2,795 research outputs found
LDEF data: Comparisons with existing models
The relationship between the observed cratering impact damage on the Long Duration Exposure Facility (LDEF) versus the existing models for both the natural environment of micrometeoroids and the man-made debris was investigated. Experimental data was provided by several LDEF Principal Investigators, Meteoroid and Debris Special Investigation Group (M&D SIG) members, and by the Kennedy Space Center Analysis Team (KSC A-Team) members. These data were collected from various aluminum materials around the LDEF satellite. A PC (personal computer) computer program, SPENV, was written which incorporates the existing models of the Low Earth Orbit (LEO) environment. This program calculates the expected number of impacts per unit area as functions of altitude, orbital inclination, time in orbit, and direction of the spacecraft surface relative to the velocity vector, for both micrometeoroids and man-made debris. Since both particle models are couched in terms of impact fluxes versus impactor particle size, and much of the LDEF data is in the form of crater production rates, scaling laws have been used to relate the two. Also many hydrodynamic impact computer simulations were conducted, using CTH, of various impact events, that identified certain modes of response, including simple metallic target cratering, perforations and delamination effects of coatings
A Framework for Situation-based Social Interaction
This paper presents a theoretical framework for
computationally representing social situations in a robot. This
work is based on interdependence theory, a social psychological
theory of interaction and social situation analysis. We use
interdependence theory to garner information about the social
situations involving a human and a robot. We also quantify the
gain in outcome resulting from situation analysis. Experiments
demonstrate the utility of social situation information and of our
situation-based framework as a method for guiding robot
interaction. We conclude that this framework offers a principled,
general approach for studying interactive robotics problems
Damage areas on selected LDEF aluminum surfaces
With the U.S. about to embark on a new space age, the effects of the space environment on a spacecraft during its mission lifetime become more relevant. Included among these potential effects are degradation and erosion due to micrometeoroid and debris impacts, atomic oxygen and ultraviolet light exposure as well as material alteration from thermal cycling, and electron and proton exposure. This paper focuses on the effects caused by micrometeoroid and debris impacts on several LDEF aluminum plates from four different bay locations: C-12, C-10, C-01, and E-09. Each plate was coated with either a white, black, or gray thermal paint. Since the plates were located at different orientations on the satellite, their responses to the hypervelocity impacts varied. Crater morphologies range from a series of craters, spall zones, domes, spaces, and rings to simple craters with little or no spall zones. In addition, each of these crater morphologies is associated with varying damage areas, which appear to be related to their respective bay locations and thus exposure angles. More than 5% of the exposed surface area examined was damaged by impact cratering and its coincident effects (i.e., spallation, delamination and blow-off). Thus, results from this analysis may be significant for mission and spacecraft planners and designers
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