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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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An electrode framework with a fiber structure, universally applicable in alkaline storage battery systems, was developed and readied for production. Storage batteries with these electrodes present higher energy and power densities and are economical to produce. The design is applicable to all rechargable storage batteries and might replace the previous variety of designs.
This paper describes a tandem mirror magnetic plasma confinement device to be considered as a hot plasma source for the hybrid plume rocket concept. The hot plasma from this device is injected into an exhaust duct, which will interact with an annular layer of hypersonic neutral gas. Such a device can be used to study the dynamics of the hybrid plume and to experimentally verify the numerical predictions obtained with computer codes. The basic system design is also geared toward being lightweight and compact, as well as having high power density (i.e., several kW/sq cm) at the exhaust. This feature is aimed toward the feasibility of 'space testing'. The plasma is heated by microwaves. A 50 percent heating efficiency can be obtained by using two half-circle antennas. The preliminary Monte Carlo modeling of test particles result reported here indicates that interaction does take place in the exhaust duct. Neutrals gain energy from the ion, which confirms the hybrid plume concept.
The radial evolution of the power spectra of Alfvenic fluctuations observed within the trailing edge of high speed streams in the solar wind has been investigated using magnetic field measurements by Pioneer 10 and Pioneer 11 at heliocentric distances between 1 and 5 AU. In the analyzed frequency range (0.00028 - 0.0083 Hz) the spectral index of the computed spectra does not depend on frequency and is close to the value predicted for hydrodynamic turbulence. The radial gradient of the power density is independent of frequency and only slightly steeper than that expected for undamped propagation of Alfvenic fluctuations in a rarefaction region. The relation between the present results and those previously obtained by Helios 1 and 2 inside 1 AU is discussed.
Electrothermal auxiliary propulsion systems provide high performance options which can have major mission benefits. There are several electrothermal concepts which offer a range of characteristics and benefits. Resistojets are the highest thrust to power option and are currently operational at mission average values of specific impulse, I sub sp approximately 295 sec. Long life, multipropellant resistojets are being developed for the Space Station, and resistojet technology advancements are being pursued to improve the I sub sp by more than 20 percent for resistojets used in satellite applications. Direct current arcjets have the potential of I sub sp over 400 sec with storable propellants and should provide over 1000 sec with hydrogen. Advanced concepts are being investigated to provide high power density options and possible growth to primary propulsion applications. Broad based experimental and analytical research and technology programs of NASA are summarized and recent significant advances are reviewed.
Dry etching of cubic (100) beta-SiC single-crystal thin films produced via chemical-vapor deposition (CVD) has been performed in CF4 and CF4 + O2 mixtures, in both the reactive-ion-etching (RIE) and plasma-etching modes. The latter process yielded measurable etch rates, but produced a dark surface layer which appears, from the results of secondary-ion mass spectrometry, to be residual SiC. The RIE samples had no residual layer, but Auger electron spectroscopy did reveal a C-rich surface. The optimal RIE conditions were obtained with 10 sccm of pure CF4 at 40 mtorr and a power density of 0.548 W/sq cm, giving an etch rate of 23.3 nm/min. Neither the increase of temperature between 293 and 573 K, nor the incremental addition of O2 to CF4 to 50 percent, produced any strong effect on the etch rates of SiC during RIE. Pictorial evidence of fine line structures produced by RIE of beta-SiC films are also presented.
Phase-coherent emission with negligible far-field supermodes produced by proposed surface-emitting laser-diode array stimulated by holographically directed emission from single master diode. To achieve same coherence and output power, single laser diode requires high power density, which substantially reduces working lifetime. Proposed integrated optical array useful in communications
Spectra of zonal, meridional and vertical wind velocity, measured during a 24 hour period with the spaced-antenna technique indicate quite a variable slope as a function of height. It is found that the spectral slope (1h to 24h) of all three components correlates with the mean horizontal wind velocity. A possible conclusion is that the frequency dependence of power density of horizontal and vertical fluctuation component apparently depends on the mean wind velocity. However, the vertical spectra at periods larger than about 1 hour can also be influenced by spillover (due to finite radar antenna beam width) from the horizontal fluctuation component or by a Doppler shift.
Magnetohydrodynamic (MHD) energy conversion systems of the pulsed laser-supported detonation (LSD) wave, plasma MHD, and liquid-metal MHD (LMMHD) types are assessed for their potential as space-based laser-to-electrical power converters. These systems offer several advantages as energy converters relative to the present chemical, nuclear, and solar devices, including high conversion efficiency, simple design, high-temperature operation, high power density, and high reliability. Of these systems, the Brayton cycle liquid-metal MHD system appears to be the most attractive. The LMMHD technology base is well established for terrestrial applications, particularly with regard to the generator, mixer, and other system components. However, further research is required to extend this technology base to space applications and to establish the technology required to couple the laser energy into the system most efficiently. Continued research on each of the three system types is recommended.
A study of the optical characteristics of cloud-to-ground dischargers and how they compare with intracloud flashes was completed. Time resolved optical (7774A) and electric field-change waveforms were measured above clouds from a U2 airplane coincident with ground-based measurements of lightning. The optical pulse trains are studied for within and between flash variability. Specifically, for each flash researchers examine the 10, 50 (full width half maximum), and 90 percent pulse widths; the 10-10, 10-50, 10-90, and 10-peak percent amplitude rise times; the radiances (optical power densities); radiant energy densities; and pulse intervals. The optical pulse characteristics of first strokes, subsequent strokes, the intracloud components of cloud-to-ground flashes and intracloud flashes as viewed from above cloud are shown to exhibit very similar waveshapes, radiances and radiant energy densities. Descriptive statistics on these pulse categories were tabulated for 25 visually confirmed cloud-to-ground flashes (229 optical pulses) and 232 intracloud flashes (3126 optical pulses). A companion study of lightning observations above and below cloud in storms, storm complexes, and mesoscale convective systems has also been completed. Researchers compared the mapping of total lightning activity from above clouds with ground-based measurements and storm evolution. Although the total (IC + CG) lightning activity is the more representative indication of thunderstorm growth and decay, the ground strike data can be used to locate, diagnose, and track storm evolution in a number of instances.
The major accomplishments were the completion of the Basic Stirling Engine (BSE) and the Stirling Engine System (SES) designs on schedule, the approval and acceptance of those designs by NASA, and the initiation of manufacture of BSE components. The performance predictions indicate the Mod II engine design will meet or exceed the original program goals of 30% improvement in fuel economy over a conventional Internal Combustion (IC) powered vehicle, while providing acceptable emissions. This was accomplished while simultaneously reducing Mod II engine weight to a level comparable with IC engine power density, and packaging the Mod II in a 1985 Celebrity with no external sheet metal changes. The projected mileage of the Mod II Celebrity for the combined urban and highway CVS cycle is 40.9 mpg which is a 32% improvement over the IC Celebrity. If additional potential improvements are verified and incorporated in the Mod II, the mileage could increase to 42.7 mpg.
The methods for obtaining the gain pattern of an Air Traffic Control Radar using the data collected by NUSAT 1 are presented. The basic equations for this are given; these require an independently determined satellite attitude. In addition we show how simultaneous measurements made by separate channels can be related to obtain a single axis attitude, i.e., the direction of propagation of the incident radiation, and the power density of the radiation. This is done by solving a system of three algebraic equations.
Upstream waves associated with water group ions were detected by Giotto up to 5.2 million km from the nucleus of comet Halley. They show predominantly quasi-linear polarization with spectral characteristics typical of turbulent cascade processes. Spectral power densities are well above solar wind levels and at similar or lower levels than those observed near comet Giacobini-Zinner. The waveforms exhibit different characteristics from those detected by the ICE mission. Wavefront steepening and associated higher frequency wave packets are not identified.
A design for a space power station that is to transmit power to the surface of a planet via high powered microwaves should commence with the optimum design of the transmitting and receiving antenna combination to be employed. Once one has assured that the desired amount of power has been transferred (which, after all, is the prupose of any power transmission system), one can, from the constraints imposed by such a design, taylor other parameters of the system such as antenna sizes and weights, power density in the planet's atmosphere (e.g., to avoid electrical breakdown), and frequency of operation. It is the purpose of this brief analysis to provide the working equations of such an optimized antenna system, and to give examples of their use. Related problems that should be analyzed in the future will then be discussed and a flow chart of the indicated order of priority presented. The analysis given here differs from previous work on this subject in that the development given will allow analytical expressions to be obtained for the relevant parameters. This is made possible by employing an approximation procedure to be given during the exposition.
Two solar array designs developed for the Advanced Photovoltaic Solar Array program are described. The goal of the program is to develop solar arrays with higher mass specific power and power density and good robustness. The specific design requirements are: a beginning-of-life value of 130 W/kg, and end-of-life goals of 105 W/kg and 110 W/sq m. The two array-wing designs consisted of a single blanket. The differences in the blanket material (25 micron-thick Kapton versus 50 micron-thick carbon-loaded Kapton), solar cells (100 micron-thick wrap around versus 50 micron-thick 2 x 4 cm planar contact cells), and performance objectives (proposed industry requirements versus mission objectives) of the two designs are examined.
Quasi-periodic oscillations (QPOs) with frequencies in the range 5-50 Hz have recently been discovered in X-rays from two bright galactic-bulge sources and from Sco X-1. A shot-noise model that provides a mathematical framework for analyzing the constraints imposed on physical models by the observed power density spectra is described. A variety of physical models are then examined briefly. One of the most promising, the beat-frequency-modulated accretion model, is adopted as a working hypothesis to consider the clues it may provide concerning the galactic-bulge sources. Finally, some key observations are noted.
The extensive observations of Vela X-1 acquired from 1980 to 1984 with the Hakucho and Tenma satellites, using a pulse-filtering technique that provides a significant improvement in pulse-timing precision, are reexamined. The details of the preparation of this data base, including the determination of updated orbital parameters based on these and previously published observations covering a 10-yr interval, are reported. Preparatory to estimation of angular-acceleration flux-correlation pairs, substantially improved estimates of the power density of fluctuations in the derivative of the pulse frequency on analysis periods between 0.5 and 80 days are presented. These results support the phenomenological hypothesis that unresolved fluctuations in the angular acceleration of the neutron star, describable as random noise, are responsible for the entire history of the observed variation in pulse frequency of Vela X-1 on all time scales longer than a few days.
New biphase metal electrodes for alkali metal thermoelectric converter (AMETEC) exhibit low electrical resistance, fast alkali metal transport, and good power densities and lifetime at operating temperatures from 1,100 to 1,160 K. Electrodes expected to last as long as 10,000 h in service without significant degradation. Made of two refractory metals, one forms strong bonds with sodium, other inert to sodium.
A high rate active Li/SOCl2 cell was designed for use in a 28 volt, 250 amp-hour space battery system. The lithium battery is being considered as a replacement of its heavier silver-zinc counterpart on board the Centaur-G booster rocket which is used to launch payloads from the Space Shuttle cargo bay into deep-space. Basically a feasibility study, this development effort is demonstrating the ability of the lithium cell to deliver up to 90 amps safely at power densities of approximately 25 watts per pound. Test data on 4 prototype units is showing an energy density of 85 watt-hours per pound and 9.0 watt-hours/cu in. The cells tested typically delivered 280 to 300 amp-hours under ambient temperature test conditions using alternating continuous loads of 90, 55, and 20 amperes throughout life. Data from four cells tested are presented to demonstrate the capability of Li/SOCl2 technology for a C/3 discharge rate in active and hermetic cell units.