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.

Melt processing of SWCNT-polyimide nanocomposite fibers

Abstract: Melt processing of SWCNT/Ultem nanocomposite fibers was demonstrated for fibers containing up to 1 wt% SWCNTs. High-resolution electron microscopy and Raman spectroscopy were used to evaluate the quality of SWCNT dispersion. SWCNT alignment in the fiber direction was induced by shear forces present during the melt extrusion and fiber drawing processes. This alignment resulted in significantly higher tensile moduli and yield stress in SWCNT/Ultem nanocomposite fibers relative to unoriented nanocomposite films having the same SWCNT concentration.

Comparison of Tm:ZBLAN and Tm:Silica fiber lasers; Spectroscopy and tunable pulsed laser operation around 1.9 μm

Abstract: Tm-doped ZBLAN and Tm-doped silica glass are compared spectroscopically and the fiber lasing of the Tm 3 F 4 →3 H 6 transition around 1.9 μm in ZBLAN and silica fibers is compared. The spectroscopy of these materials indicates that Tm:ZBLAN possesses advantages over Tm:silica glass due to the lower phonon energies. The phonon energy in these glass hosts influences both the pump manifold lifetime, the Tm 3 H 4, and the upper laser manifold lifetime, the Tm 3 F 4. The maximum phonon energy in Tm:ZBLAN, ∼500 cm-1 , compared to Tm:silica, ∼1100 cm-1, leads to better Tm–Tm self quenching towards populating the Tm 3 F 4, as well as better Tm 3 F 4→3 H 6 quantum efficiency. A spectroscopic analysis using the Judd–Ofelt theory and measured lifetimes are used to assess the merits of Tm:ZBLAN over Tm:silica as a fiber laser material. Diode-pumped fiber lasing experiments show that Tm:ZBLAN possesses advantages over Tm:silica that are believed to be due to a lower phonon energy. Data is presented for launched pump energy versus laser energy, fiber length versus slope efficiency, and output mirror reflectivity versus slope efficiency. Tm:ZBLAN is demonstrated to possess higher slope efficiencies and lower thresholds, than Tm:silicate. A grating tuned Tm:ZBLAN laser is also demonstrated for tunable operation between 1.893 μm and 1.955 μm.

Mars Science Laboratory Entry, Descent, and Landing System Overview

Abstract: In 2010, the Mars science laboratory (MSL) mission will pioneer the next generation of robotic entry, descent, and landing (EDL) systems by delivering the largest and most capable rover to date to the surface of Mars. In addition to landing more mass than prior missions to Mars, MSL will offer access to regions of Mars that have been previously unreachable. The MSL EDL sequence is a result of a more stringent requirement set than any of its predecessors. Notable among these requirements is landing a 900 kg rover in a landing ellipse much smaller than that of any previous Mars lander. In meeting these requirements, MSL is extending the limits of the EDL technologies qualified by the Mars viking, Mars pathfinder, and Mars exploration rover missions. Thus, there are many design challenges that must be solved for the mission to be successful. Several pieces of the EDL design are technological firsts, such as guided entry and precision landing on another planet, as well as the entire sky crane maneuver. This paper discusses the MSL EDL architecture and discusses some of the challenges faced in delivering an unprecedented rover payload to the surface of Mars.

Self-induced wing rock of slender delta wings

Abstract: As part of a research program aimed at exploring basic mechanisms that cause wing rock in combat aircraft, an investigation was conducted to study the aerodynamic factors which cause the low-speed wing rock exhibited by slender delta wings. A flat-plate delta wing with 80 deg leading-edge sweep was subjected to conventional static-force tests and dynamic wind-tunnel experiments which included forced-oscillation, rotary, and free-to-roll tests. In addition, visualization of the flow phenomena involved was obtained by observing tuft patterns and using a helium-bubble technique. This paper summarizes the results of this study. Fundamental information is presented on the aerodynamic mechanisms that cause the wing rock and the problem of mathematically modeling the aerodynamics and motions is discussed.