Organizational Unit:

Aerospace Systems Design Laboratory (ASDL)

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https://hdl.handle.net/1853/70744

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Organizational Unit

Daniel Guggenheim School of Aerospace Engineering

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https://finding-aids.library.gatech.edu/agents/corporate_entities/1135

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Publication Search Results

Now showing 1 - 10 of 52

A Value Proposition for Lunar Architectures Utilizing Propellant Re-supply Capabilities

(Georgia Institute of Technology, 2007-09) Young, James ; Wilhite, Alan

The NASA Exploration Systems Architecture Study (ESAS)ⁱⁱ produced a transportation architecture for returning humans to the moon affordably and safely while using commercial services for tasks such as cargo delivery to low earth orbit (LEO). Another potential utilization of commercial services is the delivery of cryogenic propellants to LEO for use in lunar exploration activities. With in-space propellant re-supply available, there is the potential to increase the payload that can be delivered to the lunar surface, increase lunar mission durations, and enable a wider range of lunar missions. The addition of on-orbit propellant resupply would have far-reaching effects on the entire exploration architecture. Currently 70% of the weight delivered to LEO by the cargo launch vehicle is propellant needed for the TLI burn. This is a considerable burden and significantly limits the design freedom of the architecture. The ability of commercial providers to deliver cryogenic propellants to LEO may provide for a less expensive and better performing lunar architecture.
Responsive Space: Concept Analysis, Critical Review, and Theoretical Framework

(Georgia Institute of Technology, 2007-09) Saleh, Joseph H. ; Dubos, Gregory

Customers’ needs are dynamic and evolve in response to unfolding environmental uncertainties. The ability of a company or an industry to address these changing customers’ needs in a timely and cost-effective way is a measure of its responsiveness. In the space industry, a systemic discrepancy exists between the time constants associated with the change of customers’ needs, and the response time of the industry in delivering on-orbit solutions to these needs. Increasingly, the penalties associated with such delays are becoming unacceptable, and space responsiveness is recognized as a strategic imperative in commercial competitive and military environments. In this paper, we provide a critical assessment of the literature on responsive space and introduce a new multi-disciplinary framework for thinking about and addressing issues of space responsiveness. Our framework advocates three levels of responsiveness: a global industry-wide responsiveness, a local stakeholder responsiveness, and an interactive or inter-stakeholder responsiveness. We introduce and motivate the use of “responsiveness maps” for multiple stakeholders. We then identify “levers of responsiveness,” technical spacecraft- and launch-centric, as well as “soft” levers (e.g., acquisition policies) for improving the responsiveness of the space industry. Finally, we propose a series of research questions to aggressively tackle problems associated with space responsiveness.
The Gryphon: A Flexible Lunar Lander Design to Support a Semi-Permanent Lunar Outpost

(Georgia Institute of Technology, 2007-09) Arney, Dale ; Hickman, Joseph ; Tanner, Philip ; Wagner, John ; Wilson, Marc ; Wilhite, Alan W.

A lunar lander is designed to provide safe, reliable, and continuous access to the lunar surface by the year 2020. The NASA Exploration System Architecture is used to initially define the concept of operations, architecture elements, and overall system requirements. The design evaluates revolutionary concepts and technologies to improve the performance and safety of the lunar lander while minimizing the associated cost using advanced systems engineering capabilities and multi-attribute decision making techniques. The final design is a flexible (crew and/or cargo) lander with a side-mounted minimum ascent stage and a separate stage to perform lunar orbit insertion.
Technology Readiness Level, Schedule Risk and Slippage in Spacecraft Design: Data Analysis and Modeling

(Georgia Institute of Technology, 2007-09) Dubos, Gregory F. ; Saleh, Joseph H. ; Braun, Robert D.

Schedule slippage plagues the space industry, and is antinomic with the recent emphasis on space responsiveness. The Government Accountability Office has repeatedly noted the difficulties encountered by the Department of Defense in keeping its acquisition of space systems on schedule, and identified the low Technology Readiness Level (TRL) of the system/payload under development as a principal culprit driving schedule risk and slippage. In this paper, we analyze based on data from past space programs the relationship between technology uncertainty and schedule risk in the acquisition of space systems, and propose an analytical framework to identify appropriate schedule margins for mitigating the risk of schedule slippage. We also introduce the TRL-schedule-risk curves to help program managers make riskinformed decisions regarding the appropriate schedule margins for a given program, or the appropriate TRL to consider should the program’s schedule be exogenously and rigidly constrained. We recommend based on our findings, that the industry adopts and develops schedule risk curves (instead of single schedule point estimates), 2) that these schedule risk curves be made available to policy- and decision-makers in acquisition programs; and 3) that adequate schedule margins be defined according to an agreed upon and acceptable schedule risk level.
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.
An Approach for Calculating the Cost of Launch Vehicle Reliability

(Georgia Institute of Technology, 2007-09) Krevor, Zachary C. ; Wilhite, Alan W.

The goal of this paper is to determine the cost of increasing launch vehicle reliability during conceptual design. The launch vehicle mission requirements are held constant while various reliability strategies are evaluated for their affects on different performance and cost metrics. Traditional design disciplines, such as trajectory analysis and propulsion are included within the performance analysis while the cost discipline focuses on launch vehicle development and production cost. The reliability modeling is developed specifically for application to launch vehicles. A design environment is created that integrates the performance, cost, and reliability disciplines for use with optimization. The integrated environment is utilized to determine a set of optimal design configurations based on a specific weighting of cost and reliability. Different design options for the Cargo Launch Vehicle from the Exploration System Architecture Study are considered and the final result is a set of configurations optimized for a particular weighting of cost and reliability.
Mars Gravity Biosatellite: Engineering, Science, and Education

(Georgia Institute of Technology, 2007-09) Korzun, Ashley M. ; Braun, Robert D. ; Wagner, Erika B. ; Fulford-Jones, Thaddeus R.F. ; Deems, Elizabeth C. ; Judnick, Daniel C. ; Keesee, John E.

The Mars Gravity Biosatellite is a novel program aimed at providing data on the effects of partial gravity on mammalian physiology. Physiological problems intrinsic to prolonged stays in microgravity have long been concerns of manned spaceflight and will continue to be a significant obstacle in achieving the goals outlined in NASA’s Vision for Space Exploration. This student-developed, free-flyer spacecraft is designed to carry a payload of 15 mice into low Earth orbit, rotating to generate an acceleration environment equivalent to Martian gravity. After 35 days, the payload will be de-orbited and recovered for study. Data collected during the mission and post-recovery will be used to characterize the physiological changes incurred under partial gravity conditions and validate the models used in designing the spacecraft. This paper presents the preliminary design of the spacecraft. By providing groundbreaking flight data on the effects of partial gravity on mammalian physiology and engaging over 500 students to date, the Mars Gravity Biosatellite program is working to enable successful human exploration of the Moon and Mars while training and inspiring a new generation of scientists and engineers.
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.
Lazarus: A SSTO Hypersonic Vehicle Concept Utilizing RBCC and HEDM Propulsion Technologies

(Georgia Institute of Technology, 2006-11) Young, David Anthony ; Kokan, Timothy Salim ; Clark, Ian G. ; Tanner, Christopher ; Wilhite, Alan W.

Lazarus is an unmanned single stage reusable launch vehicle concept utilizing advanced propulsion concepts such as rocket based combined cycle engine (RBCC) and high energy density material (HEDM) propellants. These advanced propulsion elements make the Lazarus launch vehicle both feasible and viable in today's highly competitive market. The Lazarus concept is powered by six rocket based combined cycle engines. These engines are designed to operate with HEDM fuel and liquid oxygen (LOX). During atmospheric flight the LOX is augmented by air traveling through the engines and the resulting propellant mass fractions make single stage to orbit (SSTO) possible. A typical hindrance to SSTO vehicles are the large wings and landing gear necessary for takeoff of a fully fueled vehicle. The Lazarus concept addresses this problem by using a sled to take off horizontally. This sled accelerates the vehicle to over 500 mph using the launch vehicle engines and a propellant cross feed system. This propellant feed system allows the vehicle to accelerate using its own propulsion system without carrying the necessary fuel required while it is attached to the sled. Lazarus is designed to deliver 5,000 lbs of payload to a 100 nmi x 100 nmi x 28.5° orbit due East out of Kennedy Space Center (KSC). This mission design allows for rapid redeployment of small orbital assets with little launch preparation. Lazarus is also designed for a secondary strike mission. The high speed and long range inherent in a SSTO launch vehicle make it an ideal global strike platform. Details of the conceptual design process used for Lazarus are included in this paper. The disciplines used in the design include aerodynamics, configuration, propulsion design, trajectory, mass properties, cost, operations, reliability and safety. Each of these disciplines was computed using a conceptual design tool similar to that used in industry. These disciplines were then combined into an integrated design process and used to minimize the gross weight of the Lazarus design.