Organizational Unit:
Daniel Guggenheim School of Aerospace Engineering

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End date: 2014 × Start date: 2014 × search.filters.applied.f.isOrgUnitOfPublicationTitle: Daniel Guggenheim School of Aerospace Engineering × search.filters.applied.f.isSeriesOfPublicationTitle: Master's Projects ×

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Prox-1 Guidance, Navigation, & Control Overview: Development, Algorithms, and Integrated Simulation

2014-12-01 , Schulte, Peter Z.

This report describes the development and validation process of a highly automated Guidance, Navigation, & Control (GN&C) subsystem for a small satellite on-orbit inspection application. The resulting GN&C subsystem performs proximity operations (ProxOps) without human-in the-loop interaction. The report focuses on the description of the GN&C algorithms, the integration and testing of GN&C software, and the development of decision logic to address the question of how such a system can be effectively implemented for full automation. This process is unique because a multitude of operational scenarios must be considered and a set of complex interactions between various GN&C components must be defined to achieve the automation goal. The GN&C subsystem for the Prox-1 satellite is currently under development within the Space Systems Design Laboratory at the Georgia Institute of Technology. The Prox-1 mission involves deploying the LightSail 3U CubeSat, entering into a leading or trailing orbit of LightSail using ground-in-the-loop commands, and then performing automated ProxOps through formation flight and natural motion circumnavigation maneuvers. Operations such as these may be utilized for many scenarios including on-orbit inspection, refueling, repair, construction, reconnaissance, docking, and debris mitigation activities. Prox-1 uses onboard sensors and imaging instruments to perform its GN&C operations during on-orbit inspection of LightSail. Navigation filters perform relative orbit determination based on images of the target spacecraft, and guidance algorithms conduct automated maneuver planning. A slew and tracking controller sends attitude actuation commands to a set of control moment gyroscopes, and other controllers manage desaturation, detumble, and target acquisition/recovery. All Prox-1 GN&C components are developed in a MATLAB/Simulink six degree-of-freedom simulation environment and are integrated using decision logic to autonomously determine when certain actions should be performed. The complexity of this decision logic is the main challenge of this process, and the Stateflow tool in Simulink is used to establish logical relationships and manage data flow between each of the individual GN&C hardware and software components. Once the integrated GN&C simulation is fully developed in MATLAB/Simulink, the algorithms are autocoded to C/C++ and integrated into flight software. The subsystem is tested using hardware-in-the-loop on the flight computers and other hardware

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Preliminary Design Study of Asymmetric Hypersonic Inflatable Aerodynamic Decelerators for Mars Entry

2014-04-28 , Harper, Brooke P.

The Mars missions envisioned in the future require payload mass in excess of the current capable limit for entry vehicle technology. Deployable Hypersonic Inflatable Aerodynamic Decelerators offer one solution to successfully improve drag performance and reduce ballistic coefficient to mitigate entry, descent, and landing concerns as payload mass increases. The majority of the research that has been conducted on these structures thus far only focuses on axisymmetric geometries. In this investigation, aerodynamic and aerothermodynamic performance is examined for three proposed asymmetric families that can generate non-zero lift-to-drag ratios at 0° angle of attack and are compared to a symmetric counterpart. Ideal results include favorable lift-to-drag ratios with reduced ballistic coefficients. The blunt, asymmetric Hypersonic Inflatable Aerodynamic Decelerator designs considered are assembled from stacked tori configurations with a base diameter of 20 m and the capability to interface with a 10 m diameter rigid center body. The configurations reviewed are capable of producing hypersonic lift-to-drag ratios between ~0.1 and ~0.6 for angles of attack ranging from -30° to 20°. A 40 Mt entry mass, approximate mass of large robotic or human scale mission is assumed. Advantageous ballistic coefficient data is retrieved for some asymmetric geometries. All HIAD configurations are determined to be statically stable as well. An initial assessment of the aerothermodynamic response predicts significant heating with radiative heating being much greater than convective heating. From the analyses completed thus far, encouraging results project asymmetric Hypersonic Inflatable Aerodynamic Decelerators as conceivable candidates for future large scale Mars missions

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Design and Development of RED-Data2: A Data Recording Reentry Vehicle

2014-08-01 , Sidor, Adam T.

Defunct, manmade objects in orbit regularly reenter Earth’s atmosphere in an uncon trolled manner causing risk of both personal injury and property damage. To reduce uncertainty and improve our ability to predict surviving debris, impact time and impact location, reentry breakup dynamics and aerothermodynamics data is needed. The Reentry Breakup Recorder has demonstrated the ability to obtain inertial and thermal measure ments during reentry that are pertinent to spacecraft breakup. Building on this concept, the present investigation explores the design space for this device and matures a smaller, lighter and more operationally flexible system, termed RED-Data2.

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Parachute Dynamic Stability and the Effects of Apparent Inertia

2014-02-12 , Ginn, Jason M.

The dynamic stability and equilibrium conditions of a parachute are studied using a six degree of freedom dynamic model that includes apparent inertia effects. A dynamic model that incorporates apparent inertia is described and used for analysis. The moments on the parachute system caused by the apparent inertia term are shown to affect both the equilibrium point and the stability of the system. The adjustment to equilibrium is observed and discussed. A small disturbance stability analysis is performed to give stability criteria. The dynamic modes, pitching and coning, are discussed. Computational integration of the equations of motion is used to validate the small disturbance analysis as well as to show the effects of large disturbances. An example stability analysis and nonlinear simulation are performed for a ringsail system for Mars entry.

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A Comparison of Three Algorithms for Orion Drogue Parachute Release

2014-04-28 , Matz, Daniel A.

The Orion Multi-Purpose Crew Vehicle is susceptible to flipping apex forward between drogue parachute release and main parachute inflation. A smart drogue release algorithm is required to select a drogue release condition that will not result in an apex forward main parachute deployment. The baseline algorithm is simple and elegant, but does not perform as well as desired in drogue failure cases. A simple modification to the baseline algorithm can improve performance, but can also sometimes fail to identify a good release condition. A new algorithm employing simplified rotational dynamics and a numeric predictor to minimize a rotational energy metric is proposed. A Monte Carlo analysis of a drogue failure scenario is used to compare the performance of the algorithms. The numeric predictor prevents more of the cases from flipping apex forward, and also results in an improvement in the capsule attitude at main bag extraction. The sensitivity of the numeric predictor to aerodynamic dispersions, errors in the navigated state, and execution rate is investigated, showing little degradation in performance

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