This paper presents the results of numerical modeling and vibration testing of a nanosatellite’s optical payload, aimed at assessing its mechanical stability under the mechanical impacts of launch. The purpose of the study is to compare finite element modeling (FEM) data with experimental testing to refine the computational model and improve the reliability of mechanical stability predictions. The methodology included an FEM analysis with an average damping coefficient, an adapter blank test, a resonance study with a low-level sinusoidal run, random vibration tests, and a sinusoidal pulse test. The FEM results showed an average yield margin of safety MoS = 2.5 with a minimum MoS = 1.8 in the primary mirror mount area. The adapter blank test confirmed the absence of natural resonances in the operating range. The resonance study revealed modes in the 300–1340 Hz range, with the most pronounced peaks in the secondary mirror bracket (520–600 Hz) and the electronics unit (1030–1100 Hz). A comparison of the root mean square (RMS) acceleration values between calculations and tests revealed discrepancies due to the heterogeneous nature of the damping. The values of ζ determined by the half-power method varied from 0.9% to 4.8%, which confirms the dependence of the damping properties on the frequency and localization of the modes. The obtained results confirmed the structural integrity of the payload, allowed for the localization of structural elements, and substantiated the need to consider actual damping coefficients in FEM models. The presented data can be used to optimize the design and improve mechanical stability during payload integration into the satellite platform.

Understanding melting processes in refractory materials under external stresses is important and can be of particular interest in harsh environment applications ranging from aerospace to nuclear and fusion energy where these materials have to simultaneously withstand the effect of high temperatures and complex stress states in such ways, that a melting process might be initiated in extreme conditions. However, most if not all of the prior research was focused on melting phenomena in the presence of hydrostatic compression. In our work, we investigate melting phenomena in pure tungsten under uniaxial tension, uniaxial compression, hydrostatic tension, and shear stress states. We explore these relationships numerically by molecular dynamics simulations employing extended Finnis–Sinclair (EFS) potential and two-phase method and compare our results with theoretical and experimental findings reported in the literature. The melting behaviour was investigated for all the studied stress states and compared both quantitatively and qualitatively on the basis of equivalent strain, Cauchy stress tensor invariants, and maximum shear stress. For uniaxial tension, hydrostatic tension, and shear stress an abrupt decline of stress-induced melting point values was detected after certain critical stress values. New high-temperature thermo-mechanical results are correlated with intricate structural changes taking place on the atomic scale during metal-melt phase transition.

This paper presents the design and numerical assessment of a compact short-wave infrared (SWIR) optical payload for a CubeSat nanosatellite platform. The proposed payload is intended to provide sequential imaging in selected SWIR bands using a revolver filter wheel while accommodating a long-focal-length optical system within a limited 3U volume. The optical layout is based on a modified Maksutov configuration with an effective focal length of approximately 550 mm and an aperture of 84 mm. The system is designed to achieve a ground sampling distance (GSD) of ≤15 m at an orbital altitude of 500–550 km. For sequential imaging in different regions of the SWIR range, filters with central wavelengths of 1.24, 1.6, 1.9, and 2.1 μm are used together with an additional broadband window. The optical performance was evaluated using spot diagrams and modulation transfer function (MTF) analysis for the selected spectral bands. A preliminary thermo-optical sensitivity assessment was also performed over the temperature range from −20 °C to +40 °C by considering temperature-induced changes in axial distances between optical elements and surface curvatures caused by material expansion. The results indicate that the MTF at the detector Nyquist frequency of 33 lp/mm remains above the selected threshold of 0.1 for the considered spectral bands and uniform temperature states. The proposed configuration demonstrates the feasibility of implementing a compact long-focal-length SWIR payload with filter-wheel-based band selection for CubeSat missions, while maintaining the required calculated image quality within the considered design-stage assumptions.

В статье рассматривается механическая устойчивость конструкции наноспутника формата 12U CubeSat. Платформы CubeSat широко применяются для дистанционного зондирования Земли, связи, а также проведения научных и технологических экспериментов. Надежность таких аппаратов определяется не только функционированием бортовых систем, но и жесткостью несущей конструкции, корректным размещением полезной нагрузки и способностью корпуса воспринимать механические воздействия, возникающие при запуске. Цель исследования заключалась в расчетном определении модальных и прочностных характеристик конструкции 12U CubeSat, а также в оценке надежности основных крепежных элементов. В работе использовано численное моделирование на основе метода конечных элементов. Геометрия корпуса была сформирована с учетом габаритов 232 × 245 × 363 мм, а в качестве основного конструкционного материала выбран алюминиевый сплав Al 7075. Расчеты выполнялись в программных средах MSC Apex и MSC Nastran/Patran. В расчетной модели панели корпуса были представлены оболочечными элементами, а подсистемы аппарата - в виде сосредоточенных масс. Анализ проводился с учетом спецификации Cal Poly, требований ECSS и рекомендаций NASA GEVS. В рамках исследования выполнены модальный анализ, расчет прочности при квазистатических нагрузках уровня 100 g, а также проверка болтовых соединений на сдвиг, растяжение и раскрытие зазора. По результатам расчетов первая собственная частота конструкции составила 365 Гц, что значительно превышает нижний предел 100 Гц, применяемый для аппаратов CubeSat, и подтверждает достаточную жесткость конструкции. Минимальный коэффициент запаса составил 1,36 по пределу текучести и 1,66 по пределу прочности. Анализ крепежных элементов также подтвердил наличие достаточного запаса прочности при рассматриваемых условиях нагружения. Таким образом, предложенная конструкция 12U CubeSat способна выдерживать расчетные механические нагрузки, возникающие при запуске. Полученные результаты могут быть использованы в качестве практической основы для интеграции полезной нагрузки, дальнейшего совершенствования конструкции и подготовки к последующим вибрационным испытаниям.