Organizational Unit:

Space Systems Design Laboratory (SSDL)

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https://hdl.handle.net/1853/70747

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Organizational Unit

Daniel Guggenheim School of Aerospace Engineering

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https://finding-aids.library.gatech.edu/agents/corporate_entities/1138

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Publication Search Results

Now showing 1 - 10 of 89

Optimal Phasing and Performance Mapping for Translunar Satellite Missions across the Earth-Moon Nodal Cycle

(Georgia Institute of Technology, 2020-01-10) Hunter, Richard Anthony John

Fast, 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.
Development of the evolved common hardware bus (TECHBus)

(Georgia Institute of Technology, 2016-07-28) Francis, Parker

This 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.
Analysis 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.
Computational 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.
Survivability and Resiliency of Spacecraft and Space-Based Networks: a Framework for Characterization and Analysis, Version 2

(Georgia Institute of Technology, 2008-09-09) Castet, Jean-Francois ; Saleh, Joseph H.

Considerations of survivability and resiliency have always been of importance in the design and analysis of military systems. Over the past two decades, the importance of survivability and resiliency has expanded beyond military systems to include public networks and infrastructure systems. The analysis and assessment of networked systems with respect to survivability has become particularly acute in recent years, as attested to by a growing technical literature on the subject. In this paper, we bring these considerations of survivability and resiliency to bear on spacecraft and space-based networks. We develop a framework for comparing the survivability and resiliency of different space architectures, namely that of a monolithic design and a distributed (or networked) space system architecture. There are multiple metrics along which different space architectures can be benchmarked and compared. We argue that if survivability and resiliency are not accounted for, then the evaluation process is likely to be biased in favor of monolithic spacecraft. We show that if in a given context survivability and resiliency are an important requirement for a particular customer, then a distributed architecture is more likely to satisfy this requirement than a monolithic spacecraft design. We discuss in the context of our framework different classes of threats, as well as the high-frequency and low-frequency system response to (or coping strategies with) these shocks or damaging events. We illustrate the importance of this characterization for a formal definition of survivability and resiliency and a proper quantitative analysis of the subject. Finally, we propose in future work to integrate our framework with a design tool that allows the exploration of the design trade-space of distributed space architecture and show how survivability can be “optimized” or traded against other system attributes.
Survivability and Resiliency of Spacecraft and Space-Based Networks: a Framework for Characterization and Analysis, Version 1

(Georgia Institute of Technology, 2008-09) Castet, Jean-Francois ; Saleh, Joseph H.

Considerations of survivability and resiliency have always been of importance in the design and analysis of military systems. Over the past two decades, the importance of survivability and resiliency has expanded beyond military systems to include public networks and infrastructure systems. The analysis and assessment of networked systems with respect to survivability has become particularly acute in recent years, as attested to by a growing technical literature on the subject. In this paper, we bring these considerations of survivability and resiliency to bear on spacecraft and space-based networks. We develop a framework for comparing the survivability and resiliency of different space architectures, namely that of a monolithic design and a distributed (or networked) space system architecture. There are multiple metrics along which different space architectures can be benchmarked and compared. We argue that if survivability and resiliency are not accounted for, then the evaluation process is likely to be biased in favor of monolithic spacecraft. We show that if in a given context survivability and resiliency are an important requirement for a particular customer, then a distributed architecture is more likely to satisfy this requirement than a monolithic spacecraft design. We discuss in the context of our framework different classes of threats, as well as the high-frequency and low-frequency system response to (or coping strategies with) these shocks or damaging events. We illustrate the importance of this characterization for a formal definition of survivability and resiliency and a proper quantitative analysis of the subject. Finally, we propose in future work to integrate our framework with a design tool that allows the exploration of the design trade-space of distributed space architecture and show how survivability can be “optimized” or traded against other system attributes.
A Value Proposition for Lunar Architectures Utilizing Propellant Re-supply Capabilities

(Georgia Institute of Technology, 2007-09) Young, James ; Wilhite, Alan

The NASA Exploration Systems Architecture Study (ESAS)ⁱⁱ produced a transportation architecture for returning humans to the moon affordably and safely while using commercial services for tasks such as cargo delivery to low earth orbit (LEO). Another potential utilization of commercial services is the delivery of cryogenic propellants to LEO for use in lunar exploration activities. With in-space propellant re-supply available, there is the potential to increase the payload that can be delivered to the lunar surface, increase lunar mission durations, and enable a wider range of lunar missions. The addition of on-orbit propellant resupply would have far-reaching effects on the entire exploration architecture. Currently 70% of the weight delivered to LEO by the cargo launch vehicle is propellant needed for the TLI burn. This is a considerable burden and significantly limits the design freedom of the architecture. The ability of commercial providers to deliver cryogenic propellants to LEO may provide for a less expensive and better performing lunar architecture.
Responsive Space: Concept Analysis, Critical Review, and Theoretical Framework

(Georgia Institute of Technology, 2007-09) Saleh, Joseph H. ; Dubos, Gregory

Customers’ needs are dynamic and evolve in response to unfolding environmental uncertainties. The ability of a company or an industry to address these changing customers’ needs in a timely and cost-effective way is a measure of its responsiveness. In the space industry, a systemic discrepancy exists between the time constants associated with the change of customers’ needs, and the response time of the industry in delivering on-orbit solutions to these needs. Increasingly, the penalties associated with such delays are becoming unacceptable, and space responsiveness is recognized as a strategic imperative in commercial competitive and military environments. In this paper, we provide a critical assessment of the literature on responsive space and introduce a new multi-disciplinary framework for thinking about and addressing issues of space responsiveness. Our framework advocates three levels of responsiveness: a global industry-wide responsiveness, a local stakeholder responsiveness, and an interactive or inter-stakeholder responsiveness. We introduce and motivate the use of “responsiveness maps” for multiple stakeholders. We then identify “levers of responsiveness,” technical spacecraft- and launch-centric, as well as “soft” levers (e.g., acquisition policies) for improving the responsiveness of the space industry. Finally, we propose a series of research questions to aggressively tackle problems associated with space responsiveness.
The Gryphon: A Flexible Lunar Lander Design to Support a Semi-Permanent Lunar Outpost

(Georgia Institute of Technology, 2007-09) Arney, Dale ; Hickman, Joseph ; Tanner, Philip ; Wagner, John ; Wilson, Marc ; Wilhite, Alan W.

A lunar lander is designed to provide safe, reliable, and continuous access to the lunar surface by the year 2020. The NASA Exploration System Architecture is used to initially define the concept of operations, architecture elements, and overall system requirements. The design evaluates revolutionary concepts and technologies to improve the performance and safety of the lunar lander while minimizing the associated cost using advanced systems engineering capabilities and multi-attribute decision making techniques. The final design is a flexible (crew and/or cargo) lander with a side-mounted minimum ascent stage and a separate stage to perform lunar orbit insertion.
Technology Readiness Level, Schedule Risk and Slippage in Spacecraft Design: Data Analysis and Modeling

(Georgia Institute of Technology, 2007-09) Dubos, Gregory F. ; Saleh, Joseph H. ; Braun, Robert D.

Schedule slippage plagues the space industry, and is antinomic with the recent emphasis on space responsiveness. The Government Accountability Office has repeatedly noted the difficulties encountered by the Department of Defense in keeping its acquisition of space systems on schedule, and identified the low Technology Readiness Level (TRL) of the system/payload under development as a principal culprit driving schedule risk and slippage. In this paper, we analyze based on data from past space programs the relationship between technology uncertainty and schedule risk in the acquisition of space systems, and propose an analytical framework to identify appropriate schedule margins for mitigating the risk of schedule slippage. We also introduce the TRL-schedule-risk curves to help program managers make riskinformed decisions regarding the appropriate schedule margins for a given program, or the appropriate TRL to consider should the program’s schedule be exogenously and rigidly constrained. We recommend based on our findings, that the industry adopts and develops schedule risk curves (instead of single schedule point estimates), 2) that these schedule risk curves be made available to policy- and decision-makers in acquisition programs; and 3) that adequate schedule margins be defined according to an agreed upon and acceptable schedule risk level.