نشریه علوم و فناوری فضایی
سال پانزدهم شماره 1 (پیاپی 50، بهار 1401)

In this research the free vibration analysis of simply supported grid stiffened doubly curved shells by using a refined higher order theory is presented. The advantage of the present theory in comparison with other higher order theories is investigation of the effects of trapezoidal shape factor in the stress resultants in order to obtain more accurate frequency results. The governing equations of motion and boundary conditions are obtained using Hamilton’s principle and solved by using the Galerkin method. In the case of grid stiffened shells, a distribution function is introduced for describing the physical discontinuity between the ribs and the bays. The results are validated by making comparison to those existed in the literature or those obtained using the present numerical simulation in ABAQUS/Standard solver. In most cases, validations illustrated excellent agreement between the results . Finally, the effects of geometrical properties, material property and layup on the frequency responses of the shell are discussed.

Very High Resolution Passive Scan Agile Earth Observation Satellites are able to maneuver around all their three body axes and scan the target area in different directions, simultaneously. The most stringent mid-level requirements which dominate their attitude determination and control subsystem performance are applied in detumbling and fine pointing modes. These performance requirements are maneuverability, agility, accuracy and stability. In this research, first, we derive the analytical and statistical relationships between quantitative criteria of mid-level requirements and spatial resolution as a high-level mission requirement, next the design drivers of reaction wheels are extracted consequently. Then the size, mass and consuming power of an operational satellite and the reaction wheels torque authority and momentum capacity is guesstimated based on its imaging payload size and specifications.

This study evaluates the expression level of genes that change by pressure changes in astronautics and diving disorders such as decompression sickness. This study was performed on five skilled divers to analyze the expression level of TLR-2, HSP-72, IL-1b, NF-kB, and MPO genes that are responsible for pro-inflammatory conditions. In addition, the expression level of DRD4 and BNIP3 genes (Astronaut index genes that were previously measured in a spacecraft study on mice) was analyzed on native Iranian samples. Blood samples were taken half an hour after diving, RNA was extracted, and cDNA was synthesized. Then, real-time PCR was done. Based on the results obtained using the T-Student statistical method, it was found that the expression level of all genes except MPO and TLR-2 genes increased significantly after exposure to pressure changes and diving activities. These conditions can be a permanent effect after pressure changes and can be considered an indicator for healthy people under stress in diving and astronautics.

Trajectory optimization is a familiar method for most of re-entry and Re-usable vehicles. This is because of the ability to include almost all of the problem constraints without facing restrictions such as time & Calculation issues. Adding or removing constraints in trajectory optimization problem has significant effects on overall optimization performance which even can upgrade the method to an on-line process. Most of optimization Algorithms such as nonlinear-programming need an initial guess and are also sensitive to it. Hence in this research management of initial guess is done to remove some constraints from optimization problem and transfer them to initial phase. Accordingly an effort is conducted through using a classic guidance method to satisfy constraints of distance error and angle of impact command. The output of guidance initial guess is then fed to the optimization problem. 6Dof Simulation results show the increase of optimization performance via reduced number of iterations and Optimization time and increased solution accuracy.

This paper is dedicated to modeling of fuel sloshing dynamics and its effect on the stability and control of the space vehicle. Sloshing due to the liquid movement in the fuel tank of a space vehicle's propulsion system can be effective on the vehicle’s control and stability. Force and moment interaction between fuel sloshing and space vehicle’s control system will be appeared as a feedback in the control system. With respect to simplicity of analyzing of a rigid body's equations of motion in comparison with a fluid dynamics equations and as a result reducing computational efforts, it is possible to apply a mechanical model instead. So in this paper fuel sloshing is modelled as a linear mechanical system to investigate its effect on the stability and control of the vehicle. For this purpose, two mechanical models, mass-spring and pendulum systems, are applied to model dynamics of a space vehicle with fuel sloshing and each system’s parameters are evaluated for simulat

In this article, a universal algorithm and engineering software is presented for the conceptual design of cryogenic rocket propulsion system. The algorithm consisting five engine working cycles: pressure fed, gas generator, staged combustion, closed and opened expansion cycles. For validation, the Vulcain and HM7Bengines were redesigned, the obtained results certifies that the main design parameters have less than 5% errors and the other less than 20%. One of the advantages of this software is the presence of abut150 parameters in the output and 14 diagrams related to the flow behavior in the thrust chamber and cooling vest, which allows the parametric study of the effect of input changes on the outputs.The modeling of mathematical functions and the combustion has been done, by using the MATLAB and CEAsoftware. Finally, by merging in Visual studio programming environment and with the help of C# programming language, a software with GUI is presented.

In present study, a hydrazine based monopropellant thruster decomposition chamber is simulated numerically. The catalyst bed separated in two sides, the particles size in upstream side is larger than those in downstream side. Effects of upstream side length and its particles diameter on catalyst bed characteristics were investigated. To this end, three standard particles sizes of mesh: 16.5, 25 and 30 for the upstream side and two standard particles diameter of 1/8 and 1/16 (in) for downstream side were analyzed. Additionally, three upstream side lengths of 2.5, 5 and 7.5 (mm) were used while the length of bed is 6.5 (cm). Simulations were performed in three bed loading coefficients of 16.5, 25 and 35 (kg/m2s). The related results showed the effectiveness of upstream side on flow and thermal fields are strongly depends on the ration of particles sizes in upstream and downstream sides. Moreover, the upstream side length and bed loading are two important factors affecting the upstream side effectiveness.

From the past, space activities which has been extremely important for governments as the main and traditional players in the space industry, are now attractive to non-governmental and private individuals, who are the new actors in the space industry. Undoubtedly, in this field, technology is a prerequisite for implementation and development of space activities. Developing and less developed governments are trying to pave the way for these activities by passing national space legislations, but it should be noted that there are still many obstacles in this way. One of these obstacles is existence of restrictive acts and regulations of developed countries on transfer of technology in space industry. Identifying dimensions of these barriers and limitations and evaluating them from the standpoint of intellectual property rights is the subject of this article. The conflict between tendency towards commercialization of space activities and tight control over technology transfer in the space industry is one of the results that this article has achieved.

Turbopump propulsion systems have been used in almost all launch vehicles. With the advancement of manufacturing technologies, especially in the use of composite and lightweight structures, the use of non-turbopump propulsion systems has been considered due to the reduction of operating costs. This study has been investigated the multi-disciplinary optimization design of a two-stage launch vehicle using a pressure-fed propulsion system for both stages. Two main propulsion systems including gas-pressure and self-pressure feeding systems, have been evaluated in different configurations on two launcher stages. To extracting the optimum and possible solution, the launcher mission also has been added as a design variable in the optimization algorithm. The launcher has been extracted and introduced for each specific configuration of the launcher to achieve a certain orbital altitude with the maximum carrying payload and minimum gross mass. For this purpose, the AAO multidisciplinary optimization design framework has been used. The system-level and subsystem optimizer of the GA-SQP algorithm have been chosen.