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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 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Finite volume solution of the compressible boundary-layer equations

A box-type finite volume discretization is applied to the integral form of the compressible boundary layer equations. Boundary layer scaling is introduced through the grid construction: streamwise grid lines follow eta = y/h = const., where y is the normal coordinate and h(x) is a scale factor proportional to the boundary layer thickness. With this grid, similarity can be applied explicity to calculate initial conditions. The finite volume method preserves the physical transparency of the integral equations in the discrete approximation. The resulting scheme is accurate, efficient, and conceptually simple. Computations for similar and non-similar flows show excellent agreement with tabulated results, solutions computed with Keller's Box scheme, and experimental data.

Loyd, B.↗
NASA NTRS1985

Severe storm detection with passive 37 GHz observations

The research objective was to determine the information content of satellite passive 37 GHz brightness temperatures on the severity of thunderstorms through the measurement of the attenuation (scattering) signature of precipitation. The severe storm detection potential of satellite-observed passive 37 GHz radiances was evaluated by comparing Nimbus-7 Scanning Multi-channel Microwave Radiometer (SMMR) data to reports of severe weather contained in the NSSFC severe weather log for calendar years 1979 and 1980 over the United States east of the Rocky Mountains. Heavy thunderstorms have a characteristic signature in the form of localized very low 37 GHz T sub B from scattering by precipitation-size ice particles (thick cirrus being transparent at this frequency). The local noon and midnight snapshots taken by the SMMR on alternating days (with incomplete areal coverage of the U.S. on any given day) were scanned to find cases of strong scattering by precipitation, revealed by large differences between the 18 and 37 GHz brightness temperatures, the 37 GHz T sub B being at least 20 C lower than the 18 GHz T sub B. The value of the 37 GHz T sub b was then compared to severe weather reports within one hour of the SMMR observation time, in the vicinity of the SMMR-observed storm. It was found that the degree to which the T sub B were lowered was a fairly good indicator of the probability that the storm was severe. Of 263 storms observed by the SMMR during 1979 and 1980, 54 percent had severe weather associated with them for a T sub b below 203 K, while 8 percent of those above this threshold were severe.

Spencer, R. W.↗
NASA NTRS1986

Method of examining microcircuit patterns

Examination of microstructures of LSI and VLSI devices is facilitated by employing a method in which the device is photographed through a darkfield illumination optical microscope and the resulting negative subjected to inverse processing to form a positive on a photographic film. The film is then developed to form photographic prints or transparencies which clearly illustrate the structure of the device. The entire structure of a device may be examined by alternately photographing the device and selectively etching layers of the device in order to expose underlying layers.

Suszko, S. F.↗
NASA NTRS1986

Large TV display system

A relatively small and low cost system is provided for projecting a large and bright television image onto a screen. A miniature liquid crystal array is driven by video circuitry to produce a pattern of transparencies in the array corresponding to a television image. Light is directed against the rear surface of the array to illuminate it, while a projection lens lies in front of the array to project the image of the array onto a large screen. Grid lines in the liquid crystal array are eliminated by a spacial filter which comprises a negative of the Fourier transform of the grid.

Liu, Hua-Kuang↗
NASA NTRS1986

An evaluation of the documented requirements of the SSP UIL and a review of commercial software packages for the development and testing of UIL prototypes

A review was conducted of software packages currently on the market which might be integrated with the interface language and aid in reaching the objectives of customization, standardization, transparency, reliability, maintainability, language substitutions, expandability, portability, and flexibility. Recommendations are given for best choices in hardware and software acquisition for inhouse testing of these possible integrations. Software acquisition in the line of tools to aid expert-system development and/or novice program development, artificial intelligent voice technology and touch screen or joystick or mouse utilization as well as networking were recommended. Other recommendations concerned using the language Ada for the user interface language shell because of its high level of standardization, structure, and ability to accept and execute programs written in other programming languages, its DOD ownership and control, and keeping the user interface language simple so that multiples of users will find the commercialization of space within their realm of possibility which is, after all, the purpose of the Space Station.

Gill, Esther Naomi↗
NASA NTRS1986

Venus Radar Mapper (VRM): Multimode radar system design

The surface of Venus has remained a relative mystery because of the very dense atmosphere that is opaque to visible radiation and, thus, normal photographic techniques used to explore the other terrestrial objects in the solar system are useless. The atmosphere is, however, almost transparent to radar waves and images of the surface have been produced via Earth-based and orbital radars. The technique of obtaining radar images of a surface is variously called side looking radar, imaging radar, or synthetic aperture radar (SAR). The radar requires a moving platform in which the antenna is side looking. High resolution is obtained in the cross-track or range direction by conventional radar pulse encoding. In the along-track or azimuth direction, the resolution would normally be the antenna beam width, but for the SAR case, a much longer antenna (or much sharper beam) is obtained by moving past a surface target as shown, and then combining the echoes from many pulses, by using the Doppler data, to obtain the images. The radar design of the Venus Radar Mapper (VRM) is discussed. It will acquire global radar imagery and altimetry data of the surface of Venus.

Johnson, William T. K.↗
NASA NTRS1986

Local network interconnection through a satellite point-to-multipoint link

Four architectures to implement a point to multipoint satellite link protocol for communication services offered by the Telecom 1 satellite network are presented. A safe communication service with error correction and flow control facilities is described. It is shown that a time transparent communication system combines simplicity and cost advantages.

Duarte, O. Muniz Bandeira↗
NASA NTRS1987

Hitchhiker-G: A new carrier system for attached shuttle payloads

A new carrier system has been developed for economical and quick response flight of small attached payloads on the space shuttle. Hitchhiker-G can accommodate up to 750 lb. of customer payloads in canisters or mounted to an exposed plate. The carrier connects to the orbiter's electrical systems and provides up to six customers with standard electrical services including power, real time telemetry, and commands. A transparent data and command system concept is employed to allow the customer to easily use his own ground support equipment and personnel to control his payload during integration and flight operations. The first Hitchhiker-G was successfully flown in January 1986 on STS 61C.

Goldsmith, T. C.↗
NASA NTRS1987

Automatic processing system for shadowgraph and interference patterns

The design and operation of an automatic system for the processing of shadowgraph and interference images are described. The system includes a two-coordinate processing table with an optical system for the projection of transparent images onto the photodetector, an image filter in the photodetector field, and a device for controlling the movement of the table and transmitting information to the minicomputer.

Vereninov, I. A.↗
NASA NTRS1987

Workshop on Structural Dynamics and Control Interaction of Flexible Structures

The Hubble Space Telescope features the most exacting line of sight jitter requirement thus far imposed on a spacecraft pointing system. Consideration of the fine pointing requirements prompted an attempt to isolate the telescope from the low level vibration disturbances generated by the attitude control system reaction wheels. The primary goal was to provide isolation from axial component of wheel disturbance without compromising the control system bandwidth. A passive isolation system employing metal springs in parallel with viscous fluid dampers was designed, fabricated, and space qualified. Stiffness and damping characteristics are deterministic, controlled independently, and were demonstrated to remain constant over at least five orders of input disturbance magnitude. The damping remained purely viscous even at the data collection threshold of .16 x .000001 in input displacement, a level much lower than the anticipated Hubble Space Telescope disturbance amplitude. Vibration attenuation goals were obtained and ground test of the vehicle has demonstrated the isolators are transparent to the attitude control system.

Davis, L. P.↗
NASA NTRS1987

A new hydrodynamic analysis of double layers

A genuine two-fluid model of plasmas with collisions permits the calculation of dynamic (not necessarily static) electric fields and double layers inside of plasmas including oscillations and damping. For the first time a macroscopic model for coupling of electromagnetic and Langmuir waves was achieved with realistic damping. Starting points were laser-produced plasmas showing very high dynamic electric fields in nonlinear force-produced cavitous and inverted double layers in agreement with experiments. Applications for any inhomogeneous plasma as in laboratory or in astrophysical plasmas can then be followed up by a transparent hydrodynamic description. Results are the rotation of plasmas in magnetic fields and a new second harmonic resonance, explanation of the measured inverted double layers, explanation of the observed density-independent, second harmonics emission from laser-produced plasmas, and a laser acceleration scheme by the very high fields of the double layers.

Hora, Heinrich↗
NASA NTRS1987

Sol-Gel synthesis of MgO-SiO2 glass compositions having stable liquid-liquid immiscibility

MgO-SiO2 glasses containing up to 15 mol % MgO, which could not have been prepared by the conventional glass melting method due to the presence of stable liquid-liquid immiscibility, were synthesized by the sol-gel technique. Clear and transparent gels were obtained from the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) and magnesium nitrate hexahydrate when the water/TEOS mole ratio was four or more. The gelling time decreased with increase in magnesium content, water/TEOS ratio, and reaction temperature. Magnesium nitrate hexahydrate crystallized out of the gels containing 15 and 20 mol % MgO on slow drying. This problem was partially alleviated by drying the gels quickly at higher temperatures. Monolithic gel samples were prepared using glycerol as the drying control additive. The gels were subjected to various thermal treatments and characterized by several methods. No organic groups could be detected in the glasses after heat treatments to approx. 800 C, but trace amounts of hydroxyl groups were still present. No crystalline phase was found from X-ray diffraction in the gel samples to approx. 890 C. At higher temperatures, alpha quartz precipitated out as the crystalline phase in gels containing up to 10 mol % MgO. The overall activation energy for gel formation in 10MgO-90SiO2 (mol %) system for water/TEOS mole ratio of 7.5 was calculated to be 58.7 kJ/mol.

Bansal, Narottam P.↗
NASA NTRS1986

Heavy doping effects in high efficiency silicon solar cells

The temperature dependence of the emitter saturation current for bipolar devices was studied by varying the surface recombination velocity at the emitter surface. From this dependence, the value was derived for bandgap narrowing that is in better agreement with other determinations that were obtained from the temperature dependence measure on devices with ohmic contacts. Results of the first direct measurement of the minority-carrier transit time in a transparent heavily doped emitter layer were reported. The value was obtained by a high-frequency conductance method recently developed and used for doped Si. Experimental evidence is presented for significantly greater charge storage in highly excited silicon near room temperature than conventional theory would predict. These data are compared with various data for delta E sub G in heavily doped silicon.

Lindholm, F. A.↗
NASA NTRS1987

Laser schlieren crystal monitor

A system and method for monitoring the state of a crystal which is suspended in a solution is described which includes providing a light source for emitting a beam of light along an optical axis. A collimating lens is arranged along the optical axis for collimating the emitted beam to provide a first collimated light beam consisting of parallel light rays. By passing the first collimated light beam through a transparent container, a number of the parallel light rays are deflected off the surfaces of said crystal being monitored according to the refractive index gradient to provide a deflected beam of deflected light rays. A focusing lens is arranged along optical axis for focusing the deflected rays towards a desired focal point. A knife edge is arranged in a predetermined orientation at the focal point; and a screen is provided. A portion of the deflected beam is blocked with the knife edge to project only a portion of the deflected beam. A band is created at one edge of the image of the crystal which indicates the state of change of the surface of the crystal being monitored.

Owen, Robert B.↗
NASA NTRS1986

Jet transport flight operations using cockpit display of traffic information during instrument meteorological conditions: Simulation evaluation

A simulation study was undertaken to evaluate flight operations using cockpit display of traffic information (CDTI) in a conventional jet transport aircraft. Eight two-person airline flight crews participated as test subjects flying simulated terminal area approach and departure operations under instrument meteorological conditions (IMC). A fixed-base cockpit simulator configured with a full complement of conventional electromechanical instrumentation to permit full workload operations was utilized. Traffic information was displayed on a color cathode-ray tube (CRT) mounted above the throttle quadrant in the typical weather radar location. A transparent touchpanel overlay was utilized for pilot interface with the display. Air traffic control (ATC) simulation included an experienced controller and full partyline radio environment for evaluation of pilot-controlled self-separation and traffic situation monitoring tasks. Results of the study revealed the CDTI to be well received by the test subjects as a useful system which could be incorporated into an existing jet transport cockpit. Crew coordination and consistent operating procedures were identified as important considerations in operational implementation of traffic displays. Cockpit workload was increased with active CDTI tasks. However, all test subjects rated the increase to be acceptable.

Williams, David H.↗
NASA NTRS1986

The heliospheric energy source

The solar wind and the heliosphere exist as a consequence of the heat input to the corona, particularly the coronal holes. The necessary energy input to coronal holes has been estimated to be 10 to the 6th erg/sq cm sec, requiring Alfven waves with rms fluid velocities of 100 km/sec. Observational upper limits on coronal fluid velocities are of the order of 25 km/sec, which may not apply to the transparent coronal hole. Alternatively it has been suggested that coronal holes may be heated by agitation from neighboring active regions, suggesting that the vigor of a coronal hole depends upon its location. The Ulysses Mission will provide a direct comparison of the strength of the high speed wind from coronal holes at low latitude and coronal holes at high latitude, from which the nature of the presently unknown energy sources of the coronal holes and the resulting structure of the heliosphere may be better judged. The question is fundamental to the dynamics of the windspheres of all stars.

Parker, E. N.↗
NASA NTRS1986

NASA's robotic servicing role for Space Station

Attention is given to evaluations of the relative impacts on and benefits to the Space Station Program of various levels of robotics devices for space servicing operations. The leading robotic candidate concept for the IOC Space Station, the Smart Front End, uses a small, stiff and highly dexterous work effector controlled by a human-in-the-loop from a remote control station. This configuration offers both a quality multifunctional performance capability at the work site as well as technology transparency through the ground teleoperation control mode.

Powell, L.↗