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A number of challenges in the development and application of flying qualities criteria for modern aircraft are addressed in this dissertation. The history of flying qualities is traced from its origins to modern day techniques as applied to piloted aircraft. Included in this historical review is the case that was made for the development of flying qualities criteria in the 1940's and 1950's when piloted aircraft became prevalent in the United States military. It is then argued that UAVs today are in the same context historically as piloted aircraft when flying qualities criteria were first developed. To aid in development of a flying qualities criterion for UAVs, a relevant classification system for UAVs. Two longitudinal flying qualities criteria are developed for application to autonomous UAVs. These criteria center on mission performance of the integrated aircraft and sensor system. The first criterion is based on a sensor platform's ability to reject aircraft disturbances in pitch attitude. The second criterion makes use of energy methods to create a metric to quantify the transmission of turbulence to the sensor platform. These criteria are evaluated with airframe models of different classes of air vehicles using the CASTLE 6 DOF simulation. Another topic in flying qualities is the evaluation of nonlinear control systems in piloted aircraft. A L1 adaptive controller was implemented and tested in a motion based, piloted flight simulator. This is the first time that the L1 controller has been evaluated for piloted handling qualities. Results showed that the adaptive controller was able to recover good flying qualities from a degraded aircraft. The final topic addresses a less direct, but extremely important challenge for flying qualities research and education: a capstone course in flight mechanics teaching flight test techniques and featuring a motion based flight simulator was implemented and evaluated. The course used a mixture of problem based learning and role based learning to create an environment where students could explore key flight mechanics concepts. Evaluation of the course's effectiveness to promote the understanding of key flight mechanics concepts is presented. / Ph. D.

Atmospheric Flight Mechanics (AFM) is one of the cornerstones of aeronautical engineering and includes subjects like aerodynamic prediction, stability and control, dynamics, and vehicle design. These topics are critical to the success of aircraft development, so AFM is considered one of the most important foundational knowledge areas for aerospace engineering. Unfortunately, students graduating from aerospace engineering programs are often underprepared to perform in AFM jobs. This ongoing research focuses on developing a blueprint for assessing conceptual understanding of AFM concepts. Since existing literature suggests that novices and experts organize knowledge differently, comparing students' and experts' mental models can shine a light on the alternative conceptions that students retain post-instruction. As such, framing the study around synthetic mental models can be advantageous. To explore these mental models, three types of data have been collected and analyzed. Document analysis was done on course documents to identify what concept relationships were being presented to the students. Class observations were conducted to analyze how concepts are introduced to students and what relationships are highlighted by the instructor. Finally, a concept mapping activity was facilitated to study the mental models that the students built after instruction. The results show a lack of synthetization between the knowledge introduced in the classroom and students' prior knowledge which translated into student mental models that do not meet some of the expectations of the course. Moreover, this study highlights the importance of the instructor's awareness of their own expectations for learning and knowledge synthetization in the design of an AFM course. / Doctor of Philosophy / Conceptual understanding research has often focused on how students develop their understanding of scientific concepts that are difficult to grasp. Through this research, many assessment techniques have been developed and implemented in the design of STEM courses. However, many of these techniques and implementations have been limited to K-12 or introductory engineering courses. Atmospheric Flight Mechanics (AFM) is an important part of the aerospace curriculum that has yet to be studied under the conceptual understanding lens. The goal of this study was to investigate how students develop AFM conceptual understanding using a synthetic mental model framework. This study focused on answering three questions, how are students being introduced to AFM concepts?, how do students' mental models develop throughout the semester?, and how do the students' and instructor's mental models compare?. Through the exploration of class documents, class observations, and concept mapping activities, this research found that students are having a hard time making sense of new knowledge based on their previous understanding of similar topics. By trying to integrate this new knowledge with their previous mental models, students are developing synthetic mental models that do not align with the scientific explanations of the topic. This study also found that instructors are often unaware of their own knowledge and expectations for learning which makes knowledge synthetization harder for the students. Therefore, addressing these issues during course design could make an AFM course easier to understand for students.

During planetary entry, a vehicle uses drag generated from flight through the planetary atmosphere to decelerate from hyperbolic or orbital velocity. To date, all guided entry systems have utilized lift-modulation trajectory control. Deployable aerodynamic devices enable drag-modulation trajectory control, where a vehicle controls its energy and range during entry by varying drag area. Implementation of conventional lift-modulation systems is challenging for deployable systems. In contrast, drag-modulation trajectory control may be simpler and lower-cost than current state-of-the-art lift-modulation systems. In this investigation, a survey of analytical methods for computing planetary entry trajectories is presented and the approximate analytical solution to the entry equations of motion originally developed by Allen and Eggers is extended to enable flight performance evaluation of drag-modulation trajectory control systems. Results indicate that significant range control authority is available for vehicles with modestly sized decelerators. The extended Allen-Eggers solution is closed-form and enables rapid evaluation of nonlifting entry trajectories. The solution is utilized to develop analytical relationships for discrete-event drag-modulation systems. These relationships have direct application to onboard guidance and targeting systems. Numerical techniques were used to evaluate drag-modulation trajectory control for precision landing and planetary aerocapture missions, including development of prototype real-time guidance and targeting algorithms. Results show that simple, discrete-event drag-modulation trajectory control systems can provide landed accuracies competitive with the current state of the art and a more benign aerothermal environment during entry for robotic-scale exploration missions. For aerocapture, drag-modulation trajectory control is shown to be feasible for missions to Mars and Titan and the required delta-V for periapsis raise is insensitive to the particular method of drag modulation. Overall, results indicate that drag-modulation trajectory control is feasible for a subset of planetary entry and aerocapture missions. To facilitate intelligent system selection, a method is proposed for comparing lift and drag-modulation trajectory control schemes. This method applies nonlinear variational techniques to closed-form analytical solutions of the equations of motion, generating closed-form expressions for variations of arbitrary order. This comparative method is quantitative, performance-based, addresses robustness, and applicable early in the design process. This method is applied to steep planetary entry trajectories and shows that, in general, lift and drag-modulation systems exhibit similar responses to perturbations in environmental and initial state perturbations. However, significant differences are present for aerodynamic perturbations and results demonstrate that drag systems may be more robust to uncertainty in aerodynamic parameters. Finally, the results of these contributions are combined to build a set of guidelines for selecting lift or drag-modulation for a Mars Science Laboratory-class planetary entry mission.

This report summarizes the task of conceptually designing an UAV suited for agricultural observation of Swedish farmland. The design of the UAV was divided into two parts. This report focuses on the flight mechanics, performance analysis, and cost analysis of the UAV, whereas the other part centers around the aerodynamic performance. Therefore, some elements, such as the wing selection, will not be subject to discussion in this report. A set of different requirements were posed, such as having a flight time longer than two hours, being able to between 5-10 m/s, able to perform vertical take-off and landing, fly at a maximum of 100 meters, and weighing less than 5 kg. By using different sources of literature, reasonable assumptions, and Matlab analytics, a UAV was designed that met all constraints demanded. The cost analysis yielded a result that was reasonable, which overall makes this conceptual UAV a realistic product that could be manufactured using the project design.

The field of man portable UASs (Unmanned Aerial Systems) is currently a key area in improving the fielded warrior's capabilities. Pressurized aerostructures that can perform with similar results of solid structures can potentially change how this objective may be accomplished now and in the future. Construction with high density polymers and other composites is currently part of active inflatable vehicle research. Many shape forming techniques have also been adapted from the airship and balloon manufacturing industry. Additional research includes modeling techniques so that these vehicles may be included in simulation packages. A flight dynamics simulation with reduced-order aeroelastic effects derived with Lagrangian and Eulerian dynamics approaches were developed and optimized to predict the behavior of inflatable flexible structures in small UASs. The models are used to investigate the effects of significant structural deflections (warping) on aerodynamic surfaces. The model also includes compensation for large buoyancy ratios. Existing literature documents the similarity in structural dynamics of rigid beams and inflatable beams before wrinkling. Therefore, wing bending and torsional modes are approximated with the geometrically exact ntrinsic beam equations using NATASHA (Nonlinear Aeroelastic Trim And Stability for HALE Aircraft) code. An approach was also suggested for inclusion of unique phenomena such as wrinkling during flight. A simplified experimental setup will be designed to examine the most significant results observed from the simulation model. These methods may be suitable for specifying limits on flight maneuvers for inflatable UASs.

The only aeroballistic laboratory of Turkey is the Flight Mechanics Laboratory, FML of T&Uuml / BITAK - SAGE. In FML, flight profiles of projectiles are reconstructed using their tear marks on paper sheets, called yaw cards. Tear marks are created on yaw cards as projectiles pass through them. These yaw cards are tightly stretched to metal frames which are positioned normal to the direction of projectile flight path. The use of yaw cards for flight profile reconstruction is a low cost and reliable solution. However, the yaw card method requires a heavy workload for the analysis of tear marks. Yaw cards collected from the frames are fed through an optical scanner and converted to digital images. These digital images are then processed by operators to calculate the projectile&rsquo / s flight position and angles. To automate this manual process, an algorithm is developed by using histogram based segmentation techniques, custom search algorithms, and Radon transform. This algorithm identifies and locates the projectile marks and finds angle of attack, angle of side slip and roll angle at each frame station by conducting the necessary transformations. Using this automated algorithm, a considerable amount of improvement is accomplished in terms of both decreasing the analysis time and increasing the accuracy of flight profile reconstruction.

This thesis presents a tool for conceptual design of a traditional configuration aircraft by using a parametric six degrees of freedom (6DOF) flight mechanics model implemented in the Modelica Language using Wolfram System Modeler. Being first only able to model and simulate the uncontrolled flight of an aircraft with fixed mass and centre of gravity (CG), and requiring detailed aerodynamic parameters as an input, the 6DOF model is improved by developing new features to reduce the number of required inputs while also increasing the data output of the simulations. First, the propulsion submodel is added with models for alternative propulsions to the existing model of turbofan engines. The energy and fuel consumption is also modelled for all propulsion types, and thus the aircraft model has no longer fixed mass properties, except for aircraft with electric propulsion. To further evaluate the fuel consumption for pre-defined flight missions with given flight speed, altitude and track angles, autopilots for a few different aircraft types are developed. Additionally, the 6DOF model is improved by establishing algebraic and statistical relationships between the aircraft geometric input parameters, aerodynamic coefficients and moments of inertia such that the values for the two last mentioned can be estimated inside the 6DOF model based on the minimum amount of design variables, geometric input parameters and aerodynamic properties of the 2D airfoils used in the wings. Ultimately, the improved 6DOF model is evaluated and analysed in terms of its performance in initial weight estimation on aircraft conceptual design stage as well as in predicting the aerodynamic properties.

<p>Aerocapture has been envisioned as a potential orbit insertion technique for planetary destinations with an atmosphere. Despite not being flight proven technique, many studies found in the literature and recent mission proposals have employed aerocapture into their respective mission designs. The potential varying levels of trajectory dispersions experienced during atmospheric flight at each destination drives the need for robust and fuel-efficient guidance and control solutions. Existing guidance algorithms have relied on tracking precomputed reference trajectories, which are computed using significant simplifications to the flight mechanics, are not generally designed to be fuel-efficient, and require tedious performance gain tuning. When simulated with higher levels of uncertainty, the existing algorithms have been shown to produce large orbit insertion errors. Furthermore, existing flight control methodologies have been limited in scope to bank angle modulation. While some studies have introduced new methodologies, such as drag modulation and direct force control, they haven’t been tested at the same level of rigor as the existing methods. Advances in on-board computational power are allowing for modern guidance and control solutions, in the form of numerical predictor-corrector algorithms, to be realized. This dissertation presents an aerocapture guidance architecture based on a numerical predictor-corrector algorithm. Optimal control theory is utilized to formulate and numerically obtain fuel-minimizing flight control laws for lifting and ballistic vehicles. The unified control laws are integrated into a common guidance algorithm. The architecture is utilized to conduct Monte Carlo simulation studies of Discovery-class and SmallSat-class aerocapture missions at various planetary destinations.</p>

Aircraft design is an act of art requiring dedication and careful work to ensure good results. An essential tool in that work is a flight mechanics simulator. Such simulators are often built up of modules/models that are executed in a sequential order in each time iteration. This project aims to analyze potential improvements to the model execution order based on the dependency structure of one such simulator. The analysis method Design Structure Matrix (DSM), was used to define/map the dependencies and then Binary Linear Programming (BLP) was utilized to find five new potentially improved model orders to minimize the number of feedbacks from one iteration to the next one. Those five proposed execution orders were next compared and evaluated. The result is a model order that reduce the number of models receiving feedbacks from the previous iteration from 13 to 6, with insignificant changes in the precision of the simulator. / Vid flygplanskonstruktion krävs hårt och noggrant arbete för att säkerställa gott resultat. Ett oumbärligt verktyg är då en flygmekanisk simulator. Den typen av simulatorer är ofta uppbyggda av moduler/modeller som exekveras i en bestämd sekventiellt ordning i varje tidsteg. Syftet med detta projekt är att undersöka möjliga förbättringar av exekverings ordningen av de olika modellerna i en existerande simulator, baserat på beroendestrukturen. Analysmetoden Design Structure Matrix (DSM) användes för att bestämma beroendestrukturen och sedan utnyttjades Binär Linjär Programmering (BLP) för att hitta fem förbättrade modellordningar med avseende på att minimera antalet modeller som erhåller indata från föregående tidsiteration. De fem förbättringsförslagen jämfördes och utvärderades. Resultatet är en modellordning som kan minska antalet återkopplande modeller från 13 till 6, med insignifikanta skillnader i precisionen av simulatorn.