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Space Systems Design Laboratory (SSDL)
Space Systems Design Laboratory (SSDL)
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ItemOptimal Phasing and Performance Mapping for Translunar Satellite Missions across the Earth-Moon Nodal Cycle(Georgia Institute of Technology, 2020-01-10) Hunter, Richard Anthony JohnFast, high-cadence translunar pathfinder missions hold great promise for advancing NASA's scientific observation, prospecting, and technology validation objectives through increased lunar exploration. This research applies high-performance computing to characterize direct injection lunar trajectories over a broad parameter space, and in so doing, demonstrates the viability of lunar pathfinder missions using the near-future commercial launch market. The results are intended to provide mission designers with an accurate, versatile reference for preliminary planning, including optimal departure epochs, and pertinent performance dependencies. Characterized herein are statistical distributions for the performance demands of optimally phased translunar missions, over an 18.6 year Earth-Moon nodal cycle, to a range of tailored lunar arrival architectures, for 0 – 24 kg small satellite payloads capable of supporting pathfinder objectives. This characterization is based upon a TLI stage with flight proven propulsion technology, high fidelity orbital dynamics, and direct injection flyby, orbit insertion and landing architectures compatible with both dedicated and ride share commercial launches.
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ItemDevelopment of the evolved common hardware bus (TECHBus)(Georgia Institute of Technology, 2016-07-28) Francis, ParkerThis thesis presents the design and analysis of a small spacecraft bus for use by the Georgia Tech Space Systems Design Lab. It is designed with research projects in mind, and levies the previous design work of The University of Texas at Austin's Texas Spacecraft Lab. The bus offers capabilities that are competitive to currently available commercial small spacecraft busses. The system has been designed with a variety of missions in mind, and is shown to be capable of completing several past missions that each had a customized spacecraft bus. Additional effort was placed into improving the bus' robustness and reliability to a level that has yet to be realized on CubeSats. Redundant components and software algorithms are utilized to ensure system functionality in the event of a component failure. The spacecraft bus has also been developed with the university engineering and research environment in mind. The student-built system's reliability and integrity is developed over the course of many tests, rigorous quality assurance processes, and through the use of heritage flight components. The redundancy and system integration architecture offers an unmatched 98% reliability value for one year missions; this is a 22% increase over typical single-string architectures. Each payload accommodated and each mission flown will add to the bus' heritage as approximately 95% of the spacecraft bus hardware is common between missions. For these reasons, the TECHBus is a novel system that is unique in the current CubeSat bus market, and will provide a powerful platform for space systems research and education at Georgia Tech's Space Systems Design Lab.
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ItemAnalysis of Human-System Interaction For Landing Point Redesignation(Georgia Institute of Technology, 2009-05-26) Chua, Zarrin K.Despite two decades of manned spaceflight development, the recent thrust for increased human exploration places significant demands on current technology. More information is needed in understanding how human control affects mission performance and most importantly, how to design support systems that aid in human-system collaboration. This information on the general human-system relationship is difficult to ascertain due to the limitations of human performance modeling and the breadth of human actions in a particular situation. However, cognitive performance can be modeled in limited, well-defined scenarios of human control and the resulting analysis on these models can provide preliminary information with regard to the human-system relationship. This investigation examines the critical case of lunar Landing Point Redesignation (LPR) as a case study to further knowledge of the human-system relationship and to improve the design of support systems to assist astronauts during this task. To achieve these objectives, both theoretical and experimental practices are used to develop a task execution time model and subsequently inform this model with observations of simulated astronaut behavior. The experimental results have established several major conclusions. First, the method of LPR task execution is not necessarily linear, with tasks performed in parallel or neglected entirely. Second, the time to complete the LPR task and the overall accuracy of the landing site is generally robust to environmental and scenario factors such as number of points of interest, number of identifiable terrain markers, and terrain expectancy. Lastly, the examination of the overall tradespace between the three main criteria of fuel consumption, proximity to points of interest, and safety when comparing human and analogous automated behavior illustrates that humans outperform automation in missions where safety and nearness to points of interest are the main objectives, but perform poorly when fuel is the most critical measure of performance. Improvements to the fidelity of the model can be made by transgressing from a deterministic to probablistic model and incorporating such a model into a six degree-of-freedom trajectory simulator. This paper briefly summarizes recent technological developments for manned spaceflight, reviews previous and current efforts in implementing LPR, examines the experimental setup necessary to test the LPR task modeling, discusses the significance of findings from the experiment, and also comments on the extensibility of the LPR task and experiment results to human Mars spaceflight.
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ItemComputational Fluid Dynamics Validation of a Single, Central Nozzle Supersonic Retropropulsion Configuration(Georgia Institute of Technology, 2009-05) Cordell, Christopher E., Jr.Supersonic retropropulsion provides an option that can potentially enhance drag characteristics of high mass entry, descent, and landing systems. Preliminary flow field and vehicle aerodynamic characteristics have been found in wind tunnel experiments; however, these only cover specific vehicle configurations and freestream conditions. In order to generate useful aerodynamic data that can be used in a trajectory simulation, a quicker method of determining vehicle aerodynamics is required to model supersonic retropropulsion effects. Using computational fluid dynamics, flow solutions can be determined which yield the desired aerodynamic information. The flow field generated in a supersonic retropropulsion scenario is complex, which increases the difficulty of generating an accurate computational solution. By validating the computational solutions against available wind tunnel data, the confidence in accurately capturing the flow field is increased, and methods to reduce the time required to generate a solution can be determined. Fun3D, a computational fluid dynamics code developed at NASA Langley Research Center, is capable of modeling the flow field structure and vehicle aerodynamics seen in previous wind tunnel experiments. Axial locations of the jet terminal shock, stagnation point, and bow shock show the same trends which were found in the wind tunnel, and the surface pressure distribution and drag coefficient are also consistent with available data. The flow solution is dependent on the computational grid used, where a grid which is too coarse does not resolve all of the flow features correctly. Refining the grid will increase the fidelity of the solution; however, the calculations will take longer if there are more cells in the computational grid.