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Institution

Langley Research Center

FacilityHampton, Virginia, United States
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.


Papers
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Journal ArticleDOI
TL;DR: The 2006 European-U.S. Multidiscipli-nary Optimization (MDO) Colloquium in Goettingen, Germany, was attended by nearly seventy professionals from academia, industry, and government as discussed by the authors.
Abstract: This paper is a summary of topics presented and discussed at the 2006 European-U.S. Multidiscipli- nary Optimization (MDO) Colloquium in Goettingen, Germany, attended by nearly seventy professionals from academia, industry, and government. An attempt

139 citations

Journal ArticleDOI
TL;DR: In this paper, a weighted two-color relative intensity e uorescence theory for quantitatively determining surface temperatures on hypersonic wind-tunnel models and an improved application of the one-dimensional conduction theory for use in determining global heating mappings is described.
Abstract: Detailed aeroheating information is critical to the successful design of a thermal protection system (TPS) for an aerospace vehicle. NASA Langley Research Center’ s (LaRC) phosphor thermography method is described. Development of theory is provided for a new weighted two-color relative-intensity e uorescence theory for quantitatively determining surface temperatures on hypersonic wind-tunnel models and an improved application of the one-dimensional conduction theory for use in determining global heating mappings. The phosphor methodology at LaRC is presented including descriptions of phosphor model fabrication, test facilities, and phosphor video acquisition systems. A discussion of the calibration procedures, data reduction, and data analysis is given. Estimates of the total uncertainties (with a 95% cone dence level ) associated with the phosphor technique are shown to be approximately 7 ‐10% in LaRC’ s 31-Inch Mach 10 Tunnel and 8 ‐10% in the 20-Inch Mach 6 Tunnel. A comparison with thin-e lm measurements using 5.08-cm-radius hemispheres shows the phosphor data to be within 7% of thin-e lm measurements and to agree even better with predictions via a LATCH computational e uid dynamics (CFD) solution. Good agreement between phosphor data and LAURA CFD computations on the forebody of a vertical takeoff/vertical lander cone guration at four angles of attack is also shown. In addition, a comparison is givenbetween Mach 6phosphordata andlaminarandturbulentsolutionsgeneratedusing theLAURA,GASP, and LATCH CFD codes on the X-34 cone guration. The phosphor process outlined is believed to provide the aerothermodynamic community with a valuable capability for rapidly obtaining (three to four weeks ) detailed heating information needed in TPS design. Nomenclature A = area of camera array element, m 2 a = effective aperture factor of camera optics, sr b = vehicle wing span from wing tip to wing tip, m C = heat transfer coefe cient constant, h.iw=Tw/ c = specie c heat of model substrate, J/ (kg-K) D = driver constant, iaw.Tw=iw/iTinit F = e ux of light, W/m 2 h = heat transfer coefe cient, kg/ (m 2 -s) I = radiant intensity, W/ (m 2 -sr)

139 citations

Journal ArticleDOI
TL;DR: In this paper, a formulation for identification of linear multivariable systems from single or multiple sets of input-output data is presented, where the observer is expressed in terms of an observer, which is made asymptotically stable by an embedded eigenvalue assignment procedure.
Abstract: This paper presents a formulation for identification of linear multivariable systems from single or multiple sets of input-output data. The system input-output relationship is expressed in terms of an observer, which is made asymptotically stable by an embedded eigenvalue assignment procedure. The prescribed eigenvalues for the observer may be real, complex, mixed real and complex, or zero corresponding to a deadbeat observer. In this formulation, the Markov parameters of the observer are first identified from input-output data. The Markov parameters of the actual system are then recovered from those of the observer and used to realize a state space model of the system. The basic mathematical formulation is derived, and numerical examples are presented to illustrate the proposed method.

139 citations

Journal ArticleDOI
TL;DR: Martian surface materials viewed by the two Viking landers (VL-1 and VL-2) range from fine-grained nearly cohesionless soils to rocks.
Abstract: Martian surface materials viewed by the two Viking landers (VL-1 and VL-2) range from fine-grained nearly cohesionless soils to rocks. Footpad 2 of VL-1, which landed at 2.30 m/s, penetrated 16.5 cm into very fine grained dunelike drift material; footpad 3 rests on a rocky soil which it penetrated ≈3.6 cm. Further penetration by footpad 2 may have been arrested by a hard substrate. Penetration by footpad 3 is less than would be expected for a typical lunar regolith. During landing, retroengine exhausts eroded the surface and propelled grains and rocks which produced craters on impact with the surface. Trenches excavated in drift material by the sampler have steep walls with up to 6 cm of relief. Incipient failure of the walls and failures at the end of the trenches are compatible with a cohesion near 10–10^2 N/m^2. Trenching in rocky soil excavated clods and possibly rocks. In two of five samples, commanded sampler extensions were not achieved, a situation indicating that buried rocks or local areas with large cohesions (≥10 kN/m^2) or both are present. Footpad 2 of VL-2, which landed at a velocity between 1.95 and 2.34 m/s, is partly on a rock, and footpad 3 appears to have struck one; penetration and leg strokes are small. Retroengine exhausts produced more erosion than occurred for VL-1 owing to increased thrust levels just before touchdown. Deformations of the soil by sampler extensions range from doming of the surface without visible fracturing to doming accompanied by fracturing and the production of angular clods. Although rocks larger than 3.0 cm are abundant at VL-1 and VL-2, repeated attempts to collect rocks 0.2–1.2 cm across imbedded in soil indicate that rocks in this size range are scarce. There is no evidence that the surface sampler of VL-2, while it was pushing and nudging rocks ≈25 cm across, spalled, chipped, or fractured the rocks. Preliminary analyses of surface sampler motor currents (≈25 N force resolution) during normal sampling are consistent with cohesionless frictional soils (ϕ ≈ 36°) or weakly cohesive frictionless soils (C < 2 kN/m^2). The soil of Mars has both cohesion and friction.

139 citations

Journal ArticleDOI
TL;DR: In this article, a combination of in-situ PM2.5, sunphotometers, upward pointing lidar and satellite aerosol optical depth (AOD) instruments have been employed to better understand variability in the correlation between AOD and surface PM 2.5 at the surface.

139 citations


Authors

Showing all 16015 results

NameH-indexPapersCitations
Daniel J. Jacob16265676530
Donald R. Blake11872749697
Veerabhadran Ramanathan10030147561
Raja Parasuraman9140241455
Robert W. Platt8863831918
James M. Russell8769129383
Daniel J. Inman8391837920
Antony Jameson7947431518
Ya-Ping Sun7927728722
Patrick M. Crill7922820850
Richard B. Miles7875925239
Patrick Minnis7749023403
Robert W. Talbot7729719783
Raphael T. Haftka7677328111
Jack E. Dibb7534418399
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202335
202286
2021571
2020540
2019669
2018797