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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Simmer-enhanced flashlamp-pumped dye laser

It has been demonstrated experimentally that by enhancing the simmer current in the flash lamps before the energy discharge, the lamp inductance is reduced and the dye laser efficiency is thus remarkably improved. This technique has advantages over the prepulsing technique for conditioning flash lamps; the electronic circuit for the simmer enhancement is simple, inexpensive and reliable, and accurate timing is not required. Furthermore, the simmer enhancement consumes much less power, thus minimizing the attendant thermal effects and improving overall laser efficiency.

Yee, T. K.↗
NASA NTRS2021

Revolutionary Vertical Lift Technology Project: Variable-Speed Power Turbine Technology Demonstration

Demonstrate 50% improvement in efficient operational capability using a Variable-Speed Power Turbine concept. To enable this improvement, thermodynamics mechanical challenges from operating across variable shaft speeds must be accommodated. Also, aerodynamics research for the engine high-efficiency turbine component design must be conducted over a wide range of incidence angle variation.

Susan A Gorton↗
NASA NTRSDate not supplied

From the Knowledge-based Digital Platform (KbDP) Concept for Advanced Air Mobility Research to a Preliminary Prototype

Advanced Air Mobility (AAM) encompasses a range of innovative operational and technological changes to aviation (electric aircraft, increasingly automated aircraft, increasingly automated airspace operations, etc.) that are transforming aviation’s role in everyday movement of people and goods. There are multiple associated concepts and use cases for AAM, all interrelated, including small Unmanned Aircraft System (UAS) Traffic Management (UTM), Upper-Class E Traffic Management (ETM), Extensible Traffic Management (xTM), Regional Air Mobility (RAM), and Urban Air Mobility (UAM). These AAM operations must integrate with traditional Air Traffic Management (ATM) operations, as well as non-aviation modes of transportation and logistics. National Aeronautics and Space Administration (NASA) is spearheading an innovative digital engineering approach to integrate, communicate, and facilitate the research of multi-modal transportation systems. The Knowledge-based Digital Platform (KbDP) is a concept being developed that ties the workflows of Project Managers (PM), Principal Investigators (PI), and System Engineers together across organizational boundaries. It does so through the management of an information database defined by mathematical, data science, and system engineering principles. Machine Learning (ML) algorithms play a key role in this concept by extracting meaningful knowledge from the information database, which the human user leverages to greatly improve the efficiency and effectiveness of their research. Expected benefits of this concept include improved technology transfers from research to production, improved research portfolio investments, and research outcomes that are more integrated with all aspects of the multi-modal transportation problem. The preliminary KbDP prototype has been realized using UAM as a pathfinder use case and developed by a team of system engineer, software developer, data scientist, and interns.

Systems Engineering↗
NASA NTRS1980

Evaluation and optimization of silicon sheet solar cells

This paper describes the results and procedures to evaluate and improve the efficiency of solar cells made from various unconventional silicon sheets. The performance parameters included photovoltaic characteristics, spectral response, dark I-V characteristics, and diffusion length. The evaluation techniques used provided accurate and reliable information on sheet performance, and self-consistent results were obtained from the various measurement techniques used. Minority carrier diffusion length (L) was shown to be the ultimate limiting factor for the sheet cell performance (efficiency) and other back-up measurements confirmed this L-dependence. Limited efforts were made to identify defects which influence cell performance, and to use some improved process methods to increase cell efficiency.

Yoo, H.↗
NASA NTRS2006

Testing of an Amine-Based Pressure-Swing System for Carbon Dioxide and Humidity Control

Hamilton Sundstrand has developed a stable and efficient amine-based carbon dioxide (CO2) and water vapor (H2O) sorbent, SA9T, that is well-suited for use in a spacecraft environment. The sorbent is efficiently packaged in pressure-swing regenerable beds that are thermally linked to improve removal efficiency and minimize vehicle thermal loads, and the flows are all controlled with a single spool valve. The SA9T sorbent technology has already been baselined for the new Orion spacecraft. However, more data was needed on the operational characteristics of the package in a simulated spacecraft environment. This amine-based technology, referred to as the CO2 And Moisture Removal Amine Swing-bed (CAMRAS) by the Exploration Life Support Air Team at Johnson Space Center (JSC), was tested at JSC during the last third of 2006. Two series of tests on the CAMRAS were performed at simulated metabolic loads of four and/or six crewmen in a closed chamber. Tests were run at a variety of cabin temperatures and with a range of operating conditions varying cycle time, available vacuum pressure, blower speed, and crew activity levels. Results of this testing are presented and potential flight operational strategies discussed.

Lin, Amy B.↗
NASA NTRS2007

Testing of an Amine-Based Pressure-Swing System for Carbon Dioxide and Humidity Control

In a crewed spacecraft environment, atmospheric carbon dioxide (CO2) and moisture control is crucial. Hamilton Sundstrand has developed a stable and efficient amine-based CO2 and water vapor sorbent, SA9T, that is well-suited for use in a spacecraft environment. The sorbent is efficiently packaged in pressure-swing regenerable beds that are thermally linked to improve removal efficiency and minimize vehicle thermal loads. Flows are all controlled with a single spool valve. This technology has been baselined for the new Orion spacecraft. However, more data was needed on the operational characteristics of the package in a simulated spacecraft environment. A unit was therefore tested with simulated metabolic loads in a closed chamber at Johnson Space Center during the last third of 2006. Tests were run at a variety of cabin temperatures and with a range of operating conditions varying cycle time, vacuum pressure, air flow rate, and crew activity levels. Results of this testing are presented and potential flight operational strategies discussed.

Lin, Amy↗
NASA NTRS2008

Further Testing of an Amine-based Pressure-Swing System for Carbon Dioxide and Humidity Control

In a crewed spacecraft environment, atmospheric carbon dioxide (CO2) and moisture control are crucial. Hamilton Sundstrand has developed a stable and efficient amine-based CO2 and water vapor sorbent, SA9T, that is well suited for use in a spacecraft environment. The sorbent is efficiently packaged in pressure-swing regenerable beds that are thermally linked to improve removal efficiency and minimize vehicle thermal loads. Flows are all controlled with a single spool valve. This technology has been baselined for the new Orion spacecraft. However, more data was needed on the operational characteristics of the package in a simulated spacecraft environment. A unit was therefore tested with simulated metabolic loads in a closed chamber at Johnson Space Center during the last third of 2006. Those test results were reported in a 2007 ICES paper. A second test article was incorporated for a third phase of testing, and that test article was modified to allow pressurized gas purge regeneration on the launch pad in addition to the standard vacuum regeneration in space. Metabolic rates and chamber volumes were also adjusted to reflect current programmatic standards. The third phase of tests was performed during the spring and summer of 2007. Tests were run with a range of operating conditions, varying: cycle time, vacuum pressure (or purge gas flow rate), air flow rate, and crew activity levels. Results of this testing are presented and potential flight operational strategies discussed.

Lin, Amy↗
NASA NTRS1993

Two-dimensional radiative transfer in cloudy atmospheres - The spherical harmonic spatial grid method

A new two-dimensional monochromatic method that computes the transfer of solar or thermal radiation through atmospheres with arbitrary optical properties is described. The model discretizes the radiative transfer equation by expanding the angular part of the radiance field in a spherical harmonic series and representing the spatial part with a discrete grid. The resulting sparse coupled system of equations is solved iteratively with the conjugate gradient method. A Monte Carlo model is used for extensive verification of outgoing flux and radiance values from both smooth and highly variable (multifractal) media. The spherical harmonic expansion naturally allows for different levels of approximation, but tests show that the 2D equivalent of the two-stream approximation is poor at approximating variations in the outgoing flux. The model developed here is shown to be highly efficient so that media with tens of thousands of grid points can be computed in minutes. The large improvement in efficiency will permit quick, accurate radiative transfer calculations of realistic cloud fields and improve our understanding of the effect of inhomogeneity on radiative transfer in cloudy atmospheres.

Evans, K. F.↗
NASA NTRS1979

Performance of two-stage fan with a first-stage rotor redesigned to account for the presence of a part-span damper

The NASA two-stage fan was tested with a redesigned first-stage rotor. The redesign included a new design approach to account for the presence of a part-span damper. At design speed the fan achieved a peak efficiency of 0.803, which is 1.9 percentage points higher than the original design. The peak efficiencies of the first stage and first rotor were 0.789 and 0.821, respectively. An improvement in efficiency of up to 5 percentage points in the damper region was achieved over the original large damper version. The stall margin, based on flow conditions at peak efficiency, was 10 percent at design speed.

Gorrell, W. T.↗
NASA NTRS1988

Reasoning with case histories of process knowledge for efficient process development

The significance of compiling case histories of empirical process knowledge and the role of such histories in improving the efficiency of manufacturing process development is discussed in this paper. Methods of representing important investigations as cases and using the information from such cases to eliminate redundancy of empirical investigations in analogous process development situations are also discussed. A system is proposed that uses such methods to capture the problem-solving framework of the application domain. A conceptual design of the system is presented and discussed.

Bharwani, Seraj S.↗
NASA NTRS1988

Hybrid solar cells based on dc magnetron sputtered films of n-ITO on APMOVPE grown p-InP

Hybrid indium-tin-oxide (ITO)/InP solar cells are discussed. The cells are constructed by dc magnetron sputter deposition of ITO onto high-quality InP films grown by atmospheric pressure metal-organic vapor-phase epitaxy (APMOVPE). A record efficiency of 18.9 percent, measured under standard Solar Energy Research Institute reporting conditions, has been obtained. The p-InP surface is shown to be type converted, principally by the ITO, but with the extent of conversion being modified by the nature of the sputtering gas. The deposition process, in itself, is not responsible for the type conversion. Dark currents have been suppressed by more than three orders of magnitude by the addition of hydrogen to the sputtering gas during deposition of a thin (5 nm) interface layer. Without this layer, and using only the more usual argon/oxygen mixture, the devices had poorer efficiencies and were unstable. A discussion of associated quantum efficiencies and capacitance/voltage measurements is also presented from which it is concluded that further improvements in efficiency will result from better control over the type-conversion process.

Coutts, T. J.↗
NASA NTRS1990

A computationally efficient model for turbulent droplet dispersion in spray combustion

A novel model for turbulent droplet dispersion is formulated having significantly improved computational efficiency in comparison to the conventional point source stochastic sampling methodology. In the proposed model, a computational parcel representing a group of physical particles is considered to have a normal (Gaussian) probability density function (PDF) in three-dimensional space. The mean of each PDF is determined by Lagrangian tracking of each computational parcel, either deterministically or stochastically. The variance is represented by a turbulence-induced mean squared dispersion which is based on statistical inferences from the linearized direct modeling formulation for particle/eddy interactions. Convolution of the computational parcel PDF's produces a single PDF for the physical particle distribution profile. The validity of the new model is established by comparison with the conventional stochastic sampling method, where in each parcel is represented by a delta function distribution, for non-evaporating particles injected into simple turbulent air flows.

Litchford, Ron J.↗
NASA NTRS1992

Study of shock-induced combustion using an implicit TVD scheme

The supersonic combustion flowfields associated with various hypersonic propulsion systems, such as the ram accelerator, the oblique detonation wave engine, and the scramjet, are being investigated using a new computational fluid dynamics (CFD) code. The code solves the fully coupled Reynolds-averaged Navier-Stokes equations and species continuity equations in an efficient manner. It employs an iterative method and a second order differencing scheme to improve computational efficiency. The code is currently being applied to study shock wave/boundary layer interactions in premixed combustible gases, and to investigate the ram accelerator concept. Results obtained for a ram accelerator configuration indicate a new combustion mechanism in which a shock wave induces combustion in the boundary layer, which then propagates outward and downstream. The combustion process creates a high pressure region over the back of the projectile resulting in a net positive thrust forward.

Yungster, Shayne↗
NASA NTRS1982

Efficiency of silicon solar cells containing chromium

Efficiency of silicon solar cells containing about one quadrillon atoms cu cm of chromium is improved about 26% by thermal annealing of the silicon wafer at a temperature of 200 C to form chromium precipitates having a diameter of less than 1 Angstrom. Further improvement in efficiency is achieved by scribing laser lines onto the back surface of the wafer at a spacing of at least 0.5 mm and at a depth of less than 13 micrometers to preferentially precipitate chromium near the back surface and away from the junction region of the device. This provides an economical way to improve the deleterious effects of chromium, one of the impurities present in metallurgical grade silicon mateial.

Salama, A. M.↗
NASA NTRSDate not supplied

TPSAS-NF1676L-14659-DND

Subsonic fixed wing aircraft dominant the world's air fleet and move people and goods on 24/7 basis. While air travel is an effective, efficient means of transportation providing an unmatched combination of speed and range, future subsonic aircraft must continue to improve substantially to meet energy efficiency and environmental compatibility goals. The NASA Fundamental Aeronautics Program via the Subsonic Fixed Wing (SFW) Project addresses the comprehensive challenge of enabling revolutionary energy-efficiency improvements in subsonic transport aircraft combined with dramatic reductions in harmful emissions and perceived noise to facilitate sustained growth of the air transportation system. Advanced technologies and the development of unconventional aircraft systems offer the potential to achieve these improvements. Multidisciplinary advances are required in aerodynamic efficiency to reduce drag, structural efficiency to reduce aircraft empty weight, and propulsive and thermal efficiency to reduce thrust-specific energy consumption (TSEC) for overall system benefit. Additionally, advances are required to reduce perceived noise without adversely affecting drag, weight, or TSEC and to reduce harmful emissions without adversely affecting energy efficiency or noise. The primary focus of SFW is on the "N+3" generation; that is, vehicles that are three generations beyond the current state of the art, requiring mature technology solutions in the 2025-30 timeframe. Success in overcoming these technical challenges will result in major changes to engine cycle and airframe configurations, which in turn will broaden the technology trade space for vehicles ranging from large transports to very light jets. This presentation provides an overview of SFW-sponsored research targeted at improved aerodynamic and structural efficiency for airframe and integrated vehicle systems.

Richard A Wahls↗
NASA NTRS1983

Numerical computation of transonic flow about wing-fuselage configurations on a vector computer

The transonic wing analysis code TWING, which uses the AF2 relaxation algorithm, has been vectorized to run on the Cray-1S computer. Vectorization of this code improved computational efficiency over that of the CDC 7600 computer by factors of 11 to 13. The improvement compares favorably with the prediction of a theoretical performance model. A convenient generalization now permits the treatment of rudimentary wing-fuselage combinations. Flow predictions for a transport configuration in both isolated-wing and wing-fuselage modes show the expected trends in shock strength and position when compared with wind-tunnel results. An isolated fighter wing is examined in terms of execution time on three different computers and in comparison with experimental data. The computational fluid dynamics code produced during this study is a careful union of an efficient three-dimensional, transonic, numerical algorithm and the vector features presently available on modern computers.

Thomas, S. D.↗
NASA NTRSDate not supplied

Integration of Advanced Structures and Materials Technologies for a Robust Lunar Habitat

NASA’s Artemis program plans to have a sustainable lunar base deployed on the Moon by 2028. The base calls for a foundation surface habitat that can support a crew of four members for a minimum mission duration of 28-days. The lack of a magnetic field and significant lunar atmosphere extends the lifetime of secondary radiation emitted from metallic structures, which is a health hazard for exposed astronauts. Integration of non-metallic structural materials into surface habitat design may alleviate some of these concerns. Additionally, it is favorable for the structure to be collapsible for transportation to optimize payload volume, mass efficiency, and monetary constraints. As a result, inflatable structures are being investigated due to their improved packing efficiency at launch, optimal mass-to-volume ratio, and large surface area that can efficiently disperse structural loads and heat. Currently, only two inflatable airlocks have been deployed in space. Thus, there is a significant need to advance technologies associated with inflatable structures to provide greater options for future missions, i.e., Artemis and beyond. This study focused on the inflatable lunar habitat applications of emerging NASA Langley Research Center (LaRC) technologies and their required development steps to become space qualified. The Bowling Habitat architecture was generated from 13 of these NASA LaRC technologies, five of which were deemed critical, five determined as enhancing technologies, and three were classified as transformational technologies for the Artemis program. To address the payload constraints, the study also considered a tentative timeline that aligned with the current Artemis schedule for transporting the Bowling Habitat to the Moon. Ultimately, the Bowling Habitat mainly addressed the structural needs of an inflatable lunar habitat, meaning that major areas pertaining to the life-style aspects of the habitat must be improved. Areas include, but are not limited to, hard connection points, the monitoring of human health, and extra radiation protection for solar proton events.

Inflatable Habitat↗