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Daniel Guggenheim School of Aerospace Engineering
Daniel Guggenheim School of Aerospace Engineering
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ItemUtilizing Dynamical Systems Concepts in Multidisciplinary Design(Georgia Institute of Technology, 2012-09) Steinfeldt, Bradley A. ; Braun, Robert D.A general multidisciplinary design problem features coupling and feedback between contributing analyses. This feedback may lead to convergence issues requiring significant iteration in order to obtain a feasible design. This work provides a description for casting the multidisciplinary design problem as a dynamical system in order to overcome some of the challenges associated with traditional multidisciplinary design and leverage the benefits of dynamical systems theory in a new domain. Three areas from dynamical system theory are chosen for investigation: stability analysis, optimal control, and estimation theory. Stability analysis is used to investigate the existence of a solution to the design problem. Optimal control techniques allow the requirements associated with the design to be incorporated into the system and allow for constraints that are functions of both the contributing analysis outputs and input values to be handled simultaneously. Finally, estimation methods are employed to obtain an evaluation of the robustness of the multidisciplinary design. These three dynamical system techniques are then combined in a complete methodology for the rapid robust design of a linear multidisciplinary design. The developed robust design methodology allows for uncertainties both within the models as well as the parameters of the multidisciplinary problem. The performance of the developed technique is demonstrated through a linear and nonlinear example problem.
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ItemDesign Convergence Using Stability Concepts from Dynamical Systems Theory(Georgia Institute of Technology, 2012-09) Steinfeldt, Bradley A. ; Braun, Robert D.The inherent iteration required in the multidisciplinary design problem allows the design problem to cast as a dynamical system. The iteration in design is a resultant of the two root- finding problems. The first root-finding problem is in seeking out candidate designs while the second is in optimizing the candidate designs. Viewing the root-finding schema as a dynamical system allows the application of established techniques from dynamical systems theory to design. Stability theory is one of the techniques that is enabled by viewing multidisciplinary design as a dynamical system. Stability theory is capable of providing information on whether or not a design will converge for a given iteration scheme, starting values for the iteration that will lead to convergence, as well as information regarding how fast a design will converge. Following the theoretical development, each of these concepts is demonstrated on sample problems showing the benefit of the application of stability theory in the design realm.
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ItemSurvey of Blunt Body Dynamic Stability in Supersonic Flow(Georgia Institute of Technology, 2012-08) Kazemba, Cole D. ; Braun, Robert D. ; Clark, Ian G. ; Schoenenberger, MarkThis survey presents a comprehensive investigation of blunt body dynamic stability. An examination of the experimental, analytical, and computational methods for predicting dynamic stability characteristics, along with the deficiencies accompanying each method is presented. The observed influence of vehicle and environmental parameters on the resulting dynamic response is discussed. Additionally, the proposed physical mechanisms that may govern this complex phenomenon are introduced. There exists a vast amount of literature and test data that is continually growing with each mission. Compiling the observations of dynamic behavior acquired from various test geometries, environments, and techniques, as well as the proposed explanations to the observed trends, sheds light on the validity of the proposed physical mechanisms. This in turn guides future efforts to improve the experimental and computational prediction techniques and further the fundamental understanding of blunt body dynamic stability.
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ItemAtmospheric Data System Sensor Placement Optimization for Mars Entry, Descent, and Landing(Georgia Institute of Technology, 2012-08) Dutta, Soumyo ; Braun, Robert D. ; Karlgaard, Christopher D.The Mars Science Laboratory (MSL) contains an atmospheric data system that takes measurement of the pressure distribution on the entry body during the hypersonic and supersonic descent phases of the flight. This pressure data can be combined with other on- board sensors, such as accelerometers, gyros, and radar altimeter, to estimate the flight's trajectory, aerodynamics and the atmospheric profile. The number of sensors and their locations for the atmospheric data system can be optimized to increase the accuracy of the post-flight reconstruction. Methodologies based on using the estimation residual and a surrogate of the observability matrix are presented here and results of the optimization exercises for pressure transducer systems on Mars entry, descent, and landing (EDL) vehicles are shown. These techniques can be subsequently applied in the design of instrumentation suites of future EDL vehicles.
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ItemThe Extension of Analytic Hypersonic Force Coefficients for Conceptual Design Using the Divergence Theorem(Georgia Institute of Technology, 2012-08) Grant, Michael J. ; Braun, Robert D.This study investigates the type and performance of analytic Newtonian aerodynamic solutions made possible using the Divergence Theorem. A reformulation of the Newtonian surface pressure calculation enables a mathematically equivalent divergence calculation to be performed as a substitute. This manipulation enables analytic force coefficients to be derived for shapes of increasing complexity while also reducing computational cost when compared to existing analytic solutions. The divergence solutions are obtained by converting the physical flow field into a mathematical flow field that is constant in direction but with magnitude that is equivalent to the Newtonian pressure coefficient. This unique property allows various mathematical techniques that are not available with the traditional Newtonian calculation to be performed that further reduce computational cost. The results of this investigation enable the construction of analytic relations for new hypersonic configurations of interest, and this approach serves as the foundation to construct efficient hybrid exact-approximate solutions for more complex configurations. Comparisons of the current analytic database to a state-of-the-art hypersonic design tool illustrate the computational advantages of the analytic relations to support hypersonic conceptual design.
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ItemIntegrated Trajectory, Atmosphere, and Aerothermal Reconstruction Methodology Using the MEDLI Dataset(Georgia Institute of Technology, 2012-06) Dutta, Soumyo ; Mahzari, Milad ; White, Todd R. ; Braun, Robert D.The Mars Science Laboratory (MSL) mission’s instrumentation will enable accurate reconstruction of the vehicle’s entry, descent, and landing (EDL) performance including the trajectory, the observed atmosphere, aerodynamics, aeroheating, and heatshield material response. The objective of this paper is to develop methodologies for an integrated approach to the reconstruction of the vehicle’s EDL performance. Two estimation approaches are presented: Serial and Concurrent. The serial approach is demonstrated by application to the Mars Pathfinder flight data and estimating trajectory and aeroheating performance.
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ItemReconstruction of Mars Pathfinder Aerothermal Heating and Heatshield Material Response Using Inverse Methods(Georgia Institute of Technology, 2012-06) Mahzari, Milad ; Braun, Robert D. ; White, Todd R.The Mars Pathfinder probe entered the Martian atmosphere in 1997 and contained instrumentation that provided measurements of the SLA heatshield subsurface temperature at different locations during the entry sequence. These measurements represented the first Martian aeroheating flight data since the Viking Lander missions. The objective of this paper is to reconstruct the Pathfinder entry vehicle's aerothermal heating and heatshield material response using updated modeling tools and approaches in both direct and inverse manners. The direct approach consists of performing updated Computational Fluid Dynamics (CFD) calculations on a newly reconstructed entry trajectory to characterize the vehicle's heating environment. From the calculated heating boundary conditions, the heat shield in-depth temperature response is computed using an updated thermal response and ablation model for the SLA material. These predictions are compared directly to the flight data. In addition to the direct comparison approach, inverse methods are used to estimate boundary conditions that result in a closer match between the flight data and subsurface temperature predictions. The unblown surface heat transfer coefficient is reconstructed as a function of time using whole-time domain least-squares methods in conjunction with regularization techniques.
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ItemTime-dependant Estimation of Mars Science Laboratory Surface Heating from Simulated MEDLI Data(Georgia Institute of Technology, 2012-06) Mahzari, Milad ; Braun, Robert D.There are substantial uncertainties in the computational models currently used to predict the heating environment and the Thermal Protection System (TPS) material response during Mars entry. Flight data is required to quantify and possibly reduce such uncertainties as well as improve current computational tools. The Mars Science Laboratory (MSL) Entry, Descent and Landing Instrumentation (MEDLI) suite will provide a comprehensive set of flight data which will include subsurface temperature measurements of its PICA heat shield at different locations. Accurate reconstruction of MSL surface heat flux from the flight data is a critical step in reducing these uncertainties. The purpose of this paper is to investigate the time-dependent estimation of MSL surface heating from simulated MEDLI subsurface temperature data using inverse methods in the presence of random and bias measurement and model errors. The surface heat flux is indirectly reconstructed by estimating the discretized surface heat transfer coefficient profile as a function of time. Whole-time domain least-squares methods in conjunction with the Tikhonov regularization technique are applied to this problem. The analysis is performed for the instrument plugs at the lowest and highest heating locations. The performance of the estimation methods and the accuracy of the reconstructed surface conditions are investigated under different types of errors in the measurements such as random noise and thermocouple lag. Furthermore, the effect of material property bias on the estimation of surface conditions is also studied.
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ItemMass Model Development for Conceptual Design of a Hypersonic Rigid Deployable Decelerator(Georgia Institute of Technology, 2012-06) Cruz-Ayoroa, Juan G. ; Kazemba, Cole D. ; Steinfeldt, Bradley A. ; Kelly, Jenny R. ; Clark, Ian G. ; Braun, Robert D.As the required payload masses for planetary entry systems increase, innovative entry vehicle decelerator systems are becoming a topic of interest. With this interest comes a growing need for the capability to characterize the performance of such decelerators. This work proposes a first-order mass model for fully-rigid deployable decelerator systems. The analytical methodology that is presented can be applied to a wide range of entry conditions and material properties for rapid design space exploration. The tool is applied to a case study of a C/SiC hot structure decelerator at Mars for comparison to the performance of the Hypersonic Inflatable Aerodynamic Decelerator concepts presented in a recent EDL-SA study. Results show that the performance of a rigid deployable structure can be comparable to that of a Hypersonic Inflatable Aerodynamic Decelerator at high entry ballistic coefficients and small decelerator diameters.
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ItemConceptual Modeling of Supersonic Retropropulsion Flow Interactions and the Relationship to System Performance(Georgia Institute of Technology, 2012-06) Korzun, Ashley M. ; Braun, Robert D.Supersonic retropropulsion is an entry, descent, and landing technology applicable to and potentially enabling the high-mass missions to the surface required for advanced robotic and human exploration at Mars. For conceptual design, an initial understanding of the significance of retropropulsion configuration on the vehicle’s static aerodynamic characteristics and the relation of this configuration to other vehicle performance metrics that traditionally determine vehicle configuration is necessary. This work develops an approximate model for the aerodynamic - propulsive flow interaction based on momentum transfer within the flowfield and the geometry of relevant flow structures. This model is used to explore the impact of operating conditions, required propulsion system performance, propulsion system composition, and vehicle configuration on the integrated aerodynamic drag characteristics of full-scale vehicles for Mars entry, descent, and landing. Conclusions are then drawn on the fidelity and effort required to support specific design trades for supersonic retropropulsion.