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Space Systems Design Laboratory (SSDL)

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

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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 13

Design Space Pruning Heuristics and Global Optimization Method for Conceptual Design of Low-Thrust Asteroid Tour Missions

(Georgia Institute of Technology, 2008-09) Alemany, Kristina ; Braun, Robert D.

Electric propulsion has recently become a viable technology for spacecraft, enabling shorter flight times, fewer required planetary gravity assists, larger payload masses, and/or smaller launch vehicles. With the maturation of this technology, however, comes a new set of challenges in the area of trajectory design. In 2006, the 2nd Global Trajectory Optimization Competition (GTOC2) posed a difficult mission design problem: to design the best possible low-thrust trajectory, in terms of final mass and total mission time, that would rendezvous with one asteroid in each of four pre-defined groups. Even with recent advances in low-thrust trajectory optimization, a full enumeration of this problem was not possible. This work presents a two-step methodology for determining the optimum solution to a low-thrust, combinatorial asteroid rendezvous problem. First is a pruning step that uses a heuristic sequence to quickly reduce the size of the design space. Second, a multi-level genetic algorithm is combined with a low-thrust trajectory optimization method to locate the best solutions of the reduced design space. The proposed methodology is then validated by applying it to a problem with a known solution.
Design Space Pruning Techniques for Low-Thrust, Multiple Asteroid Rendezvous Trajectory Design

(Georgia Institute of Technology, 2007-09) Alemany, Kristina ; Braun, Robert D.

In 2006, the 2nd Global Trajectory Optimization Competition (GTOC2) posed a “Grand Asteroid Tour” trajectory optimization problem, where participants were required to find the best possible low-thrust trajectory that would rendezvous with one asteroid from each of four defined groups. As a first step, most teams employed some form of design space pruning, in order to reduce the overall number of possible asteroid combinations. Because of the large size of the problem, teams were not able to determine if their pruning technique had successfully eliminated only bad solutions from the design space. Therefore, a small subset of the GTOC2 problem was analyzed, and several design space pruning techniques were applied to determine their effectiveness. The results indicate that the pruning techniques chosen by the participants likely eliminated good solutions from the design space, because they either did not accurately represent the low-thrust problem or could not be considered independently without the effect of other factors.
Design Space Pruning Techniques for Low-Thrust Multiple Asteroid Rendezvous Trajectory Design

(Georgia Institute of Technology, 2007-08) Alemany, Kristina ; Braun, Robert D.

In 2006, the 2nd Global Trajectory Optimization Competition (GTOC2) posed a "Grand Asteroid Tour" trajectory optimization problem, where participants were required to find the best possible low-thrust trajectory that would rendezvous with one asteroid from each of four defined groups. As a first step, most teams employed some form of design space pruning, in order to reduce the overall number of possible asteroid combinations. Because of the large size of the problem, teams were not able to determine if their pruning technique had successfully eliminated only bad solutions from the design space. Therefore, a small subset of the GTOC2 problem was analyzed, and several design space pruning techniques were applied to determine their effectiveness. The results indicate that the pruning techniques chosen by the participants likely eliminated good solutions from the design space, because they either did not accurately represent the low-thrust problem or could not be considered independently without the effect of other factors.
Control Authority Network Analysis Applied to Lunar Outpost Deployment

(Georgia Institute of Technology, 2007-03) Alemany, Kristina ; Morse, Elisabeth L. ; Easter, Robert W.

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.
Survey of Global Optimization Methods for Low-Thrust, Multiple Asteroid Tour Missions

(Georgia Institute of Technology, 2007-01) Alemany, Kristina ; Braun, Robert D.

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.
Survey of Global Optimization Methods for Low-Thrust Multiple Asteroid Tour Missions

(Georgia Institute of Technology, 2007-01) Alemany, Kristina ; Braun, Robert D.

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.
Mars Entry, Descent, and Landing Parametric Sizing and Design Space Visualization Trades

(Georgia Institute of Technology, 2006-08) Alemany, Kristina ; Wells, Grant William ; Theisinger, John ; Clark, Ian G. ; Braun, Robert D.

Entry, descent, and landing (EDL) is a multidimensional, complex problem, which is difficult to visualize in simple plots. The purpose of this work is to develop a systematic visualization scheme that could capture Mars EDL trades as a function of a limited number of variables, such that programmatic design decisions could be effectively made with insight of the design space. Using the Mars Science Laboratory (MSL) as a basis, contour plots have been generated for key EDL figures of merit, such as maximum landed elevation and landed mass as a function of four input parameters: entry mass, entry velocity, entry flight path angle, and vehicle L/D. Additionally, sensitivity plots have been generated in an attempt to capture the effects of varying the fixed input parameters. This set of EDL visualization data has been compiled into a Mars EDL handbook to aid in pre-phase A design space exploration and decision making.
Probabilistic Cost, Risk, and Throughput Analysis of Lunar Transportation Architectures

(Georgia Institute of Technology, 2006-03) Alemany, Kristina ; Olds, John R.

The President's Vision for Space Exploration presents a need to determine the best architecture and set of vehicle elements in order to achieve a sustained human lunar exploration program. The Lunar Architecture Stochastic Simulator and Optimizer (LASSO), a new simulation-based capability based on discrete-event simulation, was created to address this question by probabilistically simulating lunar transportation architecture based on cost, reliability, and throughput figures of merit. In this study, two competing lunar transportation architectures are examined for a variety of launch vehicle scenarios to determine the best approach for human lunar exploration. Additionally, the two architectures are also compared for varying available ground infrastructure and desired flight rates. It is concluded that an expendable architecture is favored, using man-rated versions of existing evolved expendable launch vehicles (EELVs) for crew launches and developing a heavy-lift launch vehicle for cargo launches.
LASSO - Lunar Architecture Stochastic Simulator and Optimizer

(Georgia Institute of Technology, 2005-08) Alemany, Kristina ; Street, David C.

The Lunar Architecture Stochastic Simulator and Optimizer (LASSO) is a simulation-based capability, based upon discrete event simulation (DES), for evaluating and optimizing flight element options for lunar transportation architectures. This simulation capability improves the ability to rapidly measure cost, reliability, and schedule impacts of various top-level architecture decisions and individual elements within an architecture. The ability to probabilistically simulate and even optimize an overall transportation approach represents a significant enhancement over current deterministic analysis capabilities for top-level decision making. LASSO integrates a database of flight elements in Microsoft Excel® with architecture models in Rockwell Software’s Arena®. The Arena models are further integrated into Phoenix Integration’s ModelCenter® to allow optimization of the overall architecture by selecting various combinations of elements from the database. Sample results are presented for an expendable and a reusable lunar transportation architecture to illustrate the capabilities of LASSO for top-level decision making.
Tempest: Crew Exploration Vehicle Concept

(Georgia Institute of Technology, 2005-07) Hutchinson, Virgil L., Jr. ; Olds, John R. ; Alemany, Kristina ; Christian, John A., III ; Clark, Ian G. ; Crowley, John ; Krevor, Zachary C. ; Rohrschneider, Reuben R. ; Thompson, Robert W. ; Young, David Anthony ; Young, James J.

Tempest is a reusable crew exploration vehicle (CEV) for transferring crew from the Earth to the lunar surface and back. Tempest serves as a crew transfer module that supports a 4-person crew for a mission duration of 18 days, which consists of 8 days total transit duration and 10-day surface duration. Primary electrical power generation and on-orbit maneuvering for Tempest is provided by an attached Power and Propulsion Module (PPM). Hydrogen (H2)/oxygen (O2) fuel cells and a high energy-density matter (HEDM)/liquid oxygen (LOX) propellant reaction control system (RCS) provide power and reaction control respectively during Tempest’s separation from the PPM. Tempest is designed for a lifting entry and is equipped with parachutes for a soft landing. Tempest is part of an overall lunar transportation architecture. The 60,731 lbs combination of Tempest and the PPM are launched atop the notional Centurion C-1 heavylift launch vehicle (HLLV) and delivered to a 162 nmi, 28.5º circular orbit. After separating from the C-1 upper stage, the Tempest/PPM autonomously rendezvous with Manticore, an expendable trans-lunar injection (TLI) stage pre-positioned in the current orbit, and transfer to a lunar trajectory. After entering a 54 nmi polar circular lunar orbit, the Tempest/PPM separate from Manticore. Tempest separates from the PPM and is ferried to/from the lunar surface by Artemis, a reusable lunar lander. Upon return from the lunar surface, Tempest reconnects with the PPM, and the PPM provides the trans-earth injection (TEI) burn required to return to low earth orbit (LEO). Prior to atmospheric entry, Tempest separates from the PPM and subsequently executes a lifting entry trajectory. Crushable thermal foam attached to the lower surface of Tempest serves as an ablative thermal protection system (TPS) and the impact absorber of the parachute landing. Details of the conceptual design process used for Tempest are included in this paper. The disciplines used in the design include: configuration, aerodynamics, propulsion, trajectory, mass properties, environmental control life support system (ECLSS), entry aeroheating and TPS, terminal landing system (TLS), cost, operations, and reliability & safety. Each of these disciplines was computed using a conceptual design tool similar to that used in industry. These disciplines were then combined and optimized for the minimum gross weight of the Tempest CEV. The total development cost including the design, development, testing and evaluation (DDT&E) cost was determined to be $2.9 B FY’04. The theoretical first unit (TFU) cost for the Tempest CEV was $479 M FY’04. A summary of design disciplines as well as the economic results are included.