نشریه فناوری در مهندسی هوافضا
سال دوم شماره 2 (پیاپی 5، تابستان 1397)

Scramjet is a jet engine designed to fly at high speeds, and is actually a ramjet engine in which combustion takes place in supersonic conditions. Considering that the main use of this type of engine is in the aerospace industry and the development of this type of engine results in a major transformation in this industry, researchers are working to remove the technological barriers associated with these engines. The main objective of this paper is to investigate the performance of scramjet engines to provide the propulsion force of flying vehicles with high flying speeds. The behavior of the components, thermodynamic cycle of the engine, combustion chamber's cooling methods, material used in combustion chamber, the fuels used in this type of engines, and the burning stability problem in the present study have been discussed.

Nowadays, the reduction of pollutants emission from combustion processes is integrated to the design of combustors. The chemical reactor network approach is a applicable method for estimating the emission of pollutants such as NOx in combustion systemsdue to cost reductions, fast and appropriate accuracy in results. This method requires the initial flow field data to build the reactors network. In this paper, the application of computational fluid dynamics as one of the most commonly used methods in determiningthe flow field characteristics and providing basic information for the construction of reactors networks was investigated. In this paper various approaches of turbulent flow modeling, applied chemical mechanisms and combustion regimes were studied in order to use the results in constructing CRNs. Although CFD can enhance the constraction of CRNs and improve the results butit should be noted that increasing the fidelity of CFD results should not be the cause of adding computational costs because CRNs can provide appropriate results even with a minimal number of reactors.

In the present research about 50 high altitude test facilities (HATFs) in the world and ejectors of them have been analyzed. Practical information such as type of the ejector, operating fluid, procedure of fluid generation, operating pressure and temperature, Thermal protection and costs of construction and operation can be useful in developing space industries. The present study shows that in 87% of the 50 HATFs, central ejectors and in 76% of them water steam have been used. Water spray cooling is often used to provide thermal protection for ejectors. Based on the available references, the water mass flow rate for cooling system is in the range of 1.8 to 3.9 times of the mass flow rate of exhaust gases of the engines with thrust in the range of 0.11 to 204 kN. To produce water steam, the HATFs for solid and liquid fuel engines frequently employ the steam accumulators and steam generators, respectively.

The preliminary estimation of the weight at the conceptual design stage of the turbofan engine is one of the most important stages in designing the turbine gas engines. Hence, in this paper, the methods of preliminary estimation of the turbofan engine weight and then the parameters required for the implementation of each method are discussed. The statistical society in which information about the weight of sixty-four turbofen is presented. Therefore, various methods for estimating the weight of a engine are used to calculate the weighted information obtained from the statistical processing, the comparison and the weight of the engines. Finally, the results of this experiment are compared to the actual engine weight. Based on the results obtained, among the various methods, the error rate is the lowest error in the NASA weight estimation method, which is about 4.8%. In the following, based on the diagrams obtained from this comparison, we examine the effect of different parameters on the weight of the turbofan engine (the initial estimation of the weight is based on the weight of the engine for the state in which the engine is constant but the design of the aircraft is changed.) In the initial estimation method the weight is based on the engine components, allowing the design and weight of each unit separately, hence the design of new engines more than it is used.

The major purpose of this paper is to consider the strategy and long term approaches in th American U.S. Space Launch Systems (SLSs)’s technology development. Recently, new approaches has been interested by U.S.. The major roots of these approaches can be searched in the Small Unit Space Transportation and Insertion (SUSTAIN) program that is suggested by U.S. marine corps. The main objective of SUSTAIN is to convey facilities and equipmqnt to the any point of the earth in the minimum time and cost. Hence, the importance of this program leaded to develop the future SLSs’s technology in SUSTAIN orientation. Then, in this paper, the SUSTAIN’s needs is considered and also presented the new approaches in technology development of SLSs to meet the programm’s requirements.

It has been a long time that the idea of housing another planets and sending human to space are being followed seriously. Scientists have done a big effort in order to discover life signs in other planets and to select a suitable place for human beings to live in space. According to the IT service and technology selection, Ilan Mask, managing director of the SPIEC project and a prominent figure in the astronaut field, has been working to setup a base on Mars until 2030. However, there is no reliablity that the first permanent inhabitants of this planet would be human beings. It is possible that robots will migrate to the Mars before human beings. One of the most complex robots deployed to Mars is Curiosity with a special mission: searching for signs of life in Mars. This paper discusses the properties and achievements of the robots sent to Mars specially the most complex one, Curiosity.