1,698 research outputs found
Personnel Launch System (PLS) study
NASA is currently studying a personnel launch system (PLS) approach to help satisfy the crew rotation requirements for the Space Station Freedom. Several concepts from low L/D capsules to lifting body vehicles are being examined in a series of studies as a potential augmentation to the Space Shuttle launch system. Rockwell International Corporation, under contract to NASA, analyzed a lifting body concept to determine whether the lifting body class of vehicles is appropriate for the PLS function. The results of the study are given
Advanced Manned Launch System (AMLS) study
To assure national leadership in space operations and exploration in the future, NASA must be able to provide cost effective and operationally efficient space transportation. Several NASA studies and the joint NASA/DoD Space Transportation Architecture Studies (STAS) have shown the need for a multi-vehicle space transportation system with designs driven by enhanced operations and low costs. NASA is currently studying an advanced manned launch system (AMLS) approach to transport crew and cargo to the Space Station Freedom. Several single and multiple stage systems from air-breathing to all-rocket concepts are being examined in a series of studies potential replacements for the Space Shuttle launch system in the 2000-2010 time frame. Rockwell International Corporation, under contract to the NASA Langley Research Center, has analyzed a two-stage all-rocket concept to determine whether this class of vehicles is appropriate for the AMLS function. The results of the pre-phase A study are discussed
Eco-efficiency
none4openMassari, Stefania; Miglietta, Pier Paolo; De Leo, Federica; Ruberti, MarcelloMassari, Stefania; Miglietta, Pier Paolo; De Leo, Federica; Ruberti, Marcell
What is in a pebble shape?
We propose to characterize the shapes of flat pebbles in terms of the
statistical distribution of curvatures measured along the pebble contour. This
is demonstrated for the erosion of clay pebbles in a controlled laboratory
apparatus. Photographs at various stages of erosion are analyzed, and compared
with two models. We find that the curvature distribution complements the usual
measurement of aspect ratio, and connects naturally to erosion processes that
are typically faster at protruding regions of high curvature.Comment: Phys. Rev. Lett. (to appear
The shape and erosion of pebbles
The shapes of flat pebbles may be characterized in terms of the statistical
distribution of curvatures measured along their contours. We illustrate this
new method for clay pebbles eroded in a controlled laboratory apparatus, and
also for naturally-occurring rip-up clasts formed and eroded in the Mont
St.-Michel bay. We find that the curvature distribution allows finer
discrimination than traditional measures of aspect ratios. Furthermore, it
connects to the microscopic action of erosion processes that are typically
faster at protruding regions of high curvature. We discuss in detail how the
curvature may be reliable deduced from digital photographs.Comment: 10 pages, 11 figure
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