Organizational Unit:

Daniel Guggenheim School of Aerospace Engineering

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https://hdl.handle.net/1853/70742

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College of Engineering

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Aerospace Design Group

Organizational Unit

Aerospace Systems Design Laboratory (ASDL)

Organizational Unit

Air Transportation Laboratory

Organizational Unit

Cognitive Engineering Center

Organizational Unit

Space Systems Design Laboratory (SSDL)

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https://finding-aids.library.gatech.edu/agents/corporate_entities/106

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Publication Search Results

Now showing 1 - 10 of 13

Statistical Entry, Descent, and Landing Performance Reconstruction of the Mars Science Laboratory

(Georgia Institute of Technology, 2014-01) Dutta, Soumyo ; Braun, Robert D.

The Mars Science Laboratory spacecraft landed an approximately 900 kg rover on Mars on August 5, 2012 while using the largest aeroshell and supersonic parachute ever utilized by a planetary entry mission. Similar to past Mars missions, the spacecraft recorded inertial measurement unit data and radar altimeter measurements during its descent through the Martian atmosphere, but its aeroshell was also instrumented with ush atmospheric data system sensors that captured the pressure distribution on the vehicle during hypersonic and supersonic flight regimes. The rich data set enabled a comprehensive post flight analysis of the vehicle's trajectory. This paper shows the vehicle's reconstructed trajectory, aerodynamics, and atmospheric conditions using several statistical estimation methods, specifically the Extended Kalman filter, Unscented Kalman filter, and adaptive filter. The statistical estimation methods allow for both state estimation and uncertainty quantification of model errors, which could improve design of future Mars entry missions.
Analytically-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.
Statistical methods for reconstruction of entry, descent, and landing performance with application to vehicle design

(Georgia Institute of Technology, 2013-11-06) Dutta, Soumyo

There is significant uncertainty in our knowledge of the Martian atmosphere and the aerodynamics of the Mars entry, descent, and landing (EDL) systems. These uncertainties result in conservatism in the design of the EDL vehicles leading to higher system masses and a broad range of performance predictions. Data from flight instrumentation onboard Mars EDL systems can be used to quantify these uncertainties, but the existing dataset is sparse and many parameters of interest have not been previously observable. Many past EDL reconstructions neither utilize statistical information about the uncertainty of the measured data nor quantify the uncertainty of the estimated parameters. Statistical estimation methods can blend together disparate data types to improve the reconstruction of parameters of interest for the vehicle. For example, integrating data obtained from aeroshell-mounted pressure transducers, inertial measurement unit, and radar altimeter can improve the estimates of the trajectory, atmospheric profile, and aerodynamic coefficients, while also quantifying the uncertainty in these estimates. These same statistical methods can be leveraged to improve current engineering models in order to reduce conservatism in future EDL vehicle design. The work in this thesis presents a comprehensive methodology for parameter reconstruction and uncertainty quantification while blending dissimilar Mars EDL datasets. Statistical estimation methods applied include the Extended Kalman Filter, Unscented Kalman Filter, and Adaptive Filter. The estimators are applied in a manner in which the observability of the parameters of interest is maximized while using the sparse, disparate EDL dataset. The methodology is validated with simulated data and then applied to estimate the EDL performance of the 2012 Mars Science Laboratory. The reconstruction methodology is also utilized as a tool for improving vehicle design and reducing design conservatism. A novel method of optimizing the design of future EDL atmospheric data systems is presented by leveraging the reconstruction methodology. The methodology identifies important design trends and the point of diminishing returns of atmospheric data sensors that are critical in improving the reconstruction performance for future EDL vehicles. The impact of the estimation methodology on aerodynamic and atmospheric engineering models is also studied and suggestions are made for future EDL instrumentation.
Cramér-Rao Lower Bound Optimization of Flush Atmospheric Data System Sensor Placement

(Georgia Institute of Technology, 2013-08) Dutta, Soumyo ; Braun, Robert D.

Flush atmospheric data systems take measurements of the pressure distribution on the forebodies of vehicles and improve the estimate of freestream parameters during reconstruction. These systems have been present on many past entry vehicles, but design of the pressure transducer suites and the placement of the sensors on the vehicle forebody have largely relied on engineering judgment and heuristic techniques. This paper develops a ush atmospheric data system design methodology using Cramer-Rao lower bound optimization to define the smallest theoretical variance possible from the estimation process. Application of this methodology yields Pareto frontiers of possible optimal configurations and identifies the number of ports which serve as the point of diminishing returns. The methodology is tested with a simulated Mars entry, descent, and landing trajectory.
Preliminary Statistical Trajectory Atmosphere Reconstruction of MSL Entry Descent Landing

(Georgia Institute of Technology, 2013-02) Dutta, Soumyo ; Braun, Robert D.

On August 5, 2012, the Mars Science Laboratory spacecraft landed the heaviest payload on Mars using the largest aeroshell and supersonic parachute ever used by a planetary entry mission. Moreover, an innovative Sky Crane landing system was utilized to softly and accurately place the science payload on the ground near the desired target. The spacecraft recorded inertial measurement unit data and radar altimeter measurements during its descent through the Martian atmosphere and the aeroshell was also instrumented with flush atmospheric data system sensors that allow for the reconstruction of the vehicle's pressure distribution and freestream atmospheric conditions. This paper shows the preliminary results of the vehicle's trajectory and atmosphere reconstruction using a statistical estimation methodology that utilizes an extended Kalman filter. This method has been demonstrated with simulated Mars entry data in the past, and has the capability of simultaneously estimating the parameters and their uncertainties using the initial state covariance and measurement uncertainties.
Uncertainty Quantification for Mars Entry, Descent, and Landing Reconstruction Using Adaptive Filtering

(Georgia Institute of Technology, 2013-01) Dutta, Soumyo ; Braun, Robert D. ; Karlgaard, Christopher D.

Mars entry, descent, and landing (EDL) trajectories are highly dependent on the vehicle's aerodynamics and the planet's atmospheric properties during the day-of- flight. A majority of previous EDL trajectory and atmosphere reconstruction analyses do not simultaneously estimate the flight trajectory and the uncertainties in the models. Adaptive filtering techniques, when combined with the traditional trajectory estimation methods, can improve the knowledge of the aerodynamic coefficients and atmospheric properties, while also estimating a realistic confidence interval for these parameters. Simulated datasets with known truth data are used in this study to show the improvement in state and uncertainty estimation by using adaptive filtering techniques. Such a methodology can then be implemented on existing and future EDL datasets to determine the aerodynamic and atmospheric uncertainties and improve engineering design tools.
Atmospheric 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.
Integrated 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.
Mission 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, Ethiraj

The 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.
Comparison 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.