Mclaurin Aerospace places a special emphasis on original research and the systematic, innovation-driven approach to customer success. Our extensive library of staff publications is searchable below. For additional information or to learn more about how our experts can help your concepts come to life, contact us.

AuthorTitlePrimary AuthorCoauthorsTechnology AreasPaper NumberYearPublication LinkConference/JournalAbstracttechnology_area_hfilterpublication_author_hfilter
Orr, Jeb S.The Enduring Legacy of Saturn V Launch Vehicle Flight Dynamics and Control Design Principles and PracticesOrr, Jeb S.Wall, J.H.; Dennehy, C.J.Flight Mechanics and GN&CIAC-19-9-D6.2201970th International Astronautical Congress, Washington, D.C., 21-25 October 2019

(Abstract not yet available)

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Orr, Jeb S.Space Launch System: Sensor Analysis, Modeling, and Test for Robust Propulsion System AutonomyOrr, Jeb S.Flight Mechanics and GN&CAAS 19-1032019AASAAS Guidance, Navigation, and Control Conference

An approach is presented supporting analysis, modeling, and test validation of operational flight instrumentation (OFI) that facilitates critical functions for the Space Launch System (SLS) main propulsion system (MPS). Certain types of OFI sensors were shown to exhibit highly nonlinear and non-gaussian noise characteristics during acceptance testing, motivating the development of advanced modeling and simulation (M&S) capability to support algorithm verification and flight certification. Hardware model and algorithm simulation fidelity was informed by a risk scoring metric; redesign of high-risk algorithms using test-validated sensor models significantly improved their expected performance as evaluated using Monte Carlo acceptance sampling methods. Autonomous functions include closed-loop ullage pressure regulation, pressurant leak detection, and fault isolation for automated safing and crew caution and warning (C&W)

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Orr, Jeb S.Estimation of Coriolis Force and Torque Acting on Ares-1Mackey, R.M.Kulikov, I.K.; Smelyanskiy, V.; Luchinsky, D.; Orr, J.Flight Mechanics and GN&C2011AAS

(Abstract not yet available)

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Alaniz, AbranFault Detection and Isolation Strategy for Redundant Inertial Measurement UnitsZanetti, R.Alaniz, Abran; Breger, L.; Mitchell, I.; Phillips, R.Flight Mechanics and GN&C2014AAS Spaceflight Mechanics, Santa Fe, NM

(Abstract not yet available)

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Alaniz, AbranInternational Space Station US GN&C Attitute Hold Controller Design for Orbiter Repair ManeuverBedrossian, NazarethJang, Jimmy; Alaniz, Abran; Johnson, Michael; Sebelius, Karl; Mesfin, YaredFlight Mechanics and GN&CAIAA 2005-58532005AIAAAIAA Guidance, Navigation, and Control Conference and Exhibit, San Francisco, CA

(Abstract not yet available)

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Alaniz, AbranISS Contingency Attitude Control Recovery Method for Loss of Automatic Thruster ControlBedrossian, NazarethBhatt, Sagar; Alaniz, Abran; McCants, Edward; Nguyen, Louis; Chamitoff, GregFlight Mechanics and GN&C2008AAS31st Annual American Astronomical Society GN&C Meeting, Breckenridge, CO

In this paper, the attitude control issues associated with International Space Station (ISS) loss of automatic thruster control capability are discussed and methods for attitude control recovery are presented. This scenario was experienced recently during Shuttle mission STS-117 and ISS Stage 13A in June 2007 when the Russian GN&C computers, which command the ISS thrusters, failed. Without automatic propulsive attitude control, the ISS would not be able to regain attitude control after the Orbiter undocked. The core issues associated with recovering long-term attitude control using CMGs are described as well as the systems engineering analysis to identify recovery options. It is shown that the recovery method can be separated into a procedure for rate damping to a “safe harbor” gravity gradient stable orientation and a capability to maneuver the vehicle to the necessary initial conditions for long term attitude hold.
A manual control option using Soyuz and Progress vehicle thrusters is
investigated for rate damping and maneuvers. The issues with implementing
such an option are presented and the key issue of closed-loop stability is
addressed. A new non-propulsive alternative to thruster control, Zero Propellant Maneuver (ZPM) attitude control method is introduced and its rate damping and maneuver performance evaluated. It is shown that ZPM can meet the tight attitude and rate error tolerances needed for long term attitude control. A combination of manual thruster rate damping to a “safe harbor” attitude followed by a ZPM to Stage long term attitude control orientation was selected by the Anomaly Resolution Team as the alternate attitude control method for such a contingency.

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Alaniz, AbranAres I Flight Control System DesignJang, Jiann-WoeiAlaniz, Abran; Hall, Robert; Bedrossian, Nazareth; Hall, Charles; Ryan, Stephen; Jackson, MarkFlight Mechanics and GN&CAIAA 2010-84422010AIAAAIAA Guidance, Navigation, and Control Conference, Toronto, Ontario, Canada

The Ares I launch vehicle represents a challenging flex-body structural environment for flight control system design. This paper presents a design methodology for employing numerical optimization to develop the Ares I flight control system. The design objectives include attitude tracking accuracy and robust stability with respect to rigid body dynamics, propellant slosh, and flex. Under the assumption that the Ares I time-varying dynamics and control system can be frozen over a short period of time, the flight controllers are designed to stabilize all selected frozen-time launch control systems in the presence of parametric uncertainty. Flex filters in the flight control system are designed to minimize the flex components in the error signals before they are sent to the attitude controller. To ensure adequate response to guidance command, step response specifications are introduced as constraints in the optimization problem. Imposing these constraints minimizes performance degradation caused by the addition of the flex filters. The first stage bending filter design achieves stability by adding lag to the first structural frequency to phase stabilize the first flex mode while gain stabilizing the higher modes. The upper stage bending filter design gain stabilizes all the flex bending modes. The flight control system designs provided here have been demonstrated to provide stable first and second stage control systems in both Draper Ares Stability Analysis Tool (ASAT) and the MSFC 6DOF nonlinear time domain simulation.

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Alaniz, AbranDesign of Launch Vehicle Flight Control Systems Using Ascent Vehicle Stability Analysis ToolJang, Jiann-WoeiAlaniz, Abran; Hall, Robert; Bedrossian, Nazareth; Hall, Charles; Jackson, MarkFlight Mechanics and GN&CAIAA 2011-66522011AIAAAIAA Guidance, Navigation, and Control Conference, Portland, OR

A launch vehicle represents a complicated flex-body structural environment for flight control system design. The Ascent-vehicle Stability Analysis Tool (ASAT) is developed to address the complicity in design and analysis of a launch vehicle. The design objective for the flight control system of a launch vehicle is to best follow guidance commands while robustly maintaining system stability. A constrained optimization approach takes the advantage of modern computational control techniques to simultaneously design multiple control systems in compliance with required design specs. “Tower Clearance” and “Load Relief” designs have been achieved for liftoff and max dynamic pressure flight regions, respectively, in the presence of large wind disturbances. The robustness of the flight control system designs has been verified in the frequency domain Monte Carlo analysis using ASAT.

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Alaniz, AbranMechanical Slosh Models for Rocket-Propelled SpacecraftJang, Jiann-WoeiAlaniz, Abran; Yang, Lee; Powers, Joseph; Hall, CharlesFlight Mechanics and GN&CAIAA 2013-46512013AIAAAIAA Guidance, Navigation, and Control (GNC) Conference, Boston, MA

Several analytical mechanical slosh models for a cylindrical tank with flat bottom are reviewed. Even though spacecrafts use cylinder shaped tanks, most of those tanks usually have elliptical domes. To extend the application of the analytical models for a cylindrical tank with elliptical domes, the modified slosh parameter models are proposed in this report by mapping an elliptical dome cylindrical tank to a flat top/bottom cylindrical tank while maintaining the equivalent liquid volume. For the low Bond number case, the low-g slosh models were also studied. Those low-g models can be used for Bond number > 10. The current low-g slosh models were also modified to extend their applications for the case that liquid height is smaller than the tank radius. All modified slosh models are implemented in MATLAB m-functions and are collected in the developed MST (Mechanical Slosh Toolbox).

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Purinton, David C.Effects of Slag Ejection on Solid Rocket Motor PerformanceWhitesides, R.Purinton, David C.; Hengel, John; Skelley, StephenAerodynamics & VibroacousticsAIAA 95-2724, 1995 Solid Rocket Motor Paper of the Year1995AIAA31st Joint AIAA/ASME/SAE/ASE Propulsion Conference and Exhibit, San Diego, CA

In past firings of the Reusable Solid Rocket Motor (RSRM) both static test and flight motors have shown small pressure perturbations occurring primarily between 65 and 80 seconds. A joint NASA/Thiokol team investigation concluded that the cause of the pressure perturbations was the periodic ingestion and ejection of molten aluminum oxide slag from the cavity around the submerged nozzle nose which tends to trap and collect individual aluminum oxide droplets from the approach flow. The conclusions of the team were supported by numerous data and observations from special tests including high speed photographic films, real time radiography, plume calorimeters, accelerometers, strain gauges, nozzle TVC system force gauges, and motor pressure and thrust data. A simplistic slag ballistics model was formulated to relate a given pressure perturbation to a required slag quantity. Also, a cold flow model using air and water was developed to provide data on the relationship between the slag flow rate and the chamber pressure increase. Both the motor and the cold flow model exhibited low frequency oscillations in conjunction with periods of slag ejection. Motor and model frequencies were related to scaling parameters. The data indicate that there is a periodicity to the slag entrainment and ejection phenomena which is possibly related to organized oscillations from instabilities in the dividing streamline shear layer which impinges on the underneath surface of the nozzle.

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Purinton, David C.Design of a Subscale Propellant Slag Evaluation Motor Using Two-Phase Fluid Dynamic AnalysisWhitesides, R.Dill, Richard; Purinton, David C.; Sambamurthi, JayAerodynamics & VibroacousticsAIAA 96-27801996AIAA32nd Joint AIAA/ASME/SAE/ASE Propulsion Conference and Exhibit, Lake Buena Vista, FL

Small pressure perturbations in the Space Shuttle Reusable Solid Rocket Motor (RSRM) are caused by the periodic expulsion of molten aluminum oxide slag from a pool that collects in the aft end of the motor around the submerged nozzle nose during the last half of motor operation. It is suspected that some motors produce more slag than others due to differences in aluminum oxide agglomerate particle sizes that may relate to subtle differences in propellant ingredient characteristics such as particle size distributions or processing variations. A subscale motor experiment was designed to determine the effect of propellant ingredient characteristics on the propensity for slag production. An existing 5 inch ballistic test motor was selected as the basic test vehicle. The standard converging/diverging nozzle was replaced with a submerged nose nozzle design to provide a positive trap for the slag that would increase the measured slag weights. Two-phase fluid dynamic analyses were performed to develop a nozzle nose design that maintained similitude in major flow field features with the full scale RSRM. Detailed predictions for slag accumulation weights during motor burn compared favorably with slag weight data taken from defined zones in the subscale motor and nozzle.

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Purinton, David C.Application of Two-Phase CFD Analysis to the Evaluation of Asbestos-Free Insulation in the RSRMWhitesides, R.Dill, Richard; Purinton, David C.Aerodynamics & VibroacousticsAIAA 1997-2861997AIAA33rd Joint AIAA/ASME/SAE/ASE Propulsion Conference and Exhibit, Seattle, WA

The first full scale test of asbestos-free case insulation materials being developed for the Space Shuttle Reusable Solid Rocket Motor (RSRM) occurred with the static firing of FSM-5 Materials containing a Kevlar substitute fiber were tested in the aft dome of the motor. The substitute materials experienced higher than expected erosion in a narrow circumferential zone close to the case/nozzle joint. The post fire inspection revealed an eroded depression in the insulation surface which extended around the entire circumference of the case. The erosion in this zone was higher than previously experienced with the carbon fiber filled EPDM insulation currently used at this particular location. Two-phase fluid dynamic analyses were conducted to determine the structure of the flow field in the recirculation region underneath the submerged nozzle nose and to define the gas flow and particle impingement environments along the surface of the aft case dome insulation. The results indicated that the non-uniform erosion was due to particles impacting underneath the nozzle nose and forming a sheet of molten aluminum oxide, or slag. The molten slag flows afterwards along the underneath nozzle nose surface as this is the direction of the near surface velocity vectors during the last half of motor burn. This slag layer is then sheared from the nozzle cowl/boot ring surface at the aft end of the cavity and impacts the aft dome case insulation at the location of the severe erosion. This phenomenon happens in every motor but the asbestos-free insulation appears less tolerant to a direct slag impingement environment.

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Purinton, David C.Aerodynamic Characteristics of Ribbon Stabilized GrenadesAuman, LamarDahlke, C.; Purinton, DavidAerodynamics & VibroacousticsAIAA 2000-02702000AIAA38th AIAA Aerospace Sciences Meeting, Reno, NV

An extensive experimental program has been conducted to determine the aerodynamic characteristics of grenade ribbon stabilizers. While data has been acquired from vertical and horizontal wind tunnel tests, free-flight drop tests, and free-flight gun tests, this paper presents only the data from the horizontal wind tunnel test. During this test, both static and dynamic free-yaw data were obtained at speeds ranging from 90 to 180 feet/second. The test obtained axial force, side force, yawing moment and pitching moment while the grenade was free to yaw, or while statically fixed at a given yaw angle. Analysis of the static and dynamic forces and moments indicates that there are four types of ribbon induced oscillatory motion. These types are presented, as is the zero-yaw drag as a function of ribbon length and ribbon width.

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Purinton, David C.Real-Time Flight Vehicle Simulations: Increasing Speed While Preserving AccuracyKeeter, T.M.Purinton, David C.Aerodynamics & Vibroacoustics20022002 Interservice/Industry Training, Simulation, and Education Conference

(Abstract not yet available)

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Wall, DavidCounter-Current Shear Layer Vortex GenerationThompson, RobertWall, DavidAerodynamics & Vibroacoustics200859th AIAA Southeastern Region II Student Conference, Cape Canaveral, FL

(Abstract not yet available)

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Wall, DavidInitial Development of Acetone Laser Induced Fluorescence (LIF) for Aero-OpticsReid, JohnWall, David; Lynch, Kyle; Thurow, BrianAerodynamics & VibroacousticsAIAA 2009-42952009AIAA39th AIAA Fluid Dynamics Conference, San Antonio, TX

(Abstract not yet available)

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Purinton, David C.Aerodynamic Characterization and Simulation of a Solid Rocket Booster During Reentry FlightPurinton, David C.Blevins, John A.; Pritchett, Victor; Haynes, Davy; Carpenter, MikeAerodynamics & VibroacousticsAIAA 2011-142011AIAA49th AIAA Aerospace Sciences Meeting, Orlando, FL

(Abstract not yet available)

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Purinton, David C.Aerodynamic Tests of the Space Launch System for Database DevelopmentPritchett, VictorMayle, Melody; Blevins, John A.; Crosby, William; Purinton, David C.Aerodynamics & VibroacousticsAIAA 2014-12562014AIAA52nd AIAA Aerospace Sciences Meeting, National Harbor, MD

(Abstract not yet available)

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Alaniz, AbranShuttle Stability and Control During the Orbiter Repair ManeuverHall, RobertBarrington, Ray; Kirchwey, Kim; Alaniz, Abran; Grigoriadis, KarolosFlight Mechanics and GN&CAIAA 2005-58522005AIAAAIAA Guidance, Navigation, and Control Conference and Exhibit, San Francisco, CA

(Abstract not yet available)

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Orr, Jeb S.Robust Control of Lunar Spacecraft Powered Descent Using a Second Order Sliding Mode TechniqueOrr, Jeb S.Shtessel, Yuri B.Flight Mechanics and GN&CAIAA 2008-68152008AIAAAIAA Guidance, Navigation, and Control Conference, Honolulu, HI

(Abstract not yet available)

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Orr, Jeb S.Robust Lunar Spacecraft Autopilot Design Using High Order Sliding Mode ControlOrr, Jeb S.Shtessel, Yuri B.Flight Mechanics and GN&CAIAA 2009-61822009AIAAAIAA Guidance, Navigation, and Control Conference, Chicago, IL

(Abstract not yet available)

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Orr, Jeb S.State Space Implementation of Linear Perturbation Dynamics Equations for Flexible Launch VehiclesOrr, Jeb S.Johnson, Matthew; Wetherbee, Jonathan; McDuffie, JamesFlight Mechanics and GN&CAIAA 2009-59622009AIAAAIAA Guidance, Navigation, and Control Conference, Chicago, IL

(Abstract not yet available)

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Orr, Jeb S.Parametric Optimization of Ares I Propellant Slosh Characteristics Using Frequency Response CriteriaOrr, Jeb S.Hall, CharlesFlight Mechanics and GN&CAIAA 2009-59632009AIAAAIAA Guidance, Navigation, and Control Conference, Chicago, IL

(Abstract not yet available)

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Orr, Jeb S.Flexible Modes Control Using Sliding Mode Observers: Application to Ares IShtessel, YuriHall, Charles; Baev, Simon; Orr, Jeb S.Flight Mechanics and GN&CAIAA 2010-75652010AIAAAIAA Atmospheric Flight Mechanics Conference, Toronto, Ontario, Canada

(Abstract not yet available)

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Orr, Jeb S.A Coupled Aeroelastic Model for Launch Vehicle Stability AnalysisOrr, Jeb S.Flight Mechanics and GN&CAIAA 2010-76422010AIAAAIAA Atmospheric Flight Mechanics Conference, Toronto, Ontario, Canada

(Abstract not yet available)

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Orr, Jeb S.Linear Approximation to Optimal Control Allocation for Rocket Nozzles with Elliptical ConstraintsOrr, Jeb S.Wall, John H.Flight Mechanics and GN&CAIAA 2011-65002011AIAAAIAA Guidance, Navigation, and Control Conference, Portland, OR

(Abstract not yet available)

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Orr, Jeb S.Lunar Spacecraft Powered Descent Control Using Higher-Order Sliding Mode TechniquesOrr, Jeb S.Shtessel, Yuri B.Flight Mechanics and GN&C2012Journal of the Franklin Institute, Vol. 349, Issue 2, March 2012, Pages 476-492

Robust performance of a flight control system in the presence of parametric uncertainty and external disturbances is of paramount importance to a successful planetary exploration program. The present research is concerned with the design of an autopilot that uses high-order sliding mode (HOSM) control principles so as to enhance the robustness properties of a lunar landing vehicle during the approach phase of powered descent. The design technique is applied to a high-fidelity simulation of the Apollo Lunar Module (LM). The design efficiently utilizes both the reaction control system (RCS) actuators and the severely rate-limited gimbal drive actuator (GDA) to effect smooth detection and compensation of sensed angular acceleration disturbances about the vehicle’s control axes. The integration of a HOSM control law for the RCS effectors with a HOSM disturbance observer is shown to provide performance comparable to that of the heritage autopilot and may also avoid some difficulties encountered in the Apollo flights. Performance is maintained with the controller implemented in discrete time in the presence of a realistic vehicle and sensor model, demonstrating a unique application of sliding mode control to a complex aerospace system.

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Orr, Jeb S.Robust, Practical Adaptive Control for Launch VehiclesOrr, Jeb S.Van Zwieten, Tannen S.Flight Mechanics and GN&CAIAA 2012-45492012AIAAAIAA Guidance, Navigation, and Control Conference, Minneapolis, MN

(Abstract not yet available)

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Orr, Jeb S.Elastic Model Transitions Using Quadratic Inequality Constrained Least SquaresOrr, Jeb S.Flight Mechanics and GN&CAIAA 2012-45612012AIAAAIAA Modeling and Simulation Technologies Conference, Minneapolis, MN

(Abstract not yet available)

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Orr, Jeb S.Optimal Recursive Digital Filters for Active Bending StabilizationOrr, Jeb S.Flight Mechanics and GN&CAAS 13-0542013AASAmerican Astronautical Society Guidance, Navigation, and Control Conference, Breckenridge, CO

In the design of flight control systems for large flexible boosters, it is common practice to utilize active feedback control of the first lateral structural bending mode so as to suppress transients and reduce gust loading. Typically, active stabilization or phase stabilization is achieved by carefully shaping the loop transfer function in the frequency domain via the use of compensating filters combined with the frequency response characteristics of the nozzle/actuator system. In this paper we present a new approach for parametrizing and determining optimal loworder recursive linear digital filters so as to satisfy phase shaping constraints for
bending and sloshing dynamics while simultaneously maximizing attenuation in other frequency bands of interest, e.g. near higher frequency parasitic structural modes. By parametrizing the filter directly in the z-plane with certain restrictions, the search space of candidate filter designs that satisfy the constraints is restricted to stable, minimum phase recursive low-pass filters with well-conditioned coefficients. Combined with optimal output feedback blending from multiple rate gyros, the present approach enables rapid and robust parametrization of autopilot bending filters to attain flight control performance objectives. Numerical results are presented that illustrate the application of the present technique to the development of rate gyro filters for an exploration-class multiengined space launch vehicle.

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Orr, Jeb S.Adaptive Augmenting Control Flight Characterization Experiment on an F/A-18VanZwieten, Tannen S.Gilligan, Eric T.; Wall, John H.; Orr, Jeb S.; Miller, Christopher J.; Hanson, Curtis E.Flight Mechanics and GN&CAAS 14-0522014AASAmerican Astronautical Society Guidance, Navigation, and Control Conference, Breckenridge, CO

The NASA Marshall Space Flight Center (MSFC) Flight Mechanics and Analysis
Division developed an Adaptive Augmenting Control (AAC) algorithm for launch vehicles that improves robustness and performance by adapting an otherwise welltuned classical control algorithm to unexpected environments or variations in vehicle dynamics. This AAC algorithm is currently part of the baseline design for the SLS Flight Control System (FCS), but prior to this series of research flights it was the only component of the autopilot design that had not been flight tested. The Space Launch System (SLS) flight software prototype, including the adaptive component, was recently tested on a piloted aircraft at Dryden Flight Research Center (DFRC) which has the capability to achieve a high level of dynamic similarity to a launch vehicle. Scenarios for the flight test campaign were designed
specifically to evaluate the AAC algorithm to ensure that it is able to achieve the expected performance improvements with no adverse impacts in nominal or nearnominal scenarios. Having completed the recent series of flight characterization experiments on DFRC’s F/A-18, the AAC algorithm’s capability, robustness, and reproducibility, have been successfully demonstrated. Thus, the entire SLS control architecture has been successfully flight tested in a relevant environment. This has increased NASA’s confidence that the autopilot design is ready to fly on the SLS
Block I vehicle and will exceed the performance of previous architectures.

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Orr, Jeb S.Space Launch System Implementation of Adaptive Augmenting ControlWall, John H.Orr, Jeb S.; Van Zwieten, Tannen S.Flight Mechanics and GN&CAAS 14-0512014AASAmerican Astronautical Society Guidance, Navigation, and Control Conference, Breckenridge, CO

Given the complex structural dynamics, challenging ascent performance requirements, and rigorous flight certification constraints owing to its manned capability, the NASA Space Launch System (SLS) launch vehicle requires a proven thrust vector control algorithm design with highly optimized parameters to provide stable and high-performance flight. On its development path to Preliminary Design Review (PDR), the SLS flight control system has been challenged by significant vehicle flexibility, aerodynamics, and sloshing propellant. While the design has been able to meet all robust stability criteria, it has done so with little excess margin. Through significant development work, an Adaptive Augmenting Control (AAC) algorithm has been shown to extend the envelope of failures and flight anomalies the SLS control system can accommodate while maintaining a direct link to flight control stability criteria such as classical gain and phase margin. In this paper, the work performed to mature the AAC algorithm as a baseline component of the SLS flight control system is presented. The progress to date has brought the algorithm
design to the PDR level of maturity. The algorithm has been extended to augment the full SLS digital 3-axis autopilot, including existing load-relief elements, and the necessary steps for integration with the production flight software prototype have been implemented. Several updates which have been made to the adaptive algorithm to increase its performance, decrease its sensitivity to expected external commands, and safeguard against limitations in the digital implementation are discussed with illustrating results. Monte Carlo simulations and selected stressing case results are also shown to demonstrate the algorithm’s ability to increase the robustness of the integrated SLS flight control system.

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Orr, Jeb S.Space Launch System Ascent Flight Control DesignOrr, Jeb S.Wall, John H.; Van Zwieten, Tannen S.; Hall, Charles, E.Flight Mechanics and GN&CAAS 14-0382014AASAmerican Astronautical Society Guidance, Navigation, and Control Conference, Breckenridge, CO

A robust and flexible autopilot architecture for NASA’s Space Launch System
(SLS) family of launch vehicles is presented. The SLS configurations represent a potentially significant increase in complexity and performance capability when compared with other manned launch vehicles. It was recognized early in the program that a new, generalized autopilot design should be formulated to fulfill the needs of this new space launch architecture. The present design concept is intended to leverage existing NASA and industry launch vehicle design experience and maintain the extensibility and modularity necessary to accommodate multiple vehicle configurations while relying on proven and flight-tested control design
principles for large boost vehicles. The SLS flight control architecture combines a digital three-axis autopilot with traditional bending filters to support robust active or passive stabilization of the vehicle’s bending and sloshing dynamics using optimally blended measurements from multiple rate gyros on the vehicle structure. The algorithm also relies on a pseudo-optimal control allocation scheme to maximize the performance capability of multiple vectored engines while accommodating throttling and engine failure
contingencies in real time with negligible impact to stability characteristics. The architecture supports active in-flight disturbance compensation through the use of nonlinear observers driven by acceleration measurements. Envelope expansion and robustness enhancement is obtained through the use of a multiplicative forward gain modulation law based upon a simple model reference adaptive control scheme.

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Orr, Jeb S.High-Efficiency Thrust Vector Control AllocationOrr, Jeb S.Slegers, Nathan J.Flight Mechanics and GN&C2014AIAAJournal of Guidance, Control, and Dynamics, Vol. 37, No. 2 (2014), pp. 374-382

A generalized approach to the allocation of redundant thrust vector slew commands for multi-actuated launch vehicles is presented, where deflection constraints are expressed as omniaxial or elliptical deflection limits in gimbal axes. More importantly than in the aircraft control allocation problem, linear allocators (pseudoinverses) are preferred for large booster applications to facilitate accurate prediction of the control-structure interaction resulting from thrust vectoring effects. However, strictly linear transformations for the allocation of redundant controls cannot, in general, access all of the attainable moments for which there is a set of control effector positions that satisfies the constraints. In this paper, the control allocation efficiency of a certain class of linear allocators subject to multiple quadratic constraints is analyzed, and a novel single-pass control allocation scheme is proposed that augments the pseudoinverse near the boundary of the attainable set. The controls are determined over a substantial volume of the attainable set using only a linear transformation; as such, the algorithm maintains compatibility with frequency-domain approaches to the analysis of the vehicle closed-loop elastic stability. Numerical results using a model of a winged reusable booster system illustrate the proposed technique’s ability to access a larger fraction of the attainable set than a pseudoinverse alone.

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Orr, Jeb S.Lattice Boltzmann Method for Simulation of Propellant Dynamics in Microgravity, Phase IIOrr, Jeb S.Powers, J.Flight Mechanics and GN&CTechnical report ESSSA-FY15-17182014

(Abstract not yet available)

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Orr, Jeb S.Lattice Boltzmann Method for Simulation of Propellant Dynamics in MicrogravityOrr, Jeb S.Powers, J.; Yang, H.Q.Flight Mechanics and GN&CTechnical report ESSSA-FY14-18072014

(Abstract not yet available)

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Orr, Jeb S.A Comprehensive Analysis of the X-15 Flight 3-65 AccidentOrr, Jeb S.Barshi, I.; Statler, I.; Dennehy, N.Flight Mechanics and GN&CNESC RP-14-009572014NESCNASA Engineering and Safety Center

(Abstract not yet available)

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Orr, Jeb S.Flight Testing of the Space Launch System (SLS) Adaptive Augmenting Control (AAC) Algorithm on an F/A-18VanZwieten, Tannen S.Dennehy, Cornelius J.; Hanson, Curtis E.; Wall, John h.; Miller, Chris J.; Gilligan, Eric T.; Orr, Jeb S.Flight Mechanics and GN&CNESC RP-13-008472014NESCNASA Engineering and Safety Center

(Abstract not yet available)

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Orr, Jeb S.The X-15 3-65 Accident: An Aircraft Systems and Flight Control PerspectiveOrr, Jeb S.Statler, I.; Barshi, I.Flight Mechanics and GN&C2014Proceedings of the 7th Conference of the International Association for the Advancement of Space Safety, Friedrichshafen, Germany

Despite the NASA X-15 program’s outstanding success in developing and operating the first manned hypersonic research platform, the program suffered a fatal accident on November 15, 1967, when X-15-3, the only aircraft outfitted with advanced pilot displays and an adaptive flight control system, was lost after entering uncontrolled flight at an altitude of 230,000 feet and a velocity near Mach 5. The pilot, Major Michael J. Adams, was incapacitated by the aircraft accelerations and was killed either during the ensuing breakup or upon ground impact. In light of mitigating risk to current and emerging manned aerospace vehicles, a comprehensive systems level analysis of the accident is presented with a focus on the electrical power, flight control, and instrumentation failures that affected not only the vehicle dynamics but substantially impacted the pilot decisions that led to an inevitable loss of control. Insights based on reconstructed flight data as well as analysis and simulation of the X-15’s unique adaptive control system, yield new conclusions about the reasons for the control system’s anomalous behavior and the system-level interactions and human-machine interface design oversights that led to the accident.

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Orr, Jeb S.In-Flight Suppression of a Destabilized F/A-18 Structural Mode Using the Space Launch System Adaptive Augmenting Control SystemWall, John H.Miller, Christopher J.; Hanson, Curtis E.; Van Zwieten, Tannen S.; Orr, Jeb S.; Gilligan, EricFlight Mechanics and GN&CAIAA-2015-17752015AIAA2015 AIAA Guidance, Navigation, and Control Conference, Kissimmee, FL

(Abstract not yet available)

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Orr, Jeb S.Launch Vehicle Manual Steering with Adaptive Augmenting Control: In-Flight Evaluations of Adverse Interactions Using a Piloted AircraftHanson, Curtis E.Miller, Christopher J.; Van Zwieten, Tannen S.; Gilligan, Eric; Orr, Jeb; Wall, John H.Flight Mechanics and GN&CAIAA-2015-17762015AIAA2015 AIAA Guidance, Navigation, and Control Conference, Kissimmee, FL

(Abstract not yet available)

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Orr, Jeb S.Lattice Boltzmann Method for Spacecraft Propellant Slosh SimulationOrr, Jeb S.Powers, Joseph F.; Yang, Hong Q.Flight Mechanics and GN&CAAS 15-0912015AASAAS Guidance, Navigation, and Control Conference, Breckenridge, CO

A scalable computational approach to the simulation of propellant tank sloshing dynamics in microgravity is presented. In this work, we use the lattice Boltzmann equation (LBE) to approximate the behavior of two-phase,
single-component isothermal flows at very low Bond numbers. Through the use of a non-ideal gas equation of state and a modified multiple relaxation time (MRT) collision operator, the proposed method can simulate thermodynamically consistent phase transitions at temperatures and density ratios consistent with typical spacecraft cryogenic propellants, for example, liquid oxygen. Determination of the tank forces and moments relies upon the global momentum conservation of the fluid domain, and a parametric wall wetting model allows tuning of the free surface contact angle. Development of the interface is implicit and no interface tracking approach is required. Numerical examples illustrate the method’s application to predicting bulk fluid motion including lateral propellant slosh in low-g conditions.

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Orr, Jeb S.Airborne Simulation of Launch Vehicle DynamicsMiller, Christopher J.Miller, Christopher J.; Orr, Jeb S.; Hanson, Curtis E.; Gilligan, Eric T.Flight Mechanics and GN&CAAS 15-0972015AASAAS Guidance, Navigation, and Control Conference, Breckenridge, CO

In this paper we present a technique for approximating the short-period dynamics of an exploration-class launch vehicle during flight test with a high-performance surrogate aircraft in relatively benign endoatmospheric flight conditions. The surrogate vehicle relies upon a nonlinear dynamic inversion scheme with proportional-integral feedback to drive a subset of the aircraft states into coincidence with the states of a time-varying reference model that simulates the unstable rigid body dynamics, servodynamics, and parasitic elastic and sloshing dynamics of the launch vehicle. The surrogate aircraft flies a constant pitch rate trajectory to approximate the boost phase gravity turn ascent, and the aircraft’s closed-loop bandwidth is sufficient to simulate the launch vehicle’s fundamental lateral bending and sloshing modes by exciting the rigid body dynamics of the aircraft. A novel control allocation scheme is employed to utilize the aircraft’s relatively fast control effectors in inducing various failure modes for the purposes of evaluating control system performance. Sufficient dynamic similarity is achieved such that the control system under evaluation is configured for the full-scale vehicle with no changes to its parameters, and pilot-control system interaction studies can be performed to characterize the effects of guidance takeover during boost. High-fidelity simulation and flight-test results are presented that demonstrate the efficacy of the design in simulating the Space Launch System (SLS) launch vehicle dynamics using the National Aeronautics and Space Administration (NASA) Armstrong Flight Research Center Fullscale
Advanced Systems Testbed (FAST), a modified F/A-18 airplane (McDonnell Douglas, now The Boeing Company, Chicago, Illinois), over a range of scenarios designed to stress the SLS’s Adaptive Augmenting Control (AAC) algorithm.

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Orr, Jeb S.Analysis of the X-15 Flight 3-65-97 Divergent Limit-Cycle OscillationOrr, Jeb S.Dennehy, Cornelius J.Flight Mechanics and GN&C2016AIAAAIAA J. Aircraft, Vol. 54, No. 1 (2016)

A brief history of the X-15-3 adaptive control system and an analysis of the destructive limit-cycle oscillation that occurred during its final November 1967 flight are presented. The X-15 was a piloted single-seat rocket-propelled hypersonic research aircraft operated by the NASA Flight Research Center from 1959 until 1968. Due to the limited information previously available in the public domain and the 1968 decision by the accident investigation board to forego detailed analysis of the adaptive control system’s role in the accident, it was widely assumed in the adaptive controls community that an anomalous behavior of the adaptive component caused the loss of control. Notwithstanding the complex human factors and subsystem failures that contributed to the accident, it is shown that the adaptation dynamics were not a causal factor. The limit cycle observed in the flight data is reproduced in a nonlinear time-domain simulation. Describing function analysis reveals that the instability was caused by a latent design error in the inner-loop structural filters that did not account for the nonlinear behavior of the X-15 servoactuator under rate saturation when coupled with the lightly damped aircraft longitudinal mode at high Mach numbers.

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Orr, Jeb S.The Human Factors of an Early Space Accident: Flight 3-65 of the X-15Barshi, I.Barshi, I.; Orr, Jeb S.; Statler, I.Flight Mechanics and GN&C2016Proceedings of the 7th Conference of the International Association for the Advancement of Space Safety, Friedrichshafen, Germany

(Abstract not yet available)

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Eppard, William M.Flux-Split Methods in Non-Equilibrium FlowGrossman, B.Grossman, B.; Cinnella, P.; Eppard, W.M.Computational Fluid Dynamics1991Proceedings of the International Conference on Mathematical Models and Numerical Methods in Continuum Mechanics, ed. V. M. Fomin, Novosibirsk, U.S.S.R., May 1991.

(Abstract not yet available)

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Eppard, William M.Calculation of Hypersonic Shock Structure Using Flux-Split AlgorithmsEppard, William M.Grossman, B.Computational Fluid DynamicsICAM Report 91-07-041991ICAMVirginia Polytechnic Institute and State University, Blacksburg, VA

(Abstract not yet available)

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Eppard, William M.Algorithms for Non-Equilibrium Hypersonic FlowsGrossman, B.Grossman, B.; Cinnella, P.; Eppard, W.M.Computational Fluid Dynamics1991Proceedings of the 4th International Symposium on Computational Fluid Dynamics, pp. 443–448, Davis CA, Sept. 1991.

(Abstract not yet available)

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Eppard, William M.New Developments Pertaining to Algorithms for Non-Equilibrium Hypersonic FlowsGrossman, B.Grossman, B.; Cinnella, P.; Eppard, W.M.Computational Fluid Dynamics1992Computational Fluid Dynamics J., No. 2, July 1992, pp. 175–186

(Abstract not yet available)

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Eppard, William M.Kinetic Flux-Vector Splitting for Flows in Chemical and Thermal Non-EquilibriumGrossman, B.Grossman, B.Computational Fluid DynamicsPaper CI-619921992 Division of Fluid Mechanics Annual Meeting, American Physical Society, Nov. 1992, Bulletin of APS, 37, No. 8, 1992, p. 1736

(Abstract not yet available)

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Applebaum, Michael P.Application of Thermo-Chemical Models on Unstructured MeshesApplebaum, Michael P.Mitchell, C.R.; Walters, R.W.; McGrory, W.D.Computational Fluid DynamicsAIAA 93-08951993AIAA31st Aerospace Sciences Meeting, Reno, NV

(Abstract not yet available)

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Eppard, William M.An Upwind, Kinetic Flux-Vector Splitting Method for Flows in Chemical and Thermal Non-EquilibriumEppard, William M.Grossman, B.Computational Fluid DynamicsAIAA 93-08941993AIAAAIAA 31st Aerospace Sciences Meeting, Reno, NV

(Abstract not yet available)

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Applebaum, Michael P.Finite-Rate Chemistry for Generalized DiscretizationsApplebaum, Michael P.Mitchell, C.R.; Walters, R.W.; McGrory, W.D.Computational Fluid DynamicsAIAA-93-0895199331st Aerospace Sciences Meeting, Reno, NV

(Abstract not yet available)

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Eppard, William M.A Multi-Dimensional Kinetic-Based Upwind Solver for the Euler EquationsEppard, William M.Grossman, B.Computational Fluid DynamicsAIAA 93-3303-CP1993AIAA11th AIAA Computational Fluid Dynamics Conference, Orlando, FL

(Abstract not yet available)

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Applebaum, Michael P.Unstructured Technology for High Speed Flow SimulationsApplebaum, Michael P.Computational Fluid Dynamics1994Ph.D. Dissertation, VPI&SU

(Abstract not yet available)

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Hall, Leslie H.Aerodynamic Effects Due to Body Modifications on a Tube Launched Tactical MissileKretzschmar, RichardKretzschmar, Richard; Mallette, Stephen; Deep, RaymondComputational Fluid DynamicsAIAA 95-1896-CP1995AIAA13th Applied Aerodynamics Conference, San Diego, CA

(Abstract not yet available)

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Hall, Leslie H.Aerodynamic Characteristics of Wrap Around Fins on a Tube Launched Tactical MissileKretzschmar, RichardKretzschmar, Richard; Mallette, Stephen; Deep, RaymondComputational Fluid DynamicsAIAA 95-18971995AIAA13th Applied Aerodynamics Conference, San Diego, CA

(Abstract not yet available)

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Applebaum, Michael P.A Three Dimensional Real Gas Navier-Stokes Method for Unstructured MeshesApplebaum, Michael P.Walters, R.W.; McGrory, W.D.Computational Fluid DynamicsAIAA 95-951995AIAAAIAA 33rd Aerospace Sciences Meeting, Reno, NV

(Abstract not yet available)

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Eppard, William M.A Numerical Investigation of Catalytic-Wall Effects on Combustion of High-Speed Flows using GASP Version 3Eppard, William M.Mawid, M.A.; Sekar, B.Computational Fluid DynamicsJANNAF1996Joint Propulsion and Joint Subcommittee Meetings

(Abstract not yet available)

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Hall, Leslie H.An Unsteady Multi-Body Analysis Technique for Missile Staging Events Using Enriched Structured GridsHall, Leslie H.Mitchell, C.R.Computational Fluid Dynamics1996First AFOSR Conference on Dynamic Motion CFD

(Abstract not yet available)

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Hall, Leslie H.An Unsteady Simulation Technique for Missile Guidance and Control ApplicationsHall, Leslie H.Mitchell, C.R.; Parthasarathy, V.Computational Fluid DynamicsAIAA 97-06361997AIAA35th Aerospace Sciences Meeting and Exhibit, Reno, NV

(Abstract not yet available)

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Hall, Leslie H.Validation of an Automated Chimera/6-DOF Methodology for Multiple Moving Body ProblemsHall, Leslie H.Parthasarathy, V.Computational Fluid DynamicsAIAA 98-07531998AIAA36th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV

(Abstract not yet available)

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Eppard, William M.Using Sensitivity Equations for Chemically Reacting FlowsGodfrey, Andrew G.Cliff, Eugene M.Computational Fluid DynamicsAIAA 98-48051998AIAA7th AIAA/USAF/NASA/ISSMO Symposium on Multidisciplinary Analysis and Optimization, St. Louis, MO

(Abstract not yet available)

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Hall, Leslie H.Navier-Stokes/6-DOF Analysis of the JDAM Store Separation from the F/A-18C AircraftHall, Leslie H.Computational Fluid DynamicsAIAA 99-01211999

(Abstract not yet available)

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Eppard, William M.Recent Advances in Numerical Techniques for the Design and Analysis of COIL SystemsEppard, William M.McGrory, William; Godfrey, A.; Cliff, E; Borggaard, J.Computational Fluid DynamicsAIAA 2000-25762000AIAA31st AIAA Plasmadynamics and Lasers Conference, Denver, CO

(Abstract not yet available)

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Hall, Leslie H.Aerodynamic Predictions of Pitch and Roll Control for Canard-Controlled MissilesLanders, MichaelAuman, LamarComputational Fluid DynamicsAIAA 00-45162000AIAA18th Applied Aerodynamics Conference, Denver, CO

(Abstract not yet available)

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Hall, Leslie H.Rolling Airframe Missile Aerodynamic Predictions Using a Chimera Approach for Dithering CanardsHall, Leslie H.Computational Fluid DynamicsAIAA 02-04052002AIAA40th AIAA Aerospace Science Meeting & Exhibit, Reno, NV

(Abstract not yet available)

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Hall, Leslie H.Chimera Moving Body Methodology for Rolling Airframe Missile Simulation with Dithering CanardsHall, Leslie H.Computational Fluid DynamicsAIAA 02-28012002AIAA20th AIAA Applied Aerodynamics Conference, St. Louis, MO

(Abstract not yet available)

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Applebaum, Michael P., Eppard, William M.The Effects of Water-Vapor Condensation and Surface Catalysis on COIL PerformanceEppard, William M.McGrory, WilliamComputational Fluid DynamicsAIAA 2002-21322002AIAA33rd AIAA Plasma Dynamics and Lasers Conference, Maui, HI

(Abstract not yet available)

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Hall, Leslie H.Deflectable Nose and Canard Controls for a Fin-Stabilized Projectile at Supersonic and Hypersonic SpeedsLanders, MichaelAuman, Lamar; Vaughn, MiltonAIAA 03-38052003AIAA21st AIAA Applied Aerodynamics Conference, Orlando, FL

(Abstract not yet available)

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Hall, Leslie H.Simulation of Missile with Spinning Tail Fin Using Chimera Moving Body MethodologyHall, Leslie H.Computational Fluid DynamicsAIAA 04-12492004AIAA42nd AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV

(Abstract not yet available)

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Applebaum, Michael P., Eppard, William M., Hall, Leslie H.Computational Simulation Techniques of Panel Fairing Jettison from a Launch Vehicle SystemHall, Leslie H.Mitchell, C.R.Computational Fluid DynamicsJANNAF 9592008

(Abstract not yet available)

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Applebaum, Michael P., Eppard, William M., Hall, Leslie H.Cartesian Euler Code Application for Launch Vehicle SystemsHall, Leslie H.Blevins, John A.Computational Fluid DynamicsAIAA 2011-11132011AIAA49th AIAA Aerospace Sciences Meeting, Orlando, FL

(Abstract not yet available)

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Applebaum, Michael P., Eppard, William M., Hall, Leslie H.Debris Transport Modeling Techniques on Launch Vehicle SystemsHall, Leslie H.Computational Fluid DynamicsAIAA 2011-11122011AIAA49th AIAA Aerospace Sciences Meeting, Orlando, FL

(Abstract not yet available)

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Applebaum, Michael P., Eppard, William M., Hall, Leslie H.Multi-Species Effects for Plume Modeling on Launch Vehicle SystemsHall, Leslie H.Computational Fluid DynamicsAIAA 2011-10532011AIAA49th AIAA Aerospace Sciences Meeting, Orlando, FL

(Abstract not yet available)

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Applebaum, Michael P., Eppard, William M., Hall, Leslie H.Protuberance Aerodynamic Loads for Space Launch Vehicle Systems using CFDApplebaum, Michael P.Blevins, John A.Computational Fluid DynamicsAIAA 2011-36492011AIAA29th AIAA Applied Aerodynamics Conference, Honolulu, HI

(Abstract not yet available)

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Applebaum, Michael P., Eppard, William M., Hall, Leslie H.Protuberance Aerodynamic Loads for Space Launch Vehicle Systems Using Computational Fluid DynamicsApplebaum, Michael P.Blevins, John A.Computational Fluid Dynamics2012Journal of Spacecraft and Rockets, Vol. 49, No. 5 (2012), pp. 779-787

(Abstract not yet available)

cfd-pubsapplebaum-michael-p eppard-william-m hall-leslie-h
Applebaum, Michael P., Eppard, William M., Hall, Leslie H.Multispecies Effects for Plume Modeling on Launch Vehicle SystemsApplebaum, Michael P.Computational Fluid Dynamics2012Journal of Spacecraft and Rockets, Vol. 49, No. 5 (2012), pp. 770-778

(Abstract not yet available)

cfd-pubsapplebaum-michael-p eppard-william-m hall-leslie-h
Applebaum, Michael P., Eppard, William M., Hall, Leslie H., Purinton, David C.Development of an Aerodynamic Analysis Method and Database for the SLS Service Module Panel Jettison Event Utilizing Inviscid CFD and MATLABApplebaum, Michael P.Blevins, John A.Computational Fluid DynamicsAIAA 2015-07802015AIAA53rd AIAA Aerospace Sciences Meeting, Kissimmee, FL

(Abstract not yet available)

cfd-pubsapplebaum-michael-p eppard-william-m hall-leslie-h purinto-david-c
Applebaum, Michael P., Eppard, William M., Hall, Leslie H., Purinton, David C.Modeling and Simulation Techniques for the NASA SLS Service Module Panel Separation Event; From Loosely-Coupled Euler to Full-Coupled 6-DOF, Time-Accurate, Navier Stokes MethodologiesHall, Leslie H.Computational Fluid DynamicsAIAA 2019-18432019AIAAAIAA SciTech 2019 Forum, San Diego, CA

(Abstract not yet available)

cfd-pubsapplebaum-michael-p eppard-william-m hall-leslie-h purinto-david-c
Ali, Rekesh M.Time-Accurate LES of a Cone-Slice-Ramp at Mach 6Vogel, EthanCoder, James G.Computational Fluid Dynamics2020AIAA

A cone-slice-ramp geometry in hypersonic flow produces a pair of vortices which interact with the shockwave-boundary layer interaction at the compression ramp. A cone-slice-ramp with a 20° ramp has been simulated at ground-test conditions with time-accurate implicit large-eddy simulations (ILES) performed in the OVERFLOW computational fluid dynamics solver. This analysis demonstrated global instabilities in the flow around the cone-slice-ramp at the compression ramp and in the shedding of vortices from the frustum leading edge. The vortex structure demonstrates periodicity and consistent dominant spectra, while the SWBLI does not. Results of this ILES analysis were time-averaged and compared to existing RANS data. This comparison showed strong agreement between RANS and ILES, especially in the region upstream of the compression ramp. In the ramp region, ILES illuminates small-scale structures in the flow not captured by transitional RANS analysis.

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Orr, Jeb S.Advanced Optical Sensor Technology: Launch Vehicle and Spacecraft ApplicationsOrr, Jeb S.Trevino, L.C.; Dalton, C.L.Flight Mechanics and GN&CAIAA 2014-25402014AIAAAIAA Atmospheric Flight Mechanics Conference

The advent of compact, high-performance optical sensors of strain and temperature based on frequency-domain interrogation of special optical fibers yields many unique opportunities for sensing in environments that are challenging for traditional sensor technologies. An intriguing application is the use of fiber Bragg grating (FBG) sensors to collect critical structural, thermal, and even acoustic data throughout the launch vehicle and spacecraft engineering lifecycle, including during flight.
Fiber Bragg Grating sensors are formed from special optical perturbations of a communications-grade optical fiber, and act as high sensitivity, low mass, electrically passive, and electrically immune detectors of structural strain, temperature, and other quantities; the serial architecture and embeddable sensor element with very small cross section make FBGs an attractive solution for minimally invasive instrumentation of both ground test and flight test experiments, especially where traditional (piezoelectric, foil-resistive) sensors are impractical due to harsh environmental conditions.
In this paper, several elements of the state of the art of FBG sensors are detailed with a focus on the necessary technology development steps required to employ FBGs as a critical, enabling technology for collection of mission-critical structural dynamics, thermal, and subsystem health data in harsh flight environments. Current capabilities and limitations are detailed in the context of this unique application where existing commercial and research-grade sensor systems have not yet been extensively deployed.

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Orr, Jeb S.A Flight Dynamics Model for a Multi-Actuated Flexible Rocket VehicleOrr, Jeb S.Flight Mechanics and GN&CAIAA 2011-65632011AIAAAIAA Atmospheric Flight Mechanics Conference

A comprehensive set of motion equations for a multi-actuated flight vehicle is presented. The dynamics are derived from a vector approach that generalizes the classical linear perturbation equations for flexible launch vehicles into a coupled three-dimensional model. The effects of nozzle and aerosurface inertial coupling, sloshing propellant, and elasticity are incorporated without restrictions on the position, orientation, or number of model elements. The present formulation is well suited to matrix implementation for large-scale linear stability and sensitivity analysis and is also shown to be extensible to nonlinear time-domain simulation through the application of a special form of Lagrange’s equations in quasi-coordinates. The model is validated through frequency-domain response comparison with a high-fidelity planar implementation.

flight-mechanics-gnc-pubsorr-jeb-s