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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Bit Error Rate Performance on Passive Alignment in Free Space Optical Links Using Large Core Fibers

A 20-meter free-space optical link (FSOL) is proposed for data transmission between external ISS payload sites and the main cabin at a target rate of 10 Gbps (gigabits per second). Motion between a payload site and the main cabin is predicted to cause up to 5 cm in lateral misalignment and 0.2 degrees of angular misalignment. Due to the harsh environment of space it is advantageous to locate the optical transceivers inside the spacecraft or in a controlled environment. With the optical components and transceivers in separate locations, a fiber optic cable will be required to carry light between the two. In our past work we found that the use of large-core fibers provide an increased misalignment tolerance for such systems and could eliminate the need for active control of the optics. In that work, it was shown that a 105 m core diameter fiber optic cable offered a viable low SWaP (size, weight, and power) solution for the ISS application; however, the effects of modal dispersion were not investigated. This paper will present bit error rate performance of the FSOL using these large-core fibers.

Optical Bit Error Rate Testing↗
NASA NTRS2019

Using Machine Learning to Predict Core Sizes of High-Efficiency Turbofan Engines

With the rise in big data and analytics, machine learning is transforming many industries. It is being increasingly employed to solve a wide range of complex problems, producing autonomous systems that support human decision-making. For the aircraft engine industry, machine learning of historical and existing engine data could provide insights that help drive for better engine design. This work explored the application of machine learning to engine preliminary design. Engine core-size prediction was chosen for the first study because of its relative simplicity in terms of number of input variables required (only three). Specifically, machine-learning predictive tools were developed for turbofan engine core-size prediction, using publicly available data of two hundred manufactured engines and engines that were studied previously in NASA aeronautics projects. The prediction results of these models show that, by bringing together big data, robust machine-learning algorithms and data science, a machine learning-based predictive model can be an effective tool for turbofan engine core-size prediction. The promising results of this first study paves the way for further exploration of the use of machine learning for aircraft engine preliminary design.

Core Size↗
NASA NTRSDate not supplied

Initial Petrographic Analysis of Apollo 17 73002 Continuous Core Thin Sections Using QEMSCAN Mapping Techniques

In 1972, the Apollo 17 mission landed in the Taurus-Littrow Valley located in the southeastern edge of Mare Serenitatis [1].During EVA 2at Station 3,a double drive tube was used to collect a sealed core sample (73001/2)of the upper~70cm of the lunar regolith[2-4].The core was taken from the surface of the light mantle deposit, found at the base of the South Massif [3]. For nearly 50 years, the sealed core samples have remained unopened. This study is part of the Apollo Next Generation Sample Analysis (ANGSA) initiative to analyze the continuous thin sections from the Apollo 17 drive tubes opened in 2019[5-7].

QEMSCAN↗
NASA NTRS2024

Hybrid Thermally Efficient Core (HyTEC) HyTEC Phase 1 – Advanced Aerodynamics Final Report

The objective of the Hybrid Thermally Efficient Core (HyTEC) – Advanced High Pressure Turbine (HPT) Aerodynamics project is to develop technology for a compact core that contributes to significant fuel burn reductions of 5-10% over current generation technologies. To accomplish this, the HPT is incorporating a range of aerodynamic features and technologies to improve component efficiency and provide favorable systems level trades. In particular, this project explored low solidity airfoils, advanced tip treatments, platform contouring, and advanced ceramic matrix composite (CMC) Stage 2 Nozzle (S2N) airfoils to eliminate the need for post throat cooling in a compact core environment. The maturation of these technology areas is expected to provide a significant improvement in component efficiencies, and consequently reductions in fuel burn, over the current state of the art (SoA). To mature these technologies to Technology Readiness Level (TRL) 4, a test campaign was performed that consisted of four tests at three facilities. TRL 3 testing was performed in the CW22 linear cascade at NASA Glenn for blade and nozzle technologies, TRL 4 nozzle testing was performed at GE Aerospace (GEA) Test Cell A8, and TRL 4 blade testing was performed at the Notre Dame Turbomachinery Laboratory (NDTL) using the Transonic Research Turbine (TRT) rig. Low solidity was successfully demonstrated to a TRL 4 level. Low solidity nozzles showed benefits in line with pre-project expectations, while low solidity blades were shown to have an aerodynamic penalty. Crucially, this program only considered the aerodynamic losses, and systems trades such as reductions in cooling flows are expected to continue to make low solidity blades a net positive. By successfully quantifying the aerodynamic performance in this project, these trades can be conducted to determine where in the engine architecture low solidity blades will contribute positively to system operation. Platform contouring was demonstrated to a TRL 4 level, with performance in line with the lower end of the pre-project expected range. Advanced tip treatments performance levels were indeterminate, showing the expected improvements to flow physics but with a performance level confounded by several rig issues including whirl mode induced variation in tip clearance. The elimination of post-throat cooling on the S2N was successfully demonstrated to provide a performance benefit, however that benefit was approximately half the level that was expected in pre-project predictions. Overall, the technology maturation plan for HyTEC Phase 1 was successful, bringing the suite of technologies to TRL 4.

High pressure turbine↗
NASA NTRS1962

Thermal and Criticality Analysis of the Plasma Core Reactor

Radiative heat transfer to the propellant and reactor criticality for a fissionable gaseous rocket engine are analyzed to determine their interdependence. The necessity for propellant thicknesses of approximately 1-3 m due to poor thermal absorption properties of hydrogen significantly affects reactor critical radius and mass. The two primary adverse effects are: (1) increased absorption in the reflector- moderator for a given reflector thickness and (2) poor utilization of thermal neutrons by the core due to the lower geometrical view factor of the core for the reflector walls. In fact, there is a minimum core radius at a particular propellant thickness which allows the system to “go” critical. Engine performance is limited primarily to two regions of operation: the first, a specific impulse of approximately 1550 sec at a thrust level of 2 x 10(exp 6) lb. and second, a specific impulse of approximately 2200 sec at a thrust level of 5.3 x 10(exp 6) lb.

Rocket engine↗
NASA NTRS1965

Reinforcement core facilitates O-ring installation

Reinforcement core holds O-ring in place within a structure while adjacent parts are being assembled. The core in the O-ring adds circumferential rigidity to the O-ring material. This inner core does not appreciably affect the sectional elasticity or gland-sealing characteristics of the O-ring.

Source record↗
NASA NTRS1971

Saturation current spikes eliminated in saturable core transformers

Unsaturating composite magnetic core transformer, consisting of two separate parallel cores designed so impending core saturation causes signal generation, terminates high current spike in converter primary circuit. Simplified waveform, demonstrates transformer effectiveness in eliminating current spikes.

Schwarz, F. C.↗
NASA NTRS1972

Drive turbine system for 20-inch turbofan simulators. 2: Core turbine design

Drive-turbines for a given set of 20-inch turbo-fan simulators are described. The simulators had both single-stage and two-stage fans that had design pressure ratios as low as 1.25 and as high as 3.0. The desired objective of the study was to be able to drive all of the single-stage fans with one core turbine and to drive all of the two-stage fans with this same core turbine in combination with a duct turbine. The core turbine is described. Included are the design operating conditions, design velocity diagram and a power-speed envelope determined by an off-design performance procedure. Also discussed is the adaption and scaling of an existing turbine design to this particular application.

Whitney, W. J.↗
NASA NTRS1972

Mobilities of polyatomic ions in gases - Core model.

A core model, consisting of a (12-4) central potential displaced from the origin, is suggested as a representation of the interaction of polyatomic ions with neutral molecules. The diffusion collision integral, which describes ion mobility, is computed and tabulated as a function of temperature and core size. The addition of the core reduces the maximum in the mobility against temperature curve, and eventually reduces the mobility below its polarization limit at all temperatures. These results are in accord with limited available experimental data. Comparison is made with other models of ion-neutral interactions.

Mason, E. A.↗
NASA NTRS1973

Radial honeycomb core

Core alleviates many limitations of conventional nacelle construction methods. Radical core, made of metals or nonmetals, is fabricated either by joining nodes and then expanding, or by performing each layer and then joining nodes. Core may also be produced from ribbons or strips with joined nodes or ribbons oriented in longitudinal planes.

Cantley, R. B.↗
NASA NTRS1973

Flat-band assembly for toroidal transformer cores

Toroidal transformer cores are often banded together by means of strap. Spot welds secure strap. Proper tension is obtained by use of special fixture in conjunction with winding of wire which is placed temporarily on core; winding is excited by dc current to hold core halves together magnetically during alignment.

Mclyman, W. T.↗
NASA NTRS1973

Feasibility study of full-reactor gas core demonstration test

Separate studies of nuclear criticality, flow patterns, and thermodynamics for the gas core reactor concept have all given positive indications of its feasibility. However, before serious design for a full scale gas core application can be made, feasibility must be shown for operation with full interaction of the nuclear, thermal, and hydraulic effects. A minimum sized, and hence minimum expense, test arrangement is considered for a full gas core configuration. It is shown that the hydrogen coolant scattering effects dominate the nuclear considerations at elevated temperatures. A cavity diameter of somewhat larger than 4 ft (122 cm) will be needed if temperatures high enough to vaporize uranium are to be achieved.

Kunze, J. F.↗
NASA NTRS1973

The core paradox.

Rebuttal of suggestions from various critics attempting to provide an escape from the seeming paradox originated by Higgins and Kennedy's (1971) proposed possibility that the liquid in the outer core was thermally stably stratified and that this stratification might prove a powerful inhibitor to circulation of the outer core fluid of the kind postulated for the generation of the earth's magnetic field. These suggestions are examined and shown to provide no reasonable escape from the core paradox.

Kennedy, G. C.↗
NASA NTRS1973

The end of the iron-core age.

The terrestrial planets aggregated essentially from small particles, to begin as solid cool bodies with the same general compositions, and there is no possibility of an iron-core developing within any of them at any stage. Their differing internal and surface properties receive ready explanation from their different masses which determine whether the pressures within are sufficient to bring about phase-changes. The claim that the terrestrial core can be identified by means of shock-wave data as nickel-iron is based on theoretical misconception, whereas the actual seismic data establish an uncompressed-density value much lower than any such mixture could have. The onset of the Ramsey phase-change in the earth takes the form of a rapid initial collapse to produce a large core in metallic state which thereafter continues to grow secularly as a result of radioactive heating and leads to reduction of surface-area at long last adequate to account for folded and thrusted mountain-building.

Lyttleton, R. A.↗
NASA NTRS1973

Carbon chemistry of the Apollo 15 and 16 deep drill cores

The carbon chemistry of the Apollo 15 and 16 deep drill cores is a function of the surface exposure plus the chemical and mineralogical composition of the individual samples. The depth profiles of carbide and methane yields in the Apollo 15 core show a general decline with depth and correlate with the solar wind noble gas content, percentage agglutinates, track densities, and metallic iron. All horizons examined were exposed for a considerable time on the lunar surface. The Apollo 16 core samples show that chemical and mineralogical composition plays an important role in determining the nature of carbide-like material present in the fines. The higher aluminum and calcium contents and lower iron contents of highlands material result in carbide-like material yielding less CD4 and more C2D2 (deuteroacetylene) upon DF acid dissolution.

Wszolek, P. C.↗
NASA NTRS1974

Apollo 16: Core 60004 - Preliminary study of less than 1 mm fines

The article studies the possible variation of mineralogy as a function of both grain size and depth within the core of less than 1 mm fines, for the core section 60004 from Apollo 16. Twelve samples of the fines were dry sieved. The grain size analysis showed a bimodal distribution for all samples, indicating a competing process of grain size degeneration and agglutinate formation. Approximately 99% of the minerals in the samples examined consisted of plagioclase feldspar, pyroxene and olivine, with plagioclase the dominant phase. The various minerals were analyzed, using standard electron microprobe techniques, as a function of size range for each sample, and the representative analyses are presented. Several types of glass were also analyzed, ranging in color from orange through yellow and green to colorless. The investigation of the chemical variations of mineral and lithic clasts from the top and the bottom of the core suggests that although minor variations are present, the regolith was derived from fairly homogeneous sources.

Meyer, H. O. A.↗
NASA NTRS1974

Stabilization of lunar core samples

Processing of lunar cores includes: (1) careful dissection for study of loose fines, and (2) stabilization of the residue by peeling and impregnation. The newly developed technique for preparing thin peels of lunar cores requires application of the methacrylate adhesive to a backing strip, before taking the peel. To ensure complete impregnation of the very fine, dry lunar soil, the low-viscosity epoxy, Araldite 506, is gently flowed onto the core, under vacuum.

Nagle, J. S.↗
NASA NTRS1977

Toroidal converter core

Improved approach consists of cut and uncut cores nested in concentric configuration. Cores are made by winding steel ribbon on mandrel and impregnating with epoxy to bond layers together. Gap is made by cutting across wound and bonded core. Rough ends are ground or lapped.

Mclyman, W. T.↗