CRANFIELD UNIVERSITY JAVIER BUENO FERNANDEZ MODELLING OF THE ASCENDER SPACEPLANE AND DEVELOPMENT OF AN AUTOPILOT AND FLIGHT CONTROL SYSTEM SCHOOL OF ENGINEERING MSc Autonomous Vehicles Dynamics and Control MSc Academic Year: 2015 - 2016 Supervisor: Dr. Vaios Lappas August 2016 MSc AVDC Thesis Abstract The spaceplanes have been a feasible option to cut prices on the space missions. Because of their capability to be totally reusable, they can perform even more than one flight per day, launching small satellites in LEO orbits or carrying space tourists, which has become a very profitable market. The goal of this thesis is to develop a mathematical model of Ascender, a spaceplane designed by Bristol Spaceplanes. The mode will be created in Simulink, which provides a set of very useful tools in the aerospace field to simulate and create the model. The geometric data of the aircraft will be obtained from a 3D view map provided by the company, which will also be the basis to estimate the inertia moments, weights and gravity center. Around the aircraft model, a set of controllers will be created, each one operating in a different phase according to the propulsion system used in them (turbojet, rocket or thrusters). In the case of the turbojet, a proper autopilot will be designed which will enable the pilot to command an altitude, a speed and a waypoint route for Ascender to follow. In the rocket phase, the flight path angle and the Mach number will be controlled to obtain a suitable climb a limit the demand over the aircraft structure. Finally, during the unpowered phase (climb and glide back to Earth), the thruster will control the spaceplane attitude to facilitate the launch of the payload and to improve the comfort of the passengers. Al the control systems will be checked through their response to the different commands sent to them, so the time history of the controlled variables will be plotted to assure a good performance. Finally, a simulation of the whole flight of Ascender from a trim state at 4000 meters to the point where the turbojet starts again to help in the landing, will be carried out and the system variables will be monitored to guarantee a good system behaviour. I MSc AVDC Thesis Acknowledgements I would like to use this section to thank the people that has helped during the realization of this project, and during my academic life in general. First I would like to thank my supervisor Dr. Vaios Lappas for his support during the last six of months of hard work. He has been always keen to help me in any doubt and his guidelines have been very useful to achieve the results presented in this thesis. My partners in the AVDC masters of science. We all together have build a really good group friends that has made our year in Cranfield to be incredibly great. We were also available to help us each other during our work in the individual project, which has been proved to be very useful in order to go further in our work. Finally, I would like to thank my parents Rolando and Demetria for the incredibly support that they have given me during all my life and I will always be grateful for that.. It would have been impossible to arrive to this point without their help. II MSc AVDC Thesis Contents 1 Background 1 1.1 Introduction . 1 1.2 Origin . 1 1.3 Spaceplanes and types . 2 1.3.1 Sub-orbital . 2 1.3.2 Orbital . 3 1.4 SSTO . 5 1.5 Current Designs . 6 1.5.1 XCOR Lynx . 6 1.5.2 Skylon . 6 1.5.3 Venture Star . 7 1.5.4 AVATAR . 7 1.5.5 Ascender . 8 1.5.6 Spacecab . 8 1.5.7 Spacebus . 9 1.6 Sub-orbital spaceplane Comparison . 10 1.7 Orbital spaceplane Comparison . 10 1.8 Propulsion Systems . 11 1.8.1 Rocket Engines . 11 1.8.2 Airbreathing Engines . 13 1.8.3 Spaceplanes Engines . 15 1.8.4 Combine-cycle Engines . 16 2 Project Scope 17 3 Mission Requirements 17 4 Thrust Characterization 18 4.1 Trajectory Calculation . 18 4.1.1 Equations . 18 4.1.2 Turbofan Phase . 21 4.1.3 Rocket Phase . 22 4.1.4 Gliding Phase . 24 5 Ascender Model 26 5.1 Geometric and Weights Data . 26 5.2 Simulink Model . 28 5.2.1 Aerodynamic Forces . 30 5.2.2 Propulsion Forces . 32 5.2.3 Weight Forces . 35 5.2.4 Atmosphere . 36 5.2.5 Wind Angles . 36 6 Model Trimming 36 7 Autopilot 37 7.1 Actuators Model . 39 8 Turbojet Phase Autopilot 39 8.1 Speed Controller . 42 8.2 Altitude Controller . 43 8.3 Heading Controller . 44 III MSc AVDC Thesis 8.4 Pilot Commands . 46 9 Rocket Phase Controller 47 9.1 Flight Path Angle Controller . 48 9.1.1 First Section (8-20 km) . 48 9.1.2 Second Section (20-80km) . 48 9.2 Mach Controller . 49 9.3 Rocket Simulation . 50 10 Gliding Controller 51 11 Flight Simulation 52 11.1 Altitude . 53 11.2 Pitch Angle . 54 11.3 FPA Angle . 55 11.4 Mach Number . 56 11.5 Waypoint Following . 57 12 Conclusions 58 13 References 59 Appendices 61 A Appendix: Trimming Process 61 B Appendix B: Waypoint Following Algorithm 63 C Appendix C: Simulink Blocks 65 C.1 Custom Switch System . 65 C.2 Thruster Pitch Command . 66 D Appendix D: Aerodynamic Data 67 E Appendix E: Geometric Data 70 E.1 Wings and Tail . 70 E.2 Fuselage . 70 E.3 Engines . 70 E.4 Fuel Tanks . 71 E.5 Landing Gear . 71 IV MSc AVDC Thesis List of Figures 1 North America X-15 . 2 2 SpaceshipOne with Mothership . 3 3 IXV ............................................. 3 4 Space Shuttle . 4 5 Buran............................................ 4 6 Boeing X-37B . 5 7 XCOR Lynx . 6 8 Skylon . 6 9 Venture Star . 7 10 AVATAR .......................................... 7 11 Ascender . 8 12 Spacecab . 8 13 Spacebus . 9 14 Liquid Rocket Engine . 11 15 Solid Rocket Engine . 12 16 Hybrid Rocket Engine . 12 17 Turbofan Scheme . 14 18 Ramjet Scheme . 14 19 Pre-Cooling Process . 16 20 Reference Systems . ..