Results for “range prediction” — Page 51

NASA NTRS2018

Uninstalled Performance Predictions of a Magnesium-Fueled Ramjet Cycle in Carbon Dioxide Atmospheres

Evaluation of alternative propulsion cycles for planetary space exploration applications is motivated by ongoing emphasis of robotic science and human exploration missions and concepts. Atmosphere-breathing propulsion systems operating on their own or in a combined cycle with other engines offer the potential to increase overall propulsion efficiency and reduce the amount of propellant that must be carried on board the vehicle. The purpose of this paper is to evaluate the idealized uninstalled performance characteristics of metal-fueled ramjet systems operating in carbon dioxide atmospheres. Physics-based predictions are presented for critical and a range of supercritical conditions of the propulsion cycle.

Axdahl, Erik L.↗

NASA NTRSDate not supplied

Impact of GPM-retrieved surface meteorology condition on simulations of two winter storms during ICE-POP 2018

Led by the KMA as a component of the WMO's World Weather Research Program (WWRP) Research and Development and Forecast Demonstration Projects (RDP/FDP). Taken place during the Winter Olympics (February-March) of 2018. Goals of ICE-POP: To improve understanding on severe weathers (snowfalls, visibility, rapid wind changes and gusts,) over complex terrain; To improve the predictability of nowcasting and very-short range forecasting with a few kilometer horizontal resolution - Development of NWP-based nowcasting, multi-scale data assimilation and time-lagged ensemble for VSRF, and radar reflectivity and visibility data assimilation; To improve verification for high resolution model considering complex terrain.

Xuanli Li↗

NASA NTRS2021

NASA Engineering and Safety Center Technical Bulletin No. 21-01: Experimental and Computational Study of Cavitation in Hydrogen Peroxide

Cavitation in liquid propulsion systems can lead to performance degradation and hardware failures. The NESC sponsored an investigation to measure and model cavitation in pressurized hydrogen peroxide fl ow. The experimentally measured and computationally predicted cavitation lengths were compared as a function of cavitation number. The measured and predicted data exhibited close agreement over the range of pressures and temperatures studied, and no calibration of the cavitation model coefficients was needed.

NESC Technical Bulletin No. 21-01↗

NASA NTRS2022

Low-Speed Performance Enhancement using Localized Active Flow Control: Integration Study of Localized Active Flow Control on a Performance Reference Aircraft (3/4)

A study of conceptual integration and performance aspects of localized active flow control (AFC) technology onto wings of short-to-medium-range project passenger airplanes is summarized. Using predicted aerodynamic performance improvement opportunities on the CFD Reference Aircraft, estimated benefit opportunities for conceptual implementation of studied wing localized active flow control (AFC) technology for low-speed (take-off and landing) application on a Performance Reference Aircraft configuration are presented. Using conceptual AFC systems and structural integration weight penalties for studied concepts, potential relevant net performance benefits can be obtained with reliable AFC in takeoff and landing. The conceptual integration study identifies potential promising localized wing AFC application opportunities for high-lift conditions using energy sources for modern aircraft. Material benefits are estimated for take-off and landing configurations for selected localized AFC applications. Next steps to refine and expand results of investigated topics, as well as possible other local AFC wing applications, are suggested.

AFC↗

NASA NTRSDate not supplied

Conceptual Integration Studies of Localized Active Flow Control on the Wing of a Commercial Aircraft

A study of conceptual integration and performance of localized active flow control technology onto wings of short-to-medium-range project passenger airplanes is summarized. Using predicted aerodynamic performance improvement opportunities on a computational fluid dynamics reference aircraft, this paper presents the estimated performance opportunities for conceptual implementation of studied wing localized active flow control technology for low-speed (takeoff and landing) application on a Project Research Aircraft configuration. Using conceptual active flow control systems and structural integration weight penalties for studied concepts, potential relevant net performance benefits can be obtained with reliable active flow control in takeoff and landing. The conceptual integration study identifies potential localized wing active flow control application opportunities for high-lift conditions using energy sources available on modern aircraft. Material benefits are estimated for takeoff and landing configurations for selected localized wing active flow control applications. The study concluded that substantial low-speed Maximum Lift and Lift/Drag related performance improvements may be possible with localized wing high-lift active flow control systems powered by auxiliary power unit, engine bleed, or electrical compressors - with due consideration of integration and weight impacts as well as availability requirements of such systems.

drag reduction↗

NASA NTRSDate not supplied

Numerical Simulation of No-Vent Chill and Fill of a Large Liquid Hydrogen Tank

To enable the design of future in-space cryogenic propellant transfer vehicles, high accuracy models of the cryogenic propellant transfer process are desired. For in-space refueling applications, accurate simulations are desired of the propellant tank chilldown and no-vent fill (NVF) process in order to estimate the amount of propellant required, to determine the maximum sustainable flow rate to fill the tank, and to establish a timeline for the filling process. NVF is a complex process that involves numerous two-phase heat and mass transfer phenomena, such as boiling at the wall and evaporation and condensation at the liquid/vapor interface. In recent years, progress has been made in developing a numerical modeling technique using the Generalized Fluid System Simulation Program (GFSSP) that has been validated against several small-scale liquid nitrogen NVF tests. This paper presents GFSSP numerical model validation against three liquid hydrogen NVF tests on a large-scale propellant tank. Comparing the GFSSP model to the data for pressure, fill level, and wall temperature, the mean absolute percentage error is below 20% across the range of simulated conditions, indicating very good predictive agreement for this large-scale hydrogen NVF test series.

Alok Majumdar↗

NASA NTRSDate not supplied

Numerical Simulation of No-Vent Chill and Fill of a Large Liquid Hydrogen Tank

To enable the design of future in-space cryogenic propellant transfer vehicles, high accuracy models of the cryogenic propellant transfer process are desired. For in-space refueling applications, accurate simulations are desired of the propellant tank chilldown and no-vent fill (NVF) process in order to estimate the amount of propellant required, to determine the maximum sustainable flow rate to fill the tank, and to establish a timeline for the filling process. NVF is a complex process that involves numerous two-phase heat and mass transfer phenomena, such as boiling at the wall and evaporation and condensation at the liquid/vapor interface. In recent years, progress has been made in developing a numerical modeling technique using the Generalized Fluid System Simulation Program (GFSSP) that has been validated against several small-scale liquid nitrogen NVF tests. This paper presents GFSSP numerical model validation against three liquid hydrogen NVF tests on a large-scale propellant tank. Comparing the GFSSP model to the data for pressure, fill level, and wall temperature, the mean absolute percentage error is below 20% across the range of simulated conditions, indicating very good predictive agreement for this large-scale hydrogen NVF test series.

Alok Majumdar↗

NASA NTRS1984

Experimental and analytical investigation of a freezing point depressant fluid ice protection system

A glycol-exuding porous leading edge ice protection system was tested in the NASA Icing Research Tunnel. Stainless steel mesh, laser drilled titanium, and composite panels were tested on two general aviation wing sections. Two different glycol-water solutions were evaluated. Minimum glycol flow rates required for anti-icing were obtained as a function of angle of attack, liquid water content, volume median drop diameter, temperature, and velocity. Ice accretions formed after five minutes of icing were shed in three minutes or less using a glycol fluid flow equal to the anti-ice flow rate. Two methods of predicting anti-ice flow rates are presented and compared with a large experimental data base of anti-ice flow rates over a wide range of icing conditions. The first method presented in the ADS-4 document typically predicts flow rates lower than the experimental flow rates. The second method, originally published in 1983, typically predicts flow rates up to 25 percent higher than the experimental flow rates. This method proved to be more consistent between wing-panel configurations. Significant correlation coefficients between the predicted flow rates and the experimental flow rates ranged from .867 to .947.

Albright, A. E.↗

NASA NTRS1985

Thermal traction contact performance evaluation under fully flooded and starved conditions

Ultra high speed traction tests were performed on two traction fluids commonly employed. Traction data on these fluids is required for purposes of traction drive design optimization techniques. To obtain the traction data, an existing twin disc traction test machine was employed. This machine was modified to accommodate the range of test variables. All the data reported was obtained under conditions of side slip, a technique whereby only low power levels are required to simulate real traction drive contacts. Theoretical traction predictions were performed for a representative number of curves that showed the influence of rolling velocity, of contact pressure and of aspect ratio. To establish the accuracy of the thermal model the predictions were performed ith increasing levels of independence of experimentally determined parameters. In the final resulting prediction only two non linear thermal parameters were used for the prediction of 15 different traction curves covering the entire range of variables as used in the investigation, with the exception of the influence of asperity traction. Comparison of these theoretical curves and corresponding experimental traces show very good agreement.

Tevaarwerk, J. L.↗

NASA NTRS2008

If We Can't Predict Solar Cycle 24, What About Solar Cycle 34?

Predictions of solar activity in Solar Cycle 24 range from 50% larger than SC 23 to the onset of a Grand Minimum. Because low levels of solar activity are associated with global cooling in paleoclimate and isotopic records, anticipating these extremes is required in any longterm extrapolation of climate variability. Climate models often look forward 100 or more years, which would mean 10 solar cycles into the future. Predictions of solar activity are derived from a number of methods, most of which, such as climatology and physics-based models, will be familiar to atmospheric scientists. More than 50 predictions of the maximum amplitude of SC 24 published before solar minimum will be discussed. Descriptions of several methods that result in the extreme predictions and some anticipation of even longer term predictions will be presented.

Pesnell. William Dean↗

NASA NTRS1972

The 136 MHZ/400 MHz earth station antenna-noise temperature prediction program for RAE-B

A simulation study was undertaken to determine the 136 MHz and 400 MHz noise temperature of the ground network antennas which will track the RAE-B satellite during data transmission periods. Since the noise temperature of the antenna effectively sets the signal-to-noise ratio of the received signal, a knowledge of SNR will be helpful in locating the optimum time windows for data transmission during low noise periods. Antenna noise temperatures will be predicted for selected earth-based ground stations which will support RAE-B. Telemetry data acquisition will be at 400 MHz; tracking support at 136 MHz will be provided by the Goddard Range and Range Rate (RARR) stations. The antenna-noise temperature predictions will include the effects of galactic-brightness temperature, the sun, and the brightest radio stars. Predictions will cover the ten-month period from March 1, 1973 to December 31, 1973.

Taylor, R. E.↗

NASA NTRS2011

Computational Analysis of a Low-Boom Supersonic Inlet

A low-boom supersonic inlet was designed for use on a conceptual small supersonic aircraft that would cruise with an over-wing Mach number of 1.7. The inlet was designed to minimize external overpressures, and used a novel bypass duct to divert the highest shock losses around the engine. The Wind-US CFD code was used to predict the effects of capture ratio, struts, bypass design, and angles of attack on inlet performance. The inlet was tested in the 8-ft by 6-ft Supersonic Wind Tunnel at NASA Glenn Research Center. Test results showed that the inlet had excellent performance, with capture ratios near one, a peak core total pressure recovery of 96 percent, and a stable operating range much larger than that of an engine. Predictions generally compared very well with the experimental data, and were used to help interpret some of the experimental results.

Chima, Rodrick V.↗

NASA NTRS1972

Application of the leading edge suction analogy to prediction of longitudinal load distribution and pitching moments for sharp edged delta wings

The leading-edge-suction analogy of Polhamus has been used to develop the longitudinal load distribution of the vortex lift for delta wings. This distribution is shown to be similar in shape to that of the potential-flow longitudinal loading for delta wings having aspect ratios of 2 or less. The totals of the two theoretical distributions for delta wings with an aspect ratio near 1 are in good agreement with the experimentally determined loadings over the angle-of-attack range from 0 to 30 deg. The corresponding predicted pitching moments show slightly more stability than those measured, because of loss of lift near the wing tips.

Snyder, M. H., Jr.↗

NASA NTRSDate not supplied

Backshell Radiation Measurements in the EAST Facility for Titan Entry

A new test series was performed in the Electric Arc Shock Tube (EAST) facility, with the aim of reproducing conditions which will be encountered in the backshell of the Dragonfly spacecraft. Measurements of shock-layer radiation from CN Violet, CN Red and C 2 Swan bands are made in mixtures of 2.2% CH 4 in N 2 (by mole) heated by incident shock waves spanning from 3 to 7 km/s. This study focuses on the spectrally and spatially resolved measurement of absolute radiance made with four optical emission spectrometers spanning 220-1400 nm. Comparison with CFD simulations and equilibrium conditions were made. The predicted radiation was found to be between -40% to 100% from the measurements for the nonequilibrium peak radiance, increasing with velocity. At 7 cm/150 μs from the shock front, the discrepancies appear to be larger, ranging from -50 to 200%. Comparison between measured and predicted temperatures and number densities of CN indicate shortcomings in the non-Boltzmann model of CN.

Augustin Tibere-Inglesse↗

NASA NTRSDate not supplied

Backshell Radiation Measurements in the EAST Facility for Titan Entry

A new test series was performed in the Electric Arc Shock Tube (EAST) facility, with the aim of reproducing conditions which will be encountered in the backshell of the Dragonfly spacecraft. Measurements of shock-layer radiation from CN Violet, CN Red and C 2 Swan bands are made in mixtures of 2.2% CH 4 in N 2 (by mole) heated by incident shock waves spanning from 3 to 7 km/s. This study focuses on the spectrally and spatially resolved measurement of absolute radiance made with four optical emission spectrometers spanning 220-1400 nm. Comparison with CFD simulations and equilibrium conditions were made. The predicted radiation was found to be between -40% to 100% from the measurements for the nonequilibrium peak radiance, increasing with velocity. At 7 cm/150 μs from the shock front, the discrepancies appear to be larger, ranging from -50 to 200%. Comparison between measured and predicted temperatures and number densities of CN indicate shortcomings in the non-Boltzmann model of CN.

Augustin Tibere-Inglesse↗

NASA NTRS1972

The present thermal state of the terrestrial planets

The thermal state of bodies is discussed as an aspect of their internal dynamics for bodies of roughly meteoritic composition in the range of sizes of planetary objects. The rheological behaviour of planetary material is assumed to be represented by a Newtonian viscosity varying exponentially with temperature, and only the consistency of this assumption with the elastic view of the planets is considered. It is shown that for the whole range of physically plausible values of the material parameters, the temperature distribution associated with a solution to the problem of internal dynamics for bodies with external radii larger than about 800 km departs significantly from that predicted on conduction theory arguments. For bodies in the range of sizes of the terrestrial planets, the viscosity-temperature relationship plays a dominant role in setting the absolute temperature of the central regions.

Tozer, D. C.↗

NASA NTRS1984

Dynamic flow quality measurements in the Langley Low Turbulence Pressure Tunnel

The results of tests to measure the disturbance levels across the cooler, screens, and nozzle in the test section of the rehabilitated Langley Research Center Low Turbulence Pressure Tunnel are reported and discussed. The velocity fluctuations measured upstream and downstream of the cooler were approximately equal and ranged from 5 to 15 percent. The attenuation of the measured velocity fluctuations across the screen agreed with predictions from Dryden's (1949) theory. Velocity fluctuations in the test section ranged from 0.025 percent at Mach 0.05 to 0.3 percent at Mach 0.2. Pressure fluctuations at the test section walls agreed with previous measurements made under a turbulent boundary. The autocorrelation functions indicated that there were large reductions in the integral scale of turbulence across the cooler and screens. The spectra measured upstream and downstream of the cooler were mostly broadband.

Stainback, P. C.↗

NASA NTRS1994

Computational prediction of isolated performance of an axisymmetric nozzle at Mach number 0.90

An improved ability to predict external propulsive performance was incorporated into the three-dimensional Navier-Stokes code PAB3D. The improvements are the ability to account for skin friction and external pressure forces. Performance parameters for two axisymmetric supersonic cruise nozzle configurations were calculated to test the improved methodology. Internal and external flow-field regions were computed using a two-equation kappa-epsilon turbulent viscous-stress model. The computed thrust-minus-drag ratios were within 1 percent of the absolute level of experimental data and the trends of data were predicted accurately. The predicted trend of integrated nozzle pressure drag matched the trend of the integrated experimental pressure drag over a range of nozzle pressure ratios, but absolute drag levels were not accurately predicted.

Carlson, John R.↗