Search NASA⌕ Search

SEARCH · Search NASA

Results for “Proximity effects”

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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Geosynchronous platform definition study. Volume 4, Part 1: Traffic analysis and system requirements for the baseline traffic model

The traffic analyses and system requirements data generated in the study resulted in the development of two traffic models; the baseline traffic model and the new traffic model. The baseline traffic model provides traceability between the numbers and types of geosynchronous missions considered in the study and the entire spectrum of missions foreseen in the total national space program. The information presented pertaining to the baseline traffic model includes: (1) definition of the baseline traffic model, including identification of specific geosynchronous missions and their payload delivery schedules through 1990; (2) Satellite location criteria, including the resulting distribution of the satellite population; (3) Geosynchronous orbit saturation analyses, including the effects of satellite physical proximity and potential electromagnetic interference; and (4) Platform system requirements analyses, including satellite and mission equipment descriptions, the options and limitations in grouping satellites, and on-orbit servicing criteria (both remotely controlled and man-attended).

Source record↗
NASA NTRS1978

Definition study of the Shuttle Imaging Radar-A (SIR-A) antenna on the second space shuttle mission (OFT-2)

A definition is derived for an antenna configuration fixed-mounted high in the payload bay on the hybrid OFT-2 pallet which is compatible with Orbiter interface requirements. Tests showed that the combination of the selected panels and the designed corporate feed meets SIR-A performance requirement of 33 db gain. The effects of Orbiter structure proximity on performance were determined by scale model tests to be negligible. The potential for improved performance during subsequent reflights includes a multiple-beam capability and dual polarization.

Nitschke, H. A.↗
NASA NTRS1978

Definition study of the Shuttle Imaging Radar-A /SIR-A/ antenna on the second Space Shuttle mission /OFT-2/

The study resulted in the definition of an antenna configuration fixed-mounted high in the payload bay on the hybrid OFT-2 pallet which is compatible with Orbiter interface requirements. Tests showed that the combination of the selected panels and the designed corporate feed will meet the SIR-A performance requirement of 33 dB gain. The effects of Orbiter structure proximity on performance were determined by scale model tests to be negligible. The potential for improved performance during subsequent reflights includes a multiple-beam capability and dual polarization.

Nitschke, H. A.↗
NASA NTRS1983

Improved method for transonic airfoil design-by-optimization

An improved method for use of optimization techniques in transonic airfoil design is demonstrated. FLO6QNM incorporates a modified quasi-Newton optimization package, and is shown to be more reliable and efficient than the method developed previously at NASA-Ames, which used the COPES/CONMIN optimization program. The design codes are compared on a series of test cases with known solutions, and the effects of problem scaling, proximity of initial point to solution, and objective function precision are studied. In contrast to the older method, well-converged solutions are shown to be attainable in the context of engineering design using computational fluid dynamics tools, a new result. The improvements are due to better performance by the optimization routine and to the use of problem-adaptive finite difference step sizes for gradient evaluation.

Kennelly, R. A., Jr.↗
NASA NTRS1983

Improved method for transonic airfoil design-by-optimization

An improved method for use of optimization techniques in transonic airfoil design is demonstrated. FLO6QNM incorporates a modified quasi-Newton optimization package, and is shown to be more reliable and efficient than the method developed previously at NASA-Ames, which used the COPES/CONMIN optimization problem. The design codes are compared on a series of test cases with known solutions, and the effects of problem scaling, proximity of initial point to solution, and objective function precision are studied. In contrast to the older method, well-converged solutions are shown to be attainable in the context of engineering design using computational fluid dynamics tools, a new result. The improvements are due to better performance by the optimization routine and to the use of problem-adaptive finite difference step sizes for gradient evaluation.

Kennelly, R. A., Jr.↗
NASA NTRS1991

Proposal for a low cost close air support aircraft for the year 2000: The Raptor

The Raptor is a proposed low cost Close Air Support (CAS) aircraft for the U.S. Military. The Raptor incorporates a 'cranked arrow' wing planform, and uses canards instead of a traditional horizontal tail. The Raptor is designed to be capable of responsive delivery of effective ordnance in close proximity to friendly ground forces during the day, night, and 'under the weather' conditions. Details are presented of the Raptor's mission, configuration, performance, stability and control, ground support, manufacturing, and overall cost to permit engineering evaluation of the proposed design. A description of the design process and analysis methods used is also provided.

Brown, Jerome D.↗
NASA NTRS2024

Winter Lightning to the Lee of Lake Ontario: The Lake-Effect Electrification (LEE) Field Campaign

The National Science Foundation-sponsored Lake-Effect Electrification (LEE) field campaign intensive observation periods occurred between November and early February 2022-23 across the eastern Lake Ontario region. Project LEE documented, for the first time, the total lightning and electrical charge structures of lake-effect storms and the associated storm environment using a lightning mapping array (LMA), a mobile dual-polarization X-band radar, and balloon-based soundings that measured vertical profiles of temperature, humidity, wind, electric field, and hydrometeor types. LEE also observed abundant wind turbine-initiated lightning, which is climatologically more likely during the winter. The frequent occurrence of intense lake-effect storms and the proximity of a wind farm with nearly 300 turbines each more than 100 m tall to the lee of Lake Ontario provided an ideal laboratory for this study.

Scott M Steiger↗
NASA NTRS1982

Experimental determination of flow-interference effects of wing-mounted, two-dimensional, full-capture propulsion nacelles in close proximity to a vehicle body at a Mach number of 6

Experimental tests have been conducted to determine possible aerodynamic interference effects due to the lateral positioning of two dimensional propulsion nacelles mounted on a wing surface in close proximity to a vehicle body. The tests were conducted at a Mach number of 6 and a Reynolds number 7 million per foot. The angle of attack range for force tests was -9 deg to 9 deg. The model configurations consisted of combinations of rectangular and trapezoidal cross section bodies with a wing swept 65 and a rectangular planform wing. A pair of two dimensional, flow through propulsion nacelles simulated full capture inlet operation.

Vahl, W. A.↗
NASA NTRS1930

An Investigation of Airplane Landing Speeds

This paper describes an investigation on airplane landing speeds which was made to determine the applicability of accepted aerodynamic theory to the prediction of this particular performance characteristic. The experimental work consisted in measuring the landing speed of several monoplanes by a new photographic method. The results of these tests supplemented by available information regarding biplanes were compared with predictions made with basic aerodynamic theory. The prediction makes use of the fundamental relation between wing loading, lift coefficient, and speed of level flight, and the effects of aspect ratio and proximity to the ground on lift curve slope.

LANDING SPEED - BIPLANES↗
NASA NTRS1978

On the tidal oscillations of the liquid core of the earth

An important goal of a tidal theory is the improvement of nutational amplitude and of the parameters of the earth's elastic response. A theory of tidal oscillations inside a rotating elliptical earth was developed, with special emphasis on tides in the liquid core. The Molodensky and Kramer theory of the resonance effect, as caused by the proximity of the frequency of the free diurnal wobble of the liquid core to the frequency of K sub 1 astronomical tide, was amended to include the effect of the possible deviation of the liquid core from the state of neutral stability. Coupling effects between the toroidal and spheroidal oscillations, as caused by the Coriolis force, were taken into consideration.

Musen, P.↗
NASA NTRS2017

Bone and Cartilage Degeneration in Mice Following Long-Duration Spaceflight: The Role of Bone Marrow Stem Cells

The detrimental effects of mechanical unloading in microgravity, including the musculo-skeletal system, are well documented. However, the effects of mechanical unloading on joint health and the interaction between bone and cartilage specifically, are less well known. Our ongoing studies with the mouse bone model have identified the failure of normal stem cell-based tissue regeneration, in addition to tissue degeneration, as a significant concern for long-duration spaceflight, especially in the mesenchymal and hematopoietic tissue lineages. Furthermore, we have identified the cell cycle arrest molecule, CDKN1ap21, as specifically up-regulated during spaceflight exposure and localized to osteoprecursors on the bone surface and chondroprogenitors in articular cartilage that are both required for normal tissue regeneration. The 30-day BionM1 and 37-day Rodent Research 1 (RR1) missions enabled the possibility of studying these effects in long-duration microgravity experiments. We hypothesized that the inhibition of stem cell-based tissue regeneration in short-duration spaceflight would continue during long-duration spaceflight resulting in significant tissue alterations and we specifically studied the hip joint (pelvis and proximal femur) to elucidate these effects. To test this hypothesis we analyzed bone and bone marrow stem cells using techniques including high-resolution Microcomputed Tomography (MicroCT), in-vivo differentiation and migration assays, and whole transcriptome expression profiling. We found that exposure to spaceflight for 30 days results in a significant decrease in bone volume fraction (-31), trabecular thickness (-14) and trabecular number (-20). Similar decrements in bone volume fraction (-27), trabecular number (-13) and trabecular thickness (-17) were found in female mice exposed to 37 days spaceflight. Furthermore, high-resolution MicroCT and immunohistochemical analysis of spaceflight tissues revealed a severe disruption of the epiphyseal boundary, resulting in endochondral ossification of the femoral head and perforation of articular cartilage by bone. This suggests that spaceflight in microgravity may cause rapid induction of an aging-like phenotype with signs of osteoarthritic disease in the hip joint. Microarray analysis also revealed that the top pathways altered during spaceflight include activation of matrix metalloproteinases, oxidative stress signaling and inflammation in both whole bone tissue and isolated bone marrow stem cells. In conclusion, the observed inhibition of stem cell-based tissue regeneration persists during long-duration spaceflight. Furthermore, spaceflight mice exhibit disruption of the epiphyseal boundary and endochondral ossification of the femoral head, and an inhibition of stem cell based tissue regeneration, which, taken together, may indicate onset of an accelerated aging phenotype with signs of osteoarthritic disease.

Cartilage↗
NASA NTRS1984

An experimental investigation of the parallel blade-vortex interaction

A scheme for investigating the parallel blade vortex interaction (BVI) has been designed and tested. The scheme involves setting a vortex generator upstream of a nonlifting rotor so that the vortex interacts with the blade at the forward azimuth. The method has revealed two propagation mechanisms: a type C shock propagation from the leading edge induced by the vortex at high tip speeds, and a rapid but continuous pressure pulse associated with the proximity of the vortex to the leading edge. The latter is thought to be the more important source. The effects of Mach number and vortex proximity are discussed.

Caradonna, F. X.↗
NASA NTRS1984

An experimental investigation of the parallel blade-vortex interaction

A scheme for investigating the parallel blade vortex interaction (BVI) has been designed and tested. The scheme involves setting a vortex generator upstream of a nonlifting rotor so that the vortex interacts with the blade at the forward azimuth. The method has revealed two propagation mechanisms: a type C shock propagation from the leading edge induced by the vortex at high tip speeds, and a rapid but continuous pressure pulse associated with the proximity of the vortex to the leading edge. The latter is thought to be the more important source. The effects of Mach number and vortex proximity are discussed.

Caradonna, F. X.↗
NASA NTRS2002

A Small-Scale Tiltrotor Model Operating in Descending Flight

As a rotor s descent velocity in low speed flight approaches the induced wake velocity, a vortex ring is formed around the circumference of the rotor disk causing the flow to become very unsteady. This condition is known as Vortex Ring State (VRS). The aerodynamic Characteristics of edgewise operating rotors in this VRS induced environment have been studied for many years. In the 1960 s, two propellers were tested in vertical or near vertical descent, indicating a loss in thrust in the region of VRS. Thrust fluctuations of both single and tandem rotor configurations while operating in VRS were reported. More recently, the effects of descending flight on a single rotor operating in close proximity to a physical image plane, simulating the effects of a twin rotor tiltrotor system were investigated. Mean rotor thrust reductions and thrust fluctuations were shown in VRS. Results indicated the need to acquire additional data with a two-rotor model and the need to investigate the use of a single rotor/image plane apparatus to identify the characteristics of a two-rotor flowfield. As a result a small-scale tiltrotor model with 2-b1adedy untwisted, teetering rotors was tested at various states of descent and sideslip. Dual-rotor, single-rotor with image plane, and isolated-rotor results were reported, suggesting the single-rotor with image plane configuration may not properly capture the aerodynamic nature of a dual-rotor vehicle. Recommendations included additional testing of a model that better represents the physical characteristics of a tiltrotor aircraft. Specific recommendations for model improvements included using three-bladed rotors, twisted blades, a tiltrotor fuselage and wings.

Abrego, Anita I.↗
NASA NTRS2015

Experimental Investigation of Rotorcraft Outwash in Ground Effect

The wake characteristics of a rotorcraft are affected by the proximity of a rotor to the ground surface, especially during hover. Ground effect is encountered when the rotor disk is within a distance of a few rotor radii above the ground surface and results in an increase in thrust for a given power relative to that same power condition with the rotor out of ground effect. Although this phenomenon has been highly documented and observed since the beginning of the helicopter age, there is still a relatively little amount of flow-field data existing to help understand its features. Joint Army and NASA testing was conducted at NASA Langley Research Center using a powered rotorcraft model in hover at various rotor heights and thrust conditions in order to contribute to the complete outwash data set. The measured data included outwash velocities and directions, rotor loads, fuselage loads, and ground pressures. The researchers observed a linear relationship between rotor height and percent download on the fuselage, peak mean outwash velocities occurring at radial stations between 1.7 and 1.8 r/R regardless of rotor height, and the measurement azimuthal dependence of the outwash profile for a model incorporating a fuselage. Comparisons to phase-locked PIV data showed similar contours but a more contracted wake boundary for the PIV data. This paper describes the test setup and presents some of the averaged results.

Tanner, Philip E.↗
NASA NTRS1997

Effect of Elevated Carbon Dioxide on Nutritional Quality of Tomato

Tomato (Lycopersicon esculentum Mill.) cvs. Red Robin (RR) and Reimann Philipp (RP) were grown hydroponically for 105 d with a 12 h photoperiod, 26 C/22 C thermoperiod, and 500 micromol/ sq m/s PPF at either 400, 1200, 5000, or 10,000 micromol/mol (0.04, 0.12, 0.50, 1.00 kPa) CO2. Harvested fruits were analyzed for proximate composition, total dietary fiber, nitrate, and elemental composition. No trends were apparent with regard to CO2 effects on proximate composition, with fruit from all treatments and both cultivars averiging 18.9 % protein, 3.6 % fat, 10.2 % ash, and 67.2 % carbohydrate. In comparison, average values for field-grown fruit are 16.6 % protein, 3.8 % fat, 8.1 % ash, and 71.5 % carbohydrate (Duke and Atchely, 1986). Total dietary fiber was highest at 10,000 micromol/mol (28.4 % and 22.6 % for RR and RP) and lowest at 1000 micromol/mol (18.2 % and 15.9 % for RR and RP), but showed no overall trend in response to CO2. Nitrate values ranged from 0.19 % to 0.35 % and showed no trend with regard to CO2. K, Mg, and P concentrations showed no trend in response to CO2, but Ca levels increased from 198 and 956 ppm in RR and RP at 400 micromol/mol, to 2537 and 2825 ppm at 10,000 micromol/mol. This increase in Ca caused an increase in fruit Ca/P ratios from 0.07 and 0.37 for RR and RP at 400 micromol/molto 0.99 and 1.23 for RR and RP at 10,000 micromol/mol suggesting that more dietary Ca should be available from high CO2-grown fruit.

Wheeler, R. M.↗