Search NASA⌕ Search

SEARCH · Search NASA

Results for “fine”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Additive Manufactured Ultra-Fine Lattice Structures for Propulsion Catalysts

Traditional mono-propulsion catalysts consist of coated ceramic or graphite foams that possess anisotropic mechanical and fluid properties limiting design, cost, availability, and operational use. Ultra-fine lattice structures are repeating unit cells with ligament thickness as small as 100 μm produced via Additive manufacture (AM). These lattice structures have the potential to replace coated foams used in a mono-propellant system catalysts. AM ultra-fine lattice structures are designed to mimic the operational intent of coated foams but with improved design flexibility, compressive strength, and flow behavior printed from into a single part directly from the preferred platinum metal alloy. The investigation objective was to conduct feasibility studies of AM ultra-fine lattice structures capable of replacing coated foams with superior functionality. NASA MSFC identified desired lattice characteristics and created designs while EOS developed optimized laser powder bed fusion AM parameters to manufacture Ti6Al4V and tungsten specimens. Optimized designs, computational tools, AM parameters, and post-process methods were developed. Specimens underwent x-ray micro-focus CT, metallographic inspection, compression testing, and flow testing. Results demonstrate that AM ultra-fine lattices improved geometric and performance repeatability with the potential for significantly increased availability while decreasing cost and lead time.

Omar R Mireles↗
NASA NTRS2018

JWST Cryo Fine Guidance Closed Loop Test Results

The James Webb Space Telescope uses the Fine Guidance Controller to achieve pointing accuracy to a millionth of a degree needed for its scientific observations. This closed loop controller includes the Fine Guidance Sensor instrument, the Attitude Control System, and the Fine Steering Mirror, all working together to generate precise attitude updates every 64 ms to stabilize and point the Observatory. It was exercised for the first time with the flight hardware during the cryogenic test at Johnson Space Center. We provide a top level summary of the test, the results, and its performance in preparation for on-orbit operations.

Line of Sight↗
NASA NTRSDate not supplied

Orbital Drag Near Small Bodies Due to Lofted Fines from Surface Activity

Recent exploratory missions have revealed that small bodies are more granular and dusty than previously expected. As a result of landings, mining, impacts, or other natural phenomena, bodies with negligible atmospheres such as moons and asteroids may experience an exospheric environment abundant in lofted fines. Significant quantities of these may interfere with the nominal trajectories of spacecraft in low orbits. This paper applies data collected from remote sensor and direct sample collection to approximate the density of atmospheric fines in three environments: high-velocity lunar fines generated during landings, the coma of active comets, and cryovolcanic plumes from the Saturnian moon Enceladus. It also investigates the threshold of activity that would induce concerns about a spacecraft's nominal mission. Coupled motion of spacecraft navigation and control is expressed in SE(3).

Fines↗
NASA NTRS1973

Effect of fineness ratio on boattail drag of circular-arc afterbodies having closure ratios of 0.50 with jet exhaust at Mach numbers up to 1.30

An investigation was conducted to determine the effect of fineness ratio on the drag of circular-arc boattails at subsonic and low supersonic speeds. The boattails had closure ratios of 0.50 and incorporated convergent nozzles. The investigation was conducted statically and at Mach numbers from 0.40 to 1.30 at 0 deg angle of attack with jet total-pressure ratios varying from jet off to about 6, depending on Mach number. Low-fineness-ratio boattails had large separated-flow regions and the highest drag at all Mach numbers. Subsonic pressure-plus-friction drag levels were generally similar for boattails which did not have large separated regions. Drag-rise Mach number increased as boattail fineness ratio increased.

Reubush, D. E.↗
NASA NTRS1973

Effects of fineness and closure ratios on boattail drag of circular-arc-afterbody models with jet exhaust at Mach numbers up to 1.3

The effects of variations in fineness ratio and closure ratio on the boattail drag of circular-arc afterbody models were investigated at static conditions and at Mach numbers from 0.40 to 1.30. Jet total-pressure ratio was varied from jet off to about 6, depending on Mach number. Reynolds number based on model maximum diameter varied from about 1.2 million to 2.18 million. Angle of attack was varied from -4 deg to 8 deg. The results indicate that, at subsonic speeds before the drag rise and at a scheduled pressure ratio, the total drag (pressure plus calculated skin friction) is approximately equal for configurations with the same closure ratio. Also, for configurations with the same closure ratio, increasing fineness ratio results in an increased drag-rise Mach number; and for configurations with the same fineness ratio, increasing closure ratio results in an increased drag-rise Mach number.

Reubush, D. E.↗
NASA NTRS1972

Analyses of the returned lunar surface fines for porphyrins.

Apollo 11, 12, and 14 lunar surface fines were examined for the presence of porphyrins by a sensitive fluorescent technique. The returned lunar samples studied were of bulk fines collected from the Sea of Tranquillity by Apollo 11, from the Ocean of Storms by Apollo 12, and from the nonmare Fra Mauro formation by Apollo 14. It was found that no porphyrins are present in lunar surface fines which have been extensively irradiated and sorted.

Rho, J. H.↗
NASA NTRS1973

Petrology of fine-grained rock fragments and petrologic implications of single crystal from the Luna 20 soil.

Only fine-grained rocks are present in the Luna 20 samples, and coarser-grained rocks are represented by fragments of single crystals. A petrologic study has been made of 47 fine-grained crystalline rocks, microbreccias, and glassy aggregates. In addition, a total of 33 single crystals of pyroxene, plagioclase, olivine, and spinel, in the size range from 125 to 500 microns, have been examined using electron microprobe and single-crystal X-ray diffraction techniques. The most abundant fine-grained crystalline rocks in the samples examined are recrystallized anorthositic norite and anorthositic troctolite. Gabbroic rocks, anorthosite, and KREEP basalt are present but not common. Most of the single crystals of pyroxene and plagioclase could have been derived from coarser-grained noritic, troctolitic, and anorthositic rocks. However, three of the 14 pyroxene crystals, and two of the five olivine crystals have Fe/(Fe + Mg) contents greater than 0.45 and are believed to have been derived from mare basalts or related rocks.

Cameron, K. L.↗
NASA NTRS1973

Magnetic phases in lunar fines - Metallic Fe or ferric oxides.

The ferromagnetic resonance observed for the Apollo 11 and 12 lunar fines is characterized by an asymmetric lineshape with a narrower appearance on the high field side. This asymmetry together with an anisotropy energy which varies from +640 to +500 G over the temperature range of 80 to 298 K indicate that the ferromagnetic resonance arises from metallic Fe having the body-centered cubic structure and not from hematite, magnetite or other Fe(3+) ions in magnetite-like phases. The g-value, the lineshape asymmetry, and the temperature dependence of the linewidth for the Apollo 14 and 15 fines as reported by other workers are found to be essentially similar to those observed for the Apollo 11 and 12 fines.

Tsay, F.-D.↗
NASA NTRS1973

Seismic properties of fine rock powders in lunar conditions.

Seismic properties of fine rock powders in near lunar surface conditions have been measured in the laboratory, and they correspond well with those obtained for the near lunar surface. The laboratory values of Q range from 40 to 330 with corresponding wave velocities below 100 m/sec. Many of the results obtained are shown to be understandable in terms of current theories of the elastic and plastic properties of fine rock powders in a variety of temperature and pressure conditions. This enables some estimate to be made of the changes in Q and wave velocity with depth in the moon, on the supposition that fine rock powder continues downward as an abundant constituent.

Jones, B. W.↗
NASA NTRS1973

A fine pointing system for the large space telescope

The large space telescope (LST) developed by NASA requires ultrahigh pointing stability within 0.0005 arc sec rms. A fine guidance system is proposed to body-point the entire spacecraft within this limit. The spacecraft is modeled as a rigid body having reaction wheel actuators and subject to gravitational and magnetic disturbance torques. The fine guidance sensor is cluttered with electronic noise. The disturbance accommodation standard deviation optimal controller (DASOC) is designed to be optimal with respect to the transient and the steady state response to noise, whereas the steady state response to deterministic external torques is exactly zero. Compared with conventional controllers, the fine guidance system with the DASOC offers as much as a factor of 30 improvement in pointing stability, resulting in an optimal performance of nearly 0.0001 arc sec rms. Thus, the required pointing stability can easily be obtained, and a large margin remains for the compensation of possibile deteriorations.

Schiehlen, W. O.↗
NASA NTRS1973

Distribution of inert gases in fines from the Cayley-Descartes region

The inert gases in 14 different fines and in one sample of 2 to 4 mm fines from Apollo 16 were measured by mass spectroscopy with respect to trapped solar wind gases, cosmogenic gases, and 'parentless' Ar-40. Such studies are helpful for the understanding of regolith evolution, of transport of regolith fines, and of the lunar atmosphere. The Apollo 16 soils are unique because they represent, after Luna 20, the second and much more extensive record from the lunar highlands. The landing site presents the problem of materials from the Cayley Formation vs those from the Descartes Formation. There are two large, relatively fresh craters in the area, North Ray and South Ray, whose ejecta patterns may be recognized in the inert-gas record.

Walton, J. R.↗
NASA NTRS1973

Ferromagnetic phases of lunar fines and breccias - Electron magnetic resonance spectra of Apollo 16 samples

Electron magnetic resonance measurements have been made at 9 GHz and at temperatures from 1.2 to 400 K and 35 GHz (300 K) on samples of fines and breccias from Apollo 11-16. Unsorted Apollo 16 fines (less than 1 mm) have Delta H (average) = 580 G and specific intensities that have the same range as fines from the other Apollo collections. The magnetic properties of the 'characteristic' resonance are not in accord with those of iron particles. On the bases of the properties of the 'characteristic' resonance as a function of temperature and Apollo site, laboratory heat treatments on synthetic materials and lunar crystalline rocks and a comparison with the 'characteristic' resonance of the resonance spectra of breccia specimens for which iron particle sizes have been determined from other measurements, it is suggested that some fraction (about 20%) of the 'characteristic' resonance is due to sub-micron particles of ferric oxide phases.

Weeks, R. A.↗
NASA NTRS1974

Thermal conductivity of Apollo 15 lunar fines

The moon is covered to a depth of several meters with fine material. Heat transfer calculations depend, therefore, for the most part on the properties of the fines. The results are presented of thermal conductivity measurements on fines samples returned by the Apollo 15 mission from the Hadley-Apennine region of the moon. Data are presented as a function of both density and temperature with typical lunar values being used for these parameters.

Cremers, C. J.↗
NASA NTRS1975

Compaction by impact of unconsolidated lunar fines

An investigation was conducted concerning the macroscopic irreversible partial compaction of terrestrial or lunar fines. A sample material (70051), assumed to be typical of the fines in the unconsolidated material of the lunar regolith, was used in the experiments. Tests were also carried out with powdered Vacaville basalt. Release adiabate and Hugoniot measurements were conducted. It was found that the dynamic stresses required for irreversible compaction of lunar fines on the moon are significantly lower than the values inferred from the shock recovery experiments conducted by Christie et al. (1973).

Ahrens, T. J.↗
NASA NTRS1976

A simulation for gravity fine structure recovery from high-low GRAVSAT SST data

Covariance error analysis techniques were applied to investigate estimation strategies for the high-low SST mission for accurate local recovery of gravitational fine structure, considering the aliasing effects of unsolved for parameters. Surface density blocks of 5 deg x 5 deg and 2 1/2 deg x 2 1/2 deg resolution were utilized to represent the high order geopotential with the drag-free GRAVSAT configured in a nearly circular polar orbit at 250 km. altitude. GEOPAUSE and geosynchronous satellites were considered as high relay spacecraft. It is demonstrated that knowledge of gravitational fine structure can be significantly improved at 5 deg x 5 deg resolution using SST data from a high-low configuration with reasonably accurate orbits for the low GRAVSAT. The gravity fine structure recoverability of the high-low SST mission is compared with the low-low configuration and shown to be superior.

Estes, R. H.↗
NASA NTRS1977

Ar-40 intercept values and young apparent /K-40/-/Ar-40/ ages of five Apollo 15 fines

Correlations between Ar-40 and Ar-36 from size fractions of three Apollo 15 fines (15071, 15421, 15501) have been obtained. The Ar-40 intercept values of these fines and of 15091 and 15601 are generally lower than what one would expect for fines resulting from the comminution of rocks having ages of about 3.3 billion yr, typical for basalts of the landing site. This is interpreted to be the result of contamination by ray material from the Copernican age (equal or less than about 1 billion yr) craters, Autolycus and Aristillus, north of the landing site.

Jordan, J. L.↗
NASA NTRS1978

On the interactions between large-scale structure and fine-grained turbulence in a free shear flow. II - The development of spatial interactions in the mean

The interactions between large-scale structure and fine-grained turbulence in a spatially developing mixing layer are investigated. Both a conditioned average and a time average are employed to separate the nonrandom and random fluctuations in the kinetic energy treatment of the interactions. Shape assumptions applying to the interaction integrals are adopted to obtain a solution to the closure problem. Energy-transfer mechanisms among the mean flow, the fine-grained turbulence and the large-scale structure are discussed. The magnitude of the large-scale structure and its streamwise lifetime both prove to be important in accounting for fine-grained turbulence enhancement.

Alper, A.↗
NASA NTRS1975

Inert gases in fines at three levels of the trench at Van Serg Crater

Inert-gas measurements were conducted with three soil samples collected from a trench of about 17 cm depth which had been dug at Station 9, approximately 60-m southeast of the rim of Van Serg Crater on the moon. The particular trench is interesting because it is located in the continuous ejecta blanket of a relatively young crater. The results of the inert-gas measurements are presented in a table. They confirm an earlier conclusion reported by Heymann et al. (1974) that fines from Station 9 are among the most gas rich in the whole landing site. The three fines are agglutinate rich and most of the trapped gas is contained in the constructional particles. Agglutinate contents of fines tend to decrease rapidly for particles greater than about 250 micrometers.

Jordan, J. L.↗