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    Öğe
    A Multi-Objective Perspective to Satellite Design and Reliability Optimization
    (Pergamon-Elsevier Science Ltd, 2024) Tetik, Taha; Das, Gulesin Sena; Birgoren, Burak
    Development of a communication satellite project is highly complicated and expensive which costs a few hundred million dollars depending on the mission in space. Once a satellite is launched into orbit, it has to operate in harsh environmental conditions including radiation, solar activity, meteorites, and extreme weather patterns. Since there is no possibility of physical maintenance intervention in space, reliability is a critical attribute for all space and satellite projects. Therefore, the redundancy philosophy and reliability measures are taken into account in the design phase of a satellite to prevent the loss of functionality in case of a failure in orbit. This study aims to optimize the payload design of a communication satellite by considering the system's reliability, power consumption and cost simultaneously. Since these objectives are conflicting in their nature, a multi-objective optimization approach is proposed. We offer a systematic approach to the satellite design by determining the best redundancy strategy considering contradictory objectives and onboard constraints in the multibillion-dollar satellite industry. The proposed approach promotes trade-offs and sensitivity analyses between cost, power consumption and system reliability in the early design phase of satellites using Compromise Programming. By using different sets of weights for the objectives in our model, it is possible to address different types of satellites depending on their mission and priorities. Because of the NP-Hard characteristics of the reliability optimization problem and the nonlinear equation in the proposed model, the Simulated Annealing algorithm is utilized to solve the problem. As a case analysis, the implementation is carried out on the design of a communication satellite system with active hot-standby and warm-standby onboard redundancy schemes. Results reveal that huge savings in million dollars can be attained as a result of approximately 5% reduction in reliability.
  • [ X ]
    Öğe
    A Two-Phase Approach for Reliability-Redundancy Optimization of a Communication Satellite
    (Gazi Univ, 2024) Tetik, Taha; Das, G. Sena; Birgoren, Burak
    The development and launch of communication satellite projects pose significant challenges and costs. The expenses can range from several hundred million dollars, contingent on factors such as mission objectives, satellite system size and complexity including the launch vehicle, and ground infrastructure. Satellites must be designed to withstand harsh conditions in space, such as the extreme temperatures, radiation, and other hazards, while delivering reliable communication services to its users. However, once a satellite is launched, physical maintenance interventions become infeasible in the event of technical problems. Thus, reliability is a critical aspect for these expensive systems. This study aims to minimize the cost of a high-tech communication satellite by addressing design considerations that meet customer reliability requirements without exceeding power and redundant equipment limits. To achieve this goal, we propose an integer non -linear programming model in this research. To solve the satellite design problem, we adopt a two-stage solution approach. Conventional industrial practices in satellite design often involve iterative attempts to determine the redundancy level of onboard units based on customer reliability requirements. These processes rely heavily on the experience of design engineers who evaluate a limited number of alternatives to determine the number of redundant units, resulting in sub -optimal outcomes. In contrast, our proposed approach systematically handles the problem and yields optimal results. Our findings demonstrate that the proposed two-phase approach can achieve optimal redundancy levels within seconds.
  • Küçük Resim
    Öğe
    Bir İletişim Uydu Operatörünün Fırlatma Aracı Seçim Problemi İçin Kesin ve Bulanık VZA Yaklaşımlarının Karşılaştırılması
    (2017) Daş, G. Sena; Tetik, Taha
    Uzay endüstrisinde, bir uydu için fırlatma aracı seçimi kritik bir idari ve teknik karar verme problemidir. Seçilen fırlatma aracına bağlı olarak fırlatma maliyeti, milyon dolarlık bir uydunun toplam maliyetinin yüzde 20'si ila 50'si arasında değişebilir. Bu çalışmanın amacı, istenilen yörüngeye bir yere eş zamanlı iletişim uydusunu fırlatmak için kullanılan fırlatma aracı alternatiflerini, Çok Kriterli Karar Verme (ÇKKV) yöntemleri kullanarak analiz etmektir. Bu amaçla, kesin ve bulanık Veri Zarflama Analizi (VZA) yönteminin versiyonları ÇKKV yöntemi olarak kullanılmıştır. Fırlatma aracı seçeneklerinin değerlendirilmesi için sektör uzmanları tarafından oluşturulan kriterler hiyerarşisi kullanılmıştır. Kesin ve bulanık VZA yöntemlerinin çıktıları kıyaslanmıştır. Kıyaslama sonucunda VZA versiyonlarının, seçenekleri farklı sıraladıkları ama Seçenek 1'in genellikle sıralamanın ilk sırasında yer aldığı gözlenmiştir
  • Küçük Resim
    Öğe
    Launch Vehicle Selection for a Geostationary Communication Satellite using Data Envelopment Analysis
    (Ieee, 2017) Tetik, Taha; Das, G. Sena
    In space business, launch vehicle selection for a satellite is a crucial managerial and technical decision making problem taking into consideration of various qualitative and quantitative factors. The aim of this paper is to solve this complicated supplier selection problem by analyzing several Geostationary Transfer Orbit launch vehicle alternatives, which have very high costs measured in million dollars. For this purpose, Data Envelopment Analysis (DEA) is utilized and the results are compared with two popular Multi Criteria Decision Making (MCDM) tools namely, AHP and PROMETHEE. The results indicate that all applied methods ranked the same alternative as the best. However, such a strong consensus is not observed for the worst alternative. In this context, DEA seems to determine the best alternative using less information compared to AHP and PROMETHEE.