High strength aluminum alloy 7075 is used in aerospace applications. This alloy is considered unweldable using fusion welding processes. Friction stir welding being a solid state process has been proved to be a suitable process for obtaining sound welds of these materials. Although no solid–liquid phase transformation occurs during friction stir welding, relatively high temperatures, up to 475 °C for AA7075 aluminum alloy, are generated by friction between the tool and the workpiece. This produces modified microstructures that may be more susceptible to corrosion than the parent alloy. In the current study, 16 mm thick rolled AA7075–T651 aluminum alloy plates were joined using friction stir welding. The corrosion behavior of base material and friction stir welds was investigated using the Salt fog test (ASTM B117). It was observed that the corrosion resistance of the welds in the basic solution is better than that in the acidic and neutral solutions. In contrast, no significant difference has been found in the corrosion resistance of the base material with change in pH value. It was also found that the corrosion rate decreases with increase in time of exposure. It has been observed that corrosion attack is greater in the weld region than in the parent material and within the weld, the heat-affected zone has been found to be more susceptible to corrosion compared to the weld nugget and thermo-mechanically-affected zone regions. Transmission electron microscopy studies showed coarser precipitates and wider precipitate-free zones in the heat-affected zone which are concluded to be reasons for more susceptibility to corrosion.

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For any space mission to be successful it is necessary to guide the satellite to revolve in the right orbit and gather all the required data without any flaws. Among the many spacecraft subsystems contributing in this regard, Star sensors are the attitude estimation sensors installed in the satellites in order to determine the exact location of the satellite. It helps to bring back the satellite to the required position if there is any deviation from its path. Star sensor captures the image of any of the predetermined reference star. This image is compared with that of the image of the same star captured from the Earth. By this comparison and with the help of star catalogs, digitizers and microprocessors, the attitude and inclination of the satellite is determined.

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