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Daniel Guggenheim School of Aerospace Engineering
Daniel Guggenheim School of Aerospace Engineering
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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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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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ItemMission Sizing and Trade Studies for Low Ballistic Coefficient Entry Systems to Venus(Georgia Institute of Technology, 2012-03) Dutta, Soumyo ; Smith, Brandon P. ; Prabhu, Dinesh ; Venkatapathy, EthirajThe U.S and the U.S.S.R. have sent seventeen successful atmospheric entry missions to Venus. Past missions to Venus have utilized rigid aeroshell systems for entry. This rigid aeroshell paradigm sets performance limitations since the size of the entry vehicle is constrained by the fairing diameter of the launch vehicle. This has limited ballistic coefficients (β) to well above 100 kg/m2 for the entry vehicles. In order to maximize the science payload and minimize the Thermal Protection System (TPS) mass, these missions have entered at very steep entry flight path angles (ɣ). Due to Venus’ thick atmosphere and the steep-ɣ, high-β conditions, these entry vehicles have been exposed to very high heat flux, very high pressures and extreme decelerations (upwards of 100 g’s). Deployable aeroshells avoid the launch vehicle fairing diameter constraint by expanding to a larger diameter after the launch. Due to the potentially larger wetted area, deployable aeroshells achieve lower ballistic coefficients (well below 100 kg/m2), and if they are flown at shallower flight path angles, the entry vehicle can access trajectories with far lower decelerations (~50-60 g’s), peak heat fluxes (~400 W/cm2) and peak pressures. The structural and TPS mass of the shallow-ɣ, low-β deployables are lower than their steep-ɣ, high-β rigid aeroshell counterparts at larger diameters, contributing to lower areal densities and potentially higher payload mass fractions. For example, at large diameters, deployables may attain aeroshell areal densities of 10 kg/m2 as opposed to 50 kg/m2 for rigid aeroshells. However, the low-β, shallow-ɣ paradigm also raises issues, such as the possibility of skip-out during entry. The shallow-_ could also increase the landing footprint of the vehicle. Furthermore, the deployable entry systems may be flexible, so there could be fluid-structure interaction, especially in the high altitude, low-density regimes. The need for precision in guidance, navigation and control during entry also has to be better understood. This paper investigates some of the challenges facing the design of a shallow-ɣ, low-β entry system.
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ItemComparison of Statistical Estimation Techniques for Mars Entry, Descent, and Landing Reconstruction from MEDLI-like Data Sources(Georgia Institute of Technology, 2012-01) Dutta, Soumyo ; Braun, Robert D. ; Russell, Ryan P. ; Clark, Ian G. ; Striepe, Scott A.Flight data from an entry, descent, and landing (EDL) sequence can be used to reconstruct the vehicle's trajectory, aerodynamic coefficients and the atmospheric profile experienced by the vehicle. Past Mars missions have contained instruments that do not provide direct measurement of the freestream atmospheric conditions. Thus, the uncertainties in the atmospheric reconstruction and the aerodynamic database knowledge could not be separated. The upcoming Mars Science Laboratory (MSL) will take measurements of the pressure distribution on the aeroshell forebody during entry and will allow freestream atmospheric conditions to be partially observable. This data provides a mean to separate atmospheric and aerodynamic uncertainties and is part of the MSL EDL Instrumentation (MEDLI) project. Methods to estimate the flight performance statistically using on-board measurements are demonstrated here through the use of simulated Mars data. Different statistical estimators are used to demonstrate which estimator best quantifies the uncertainties in the flight parameters. The techniques demonstrated herein are planned for application to the MSL flight dataset after the spacecraft lands on Mars in August 2012.
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ItemStatistical Entry, Descent and Landing Performance Reconstruction of the Mars Phoenix Lander(Georgia Institute of Technology, 2011-06) Dutta, Soumyo ; Clark, Ian G. ; Russell, Ryan P. ; Braun, Robert D.The Phoenix Lander successfully landed on the surface of Mars on May 25, 2008. During the entry, descent and landing (EDL), the vehicle had instruments on-board that took sensed acceleration, angular rates and altimeter measurements. In this study, methodology used to reconstruct the trajectory and other EDL performance information using a statistical filter to process the observations from the sensors is demonstrated. A statistical filter estimates parameters simultaneously with the uncertainty in the estimates. The results presented here will include Phoenix’s event timeline, trajectory information, time-of-flight atmosphere and aerodynamic coefficients of an EDL subsystem as well as the uncertainty in the estimated states.
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ItemPhoenix Location Determination using HiRISE Imagery(Georgia Institute of Technology, 2010-06) Wells, Grant ; Dutta, Soumyo ; Mattson, Sarah ; Lisano, MichaelThis investigation looked into determining Phoenix’s position using an image taken by the University of Arizona’s High Resolution Imaging Science Experiment camera. The objective was to test how accurately a position for the lander could be determined during entry, descent, and landing to provide an alternate means of position determination independent of Phoenix navigation data or Phoenix telemetry in the event of the spacecraft’s on-board inertial measurement unit failing or a communications breakdown that prevented the return of the data.
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ItemMars Entry, Descent, and Landing Trajectory and Atmosphere Reconstruction(Georgia Institute of Technology, 2010-05-05) Dutta, SoumyoFlight data from an entry, descent, and landing (EDL) sequence can be used to reconstruct the vehicle’s trajectory as well as compute the associated uncertainty. The atmospheric profile encountered by the vehicle can similarly be estimated from the flight data. Past Mars missions have contained instruments, such as accelerometers, gyroscopes, and radar altimeters that do not provide direct measurement of the free-stream atmospheric conditions. Thus, uncertainties in the atmospheric reconstruction and the aerodynamic database knowledge cannot be separated. However, the upcoming Mars Science Laboratory (MSL) will take measurements of the pressure on the aeroshell forebody during entry. These measurements will provide means to determine the free-stream conditions and to separate the atmospheric and aerodynamic uncertainties. In this paper, analytical methods to statistically estimate trajectories and free-stream conditions from flight data and to quantify uncertainties in these parameters are discussed. A sample data set from a ballistic range test of an Orion Crew Exploration Vehicle (CEV) model is then used to demonstrate results from applying these procedures. This approach utilizes the same techniques and toolset planned for subsequent application for the reconstruction of MSL’s EDL sequence in 2012.