Asrel Aerospace Research Letters Latest Issue

In metropolises with populations reaching millions or even tens of millions, overcrowding leads to various problems. One of the most significant issues caused by this is traffic congestion. The most effective solution to traffic problems is undoubtedly the efficient use of public transportation. Due to factors such as safety, comfort, and punctuality, rail systems and air transportation are among the most preferred public transportation systems. However, overcrowding at stations and terminals, along with the architectural design that requires passengers to enter from the same points, leads to congestion in specific areas of trains. These issues not only reduce travel comfort but also increase passenger waiting times. As a result of these delays, especially in rail systems, daily schedules, train travel times, and station arrival times are affected. These disruptions create challenges not only for passengers but also for the operators of light rail systems. One of today's most popular fields of study, artificial intelligence, is making a name for itself with its successful applications in various domains. In our study, deep learning—a subfield of artificial intelligence—and digital image processing techniques are used to address this issue. These techniques aim to detect passenger density in light rail systems based on the number of passengers in each carriage. By directing waiting passengers at upcoming stations to appropriate carriages and doors, a more efficient system can be achieved, benefiting both passengers and rail system operators. Additionally, highly valuable data will be obtained for use in scheduling transportation services. With this data, it will be possible to identify the specific days, times of day, and locations experiencing the highest congestion. By taking factors such as trip frequency and vehicle capacities into account, a more cost-effective and efficient operational process can be implemented.

The aviation sector is rapidly evolving in parallel with technological advancements worldwide. This progress, combined with the need for efficient use of limited energy resources, drives the demand for robust, economical, and lightweight system designs. Within modern aircraft, numerous avionics systems must communicate quickly and reliably to ensure safe and efficient operation. To address challenges such as wiring complexity and system weight, communication protocols have been developed that support lightweight, efficient data exchange.One such protocol is the Controller Area Network (CAN), originally developed by Bosch for the automotive industry in the 1980s. CAN is a reliable and cost-effective serial communication protocol designed to reduce wiring complexity while supporting real-time communication. Its strengths—such as robustness, low latency, and fault tolerance—have led to its adoption in various domains including aviation, industrial automation, and defense.To address the specific needs of the aviation sector, the CANaerospace protocol was developed by Stock Flight Systems in 1998. This high-level protocol extends CAN by providing structured, modular, and fault-tolerant communication suitable for avionics applications. It supports both peer-to-peer and broadcast messaging, allowing for flexible and interoperable communication among systems. In this study, a data communication application based on the CANaerospace protocol was developed using LabVIEW. The system utilizes National Instruments’ NI USB-8473s hardware to connect a computer to a CAN network. The LabVIEW program can parse incoming messages according to the CANaerospace format, display them in a user-friendly interface, and allow users to send formatted messages. The developed tool not only demonstrates practical implementation of the CANaerospace protocol but also serves as a useful platform for education, prototyping, and avionic system testing. It bridges the gap between theoretical protocol design and real-world application, making it valuable for engineers and researchers in the aerospace field.

In this study, a uniquely designed aerospike rocket nozzle was developed, and its performance was compared both numerically and experimentally with that of a conventional De Laval rocket nozzle. Nozzles are critical components of rocket engines, responsible for accelerating and directing the high-energy exhaust gases generated in the combustion chamber to produce thrust. The geometry and aerodynamic characteristics of a nozzle significantly influence the overall efficiency, fuel consumption, and mission success of a rocket system. The type of nozzle used in a rocket engine varies depending on the mission profile, atmospheric conditions, and altitude range. Among the most widely used nozzle types are the De Laval and aerospike nozzles. While De Laval nozzles are optimized for specific altitude conditions with fixed geometries, aerospike nozzles can adapt to changing ambient pressures, maintaining high aerodynamic efficiency over a wide range of altitudes. This makes them particularly suitable for Single Stage to Orbit (SSTO) missions. Due to their altitude-compensating nature, aerospike nozzles provide more efficient thrust and reduced fuel consumption, especially at lower altitudes where environmental pressure varies significantly. In this research, both nozzle types were evaluated under identical conditions, including the same combustion chamber and propellant. Numerical analyses were conducted using ANSYS Fluent software to simulate pressure, temperature, and velocity distributions within each nozzle. Mesh structures, boundary conditions, and turbulence models were carefully selected to improve the accuracy of the simulations. Based on the numerical results, performance trends of each nozzle design were assessed, followed by experimental testing in a laboratory environment. Experimental measurements included thrust force, exhaust gas velocity, and temperature, which were then compared with the numerical data. The findings revealed a strong correlation between simulation and experimental results.

Airport runways are fundamental components of critical transportation infrastructure, requiring high resilience against natural disasters such as earthquakes. Earthquakes can cause significant structural and functional damage to critical transport infrastructure like airport runways. This study presents an analysis of the damage that occurs to airport runways under seismic effects and evaluates existing improvement and mitigation methods. Earthquakes induce various types of damage to runways. The main forms of damage observed due to seismic activity include soil liquefaction, settlement (including differential settlement), crack formation (surface cracking on the runway), surface deformations and structural distortions, drainage system failures, and losses in substructure stabilization. Runways constructed on alluvial soils are particularly vulnerable due to the high risk of liquefaction during earthquakes. Such damage can render runways inoperative, leading to significant delays in emergency response operations. Especially after high-magnitude earthquakes, the operational capacity of runways is observed to be severely affected. There are several pre- and post-earthquake ground improvement and mitigation measures that can be applied. From the perspective of mitigation strategies, current approaches involve both proactive and reactive measures. Proactive methods include the development of seismic design criteria, soil improvement techniques, and flexible pavement systems. Reactive methods comprise rapid damage assessment protocols, emergency repair techniques, and comprehensive rehabilitation programs. The findings of this study highlight the necessity of an integrated approach to enhancing the earthquake resilience of airport runways. This integrated strategy should encompass the entire lifecycle—from design to routine maintenance and strengthening activities—within a comprehensive risk management framework. Based on literature review and field observations from past earthquakes, it is concluded that the application of appropriate improvement methods significantly enhances the seismic performance of runway structures.

This study presents the design, simulation, and performance evaluation of a 2×2 Ka-band (18–21 GHz) phased array microstrip antenna developed for providing reliable internet connectivity aboard passenger aircraft. With the growing demand for high-speed in-flight internet services, especially over satellite communication links, antenna systems must offer compact, lightweight, and aerodynamically compatible designs without sacrificing electromagnetic performance. The proposed antenna is specifically optimized for fast-moving aerial platforms and offers a low-profile geometry suitable for seamless fuselage integration, ensuring minimal impact on the aircraft's aerodynamic efficiency. The antenna was designed using Ansys HFSS, a full-wave electromagnetic simulator, and analyzed in terms of key performance parameters such as return loss (S11), radiation pattern, gain, and bandwidth. The simulation results indicated a return loss of –32.47 dB at the center frequency, implying excellent impedance matching. The antenna also exhibited a wide bandwidth of 2.36 GHz, fully covering the desired Ka-band downlink frequency range. The maximum simulated gain was 14.90 dBi, demonstrating a focused radiation pattern and high directivity, which are essential for maintaining a stable satellite link during dynamic flight conditions. In addition to electromagnetic performance, a comprehensive link budget analysis was conducted to assess the viability of the antenna in a typical Ka-band satellite communication scenario. The energy-per-bit to noise power spectral density ratio (Eb/N₀) was calculated as 13.60 dB, and the overall system link margin was found to be 0.55 dB, which confirms that the antenna system can support reliable data transmission even under marginal link conditions. In conclusion, the designed 2×2 phased array microstrip antenna offers a promising solution for Ka-band satellite internet systems used in commercial aviation. Its favorable electrical characteristics, compact structure, and aerodynamic compatibility make it highly suitable for next-generation airborne connectivity applications.

This study presents a comprehensive energy and exergy-based performance analysis of the PT6B-37A turboshaft engine used in the Agusta A119 Koala helicopter under varying altitude conditions. The investigation focuses on engine behavior at altitudes of 0 m, 300 m, 600 m, and 900 m, within the framework of International Standard Atmosphere (ISA) conditions. The primary objective is to assess the thermodynamic performance of the engine and to determine the impact of altitude changes on efficiency and irreversibility. A hybrid modeling approach was adopted: the engine’s design point performance was simulated using GasTurb 14 software, and altitude-specific energy and exergy parameters were computed using a custom MATLAB-based analytical code. Additionally, detailed component-level analyses were conducted, focusing on the compressor, combustion chamber, turbine, and exhaust sections. According to the analysis results, the engine produced a shaft power of 712.3 kW at sea level, with an overall energy efficiency of 26.24%. As altitude increased, reductions of up to 9% were observed in shaft power and thermal efficiency, while specific fuel consumption and exergy destruction increased. The combustion chamber and exhaust were identified as the most sensitive components to atmospheric variations and the main sources of exergy losses. Chemical irreversibilities, entropy generation due to high flame temperatures, and pressure drops in the combustion process were among the key factors limiting overall efficiency. Furthermore, NOx emissions—evaluated as an environmental performance parameter—were found to decrease with increasing altitude, primarily due to lower combustion temperatures and reduced partial oxygen pressure. The findings provide valuable technical insights for engine manufacturers, operators, and researchers, offering guidance on altitude-responsive design solutions, mission planning strategies, fuel optimization, and environmental mitigation. This analysis may also contribute to the development of parameter-based design criteria for future hybrid-electric helicopter platforms.

The attitude control of a spacecraft is one of the most critical factors to ensure mission success. Satellites must maintain a constant orientation in space due to their operational objectives, such as communication satellites with directional antennas or those that depend on precise solar panel alignment to maximise energy efficiency. It is very important to keep the satellite stable at a predetermined position in space. To maintain this constant orientation and correct any disturbances, attitude control systems are used. The dynamics of such systems can be described using Newton's Second Law, which results in a set of non-linear equations for motion about the x, y and z axes. Due to their nonlinearity, these equations cannot be analysed directly using classical control methods based on transfer functions. PID (Proportional - Integral - Derivative) controllers are widely used in control systems, but their coefficients need to be determined appropriately. To obtain a suitable set of PID coefficients for satellite control via reaction wheels, the nonlinear system must first be linearised around a point close to the reference values. This ensures that the linear approximation accurately represents the system dynamics near the desired direction. This study aims to determine PID coefficients with respect to our desired control performance criteria. For this, the PID coefficients are calculated from the linearised system and applied to the original nonlinear model. For this calculation, the previously obtained linear model and actuator models are used. The PID coefficients are calculated by considering the desired settling time and overshoot. The PID coefficients are tested for linear and nonlinear models in simulation to show the effectiveness of the proposed approach.

This research aims to make a significant contribution to the literature on the use of hydrogen in aviation and to encourage the adoption of environmentally friendly alternatives. This review focuses on reducing carbon emissions in the aviation sector and advancing the shift toward environmentally friendly, sustainable energy sources. It explores the potential of hydrogen as an alternative fuel, with findings suggesting that hydrogen gas could serve as a viable replacement for the traditional Jet A-1 fuel used in aviation. In this context, various hydrogen storage methods are examined, with a particular emphasis on cryogenic tanks, which are considered both safer and more cost-effective. Increasing air traffic and fossil fuel dependency further deepen problems such as global warming, climate change, and environmental pollution. These negative effects of the current fuels used in airplanes on the climate have brought to the agenda the need for the development of cleaner and more sustainable alternative fuels worldwide. The study investigates the use of hydrogen-powered engines and fuel cell aircraft, assessing the performance, efficiency, and safety of hydrogen in aviation. This approach will contribute to defining the necessary steps for the sector's transformation. While aiming to increase the use of hydrogen in aviation for a more sustainable future, the project also presents innovative solutions to reduce carbon emissions in the aviation sector to zero. As a zero-emission fuel, hydrogen offers significant potential for promoting the widespread adoption of eco-friendly alternatives in aviation. Additionally, research into the design of hydrogen-powered aircraft and the specifications of the liquid hydrogen tanks used in these aircraft provides valuable insights into reducing the environmental impact of future aircraft designs. These efforts will accelerate the transition of the aviation industry to clean energy and contribute to a substantial reduction in carbon emissions.