Organizational Unit:

Daniel Guggenheim School of Aerospace Engineering

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https://hdl.handle.net/1853/70742

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College of Engineering

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Aerospace Design Group

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Aerospace Systems Design Laboratory (ASDL)

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Air Transportation Laboratory

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Cognitive Engineering Center

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Space Systems Design Laboratory (SSDL)

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https://finding-aids.library.gatech.edu/agents/corporate_entities/106

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Publication Search Results

Now showing 1 - 10 of 40

Trajectory Reconstruction of a Martian Planetary Probe Mission: Reconstruction of the Spirit Mars Exploration Rover Entry Descent Landing Performance

(Georgia Institute of Technology, 2008-10) Wells, Grant W. ; Braun, Robert D.

Accurate post-flight reconstruction of a vehicle’s trajectory during entry into a planetary atmosphere can produce a wide array of valuable information. Data collected through the reconstruction of entry, descent, and landing system performance enables the quantification of performance margins for future systems. Beyond the engineering knowledge gained through trajectory reconstruction, the results may also be used by planetary scientists to generate an accurate atmospheric profile. This paper provides a reconstruction of the trajectory, vehicle orientation, and atmospheric density profile for the hypersonic and supersonic phases of the Spirit Mars Exploration Rover spacecraft.
Multiobjective Hypersonic Entry Aeroshell Shape Optimization

(Georgia Institute of Technology, 2008-09) Theisinger, John E. ; Braun, Robert D.

A capability has been developed that utilizes multiobjective optimization to identify hypersonic entry aeroshell shapes that will increase landed mass capability. Aeroshell shapes are parameterized using non-uniform rational B-splines to generate complete aeroshell surfaces. Hypersonic aerodynamic objectives and constraints are computed by numerically integrating pressure coefficient distributions obtained using Newtonian flow theory. An integrated optimization environment is created using iSIGHT with single- and multiobjective evolutionary algorithms. Results are presented based on optimization using constraints derived from the aeroshell for the Mars Science Laboratory mission. Resulting solutions clearly demonstrate the trade-offs between drag-area, static stability, and volumetric efficiency for this particular mission.
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.
Low-Thrust Trajectory Optimization Tool to Assess Options for Near-Earth Asteroid Deflection

(Georgia Institute of Technology, 2008-08) Stahl, Benjamin A. ; Braun, Robert D.

In the past decade, the scientific community has become more interested in Near Earth Objects (NEOs) and the threat they pose to existence of life on this planet. The recent trend in NEO deflection technique research has been toward "slow push" techniques in order to absolve the need for sending nuclear weapons into space. A software tool was developed to assist in design and performance testing of various low-thrust deflection methods. The tool features an n-body high fidelity long term orbit propagator that allows for deflection mechanism forces to be directly applied through the equations of motion. The propagator utilizes DE405 ephemeris data for the acting bodies and was validated through comparison with JPL's HORIZONS database. A hybrid optimization algorithm featuring a genetic algorithm global search and a conjugate direction local search was also developed to optimize the thrust direction versus time for a given deflection technique. The optimizer is applicable for many different missions and objectives, and is tested with several missions designed to maximize NEO close approach miss distance.
Guidance, Navigation, and Control Technology System Trades for Mars Pinpoint Landing

(Georgia Institute of Technology, 2008-08) Steinfeldt, Bradley A. ; Grant, Michael J. ; Matz, Daniel M. ; Braun, Robert D. ; Barton, Gregg H.

Landing site selection is a compromise between safety concerns associated with the site's terrain and scientific interest. Therefore, technologies enabling pinpoint landing (sub-100 m accuracies) on the surface of Mars are of interest to increase the number of accessible sites for in-situ research as well as allow placement of vehicles nearby prepositioned assets. A survey of various guidance, navigation, and control technologies that could allow pinpoint landing to occur at Mars has shown that negligible propellant mass fraction benefits are seen for reducing the three-sigma position dispersion at parachute deployment below approximately 3 km. Four different propulsive terminal descent guidance algorithms were analyzed with varying applicability to flight. Of these four, a near propellant optimal, analytic guidance law showed promise for the conceptual design of pinpoint landing vehicles. The existence of a propellant optimum with regards to the initiation time of the propulsive terminal descent was shown to exist for various flight conditions. In addition, subsonic guided parachutes are shown to provide marginal performance benefits due to the timeline associated with Martian entries, and a low computational-cost, yet near fuel optimal propulsive terminal descent algorithm is identified. This investigation also demonstrates that navigation is a limiting technology for Mars pinpoint landing, with overall landed performance being largely driven by navigation sensor and map tie accuracy.
Entry, Descent, and Landing System Design for the Mars Gravity Biosatellite

(Georgia Institute of Technology, 2008-06) Korzun, Ashley M. ; Smith, Brandon P. ; Hartzell, Christine M. ; Yu, Chi-Yau ; Place, Laura A. ; Martinelli, Scott K. ; Braun, Robert D. ; Hott, Kyle B.

Execution of a full entry, descent, and landing (EDL) from low Earth orbit is a rare requirement among university class spacecraft. Successful completion of the Mars Gravity Biosatellite mission requires the recovery of a mammalian payload for post-flight analysis of the effects of partial gravity. The EDL design for the Mars Gravity Biosatellite is driven by requirements on the allowable deceleration profile for a payload of deconditioned mice and maximum allowable recovery time. The 260 kg entry vehicle follows a ballistic trajectory from low Earth orbit to a target recovery site at the Utah Test and Training Range. Reflecting an emphasis on design simplicity and the use of heritage technology, the entry vehicle uses the Discoverer aeroshell geometry and leverages aerodynamic decelerators for mid-air recovery and operations originally developed for the Genesis mission. This paper presents the student-developed EDL design for the Mars Gravity Biosatellite, with emphasis on trajectory design, dispersion analysis, and mechanical design and performance analysis of the thermal protection and parachute systems. Also included is discussion on EDL event sequencing and triggers, the de-orbit of the spacecraft bus, plans for further work, and the educational impact of the Mars Gravity Biosatellite program.
A Survey of Supersonic Retropropulsion Technology for Mars Entry, Descent, and Landing

(Georgia Institute of Technology, 2008-03) Korzun, Ashley M. ; Cruz, Juan R. ; Braun, Robert D.

This paper presents a literature survey on supersonic retropropulsion technology as it applies to Mars entry, descent, and landing (EDL). The relevance of this technology to the feasibility of Mars EDL is shown to increase with ballistic coefficient to the point that it is likely required for human Mars exploration. The use of retropropulsion to decelerate an entry vehicle from hypersonic or supersonic conditions to a subsonic velocity is the primary focus of this review. Discussed are systems level studies, general flowfield characteristics, static aerodynamics, vehicle and flowfield stability considerations, and aerothermodynamics. The experimental and computational approaches used to develop retropropulsion technology are also reviewed. Finally, the applicability and limitations of the existing literature and current state-of-the-art computational tools to future missions are discussed in the context of human and robotic Mars exploration.1,2
Supersonic Inflatable Aerodynamics Decelerators for Use on Future Robotic Missions To Mars

(Georgia Institute of Technology, 2008-03) Clark, Ian G. ; Hutchings, Allison L. ; Tanner, Christopher L. ; Braun, Robert D.

The 2009 Mars Science Laboratory mission is being designed to place an 850 kg rover on the surface of Mars at an altitude of at least one kilometer [1]. This is being accomplished using the largest aeroshell and supersonic parachute ever flown on a Mars mission. Future missions seeking to place more massive payloads on the surface will be constrained by aeroshell size and deployment limitations of supersonic parachutes [2],[3]. Inflatable aerodynamic decelerators (IADs) represent a technology path that can relax those constraints and provide a sizeable increase in landed mass. This mass increase results from improved aerodynamic characteristics that allow IADs to be deployed at higher Mach numbers and dynamic pressures than can be achieved by current supersonic parachute technology. During the late 1960’s and early 1970’s preliminary development work on IADs was performed. This included initial theoretical shape and structural analysis for a variety of configurations as well as wind tunnel and atmospheric flight tests for a particular configuration, the Attached Inflatable Decelerator (AID). More recently, the Program to Advance Inflatable Decelerators for Atmospheric Entry (PAI-DAE) has been working to mature a second configuration, the supersonic tension cone decelerator, for use during atmospheric entry. 1,2 This paper presents an analysis of the potential advantages of using a supersonic IAD on a proposed 2016 Mars mission. Conclusions drawn are applicable to both the Astrobiology Field Laboratory and Mars Sample Return mission concepts. Two IAD configurations, the AID and tension cone, are sized and traded against their system-level performance impact. Analysis includes preliminary aerodynamic drag estimates for the different configurations, trajectory advantages provided by the IADs, and preliminary geometric and mass estimates for the IAD subsystems. Entry systems utilizing IADs are compared against a traditional parachute system as well as a system employing an IAD in the supersonic regime and a parachute in the subsonic regime. Key sensitivities in IAD design are included to highlight areas of importance in future technology development programs.
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.