Aerotecnica Missili & Spazio最新文献

Calculating the temperatures of windows of space stations in Low Earth Orbit (LEO) is crucial for ensuring their structural integrity. We present a comprehensive thermal analysis that considers direct solar radiation, Earth’s albedo effect, infrared radiation from the Earth and convective heat exchange with the internal environment. The thermal balance equation incorporates the time variation of these contributions due to orbital motion for windows with different orientations, to determine the temperature of the materials, factoring in key parameters, such as absorptivity, transmissivity, reflectivity, and their dependence on the radiation wavelength spectrum. Referring to the conditions of the Cupola of the International Space Station as a paradigmatic example, we compare the thermal performance of two common window materials: fused silica and acrylic glass. Our results indicate that the higher transmissivity of fused silica makes it insensitive to solar and albedo radiation, reducing temperature values and their dependence on plate thickness and exposure variability due to orbital motion. In contrast, the higher absorptivity of acrylic glass results in much higher temperatures, proportional to the thickness, with a cyclical dependence on the orbital period. This analysis provides insights for the design and selection of window materials in space station construction, ensuring their durability and functionality in the conditions of LEO.

The reliable operation of satellites and their payloads hinges on a robust power system and an efficient energy storage unit capable of consistently meeting energy demands throughout a satellite’s lifecycle. This paper explores the development of an economical supercapacitor-based battery system tailored for CubeSat applications. It presents a highly efficient design that leverages readily available commercial off the-shelf (COTS) supercapacitors. In recent years, small satellites, particularly CubeSats, have demonstrated impressive performance levels akin to their larger counterparts. They have become instrumental in pioneering new technologies, clean energy solutions, and environmentally friendly materials for sustainable energy storage systems, particularly in the realm of power systems, energy storage, and high-power consumption requirements. As a result, there is a growing interest in storage systems that rely either entirely on supercapacitors or incorporate them in a hybrid fashion. Supercapacitors are favoured for their ability to deliver high power rapidly, quick recharge capabilities, and compact form factors. The designed supercapacitor-based battery system employs a series connection of two 2.7 V 500 F supercapacitors, equipped with a DC–DC converter, charge and discharge control system, as well as mechanisms for balancing and overvoltage protection. This innovative configuration empowers the CubeSat with a tailored energy supply for specific mission objectives and stands as a potential solution to address power supply interruptions.

Spacecraft trajectory optimisation represents a pillar for space mission development, as it allows the design of more cost-effective and high-performance operational concepts. In this context, the Mars exploration race, best epitomised by the Mars Sample Return mission (MSR), has highlighted the need to optimise not only the Keplerian phase trajectory, but also the proximity dynamics and the atmosphere environment one. In this paper, the Differential Dynamic Programming (DDP) optimisation algorithm is initially introduced as a proven second-order technique that relies on Bellman’s Principle of Optimality and successive minimisation of quadratic approximations. Then, a collection of modified DDP methods is presented for the purpose of enhancing the classic DDP weaknesses. Subsequently, a constrained DDP algorithm is implemented and applied to two case studies: a deep-space rendez-vous and a martian soil landing manoeuvre. The choice is to test the algorithm in different environments, showing the influence of gravity and atmosphere on the convergence properties. For both problems, a parametric and a convergence analysis is carried out to identify the best input parameters and the resulting trajectory optimisation process is displayed. Satisfactory results are achieved, proving the validity of the algorithm: order of few centimetres for position and some decimetres per second for velocity errors are reached. Furthermore, its adaptability allows to satisfy diverse requirements depending on the type of manoeuvre performed, extending its application field. Finally, some algorithm’s features are pointed out, investigating the influence of regularisation parameters and time of flight on the convergence process.

An aircraft's Air Data System (ADS) is essential for a number of reasons, such as situational awareness and safety. To compute the primary air data, namely pressures and flow angles, the ADS architecture has historically relied on physical sensors mounted on the aircraft's exterior. A lot of research has been done on the possibility of using synthetic reconstruction of air data as a substitute for these sensors. Only a small number of those examples, nevertheless, made it to the certification stage to be incorporated into an aircraft. This paper provides an overview of the design, integration and test of a Hybrid ADS architecture that relies on both sensors and synthetic estimator specifically designed to solve a calibration problem occurring during high AOA maneuvers on an already existing architecture. The avionics, safety, flight control, and aerodynamics departments worked collectively to implement this system in a multidisciplinary framework. In a laboratory environment, the suggested design and integration solution have been verified. Flight testing has been utilized to confirm the ADS's functionality, validate the systems and yield data for future enhancements. The goal of the entire procedure is to give the certification authority the compliance proof and to attain the required accuracy throughout the envelope.

Carrier landing of aircrafts is a challenge for control due to the existence of nonlinear wind disturbances and the requirements of changing reference trajectories. In this paper, a robust landing control system is presented for carrier landing of unmanned F/A-18 aircraft. In the control system, an augmented observer is applied to estimate the combined disturbances in the pitch dynamics of F/A-18 aircraft during carrier landing. Therefore, the control performance is improved through the control compensations from these estimations. Additionally, the controllers are designed to regulate the velocity, rate of descent and vertical position. A full model, including the nonlinear flight dynamics, controller, carrier deck motion, wind and measurement noise, is constructed numerically and implemented in software. Combining the observer with a proportional-derivative (PD) control, the proposed pitch control shows the better transient characteristics and stronger robustness than a proportional-integral-derivative (PID) controller. The simulations verify that the designed control system can make the aircraft quickly track a time-varying reference despite the existence of nonlinear disturbances and noise.