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Daniel Guggenheim School of Aerospace Engineering
Daniel Guggenheim School of Aerospace Engineering
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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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ItemA Statistics-Based Material Property Analysis to Support Ablation Simulation UQ Efforts(Georgia Institute of Technology, 2012-04) Copeland, Sean R. ; Mahzari, Milad ; Cozmuta, Ioana ; Alonso, Juan J.Accurate characterization of Thermal Protection System (TPS) material properties is an important component in modeling and simulating the response of the material under heating. Unfortunately, for many common TPS materials, especially ablators, these material properties are not always well known and contribute a source of aleatory uncertainty to thermal simulations, impacting the safety and reliability of entry systems. Furthermore, efforts to capture these uncertainties have been hampered by a lack of suitable experimental data to establish proper input statistics, necessitating the use of ad-hoc methodologies to fabricate input PDFs. In this work, new ablator material property data from the Mars Science Laboratory (MSL) program is used to construct experimentally-based material property PDFs for use in non-deterministic ablation simulations. A standard UQ propagation, sensitivity analysis and uncertainty contributor breakdown analysis is performed using the revised input set in the anticipated MSL aerothermal environment. Lastly, a problem is formulated to quantitatively establish the relationship between errors in input statistics and errors in output quantities of interest.
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ItemProposed Analysis Process for Mars Science Laboratory Heat Shield Sensor Plug Flight Data(Georgia Institute of Technology, 2011-06) Cozmuta, Ioana ; White, Todd R. ; Santos, Jose A. ; Laub, Bernard ; Mahzari, MiladThe Mars Science Laboratory (MSL) mission is scheduled to enter the Martian atmosphere in August 2012. Aboard the heatshield is the MSL Entry Descent and Landing Instrumentation (MEDLI) system that includes a series of embedded sensor plugs to measure in-depth response of the thermal protection system (TPS). The general objectives of the MEDLI system are to assess the TPS performance and reconstruct the aerothermal environment experienced during entry. Some specific objectives, such as measuring TPS temperature, can be addressed with direct measurements. Other objectives, such as determining surface heating, must be inferred using measurements combined with analytical tools. This paper describes the specific objectives, the expected sensor responses to the entry environment based on aerothermal and material response simulations, and the reconstruction analysis process being developed for the flight data.
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ItemAn Inverse Parameter Estimation Methodology for the Analysis of Aeroheating and Thermal Protection System Experimental Data(Georgia Institute of Technology, 2010-09-27) Mahzari, MiladThere are substantial uncertainties in the computational models currently used to predict a spacecraft’s heating environment and the Thermal Protection System (TPS) material response during Mars entry. Flight data will help reduce these uncertainties and improve the current computational tools. The Mars Science Laboratory (MSL) Entry, Descent and Landing Instrumentation (MEDLI) suite will provide more aeroheating data than all the previous Mars missions combined. Motivated by this future data, a comprehensive inverse parameter estimation methodology is presented in this paper for the analysis of aeroheating and TPS experimental data. The proposed methodology is applied to an MSL relevant Arcjet test dataset to investigate the feasibility of the proposed approach. The first step is the Nominal Analysis where the quality of the experimental data is examined and a comparison to the nominal predictions is presented. The second step is the Monte Carlo Analysis where a Monte Carlo study is performed to identify the model input parameters that contribute the most to the measurement uncertainty. The third step is the Sensitivity Analysis where the correlation between the different input parameters is investigated in order to determine what parameters can be estimated simultaneously. Finally the last step is the Inverse Analysis where an inverse parameter estimation code is developed to estimate heating and material parameters from the Arcjet data. Solution existence, uniqueness and stability were identified as the main challenges faced in the inverse analysis. Some strategies were suggested in order to deal with these challenges. Finally, in order to show how the different steps of this methodology come together a test problem was solved.
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ItemA Historical Review of Inflatable Aerodynamic Decelerator Technology Development(Georgia Institute of Technology, 2010-03) Smith, Brandon P. ; Tanner, Christopher L. ; Mahzari, Milad ; Clark, Ian G. ; Braun, Robert D. ; Cheatwood, F. McNeilViking-era deployable decelerator technology has been employed for several planetary probe missions at Earth and within other planetary atmospheres.1 2 Numerous system studies in the past fifty years demonstrate the benefit of developing a new decelerator technology capable of operating at higher Mach numbers and higher dynamic pressures than existing decelerators allow. The deployable Inflatable Aerodynamic Decelerator (IAD) is one such technology. This survey paper describes the development history of the IAD from its conception in the 1960’s to the present day. Major findings in primary IAD sub-disciplines for the foremost configurations are discussed. Quantitative engineering data from prior testing is reproduced directly, while qualitative conclusions are referenced in the literature. This work provides a summary of past and present IAD technology development efforts and shows data in a manner useful for today’s mission designers.