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Daniel Guggenheim School of Aerospace Engineering
Daniel Guggenheim School of Aerospace Engineering
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ItemA parametric and physics-based approach to structural weight estimation of the hybrid wing body aircraft(Georgia Institute of Technology, 2012-08-28) Laughlin, Trevor WilliamEstimating the structural weight of a Hybrid Wing Body (HWB) aircraft during conceptual design has proven to be a significant challenge due to its unconventional configuration. Aircraft structural weight estimation is critical during the early phases of design because inaccurate estimations could result in costly design changes or jeopardize the mission requirements and thus degrade the concept's overall viability. The tools and methods typically employed for this task are inadequate since they are derived from historical data generated by decades of tube-and-wing style construction. In addition to the limited applicability of these empirical models, the conceptual design phase requires that any new tools and methods be flexible enough to enable design space exploration without consuming a significant amount of time and computational resources. This thesis addresses these challenges by developing a parametric and physics-based modeling and simulation (M&S) environment for the purpose of HWB structural weight estimation. The tools in the M&S environment are selected based on their ability to represent the unique HWB geometry and model the physical phenomena present in the centerbody section. The new M&S environment is used to identify key design parameters that significantly contribute to the variability of the HWB centerbody structural weight and also used to generate surrogate models. These surrogate models can augment traditional aircraft sizing routines and provide improved structural weight estimations.
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ItemA simulation framework for the analysis of reusable launch vehicle operations and maintenance(Georgia Institute of Technology, 2012-07-26) Dees, Patrick DanielDuring development of a complex system, feasibility initially overshadows other concerns, in some cases leading to a design which may not be viable long-term. In particular for the case of Reusable Launch Vehicles, Operations&Maintenance comprises the majority of the vehicle's LCC, whose stochastic nature precludes direct analysis. Through the use of simulation, probabilistic methods can however provide estimates on the economic behavior of such a system as it evolves over time. Here the problem of operations optimization is examined through the use of discrete event simulation. The resulting tool built from the lessons learned in the literature review simulates a RLV or fleet of vehicles undergoing maintenance and the maintenance sites it/they visit as the campaign evolves over a period of time. The goal of this work is to develop a method for uncovering an optimal operations scheme by investigating the effect of maintenance technician skillset distributions on important metrics such as the achievable annual flight rate and maintenance man hours spent on each vehicle per flight. Using these metrics, the availability of technicians for each subsystem is optimized to levels which produce the greatest revenue from flights and minimum expenditure from maintenance.
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ItemAutonomous Hopping Rotochute(Georgia Institute of Technology, 2011-04-05) Aksaray, DeryaThe Hopping Rotochute is a promising micro vehicle with the capability of exploring rough and complex terrains with minimum energy consumption. While it is able to fly over obstacles via thrust produced by its coaxial rotor, its physical architecture, inspired from a "Weebles Wooble," provides re-orientation wherever it hits the ground. Therefore, this aerial and ground vehicle represents a potential hybrid vehicle capable of reconnaissance and surveillance missions in complex environments. The most recent version of the Hopping Rotochute is manually controlled to follow a trajectory. The control commands, listed in a file prior to the particular mission, are executed exactly as defined, like a "batch job," regardless of the uncertain external events. This control scheme is likely to cause great deviations from the route. Consequently, the vehicle may finish the mission very far away from the desired end point. However, if a vehicle is capable of receiving the control commands during a mission, "interactive processing" can be realized and efficient path tracking would be achieved. Hence, the development of the Hopping Rotochute that follows a trajectory autonomously reveals the foundation of this thesis. Two control approaches inspired the proposed methodology for developing an autonomous trajectory-following algorithm. The first approach is rule-based control that enables decision making through conditional statements. In this thesis, rule-based control is used to select a target point for a particular hop based on the existence of an obstacle and/or wind in the environment. The second approach is model predictive control employed to predict future outputs from hop performance models. In other words, this technique approaches the problem by providing intelligence pertaining to how a particular hop will end up before being attempted. Hence, the optimum control commands are selected based on the predicted performance of a particular hop. This research demonstrates that the autonomous Hopping Rotochute can be realized by rule-based control embedded with some performance models. In the assumption of known boundaries such as wall and ceiling information, this study has two aims: (1) to avoid obstacles by creating a smaller operational volume inside the real boundaries so that the vehicle is restricted from exiting the operational volume and no violation occurs within the real boundaries; (2) to estimate the wind by previous hops to select the next hopping point with respect to the estimated wind information. Based on the developed methodology, simulations are conducted for four different scenarios in the existence of obstacles and/or wind, and the results of the simulations are analyzed. Finally, based on the statistics of simulation results, the effectiveness of the proposed methodology is discussed.
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ItemUH-1 corrosion monitoring(Georgia Institute of Technology, 2010-11-19) Kersten, Stephanie M.As the UH-1 aircraft continue to age, there is growing concern for their structural integrity. With corrosion damage becoming a bigger part of the sustainment picture with increasing maintenance burden and cost, it is becoming increasingly important for corrosion management to be updated with more advanced techniques. The current find-and-fix technique for handling corrosion has many shortfalls, spurring the recent interest in early detection through structural health monitoring. This condition based technique is becoming more prevalent and is recognized for the potential to greatly reduce maintenance cost. Through corrosion monitoring, structural and environmental conditions can be closely observed, preventing excessive maintenance action and saving cost. Searches for corrosion monitoring system designs revealed several commercial companies with prototype systems installed on commercial aircraft, however, details on system design and data analysis were scarce. This study attempted to bridge the gap in literature by providing insight into the development of a corrosion damage prediction model and the design of a corrosion monitoring system. This study attempted to use aircraft maintenance data to make prediction models for determining what corrosion damage an aircraft can expect, given varying operating conditions. Although a reliable prediction model could not be created, trends observed in the data were still valuable for identifying problematic areas of the aircraft. In order to create reliable models, more accurate corrosion data is needed. This can be accomplished through the implementation of a corrosion monitoring system. A custom corrosion monitoring system was designed for the UH-1 aircraft. Commercial off-the-shelf products were fit to the design and a benefits-to-cost analysis was performed for the monitoring system, evaluating the system based on criteria developed from user requirements. The system proved to meet and exceed expectation, making it an ideal choice for the UH-1 aircraft.
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ItemDynamic cutback optimization(Georgia Institute of Technology, 2010-04-15) Jayaraman, ShankarThe focus of this thesis is to develop and evaluate a cutback noise minimization process - also known as dynamic cutback optimization - that considers engine spool down during thrust cutback and is consistent with ICAO and FAR Part 36 noise certification procedures. Simplified methods for flyover EPNL prediction used by propulsion designers assume instantaneous thrust reduction and do not take into account the spooling down of the engine during the cutback procedure. The thesis investigates if there is an additional noise benefit that can be gained by modeling the engine spool down behavior. This in turn would improve the margin between predicted EPNL and Stage 4 noise regulations. Modeling dynamic cutback also impacts engine design during the preliminary and detailed design stages. Reduced noise levels due to cutback may be traded for lower engine fan diameter, which in turn reduces weight, fuel burn, and cost.