CONCEPTUAL DESIGN OF A STEALTH UNMANNED COMBAT AERIAL VEHICLE WITH MULTIDISCIPLINARY DESIGN OPTIMIZATION A THESIS SUBMITTED TO THE GRADUATE SCHOOL OF NATURAL AND APPLIED SCIENCES OF MIDDLE EAST TECHNICAL UNIVERSITY BY UĞUR ÇAKIN IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN AEROSPACE ENGINEERING JANUARY 2018 Approval of the thesis: CONCEPTUAL DESIGN OF A STEALTH UNMANNED COMBAT AERIAL VEHICLE WITH MULTIDISCIPLINARY DESIGN OPTIMIZATION submitted by UĞUR ÇAKIN in partial fulfillment of the requirements for the degree of Master of Science in Aerospace Engineering Department, Middle East Technical University by, Prof. Dr. Gülbin Dural Ünver _________________ Director, Graduate School of Natural and Applied Sciences Prof. Dr. Ozan Tekinalp _________________ Head of Department, Aerospace Engineering Prof. Dr. Hüseyin Nafiz Alemdaroğlu _________________ Supervisor, Aerospace Engineering Dept., METU Examining Committee Members: Prof. Dr. Serkan Özgen _____________________ Aerospace Engineering Dept., METU Prof. Dr. Hüseyin Nafiz Alemdaroğlu _____________________ Aerospace Engineering Dept., METU Prof. Dr. Altan Kayran _____________________ Aerospace Engineering Dept., METU Assoc. Prof. Dr. Ali Türker Kutay _____________________ Aerospace Engineering Dept., METU Assoc. Prof. Dr. D. Sinan Körpe _____________________ Aerospace Engineering Dept., THK Date: 30.01.2018 I hereby declare that all the information in this document has been obtained and presented in accordance with academic rules and ethical conduct. I also declare that, as required by these rules and conduct, I have fully cited and referenced all material and results that are not original to this work. Name, Last Name: Signature: iv ABSTRACT CONCEPTUAL DESIGN OF A STEALTH UNMANNED COMBAT AERIAL VEHICLE WITH MULTIDISCIPLINARY DESIGN OPTIMIZATION Çakın, Uğur M.S., Department of Aerospace Engineering Supervisor : Prof. Dr. H. Nafiz Alemdaroğlu January 2018, 54 pages The present study aims to develop a methodology for multi-disciplinary design optimization (MDO) of an unmanned combat aerial vehicle. At the current stage of optimization study, three disciplines are considered, which are aerodynamics, structural weight and radar cross section (RCS) signature. As objective functions, maximum range and minimum RCS signature are employed. To generate pareto-optimal solutions, multi-objective particle swarm optimization (MOPSO) function of MATLAB® is performed. To get aerodynamic coefficients of generated UCAV geometries, a high-fidelity aerodynamic analysis tool SU2 is employed. Moreover, to shorten computational effort, firstly, a meta-model for aerodynamic results is formed by performing multivariate adaptive regression splines (MARS) approximation. Structural and system weights are estimated by using statistical weight equations. After that, by using aerodynamic coefficients and estimated total weight, range is calculated. RCS signature values are calculated by conducting POFACETS which is an implementation of the physical optics approximation for predicting RCS of complex objects. Also, meta-model of RCS results is generated for decreasing the computational time. Finally, the developed framework is performed to optimize a UCAV planform as an example of the v framework’s capability. The pareto-front results for MDO computations are presented in detail at results and discussion. Keywords: Unmanned Combat Aerial Vehicle, Multidisciplinary Design Optimization, Multi-Objective Particle Swarm Optimization, Meta-Modelling, Conceptual Design. vi ÖZ ÇOK DİSİPLİNLİ TASARIM OPTİMİZASYONU İLE DÜŞÜK RADAR İZİNE SAHİP MUHARİP İHA KONSEPT TASARIMI Çakın, Uğur Yüksek Lisans, Havacılık ve Uzay Mühendisliği Bölümü Tez Yöneticisi : Prof. Dr. H. Nafiz Alemdaroğlu Ocak 2018, 54 sayfa Bu tezde, muharip insansız hava aracının (MİHA) çok disiplinli tasarım optimizasyonu için bir metodoloji geliştirilmesi amaçlanmaktadır. Optimizasyon çalışmasının şu andaki aşamasında aerodinamik, ağırlık kestirimi ve radar kesit alanı (RKA) izi gibi üç disiplin ele alınmaktadır. Amaç fonksiyonları olarak, maksimum menzil ve minimum RKA izi kullanılmaktadır. Pareto-optimal çözümleri üretmek için çok amaçlı parçacık sürü optimizasyonu (ÇAPSO) yöntemi uygulanmaktadır. Oluşturulan MİHA geometrilerinin aerodinamik katsayılarını elde etmek için yüksek doğruluğa sahip bir aerodinamik analiz aracı SU2 kullanılmaktadır. Burada, hesaplama zamanını kısaltmak için Multivariate Adaptive Regression Splines (MARS) yaklaşımıyla aerodinamik sonuçlar için bir meta model oluşturulmaktadır. Yapısal ve sistem ağırlıkları istatistiksel ağırlık denklemleri kullanılarak hesaplanmaktadır. Hava aracı menzil hesabı, aerodinamik katsayılar ve tahmini toplam ağırlık kullanılarak yapılmaktadır. RKA izi değerleri, karmaşık nesnelerin RKA'sını tahmin etmek için fiziksel optik yaklaşımın bir uygulaması olan POFACETS kodu yardımıyla hesaplanmaktadır. Burada, hesaplama süresini azaltmak için RKA sonuçlarının meta-modeli oluşturulmuştur. Bunların sonunda, tasarım aracının kapasitesinin bir örneği olarak MİHA dış geometrisinin vii optimizasyonu belirlenen amaç fonksiyonları için tasarım aracı kullanılarak yapılmıştır. Çok disiplinli tasarım optimizasyonu sonucu bulunan Pareto-optima sonuçları çalışma sonunda verilmektedir. Anahtar Kelimeler: Muharip İnsansız Hava Aracı, Multidisipliner Tasarım Optimizasyonu, Parçacık Sürü Optimizasyonu, Meta-Modelleme, Kavramsal Tasarım viii “If I have seen further, It is by standing on the shoulders of giants” Sir Isaac Newton ix ACKNOWLEDGEMENTS I would like to express my deepest gratitude to my supervisor, Prof. Dr. H. Nafiz Alemdaroğlu for his guidance, advice, criticism, insight, and encouragement throughout the research. I want to express my gratitude to my colleagues, Ethem Hakan Orhan, Halil Kaya, Orkun Şimşek, Senem Ayşe Haser, Ceren Orhan, Hüseyin Aktan, Hakan Tiftikçi, Tuğba Yıldırım, Tuğrul Yıldırım, Aykut Kutlu and my other friends who were there to give me support and advice during my study. I want to express my deepest gratitude to my fellows, Durukan Tamkan, Hasan Şener, Ali Ünal, Ali Yıldırım, Mustafa İçen who give me strength to live in Ankara. I would like to thank my parents and my wife who never ceased to give me encouragement and pray for me during my graduate study. x TABLE OF CONTENTS ABSTRACT ................................................................................................................. v ÖZ .............................................................................................................................. vii ACKNOWLEDGEMENTS ......................................................................................... x TABLE OF CONTENTS ............................................................................................ xi LIST OF TABLES .................................................................................................... xiii LIST OF FIGURES .................................................................................................. xiv LIST OF SYMBOLS ................................................................................................ xvi LIST OF ABBREVIATIONS ................................................................................. xviii CHAPTERS 1. INTRODUCTION................................................................................................ 1 1.1 Description of Unmanned Combat Aerial Vehicles (UCAV) ........................ 1 1.2 Literature Review ........................................................................................... 3 1.3 Aim of this study ............................................................................................ 6 1.4 Outline of the presented work ........................................................................ 6 2. DEVELOPMENT OF OPTIMIZATION FRAMEWORK ................................. 7 2.1 General Description of Framework ................................................................ 7 2.2 Aerodynamic Module ................................................................................... 13 2.3 Radar Cross Section (RCS) Module ............................................................ 17 2.4 Weight Estimation Module .......................................................................... 20 2.5 Optimization Module ................................................................................... 23 3. RESULTS AND DISCUSSIONS ...................................................................... 27 3.1 Results .......................................................................................................... 27 3.2 Discussions ................................................................................................... 32 4. CONCLUSIONS AND FUTURE WORK ........................................................ 41 4.1 Conclusions .................................................................................................. 41 4.2 Future Work ................................................................................................. 43 REFERENCES ........................................................................................................... 45 xi APPENDICES A. META-MODELLING TECHNIQUE ......................................................... 49 B. VALIDATION OF MOPSO ALGORITHM FOR MULTIDISCIPLINARY OPTIMIZATION PROBLEM .......................................................................... 53 xii LIST OF TABLES TABLES Table 2.1 Design variables and assumptions ..............................................................