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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Investigation of two-dimensional wedge exhaust nozzles for advanced aircraft

Two-dimensional wedge nozzle performance characteristics were investigated in a series of wind-tunnel tests. An isolated single-engine/nozzle model was used to study the effects of internal expansion area ratio, aftbody cowl boattail angle, and wedge length. An integrated twin-engine/nozzle model, tested with and without empenage surfaces, included cruise, acceleration, thrust vectoring and thrust reversing nozzle operating modes. Results indicate that the thrust-minus-aftbody drag performance of the twin two-dimensional nozzle integration is significantly higher, for speeds greater than Mach 0.8, than the performance achieved with twin axisymmetric nozzle installations. Significant jet-induced lift was obtained on an aft-mounted lifting surface using a cambered wedge center body to vector thrust. The thrust reversing capabilities of reverser panels installed on the two-dimensional wedge center body were very effective for static or in-flight operation.

Maiden, D. L.↗
NASA NTRS1977

Nonplanar wing load-line and slender wing theory

Nonplanar load line, slender wing, elliptic wing, and infinite aspect ratio limit loading theories are developed. These are quasi two dimensional theories but satisfy wing boundary conditions at all points along the nonplanar spanwise extent of the wing. These methods are applicable for generalized configurations such as the laterally nonplanar wing, multiple nonplanar wings, or wing with multiple winglets of arbitrary shape. Two dimensional theory infers simplicity which is practical when analyzing complicated configurations. The lateral spanwise distribution of angle of attack can be that due to winglet or control surface deflection, wing twist, or induced angles due to multiwings, multiwinglets, ground, walls, jet or fuselage. In quasi two dimensional theory the induced angles due to these extra conditions are likewise determined for two dimensional flow. Equations are developed for the normal to surface induced velocity due to a nonplanar trailing vorticity distribution. Application examples are made using these methods.

Deyoung, J.↗
NASA NTRS1992

Inverse design of a proper number, shapes, sizes, and locations of coolant flow passages

During the past several years we have developed an inverse method that allows a thermal cooling system designer to determine proper sizes, shapes, and locations of coolant passages (holes) in, say, an internally cooled turbine blade, a scram jet strut, a rocket chamber wall, etc. Using this method the designer can enforce a desired heat flux distribution on the hot outer surface of the object, while simultaneously enforcing desired temperature distributions on the same hot outer surface as well as on the cooled interior surfaces of each of the coolant passages. This constitutes an over-specified problem which is solved by allowing the number, sizes, locations and shapes of the holes to adjust iteratively until the final internally cooled configuration satisfies the over-specified surface thermal conditions and the governing equation for the steady temperature field. The problem is solved by minimizing an error function expressing the difference between the specified and the computed hot surface heat fluxes. The temperature field analysis was performed using our highly accurate boundary integral element code with linearly varying temperature along straight surface panels. Examples of the inverse design applied to internally cooled turbine blades and scram jet struts (coated and non-coated) having circular and non-circular coolant flow passages will be shown.

George S. Dulikravich↗
NASA NTRS2015

Parallel Study of HEND, RAD, and DAN Instrument Response to Martian Radiation and Surface Conditions

Nuclear detection methods are being used to understand the radiation environment at Mars. JPL (Jet Propulsion Laboratory) assets on Mars include: Orbiter -2001 Mars Odyssey [High Energy Neutron Detector (HEND)]; Mars Science Laboratory Rover -Curiosity [(Radiation Assessment Detector (RAD); Dynamic Albedo Neutron (DAN))]. Spacecraft have instruments able to detect ionizing and non-ionizing radiation. Instrument response on orbit and on the surface of Mars to space weather and local conditions [is discussed] - Data available at NASA-PDS (Planetary Data System).

Mars↗
NASA NTRS1975

Theory of an airfoil equipped with a jet flap under low-speed flight conditions

A theory is developed, for the inviscid, incompressible flow past a thin airfoil equipped with a thin, part-span jet flap, by treating the induced flowfields of the jet and the wing separately and by obtaining the fully coupled solution in an iterative manner. Spanwise variation of the jet vortex strength is assumed to be elliptical in the analysis. Since the method considers the vorticity associated with the jet to be positioned on the computed locus of the jet, the downwash aft of the wing is evaluated as well as forces and moments on the wing. A lifting-surface theory is incorporated for the aerodynamics of the wing. Computational results are presented for a rectangular wing at momentum coefficients above 2.0 and compared with existing linear theories and experimental data. Good agreement is found for small angles of attack, jet-deflection angles, and jet-momentum coefficients where the linear theories and experimental data are applicable. Downwash data at a point in the vicinity of a control surface, the load distribution on the airfoil, and the jet, and the jet location are also presented for representative flight conditons.

Addessio, F. L.↗
NASA NTRS1972

Acoustic results obtained with upper-surface-blowing lift augmentation systems

The noise caused by the interaction of the jet exhaust and a wing was measured under static conditions for several versions of a small-scale STOL engine-over-the-wing configuration. Three basic nozzles were used in the tests; a circular nozzle, a 5:1 aspect ratio slot nozzle and a 10:1 aspect ratio slot nozzle. Various flow attachment devices were included in the study. The wing included a flap that could be positioned for nominal takeoff or approach flap settings. Far field noise data are presented for the flyover mode. The data are discussed in terms of sound power and sound pressure spectra. Implications of extending the small-scale model acoustic data to full-scale aircraft are discussed briefly and indicate a sizeable flyover noise attenuation may be achieved due to shielding by the wing.

Vonglahn, U. H.↗
NASA NTRS2008

Experimental Measurement of RCS Jet Interaction Effects on a Capsule Entry Vehicle

An investigation was made in NASA Langley Research Center s 31-Inch Mach 10 Tunnel to determine the effects of reaction-control system (RCS) jet interactions on the aft-body of a capsule entry vehicle. The test focused on demonstrating and improving advanced measurement techniques that would aid in the rapid measurement and visualization of jet interaction effects for the Orion Crew Exploration Vehicle while providing data useful for developing engineering models or validation of computational tools used to assess actual flight environments. Measurements included global surface imaging with pressure and temperature sensitive paints and three-dimensional flow visualization with a scanning planar laser induced fluorescence technique. The wind tunnel model was fabricated with interchangeable parts for two different aft-body configurations. The first, an Apollo-like configuration, was used to focus primarily on the forward facing roll and yaw jet interactions which are known to have significant aft-body heating augmentation. The second, an early Orion Crew Module configuration (4-cluster jets), was tested blowing only out of the most windward yaw jet, which was expected to have the maximum heating augmentation for that configuration. Jet chamber pressures and tunnel flow conditions were chosen to approximate early Apollo wind tunnel test conditions. Maximum heating augmentation values measured for the Apollo-like configuration (>10 for forward facing roll jet and 4 for yaw jet) using temperature sensitive paint were shown to be similar to earlier experimental results (Jones and Hunt, 1965) using a phase change paint technique, but were acquired with much higher surface resolution. Heating results for the windward yaw jet on the Orion configuration had similar augmentation levels, but affected much less surface area. Numerical modeling for the Apollo-like yaw jet configuration with laminar flow and uniform jet outflow conditions showed similar heating patterns, qualitatively, but also showed significant variation with jet exit divergence angle, with as much as 25 percent variation in heat flux intensity for a 10 degree divergence angle versus parallel outflow. These results along with the fabrication methods and advanced measurement techniques developed will be used in the next phase of testing and evaluation for the updated Orion RCS configuration.

Buck, Gregory M.↗
NASA NTRS1986

Surface drilling technologies for Mars

We propose rock drilling and coring conceptual designs for the surface activities associated with a manned Mars mission. Straightforward extensions of equipment and procedures used on Earth are envisioned for the sample coring and shallow high explosive shot holes needed for tunneling and seismic surveying. A novel rocket exhaust jet piercing method is proposed for very rapid drilling of shot holes required for explosive excavation of emergency radiation shelters. Summaries of estimated equipment masses and power requirements are provided, and the indicated rotary coring rigs are scaled from terrestrial equipment and use compressed C02 from the Martian atmosphere for core bit cooling and cuttings removal. A mass of 120 kg and power of 3 kW(e) are estimated for a 10 m depth capability. A 100 m depth capacity core rig requires about 1150 kg and 32 kw(e). The rocket exhaust Jet equipment devised for shallow (3m) explosive emplacement shot holes requires no surface power beyond an electrical ignition system, and might have a 15 kg mass.

J D Blacic↗
NASA NTRS2023

Risks of Synchronized Low Yields Are Underestimated in Climate and Crop Model Projections

Simultaneous harvest failures across major crop-producing regions are a threat to global food security. Concurrent weather extremes driven by a strongly meandering jet stream could trigger such events, but so far this has not been quantified. Specifically, the ability of state-of-the art crop and climate models to adequately reproduce such high impact events is a crucial component for estimating risks to global food security. Here we find an increased likelihood of concurrent low yields during summers featuring meandering jets in observations and models. While climate models accurately simulate atmospheric patterns, associated surface weather anomalies and negative effects on crop responses are mostly underestimated in bias-adjusted simulations. Given the identified model biases, future assessments of regional and concurrent crop losses from meandering jet states remain highly uncertain. Our results suggest that model-blind spots for such high-impact but deeply-uncertain hazards have to be anticipated and accounted for in meaningful climate risk assessments.

Atmospheric dynamics↗
NASA NTRS1985

Some exactly solvable models of thick disk and radio jets near the black hole

The exact solution of the relativistic Euler's equation in the black hole geometry is obtained by identifying surfaces of constant angular momentum with the surfaces of constant angular velocity for the azimuthal component. It is shown that the solution gives rise to thick disks and cosmic jets for suitable choices of the physical parameters.

Chakrabarti, S. J.↗
NASA NTRS1975

Dynamic oxidation behavior of TD-NiCr alloy with different surface pretreatments

Oxidation tests of TD-NiCr alloy with different surface pretreatments were conducted in a Mach-5 arc-jet at 1200 C and 0.002 lb/sec flowing air environment. The mechanisms responsible for the observed oxidation behavior are examined. The presence of atomic oxygen in the air stream plays a significant role in determining the oxidation characteristic of the alloy. The rate of Cr2O3 vaporization by formation of volatile CrO3 is greatly enhanced by the flowing conditions. The typical microstructure of oxides formed in the dynamic tests consists of an external layer of NiO with a porous mushroom-type morphology, an intermediate layer of NiO and Cr2O3 oxide mixture, and a continuous inner layer of Cr2O3 in contact with the Cr-depleted alloy substrate. Three basic processes underlying the formation of mushroom-type NiO are identified and discussed. The oxidation rate is determined by the rate of vaporization of NiO. Surface pretreatment has a significant effect on the oxidation behavior of the alloy in the early stage of oxidation, but becomes less important as exposure time increases. Mechanical polishing induces surface recrystallization, but promotes the concurrence of external growth of NiO and internal oxidation of the alloy in the dynamic atmosphere.

Young, C. T.↗
NASA NTRS1995

Observations of Radar Backscatter at Ku and C Bands in the Presence of Large Waves during the Surface Wave Dynamics Experiment

Ocean radar backscatter in the presence of large waves is investigated using data acquired with the Jet Propulsion Laboratory NUSCAT radar at Ku band for horizontal and vertical polarizations and the University of Massachusetts CSCAT radar at C band for vertical polarization during the Surface Wave Dynamics Experiment. Off-nadir backscatter data of ocean surfaces were obtained in the presence of large waves with significant wave height up to 5.6 m. In moderate-wind cases, effects of large waves are not detectable within the measurement uncertainty and no noticeable correlation between backscatter coefficients and wave height is found. Under high-wave light-wind conditions, backscatter is enhanced significantly at large incidence angles with a weaker effect at small incidence angles. Backscatter coefficients in the wind speed range under consideration are compared with SASS-2 (Ku band), CMOD3-H1 (C band), and Plant's model results which confirm the experimental observations. Variations of the friction velocity, which can give rise to the observed backscatter behaviors in the presence of large waves, are presented.

Nghiem, S. V.↗
NASA NTRS1985

Surface photometry of comet P/Encke

A scheme to clean cometary digital images from offending background-star trails, and this technique has been applied to a pair of deep Kitt Peak 4-m plates of comet P/Encke, taken in October 1980. Simultaneous and subsequent digital spectra have been obtained at Lick Observatory. The non-polluted coma images show a strong asymmetric sunward-oriented fan/jet, and an extended and rounder (mostly gaseous) main coma, out to approximately 100,000 km radius. The stellar-trail point-spread function has a narrow width (sigma approximately 0.6 arcsec), so that spatial resolution better than approximately 300 km is achieved at the comet. The photometric gradient near the nucleus is very steep, strongly suggesting an icy-grain component which evaporates quickly (at radii equal to or less than 500 km) in the sunlight. Further from the nucleus, the profile becomes shallower, bluer, and more gas dominated. The effect of solar radiation pressure on C2, CN, and other molecules is probably responsible for the rounding of the outer, fainter isophotes. The source of the molecules is likely to be larger than the nucleus itself, and a substantial fraction may originate in the jet. The technique described here may also be applicable in surface photometry of galaxies, in cases where the heavy image pollution by foreground stars is present.

Djorgovski, S.↗
NASA NTRS2002

Molten-Metal Droplet Deposition on a Moving Substrate in Microgravity: Aiding the Development of Novel Technologies for Microelectronic Assembly

Driven by advancements in microelectronics manufacturing, this research investigates the oblique (non-axisymmetric) impact of liquid-metal droplets on flat substrates. The problem of interest is relevant to the development of the novel technology of on-demand dispension (printing) of microscopic solder deposits for the surface mounting of microelectronic devices. The technology, known as solder jetting, features on-demand deposition of miniature solder droplets (30 to 120 microns in diameter) in very fine, very accurate patterns using techniques analogous to those developed for the ink-jet printing industry. Despite its promise, severe limitations exist currently with regards to the throughput rates of the technology; some of these limitations are largely due to the lack of the capability for reliable prediction of solder bump positioning and shapes, especially under ballistic deposition conditions where the droplet impact phenomena are inherently three-dimensional. The study consists of a theoretical and an experimental component. The theoretical work uses a finite element formulation to simulate numerically the non-axisymmetric (3-D) fluid mechanics and heat transfer phenomena of a liquid solder droplet impacting at an angle alpha on a flat substrate. The work focuses on the pre-solidification regime. The modeling of the most challenging fluid mechanics part of the process has been completed successfully. It is based upon the full laminar Navier-Stokes equations employing a Lagrangian frame of reference. Due to the large droplet deformation, the surface (skin) as well as the volumetric mesh have to be regenerated during the calculations in order to maintain the high accuracy of the numerical scheme. The pressure and velocity fields are then interpolated on the newly created mesh. The numerical predictions are being tested against experiments, for cases where wetting phenomena are not important. For the impact parameters used in the example shown (We = 2.38, Fr = 16300, Re = 157), the droplet rolls along the substrate, but its shape remains practically axisymmetric for all impact angles within the range from 0 to 60 deg. Interestingly, the substrate/droplet contact area during the recoiling phase of the impact is not a monotonically decreasing function of time. The experimental component of the research tests the numerical predictions and provides necessary input data (contact angles) for the theoretical model. The experiments are performed in microgravity (2.2s drop tower of the NASA GRC) in order to allow for the use of mm-size solder droplets, which make feasible the performance of accurate measurements, while maintaining similitude of the relevant fluid dynamic groups (Re, Fr, We, Ste). Preliminary oblique impact experiments have been performed using water droplets in normal gravity.

Megaridis, C. M.↗
NASA NTRS1997

The Interplay of Surface Mount Solder Joint Quality and Reliability of Low Volume SMAs

Spacecraft electronics including those used at the Jet Propulsion Laboratory (JPL), demand production of highly reliable assemblies. JPL has recently completed an extensive study, funded by NASA's code Q, of the interplay between manufacturing defects and reliability of ball grid array (BGA) and surface mount electronic components.

Spacecraft electronics electronic assemblies J-lea↗
NASA NTRS2009

Numerical Analysis of Film Cooling at High Blowing Ratio

Computational Fluid Dynamics is used in the analysis of a film cooling jet in crossflow. Predictions of film effectiveness are compared with experimental results for a circular jet at blowing ratios ranging from 0.5 to 2.0. Film effectiveness is a surface quantity which alone is insufficient in understanding the source and finding a remedy for shortcomings of the numerical model. Therefore, in addition, comparisons are made to flow field measurements of temperature along the jet centerline. These comparisons show that the CFD model is accurately predicting the extent and trajectory of the film cooling jet; however, there is a lack of agreement in the near-wall region downstream of the film hole. The effects of main stream turbulence conditions, boundary layer thickness, turbulence modeling, and numerical artificial dissipation are evaluated and found to have an insufficient impact in the wake region of separated films (i.e. cannot account for the discrepancy between measured and predicted centerline fluid temperatures). Analyses of low and moderate blowing ratio cases are carried out and results are in good agreement with data.

El-Gabry, Lamyaa↗
NASA NTRS1975

Installation and airspeed effects on jet shock-associated noise

Experimental acoustic data are presented to illustrate, at model scale, the effect of varying the nozzle-wing installation on shock-associated noise, statically and with airspeed. The variation in installations included nozzle only, nozzle under-the-wing (with and without flaps deflected), and nozzle over-the-wing (unattached flow). The nozzles used were a conical and a 6-tube mixer nozzle with a cold-flow nozzle pressure ratio of 2.1. A 33-cm diameter free jet was used to simulate airspeed. With the nozzle only, shock wave noise dominated the spectra in the forward quadrant, while jet mixing noise dominated in the rearward quadrant. Similar trends were observed when a wing (flaps retracted) was included. Shock noise was attenuated with an over-the-wing configuration and increased with an under-the-wing configuration (due to reflection from the wing surface). With increasing flap deflection (under-the-wing configuration), the jet-flap interaction noise exceeded the shock noise and became dominant in both quadrants. The free jet results showed that airspeed had no effect on shock noise. The free jet noise data were corrected for convective amplification to approximate flight and comparisons between the various configurations are made.

Vonglahn, U.↗
NASA NTRS1975

Installation and airspeed effects on jet shock-associated noise

Experimental acoustic data are presented to illustrate, at model scale, the effect of varying the nozzle-wing installation on shock-associated noise, statically and with airspeed. The variation in installations included nozzle only, nozzle under-the-wing, and nozzle over-the-wing. With the nozzle only, shock wave noise dominated the spectra in the forward quadrant, while jet mixing noise dominated in the rearward quadrant. Similar trends were observed when a wing (flaps retracted) was included. Shock noise was attenuated with an over-the-wing configuration and increased with an under-the-wing configuration (due to reflection from the wing surface). With increasing flap deflection (under-the-wing configuration), the jet-flap interaction noise exceeded the shock noise and became dominant in both quadrants. The free jet results showed that airspeed had no effect on shock noise.

Von Glahn, U.↗