while the returning transmitted beam passes into the optical system unaffected. An image is thereby produced from only the desired transmitted beam. In one configuration, the blocking device includes a semicircular aperture which is caused to rotate about the axis of the test beam. By rotating, all portions of the test beam are cyclically projected into the optical system to thereby produce a complete test image. The rotating optical stop is preferably caused to rotate rapidly to eliminate flicker in the resulting image.

Steimle, Lawrence J.↗
NASA NTRS2013

Nanoscale Surface Plasmonics Sensor With Nanofluidic Control

Conventional quantitative protein assays of bodily fluids typically involve multiple steps to obtain desired measurements. Such methods are not well suited for fast and accurate assay measurements in austere environments such as spaceflight and in the aftermath of disasters. Consequently, there is a need for a protein assay technology capable of routinely monitoring proteins in austere environments. For example, there is an immediate need for a urine protein assay to assess astronaut renal health during spaceflight. The disclosed nanoscale surface plasmonics sensor provides a core detection method that can be integrated to a lab-on-chip device that satisfies the unmet need for such a protein assay technology. Assays based upon combinations of nanoholes, nanorings, and nanoslits with transmission surface plasmon resonance (SPR) are used for assays requiring extreme sensitivity, and are capable of detecting specific analytes at concentrations as low as picomole to femtomole level in well-controlled environments. The device operates in a transmission mode configuration in which light is directed at one planar surface of the array, which functions as an optical aperture. The incident light induces surface plasmon light transmission from the opposite surface of the array. The presence of a target analyte is detected by changes in the spectrum of light transmitted by the array when a target analyte induces a change in the refractive index of the fluid within the nanochannels. This occurs, for example, when a target analyte binds to a receptor fixed to the walls of the nanochannels in the array. Independent fluid handling capability for individual nanoarrays on a nanofluidic chip containing a plurality of nanochannel arrays allows each array to be used to sense a different target analyte and/or for paired arrays to analyze control and test samples simultaneously in parallel. The present invention incorporates transmission mode nanoplasmonics and nanofluidics into a single, microfluidically controlled device. The device comprises one or more arrays of aligned nanochannels that are in fluid communication with inflowing and outflowing fluid handling manifolds that control the flow of fluid through the arrays. The array acts as an aperture in a plasmonic sensor. Fluid, in the form of a liquid or a gas and comprising a sample for analysis, is moved from an inlet manifold through the nanochannel array, and out through an exit manifold. The fluid may also contain a reagent used to modify the interior surfaces of the nanochannels, and/or a reagent required for the detection of an analyte.

Wei, Jianjun↗
NASA NTRS1966

Torus elements used in effective shock absorber

Energy absorbing device forces torus elements to revolve annularly between two concentric tubes when a load is applied to one tube. Interference forces can be varied by using torus elements of different thicknesses. The device operates repeatedly in compression or tension, and under problems of large onset rate tolerance or structural overload.

Cunningham, P.↗
NASA NTRS1967

Automatic channel switching device

Automatic channel switching device operates with all three triple modular redundant channels when there are no errors. When a failure occurs, channel and module switching isolate the failure to a specific channel. Since only one must operate correctly, reliability is increased.

Ball, M.↗
NASA NTRS1966

Summary

Summary of papers presented at NASA-university program conference on dynamic and other models, control devices, operator performance, and information theory related to manual control

OPERATOR PERFORMANCE↗
NASA NTRS1969

Improved VHF direction finding system

Direction finding device operating at very high frequencies requires a loop antenna, mechanical rotation, and large structures. The system is applicable to an unmanned configuration. Direction information is extracted in the form of a direction cosine analog.

Graf, E. R.↗
NASA NTRS1970

Fuse and switch functions combined within a single housing

Fuswitch provides both switch and fuse functions within a single housing. A mercury capillary is used to alternately vaporize and condense the mercury within a reservoir. The housing is impervious to mercury and the fuse portion of the device operates on the principle of the self-healing mercury fuse.

Cohn, E. M.↗
NASA NTRS1970

Remotely actuated release mechanism

Release mechanism for actuation of automatic device operates on system of restrained energy force, which is automatically released by electrical charge that may be applied by manual switch or, in remote application, by RF impulse, received by conventional electronic circuitry.

Rotta, J. W., Jr.↗