Langley Research Center

About: Langley Research Center is a facility organization based out in Hampton, Virginia, United States. It is known for research contribution in the topics: Mach number & Wind tunnel. The organization has 15945 authors who have published 37602 publications receiving 821623 citations. The organization is also known as: NASA Langley & NASA Langley Research Center.

Spectral reflectances of natural targets for use in remote sensing studies

Abstract: A collection of spectral reflectances of 156 natural targets is presented in a uniform format. For each target both a graphical plot and a digital tabulation of reflectance is given. The data were taken from the literature and include laboratory, field, and aircraft measurements. A discussion of the different measurements of reflectance is given, along with the changes in apparent reflectance when targets are viewed through the atmosphere. The salient features of the reflectance curves of common target types are presented and discussed.

Methodology for error analysis and simulation of lidar aerosol measurements

Abstract: A methodology is presented for objective and automated determination of the uncertainty in lidar aerosol measurements. This methodology is based on standard error-propagation procedures, a large data base on atmospheric behavior, and long experience in lidar data processing. Algebraic expressions for probable error are derived as a function of the relevant parameters. The validity of these expressions is then tested by making simulated measurements and analyses in which random errors of appropriate size are injected at proper steps of the measurement and analysis process. An illustrative example is given where the methodology is applied to a new lidar system now being used for airborne measurements of the stratospheric aerosol.

The 2010 California Research at the Nexus of Air Quality and Climate Change (CalNex) field study

Abstract: The California Research at the Nexus of Air Quality and Climate Change (CalNex) field study was conducted throughout California in May, June, and July of 2010. The study was organized to address issues simultaneously relevant to atmospheric pollution and climate change, including (1) emission inventory assessment, (2) atmospheric transport and dispersion, (3) atmospheric chemical processing, and (4) cloud-aerosol interactions and aerosol radiative effects. Measurements from networks of ground sites, a research ship, tall towers, balloon-borne ozonesondes, multiple aircraft, and satellites provided in situ and remotely sensed data on trace pollutant and greenhouse gas concentrations, aerosol chemical composition and microphysical properties, cloud microphysics, and meteorological parameters. This overview report provides operational information for the variety of sites, platforms, and measurements, their joint deployment strategy, and summarizes findings that have resulted from the collaborative analyses of the CalNex field study. Climate-relevant findings from CalNex include that leakage from natural gas infrastructure may account for the excess of observed methane over emission estimates in Los Angeles. Air-quality relevant findings include the following: mobile fleet VOC significantly declines, and NO_x emissions continue to have an impact on ozone in the Los Angeles basin; the relative contributions of diesel and gasoline emission to secondary organic aerosol are not fully understood; and nighttime NO_3 chemistry contributes significantly to secondary organic aerosol mass in the San Joaquin Valley. Findings simultaneously relevant to climate and air quality include the following: marine vessel emissions changes due to fuel sulfur and speed controls result in a net warming effect but have substantial positive impacts on local air quality.

Design of Three-Dimensional Hypersonic Inlets with Rectangular-to-Elliptical Shape Transition

Abstract: A methodology has been devised for the design of three-dimensional hypersonic Inlets, This methodology makes extensive use of inviscid stream-tracing techniques to generate an inlet with smooth shape transition from a rectangular-like capture to an elliptical throat. Highly swept leading edges and a significantly notched cowl enable use of these inlets in fixed geometry configurations. The design procedure includes a three-dimensional viscous correction and uses established correlations to check for boundary-layer separation caused by shock wave interactions. Complete details of the design procedure are presented and the characteristics of a modular inlet with a design point of Mach 6.0 are examined. Comparison with a classical two-dimensional inlet optimized for maximum total pressure recovery indicates that these three-dimensional inlets demonstrate good inviscid performance even when operating well below the design point. An estimate of the on-design viscous performance corresponds with that of an efficient inlet for scramjet applications.

High-dielectric-constant all-polymer percolative composites

Abstract: We report here an all-polymer high-dielectric (dielectric constant K>1000 at 1 kHz) percolative composite material, fabricated by a combination of conductive polyaniline particles (K>105) within a poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) terpolymer matrix (K>50). These high-K polymer hybrid materials also exhibit high electromechanical responses. For example, 1.5% strain, which is proportional to the square of the field applied, can be induced by a field of 9.5 MV/m, an eightfold reduction in field applied compared with that in a fluoroterpolymer matrix.