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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

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Aerospace Systems Design Laboratory (ASDL)

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Air Transportation Laboratory

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Cognitive Engineering Center

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Space Systems Design Laboratory (SSDL)

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Publication Search Results

Now showing 1 - 10 of 14

Evaluation of Deployable Aerosurface Systems for Mars Entry

(Georgia Institute of Technology, 2012-12-14) Cruz-Ayoroa, Juan G.

One of the challenges presented by the exploration of Mars is the entry, descent and landing (EDL) of payloads to the surface. Current robotic missions to Mars are reaching the limist of existing Viking heritage EDL technologies. A number of EDL technology improvements can be made to extend the capabilities beyond the current landed mass limits, including increasing the entry vehicle hypersonic drag and lift capability. Technologies being currently studied include inflatable aerodynamic decelerators, which are designed to increase vehicle drag. Many of these concepts center on axisymmetric designs, which provide high drag but relatively low lift and are most easily integrated to blunt entry vehicles. However, due to packaging density and launch vehicle fairing constraints, it is likely that future missions will require the use of slender bodies. This study investigates three deployable concepts designed to provide better integration into a slender vehicle while augmenting its performance by increasing its hypersonic drag. The deployable aerosurfaces are applied to a 5 meter diameter slender vehicle for a robotic mission at Mars with entry masses ranging from 10 to 60t. A multidisciplinary design optimization framework is used to estimate the landed mass capability of each system. Results show that the deployable concepts can significantly improve payload mass capability by reducing the terminal propulsion propellant required. Initial feasibility studies show that the concepts are hypersonically statically stable and comply with mechanical and thermal material capabilities
Implementation of a Mesomechanical Material Model for IAD Fabrics within LS-DYNA

(Georgia Institute of Technology, 2012-12-14) Hill, Jeremy

The implementation and evaluation of a high fidelity material model for dry fabrics is the main objective of this paper. Inflatable Aerodynamic Decelerators (IADs) and other air inflated structures quite often utilize woven fabrics due to their lightweight and high loading carrying capabilities. Design optimization of these inflated structures relies on a detailed understanding of the woven fabric mechanics. Woven fabrics are composite orthotropic materials that respond differently under load from traditional solid mechanics. While low fidelity fabric materials usually assume a continuous medium, a higher fidelity model needs to account for the reorientation of yarns and weave geometry. An existing mesomechanical material model within the LS-DYNAÒ commercial non-linear finite element software package is utilized. In this paper, experimental stress-strain data for Kevlar 129 samples are validated against numerical simulations of models with matching geometry and loading conditions.
Dynamic Stability Analysis of Blunt Body Entry Vehicles Through the Use of a Time-Lagged Aftbody Pitching Moment

(Georgia Institute of Technology, 2012-10-05) Kazemba, Cole

This analysis defines an analytic model for the pitching motion of blunt bodies during atmospheric entry. The proposed model is independent of the pitch damping sum term which is present in the standard equations of motion, instead using the principle of a time-lagged aftbody moment as the forcing function for oscillation divergence. Four parameters, all with intuitive physical relevance, are introduced to fully define the aftbody moment and the associated time delay. It is shown that the dynamic oscillation responses typical to blunt bodies can be produced using hysteresis of the aftbody moment alone. The approach used in this investigation is shown to be useful in understanding the governing physical mechanisms for blunt body dynamic stability and in guiding vehicle and mission design requirements. A case study using simulated ballistic range test data is conducted. From this, parameter identification is carried out through the use of a least squares optimizing routine. Results show good agreement with the limited existing literature for the parameters identified. The model parameters were found to be accurate for a wide array of initial conditions and can be identified with a reasonable number of ballistic range shots and computational effort.
Guided Entry Performance of Low Ballistic Coefficient Vehicles at Mars

(Georgia Institute of Technology, 2012-05-21) Meginnis, Ian M.

Current Mars entry, descent, and landing technology is near its performance limit and is generally 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 landing more massive payloads. This study analyzed the guided entry performance of several low ballistic coefficient vehicle concepts at Mars. A terminal point controller guidance algorithm, based on the Apollo Final Phase algorithm, was used to provide precision targeting capability. Terminal accuracy, peak deceleration, peak heat rate, and integrated heat load were assessed and compared to a traditional Mars entry vehicle concept to determine the effects of lowering the vehicle ballistic coefficient on entry performance. Results indicate that, while terminal accuracy degrades slightly with decreasing ballistic coefficient, the terminal 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 low ballistic coefficients (large diameters) may be feasible at Mars. Additionally, flight performance may be improved through the use of guidance schemes designed specifically for low ballistic coefficient vehicles, as well as novel terminal descent systems designed around low ballistic coefficient trajectories
Rapid simultaneous hypersonic aerodynamic and trajectory optimization for conceptual design

(Georgia Institute of Technology, 2012-03-30) Grant, Michael James

Traditionally, the design of complex aerospace systems requires iteration among segregated disciplines such as aerodynamic modeling and trajectory optimization. Multidisciplinary design optimization algorithms have been developed to efficiently orchestrate the interaction among these disciplines during the design process. For example, vehicle capability is generally obtained through sequential iteration among vehicle shape, aerodynamic performance, and trajectory optimization routines in which aerodynamic performance is obtained from large pre-computed tables that are a function of angle of attack, sideslip, and flight conditions. This numerical approach segregates advancements in vehicle shape design from advancements in trajectory optimization. This investigation advances the state-of-the-art in conceptual hypersonic aerodynamic analysis and trajectory optimization by removing the source of iteration between aerodynamic and trajectory analyses and capitalizing on fundamental linkages across hypersonic solutions. Analytic aerodynamic relations, like those derived in this investigation, are possible in any flow regime in which the flowfield can be accurately described analytically. These relations eliminate the large aerodynamic tables that contribute to the segregation of disciplinary advancements. Within the limits of Newtonian flow theory, many of the analytic expressions derived in this investigation provide exact solutions that eliminate the computational error of approximate methods widely used today while simultaneously improving computational performance. To address the mathematical limit of analytic solutions, additional relations are developed that fundamentally alter the manner in which Newtonian aerodynamics are calculated. The resulting aerodynamic expressions provide an analytic mapping of vehicle shape to trajectory performance. This analytic mapping collapses the traditional, segregated design environment into a single, unified, mathematical framework which enables fast, specialized trajectory optimization methods to be extended to also include vehicle shape. A rapid trajectory optimization methodology suitable for this new, mathematically integrated design environment is also developed by relying on the continuation of solutions found via indirect methods. Examples demonstrate that families of optimal hypersonic trajectories can be quickly constructed for varying trajectory parameters, vehicle shapes, atmospheric properties, and gravity models to support design space exploration, trade studies, and vehicle requirements definition. These results validate the hypothesis that many hypersonic trajectory solutions are connected through fast indirect optimization methods. The extension of this trajectory optimization methodology to include vehicle shape through the development of analytic hypersonic aerodynamic relations enables the construction of a unified mathematical framework to perform rapid, simultaneous hypersonic aerodynamic and trajectory optimization. Performance comparisons relative to state-of-the-art methodologies illustrate the computational advantages of this new, unified design environment.
Aerodynamic and performance characterization of supersonic retropropulsion for application to planetary entry and descent

(Georgia Institute of Technology, 2012-03-29) Korzun, Ashley Marie

Supersonic deceleration has been identified as a critical deficiency in extending heritage technologies to the high-mass systems required to achieve long-term exploration goals at Mars. Supersonic retropropulsion (SRP), or the use of retropropulsive thrust while an entry vehicle is traveling at supersonic conditions, is an approach addressing this deficiency. The focus of this dissertation is aerodynamic and performance evaluation of SRP as a decelerator technology for high-mass Mars entry systems. This evaluation was completed through a detailed SRP performance analysis, establishment of the relationship between vehicle performance and the aerodynamic-propulsive interaction, and an assessment of the required fidelity and computational cost in simulating SRP flowfields, with emphasis on the effort required in conceptual design. Trajectory optimization, high-fidelity computational aerodynamic analysis, and analytical modeling of the SRP aerodynamic-propulsive interaction were used to define the fidelity and effort required to evaluate individual SRP concepts across multiple mission scales.
Problem decomposition by mutual information and force-based clustering

(Georgia Institute of Technology, 2012-03-28) Otero, Richard Edward

The scale of engineering problems has sharply increased over the last twenty years. Larger coupled systems, increasing complexity, and limited resources create a need for methods that automatically decompose problems into manageable sub-problems by discovering and leveraging problem structure. The ability to learn the coupling (inter-dependence) structure and reorganize the original problem could lead to large reductions in the time to analyze complex problems. Such decomposition methods could also provide engineering insight on the fundamental physics driving problem solution. This work forwards the current state of the art in engineering decomposition through the application of techniques originally developed within computer science and information theory. The work describes the current state of automatic problem decomposition in engineering and utilizes several promising ideas to advance the state of the practice. Mutual information is a novel metric for data dependence and works on both continuous and discrete data. Mutual information can measure both the linear and non-linear dependence between variables without the limitations of linear dependence measured through covariance. Mutual information is also able to handle data that does not have derivative information, unlike other metrics that require it. The value of mutual information to engineering design work is demonstrated on a planetary entry problem. This study utilizes a novel tool developed in this work for planetary entry system synthesis. A graphical method, force-based clustering, is used to discover related sub-graph structure as a function of problem structure and links ranked by their mutual information. This method does not require the stochastic use of neural networks and could be used with any link ranking method currently utilized in the field. Application of this method is demonstrated on a large, coupled low-thrust trajectory problem. Mutual information also serves as the basis for an alternative global optimizer, called MIMIC, which is unrelated to Genetic Algorithms. Advancement to the current practice demonstrates the use of MIMIC as a global method that explicitly models problem structure with mutual information, providing an alternate method for globally searching multi-modal domains. By leveraging discovered problem inter-dependencies, MIMIC may be appropriate for highly coupled problems or those with large function evaluation cost. This work introduces a useful addition to the MIMIC algorithm that enables its use on continuous input variables. By leveraging automatic decision tree generation methods from Machine Learning and a set of randomly generated test problems, decision trees for which method to apply are also created, quantifying decomposition performance over a large region of the design space.
Aeroelastic analysis and testing of supersonic inflatable aerodynamic decelerators

(Georgia Institute of Technology, 2012-01-17) Tanner, Christopher Lee

The current limits of supersonic parachute technology may constrain the ability to safely land future robotic assets on the surface of Mars. This constraint has led to a renewed interest in supersonic inflatable aerodynamic decelerator (IAD) technology, which offers performance advantages over the DGB parachute. Two supersonic IAD designs of interest include the isotensoid and tension cone, named for their respective formative structural theories. Although these concepts have been the subject of various tests and analyses in the 1960s, 1970s, and 2000s, significant work remains to advance supersonic IADs to a technology readiness level that will enable their use on future flight missions. In particular, a review of the literature revealed a deficiency in adequate aerodynamic and aeroelastic data for these two IAD configurations at transonic and subsonic speeds. The first portion of this research amended this deficiency by testing flexible IAD articles at relevant transonic and subsonic conditions. The data obtained from these tests showed that the tension cone has superior drag performance with respect to the isotensoid, but that the isotensoid may demonstrate more favorable aeroelastic qualities than the tension cone. Additionally, despite the best efforts in test article design, there remains ambiguity regarding the accuracy of the observed subscale behavior for flight scale IADs. Due to the expense and complexity of large-scale testing, computational fluid-structure interaction (FSI) analyses will play an increasingly significant role in qualifying flight scale IADs for mission readiness. The second portion of this research involved the verification and validation of finite element analysis (FEA) and computational fluid dynamic (CFD) codes for use within an FSI framework. These verification and validation exercises lend credence to subsequent coupled FSI analyses involving more complex geometries and models. The third portion of this research used this FSI framework to predict the static aeroelastic response of a tension cone IAD in supersonic flow. Computational models were constructed to mimic the wind tunnel test articles and flow conditions. Converged FSI responses computed for the tension cone agreed reasonably well with wind tunnel data when orthotropic material models were used and indicated that current material models may require unrealistic input parameters in order to recover realistic deformations. These FSI analyses are among the first results published that present an extensive comparison between FSI computational models and wind tunnel data for a supersonic IAD.
A comparison of multiple techniques for the reconstruction of entry, descent, and landing trajectories and atmospheres

(Georgia Institute of Technology, 2011-04-05) Wells, Grant

The primary importance of trajectory reconstruction is to assess the accuracy of pre-flight predictions of the entry trajectory. While numerous entry systems have flown, often these systems are not adequately instrumented or the flight team not adequately funded to perform the statistical engineering reconstruction required to quantify performance and feed-forward lessons learned into future missions. As such, entry system performance and reliability levels remain unsubstantiated and improvement in aerothermodynamic and flight dynamics modeling remains data poor. The comparison is done in an effort to quantitatively and qualitatively compare Kalman filtering methods of reconstructing trajectories and atmospheric conditions from entry systems flight data. The first Kalman filter used is the extended Kalman filter. Extended Kalman filtering has been used extensively in trajectory reconstruction both for orbiting spacecraft and for planetary probes. The second Kalman filter is the unscented Kalman filter. Additionally, a technique for using collocation to reconstruct trajectories is formulated, and collocation's usefulness for trajectory simulation is demonstrated for entry, descent, and landing trajectories using a method developed here to deterministically find the state variables of the trajectory without nonlinear programming. Such an approach could allow one to utilize the same collocation trajectory design tools for the subsequent reconstruction.
Oscillation of Supersonic Inflatable Aerodynamic Decelerators at Mars

(Georgia Institute of Technology, 2010-12-01) Smith, Brandon P.

This analysis considers the dynamic stability of a notional Mars 2018 entry probe augmented with an attached supersonic inflatable aerodynamic decelerator (SIAD) deployed at Mach 5. Dynamics of the attached isotensoid and tension cone SIAD configurations are compared using an explicit solution to the planar equations of motion. A current experimental database of flexible isotensoid and tension cone static aerodynamics is employed in the simulation. Pitch-damping data from the Mars Science Laboratory (MSL) ballistic range tests is parameterized and applied to the SIAD-augmented portion of flight. The Mach number at which safe parachute deployment can occur depends on the amplitude of pitch oscillation, so the sensitivity of this metric to the parameterized pitch-damping behavior is determined. Pitch dynamics yielding unacceptable parachute staging conditions are quantified to inform SIAD configuration selection and design. These exploratory results are used to recommend a general strategy for measuring the pitch dynamics of SIAD augmented blunt vehicles in ground testing facilities.