نشریه علوم و فناوری فضایی
سال پانزدهم شماره 4 (پیاپی 54، زمستان 1401)

The miss distance analysis of the first-order explicit guidance law (EGL) is carried out using linearized equation of motion in the normalized form in order to obtain normalized miss distance curves. The initial heading error, constant target, acceleration limit, radome refraction error, and fifth-order binomial control system are considered. Moreover, body rate feedback is added to the explicit guidance law as a well-known classical compensation method of the radome effect as in proportional navigation. The analysis is performed for different values of the power of the alpha function, defined as the time decrease rate of the zero-effort miss to unit control input. As a special case, the EGL with unit power gives the first-order optimal guidance strategy for minimizing the integral of the square of the commanded acceleration during the total flight time. For the performance/stability analysis, the rms miss distance versus turning rate time constant and radome slope can be plotted for different values of the power of alpha function.

The effects of injector pressure drop on the performance of a catalytic reactor are studied experimentally. The injectors were simple orifices. Dynamic interactions between the injector and the reactor determine the transient behavior of the system. Results showed that the injector pressure drop affected neither the decomposition reaction efficiency nor the ignition delay time. However, pressure response time increased, and pressure roughness decreased with increasing injector pressure drop. Interestingly, the response time curve had a slope change at a 20% pressure drop. As discussed in the paper, the slope change is a result of cavitation phenomena in high pressure drop. It is concluded that cold injector tests are not enough for injector design validation, and performance tests are necessary tasks.

Development in the aerospace industry is linked to the continuous pursuit of lightweight designs. Open-architecture composite structures are a new and novel use of composites for minimal-weight component design. It is reasonable to use efficient and advanced techniques such as radial braiding in the manufacturing of composite lattice tubular structures. In this article, an aerospace composite lattice tubular structure with a braided reinforcement system is studied. A method is developed to determine the parameters of the preform reinforcement. A new process has been created for the manufacture of lattice structures with a braided reinforcement system. A methodology has been developed for determining the technological parameters of radial braiding. A sample structure is manufactured and tested. Experimental studies of lattice structure samples were carried out in order to verify the methods for determining mechanical, structural, and technological parameters.

In this paper, Design, optimization, and implementation of a Transparent Pseudo-Noise satellite Ranging relay are presented. CCSDS and DSN standards were studied for requirements of on board hardware for LEO satellites and ground station. To optimize the performance of the relay, a ground station for a two-way ranging system was modeled in MATLAB according to the DSN standard architecture. The effects of non-ideal hardware for the Implementation of an on-board relay were simulated. The simulation results confirmed that the designed transparent relay hardware satisfies the requirements of CCSDS and DSN  ranging standards system and has no detrimental effect on it. Finally, the implemented relay was tested with a Transceiver similar to the ranging Transceiver was confirmed for operation.

Today, one of the main concerns of the Committee for the Peaceful Use of Outer Space (COPUOS) and its subcommittees is the issue of militarization in space law. Top space countries such as the United States, Russia and China have added to this concern by using advanced space military equipment. Therefore, the international community must look for desirable and practical solutions to solve this problem in order to prevent militarization and the creation of an arms race in space. Based on this, the present article tries to investigate the military prohibitions governing space activities in order to prohibit such activities in outer space by analyzing the military use of space and legal documents and explaining the conventional and customary system governing space treaties and by examining some dual-use space-based weapons; Conduct a descriptive analysis and reveal more about the negative aspects of the military use of space.

In this paper, in order to provide telecommunication coverage for a wide geographical area, the use of a network consisting of an LEO satellite and a Tethered-Balloon equipped with antenna pointing mechanism is proposed. The proposed telecommunication network is able to send the collected data to a mission center outside the covered region and receive the required telecommands, while providing a telecommunication link between the users in the covered region. To control and point the antenna beams towards desired targets, an Adaptive Dynamic Surface Controller is designed. Determining the required operating modes, designing a mode management algorithm and extracting the appropriate reference trajectories for each operating mode are among the discussed issues in this paper. The Uniform Ultimate Boundary (UUB) stability of the closed-loop system is proved and the performance of the control system is studied by simulation. The proposed communication network and control system are able to provide wide telecommunication coverage in remote areas or emergency situations.

A study of the effect of microgravity on the endothelial progenitor cells is useful both in understanding cardiac changes in astronauts and in using microgravity as angiogenic stimuli. The aim of the present study was to investigate the effect of microgravity on VEGFR-2 and CD34 angiogenesis markers. Following extraction of progenitor cells from peripheral blood and its confirmation, gene expression was assessed by real-time PCR, and cell viability was assessed by MTT assay. The extracted cells were endothelial progenitor cells in terms of shape and surface markers CD31 and CD144. Microgravity increased the VEGFR-2 gene expression by 3.5 times after 24 hours. CD34 expression increased by 50% after 3 h but reached control level after 24 hours. Microgravity appears to have a positive effect on the expression of angiogenic markers and stimulation of endothelial progenitor cells, and it may be used as a new environment to differentiate these cells into blood vessels and to treat heart disease.

Gravity is an influential force on living organisms on earth, including microorganisms. E. coli O157: H7 causes complications such as bloody diarrhea and hemolytic uremic syndrome in humans and immunization is the main way to fight it. Subunit B of Shiga-like toxin type 2 (STX2B), binding agent of bacterial toxin to target cells, is a candidate for the recombinant vaccine to prevent disease. Due to the quantitative and qualitative increase in the expression of some recombinant proteins under microgravity, the STX2B recombinant protein expression was examined under simulated microgravity conditions on clinostat device. After confirmation of the recombinant by immunological methods, its expression was performed under microgravity and after the protein purification by chromatographic column, its amount was measured. The results showed that despite the decrease in expression under microgravity, which was probably due to lack of proper aeration of the culture medium, recombinant protein was still produced under microgravity condition.

In this study, the effects of geometry and spiral rifling like guides inside the injection nozzle on the performance of an engine are investigated, using AVL Fire software. To do so, firstly injectors with different nozzle geometries and their resultant spray patterns were simulated. Numerical results of this step show that creation of spiral rifling like guides inside the nozzle increases the spray cone angle and improves fuel atomization quality. In the next step, effects of using forgoing nozzle geometries on sample engine characteristics were studied and the related results compared to those of common cylindrical injectors. Numerical results of this step clearly show the superior performance of nozzles with spiral rifling like guides. In this case, SFC reduces up to 32 percent while the engine power and it's torque rises more than 63 percent. Also the amount of pollutants like NOx reduces 12 percent with respect to common cylindrical nozzles.