This report covers the basic approach to creating a new multirotor design. All the way from creating a concept, through design requirements and finally evaluation. Both control algorithms and system design is covered. The main problem solved is that of the danger of naked propellers used on most multirotor drones and how to make them safer and easier to fly in populated areas.

The degree project we were assigned consists of designing an environment-friendly Unmanned Aerial Vehicle (UAV) that can fly at least one hour. In this case the type of energy used for power system is solar energy as a clean energy.

At higher altitudes is where we on occasion observe some of the most interesting atmospheric events in the sky. Examples of such are Aurora borealis, lightning sprites, jets and noctilucent clouds. In studying these processes one can learn much about them and our atmosphere in general but studying them is not always easy. Since atmospheric events of this scale cannot possibly be replicated in a laboratory environment they must be observed when they occur in our atmosphere. The ALPHA project's purpose is to (at a reasonable cost) design and build an UAV equipped with scientific instruments including a camera suitable for low-light imaging to be able to capture these fascinating phenomena. The aircraft will have a high cruising altitude of 15 km (lower part of the stratosphere). By making observations in flight above the troposphere, the limiting factor of weather is practically eliminated as compared to making ground-based observations.  In this 15 credits project, the thermal design aspects for the components of the UAV are explored. This mainly involves ensuring that the camera, batteries, and electronics are kept at a moderate temperature during flight. Another area that is explored is potential icing and its effects on the UAV.

The current research investigates a next-generation method of combustion called detonations for propulsive applications which has support from the Combustion Services Branch at the Air Force Research Laboratory (AFRL) of the Rocket Propulsion Division. The overall initiative seeks to explore the viability of detonation-based systems to augment or replace current rocket propulsion methods in the coming five years. The present work progresses this vision by providing proof of a liquid RP-2 based Rotating Detonation Rocket Engine (RDRE) as well as the fundamentals associated with the physics involved to further the understanding of the phenomenon and its potential uses. Phase one of the research starts with development of a theoretical model based on the Zel'dovich-Neumann-Doring (ZND) detonation model and the well established D2 droplet burning model to establish a droplet sizing parameter for varying detonation wavespeeds. Phase two then documents the interaction of a millimeter droplet colliding with varying supersonic waves where the goal is to document the breakup and transient evolution of the droplet when imparted with the supersonic flow velocity. Phase three consists of characterization of an unlike-doublet impinging injector using Liquid-RP2 and Air to record the incipient spray behavior relative to varying operating conditions of interest. Phase four comprises of the aforementioned spray interacting with a fully developed detonation wave where Schlieren, CH*, Formaldehyde PLIF and Mie scatter were used to archive the reactions that ensues. Finally, phase five consists of testing a RDRE fueled with liquid RP-2 and O2 as the reactants where thrust measurements and back-end imaging analysis of the wavespeeds provide insight into the operation and sustenance of the combustion phenomenon occurring inside the engine.

Liquid jet in crossflow systems are often used as lightweight and efficient mechanisms of atomizing fuel prior to entertainment in the flame holder and combustion, making them integral components of liquid fueled engines. Unfortunately, such systems are susceptible to deviations in both trajectory and breakup rate, depending primarily on the Weber number and momentum flux ratio of the injected jet. In these studies, the effects of solid obstructions, called pintiles, on the variability of liquid jet in cross flow trajectory and breakup are investigated. Initial investigations looked at the impacts of broad geometric parameters on flow independence, using Mie scatter imaging and phase Doppler particle analysis. The results of that investigation yielded an optimal overarching geometry for pintiles. This knowledge was then refined by looking at specific face characteristics of the obstructions, primarily investigating face angle and concavity. Spray characteristics were spatially resolved using LIF/Mie particle sizing techniques, revealing that modest convex surfaces yielded the most consistent breakup characteristics across space, while simultaneously improving the average breakup distance of the liquid jet. Finally, this progression of pintile characteristics is investigated on the effects pintiles have on overarching flame properties, using C2*/CH* chemiluminescence ratios to determine spatially resolved equivalence ratio distributions across a wide range of Weber numbers and momentum flux ratios encompassing breakup regimes from the enhanced capillary modes through to shear breakup modes. Results from these studies demonstrate significant improvement of combustion properties from the introduction of the pintiles.

While landing, birds often perform a perching maneuver, which involves pitching their wings upwards while decelerating to a complete stop. By performing this perching maneuver, the birds can continue generating higher lift and drag force while slowing down, resulting in a smooth landing. The present study is motivated by the perching maneuver and aims to investigate two critical aspects of it. First, we want to explore how the proximity of the ground affects the unsteady forces and the flow field during the perching flight; and second, we want to analyze how a wing sweep influences a perching maneuver. To explore the first aspect of this dissertation, we investigated the finite flat plate undergoing a perching maneuver in the ground effect. Our results showed that the instantaneous and time-averaged lift force increased as the plate came close to the ground, while the instantaneous peak drag coefficient stayed relatively constant with changes in the ground height. However, the negative drag force, or the parasitic thrust, at the latter stages of the perching maneuver increased with the increase of the ground proximity. We found that performing rapid pitching at the end phase of the decelerating motion, which is done by introducing the time offset between the decelerating and pitch-up motion, significantly reduced the parasitic thrust even when the perching plate was in close proximity to the ground. Our results revealed that the dipole jet induced by the counter-rotating vortices was lower for the pitching case executed at the latter stage of the decelerating motion, which affected the advection of the shed vortices, acceleration of the fluid between the wing and the ground, and varied the unsteady forces during the perching maneuver. For the highest shape change number considered in this study, at a time offset of 0.5, the wing generated a positive averaged drag force and near zero averaged lift force, which is appropriate to land smoothly on the initial perching location without gaining altitude. The second aspect of this dissertation is motivated by the observation that some birds fold their wings to create a wing sweep during such perching. This study aims to find out whether such a wing sweep helps during a perching maneuver. We use two flat plates: one with a sweep and another without any sweep, and consider a deceleration maneuver where both decelerate to a complete stop from a Reynolds number, Re = 13000. We consider two cases: one, where the wings undergo only heaving, and another, where the wings perform both heaving and pitching. The latter maneuver was designed to mimic perching. By performing experiments and simulations, we compare the temporal evolution of the instantaneous forces and the vortex dynamics of both these plates. We show that during a major part of the deceleration, the instantaneous lift forces are higher in the case of the plate with sweep compared to the plate with no sweep during both kinematics. Our results indicate that the higher lift in the swept plate case was contributed by a stable leading edge vortex (LEV) which remains attached to the plate. This increase in stability was contributed by the spanwise vorticity convection caused by a distinct spanwise flow on the swept plate, as revealed by the numerical simulation. We also show that combined pitching and heaving resulted in higher force peaks, and the forces also decayed faster in this case compared to the heave-only case. Finally, by using an analytical model for unsteady flows, we prove that the higher lift characteristics of the swept plate were entirely due to higher circulatory forces. We also developed an analytical model that accounts for the variation of unsteady forces on a flat plate undergoing a perching maneuver. We model the flat plate using unsteady lifting line theory while the effect of ground height is incorporated using image vortices. We used Wagner's theory and the unsteady Kutta condition to model pitching and gradual deceleration. To include the ground effect, we updated the added mass force by accounting for the increase in flow acceleration between the wing and the ground. The model's accuracy was tested against the experimental results on a finite wing undergoing identical kinematics. Our result demonstrates that the present analytical model captures the unsteady variation of forces during a perching maneuver.

Dust problems raise significant concerns in planetary surface exploration. The unusual behavior of the dust particles that surround the vehicle after engine cutoff has the potential to have more of an influence on surface systems than the high velocity lunar rocket plume ejecta in the landing process. A prevailing hypothesis attributes the levitation and transport of dust particles on the surface of airless bodies to the electrostatic effects and electric field. However, there is no accurate model considering the inter-particle electrostatic interactions, especially when the particles are charged by plume. This dissertation aims to understand the behavior of charged lunar regolith with a discrete element method (DEM) approach focusing on the inter-particle interactions and contact charge transfer. To accomplish this, the grain dynamics is coupled with mechanical and electrical particle interactions, and both short-range and long-range interactions between particles are incorporated. A tribo-charging model based on instantaneous collisions is adopted and validated by simulation and experimental data. Sensitivity analysis is conducted to quantify the effects of initial charge, tribo-charging, and E-field on transport of lunar dust. DEM simulations are then performed for a near realistic lunar environment that show the differences of position and velocity distributions between charged particles and uncharged particles. The results indicate that the charged dust particles have higher dispersion and wider distribution of velocity due to the electrostatic effects. This provides a possible explanation for the phenomena of the approximately 30 s dust lofting following Apollo Lunar Module landing. It is shown that tribo-charging has a more considerable effect on the dynamics of charged particles with a large amount of charge, while the change of E-field does not significantly affect the results. Furthermore, superquadrics and multi-sphere approximations are introduced as two approaches to aspherical geometry to accomplish high-fidelity simulation of lunar dust in the future.

Conventional engines are limited by the efficiency of their combustion mode. Compared to present constant pressure deflagration-based engines, detonation-based systems can realize a higher thermodynamic cycle efficiency, making them an attractive candidate for next generation propulsion systems that will take humanity to hypersonic speeds and even to Mars. For all its performance gains, detonation engines are still far off from implementation. One system, the rotating detonation engine (RDE) is promising as a detonation-based engine concept for its stability, simplicity, and versatility. For these reasons, RDEs have been the subject of studies internationally in efforts to understand their operation and integration into conventional technology. RDEs are on the cusp of field use, considered at technology readiness level 5 with prototype demonstrations occurring today; however, there are still significant barriers holding back this technology from widespread adoption. The work of this dissertation confronts each of these barriers with experimental methods. Using multiple different RDE test facilities, investigations into injection, fueling, exhaust, detonability, and integration were conducted, targeting research gaps in each barrier. As a result, many novel advancements have been made from these studies such as the first demonstration of hydrogen and oxygen rotating detonations, the detonability of sustainable solid particle fuels, and the effect of fuel stratification on rotating detonation propagation. Altogether, the work presented depicts the RDE from a complete perspective by advancing current RDE research through multiple channels with the intention of advancing the technology readiness level of RDEs.

No description available.

Space- and time-resolved measurements of temperature and species mole fractions of nitrogen, oxygen, and hydrogen were obtained with a dual-pump coherent anti-Stokes Raman spectroscopy (CARS) system in hydrogen-fueled supersonic combustion free jet flows. These measurements were taken to provide time-resolved fluid properties of turbulent supersonic combustion for use in the creation and verification of computational fluid dynamic (CFD) models. CFD models of turbulent supersonic combustion flow currently facilitate the design of air- breathing supersonic combustion ramjet (scramjet) engines. Measurements were made in supersonic axi-symmetric free jets of two scales. First, the measurement system was tested in a laboratory environment using a laboratory-scale burner (∼10 mm at nozzle exit). The flow structures of the laboratory-burner were too small to be resolved with the CARS measurements volume, but the composition and temperature of the jet allowed the performance of the system to be evaluated. Subsequently, the system was tested in a burner that was approximately 6 times larger, whose length scales are better resolved by the CARS measurement volume. During both these measurements, weaknesses of the CARS system, such as sensitivity to vibrations and beam steering and inability to measure temperature or species concentrations in hydrogen fuel injection regions were identified. Solutions were then implemented in improved CARS systems. One of these improved systems is a dual-pump broadband CARS technique called, Width Increased Dual-pump Enhanced CARS (WIDECARS). The two lowest rotational energy levels of hydrogen detectable by WIDECARS are H2 S(3) and H2 S(4). The detection of these lines gives the system the capability to measure temperature and species concentrations in regions of the flow containing pure hydrogen fuel at room temperature. WIDECARS is also designed for measurements of all the major species (except water) in supersonic combustion flows fueled with hydrogen and hydrogen/ethylene mixtures (N2, O 2, H2, C2H4, CO, and CO2). This instrument can characterize supersonic combustion fueled with surrogate fuel mixtures of hydrogen and ethylene. This information can lead to a better understanding of the chemistry and performance of supersonic combustion fueled with cracked jet propulsion (JP)-type fuel.