6,023 research outputs found
Satellite remote sensing for ice sheet research
Potential research applications of satellite data over the terrestrial ice sheets of Greenland and Antarctica are assessed and actions required to ensure acquisition of relevant data and appropriate processing to a form suitable for research purposes are recommended. Relevant data include high-resolution visible and SAR imagery, infrared, passive-microwave and scatterometer measurements, and surface topography information from laser and radar altimeters
Experimental and computational characterization of a modified GEC cell for dusty plasma experiments
A self-consistent fluid model developed for simulations of micro- gravity
dusty plasma experiments has for the first time been used to model asymmetric
dusty plasma experiments in a modified GEC reference cell with gravity. The
numerical results are directly compared with experimental data and the
experimentally determined dependence of global discharge parameters on the
applied driving potential and neutral gas pressure is found to be well matched
by the model. The local profiles important for dust particle transport are
studied and compared with experimentally determined profiles. The radial forces
in the midplane are presented for the different discharge settings. The
differences between the results obtained in the modified GEC cell and the
results first reported for the original GEC reference cell are pointed out
Cyclical Tests of Selected Space Shuttle TPS Metallic Materials in a Plasma Arc Tunnel. Volume 2: Appendices - Data Tabulation
Calibration data are presented for heat flux and pressure profiles, model temperature histories, and model weight and thickness changes
Cyclical tests of selected space shuttle TPS metallic materials in a plasma arc tunnel Volume 1: Description of tests and program summary
Work, concerned with cyclical thermal evaluation of selected space shuttle thermal protection system (TPS) metallic materials in a hypervelocity oxidizing atmosphere that approximated an actual entry environment, is presented. A total of 325 sample test hours were conducted on 21 super-alloy metallic samples at temperatures from 1800 to 2200 F (1256 to 1478 K) without any failures. The 4 x 4 in. (10.2 x 10.2 cm) samples were fabricated from five nickel base alloys and one cobalt base alloy. Eighteen of the samples were cycled 100 times each and the other three samples 50 times each in a test stream emanating from an 8 in. (20.3 cm) diam exit, Mach 4.6, conical nozzle. The test cycle consisted of a 10 min heat pulse to a controlled temperature followed by a 10 min cooldown period. The TD-NiCrAl and TD-NiAlY materials showed the least change in weight, thickness, and physical appearance even though they were subjected to the highest temperature environment
Methodology for urban rail and construction technology research and development planning
A series of transit system visits, organized by the American Public Transit Association (APTA), was conducted in which the system operators identified the most pressing development needs. These varied by property and were reformulated into a series of potential projects. To assist in the evaluation, a data base useful for estimating the present capital and operating costs of various transit system elements was generated from published data. An evaluation model was developed which considered the rate of deployment of the research and development project, potential benefits, development time and cost. An outline of an evaluation methodology that considered benefits other than capital and operating cost savings was also presented. During the course of the study, five candidate projects were selected for detailed investigation; (1) air comfort systems; (2) solid state auxiliary power conditioners; (3) door systems; (4) escalators; and (5) fare collection systems. Application of the evaluation model to these five examples showed the usefulness of modeling deployment rates and indicated a need to increase the scope of the model to quantitatively consider reliability impacts
A Long Duration Orbital Simulator (LDOS) Utilized in Technical Planning Activities
This paper describes the development and use of a long duration orbital simulator (LDOS). The LDOS capabilities, options, accuracy, and central processing unit (CPU) usage are discussed. The applications described using the LDOS are associated with (a) Manned Space Flight Network (MSFN) support of long duration missions, (b) environmental effects on high earth orbits and (c) long term orbit decay. The appendix depicts the salient portions of the math model
How to make large, void free dust clusters in dusty plasma under microgravity
Collections of micrometer sized solid particles immersed in plamsa are used
to mimic many systems from solid state and fluid physics, due to their strong
electrostatic interaction, their large inertia, and the fact that they are
large enough to be visualized with ordinary optics. On Earth, gravity restricts
the so called dusty plasma systems to thin, two-dimensional layers, unless
special experimental geometries are used, involving heated or cooled electrons,
and/or the use of dielectric materials.In micro-gravity experiments, the
formation of a dust-free void breaks the isotropy of three-dimensional dusty
plasma systems. In order to do real three-dimensional experiments, this void
has somehow to be closed. In this paper, we use a fully self-consistent fluid
model to study the closure of a void in a micro-gravity experiment, by lowering
the driving potential. The analysis goes beyond the simple description of the
virtual void, which describes the formation of a void without taking the dust
into account. We show that self-organization plays an important role in void
formation and void closure, which also allows a reversed scheme, where a
discharge is run at low driving potentials and small batches of dust are added.
No hysteresis is found this way. Finally, we compare our results to recent
experiments and find good agreement,but only when we do not take
charge-exchange collisions into account
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