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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 181 records · Page 10
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NASA NTRS1989

X-ray-selected candidates for the RS CVn and W UMa classes of binary stars

X-ray luminosity, spectral type, radial-velocity variation, rotationally broadened line profile, and Ca II H and K line emission data are used to identify 12 new candidates for the RS CVn class and seven new candidates for the W UMa class from spectroscopic binaries which are contained in the Einstein Extended Medium Sensitivity Survey. Under the assumption that the candidates are genuine members of each class, local space density estimates of 4.47 + or - 1.19 x 10 to the -4th/cu pc for RS CVn binaries and 8.47 + or - 3.00 x 10 to the -5th/cu pc for W UMa binaries are found. Although the density estimate for the W UMa binaries is shown to be consistent with previous estimates obtained from optically selected samples, the estimate for the RS CVn binaries is more than an order of magnitude greater than previously determined space densities.

Fleming, Thomas A.↗
NASA NTRS1989

Tropical forest biomass and successional age class relationships to a vegetation index derived from Landsat TM data

Forest stand structure and biomass data were collected using conventional forest inventory techniques in tropical, subtropical, and warm temperate forest biomes. The feasibility of detecting tropical forest successional age class and total biomass differences using Landsat-Thematic mapper (TM) data, was evaluated. The Normalized Difference Vegetation Index (NDVI) calculated from Landsat-TM data were not significantly correlated with forest regeneration age classes in the mountain terrain of the Luquillo Experimental Forest, Puerto Rico. The low sun angle and shadows cast on steep north and west facing slopes reduced spectral reflectance values recorded by TM orbital altitude. The NDVI, calculated from low altitude aircraft scanner data, was significatly correlated with forest age classes. However, analysis of variance suggested that NDVI differences were not detectable for successional forests older than approximately 15-20 years. Also, biomass differences in young successional tropical forest were not detectable using the NDVI. The vegetation index does not appear to be a good predictor of stand structure variables (e.g., height, diameter of main stem) or total biomass in uneven age, mixed broadleaf forest. Good correlation between the vegetation index and low biomass in even age pine plantations were achieved for a warm temperate study site. The implications of the study for the use of NDVI for forest structure and biomass estimation are discussed.

Sader, Steven A.↗
NASA NTRS1989

Distribution of taxonomic classes and the compositional structure of the asteroid belt

This paper reviews previous studies on the distribution of the asteroid taxonomic classes and analyzes the techniques, results, and interpretations of these studies, with special attention given to the strong and weak points of these studies and the important caveat for their interpretation. It is concluded that, in spite of the differences in class definition, the rather ordered heliocentric distribution of the composition is real and must be due to either primordial, evolutionary, or dynamical processes, or to a combination of all three. In general, the distribution of asteroid taxonomic classes is characterized by moderate-albedo asteroids dominant in the inner asteroid belt, and low-albedo asteroids prevalent in the outer belt and beyond.

Gradie, Jonathan C.↗
NASA NTRS1991

A theory of photometric stereo for a class of diffuse non-Lambertian surfaces

A theory of photometric stereo is proposed for a large class of non-Lambertian reflectance maps. The authors review the different reflectance maps proposed in the literature for modeling reflection from real-world surfaces. From this, they obtain a mathematical class of reflectance maps to which the maps belong. They show that three lights can be sufficient for a unique inversion of the photometric stereo equation for the entire class of reflectance maps. They also obtain a constraint on the positions of light sources for obtaining this solution. They investigate the sufficiency of three light sources to estimate the surface normal and the illuminant strength. The issue of completeness of reconstruction is addressed. They shown that if k lights are sufficient for a unique inversion, 2k lights are necessary for a complete inversion.

Tagare, Hemant D.↗
NASA NTRS1929

Drag of C-Class Airship Hulls of Various Fineness Ratios

This report presents the results of wind-tunnel tests on eight C-class airship hulls with various fineness ratios, conducted in the Navy Aerodynamic Laboratory, Washington. The purpose of the tests was to determine the variation of resistance with fineness ratio, and also to find the pressure and friction elements of the total drag for the model having the least shape coefficient. Seven C-class airship hulls with fineness ratios of 1.0, 1.5, 2.0, 3.0, 6.0, 8.0, and 10.0 were made and verified. These models and also the previously constructed original C-class hull, whose fineness ratio is 4.62, were then tested in the 8 by 8 foot tunnel for drag of 0 degree pitch and yaw, at various wind speeds. The original hull, which was found to have the least shape coefficient, was then tested for pressure distribution over the surface at various wind speeds. (author)

Zahm, A F↗
NASA NTRS1994

Towards a class library for mission planning

The PASTEL Mission Planning System (MPS) has been developed in C++ using an object-oriented (OO) methodology. While the scope and complexity of this system cannot compare to that of an MPS for a complex mission one of the main considerations of the development was to ensure that we could reuse some of the classes in future MPS. We present here PASTEL MPS classes which could be used in the foundations of a class library for MPS.

Pujo, Oliver↗
NASA NTRS1995

A class of stabilizing controllers for flexible multibody systems

The problem of controlling a class of nonlinear multibody flexible space systems consisting of a flexible central body to which a number of articulated appendages are attached is considered. Collocated actuators and sensors are assumed, and global asymptotic stability of such systems is established under a nonlinear dissipative control law. The stability is shown to be robust to unmodeled dynamics and parametric uncertainties. For a special case in which the attitude motion of the central body is small, the system, although still nonlinear, is shown to be stabilized by linear dissipative control laws. Two types of linear controllers are considered: static dissipative (constant gain) and dynamic dissipative. The static dissipative control law is also shown to provide robust stability in the presence of certain classes of actuator and sensor nonlinearities and actuator dynamics. The results obtained for this special case can also be readily applied for controlling single-body linear flexible space structures. For this case, a synthesis technique for the design of a suboptimal dynamic dissipative controller is also presented. The results obtained in this paper are applicable to a broad class of multibody and single-body systems such as flexible multilink manipulators, multipayload space platforms, and space antennas. The stability proofs use the Lyapunov approach and exploit the inherent passivity of such systems.

Joshi, Suresh M.↗
NASA NTRS1995

Rocket-based combined-cycle (RBCC) powered spaceliner class vehicle can advantageously employ vertical takeoff and landing (VTOL)

The subject is next generation orbital space transporation, taken to be fully reusable non-staged 'aircraft like' systems targeted for routine, affordable access to space. Specifically, the takeoff and landing approach to be selected for such systems is considered, mainly from a propulsion viewpoint. Conventional wisdom has it that any transatmospheric-class vehicle which uses high-speed airbreathing propulsion modes (e.g., scramjet) intrinsically must utilize horizontal takeoff and landing, HTOHL. Although this may be true for all-airbreathing propulsion (i.e., no rocket content as in turboramjet propulsion), that emerging class of powerplant which integrally combines airbreathing and rocket propulsion, referred to as rocket-based combined-cycle (RBCC) propulsion, is considerably more flexible with respect to selecting takeoff/landing modes. In fact, it is proposed that any of the modes of interest may potentially be selected: HTOHL, VTOHL, VTOVL. To illustrate this surmise, the case of a previously documented RBCC-powered 'Spaceliner' class space transport concept, which is designed for vertical takeoff and landing, is examined. The 'RBCC' and 'Spaceliner' categories are first described for background. Departing form an often presumed HTOHL baseline, the leading design and operational advantages of moving to VTOVL are then elucidated. Technical substantiation that the RBCC approach, in fact, enables this capability (but also that of HTOHL and VTOVL) is provided, with extensive reference to case-in-point supporting studies. The paper closes with a set of conditional surmises bearing on its set of conclusions, which point up the operational cost advantages associated with selecting the vertical takeoff and landing mode combination (VTOL), uniquely offered by RBCC propulsion.

Escher, William J. D.↗
NASA NTRS1996

The Total Gaussian Class of Quasiprobabilities and its Relation to Squeezed-State Excitations

The class of quasiprobabilities obtainable from the Wigner quasiprobability by convolutions with the general class of Gaussian functions is investigated. It can be described by a three-dimensional, in general, complex vector parameter with the property of additivity when composing convolutions. The diagonal representation of this class of quasiprobabilities is connected with a generalization of the displaced Fock states in direction of squeezing. The subclass with real vector parameter is considered more in detail. It is related to the most important kinds of boson operator ordering. The properties of a specific set of discrete excitations of squeezed coherent states are given.

Wuensche, Alfred↗
NASA NTRS2000

Artificial Gravity as a Multi-System Countermeasure for Exploration Class Space Flight Missions

NASA's vision for space exploration includes missions of unprecedented distance and duration. However, during 30 years of human space flight experience, including numerous long-duration missions, research has not produced any single countermeasure or combination of countermeasures that is completely effective. Current countermeasures do not fully protect crews in low-Earth orbit, and certainly will not be appropriate for crews journeying to Mars and back over a three-year period. The urgency for exploration-class countermeasures is compounded by continued technical and scientific successes that make exploration class missions increasingly attractive. The critical and possibly fatal problems of bone loss, cardiovascular deconditioning, muscle weakening, neurovestibular disturbance, space anemia, and immune compromise may be alleviated by the appropriate application of artificial gravity (AG). However, despite a manifest need for new countermeasure approaches, concepts for applying AG as a countermeasure have not developed apace. To explore the utility of AG as a multi-system countermeasure during long-duration, exploration-class space flight, eighty-three members of the international space life science and space flight community met earlier this year. They concluded unanimously that the potential of AG as a multi-system countermeasure is indeed worth pursuing, and that the requisite AG research needs to be supported more systematically by NASA. This presentation will review the issues discussed and recommendations made.

Paloski, William H.↗
NASA NTRS2008

Limits to Open Class Performance?

This presentation discusses open or unlimited class aircraft performance limitations and design solutions. Limitations in this class of aircraft include slow climbing flight which requires low wing loading, high cruise speed which requires high wing loading, gains in induced or viscous drag alone which result in only half the gain overall and other structural problems (yaw inertia and spins, flutter and static loads integrity). Design solutions include introducing minimum induced drag for a given span (elliptical span load or winglets) and introducing minimum induced drag for a bell shaped span load. It is concluded that open class performance limits (under current rules and technologies) is very close to absolute limits, though some gains remain to be made from unexplored areas and new technologies.

Bowers, Albion H.↗
NASA NTRS2006

X-Windows Information Sharing Protocol Widget Class

The X-Windows Information Sharing Protocol (ISP) Widget Class ("Class") is used here in the object-oriented-programming sense of the word) was devised to simplify the task of implementing ISP graphical-user-interface (GUI) computer programs. ISP programming tasks require many method calls to identify, query, and interpret the connections and messages exchanged between a client and an ISP server. Most X-Windows GUI programs use widget sets or toolkits to facilitate management of complex objects. The widget standards facilitate construction of toolkits and application programs. The X-Windows Information Sharing Protocol (ISP) Widget Class encapsulates the client side of the ISP programming libraries within the framework of an X-Windows widget. Using the widget framework, X-Windows GUI programs can interact with ISP services in an abstract way and in the same manner as that of other graphical widgets, making it easier to write ISP GUI client programs. Wrapping ISP client services inside a widget framework enables a programmer to treat an ISP server interface as though it were a GUI. Moreover, an alternate subclass could implement another communication protocol in the same sort of widget.

Barry, Matthew R.↗
NASA NTRS2006

X-Windows Socket Widget Class

The X-Windows Socket Widget Class ("Class" is used here in the object-oriented-programming sense of the word) was devised to simplify the task of implementing network connections for graphical-user-interface (GUI) computer programs. UNIX Transmission Control Protocol/Internet Protocol (TCP/IP) socket programming libraries require many method calls to configure, operate, and destroy sockets. Most X Windows GUI programs use widget sets or toolkits to facilitate management of complex objects. The widget standards facilitate construction of toolkits and application programs. The X-Windows Socket Widget Class encapsulates UNIX TCP/IP socket-management tasks within the framework of an X Windows widget. Using the widget framework, X Windows GUI programs can treat one or more network socket instances in the same manner as that of other graphical widgets, making it easier to program sockets. Wrapping ISP socket programming libraries inside a widget framework enables a programmer to treat a network interface as though it were a GUI.

Barry, Matthew R.↗
NASA NTRS2011

Sparse Solutions for Single Class SVMs: A Bi-Criterion Approach

In this paper we propose an innovative learning algorithm - a variation of One-class nu Support Vector Machines (SVMs) learning algorithm to produce sparser solutions with much reduced computational complexities. The proposed technique returns an approximate solution, nearly as good as the solution set obtained by the classical approach, by minimizing the original risk function along with a regularization term. We introduce a bi-criterion optimization that helps guide the search towards the optimal set in much reduced time. The outcome of the proposed learning technique was compared with the benchmark one-class Support Vector machines algorithm which more often leads to solutions with redundant support vectors. Through out the analysis, the problem size for both optimization routines was kept consistent. We have tested the proposed algorithm on a variety of data sources under different conditions to demonstrate the effectiveness. In all cases the proposed algorithm closely preserves the accuracy of standard one-class nu SVMs while reducing both training time and test time by several factors.

Das, Santanu↗
NASA NTRS2006

X-Windows PVT Widget Class

The X-Windows Process Validation Table (PVT) Widget Class ( Class is used here in the object-oriented-programming sense of the word) was devised to simplify the task of implementing network registration services for Information Sharing Protocol (ISP) graphical-user-interface (GUI) computer programs. Heretofore, ISP PVT programming tasks have required many method calls to identify, query, and interpret the connections and messages exchanged between a client and a PVT server. Normally, programmers have utilized direct access to UNIX socket libraries to implement the PVT protocol queries, necessitating the use of many lines of source code to perform frequent tasks. Now, the X-Windows PVT Widget Class encapsulates ISP client server network registration management tasks within the framework of an X Windows widget. Use of the widget framework enables an X Windows GUI program to interact with PVT services in an abstract way and in the same manner as that of other graphical widgets, making it easier to program PVT clients. Wrapping the PVT services inside the widget framework enables a programmer to treat a PVT server interface as though it were a GUI. Moreover, an alternate subclass could implement another service in a widget of the same type. This program was written by Matthew R. Barry of United Space Alliance for Johnson Space Center. For further information, contact the Johnson Technology Transfer Office at (281) 483-3809. MSC-23582 Shuttle Data Center File- Processing Tool in Java A Java-language computer program has been written to facilitate mining of data in files in the Shuttle Data Center (SDC) archives. This program can be executed on a variety of workstations or via Web-browser programs. This program is partly similar to prior C-language programs used for the same purpose, while differing from those programs in that it exploits the platform-neutrality of Java in implementing several features that are important for analysis of large sets of time-series data. The program supports regular expression queries of SDC archive files, reads the files, interleaves the time-stamped samples according to a chosen output, then transforms the results into that format. A user can choose among a variety of output file formats that are useful for diverse purposes, including plotting, Markov modeling, multivariate density estimation, and wavelet multiresolution analysis, as well as for playback of data in support of simulation and testing.

Barry, Matthew R.↗
NASA NTRS2013

Kilowatt-Class Fission Power Systems for Science and Human Precursor Missions

Nuclear power provides an enabling capability for NASA missions that might otherwise be constrained by power availability, mission duration, or operational robustness. NASA and the Department of Energy (DOE) are developing fission power technology to serve a wide range of future space uses. Advantages include lower mass, longer life, and greater mission flexibility than competing power system options. Kilowatt-class fission systems, designated "Kilopower," were conceived to address the need for systems to fill the gap above the current 100-W-class radioisotope power systems being developed for science missions and below the typical 100-k We-class reactor power systems being developed for human exploration missions. This paper reviews the current fission technology project and examines some Kilopower concepts that could be used to support future science missions or human precursors.

Flexibility↗
NASA NTRS2014

Interannual Variation in Phytoplankton Class-Specific Primary Production at a Global Scale

We used the NASA Ocean Biogeochemical Model (NOBM) combined with remote sensing data via assimilation to evaluate the contribution of 4 phytoplankton groups to the total primary production. First we assessed the contribution of each phytoplankton groups to the total primary production at a global scale for the period 1998-2011. Globally, diatoms were the group that contributed the most to the total phytoplankton production (50, the equivalent of 20 PgC y-1. Coccolithophores and chlorophytes each contributed to 20 (7 PgC y-1 of the total primary production and cyanobacteria represented about 10 (4 PgC y(sub-1) of the total primary production. Primary production by diatoms was highest in high latitude (45) and in major upwelling systems (Equatorial Pacific and Benguela system). We then assessed interannual variability of this group-specific primary production over the period 1998-2011. Globally the annual relative contribution of each phytoplankton groups to the total primary production varied by maximum 4 (1-2 PgC y-1. We assessed the effects of climate variability on the class-specific primary production using global (i.e. Multivariate El Nio Index, MEI) and regional climate indices (e.g. Southern Annular Mode (SAM), Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO)). Most interannual variability occurred in the Equatorial Pacific and was associated with climate variability as indicated by significant correlation (p 0.05) between the MEI and the class-specific primary production from all groups except coccolithophores. In the Atlantic, climate variability as indicated by NAO was significantly correlated to the primary production of 2 out of the 4 groups in the North Central Atlantic (diatomscyanobacteria) and in the North Atlantic (chlorophytes and coccolithophores). We found that climate variability as indicated by SAM had only a limited effect on the class-specific primary production in the Southern Ocean. These results provide a modeling and data assimilation perspective to phytoplankton partitioning of primary production and contribute to our understanding of the dynamics of the carbon cycle in the oceans at a global scale.

Chl-a↗
NASA NTRS2008

Mission Architecture and Technology Options for a Flagship Class Venus In Situ Mission

Venus, as part of the inner triad with Earth and Mars, represents an important exploration target if we want to learn more about solar system formation and evolution. Comparative planetology could also elucidate the differences between the past, present, and future of these three planets, and can help with the characterization of potential habitable zones in our solar system and, by extension, extrasolar systems. A long lived in situ Venus mission concept, called the Venus Mobile Explorer, was prominently featured in NASA's 2006 SSE Roadmap and supported in the community White Paper by the Venus Exploration Analysis Group (VEXAG). Long-lived in situ missions are expected to belong to the largest (Flagship) mission class, which would require both enabling and enhancing technologies beside mission architecture options. Furthermore, extreme environment mitigation technologies for Venus are considered long lead development items and are expected to require technology development through a dedicated program. To better understand programmatic and technology needs and the motivating science behind them, in this fiscal year (FY08) NASA is funding a Venus Flaghip class mission study, based on key science and technology drivers identified by a NASA appointed Venus Science and Technology Definition Team (STDT). These mission drivers are then assembled around a suitable mission architecture to further refine technology and cost elements. In this paper we will discuss the connection between the final mission architecture and the connected technology drivers from this NASA funded study, which - if funded - could enable a future Flagship class Venus mission and potentially drive a proposed Venus technology development program.

Balint, Tibor S.↗