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Daniel Guggenheim School of Aerospace Engineering
Daniel Guggenheim School of Aerospace Engineering
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ItemCooperative Scenarios for Human Exploration Beyond Low Earth Orbit(Georgia Institute of Technology, 2014-09) Battat, Jonathan ; Alifanov, Oleg ; Braun, Robert D. ; Crawley, Edward ; Logsdon, John ; Zeleny, Lev ; Borowitz, Mariel ; Capparelli, Emanuele ; Davison, Peter ; Golkar, Alessandro ; Steinfeldt, Bradley A.There is an international need to define a concrete strategy and plan to implement that strategy for the initial human exploration missions beyond Low Earth Orbit (LEO). Across all stakeholders, there is a growing consensus that the long term objective of global human space exploration is the long duration presence of people on the Martian surface. Along the pathway between current activities in LEO and eventual Mars outposts are a variety of preparatory exploration missions and intermediate goals. Over the last decade several different initial steps along these pathways beyond LEO have been proposed. It is important to build international consensus on such a plan soon because future missions require near-term investments for new capabilities with no single nation committing resources to achieve all the steps of an ambitious program on its own. The goal of this work is to enumerate and evaluate scenarios for cooperative missions beyond LEO that achieve incremental development of human exploration capabilities. Towards the goal of generating scenarios for cooperative missions beyond LEO, proposed missions and capabilities from a variety of international actors have been assessed. Presented in this paper are results of a survey of proposed missions and a series of interviews with industry experts knowledgeable about both the technical and geopolitical issues in forging a sustainable path towards Mars. There are four realistic proposals for initial human exploration beyond LEO: a cis-Lunar habitat, asteroid redirect, Mars flyby, and a Lunar surface sortie. In the absence of top-down agreements, such as those governing the International Space Station, that specify partnership responsibilities and privileges, ad-hoc exchanges within individual development projects or for specific mission capabilities is most likely to facilitate international cooperation in the coming years. General LEO transportation logistics and habitation functions are shared by many actors and allow for exchange of services and utilization of exploration assets if designed into the critical path. Given the early stage of readiness, it is possible that subsystem-level coordination could be pursued for an advanced habitation element. Other technologies are either niche (robotics) or have national sensitivities (in-space propulsion) that make them less desirable for subsystem-level coordination.
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ItemExtensibility of a Linear Rapid Robust Design Methodology(Georgia Institute of Technology, 2014-01) Steinfeldt, Bradley A. ; Braun, Robert D.The extensibility of a linear rapid robust design methodology is examined. This analysis is approached from a computational cost and accuracy perspective. The sensitivity of the solution's computational cost is examined by analysing effects such as the number of design variables, nonlinearity of the CAs, and nonlinearity of the response in addition to several potential complexity metrics. Relative to traditional robust design methods, the linear rapid robust design methodology scaled better with the size of the problem and had performance that exceeded the traditional techniques examined. The accuracy of applying a method with linear fundamentals to nonlinear problems was examined. It is observed that if the magnitude of nonlinearity is less than 1000 times that of the nominal linear response, the error associated with applying successive linearization will result in errors in the response less than 10% compared to the full nonlinear error.
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ItemUsing Estimation Techniques in Multidisciplinary Design(Georgia Institute of Technology, 2014-01) Steinfeldt, Bradley A. ; Braun, Robert D.Viewing the multidisciplinary design problem as a dynamical system a number of tools from the established field of dynamical system theory became available to the multidisciplinary design community. This work demonstrates the applicability of applying the Kalman filter in a manner similar to linear covariance analysis to the multidisciplinary design problem to obtain robustness characteristics. In addition to robustness characteristics, the estimation theory is shown to be applicable to design decomposition. Following theoretical development, two example problems demonstrate the applicability of applying dynamical system theory. For a linear, two contributing analysis problem showed the mean was able to be estimated with an error less than 0.08% and a matrix norm bounded the variance to less than 37.8% relative to analytic propagation. This error is shown to be a function of the geometry of the matrix two-norm and reduces as the problem dimensionality increases. The use of estimation theory is also shown to be applicable for nonlinear designs through a two-bar truss problem through successive linearization.
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ItemAnalytically-derived Aerodynamic Force Moment Coefficients of Resident Space Objects in Free-Molecular Flow(Georgia Institute of Technology, 2014-01) Hart, Kenneth A. ; Dutta, Soumyo ; Simonis, Kyle R. ; Steinfeldt, Bradley A. ; Braun, Robert D.Fast, high-fidelity trajectory propagation of objects in near-Earth orbits is a key capability for space situational awareness and mitigating probability of collisions on orbit. This high-fidelity analysis requires accurate aerodynamics prediction for objects in the free- molecular regime of flight, but most tools for aerodynamic prediction for this regime either are found using assumptions or are computationally intensive. Symbolic manipulation software can be used to analytically integrate expressions for pressure and shear pressure coefficients acting on a general body in free-molecular regime to derive aerodynamic force and moment expressions. The analytical aerodynamics prediction method is described and relations have been developed for the sphere, cylinder, panel, and rectangular prism. The NASA-developed Direct Simulation Monte Carlo Analysis Code is used to validate the analytical expressions and it is shown that expressions are accurate within 0.38%. These generalized analytic expressions in terms of angle of attack, sideslip angle, freestream conditions, wall temperature, and accommodation coefficients allow near-instantaneous computation of the rarefied aerodynamics and enables space situation awareness analysis.
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ItemSupersonic Inflatable Aerodynamic Decelerators for Use on Sounding Rocket Payloads(Georgia Institute of Technology, 2014-01) Miller, Matthew J. ; Steinfeldt, Bradley A. ; Braun, Robert D.This paper presents an assessment of a supersonic inflatable aerodynamic decelerator for use on a sounding rocket payload bus structure for a high-altitude sample return mission. Three decelerator configurations, the tension cone, attached isotensoid, and the trailing isotensoid, were examined on the metrics of decelerator mass, aerodynamic performance, and vehicle integration. The attached isotensoid configuration is shown to be the least mass solution. Aerodynamic analysis shows that a drag performance degradation of up to 40% for the attached decelerators results when the attachment point is recessed from the forebody of the bus structure. Vehicle integration mechanisms are identified and examined for each decelerator configuration. Using multiattribute decision making techniques, the trailing isotensoid is identified to be the most advantageous decelerator option for use in this application.