Developing a Comprehensive Power Simulation Model for the MEMESat-1 CubeSat Using Orbital Dynamics

The University of Georgia’s Small Satellite Research Lab’s Mission for Education and Multimedia Engagement Satellite (MEMESat-1) requires the use of variables such as power generation, power draw, orbital path, packet size, and data processing times. As power generation and charge varies, MEMESat-1 will automatically transition through three operational modes to prevent battery depletion and halt system processes in case of anomalies. Taking these variables and operational modes into account, the MEMESat-1 Mission Operations (MOPS) team will use FreeFlyer software to analyze power generation and draw during MEMESat-1’s orbital cycle. The power limitations of MEMESat-1 are budgeted based on battery and solar cell specifications implying the necessity of power simulations by MOPS

Elastic forces that do no work and the dynamics of fast cracks

Elastic singularities such as crack tips, when in motion through a medium that is itself vibrating, are subject to forces orthogonal to the direction of motion and thus impossible to determine by energy considerations alone. This fact is used to propose a universal scenario, in which three dimensionality is essential, for the dynamic instability of fast cracks in thin brittle materials.Comment: 8 pages Latex, 1 Postscript figur

Scanning electrochemical microscopy as a local probe of oxygen permeability in cartilage

The use of scanning electrochemical microscopy, a high-resolution chemical imaging technique, to probe the distribution and mobility of solutes in articular cartilage is described. In this application, a mobile ultramicroelectrode is positioned close (not, vert, similar1 μm) to the cartilage sample surface, which has been equilibrated in a bathing solution containing the solute of interest. The solute is electrolyzed at a diffusion-limited rate, and the current response measured as the ultramicroelectrode is scanned across the sample surface. The topography of the samples was determined using Ru(CN)64−, a solute to which the cartilage matrix was impermeable. This revealed a number of pit-like depressions corresponding to the distribution of chondrocytes, which were also observed by atomic force and light microscopy. Subsequent imaging of the same area of the cartilage sample for the diffusion-limited reduction of oxygen indicated enhanced, but heterogeneous, permeability of oxygen across the cartilage surface. In particular, areas of high permeability were observed in the cellular and pericellular regions. This is the first time that inhomogeneities in the permeability of cartilage toward simple solutes, such as oxygen, have been observed on a micrometer scale

Fundamental Studies Relating to Systems Analysis of Solid Propellants : Progress Report No. 6 - GALCIT 101, Subcontract No. R 69752, January 1, 1960-May 31, 1960

Previous reports of this series have attempted to define some of the important parameters affecting structural integrity of solid propellant rocket grains. Three general areas have been discussed, namely material properties, analytical procedures, and criteria for mechanical failure. This particular report is devoted to failure criteria, including both limiting deformation and fracture. First of all, the characteristic material properties of filled and unfilled elastomers are described, followed by a brief description of current and proposed tests which can be conducted to obtain experimental information relating to these characteristics in such a form that they can be incorporated in structural integrity analyses. In particular, the necessity for multi-axial tests is stressed in conjunction with minor requirements for new experimental equipment. The selection of appropriate fracture criteria is discussed. Most progress, however, can be reported only in criteria for unfilled elastomers for small and large strains where it appears a distortion strain energy density may be used. It is necessary to delay any really definitive remarks upon filled elastomers or actual grain composites, and subsequent use with cumulative damage analyses, until additional experimental data for propellants is forthcoming