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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Ultrasonic nondestructive evaluation, microstructure, and fracture toughness interrelations

Ultrasonic techniques for mechanical property characterizations are reviewed and conceptual models are advanced for explaining and interpreting the empirically based results. At present, the technology is generally empirically based and is emerging from the research laboratory. Advancement of the technology will require establishment of theoretical foundations for the experimentally observed interrelations among ultrasonic measurements, mechanical properties, and microstructure. Conceptual models are applied to ultrasonic assessment of fracture toughness to illustrate an approach for predicting correlations found among ultrasonic measurements, microstructure, and mechanical properties.

Vary, Alex↗
NASA NTRSDate not supplied

NASA biological and physical sciences databases: who’s the FAIRest of them all?

Conceptual models are a key part of the foundation of scientific study. Scientific data discovery and retrieval are often inaccurate and incomplete because these models are not sufficiently well-incorporated into data retrieval systems. Systems often don’t provide the necessary tools to those producing scientific data to fully and unambiguously annotate them and the result is consumers of the data cannot find them efficiently. The capability of data archives to provide these tools to link data to underlying conceptual models is one of dimensions of the recently developed “FAIR” principles (https://www.go-fair.org/fair-principles/ ), and is key to many automated processes being able to operate on these data, particularly analytics involving artificial intelligence. We used an open-source web service to measure the FAIR compliance of the three data archives operated by NASA for the biological and physical sciences: the Life Sciences Data Archive, the Physical Sciences Informatics database, and GeneLab. The service ingests references to data sets in these archives, and then executes domain-non-specific examinations of these data and metadata that test compliance to the FAIR principles. Of the 22 metrics tested, GeneLab passed 11 (50%), and PSI and LSDA each passed 7 (32%). These data were gathered using only one representative data set from each archive and we anticipate variability in results as we continue to apply these metrics to other data. A preliminary study of the failure traces for each metric suggests there is a wide range of effort and complexity in the enhancements required for each system to elevate FAIR compliance, and this is the subject of continued investigation. This information has been and will likely continue to be important information in planning these enhancements, with the goal of increased readiness of the data for automated processes.

database↗
NASA NTRS1994

Integrating O/S models during conceptual design, part 3

Space vehicles, such as the Space Shuttle, require intensive ground support prior to, during, and after each mission. Maintenance is a significant part of that ground support. All space vehicles require scheduled maintenance to ensure operability and performance. In addition, components of any vehicle are not one-hundred percent reliable so they exhibit random failures. Once detected, a failure initiates unscheduled maintenance on the vehicle. Maintenance decreases the number of missions which can be completed by keeping vehicles out of service so that the time between the completion of one mission and the start of the next is increased. Maintenance also requires resources such as people, facilities, tooling, and spare parts. Assessing the mission capability and resource requirements of any new space vehicle, in addition to performance specification, is necessary to predict the life cycle cost and success of the vehicle. Maintenance and logistics support has been modeled by computer simulation to estimate mission capability and resource requirements for evaluation of proposed space vehicles. The simulation was written with Simulation Language for Alternative Modeling II (SLAM II) for execution on a personal computer. For either one or a fleet of space vehicles, the model simulates the preflight maintenance checks, the mission and return to earth, and the post flight maintenance in preparation to be sent back into space. THe model enables prediction of the number of missions possible and vehicle turn-time (the time between completion of one mission and the start of the next) given estimated values for component reliability and maintainability. The model also facilitates study of the manpower and vehicle requirements for the proposed vehicle to meet its desired mission rate. This is the 3rd part of a 3 part technical report.

Ebeling, Charles E.↗
NASA NTRS2010

Vehicle Sketch Pad: a Parametric Geometry Modeler for Conceptual Aircraft Design

The conceptual aircraft designer is faced with a dilemma, how to strike the best balance between productivity and fidelity? Historically, handbook methods have required only the coarsest of geometric parameterizations in order to perform analysis. Increasingly, there has been a drive to upgrade analysis methods, but these require considerably more precise and detailed geometry. Attempts have been made to use computer-aided design packages to fill this void, but their cost and steep learning curve have made them unwieldy at best. Vehicle Sketch Pad (VSP) has been developed over several years to better fill this void. While no substitute for the full feature set of computer-aided design packages, VSP allows even novices to quickly become proficient in defining three-dimensional, watertight aircraft geometries that are adequate for producing multi-disciplinary meta-models for higher order analysis methods, wind tunnel and display models, as well as a starting point for animation models. This paper will give an overview of the development and future course of VSP.

Hahn, Andrew S.↗
NASA NTRS2006

Architecting Ourselves: Schema to Facilitate Growth of the International Space Architecture Community

This paper develops a conceptual model, adapted from the way research and development non-profits and universities tend to be organized, that could help amplify the reach and effectiveness of the international space architecture community. The model accommodates current activities and published positions, and increases involvement by allocating accountability for necessary professional and administrative activities. It coordinates messaging and other outreach functions to improve brand management. It increases sustainability by balancing volunteer workload. And it provides an open-ended structure that can be modified gracefully as needs, focus, and context evolve. Over the past 20 years, Space Architecture has attained some early signs of legitimacy as a discipline: an active, global community of practicing and publishing professionals; university degree programs; a draft undergraduate curriculum; and formal committee establishment within multiple professional organizations. However, the nascent field has few outlets for expression in built architecture, which exacerbates other challenges the field is experiencing in adolescence: obtaining recognition and inclusion as a unique contributor by the established aerospace profession; organizing and managing outreach by volunteers; striking a balance between setting admittance or performance credentials and attaining a critical mass of members; and knowing what to do, beyond sharing common interests, to actually increase the market demand for space architecture. This paper develops a conceptual model, adapted from the way research-anddevelopment non-profits and universities tend to be organized, that could help amplify the reach and effectiveness of the international space architecture community. The model accommodates current activities and published positions, and increases involvement by allocating accountability for necessary professional and administrative activities. It coordinates messaging and other outreach functions to improve brand management. It increases sustainability by balancing volunteer workload. And it provides an open-ended structure that can be modified gracefully as needs, focus, and context evolve. This organizational model is offered up for consideration, debate, and toughening by the space architecture community at large.

space architecure↗
NASA NTRS1991

Propellant-remaining modeling

A successful satellite mission is predicted upon the proper maintenance of the spacecraft's orbit and attitude. One requirement for planning and predicting the orbit and attitude is the accurate estimation of the propellant remaining onboard the spacecraft. Focuss is on the three methods that were developed for calculating the propellant budget: the errors associated with each method and the uncertainties in the variables required to determine the propellant remaining that contribute to these errors. Based on these findings, a strategy is developed for improved propellant-remaining estimation. The first method is based on Boyle's law, which related the values of pressure, volume, and temperature (PVT) of an ideal gas. The PVT method is used for the monopropellant and the bipropellant engines. The second method is based on the engine performance tests, which provide data that relate thrust and specific impulse associated with a propellant tank to that tank's pressure. Two curves representing thrust and specific impulse as functions of pressure are then generated using a polynomial fit on the engine performance data. The third method involves a computer simulation of the propellant system. The propellant flow is modeled by creating a conceptual model of the propulsion system configuration, taking into account such factors as the propellant and pressurant tank characteristics, thruster functionality, and piping layout. Finally, a thrust calibration technique is presented that uses differential correction with the computer simulation method of propellant-remaining modeling. Thrust calibration provides a better assessment of thruster performance and therefore enables a more accurate estimation of propellant consumed during a given maneuver.

Torgovitsky, S.↗
NASA NTRS2015

Open-Source Conceptual Sizing Models for the Hyperloop Passenger Pod

Hyperloop is a new mode of transportation proposed as an alternative to California's high speed rail project, with the intended benefits of higher performance at lower overall costs. It consists of a passenger pod traveling through a tube under a light vacuum and suspended on air bearings. The pod travels up to transonic speeds resulting in a 35 minute travel time between the intended route from Los Angeles and San Francisco. Of the two variants outlined, the smaller system includes a 1.1 meter tall passenger capsule traveling through a 2.2 meter tube at 700 miles per hour. The passenger pod features water-based heat exchangers as well as an on-board compression system that reduces the aerodynamic drag as it moves through the tube. Although the original proposal looks very promising, it assumes that tube and pod dimensions are independently sizable without fully acknowledging the constraints of the compressor system on the pod geometry. This work focuses on the aerodynamic and thermodynamic interactions between the two largest systems; the tube and the pod. Using open-source toolsets, a new sizing method is developed based on one-dimensional thermodynamic relationships that accounts for the strong interactions between these sub-systems. These additional considerations require a tube nearly twice the size originally considered and limit the maximum pod travel speed to about 620 miles per hour. Although the results indicate that Hyperloop will need to be larger and slightly slower than originally intended, the estimated travel time only increases by approximately five minutes, so the overall performance is not dramatically affected. In addition, the proposed on-board heat exchanger is not an ideal solution to achieve reasonable equilibrium air temperatures within the tube. Removal of this subsystem represents a potential reduction in weight, energy requirements and complexity of the pod. In light of these finding, the core concept still remains a compelling possibility, although additional engineering and economic analyses are markedly necessary before a more complete design can be developed.

design analysis↗
NASA NTRS1972

A three stage sampling model for remote sensing applications

A conceptual model and an empirical application of the relationship between the manner of selecting observations and its effect on the precision of estimates from remote sensing are reported. This three stage sampling scheme considers flightlines, segments within flightlines, and units within these segments. The error of estimate is dependent on the number of observations in each of the stages.

Eisgruber, L. M.↗
NASA NTRS2000

A Dynamical Model for The Jupiter Thermocline

A new conceptual model for the observed banded wind structure of the giant outer planets is proposed, assuming a smoothly distributed potential vorticity (PV) atop a layer of deeply seated, latitudinally variable stratification. With a vanishing horizontal entropy contrast presumably enforced at the bottom of the flow layer by the underlying convection, the thermal-wind balance of observed cloud-top motions implies a mapping of constant potential temperature surfaces, nearly vertical at upper tropospheric levels, down to a deeper, flatter, but variably sloped 'thermocline.' For a generally colder-poleward distribution of isentropes consistent with the strong equatorial jets of both Jupiter and Saturn, this kind of mapping would also imply a poleward decreasing static stability. The proposed temperature-stability distribution is just the reverse of the Earth's troposphere, where the strongest latitudinal potential temperature gradients are at the bottom instead of the top, with static stability generally increasing toward the pole. The warmer-stabler correlation for Jupiter would be consistent, however, with a nearly monotonic distribution of PV from low to high latitudes, over planetary scales for which the planetary vorticity dominates the relative vorticity of the jets. In this way efficient PV mixing for the isentropically bounded thermocline can account for the dynamical maintenance of the cyclonic flanks of the equatorial jet. Over latitudinal intervals comparable to the internal deformation scale, however, the gradient of the absolute vorticity is dominated by the flow curvature, with the local latitudinal gradient of the static stability proportional to the local potential temperature gradient and therefore the local variation in geostrophic velocity. The resulting correlation of velocities and vorticity gradients implies an alternation of the flow over the internal deformation radius set by the vertical entropy contrast.

Allison, Michael↗
NASA NTRS2003

Observed and Modeled Trends in Southern Ocean Sea Ice

Conceptual models and global climate model (GCM) simulations have both indicated the likelihood of an enhanced sensitivity to climate change in the polar regions, derived from the positive feedbacks brought about by the polar abundance of snow and ice surfaces. Some models further indicate that the changes in the polar regions can have a significant impact globally. For instance, 37% of the temperature sensitivity to a doubling of atmospheric CO2 in simulations with the GCM of the Goddard Institute for Space Studies (GISS) is attributable exclusively to inclusion of sea ice variations in the model calculations. Both sea ice thickness and sea ice extent decrease markedly in the doubled CO, case, thereby allowing the ice feedbacks to occur. Stand-alone sea ice models have shown Southern Ocean hemispherically averaged winter ice-edge retreats of 1.4 deg latitude for each 1 K increase in atmospheric temperatures. Observations, however, show a much more varied Southern Ocean ice cover, both spatially and temporally, than many of the modeled expectations. In fact, the satellite passive-microwave record of Southern Ocean sea ice since late 1978 has revealed overall increases rather than decreases in ice extents, with ice extent trends on the order of 11,000 sq km/year. When broken down spatially, the positive trends are strongest in the Ross Sea, while the trends are negative in the Bellingshausen/Amundsen Seas. Greater spatial detail can be obtained by examining trends in the length of the sea ice season, and those trends show a coherent picture of shortening sea ice seasons throughout almost the entire Bellingshausen and Amundsen Seas to the west of the Antarctic Peninsula and in the far western Weddell Sea immediately to the east of the Peninsula, with lengthening sea ice seasons around much of the rest of the continent. This pattern corresponds well with the spatial pattern of temperature trends, as the Peninsula region is the one region in the Antarctic with a strong record of temperature increases. Still, although the patterns of the temperature and ice changes match fairly well, there is a substantial ways to go before these patterns are understood (and can be modeled) in the full context of global change.

Parkinson, Claire L.↗
NASA NTRS1980

Theoretical results on the tandem junction solar cell based on its Ebers-Moll transistor model

A one-dimensional theoretical model of the tandem junction solar cell (TJC) with base resistivity greater than about 1 ohm-cm and under low level injection has been derived. This model extends a previously published conceptual model which treats the TJC as an npn transistor. The model gives theoretical expressions for each of the Ebers-Moll type currents of the illuminated TJC and allows for the calculation of the spectral response, I(sc), V(oc), FF and eta under variation of one or more of the geometrical and material parameters and 1MeV electron fluence. Results of computer calculations based on this model are presented and discussed. These results indicate that for space applications, both a high beginning of life efficiency, greater than 15% AM0, and a high radiation tolerance can be achieved only with thin (less than 50 microns) TJC's with high base resistivity (greater than 10 ohm-cm).

Goradia, C.↗
NASA NTRS1989

Lithospheric buckling and intra-arc stresses: A mechanism for arc segmentation

Comparison of segment development of a number of arcs has shown that consistent relationships between segmentation, volcanism and variable stresses exists. Researchers successfully modeled these relationships using the conceptual model of lithospheric buckling of Yamaoka et al. (1986; 1987). Lithosphere buckling (deformation) provides the needed mechanism to explain segmentation phenomenon; offsets in volcanic fronts, distribution of calderas within segments, variable segment stresses and the chemical diversity seen between segment boundary and segment interior magmas.

Nelson, Kerri L.↗
NASA NTRS1983

A model for the distributed storage and processing of large arrays

A conceptual model for parallel computations on large arrays is developed. The model provides a set of language concepts appropriate for processing arrays which are generally too large to fit in the primary memories of a multiprocessor system. The semantic model is used to represent arrays on a concurrent architecture in such a way that the performance realities inherent in the distributed storage and processing can be adequately represented. An implementation of the large array concept as an Ada package is also described.

Mehrota, P.↗
NASA NTRS1985

Stress analysis of the space telescope focal plane structure joint

Two major efforts were begun concerning the Space Telescope focal plane structure joint. The 3-D solid finite element modeling of the bipod flexure plate was carried out. Conceptual models were developed for the load transfer through the three major bolts to the flexure plate. The flexure plate drawings were reconstructed using DADAM for the purpose of developing a file from which the coordinates of any point on the flexure plate could be determined and also to locate the attachment points of the various components which connect with the flexure plate. For modeling convenience the CADAM drawing of the flexure plate has been divided into several regions which will be subdivided into finite elements using MSGMESH, which is a finite element mesh generator available with MSC/NASTRAN. In addition to the CADAM work on the flexure plate, an effort was also begun to develop computer aided drawings of the peripheral beam which will be used to assist in modeling the connection between it and the flexure plate.

Foster, W. A., Jr.↗
NASA NTRS1987

Software reliability models for fault-tolerant avionics computers and related topics

Software reliability research is briefly described. General research topics are reliability growth models, quality of software reliability prediction, the complete monotonicity property of reliability growth, conceptual modelling of software failure behavior, assurance of ultrahigh reliability, and analysis techniques for fault-tolerant systems.

Miller, Douglas R.↗
NASA NTRSDate not supplied

Assessment of the Impact of an Advanced Power System on a Turboelectric Single-Aisle Concept Aircraft

Electrified aircraft propulsion concepts show potential in using propulsion airframe inte-gration in order to increase efficiency in flight and therefore decrease fuel burn and emissions.Electrification offers component efficiency values greater than 90 percent, but the loss is in the form of low grade waste heat. A major challenge of electrified aircraft propulsion is managing that heat while minimizing any penalties associated with a thermal management system. This paper explores the effect of two innovations in the management of waste heat at the aircraft system level for a turboelectric single aisle concept. The first innovation is achieving a 3 times reduction in heat by developing high-efficiency components rather than managing the high levels of heat. The second takes advantage of the outer mold line of the aircraft to reject heat directly to the environment passively instead of adding active cooling loops that negatively impact the weight, power, and drag of the aircraft. In order to fully grasp the impact of the advanced power system, we develop methods of modeling the power and thermal management systems to be integrated in the full aircraft conceptual model. We then model the aircraft with a state of the art DC transmission system and active cooling loops as a baseline for our study. Our second model includes the advanced power system with active cooling, which results in a fuel burn reduction of 2.5 percent. Finally, in our third model we assess the benefit of an outer mold line cooling scheme with the advanced power system. The outer mold line cooling scheme with an advanced power system yields an additional 0.8 percent reduction in fuel burn,for an overall fuel burn reduction potential of 3.3 percent in addition to aerodynamic benefits of electrified aircraft propulsion.

Electric Aircraft↗
NASA NTRS1988

Use of LANDSAT images of vegetation cover to estimate effective hydraulic properties of soils

The estimation of the spatially variable surface moisture and heat fluxes of natural, semivegetated landscapes is difficult due to the highly random nature of the vegetation (e.g., plant species, density, and stress) and the soil (e.g., moisture content, and soil hydraulic conductivity). The solution to that problem lies, in part, in the use of satellite remotely sensed data, and in the preparation of those data in terms of the physical properties of the plant and soil. The work was focused on the development and testing of a stochastic geometric canopy-soil reflectance model, which can be applied to the physically-based interpretation of LANDSAT images. The model conceptualizes the landscape as a stochastic surface with bulk plant and soil reflective properties. The model is particularly suited for regional scale investigations where the quantification of the bulk landscape properties, such as fractional vegetation cover, is important on a pixel by pixel basis. A summary of the theoretical analysis and the preliminary testing of the model with actual aerial radiometric data is provided.

Eagleson, Peter S.↗