A major challenge for extended human spaceflights in deep space is the dangerous exposure to space radiation. These high-energy particles pose significant risks to astronaut health. To mitigate these risks, effective radiation shielding is essential. In previous studies, aluminium has been used as a multilayer shielding material in GCR (Galactic Cosmic Rays) space radiation environment with high dose equivalent. Because of aluminium's secondary particle production, the overall effective dose equivalent for astronauts behind an aluminium shield is higher than for more advanced shielding materials. To further reduce the dose equivalent, the shielding effectiveness of various metal hydrides in GCR free space environment is investigated using HZETRN2015 (High charge (Z) & Energy TRaNsport) and OLTARIS (On-Line Tool for the Assessment of Radiation In Space) in this work. Metal hydride materials are chosen because of their capacity to store hydrogen. Among these materials, lithium hydride has demonstrated superior effectiveness as a radiation shield. Given this, the potential of a multilayer shield composed of polyethylene and lithium hydride is also being explored considering the tensile strength certain varieties of polyethylene like UHMWPE (Ultra High Molecular Weight Poly-Ethylene) can provide. In multilayer shielding, different materials can target different types of radiation, providing more comprehensive protection. The results from HZETRN2015 and OLTARIS transport codes are compared and found in agreement.
Laboratory methods for steady-state and transient testing are two well-known approaches for measuring the heat transfer coefficient. Transient methods are more widely used due to their lower cost and broader temperature range. However, their application in fibrous insulation is more limited due to the low thermal conductivity and non-homogeneous nature of these materials. Guarded hot plate and three-point methods are two significant transient techniques for measuring the heat transfer coefficient in fibrous insulations. This paper compares these two testing methods, with the primary evaluation criterion being the minimum variance in the final experimental results. The variance of the final results is inversely proportional to the determinant of the sensitivity matrix. To compute the sensitivity matrix, the transient temperature distribution across the insulation thickness is first calculated using an initial estimate of the heat transfer coefficient, obtained from other experimental sources. Changes in the number and placement of thermal sensors, the insulation geometry, and the test duration affect the determinant of the sensitivity matrix. The optimal experiment is determined by identifying the maximum determinant of this matrix. Studies show that in the three-point method, the optimal setup consists of two thermal sensors placed on an insulation layer with a thickness of 2 cm, over a duration of 100 seconds. In contrast, in the guarded hot plate method, the optimal setup includes two thermal sensors on insulation with a height of 5 cm, over a 300-second testing period. The analysis indicates that the variance of the final results in the three-point method is lower than in the guarded hot plate method, which can significantly enhance the accuracy of heat transfer coefficient measurements.
One of the important passive techniques to reduce the drag force is the use of microstructured surfaces. The structures of these surfaces, which are from the order of nanometers to several hundred micrometers, can be created randomly or in a regular and controlled manner, with different geometries and configurations on the surface, and by affecting the fluid flow, they can change the amount of drag. With the aim of studying the physics governing microstructures, this article will investigate the parameters resulting from air flow passing them, which include drag components, velocity profiles and shear stress. For this purpose, triangular microstructures with the same base and height of 50, 100, 200, 400 and 800 µm have been used, which are transversely exposed to air flow with velocity of 5 m/s and 25 m/s. Due to the emphasis of some articles on the flow slipping over the microstructures, the velocity profiles on these surfaces have been investigated, but finally, the change in the amount and direction of the shear stress has been described as the main mechanism of viscous drag reduction. Then, the effect of the size of the structures and the velocity of the flow has been investigated. The obtained results show that the trapped vortices among the transverse structures can reduce the viscous drag by reducing the amount of shear stress around the peaks and reversing its direction in the valleys. On the other hand, creating a pressure gradient inside and around the structures will lead to creating pressure drag. The sum of these two drag components, which depend on the size of the microstructures and the flow velocity, will finally determine the increase or decrease of the total drag.
The boundary layer behavior in hypersonic nozzle of a shock tunnel has been investigated by means of the computational fluid dynamics simulations. The state of boundary layer at the nozzle outlet can highly affect the downstream flow passing around the test model in the shock tunnel test section. The formation of shock and expansion wave systems towards the downstream diaphragm and the reflection and expansion waves towards the upstream shock tube were well-simulated after the diaphragm rupture. Focusing on the transitional boundary layer simulation, results of the optimal nozzle's steady-state flow indicate that the boundary layer enters the throat region, undergoes a phase transition, and then returns to a laminar state due to re-acceleration. The turbulence intensity in this region, coupled with the width of the transition zone, increases with higher upstream stagnation pressure. Furthermore, simulation of the unsteady starting flow shows that the passage time of unsteady waves and the quasi-steady region, have good agreement with the experimental results.
The attitude determination and control subsystem is a vital satellite subsystem that provides maneuvering and pointing. According to statistics, more than half of the launched small satellites use the reaction wheel as the principal executive mechanism to complete the attitude maneuvering task. The underactuated technical term describes systems with fewer actuators than the degrees of freedom. Construction constraints and actuator failures can result in an underactuated system. Underactuation of a satellite under operating conditions can reduce its in-orbit performance and cause mission failure. This paper first introduces an underactuated satellite and reviews satellite attitude control methods in healthy conditions. The following presents fault-tolerant control and various mechanisms for identifying underactuated conditions. Model-based methods effectively diagnose underactuated conditions as they align well with fault compensation control techniques and perform efficiently across all satellite operating conditions. Also, most of the works are focused on the observer. In addition, methods used to stabilize and control an underactuated satellite using a reaction wheel actuator are investigated. Finally, attitude tracking control in underactuated conditions is presented.
Space exploration and satellite deployment drive modern technological advancements. They are crucial for global communication, navigation, and scientific discovery. Satellites form the backbone of interstellar communication, ensuring reliable data transfer in both civilian and defense sectors. However, as space missions grow more complex, maintaining their integrity and security becomes a major challenge.Unmanned Aerial Vehicles (UAVs) play a key role in space missions. They assist in satellite deployment, orbital inspections, and inter-satellite communication. Yet, these cyber-physical systems face evolving cybersecurity threats that could jeopardize mission-critical tasks. Traditional intrusion detection systems struggle to counter the complex and dynamic cyber threats targeting UAVs in harsh space environments.This paper introduces a novel Deep Reinforcement Learning model to predict and mitigate cyber risks in space-related UAV missions. Using a publicly available dataset that combines cyber and physical UAV data, the model predicts multi-step threats such as Denial of Service, Replay, Evil Twin, and False Data Injection. This enables proactive threat mitigation. Compared to traditional machine learning models—Support Vector Machines, Random Forests, and Recurrent Neural Networks—the proposed model achieves superior performance, with 99.34% accuracy and an AUC score of 0.99.
The celestial navigation is one of the oldest navigation methods for determining the position, which is done by observing different celestial bodies such as stars. With the advancement of technology and the emergence of accurate imaging sensors, this method has entered a new stage, so that by processing images of stars and analyzing their data, the exact position of an observer can be determined in space or on land. This paper presents a novel method for determining the geographic location of a mobile system using an image of visible stars in the local sky at a specific time. The proposed method does not require any prior knowledge about the observer's position or orientation. Initially, a grayscale image of the sky is either generated using the Sky Map function in MATLAB, based on the SAO star catalog, or acquired directly from a star sensor. Spatial and frequency-domain features are extracted from the image and compared with features from a set of synthetic sky images corresponding to various geographic locations. A genetic algorithm is employed to optimize the matching process through a tailored fitness function. The key innovation of this research lies in the development of an algorithm capable of accurate localization using only a sky image, without reliance on auxiliary sensors or initial position data. The proposed approach is robust to noise and image rotation and is applicable across the entire Earth's surface. Simulation results confirm the effectiveness and high accuracy of the method for vision-based autonomous navigation.
One important passive technique for drag reduction is the use of microstructured surfaces. In recent years, the advantages of this method have led some airlines to reduce their fuel consumption by installing microstructured films on aircraft. To understand the physics governing microstructures, this article investigates the effect of V-shaped transverse microgrooves on the NACA 8-H-12 airfoil. For this purpose, grooves with a base and height of 150 μm are placed transversely at eight different locations on the airfoil surface and their effects are investigated at zero angle of attack (AoA) and at velocities of 35, 65, and 100 m/s. The results show that vortices trapped within the transverse microgrooves reduce viscous drag by decreasing shear stress magnitude near the peaks and reversing its direction within the valleys. However, the microgrooves also generate pressure drag due to pressure gradients created within and around the structures. The combined effects of these changes in viscous and pressure drag determine the overall change in total drag. Total drag can either increase or decrease depending on the microgrooved surface area, its location on the airfoil, and the freestream velocity. The maximum drag reduction observed in this study was approximately 6%, achieved with two 200 mm microgrooved surfaces located mid-chord on both the suction and pressure sides at 35 m/s.
The possibility of injecting a satellite into orbit using a single-stage carrier has been one of the challenges far from human hands since the past. Even in the past, to prove the impossibility of achieving this wish, various mathematical relations and equations have been expressed. But what has filled the hopes in recent years is the improvement of the technology level. The answer to the question of whether it is possible to achieve the circuit using a single-stage carrier with the current level of technology has recently received attention. In this research, an overview of the existing technologies and single-stage launchers is discussed and the path from the existing technology to the required technology is extracted. For this purpose, after modeling different subsystems, the design framework based on multi-subject optimal conceptual design and GA-SQP optimization algorithm has been developed and validated. Then, multi-objective optimal design (MDO) of a single-stage satellite carrier has been carried out and the feasibility of achieving a single-stage satellite carrier has been evaluated. Despite extracting the best structure, the results indicate the impossibility of achieving this product with the current level of technology. In the following, the minimum amount of technology jump required by each technology, including issues such as release, propulsion and structure, to achieve this task was carried out based on multi-objective optimal analysis (MDA) and the results for each technology are presented separately.
Magnetometer is one of the main sensors in satellite attitude determination and control subsystems and its data calibration plays an important role in mission’s success. In this paper, the subject of magnetometer calibration using two optimal approaches is analyzed and their robustness in the presence of measurement disturbances is investigated. In this regard, firstly, a measurement model which contains main magnetometer parameters, namely, biases, scale factors and non-orthogonality corrections is presented. Then, two approaches for magnetometer calibration are proposed. In the first approach which is a centered method, nonlinear magnetometer calibration problem is transferred to a linear problem and calibration parameters are derived. However, in the second method which is based on maximum likelihood approach, magnetometer calibration problem is considered as a nonlinear problem and calibration parameters are estimated. Two kinds of magnetic field profiles are considered to evaluate the performance of calibration methods for a LEO satellite. According to the results, accuracy of the maximum likelihood approach is much better than centered method. Finally, in order to assess the robustness of the two presented methods, 100 Monte Carlo simulations are performed. Based on the Monte Carlo simulations results, estimation of calibration parameters using maximum likelihood approach is much smoother and calibration parameters are estimated more accurately.
This study introduces a novel spacecraft attitude control framework designed to operate reliably under uncertainties and external disturbances. At its core lies a dual-component strategy: a controller and a disturbance observer, both engineered for fixed-time convergence. Unlike conventional finite-time methods, where stabilization speed depends on initial conditions, this approach guarantees a preset stabilization window, tunable via controller parameters giving engineers precise command over performance timelines. By modeling spacecraft attitude dynamics using modified Rodriguez parameters (MRP), the system is cast into a second-order nonlinear structure. A non-singular terminal sliding surface is developed to enforce fixed-time convergence, enabling the derivation of robust control inputs. To address real-world unpredictability, a universally robust exact differentiator (URED) observer estimates and neutralizes disturbances within the same fixed timeframe, ensuring seamless compensation. Stability is validated using Lyapunov theory, while comparative simulations against existing methods demonstrate that the proposed framework achieves faster convergence and superior tracking accuracy for both controller and observer. These advancements set it as a promising solution for critical space missions requiring rapid, precise attitude control, such as satellite docking or deep-space exploration.
Due to its effectiveness and practicality, the proportional-integral-derivative (PID) controller remains a cornerstone of industrial control systems. The precise tuning of controller parameters significantly impacts system dynamics, influencing key performance metrics such as rise time, settling time, overshoot, stability, and steady-state error. While conventional methods effectively tune PID parameters in linear systems, they are inadequate for nonlinear processes due to the complexity of dynamic equations. This study proposes applying the particle swarm optimization (PSO) algorithm for tuning PID controller parameters in a three-degree-of-freedom satellite attitude simulator. The simulator incorporates reaction wheel actuators for attitude control, providing a robust platform for implementing control algorithms and optimizing onboard computational processes. The PSO-based optimization algorithm was executed for various performance criterion functions, demonstrating advantages such as rapid convergence to optimal values and straightforward implementation in nonlinear control systems. PID parameters derived from the conventional Ziegler-Nichols method were also applied to the simulator to benchmark the nonlinear optimization performance. Experimental results comparing different PID parameter sets were analyzed based on time response characteristics during a predefined maneuver. The comparative analysis identified the optimal PID parameters, which were subsequently implemented for enhanced simulator performance.
Abstract: In this paper, a reflective-mode phase-variation microwave moderate range displacement sensor is proposed. It consists of a reader which is a one-port microstrip line terminated with a matched load, and a movable resonator (etched in an independent substrate), which exhibits three different resonance frequencies, two of them in low frequency range and close to each other, and the third one at a higher frequency. The sensing mechanism is based on the motion of the resonator along the microstrip line, with a small airgap in between. The phase of the reflection coefficient at the three resonance frequencies of the resonator is recorded at the input port of the reader. As a result, the motion of the movable resonator can be characterized. The phase of the reflection coefficient at the two lower frequencies is used to enhance the dynamic range, while the phase at the higher frequency improves sensor resolution.Index Terms—microstrip technology, microwave sensor, reflective-mode sensor, displacement sensor, phase-variation sensor.
One of the most significant challenges in space missions is controlling the noise level within the cabin. Mufflers or silencers are employed to mitigate noise. In the present study, the performance of a basic reflective silencer is first investigated analytically and numerically in its simplest configuration. Based on the analytical evaluation of the base muffler, maximum performance occurs at odd multiples of π/2, while minimum performance is observed at integer multiples of π. Following the analytical analysis, extensions in the form of expanded tubes, designed based on the analytical findings, are added to the muffler. The performance of the reflective muffler is calculated using the sound transmission loss parameter and transfer matrix method, and the results are compared with numerical simulations. The findings reveal that while the numerical results generally align with the analytical predictions, discrepancies exist. Specifically, at frequencies above 1370 Hz, non-ideal effects are observed in the numerical results. As frequency increases, the acoustic wavefront inside the chamber deviates from a planar state, leading to reduced muffler efficiency at higher frequencies. Non-planar waves between the two extended tubes (with lengths L/2 and L/4) form at resonant frequencies of 1026 Hz and 1371 Hz. Although the emergence of non-planar waves disrupts muffler performance, the muffler with a single L/2 extension still outperforms the base muffler. Moreover, the configuration with two extended tubes (L/2 and L/4) exhibits the best performance among all tested mufflers.
Electroaerodynamic (EAD) propulsion has gained considerable attention in aerospace research due to its ability to generate thrust even in rarefied atmospheres at high altitudes. This study presents a comprehensive analysis of the performance and optimization of a decoupled EAD propulsion system, emphasizing its potential advantages over conventional propulsion technologies. A hybrid genetic algorithm–sequential quadratic programming (GA-SQP) approach was employed to optimize the system across various thrust levels. The optimized results were compared with traditional electric motors, offering insights into key trade-offs between the two systems. Findings indicate that while the EAD propulsion system operates at higher voltages than electric motors—resulting in increased power consumption—it provides a distinct advantage in terms of weight. As thrust levels rise, the system's mass exhibits only a marginal increase. For thrust levels between 10 and 70 N, the maximum mass increment is limited to 333 g, making EAD propulsion particularly suitable for applications requiring high thrust-to-weight efficiency. Sensitivity analysis further reveals that increasing system volume enhances thrust without proportionally increasing power consumption, albeit at the cost of additional mass. Additionally, increasing the voltage across the system’s electrodes improves thrust and power consumption without affecting mass. Although higher power consumption necessitates larger energy storage and conversion systems, the minimal mass increase relative to thrust highlights the EAD propulsion system as a promising alternative for high-altitude and space applications where weight constraints are critical
The development of commercial suborbital spacecraft in the world in recent years has provided an opportunity to understand the effects of short-term space flight factors on the biology of living organisms. Plants are an important element of life support systems in space exploration, as they provide essential components for long-term human survival outside of Earth. Their seeds, as plant genetic reserves or germplasm, have been among the most important biological payloads to be transferred to space since the past. This study aimed to investigate the effects of a suborbital flight (Kavus biocapsule) on the germination indices of tomato seeds and the growth indices (epicotyl and radicle length) of plants grown from them. The height of the capsule launch was 133 km and the total duration of the launch was 900 seconds. The launch speed and acceleration were 1657.97 meters per second and 64 meters per square second, respectively. The duration of microgravity and hypergravity applied to biological samples in this launch was 245 and 68 seconds, respectively. The range of temperature fluctuations was between -84.5 and +264.48 degrees Celsius. After the launch and successful recovery of the biological payload, the seed germination and seedling growth indices were compared between the launch and ground control groups. Spaceflight stimulated the initial growth of seeds and positively affected the growth indices of tomato seedlings in the launch group compared to the ground control group. To our knowledge, data regarding the ultrafast response of plants to short-term spaceflight conditions is very limited. This report can provide new insights regarding the importance of studying the effects of short-term space flights on biological systems, especially plants.
In this article, beamforming methodologies for antennas are first reviewed, highlighting the pros and cons of each method. It is observed that each method offers unique advantages and limitations. Some of the key technologies used to provide beamforming antennas are also compared with consideration of complexity, beamwidth, price, scanning angle, frequency range, beamforming speed, and accuracy. It is shown that beamforming using plasma offers flexibility compared to other techniques while remaining relatively cost-efficient. Moreover, using plasma components, it is possible to conceal the entire antenna or parts of it. Based on these advantages, this study presents a low-complexity, low-cost plasma-based antenna for beamforming. This novel antenna combines an axial mode helical antenna surrounded by circular arrays of plasma elements, forming plasma cups around the helix. The plasma cups are used to control the direction and width of the radiated beam of the helix. Activation of a plasma cup enhances the beamwidth of the helix, while asymmetrically activated configurations allow for steering the end-fire beam pattern up to ±27°. A prototype of the proposed antenna structure has been fabricated, and measurements for different configurations of the plasma reflectors have been carried out. The concept and computational results have been validated by the strong agreement between the simulation and measurement results. The proposed antenna offers a cost-effective solution for scanning and target acquisition in space communications and radar systems.
Deployable solar arrays serve as the primary power source for many remote-sensing satellites. These arrays, characterized by their long, wide, and thin structure, exhibit significant flexibility, posing challenges to satellite attitude control. Remote sensing missions require rapid maneuvers to capture images within strict time constraints, yet such maneuvers induce oscillations in the deployable solar arrays, degrading image quality. This study presents an advanced attitude control strategy to mitigate the uncertainties introduced by solar array vibrations. An adaptive robust attitude controller is implemented to address model uncertainties and environmental disturbances. While the adaptive robust control method effectively manages attitude maneuvers with slew rates below 1 deg/s, high-frequency vibration amplitudes increase during rapid attitude adjustments. A dual-control approach is introduced to counteract this effect, integrating an adaptive robust attitude controller with an input shaping technique for vibration suppression. Simulation results confirm that the proposed control strategy enhances pointing accuracy, stability, and vibration attenuation, improving imaging performance in dynamic operational scenarios.
Feature detection is a critical component of visual odometry, directly influencing position estimation accuracy. This process forms the basis for identifying key points in images, playing a pivotal role in subsequent operations such as feature matching and motion tracking. This study examines the impact of various feature detection algorithms on position estimation accuracy in visual odometry, focusing on a comparative analysis of the Harris, FAST, SIFT, CenSurE, and ORB algorithms. Performance evaluation was conducted based on accuracy and computational efficiency in position estimation. Each algorithm's average errors and processing times were calculated and systematically compared using an image dataset. Results indicate that the CenSurE algorithm is optimal for real-time applications and scenarios demanding rapid processing due to its lower computational cost. Its high-speed feature extraction capability makes it particularly suitable for such use cases. Conversely, despite its higher processing time, the Harris algorithm offers superior accuracy in position estimation and angular measurement, making it a preferred choice when precision is prioritized over speed. The FAST and SIFT algorithms balance accuracy and computational efficiency; the FAST algorithm, with its lower processing time, performs effectively in horizontal orientations, whereas the Harris algorithm excels in precision. The ORB algorithm exhibits moderate speed and acceptable performance but demonstrates reduced accuracy in certain positional features. This study enhances the understanding of the trade-offs between accuracy and efficiency in feature detection for visual odometry, providing a foundation for further research in optimizing algorithm selection for specific applications.
Designing complex systems, especially in the space industry, is accompanied by challenges such as changes in components and their interactions. This article aims to facilitate the design of complex systems by introducing and examining the design structure matrix (DSM). The design structure matrix, by analyzing the relationships between components, helps improve the speed of design and implement optimal changes in systems. This article discusses the features and analyses of this matrix, as well as its limitations and challenges. Two matrices are developed for a remote sensing satellite under study. The first matrix is designed to examine the influence of each component on the design of other components. In this matrix, all components are listed along both the rows and columns (meaning it's a square matrix), and if one component affects the design of another, this influence is indicated in the matrix. These effects are determined by the design team of each subsystem. Furthermore, both direct and indirect effects are considered in the formation of this matrix, and the calculation method is detailed in this paper. The second matrix examines the relationships between different components. These relationships include electrical, mechanical, data, or thermal connections, which are identified based on design blueprints and represented in the matrix. A matrix is also developed to assess the impact of each component on the design of other components, and efforts have been made to make this matrix practical by examining and weighting the effects of components on each other. With the help of these two matrices, the impact of changing one component (adding, removing, or altering the design) on other components is examined. Additionally, for better analysis, a case study is conducted. In this case study, the impact of adding a star sensor to the considered satellite is investigated and required technical changes for supporting on extra star sensor, such as data interface and power line or mechanical interface have been investigated. The defined matrices increase the design speed for more technical and precise analyses and provide the expert with the tool to apply changes in the system in less time and without creating excessive design cycles.
