Organizational Unit:

Space Systems Design Laboratory (SSDL)

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https://hdl.handle.net/1853/70747

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Organizational Unit

Daniel Guggenheim School of Aerospace Engineering

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https://finding-aids.library.gatech.edu/agents/corporate_entities/1138

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Publication Search Results

Now showing 1 - 10 of 27

Survey of Blunt Body Dynamic Stability in Supersonic Flow

(Georgia Institute of Technology, 2012-08) Kazemba, Cole D. ; Braun, Robert D. ; Clark, Ian G. ; Schoenenberger, Mark

This 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.
Mass 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.
Guided Entry Performance of Low Ballistic Coefficient Vehicles at Mars

(Georgia Institute of Technology, 2012-03) Meginnis, Ian ; Putnam, Zachary R. ; Clark, Ian G. ; Braun, Robert D. ; Barton, Gregg H.

Current Mars entry, descent, and landing technology is near its performance limit and is unable to land payloads on the surface that exceed approximately 1 metric ton. One option for increasing landed payload mass capability is decreasing the entry vehicle’s hypersonic ballistic coefficient. A lower ballistic coefficient vehicle decelerates higher in the atmosphere, providing additional timeline and altitude margin necessary for heavier payloads. This study analyzed the guided entry performance of concept low ballistic coefficient vehicles at Mars. A terminal point controller guidance algorithm was used to provide precision targeting capability. Accuracy at parachute deploy, peak deceleration, peak heat rate, and integrated heat load were assessed and compared to a traditional vehicle to determine the effects of lowering the vehicle ballistic coefficient on entry performance. Results from this study suggest that while accuracy at parachute deploy degrades with decreasing ballistic coefficient, accuracy and other performance metrics remain within reasonable bounds for ballistic coefficients as low as 1 kg/m2. As such, this investigation demonstrates that from a performance standpoint, guided entry vehicles with large diameters may be feasible at Mars.
Drag Modulation Flight Control for Aerocapture

(Georgia Institute of Technology, 2012-03) Putnam, Zachary R. ; Clark, Ian G. ; Braun, Robert D.

Hypersonic deployable aerodynamic devices, both rigid and inflatable, have the potential to enable a broad spectrum of next-generation aeroassist missions by mitigating shape and size constraints on aeroassist vehicles and providing an in-flight reconfiguration capability. Such a capability provides new options for flight control during atmospheric flight, such as drag modulation. Drag modulation is an attractive flight control option for future aerocapture missions because it requires only minimal additional system complexity for vehicles with deployable aerodynamic devices, in contrast to more conventional lift-modulation steering methods. This study expands upon previous aerocapture drag modulation studies by extending the analysis of single-event jettison systems to Earth and Mars. A single-event jettison guidance algorithm was developed and used to evaluate the feasibility of real-time targeting of apoapsis altitude during flight. Results indicate that sufficiently large ballistic coefficient ratios provide adequate aerodynamic and guided corridors for future aerocapture missions. While the preliminary guidance algorithm demonstrates only modest insertion accuracy, this level of accuracy may be tolerable for certain missions.
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.
System Level Impact of Landing Point Redesignation for High-Mass Mars Missions

(Georgia Institute of Technology, 2011-09) Chua, Zarrin K. ; Steinfeldt, Bradley A. ; Kelly, Jenny R. ; Clark, Ian G.

This work presents a preliminary system level assessment of the payload mass change due to landing point redesignation of representative high-mass Mars systems (systems with entry masses greater than 20 t). An optimal propulsive descent guidance law which minimizes the control effort during the descent is used in order to assess the range of feasible landing sites as well as the mass impact on the payload of the system. It is shown that either increasing the entry mass or delaying the time of redesignating the landing site decreases the payload capability of reaching the surface as well as reduces the number of reachable landing sites. In addition, it is shown that the payloads associated with supersonic retropropulsion are more sensitive to the landing point redesignation time than systems using inflatable aerodynamic decelerators.
Rapid Simultaneous Hypersonic Aerodynamic and Trajectory Optimization Using Variational Methods

(Georgia Institute of Technology, 2011-08) Grant, Michael J. ; Clark, Ian G. ; Braun, Robert D.

Traditional multidisciplinary design optimization methodologies of hypersonic missions often employ population-based global searching methods that rely on shooting methods to perform trajectory optimization. In this investigation, a rapid simultaneous hypersonic aerodynamic and trajectory optimization methodology is constructed based on variational methods. This methodology is constructed from two enabling advancements in analytic hypersonic aerodynamics and rapid trajectory optimization. Comparisons made with a single and multi-objective particle swarm optimizer highlight the computational advantages and improved solutions obtained through continuation of variational methods. The incorporation of trajectory constraints into the particle swarm optimization process through penalty functions or as additional objectives is shown to greatly increase the complexity of the design process. Alternatively, variational methods are able to precisely satisfy trajectory constraints without this added complexity. Examples demonstrate that Pareto frontiers in both vehicle and trajectory objectives can be constructed using variational methods. For convex frontiers, this is performed using a weighted sum of the objectives. For non- convex frontiers, the optimization is performed through continuation of a set of constrained objectives.
Rapid Design Space Exploration for Conceptual Design of Hypersonic Missions

(Georgia Institute of Technology, 2011-08) Grant, Michael J. ; Clark, Ian G. ; Braun, Robert D.

During conceptual design, multidisciplinary optimization is often performed using computationally intensive direct methods. Prior work has shown that rapid design studies can be performed using fast indirect methods, but several optimization techniques including discrete dynamic programming, nonlinear inversion, and pseudo spectral methods are required to construct a suitable initial guess within the design space. In this investigation, a simplified methodology is developed to eliminate these optimization techniques, enabling rapid design space exploration using continuation of indirect methods alone. This is made possible by initially converging to a simple solution that is outside of the design space of interest, and solutions within the design space of interest are quickly accessed through continuation from this initial solution. As an initial step to automate this continuation process, state transition tensors are used to predict optimal solutions throughout the design space. A methodology is developed to provide accurate predictions of trajectories with varying flight times, and the error of these predictions is controlled to regulate the continuation process. This approach provides flexibility to adapt to future computational capabilities and serves as an initial step to bridge the gap between conceptual trajectory design and onboard trajectory planning.
Performance Characterization, Sensitivity and Comparison of a Dual Layer Thermal Protection System

(Georgia Institute of Technology, 2011-06) Kazemba, Cole D. ; McGuire, Mary Kathleen ; Howard, Austin ; Clark, Ian G. ; Braun, Robert D.

With the goal of landing high-mass cargo or crewed missions on Mars, NASA has been developing new thermal protection technologies with enhanced capability and reduced mass compared to traditional approaches. Two examples of new thermal protection system (TPS) concepts are dual layer and flexible TPS. Each of these systems introduces unique challenges along with potential performance enhancements. Traditional monolithic ablative TPS, which have been flown on every Mars robotic mission to date, use a single layer of ablative material. The new dual layer TPS concepts utilize an insulating layer of material beneath an ablative layer to increase efficiency and save mass. A study was conducted on the dual layer system to identify sensitivities in performance to uncertainties in material properties and aerothermal environments. A performance metric which is independent of the system construction was developed in order to directly compare the abilities and benefits between the traditional, dual layer and eventually, flexible systems. Using a custom MATLAB code enveloping the Fully Implicit Ablation and Thermal Response Program (FIAT), the required TPS areal mass was calculated for several different parametric scenarios. Overall TPS areal mass was found to be most sensitive to the constraining allowable temperature in each system and aerothermal heat transfer augmentation (attributed here to material surface roughness). From these preliminary results it was found that the nominal dual layer TPS construction investigated could produce improvements over a traditional TPS in the specified performance metric between 14-36%, depending on the flight environments and total integrated heat load expected.
Statistical 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.