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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

A new component of cosmic rays of unknown origin at a few MeV per nucleon

Recently discovered anomalies in the abundances and energy spectra of quiet time, extraterrestrial hydrogen, helium, carbon, nitrogen, and oxygen require serious revisions of origin theories to account for this new component of cosmic radiation. Abnormally large O/C and N/C ratios, long term intensity variations with time, and radial gradient measurements indicate a non-solar origin for these 2 to 30 MeV/nucleon particles. Ideas suggested to explain these measurements range from acceleration of galactic source material having an unusual composition to local acceleration of particles within the solar cavity. Observations are at present insufficient to choose between these alternate origin models.

Gloecker, G.↗
NASA NTRS1975

Composition and energy spectra of heavy nuclei of unknown origin detected on Skylab

At the orbit of Skylab, steeply falling energy spectra of nuclei with atomic numbers of at least 8 and energies between about 10 and 40 MeV/amu at intensities much higher than seen outside the magnetosphere were observed. The composition is consistent with that of the solar corona. It is suggested that heavy solar-wind ions enter the magnetosphere, are accelerated, and populate the inner radiation belt.

Chan, J. H.↗
NASA NTRS1975

Composition and energy spectra of heavy nuclei of unknown origin detected on Skylab

Lexan track detectors with large collecting power were exposed inside and outside Skylab during late 1973 and early 1974. Steeply falling energy spectra of nuclei with Z greater than or equal to 8 and energies between 10 and 40 MeV were observed at intensities much higher than those observed outside the magnetosphere. Four possible sources (solar flare particles; low-energy cosmic rays; the anomalous component of low-energy cosmic rays; particles trapped in the inner Van Allen belt) are examined using Skylab particle flux data outside the magnetosphere and other measurements. The composition is found to be most consistent with that of the solar corona. It is suggested that heavy solar wind ions enter the magnetosphere, are accelerated, and populate the inner radiation belt.

Chan, J. H.↗
NASA NTRS1976

Charge coupled device integration-time coding for detection of images moving with unknown velocities

Existing techniques for the detection of a moving low light level image by a CCD array have required velocity synchronism between the image and the photogenerated charges. This was necessary to prevent blurring during the long duration of charge integration. A new detection scheme is described which causes the image to be convolved with a clock modulation signal as the photocharges are collected. The charge accumulating from each image point will now be spread over many photoelements due to the absence of velocity synchronism, but the output is not blurred in the usual sense. Instead the charge is distributed through the array in a controlled way so that the image can be reconstructed.

White, J. M.↗
NASA NTRS1979

Radar observation of known and unknown clear echoes

Target cross-section as a function of wavelength for known insects, known bird, and dot targets is presented. Tracking data using the time series analysis was tabulated for known birds. Examples were selected from these early works to give entomologists some indication of the types of information that are available by radar as well as examples of the different sources of clear-air radar backscatter.

Glover, K. M.↗
NASA NTRS1980

The remaining large minor planets with unknown rotational properties - 31 Euphrosyne and 65 Cybele

Photoelectric photometry results are presented for 31 Euphrosyne and 65 Cybele. The rational properties of the asteroids were found to be quite similar, both in period and maximum amplitude. Evidence was found for an opposition effect for 65 Cybele. The B-V and U-B colors were determined to be plus 0.67 and plus 0.30 for 31 Euphrosyne, plus 0.73 and plus 0.23 for 65 Cybele. Recent observations of 65 Cybele occulting a star have shown evidence of a possible satellite for this minor planet.

Schober, H. J.↗
NASA NTRS1981

1979J3 - Discovery of a previously unknown satellite of Jupiter

During a detailed search of Voyager 1 frames for additional observations of the satellite 1979J1, two small dark spots were observed in transit in several consecutive wide-angle frames of the Jovian atmosphere. The size, spacing, and motion of these pairs of dark spots indicated that they were the images of 1979J1 and its shadow. Subsequent analysis of images spanning 6 days, however, proved that the satellite observed in these Voyager 1 frames would have been occulted by Jupiter at the times of the Voyager 2 images of 1979J1 and was, therefore, a new satellite. It was subsequently found in transit on Voyager 2 images within 13 deg of the Voyager 1 prediction. Its period is 7 hrs 4 min 30 sec + or - 3 sec, and its mean distance is 1.793 Jupiter radii (Jupiter radius = 71,400 km). The observable profile appears to be roughly circular with a diameter of 40 km, and the albedo is approximately 0.05, similar to Amalthea's.

Synnott, S. P.↗
NASA NTRS1992

Ulysses operations at Jupiter - Planning for the unknown

The operational preparations for the Ulysses encounter with Jupiter are described with particular attention given to requirements for survival in the Jovian environment, ground-segment planning, a deep-space network, and encounter activities. It is concluded that the successful operation of the Ulysses spacecraft at Jupiter was the culmination of many years of activity, from spacecraft design and mission planning to the coordination of the encounter activities and production of the detailed timeline.

Angold, N.↗
NASA NTRS1995

Exploring the Unknown: Selected Documents in the History of the US Civil Space Program: Organizing for Exploration - Volume 1

A selection of key documents in the history of the U.S. civil space program is presented. This volume deals with organizational developments of the space program. More than 200 documents are printed. Each is introduced by a headnote providing context, bibliographical information, and background information necessary to understanding the document. These are organized into four major sections, each beginning with an introductory essay that keys the documents to major events in the history of the space program.

Logsdon, John M.↗
NASA NTRS1996

Analysis of condensation on a horizontal cylinder with unknown wall temperature and comparison with the Nusselt model of film condensation

Theoretical analysis and numerical computations are performed to set forth a new model of film condensation on a horizontal cylinder. The model is more general than the well-known Nusselt model of film condensation and is designed to encompass all essential features of the Nusselt model. It is shown that a single parameter, constructed explicitly and without specification of the cylinder wall temperature, determines the degree of departure from the Nusselt model, which assumes a known and uniform wall temperature. It is also known that the Nusselt model is reached for very small, as well as very large, values of this parameter. In both limiting cases the cylinder wall temperature assumes a uniform distribution and the Nusselt model is approached. The maximum deviations between the two models is rather small for cases which are representative of cylinder dimensions, materials and conditions encountered in practice.

Bahrami, Parviz A.↗
NASA NTRS1996

Exploring the Unknown: Selected Documents in the History of the U.S. Civilian Space Program: External Relationships - Volume 2

The documents selected for inclusion in this volume are presented in three chapters, each covering a particular aspect of the evolution of U.S. space exploration. These chapters address (1) the relations between the civilian space program of the United States and the space activities of other countries, (2) the relations between the U.S. civilian space program and the space efforts of national security organizations and the military, and (3) NASA's relations with industry and academic institutions.

Logsdon, John M.↗
NASA NTRS1998

Predictive Feedback and Feedforward Control for Systems with Unknown Disturbances

Predictive feedback control has been successfully used in the regulation of plate vibrations when no reference signal is available for feedforward control. However, if a reference signal is available it may be used to enhance regulation by incorporating a feedforward path in the feedback controller. Such a controller is known as a hybrid controller. This paper presents the theory and implementation of the hybrid controller for general linear systems, in particular for structural vibration induced by acoustic noise. The generalized predictive control is extended to include a feedforward path in the multi-input multi-output case and implemented on a single-input single-output test plant to achieve plate vibration regulation. There are cases in acoustic-induce vibration where the disturbance signal is not available to be used by the hybrid controller, but a disturbance model is available. In this case the disturbance model may be used in the feedback controller to enhance performance. In practice, however, neither the disturbance signal nor the disturbance model is available. This paper presents the theory of identifying and incorporating the noise model into the feedback controller. Implementations are performed on a test plant and regulation improvements over the case where no noise model is used are demonstrated.

Juang, Jer-Nan↗
NASA NTRS1999

Exploring the Unknown: Selected Documents in the History of the U.S. Civil Space Program: Accessing Space - Volume 4

The documents selected for inclusion in this volume are presented in four major chapters, each covering a particular aspect of access to space and the manner in which it has developed over time. These chapters focus on the evolution toward the giant Saturn V rocket, the development of the Space Shuttle, space transportation commercialization, and future space transportation possibilities. Each chapter in this volume is introduced by an overview essay, prepared by individuals who are particularly well qualified to write on the topic. In the main, these essays are intended to introduce and complement the documents in the chapter and to place them, for the most part, in a chronological and substantive context. Each essay contains references to the documents in the chapter it introduces, and many also contain references to documents in other chapters of the collection. These introductory essays are the responsibility of their individual authors, and the views and conclusions contained therein do not necessarily represent the opinions of either George Washington University or NASA.

Logsdon, John M.↗
NASA NTRS2001

A Coupled Nonlinear Spacecraft Attitude Controller/Observer With an Unknown Constant Gyro Bias

A nonlinear control scheme for attitude control of a spacecraft is combined with a nonlinear gyro bias observer for the case of constant gyro bias. The closed loop system is proven to be globally stable, with zero tracking error, thus proving a separation principle for the given system. The nonlinear observer incorporates persistency of excitation, resulting in exponential convergence of the gyro bias error.

Deutschmann, Julie↗
NASA NTRS2001

Exploring the Unknown: Selected Documents in the History of the US Civil Space Program: Exploring the Cosmos - Volume 5

The documents selected for inclusion in this volume are presented in three major sections, each covering a particular aspect of the origins, evolution, and execution of the US space science program. Chapter 1 deals with the origins, evolution, and organization of the space science program. Chapter 2 deals with the solar system exploration. Chapter 3 deals with NASA's astronomy and astrophysics efforts. Each chapter in the present volume is introduced by an overview essay. In the main, these essays are intended to introduce and complement the documents in the chapter and to place them in a chronological and substantive context. Each essay contains references to the documents in the chapter it introduces, and may also contain references to documents in other chapters of the collection

Logsdon, John M.↗
NASA NTRS2001

A Nonlinear Spacecraft Attitude Controller and Observer with an Unknown Constant Gyro Bias and Gyro Noise

A nonlinear control scheme for attitude control of a spacecraft is combined with a nonlinear gyro bias observer for the case of constant gyro bias, in the presence of gyro noise. The observer bias estimates converge exponentially to a mean square bound determined by the standard deviation of the gyro noise. The resulting coupled, closed loop dynamics are proven to be globally stable, with asymptotic tracking which is also mean square bounded. A simulation of the proposed observer-controller design is given for a rigid spacecraft tracking a specified, time-varying attitude sequence to illustrate the theoretical claims.

Deutschmann, Julie↗
NASA NTRS2002

A Coupled Nonlinear Spacecraft Attitude Controller and Observer with an Unknown Gyro Misalignment and Gyro Bias

A nonlinear control scheme for attitude control of a spacecraft is combined with a nonlinear gyro misalignment and bias observer for the case of constant gyro misalignment and bias. A persistency of excitation analysis shows the observer gyro bias estimates converge to the true bias values exponentially fast. The convergence of the misalignment estimates is also presented. Then; the resulting coupled, closed loop dynamics are proven by a Lyapunov analysis to be globally stable, with asymptotically perfect tracking. The analysis is extended to consider the effects of noise in addition to the gyro misalignment and bias. A simulation of the proposed observer-controller design is given for a rigid spacecraft tracking a specified, time-varying attitude sequence to illustrate the theoretical claims.

Thienel, Julie↗