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High aspect-ratio flying wing configurations designed for high altitude, long endurance missions are characterized by high flexibility, leading to significant static aeroelastic deformation in flight, and coupling between aeroelasticity and flight dynamics. As a result of this coupling, an integrated model of the aeroelasticity and flight dynamics has to be used to accurately model the dynamics of the flexible flying wing. Such an integrated model of the flight dynamics and the aeroelasticity developed by Patil and Hodges is reviewed in this dissertation and is used for studying the unique flight dynamics of high aspect-ratio flexible flying wings. It was found that a rigid body configuration that accounted for the static aeroelastic deformation at trim captured the predominant flight dynamic characteristics shown by the flexible flying wing. Moreover, this rigid body configuration was found to predict the onset of dynamic instability in the flight dynamics seen in the integrated model. Using the concept of the mean axis, a six degree-of-freedom reduced order model of the flight dynamics is constructed that minimizes the coupling between rigid body modes and structural dynamics while accounting for the nonlinear static aeroelastic deformation of the flying wing. Multi-step nonlinear dynamic inversion applied to this reduced order model is coupled with a nonlinear guidance law to design a flight controller for path following. The controls computed by this flight controller are used as inputs to a time-marching simulation of the integrated model of aeroelasticity and flight dynamics. Simulation results presented in this dissertation show that the controller is able to successfully follow both straight line and curved ground paths while maintaining the desired altitude. The controller is also shown to be able to handle an abrupt change in payload mass while path-following. Finally, the equations of motion of the integrated model were non-dimensionalized to identify aeroelastic parameters for optimization and design of high aspect-ratio flying wings. / Ph. D.

Clusters of low-performance spacecraft flying in formation may provide enhanced performance over single high-performance spacecraft. This is especially true for remote sensing missions where interferometry or stereographic imaging may provide higher resolution data. The configurations of such formations vary during an orbit due to orbital dynamics, and over longer time scales due to perturbations. Selection of a configuration should be based on overall performance of the formation. In this thesis, performance measures are developed and evaluated based on integration over one orbit. The measures involve the angular separation of spacecraft, the distance between spacecraft, and an area-based measure of the separation of the spacecraft. Numerical techniques are employed to evaluate the performance measures to determine optimal scenarios for two formations. Simplifying assumptions are made to allow a closed-form analytic solution and the results are compared to those obtained numerically. Finally, the sensitivity of the measures to linearized propagation techniques is investigated. / Master of Science

This dissertation addresses the question, how and why do 'flying' snakes (Chrysopelea) undulate through the air? Instead of deploying paired wings or wing-like surfaces, flying snakes jump, splay their ribs into a bluff-body airfoil, and undulate through the air. Aerial undulation is the dominant feature of snake flight, but its effects on locomotor performance and stability are unknown. Chapter 2 describes a new non-equilibrium framework to analyze gliding animals and how the pitch angle affects their translational motion. Chapter 3 combines flying snake glide experiments and detailed dynamic modeling to address what is aerial undulation and how each kinematic component affects rotational stability and translational performance. Chapter 4 combines the kinematic data of Chapter 3, with elements of the non-equilibrium framework of Chapter 2, to examine the kinematics of snake flight in greater detail. This chapter also tests if our current understanding of flying snake aerodynamics is sufficient to explain the observed center of mass motion. / Ph. D.

The genus Chrysopelea encompasses the "flying" snakes. This taxon has the ability to glide via lateral aerial undulation and dorsoventral body flattening, a skill unique to this group, but in addition to other functions common to all colubrids. The skin must be extensible enough to allow this body shape alteration and undulation, and strong enough to withstand the forces seen during landing. For this reason, characterizing the mechanical properties of the skin may give insight to the functional capabilities of the skin during these gliding and landing behaviors. Dynamic and viscoelastic uniaxial tensile tests were combined with a modified particle image velocimetry technique to provide strength, extensibility, strain energy, and stiffness information about the skin with respect to orientation, region, and species, along with viscoelastic parameters. Results compared with two other species in this study and a broader range of species in prior studies indicate that while the skin of these unique snakes may not be specifically specialized to deal with larger forces, extensibility, or energy storage and release, the skin does have increased strength and energy storage associated with higher strain rates. The skin also has differing properties with respect to dorsoventral location, and regional differences in strength in the circumferential orientation. This may indicate that, although the properties of the skin may not be different, the rate at which the skin is strained in the different species may vary, thus altering the apparent properties of the skin during specific behaviors. / Master of Science

This thesis analyzes the presence and progression of the Flying African Myth in Canada— a myth which originally reflected the desires for escape and cross-Atlantic return shared by generations of Black slaves throughout the Americas. While related West African themes of spirit flight and human transformation do suggest a historic relationship, it was only in the New World that human powers of flight emerged. Thus, a new mythology sprung from the desires to transcend the bonds of slavery and return to an African home. However, despite being well documented as Pan-American, this myth has gone largely uninvestigated in its Canadian context thus far— an omission which follows an extensive pattern of Black cultural erasure in Canada as well as the exclusion of Canada in much Black diasporic scholarship. These absences lead to my exploration of the unique circumstances in Canada that continue to influence this myth, including the constant "struggle against erasure" and the “fragile coalition of identities” that constitute the Black diaspora in Canada, as well as federal legislation that protects the nation’s self-image as a multicultural “mosaic.” I argue not only that the myth exists more extensively in Canadian oral and written literatures than may be expected, but that the myth may be alternately interpreted as a method of preserving Canadian national roots as well as navigating Black diasporic routes. I suggest that these two opposing functions of the myth, to pronounce both fixity and fluidity, reflect the tendencies of critics George Elliott Clarke and Rinaldo Walcott to articulate differing approaches to Black identity and culture in Canada. This thesis also embraces the aims set forth in Paul Gilroy’s The Black Atlantic: Modernity and Double-Consciousness, demonstrating how the image of human flight further challenges the oppressive ideologies of Western modernity as well as reimagines the possibilities and implications of the Black diaspora. Indeed, the myth has literally contributed to the formation of the Black diaspora in that it is a cultural artefact shared throughout the Americas and associated with the desire for African return. But the myth also offers a means by which to reconceptualise the structure of the Black diaspora. That is, as the medium of flight, the sky offers an alternative, though equally flexible and more ubiquitous, space for locating the Black diaspora beyond the Atlantic basin. Moreover, the notions of impossibility, immateriality, and imagination which are embraced by this myth circumvent Gilroy’s implicit affirmation of individualism, rationalism, physical mobility, as well as static and bounded geographic space— elements which compromise his productive critique of nationalisms, ethnic essentialisms, and particularly of modernity.

Indiana University-Purdue University (IUPUI)

To prevent climate change, the world needs to reduce carbon emissions globally. This also applies to academia, where a large portion of a research-intensive organization’s total emissions comes from flying. At KTH, a research-intensive organization, an ambitious university-wide goal to reduce emissions from academic flying has been established. The mid-level structure in the organization, a division, functions as a boundary between the individual employee and the larger organization, and has been identified as a promising target to address the organizational goals. In this study a tool for heads of divisions to budget and follow-up a speculative carbon budget on their division is explored through a design process. It was found that a tool for heads of division to manage carbon emissions at their division needs to involve the employees in the process, be effortless in terms of prioritization of trips and provide a good overview for decision making. The most prominent finding, and the requirement for such a tool to be implemented, is clearer directives and communication from the top-level of the organization. / För att förebygga klimatförändringar behöver världen minska koldioxidutsläppen globalt. Detta gäller även akademin, där en stor del av forskningsintensiv-organisationers totala utsläpp kommer från flyg. På KTH, som är en forskningsintensivorganisation, har ambitiösa organisatoriska mål fastställts för att minska utsläppen från akademiskt flyg. Inom organisationen fungerar avdelningar som en förbindelse mellan den enskilde medarbetaren och den större organisationen, och har identifierats som en lämplig del av organisationen att agera på de organisatoriska målen. I denna studie utvecklas ett verktyg som ska hjälpa avdelningschefer att budgetera och följa upp en spekulativ koldioxidbudget på sin avdelning, detta utforskas genom en designprocess. Det uppmärksammades att ett sådant verktyg behöver involvera medarbetarna i processen, vara enkelt när det gäller prioritering av resor och ge en bra överblick för att kunna ta beslut. Den mest framträdande upptäckten, som också är ett krav för att ett sådant verktyg ska kunna implementeras, är tydligare direktiv och kommunikation från organisationens ledningsnivå.

Effects of engine placement on flutter characteristics of a very flexible high-aspect-ratio wing are investigated using the code NATASHA (Nonlinear Aeroelastic Trim And Stability of HALE Aircraft). The analysis was validated against published results for divergence and flutter of swept wings and found to be in excellent agreement with the experimental results of the classical wing of Goland. Moreover, modal frequencies and damping obtained for the Goland wing were found in excellent agreement with published results based on a new continuum-based unsteady aerodynamic formulation. Gravity for this class of wings plays an important role in flutter characteristics. In the absence of aerodynamic and gravitational forces and without an engine, the kinetic energy of the first two modes are calculated. Maximum and minimum flutter speed locations coincide with the area of minimum and maximum kinetic energy of the second bending and torsion modes. Time-dependent dynamic behavior of a turboshaft engine (JetCat SP5) is simulated with a transient engine model and the nonlinear aeroelastic response of the wing to the engine's time-dependent thrust and dynamic excitation is presented. Below the flutter speed, at the wing tip and behind the elastic axis, the impulse engine excitation leads to a stable limit cycle oscillation; and for the ramp kind of excitation, beyond the flutter speed, at 75% span, behind the elastic axis, it produces chaotic oscillation of the wing. Both the excitations above the flutter speed are stabilized, on the inboard portion of the wing. Effects of engine placement and sweep on flutter characteristics of a backswept flying wing resembling the Horten IV are explored using NATASHA. This aircraft exhibits a non-oscillatory yawing instability, expected in aircraft with neither a vertical tail nor yaw control. More important, however, is the presence of a low frequency “body-freedom flutter” mode. The aircraft center of gravity was held fixed during the study, which allowed aircraft controls to trim similarly for each engine location, and minimized flutter speed variations along the inboard span. Maximum flutter speed occurred for engine placement just outboard of 60% span with engine center of gravity forward of the elastic axis. The body-freedom flutter mode was largely unaffected by the engine placement except for cases in which the engine is placed at the wing tip and near the elastic axis. In the absence of engines, aerodynamics, and gravity, a region of minimum kinetic energy density for the first symmetric free-free bending mode is also near the 60% span. A possible relationship between the favorable flutter characteristics obtained by placing the engines at that point and the region of minimum kinetic energy is briefly explored. Effects of multiple engine placement on a similar type of aircraft are studied. The results showed that multiple engine placement increases flutter speed particularly when the engines are placed in the outboard portion of the wing (60% to 70% span), forward of the elastic axis, while the lift to drag ratio is affected negligibly. The behavior of the sub- and supercritical eigenvalues is studied for two cases of engine placement. NATASHA captures a hump body-freedom flutter with low frequency for the clean wing case, which disappears as the engines are placed on the wings. In neither case is there any apparent coalescence between the unstable modes. NATASHA captures other non-oscillatory unstable roots with very small amplitude, apparently originating with flight dynamics. For the clean-wing case, in the absence of aerodynamic and gravitational forces, the regions of minimum kinetic energy density for the first and third bending modes are located around 60% span. For the second mode, this kinetic energy density has local minima around the 20% and 80% span. The regions of minimum kinetic energy of these modes are in agreement with calculations that show a noticeable increase in flutter speed at these regions if engines are placed forward of the elastic axis. High Altitude, Long Endurance (HALE) aircraft can achieve sustained, uninterrupted flight time if they use solar power. Wing morphing of solar powered HALE aircraft can significantly increase solar energy absorbency. An example of the kind of morphing considered in this thesis requires the wings to fold so as to orient a solar panel to be hit more directly by the sun's rays at specific times of the day. In this study solar powered HALE flying wing aircraft are modeled with three beams with lockable hinge connections. Such aircraft are shown to be capable of morphing passively, following the sun by means of aerodynamic forces and engine thrusts. The analysis underlying NATASHA was extended to include the ability to simulate morphing of the aircraft into a “Z” configuration. Because of the “long endurance” feature of HALE aircraft, such morphing needs to be done without relying on actuators and at as near zero energy cost as possible. The emphasis of this study is to substantially demonstrate the processes required to passively morph a flying wing into a Z-shaped configuration and back again.

This research programme explores, theoretically and experimentally, a new liftsystem for Vertical/Short Take-off and Landing (V/STOL) Aircraft. It is based upon an annular wing wrapped around a centrifugal flow generator, potentially creating a vehicle with no external moving parts, reduced vehicle aerodynamic losses compared to previous V/STOL technologies and substantially eliminating induced drag. It is shown that such a wing works best with a thick aerofoil section, and appears to offer greatest potential at a micro-aerial vehicle scale with regard to fundamental performance parameter “lift to weight ratio”. Certain efficiency losses are encountered mainly occurring from annular flow expansion and problems with achieving acceptable blower slot heights. Experimental methods are described along with results, and a comparison shows that the experimental values remain below theoretical values, partly due to flow asymmetry but possibly also other factors. Symmetrical blowing, as initially hypothesised, was found to be impracticable; this suggested use of pure upper surface blowing with Coanda effect. The modified approach was further explored and proved viable. The ultimate goal of this work was to develop an understanding and the facility to integrate the annular-wing into a vehicle to achieve controlled powered flight. To serve the purpose, issues encountered on current and past V/STOL aircraft are being investigated to set a path for further research/development and to validate/justify the design of future V/STOL aircraft. Also, presented is a feasibility study where different physical scales and propulsion systems are considered, and a turbofan has shown to achieve the best performance in terms of Range and Endurance. This privilege allows one to accurately study the V/STOL technologies around.