Search NASA⌕ Search

SEARCH · Search NASA

Results for “Small Core”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Core noise measurements from a small, general aviation turbofan engine

As part of a program to investigate combustor and other core noises, simultaneous measurements of internal fluctuating pressure and far field noise were made with a JT15D turbofan engine. Acoustic waveguide probes, located in the engine at the combustor, at the turbine exit and in the core nozzle wall, were used to measure internal fluctuating pressures. Low frequency acoustic power determined at the core nozzle exit corresponds in level to the far field acoustic power at engine speeds below 65% of maximum, the approach condition. At engine speeds above 65% of maximum, the jet noise dominates in the far field, greatly exceeding that of the core. From coherence measurements, it is shown that the combustor is the dominant source of the low frequency core noise. The results obtained from the JT15D engine were compared with those obtained previously from a YF102 engine, both engines having reverse flow annular combustors and being in the same size class.

Reshotko, M.↗
NASA NTRS1980

Core noise measurements from a small, general aviation turbofan engine

As part of a program to investigate combustor and other core noises, simultaneous measurements of internal fluctuating pressure and far field noise were made with a JT15D turbofan engine. Acoustic waveguide probes, located in the engine at the combustor, at the turbine exit and in the core nozzle wall, were used to measure internal fluctuating pressures. Low frequency acoustic power determined at the core nozzle exit corresponds in level to the far-field acoustic power at engine speeds below 65% of maximum, the approach condition. At engine speeds above 65% of maximum, the jet noise dominates in the far-field, greatly exceeding that of the core. From coherence measurements, it is shown that the combustor is the dominant source of the low frequency core noise. The results obtained from the JT15D engine were compared with those obtained previously from a YF102 engine, both engines having reverse flow annular combustors and being in the same size class.

Reshotko, M.↗
NASA NTRS1986

Airfoil gust response and the sound produced by airifoil-vortex interaction

This paper contributes to the understanding of the noise generation process of an airfoil encountering an unsteady upwash. By using a fast Fourier transform together with accurate airfoil response functions, the lift-time waveform for an airfoil encountering a delta function gust (the indicial function) is calculated for a flat plate airfoil in a compressible flow. This shows the interesting property that the lift is constant until the generated acoustic wave reaches the trailing edge. Expressions are given for the magnitude of this constant and for the pressure distribution on the airfoil during this time interval. The case of an airfoil cutting through a line vortex is also analyzed. The pressure-time waveform in the far field is closely related to the left-time waveform for the above problem of an airfoil entering a delta function gust. The effects of varying the relevant parameters in the problem are studied, including the observed position, the core diameter of the vortex, the vortex orientation and the airfoil span. The far field sound varies significantly with observer position, illustrating the importance of non-compactness effects. Increasing the viscous core diameter tends to smooth the pressure-time waveform. For small viscous core radius and infinite span, changing the vortex orientation changes only the amplitude of the pressure-time waveform, and not the shape.

Amiet, R. K.↗
NASA NTRS1994

On the effects of filtering on convective-core statistics

Analysis of convective events north of Australia during the equatorial Monsoon Experiment (EMEX) reinforces accumulating evidence that convective cores over the tropical ocean are weak, with small diameters and vertical velocities. Superposition of smaller-scale turbulence on the convective core signal could yield artificially small cores, and thus produce sampling bias by aircraft. To investigate this potential source of bias, a side-by-side analysis of filtered and unfiltered vertical velocity data was performed while investigating the EMEX convective cores. Data were collected by the NOAA P3 and NCAR Electra using filtered (Graham filter) and non-filtered cores. The effects of filtering vertical velocity data to identify updraft and downdraft cores were noticeable but smaller than expected. Updraft cores had a vertical velocity greater than 1 m/sec for at least 500 m, and downdraft cores were defined analogously so that the filter eliminated events with less than a 500 m apparent diameter. Median and 10 percent core diameters were increased by 20-25 percent at most, with larger increases at higher levels (fewer small events). The maximum vertical velocity was changed only by changing the individual events in the distribution, but changes were detectable. At the lower levels, where many small, weak cores are introduced by filtering, average vertical velocity for the updraft cores was lowered by up to around 10 percent. Mass flux was changed the least, since diameter and mean vertical velocity respond to filtering in opposite ways. The filtering procedure increased total mass flux slightly due to inclusion of more upward moving air into the sample.

Lemone, Margaret A.↗
NASA NTRS2013

Small Launch Vehicle Design Approaches: Clustered Cores Compared with Multi-Stage Inline Concepts

In an effort to better define small launch vehicle design options two approaches were investigated from the small launch vehicle trade space. The primary focus was to evaluate a clustered common core design against a purpose built inline vehicle. Both designs focused on liquid oxygen (LOX) and rocket propellant grade kerosene (RP-1) stages with the terminal stage later evaluated as a LOX/methane (CH4) stage. A series of performance optimization runs were done in order to minimize gross liftoff weight (GLOW) including alternative thrust levels, delivery altitude for payload, vehicle length to diameter ratio, alternative engine feed systems, re-evaluation of mass growth allowances, passive versus active guidance systems, and rail and tower launch methods. Additionally manufacturability, cost, and operations also play a large role in the benefits and detriments for each design. Presented here is the Advanced Concepts Office's Earth to Orbit Launch Team methodology and high level discussion of the performance trades and trends of both small launch vehicle solutions along with design philosophies that shaped both concepts. Without putting forth a decree stating one approach is better than the other; this discussion is meant to educate the community at large and let the reader determine which architecture is truly the most economical; since each path has such a unique set of limitations and potential payoffs.

Waters, Eric D.↗
NASA NTRS1993

Experimental segregation of iron-nickel metal, iron-sulfide, and olivine in a thermal gradient: Preliminary results

Speculation about the possible mechanisms for core formation in small asteroids raises more questions than answers. Petrologic evidence from iron meteorites, pallasites, and astronomical observations of M asteroids suggests that many small bodies were capable of core formation. Recent work by Taylor reviews the geochemical evidence and examines the possible physical/mechanical constraints on segregation processes. Taylor's evaluation suggests that extensive silicate partial melting (preferably 50 vol. percent or greater) is required before metal can segregate from the surrounding silicate and form a metal core. The arguments for large degrees of silicate partial melting are two-fold: (1) elemental trends in iron meteorites require that the metal was at is liquidus; and (2) experimental observations of metal/sulfide inclusions in partially molten silicate meteorites show that the metal/sulfide tends to form spherules in the liquid silicate due to surface tension effects. Taylor points out that for these metal spherules to sink through a silicate mush, high degrees of silicate partial melting are required to lower the silicate yield strength. Although some qualitative experimental data exists, little is actually known about the behavior of metals and liquid sulfides dispersed in silicate systems. In addition, we have been impressed with the ability of cumulative olivine to expel trapped liquid when placed in a thermal gradient. Consequently, we undertook to accomplish the following: (1) experimentally evaluate the potential for metal/sulfide/silicate segregation in a thermal gradient; and (2) obtain quantitative data of the wetting parameters of metal-sulfide melts among silicate grains.

Jurewicz, Stephen R.↗
NASA NTRS2004

When Push Comes to Shove: Gap-opening, Disk Clearing and the In Situ Formation of Giant Planets

Here we investigate a scenario in which cores as small as a few Earth masses stall in the terrestrial planet region, but continue to grow as a result of the Type I migration of other Earth sized objects, taking place in a timescale approx. 10(exp 6) years similar to the disk clearing timescale (such migration may thus significantly reduce the accretion efficiency, particularly in the terrestrial planet region). Since the core may intercept such inwardly migrating objects (possibly by altering the surface density to the point that the object stalls within the core's feeding zone) or coalesce with neighboring cores, its growth may continue until it reaches a CCM. The question then arises whether such a core can accrete enough gas to become a Jovian-sized giant planet. In the limit of low opacity (such that the protoplanet s tidal torque fails to clear gas from its feeding zone in time to prevent its accretion), the final mass of the planet is given by the gaseous isolation mass (provided alpha is < or approx. = 10(exp -4) and that the gas component dominates the planet's mass).

Mosqueira, I.↗
NASA NTRS2016

Testing and Resilience of the Impact Origin of the Moon

The leading hypothesis for the origin of the Moon is the giant impact model, which grew out of the post-Apollo science community. The hypothesis was able to explain the high E-M system angular momentum, the small lunar core, and consistent with the idea that the early Moon melted substantially. The standard hypothesis requires that the Moon be made entirely from the impactor, strangely at odds with the nearly identical oxygen isotopic composition of the Earth and Moon, compositions that might be expected to be different if Moon came from a distinct impactor. Subsequent geochemical research has highlighted the similarity of both geochemical and isotopic composition of the Earth and Moon, and measured small but significant amounts of volatiles in lunar glassy materials, both of which are seemingly at odds with the standard giant impact model. Here we focus on key geochemical measurements and spacecraft observations that have prompted a healthy re-evaluation of the giant impact model, provide an overview of physical models that are either newly proposed or slightly revised from previous ideas, to explain the new datasets.

Righter, K.↗
NASA NTRS2001

Jet Stability and the Generation of Superluminal and Stationary Components

We present a numerical simulation of the response of an expanding relativistic jet to the ejection of a superluminal component. The simulation has been performed with a relativistic time-dependent hydrodynamical code from which simulated radio maps are computed by integrating the transfer equations for synchrotron radiation. The interaction of the superluminal component with the underlying jet results in the formation of multiple conical shocks behind the main perturbation. These trailing components can be easily distinguished because they appear to be released from the primary superluminal component instead of being ejected from the core. Their oblique nature should also result in distinct polarization properties. Those appearing closer to the core show small apparent motions and a very slow secular decrease in brightness and could be identified as stationary components. Those appearing farther downstream are weaker and can reach superluminal apparent motions. The existence of these trailing components indicates that not all observed components necessarily represent major perturbations at the jet inlet; rather, multiple emission components can be generated by a single disturbance in the jet. While the superluminal component associated with the primary perturbation exhibits a rather stable pattern speed, trailing components have velocities that increase with distance from the core but move at less than the jet speed. The trailing components exhibit motion and structure consistent with the triggering of pinch modes by the superluminal component. The increase in velocity of the trailing components is an indirect consequence of the acceleration of the expanding fluid, which is assumed to be relativistically hot; if observed, such accelerations would therefore favor an electron-positron (as opposed to proton rest mass) dominated jet.

Agudo, Ivan↗
NASA NTRS2026

Hybrid Thermally Efficient Core (HyTEC) Phase 1 3-Stage Compressor Rig Final Report - Unlimited Rights

The HyTEC Phase 1 3-Stage Compressor Rig project was conducted to mature and validate front-stage aerodynamic technologies in support of HyTEC Phase 2 and GEA’s Compact Core compressor. Building on the prior ERA Phase 2 Baseline Rig, GEA and NASA collaborated on the design and testing of the HyTEC rig, incorporating advanced technologies such as increased radius ratio, higher aerodynamic loading, and advanced casing treatment. The HyTEC test campaign leveraged similar design and instrumentation philosophy, test execution approach, and the same facility (NASA W-7) to enable clear comparison with the legacy ERA rig results. The HyTEC rig was designed to deliver benefits in efficiency, tip loading, operability, and aeromechanics, with success measured against defined TPMs that were anchored to the ERA baseline rig data.

Axial Compressors↗
NASA NTRS2014

Proteins with Novel Structure, Function and Dynamics

Recently, a small enzyme that ligates two RNA fragments with the rate of 10(exp 6) above background was evolved in vitro (Seelig and Szostak, Nature 448:828‐831, 2007). This enzyme does not resemble any contemporary protein (Chao et al., Nature Chem. Biol. 9:81‐83, 2013). It consists of a dynamic, catalytic loop, a small, rigid core containing two zinc ions coordinated by neighboring amino acids, and two highly flexible tails that might be unimportant for protein function. In contrast to other proteins, this enzyme does not contain ordered secondary structure elements, such as alpha‐helix or beta‐sheet. The loop is kept together by just two interactions of a charged residue and a histidine with a zinc ion, which they coordinate on the opposite side of the loop. Such structure appears to be very fragile. Surprisingly, computer simulations indicate otherwise. As the coordinating, charged residue is mutated to alanine, another, nearby charged residue takes its place, thus keeping the structure nearly intact. If this residue is also substituted by alanine a salt bridge involving two other, charged residues on the opposite sides of the loop keeps the loop in place. These adjustments are facilitated by high flexibility of the protein. Computational predictions have been confirmed experimentally, as both mutants retain full activity and overall structure. These results challenge our notions about what is required for protein activity and about the relationship between protein dynamics, stability and robustness. We hypothesize that small, highly dynamic proteins could be both active and fault tolerant in ways that many other proteins are not, i.e. they can adjust to retain their structure and activity even if subjected to mutations in structurally critical regions. This opens the doors for designing proteins with novel functions, structures and dynamics that have not been yet considered.

Proteins↗
NASA NTRS1980

Study of sample drilling techniques for Mars sample return missions

To demonstrate the feasibility of acquiring various surface samples for a Mars sample return mission the following tasks were performed: (1) design of a Mars rover-mounted drill system capable of acquiring crystalline rock cores; prediction of performance, mass, and power requirements for various size systems, and the generation of engineering drawings; (2) performance of simulated permafrost coring tests using a residual Apollo lunar surface drill, (3) design of a rock breaker system which can be used to produce small samples of rock chips from rocks which are too large to return to Earth, but too small to be cored with the Rover-mounted drill; (4)design of sample containers for the selected regolith cores, rock cores, and small particulate or rock samples; and (5) design of sample handling and transfer techniques which will be required through all phase of sample acquisition, processing, and stowage on-board the Earth return vehicle. A preliminary design of a light-weight Rover-mounted sampling scoop was also developed.

Mitchell, D. C.↗
NASA NTRS1966

Plug replaces weld filler as seal in complex casting

Expandable metal plug is inserted to provide a seal to support the mold core with small blocks, referred to as chaplets, during the casting of a complex volute. Weld-warpage and multiple X ray inspection are eliminated by use of this technique.

Goundrey, R. L.↗
NASA NTRS1973

Digital data command bus

Command bus constructed from coaxial cable has short segments of its outer jacket and shield removed and replaced with small ferrite cores carrying multiturn windings connected to decoder. Device reduces number of wire pairs required to communicate command data to systems and subsystems.

Milligan, G. C.↗
NASA NTRS1974

Iron abundance and magnetic permeability of the moon

A set of simultaneous data from the Apollo 12 lunar surface magnetometer and the Explorer 35 Ames magnetometer are used to construct a whole-moon hysteresis curve, from which a new value of global lunar permeability is determined to be mu = 1.012 + or - 0.006. The corresponding global induced dipole moment is 2.1 x 10 to the 18th power gauss-cucm for typical inducing fields of .1000 gauss in the lunar environment. From the permeability measurement, lunar free iron abundance is determined to be 2.5 + or - 2.0 wt. %. Total iron abundance is calculated for two assumed compositional models of the lunar interior: a free iron/orthopyroxene lunar composition and a free iron/olivine composition. The overall lunar total iron abundance is determined to be 9.0 + or - 4.7 wt. %. Other lunar models with a small iron core and with a shallow iron-rich layer are discussed in light of the measured global permeability. Effects on permeability and iron content calculations due to a possible lunar ionosphere are also considered.

Parkin, C. W.↗
NASA NTRS1974

Magnetism and the interior of the moon

During the time period 1961-1972 eleven magnetometers were sent to the moon. The results of lunar magnetometer data analysis are reviewed, with emphasis on the lunar interior. Magnetic fields have been measured on the lunar surface at the Apollo 12, 14, 15, and 16 landing sites. The remanent field values at these sites are given. Satellite and surface measurements show strong evidence that the lunar crust is magnetized over much of the lunar globe. The origin of the lunar remanent field is not yet satisfactorily understood; several source models are presented. Simultaneous data from the Apollo 12 lunar surface magnetometer and the Explorer 35 Ames magnetometer are used to construct a wholemoon hysteresis curve, from which the global lunar permeability is determined. Total iron abundance is calculated for two assumed compositional models of the lunar interior. Other lunar models with a small iron core and with a shallow iron-rich layer are also discussed in light of the measured global permeability.

Dyal, P.↗
NASA NTRS1974

Iron abundance and magnetic permeability of the moon

A larger set of simultaneous data from the Apollo 12 lunar surface magnetometer and the Explorer 35 Ames magnetometer are used to construct a whole-moon hysteresis curve, from which a new value of global lunar permeability is determined to be mu = 1.012 + or - 0.006. The corresponding global induced dipole moment is 2.1 x 10 to the 18th power gauss-cu cm for typical inducing fields of .0001 gauss in the lunar environment. From the permeability measurement, lunar free iron abundance is determined to be 2.5 + or - 2.0 wt. %. Total iron abundance (sum of iron in the ferromagnetic and paramagnetic states) is calculated for two assumed compositional models of the lunar interior: a free iron/orthopyroxene lunar composition and a free iron/olivine composition. The overall lunar total iron abundance is determined to be 9.0 + or - 4.7 wt. %. Other lunar models with a small iron core and with a shallow iron-rich layer are discussed in light of the measured global permeability.

Parkin, C. W.↗
NASA NTRS1974

Iron abundance and magnetic permeability of the moon

A larger set of simultaneous data from the Apollo 12 lunar surface magnetometer and the Explorer 35 Ames magnetometer are used to construct a whole-moon hysteresis curve, from which a new value of global lunar permeability is determined to be mu = 1.012 + or - 0.006. The corresponding global induced dipole moment is 2.1 times ten to the eighteenth power gauss-cu cm for typical inducing fields of one ten-thousandth gauss in the lunar environment. From the permeability measurement, lunar free iron abundance is determined to be 2.5 + or - 2.0 wt %. Total iron abundance (sum of iron in the ferromagnetic and paramagnetic states) is calculated for two assumed compositional models of the lunar interior: a free iron/orthopyroxene lunar composition and a free iron/olivine composition. The overall lunar total iron abundance is determined to be 9.0 + or - 4.7 wt %. Other lunar models with a small iron core and with a shallow iron-rich layer are discussed in light of the measured global permeability. Effects on permeability and iron content calculations due to a possible lunar ionosphere are also considered.

Parkin, C. W.↗