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Nanosatellites, such as Cubesats, are a rapidly growing sector of the space industry. Their popularity stems from their low development cost, short development cycle, and the widespread availability of COTS subsystems. Budget-conscious spacecraft designers are working to expand the range of missions that can be accomplished with nanosatellites, and a key area of development fueling this expansion is the creation of micropropulsion systems. One such system, originally developed at the Australian National University (ANU), is an electrothermal plasma thruster known as Pocket Rocket (PR). This device heats neutral propellant gas by exposing it to a Capacitively Coupled Plasma (CCP), then expels the heated gas to produce thrust. Significant work has gone towards understanding how PR creates and sustains a plasma and how this plasma heats the neutral gas. However, no research has been published on varying in the device's geometry. This thesis aims to observe how the size of the RF electrode affects PR operation, and to determine if it can be adjusted to improve performance. To this end, a thruster has been built which allows the geometry of the RF electrode to be easily varied. Measurements of the plasma density at the exit of this thruster with different sizes of electrode were then used to validate a Computational Fluid Dynamics (CFD) model capable of approximately reproducing experimental measurements from both this study and from the ANU team. From this CFD, the number of argon ions in the thruster was found for each geometry, since collisions between argon ions and neutrals are primarily responsible for the heating observed in the thruster. A geometry using a 10.5 mm electrode was observed to produce a 23% increase in the quantity of ions produced compared to the baseline 5 mm electrode size, and a 3.5 mm electrode appears to produce 88% more ions.

<div>A 7° half-angle cone with a highly-swept fin was tested in the Boeing/AFOSR Mach-6 Quiet Tunnel at 0.0° angle of attack. Previous measurements of the surface heat transfer using temperature sensitive paint revealed heating streaks on the cone surface related to streamwise vortices generated by the fin shock. High-frequency measurements of the cone-surface pressure fluctuations revealed that transition occurs in the streak region at sufficiently-high freestream unit Reynolds numbers under quiet flow. In this work, high-resolution measurements of the surface heat transfer are obtained using infrared thermography and a polyether-ether-ketone wind-tunnel model. In addition, a novel model design made it possible to measure pressure fluctuations throughout the streak region on the cone surface.</div><div><br></div><div>A slender cone with a sharp nosetip and a fin swept back 75° with a 3.18 mm leading-edge radius served as the primary geometry for this work. Two laminar heating streaks</div><div>were measured on the cone surface. These travel along a line of nearly-constant azimuth. A hot spot develops in the streak farthest from the fin, which then moves upstream with increasing freestream Reynolds number. Downstream of this hot spot, the streaks begin to spread in azimuth. The heat transfer along the outer streak shows a threefold increase near the hot spot before decreasing back to nearly two times the laminar streak heating. The amplitude of the pressure fluctuations increases simultaneously with the heat transfer, reaching a peak of nearly 9% of the Taylor-Maccoll pressure for a 7° straight cone. Power spectral densities calculated from these fluctuations demonstrate spectral broadening, which is indicative of boundary-layer transition. Using surface-pressure-fluctuation and heat-flux measurements, transition onset was estimated to occur at an axial length Reynolds number of 2.2×10⁶. Pressure sensors that were rotated through the streak region showed that multiple instabilities amplify between the heating streaks, upstream of the transition onset location. Downstream of transition onset, the highest-amplitude instabilities are localized to the hot spot in the outer streak. The effect of freestream noise on transition was also investigated with this geometry. Under conventional noise levels, transition onset was estimated to occur at an axial length Reynolds number of 0.93×10⁶, and only one instability was measured in the streak region with a frequency similar to the second-mode instability.</div><div><br></div><div>Four configurations were tested to investigate the effect of fin sweep and nosetip bluntness under quiet flow. Fins with 70° and 75° sweep were each tested with nominally sharp and 1-mm-radius nosetips. Increasing fin sweep was shown to move the heating streaks on the cone closer to the fin and to decrease the peak-to-peak spacing of the streaks. In addition, transition onset occurred at lower freestream unit Reynolds numbers for the 70° sweep case. Increasing nosetip radius had little effect on the heating streaks, other than to delay the transition location. A blunt nosetip was shown to delay transition more for the 75° sweep fin as compared to the 70° fin. Similar instabilities were measured for all four of the configurations in this work. The frequency of the instabilities appears to be correlated with the peak-to-peak distance of the heating streaks, which can be viewed as an indirect measurement of the vortex diameter.</div><div><br></div><div>Lastly, the first quantitative measurements of heat transfer on the fin were made using the infrared thermography apparatus. Peak heating on the fin, not including the leading edge, is lower than peak heating rates on the cone. One broad heating streak was measured close to the corner, and smaller low-heating streaks were measured farther outboard. The heating within the streak closest to the corner was shown to agree well with a fully-laminar computed basic state, indicating that the flow on the fin is laminar up to at least 6.31×10⁶ m⁻¹. Using miniaturized Kulite sensors, pressure fluctuations were measured at twelve locations on the fin surface. No obvious conclusions could be drawn from these Kulite measurements, and there is no clear indication that transition occurs on the fin within the maximum quiet</div><div>freestream conditions.</div>

In order to accurately conduct the preliminary and detailed design of solar powered Unmanned Aerial Systems (UAS), it is necessary to have a thorough understanding of the systems involved. In particular, it is desirable to have mathematical models and analysis tools describing the energy income and expenditure of the vehicle. Solar energy income models may include available solar irradiance, photovoltaic array power output, and maximum power point tracker efficiency. Energy expenditure models include battery charging and discharging characteristics, propulsion system efficiency, and aerodynamic efficiency. In this thesis, a series of mathematical models were developed that characterize the performance of these systems. Several of these models were then validated against test data. Testing was conducted on specific components used by a solar UAS designed and built by students at the California Polytechnic State University, San Luis Obispo, which completed a six-hour flight relying only on solar energy in May 2019. Results indicate that, while some models accurately predicted test outcomes, others still need further improvement. While these models may be useful during the preliminary and detailed design phases of a solar powered UAS, specific component testing should be conducted to converge on the most desired design solution.

This work deals with development of propulsion for ultralight plane with using fuel cells technology. This thesis is described different types of fuel cells, fuels, electric motors and other component parts needed to build a functioning drive as a whole. The thesis also described situation in the market of fuel cell technology, production facilities and hydrogen tanks. Work includes part of the design drawings of the proposed solutions of thesis.

This thesis deals with the design of an underwater scooter, which is meant to be used by group of divers. That should be helped by a system of electromagnetic devices, through which could be smaller scooters and other equipment connected with a greater machine. The work is approached more as a design and ergonomics solution, while the construction is associated with conceptual level.

The theoretical part deals with the basic division of industrial robots, their structure and working space. It analyzes propulsion using the industrial robots and sensors required to operate in the robot. The practical part describes the design of a mechanical arm for an industrial robot manipulator. The practical part also includes a description of the sensor and a description of the control unit.

<div>A new class of bladeless turbines was developed which allows for power extraction from harsh environments with minimal maintenance cost. This is achieved through a wavy hub surface that promotes shocks and expansion fans and hence generates torque besides trust if used as bottoming or topping cycle. </div><div>A numerical procedure to design, mesh, and model this new expansion device through steady and unsteady Reynolds Averaged Navier Stokes simulations is outlined. Then, the full three-dimensional flow field is replicated using a two-dimensional geometry to enable a simpler test section with full optical access at the Purdue Experimental Turbine Aerothermal Lab. Pressure, heat flux, and skin friction are computed via several measurement techniques to provide an accurate estimation of the uncertainties on the power, efficiency, and heat flux of the bladeless turbine. High-frequency pressure sensors (160 kHz) along with a high-frequency heat flux sensor (atomic layer thermopile) are used to characterize the unsteady phenomena on the hub and the shroud. Unsteadiness in the flow field is assessed through 10 kHz shadowgraph, density gradients are quantitatively assessed via 3 kHz Background Oriented Schlieren, and unsteady velocity components and flow angles are characterized with 1 kHz Femtosecond Laser Electronic Excitation Tagging. A reduced order model is constructed with Spectral Proper Orthogonal Decomposition to retrieve the dominant frequencies in the flow field, which could be associated with a multitude of shock-boundary layer, shock-shock, and shock-shear layer interactions.</div><div>A parametric study and multi-objective optimization to maximize power extraction while minimizing pressure loss and heat flux are performed. The operational envelope and scaling of the bladeless turbine are described for several reduced mass flows, reduced speeds, and swirl angles. Based on all the gathered simulations, a guideline for the design of bladeless turbines is provided.</div><div><br></div><div>Finally, the operation of the bladeless turbine is analyzed considering the unsteady propagation of a rotating oblique shock throughout the passage. Non-dimensional parameters to generically describe rotating shocks are discussed, and their influence on the operation of the turbine is assessed. Correction terms for the power and pressure loss during the unsteady operation of the bladeless turbine are developed with results of this section.</div><div><br></div>

<div>Wind-tunnel experiments with a sharp 7-degree half-angle cone and a 33% scale Boundary Layer Transition (BOLT) model were performed in the Boeing/AFOSR Mach 6 Quiet Tunnel to investigate the effects of forward- and backward-facing steps on boundary-layer instability and transition. Each model was modified to include intentional steps just downstream of the nosetip. Experiments were performed at different freestream Reynolds numbers and varying step sizes. Infrared thermography was used to calculate surface heat transfer, and high-frequency pressure sensors were used to measure pressure fluctuations. A replica measurement technique was used to accurately measure step heights on the BOLT flight vehicle and the wind tunnel model.</div><div><br></div><div>A 7-degree half-angle cone was tested at 0-degree and 6-degree angles of attack. Step heights ranged from 0.610 mm to 1.219 mm. At a 0-degree angle of attack, no significant increases in heat transfer were observed with any of the forward- or backward-facing steps. However, a 250 kHz instability was measured with the forward-facing steps. Growth of the instability was similar to a second-mode. At a 6-degree angle of attack, an increase in heat transfer was observed on the windward ray with the forward-facing steps. Sharp increases in heating rates and increased pressure fluctuations were indications of boundary-layer transition. Elevated heating rates and pressure fluctuations were not measured with the backward-facing steps.</div><div><br></div><div>The BOLT model was tested at 0-degree, 2-degree, and 4-degree angles of attack and 2-degree and 4-degree yaw angles. Step heights ranged from 0.076 mm to 1.016 mm. At a 0-degree angle of attack and 0-degree yaw angle, thin wedges of heating were observed with the backward-facing steps. Instabilities were measured near these wedges of heating and are thought to be caused by a secondary instability. The effects of the steps were magnified on the windward side of the BOLT model at angles of attack. Wedges of heating were wider and more intense. At higher angles of attack, the onset of heating was further upstream. Sensors near and directly underneath the wedges of heating measured pressure fluctuations that were indicative of a turbulent flow. Wedges of heating were also observed at a 4-degree yaw angle, but only with the 1.016 mm backward-facing step.</div>

The focus of this work is to design and construct a version of the secondary propulsion units used on US Navy submarines for the Virginia Tech 690 autonomous underwater vehicle. These units were used to demonstrate a control system developed in a separate study which allowed the vehicle to autonomously perform advance maneuvers such as course-keeping, mooring and obstacle avoidance. The study of the miniaturized thrusters prompted an in-depth look into two thruster designs. The first was a retractable rimdriven propeller design which was found to be too power inefficient for implementation. The final design was an azimuthing ducted propeller capable of vectoring thrust 360 degrees. Two body sections containing an implementation of the ducted propeller design were constructed and mounted to the 690 vehicle. Tests were successfully conducted in a pool. / Master of Science