http://smartech.gatech.edu/handle/1853/7704 The Space Systems Design Laboratory (SSDL) was founded within the School of Aerospace Engineering in 1995 with the goal of creating a world-class research and educational organization dedicated to the design of advanced space systems. The lab is co-directed by Dr. Robert D. Braun and Dr. John R. Olds, and consists of undergraduate students, Masters-level graduate students, and PhD-level graduate students with an interest in space systems analysis, design and development. Search the Channel search http://smartech.gatech.edu/simple-search http://smartech.gatech.edu/handle/1853/24397 Title: Survivability and Resiliency of Spacecraft and Space-Based Networks: a Framework for Characterization and Analysis <br/> <br/>Authors: Castet, Jean-Francois; Saleh, Joseph H. <br/> <br/>Abstract: Considerations of survivability and resiliency have always been of importance in the design and analysis of military systems. Over the past two decades, the importance of survivability and resiliency has expanded beyond military systems to include public networks and infrastructure systems. The analysis and assessment of networked systems with respect to survivability has become particularly acute in recent years, as attested to by a growing technical literature on the subject. In this paper, we bring these considerations of survivability and resiliency to bear on spacecraft and space-based networks. We develop a framework for comparing the survivability and resiliency of different space architectures, namely that of a monolithic design and a distributed (or networked) space system architecture. There are multiple metrics along which different space architectures can be benchmarked and compared. We argue that if survivability and resiliency are not accounted for, then the evaluation process is likely to be biased in favor of monolithic spacecraft. We show that if in a given context survivability and resiliency are an important requirement for a particular customer, then a distributed architecture is more likely to satisfy this requirement than a monolithic spacecraft design. We discuss in the context of our framework different classes of threats, as well as the high-frequency and low-frequency system response to (or coping strategies with) these shocks or damaging events. We illustrate the importance of this characterization for a formal definition of survivability and resiliency and a proper quantitative analysis of the subject. Finally, we propose in future work to integrate our framework with a design tool that allows the exploration of the design trade-space of distributed space architecture and show how survivability can be “optimized” or traded against other system attributes. <br/> <br/>Description: AIAA 2008-7707, Space 2008 Conference & Exposition, San Diego, CA, Sept 2008. http://smartech.gatech.edu/handle/1853/15067 Title: Survey of Global Optimization Methods for Low-Thrust, Multiple Asteroid Tour Missions <br/> <br/>Authors: Alemany, Kristina; Braun, Robert D. <br/> <br/>Abstract: Electric propulsion has recently become a viable option for robotic missions, enabling shorter flight times, fewer required planetary gravity assists, smaller launch vehicles, and/or larger payloads. Trajectory design of these missions often relies on local optimization of the low-thrust trajectories using starting points for departure and arrival dates and selection of gravitational swing-bys based on previous experience. Global optimization of a low-thrust trajectory with multiple targets and gravity assists, however, is a difficult problem, due to the multi-modality and large size of the design space. In choosing analysis techniques, there exists an important tradeoff between the accuracy of the results and computing time required. This paper presents the difficulty of solving this global optimization problem, using the design of a multiple asteroid tour mission as an example. Furthermore, this paper presents an overview of the methods available for both low-thrust trajectory optimization and global optimization, along with recent improvements made, and assesses their efficacy and applicability to solving a multiple target/multiple gravity assist problem. <br/> <br/>Description: 2007 AAS/AIAA Space Flight Mechanics Meeting January 2007, Sedona, Arizona. http://smartech.gatech.edu/handle/1853/14804 Title: Control Authority Network Analysis Applied to Lunar Outpost Deployment <br/> <br/>Authors: Alemany, Kristina; Morse, Elisabeth L.; Easter, Robert W. <br/> <br/>Abstract: In order to return humans to the Moon, the Constellation Program will be required to operate a complex network of humans and spacecraft in several locations. This requires an early look at how decision-making authority will be allocated and transferred between humans and computers, for each of the many decision steps required for the various mission phases. This paper presents an overview of such a control authority analysis, along with an example based upon a lunar outpost deployment scenario. The results illustrate how choosing an optimal control authority architecture can serve to significantly reduce overall mission risk, when applied early in the design process. <br/> <br/>Description: 2007 IEEE Aerospace Conference March 2007, Big Sky, MT. http://smartech.gatech.edu/handle/1853/14773 Title: An Approximate Ablative Thermal Protection System Sizing Tool for Entry System Design <br/> <br/>Authors: Dec, John A.; Braun, Robert D. <br/> <br/>Abstract: A computer tool to perform entry vehicle ablative thermal protection systems sizing has been developed. Two options for calculating the thermal response are incorporated into the tool. One, an industry-standard, high-fidelity ablation and thermal response program was integrated into the tool, making use of simulated trajectory data to calculate its boundary conditions at the ablating surface. Second, an approximate method that uses heat of ablation data to estimate heat shield recession during entry has been coupled to a one-dimensional finite-difference calculation that calculates the in-depth thermal response. The in-depth solution accounts for material decomposition, but does not account for pyrolysis gas energy absorption through the material. Engineering correlations are used to estimate stagnationpoint convective and radiative heating as a function of time. The sizing tool calculates recovery enthalpy, wall enthalpy, surface pressure, and heat transfer coefficient. Verification of this tool is performed by comparison to past thermal protection system sizings for the Mars Pathfinder and Stardust entry systems and calculations are performed for an Apollo capsule entering the atmosphere at lunar and Mars return speeds. <br/> <br/>Description: AIAA Aerospace Sciences Conference January 2006, Reno, NV.