Browsing by Author "Gobin, Bradley Scott"

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    Exploration and Development of Electrically Controllable Gel and Solid Propellants
    Gobin, Bradley Scott (Virginia Tech, 2023-05-26)
    Electrically controllable propellants (ECPs) provide a new method to increase the control and functionality of rocket motors in particular solid rockets. Traditional solid rockets do not have the capability to modify the burning rate on demand during operation, which greatly limits operational capabilities. The research outlined in this dissertation explores the fundamentals in the creation of ECPs to enable increased control in the burning rate of solid rockets. The research is organized into four studies which step through the fundamentals of ECPs, starting with a focus on the solid oxidizers, then moving into the creation of electrically controllable gel propellants (ECGPs). Next, electrically controllable solid propellants (ECSPs) were explored under atmospheric conditions, and then finally under elevated pressures. The first study explores the ability to electrically control the decomposition characteristics of various solid oxidizers. Typical composite solid propellants are composed of solid fuels and oxidizers and isolating the oxidizer in this study enables the ability to characterize critical components of ECSPs individually. This study discovered that certain solid oxidizers respond differently to applied voltages, but generally the decomposition rate of the solid oxidizers is greatly increased when voltage is applied using metal electrodes. The melt layer formed in the decomposition of the solid oxidizers was observed to be critical in the ability to manipulate the decomposition rate of the oxidizers. The second study built upon the knowledge that the melt layer was critical in the functionality of ECPs and explored the utilization of ECGPs which combined a viscous liquid polymer fuel in which solid oxidizers were dissolved. The ECGPs used in this study readily decomposed and ignited when a voltage potential was applied. The composition of the ECGPs along with the magnitude of the voltage being applied greatly impacted the ignition delay and overall burning characteristics of the propellants. This study illustrated the potential to create ECPs that enable increased control over the burning characteristics compared to conventional propellants. The third study utilized a solid polymer binder along with the solid oxidizers to create ECSPs that would readily decompose and ignite when a voltage potential was applied. Compositional changes in the propellant along with the magnitude of the applied voltage potential were observed to impact the regression rate of the ECSPs utilized in this study. The electrochemical decomposition characteristics of the ECSPs were explored to better characterize the contribution of the electrochemical reactions and how they differ from the more conventional thermochemical decomposition. The fourth and final study builds upon the prior ECSP study, but now experiments utilize compositions with electrically conductive additives to increase the responsiveness of the ECSPs to the applied voltage. This enabled the creation of ECSPs which ignite much more readily and with a higher degree of consistency. Experiments were also conducted at elevated pressures to analyze the combined impact that voltage and pressure play on the regression rate of the ECSPs.
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    Quantitative Approach and Departure Risk  Assessment for Unmanned Aerial Systems
    Gobin, Bradley Scott (Virginia Tech, 2020-10-26)
    The usage of unmanned aerial systems (UAS), also called drones, has grown at an increasing rate, with expectations of the number of unmanned aircraft (UA) to triple between 2019 and 2023 as commercial and government usage of UAS increases as per the Federal Aviation Administration. As the usage of UA increases, the probability of a UA crash resulting in injuries of 3rd parties on the ground also increases. The goal of this research was to create a method and software tool that gives the user an accurate representation of the risk to 3rd parties on the ground associated with a given flight plan. The main area of focus was on large rotorcraft and fixed-wing aircraft that are used by the military and that have the potential to do large amounts of damage if a crash were to occur. How unique types of failures affect the ground area at risk and the UA crash characteristics and how these characteristics affect population on the ground were all considered. With this information, a probability of fatality value is calculated, which helps the user determine if the mission risk is acceptable. The ability to optimize this flight path to find the lowest risk flight path is also possible, based upon user specifications.