Geological interpretation of a segment of Venus from radar images of the U.S.S.R. spacecrafts Venera -15 and -16

A first geological interpretation of a part of the Maxwell Mountains area is given using radar images of the Soviet spacecrafts Venera 15 and 16. The region is characterized by following features: plateaus, ridges and depressions, ring structures, volcanoes, and lineations of different types and, very probably, also of different age. The dominant surface modeling mechanism should be gliding processes connected to faults producing many complicated superpositions of features. To obtain more objective and reproducible, results a method was used for quantitative texture analysis to decipher some of the geological indications.     

A modular 550 watt, 25 watts per cubic inch power supply for nextgeneration aircraft

The development of the HVS-550 high-performance power supply is described. The HVS-550 was designed and built utilizing state-of-the-art surface mount construction, low-profile magnetics, and aggressive thermal management techniques. This combination allowed the module height to be only 0.58 in. The unique requirements of the military system that bounded the power-supply parameters are discussed. Cooling is provided either by liquid circulating through the chassis or by conduction through the card edges. The measured power supply efficiency is in excess of 85%, with 11-V output. The output noise spectrum is excellent because of noise-cancelling techniques utilized to achieve the level of performance required by the system     

NASA's new Mars Exploration Program: the trajectory of knowledge

NASA's newly restructured Mars Exploration Program (MEP) is finally on the way to Mars with the successful April 7 launch of the 2001 Mars Odyssey Orbiter. In addition, the announcement by the Bush Administration that the exploration of Mars will be a priority within NASA's Office of Space Science further cements the first decade of the new millennium as one of the major thrusts to understand the "new" Mars. Over the course of the past year and a half, an integrated team of managers, scientists, and engineers has crafted a revamped MEP to respond to the scientific as well as management and resource challenges associated with deep space exploration of the Red Planet. This article describes the new program from the perspective of its guiding philosophies, major events, and scientific strategy. It is intended to serve as a roadmap to the next 10-15 years of Mars exploration from the NASA viewpoint. [For further details, see the Mars Exploration Program web site (URL): http://mars.jpl.nasa.gov]. The new MEP will certainly evolve in response to discoveries, to successes, and potentially to setbacks as well. However, the design of the restructured strategy is attentive to risks, and a major attempt to instill resiliency in the program has been adopted. Mars beckons, and the next decade of exploration should provide the impetus for a follow-on decade in which multiple sample returns and other major program directions are executed. Ultimately the vision to consider the first human scientific expeditions to the Red Planet will be enabled. By the end of the first decade of this program, we may know where and how to look for the elusive clues associated with a possible martian biological record, if any was every preserved, even if only as "chemical fossils."     

The Production of Biologically Active Substances by Plant Cell Cultures in Space

The impact of the conditions of space flight on the productivity of cultures of the plant cells with respect to the biomass and the metabolites is investigated. The experiments were performed with the callus cultures of the cells of ginseng (Panax ginseng), red root puccoon (Lithospermum arythrorhizon), and macrotomia coloring (Macrotomia euchroma) onboard the orbital station Mirand American Space Shuttle. A more pronounced variation of the output of the metabolites is noted with respect to the ground control. This output depends upon the properties of the strain and conditions of the experiment.     

Evaluation of mixed mode-I/II criteria for fatigue crack propagation using experiments and modeling

In this study, in-plane mixed mode-I/II fatigue crack growth simulations and experiments are performed for the Al 7075-T651 aluminum alloy which is widely used in the aerospace industry. Tests are carried out under different mode mixity ratios to evaluate the applicability of a fracture criterion developed in a previous study to mixed mode-I/II fatigue crack growth tests. Results obtained from the analyses and experiments are compared with existing and developed criteria in terms of crack growth lives. Compact Tension Shear (CTS) specimens, which enable mixed mode loading with loading devices under different loading angles, are used in the simulations and experiments. In an effort to model and simulate the actual conditions in the experiments, crack surfaces of fractured specimens are scanned, crack paths are modeled exactly, and contacts are defined between the contact surfaces of a specimen and the loading device for each crack propagation step in the analyses. Having computed the mixed mode stress intensity factors from the numerical analyses, propagation life cycles are predicted by existing and the developed mixed mode-I/II criteria and then compared with experimental results.