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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

On-board near-optimal climb-dash energy management

On-board real time flight control is studied in order to develop algorithms which are simple enough to be used in practice, for a variety of missions involving three dimensional flight. The intercept mission in symmetric flight is emphasized. Extensive computation is required on the ground prior to the mission but the ensuing on-board exploitation is extremely simple. The scheme takes advantage of the boundary layer structure common in singular perturbations, arising with the multiple time scales appropriate to aircraft dynamics. Energy modelling of aircraft is used as the starting point for the analysis. In the symmetric case, a nominal path is generated which fairs into the dash or cruise state.

Weston, A. R.↗
NASA NTRS1984

Analysis of a 10 megawatt space-based solar-pumped neodymium laser system

A ten megawatt solar-pumped continuous liquid laser system for space applications is examined. It is found that a single inflatable mirror of 434 m diameter used in conjunction with a conical secondary concentrator is sufficient to side pump a liquid neodymium lasant in an annular tube of 6 m length and 1 m outer and 0.8 m inner diameter. About one fourth of intercepted radiation converging on the laser tube is absorbed and one fifth of this radiation is effective in populating the upper levels. The liquid lasant is flowed through the annular laser cavity at 1.9 m/s and is cooled via a heat exchanger and a large radiator surface comparable in size to the concentrating mirror. The power density of incident light within the lasant of approximately 68 watt/cu cm required for cw operation is exceeded in the present annular configuration. Total system weight corresponds to 20,500 kg and is thus capable of being transported to near Earth orbit by a single shuttle flight.

Kurweg, U. H.↗
NASA NTRS1983

Remote sensing of agricultural crops and soils

Research in the correlative and noncorrelative approaches to image registration and the spectral estimation of corn canopy phytomass and water content is reported. Scene radiation research results discussed include: corn and soybean LANDSAT MSS classification performance as a function of scene characteristics; estimating crop development stages from MSS data; the interception of photosynthetically active radiation in corn and soybean canopies; costs of measuring leaf area index of corn; LANDSAT spectral inputs to crop models including the use of the greenness index to assess crop stress and the evaluation of MSS data for estimating corn and soybean development stages; field research experiment design data acquisition and preprocessing; and Sun-view angles studies of corn and soybean canopies in support of vegetation canopy reflection modeling.

Bauer, M. E.↗
NASA NTRS1984

A note on the temporal behavior of bucket hydrologies

The use of a "canopy' bucket to more accurately represent evapotranspiration over land surfaces is explained. The temporal behavior of the traditional bucket model is compared with one that mimics the effects of interception loss. Results are presented in terms of the spectral response of the parameterization to a hypothetical white noise forcing.

Suarez, M. J.↗
NASA NTRS1984

Supersonic STOVL aircraft with turbine bypass/turbo-compressor engines

Three propulsion systems for a Mach 2 STOVL fighter were compared. The three propulsion systems are: (1) turbine bypass engine with a turbocompressor used for STOVL only; (2) turbine bypass engine with a turbocompressor for both STOVL and thrust during forward flight; and (3) mixed flow afterburning turbofan with a remote burner lift system. In the first system, the main engines have afterburners and the turbocompressors use after burning during STOVL. In the second system, the turbine bypass engines are dry and the turbocompressors have afterburners. The mission used in the study is a deck launched intercept mission. It is indicated that large improvements in combat time are possible when the turbocompressors are used for both left and thrust for forward flight.

Franciscus, L. C.↗
NASA NTRS1984

Optical Analysis of Cassegrainian Point Focus Concentrators

A Cassegrainian solar concentrator, using a 7-meter diameter primary reflector, was analyzed in three forms: (1) an unmodified Cassegrainian, (2) the Ritchey-Chretien configuration, and (3) the unmodified Cassegrainian with a non-imaging tertiary reflector. Optical performance was not significantly improved with the Ritchey-Chretien; however, the tertiary resulted in significant improvement in intercept factor and optical efficiency. The effects of misalignment of the secondary and tertiary reflectors on the optical performance of the collector were also analyzed.

Waterbury, S. S.↗
NASA NTRS1984

A Nomographic Methodology for Use in Performance Trade-Off Studies of Parabolic Dish Solar Power Modules

A simple graphical method was developed to undertake technical design trade-off studies for individual parabolic dish models comprising a two-axis tracking parabolic dish with a cavity receiver and power conversion assembly at the focal point. The results of these technical studies are then used in performing the techno-economic analyses required for determining appropriate subsystem sizing. Selected graphs that characterize the performance of subsystems within the module were arranged in the form of a nomogram that would enable an investigator to carry out several design trade-off studies. Key performance parameters encompassed in the nomogram include receiver losses, intercept factor, engine rating, and engine efficiency. Design and operation parameters such as concentrator size, receiver type (open or windowed aperture), receiver aperture size, operating temperature of the receiver and engine, engine partial load characteristics, concentrator slope error, and the type of reflector surface, are also included in the graphical solution. Cost considerations are not included.

Selcuk, M. K.↗
NASA NTRS1984

Severe storm electricity

Successful ground truth support of U-2 overflights was been accomplished. Data have been reduced for 4 June 1984 and some of the results have been integrated into some of MSFC's efforts. Staccato lightning (multiply branched, single stroke flash with no continuing current) is prevalent within the rainfree region around the main storm updraft and this is believed to be important, i.e., staccato flashes might be an important indicator of severe storm electrification. Results from data analysis from two stations appear to indicate that charge center heights can be estimated from a combination of intercept data with data from the fixed laboratory at NSSL. An excellent data base has been provided for determining the sight errors and efficiency of NSSL's LLP system. Cloud structures, observable in a low radar reflectivity region and on a scale smaller than is currently resolved by radar, which appear to be related to electrical activity are studied.

Arnold, R. T.↗
NASA NTRS1983

Viscosity of rock-ice mixtures and applications to the evolution of icy satellites

Theory and experiments are used to establish lower and upper bounds on the ratio of actual viscosity to pure ice viscosity for a suspension of rock particles in a water ice matrix. A rheological model for rock-ice mixtures is described, establishing bounds for the range of possible viscosity enhancements provided by a suspension of silicate spheres in an ice matrix. A parametrized thermal convection model is described and used to determine a criterion for criticality, defined as the heat flow and/or silicate volume fraction for which the satellite temperature profile intercepts the melting curve of water ice. The consequences of achieving this critical state are examined, and it is shown that under certain circumstances a 'runaway' differentiation can occur in which the silicates settle to form a core and extensive melting of water ice takes place, the latent heat being supplied by the gravitational energy of differentiation. A possible application of these results to Ganymede and Callisto is described.

Friedson, A. J.↗
NASA NTRS1983

A mathematical model for crop spectral-temporal trajectories based on a plant growth model

The Kubelka-Munk radiative transfer model is combined with an approximation of Kauth-Thomas greeness and brightness transforms to derive approximate closed form expressions for crop greeness and brightness surrogates in terms of canopy biomass. The greeness relation derived resembles an existing empirical relation between leaf area index and greeness. A simple growth model based on interception and utilization of photosynthetically active radiation is developed and used to describe the time evolution of greeness and brightness. The model developed does not yet yield definitive profile calculations but suggests a conceptual framework which may be found useful for further profile analysis.

Woolford, T. L.↗
NASA NTRS1983

Supersonic fan engines for military aircraft

Engine performance and mission studies were performed for turbofan engines with supersonic through-flow fans. A Mach 2.4 CTOL aircraft was used in the study. Two missions were considered: a long range penetrator mission and a long range intercept mission. The supersonic fan engine is compared with an augmented mixed flow turbofan in terms of mission radius for a fixed takeoff gross weight of 75,000 lbm. The mission radius of aircraft powered by supersonic fan engines could be 15 percent longer than aircraft powered with conventional turbofan engines at moderate thrust to gross weight ratios. The climb and acceleration performance of the supersonic fan engines is better than that of the conventional turbofan engines. Previously announced in STAR as N83-34947

Franciscus, L. C.↗
NASA NTRS1983

Variable line-space gratings - New designs for use in grazing incidence spectrometers

An account is given of a fundamentally different approach to the use of variable line-space gratings for grazing incidence spectrometers. In the new approach, the gratings are flat and they are placed to intercept the converging beam from a collecting mirror rather than the diverging beam from a slit. This results in (1) small aberrations over a wide instantaneous range in wavelength, (2) a modest required variation in line spacing across the ruled width, (3) a simultaneous minimization of both the spectral and image height aberrations, and (4) a completely stigmatic zero order image. The slitless arrangement common to these designs is very compact, having no additional length behind the focal plane of the collecting mirror. In-plane and conical fan designs are considered. One combination design, in the form of an echelle spectrometer, is discussed. The designs are considered to represent ideal candidates for moderate to high resolution spectrometers on such missions as the Far Ultraviolet Spectroscopic Explorer (FUSE, now Columbus) and the Advanced X-ray Astrophysics Facility (AXAF).

Hettrick, M. C.↗
NASA NTRS1983

The application of turbine bypass engines to high performance V/STOL aircraft

A study of the application of the turbine bypass engine (TBE) concept to high-performance V/STOL aircraft is in progress. The study is designed to identify the most promising TBE cycles for combination with a remote augmentor lift system (RALS), and to compare them with conventional turbofan RALS and lift-plus-lift/cruise concepts. Three cycles chosen for study are 15- and 30-percent-bypass-bleed TBE with simple RALS and 15-percent-bypass-bleed TBE with a turbo-compressor-RALS combination. Aircraft configurations were developed for the 15-percent-bleed TBE with simple and turbocompressor RALS and sized to a naval, supersonic, deck-launched, intercept mission. Early sizing results indicate that these two concepts give comparable airplane performance, although the simple RALS configuration has some potential design drawbacks that are avoided in the turbo-compressor RALS design.

Sheridan, A. E.↗
NASA NTRS1983

On-board near-optimal climb-dash energy management

On-board real time flight control is studied in order to develop algorithms which are simple enough to be used in practice, for a variety of missions involving three-dimensional flight. The intercept mission in symmetric flight is emphasized. Extensive computation is required on the ground prior to the mission but the ensuing on-board exploitation is extremely simple. The scheme takes advantage of the boundary layer structure common in singular perturbations, arising with the multiple time scales appropriate to aircraft dynamics. Energy modelling of aircraft is used as the starting point for the analysis. In the symmetric case, a nominal path is generated which fairs into the dash or cruise state. Previously announced in STAR as N84-16116

Weston, A. R.↗
NASA NTRS1983

The use and misuse of statistical analyses

The statistical techniques most often used in space physics include Fourier analysis, linear correlation, auto- and cross-correlation, power spectral density, and superposed epoch analysis. Tests are presented which can evaluate the significance of the results obtained through each of these. Data presented without some form of error analysis are frequently useless, since they offer no way of assessing whether a bump on a spectrum or on a superposed epoch analysis is real or merely a statistical fluctuation. Among many of the published linear correlations, for instance, the uncertainty in the intercept and slope is not given, so that the significance of the fitted parameters cannot be assessed.

Reiff, P. H.↗
NASA NTRS1984

Supersonic STOVL aircraft with turbine bypass/turbo-compressor engines

Three propulsion systems for a Mach 2 STOVL fighter were compared. The three propulsion systems are: (1) turbine bypass engine with a turbocompressor used for STOVL only; (2) turbine bypass engine with a turbocompressor for both STOVL and thrust during forward flight; and (3) mixed flow afterburning turbofan with a remote burner lift system. In the first system, the main engines have afterburners and the turbocompressors use afterburning during STOVL. In the second system, the turbine bypass engines are dry and the turbocompressors have afterburners. The mission used in the study is a deck launched intercept mission. It is indicated that large improvements in combat time are possible when the turbocompressors are used for both left and thrust for forward flight. Previously announced in STAR as N84-24582

Franciscus, L. C.↗
NASA NTRS1984

Alternative gravity-assist sequences for the ISEE-3 escape trajectory

The International Sun-Earth Explorer-3 (ISEE-3) was moved from its mission halo orbit upstream of the earth's magnetosphere on June 10, 1982. Multiple lunar swingby maneuvers were then used to shape the trajectory for extensive exploration of the distant geomagnetic tail and finally to place the spacecraft on a course that will intercept the comet Giacobini-Zinner on September 11, 1985. With this new mission objective, the spacecraft was renamed the International Cometary Explorer (ICE). A double-lunar-swingby control technique involving five passes by the moon was eventually implemented to accomplish this, but in the process of finding this solution several feasible, though less optimal, alternative trajectory sequences implementing the same procedure were discovered. This paper provides a descriptive comparison of these very different orbital profiles and serves to illustrate the utility and great flexibility of this orbital control procedure. Targeting methodology for finding constrained solutions in this space is also presented.

Muhonen, D.↗
NASA NTRS1984

Trajectory determination support and analysis for ISEE-3 from halo orbit to escape from the earth/moon system

The analyses performed in altering the ISEE-3 spacecraft path from a liberation point to a helicocentric orbit for intercepting the Giacobini-Zimmer cometary tail are reviewed. The initial calculations considered the expected accuracy, the best temporal lengths to be used for the calculations and the maneuver points. The early maneuvers were also constrained to a maximum number of crossings of the terrestrial magnetotail for data collection purposes. Three earth-based tracking stations trajectory data collection schedules were projected, and programs were prepared for comparing tracking data with predictions. Delta- V maneuvers were set for perigee locations in order to conserve fuel. A 21-day span was selected for tracking, expect during maneuver periods. Accuracies of 0.1-10 km and 0.3-2.0 cm/sec were obtained.

Joyce, J. B.↗