Organizational Unit:

Space Systems Design Laboratory (SSDL)

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

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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/1138

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Publication Search Results

Now showing 1 - 10 of 14

Advances in Guidance Navigation Control for Planetary Entry, Descent, and Landing Systems

(Georgia Institute of Technology, 2016-02) Putnam, Zachary R. ; Braun, Robert D.

Planetary entry, descent, and landing has been performed successfully at Venus, Earth, Mars, Jupiter, Titan, and the moon, producing a wealth of in situ data not available from in-space remote-sensing platforms. To achieve such success, entry, descent, and landing systems have been designed to accommodate a wide variety of mission scenarios and environments, from the thin atmosphere of Mars to the thick atmosphere of Venus, from atmospheric entry velocities as low as 4 km/s at Mars to nearly 48 km/s at Jupiter. The history and development of the complex systems necessary to successfully execute entry, descent, and landing is summarized and discussed, with a focus on guidance and control strategies. Improvements to inertial navigation systems and interplanetary approach navigation techniques are highlighted. Mission requirements that drive entry, descent, and landing system design are identified. Lastly, future challenges and goals for entry, descent, and landing systems are enumerated and current technology development efforts are discussed.
Strategies for Landing Large Ballistic Coefficient Vehicles on Mars

(Georgia Institute of Technology, 2016-01) Anderson, Tyler R. ; Putnam, Zachary R. ; Braun, Robert D.

Large ballistic coefficient entry, descent, and landing vehicles are likely required to achieve more ambitious exploration goals at Mars. This paper investigates strategies for safe landing on Mars for vehicles with large ballistic coefficients, with a focus on maintaining sufficient altitude for terminal descent. Specifically, requirements and guidance strategies for the use of aerodynamic lift in the hypersonic regime are assessed over a range of ballistic coefficients. Results indicate that, for moderately high ballistic coefficients, judicious use of lift may allow safe landing. These strategies may be applicable to future large-scale robotic or human entry, descent, and landing architectures.
Review and Assessment of the Steep Lifting Entry Closed-Form Trajectory Solution

(Georgia Institute of Technology, 2016-01) Putnam, Zachary R. ; Braun, Robert D.

The complete, historical closed-form steep lifting entry trajectory solution is documented and developed from first principles. The efficacy and accuracy of the solution is assessed for application to aeroassist missions of interest, including aerocapture and entry. Specifically, analytical assessment of the primary assumptions in the solution shows the solution is applicable across a wide range of initial states for vehicles with nonzero lift-to-drag ratios. Solution accuracy is assessed relative to the planar equations of motion; accuracy improves for steeper trajectories and larger lift-to-drag ratios. The steep lifting entry estimate of peak acceleration is shown to be accurate to within 10% for initial flight- path angles steeper than approximately -10 deg across a variety of vehicles, missions, and planetary destinations. Overall, the steep lifting entry solution provides a simple, rapid first-order trajectory solution capability for lifting aeroassist vehicles with relatively steep initial flight-path angles.
Analytical Assessment of Drag-Modulation Trajectory Control for Planetary Entry with Application to Real-Time Guidance

(Georgia Institute of Technology, 2015-08) Putnam, Zachary R. ; Braun, Robert D.

Discrete-event drag-modulation trajectory control is assessed for planetary entry using the analytical Allen-Eggers approximate solution to the equations of motion. A control authority metric for drag-modulation trajectory control systems is derived. Closed-form relationships are developed to assess range divert capability, identify jettison condition constraints for limiting peak acceleration and peak heat rate. Discrete-event drag-modulation systems with single stages and an arbitrary number of stages are assessed.
Extension and Enhancement of the Allen-Eggers Analytic Solution for Ballistic Entry Trajectories

(Georgia Institute of Technology, 2014-06) Putnam, Zachary R. ; Braun, Robert D.

The closed-form analytic solution to the equations of motion for ballistic entry developed by Allen and Eggers is extended and enhanced with a method of choosing an appropriate constant flight-path angle, limits based on the equations of motion and acceptable ap- proximation error are proposed that bound the domain of applicability, and closed-form expressions for range and time-dependency. The expression developed for range to go exhibits error that may low enough for onboard drag-modulation guidance and targeting systems. These improvements address key weaknesses in the original approximate solution. Results show that the extended and enhanced Allen-Eggers solution provides good accuracy across a range of ballistic coefficients entries at Earth with initial flight-path angles steeper than -7 deg.
Advances in Inertial Guidance Technology for Aerospace Systems

(Georgia Institute of Technology, 2013-08) Braun, Robert D. ; Putnam, Zachary R. ; Steinfeldt, Bradley A. ; Grant, Michael J. J.

The origin, evolution, and outlook of guidance as a path and trajectory manager for aerospace systems is addressed. A survey of theoretical developments in the field is presented demonstrating the advances in guidance system functionality built upon inertial navigation technology. Open-loop and closed-loop approaches for short-range systems, long-range systems and entry systems are described for both civilian and military applications. Over time, guidance system development has transitioned from passive and open-loop systems to active, closed-loop systems. Significant advances in onboard processing power have improved guidance system capabilities, shifting the algorithmic computational burden to onboard systems and setting the stage for autonomous aerospace systems. Seminal advances in aerospace guidance are described, highlighting the advancements in guidance and resulting performance improvements in aerospace systems.
Precision Landing at Mars Using Discrete-Event Drag Modulation

(Georgia Institute of Technology, 2013-02) Putnam, Zachary R. ; Braun, Robert D.

An entry, descent, and landing architecture capable of achieving Mars Science Laboratory class landed accuracy (with 10 km of target) while delivering a Mars Exploration Rover class payload to the surface of Mars is presented. The architecture consists of a Mars Exploration Rover class aeroshell with a rigid, annular drag skirt. Maximum vehicle diameter is limited to be compatible with current launch vehicle fairings. A single drag skirt jettison event is used to control range during entry. Three-degree-of-freedom trajectory simulation is used in conjunction with Monte Carlo techniques to assess the flight performance of the proposed architecture. Results indicate landed accuracy is competitive with pre-flight Mars Science Laboratory estimates, and peak heat rate and integrated heat load are significantly reduced relative to the Mars Exploration Rover entry system. Modeling parachute descent within the onboard guidance algorithm is found to remove range error bias present at touchdown; the addition of a range-based parachute deploy trigger is found to significantly improve landed accuracy.
Variable Angle-of-Attack Profile Entry Guidance for a Crewed Lifting Body

(Georgia Institute of Technology, 2013-01) Putnam, Zachary R. ; Grant, Michael J. J. ; Kelly, Jenny R. ; Braun, Robert D. ; Krevor, Zachary C.

The feasibility of flying a crewed lifting body, such as the HL-20, during entry from low-Earth orbit without steady-state body flap deflections was evaluated. This entry strategy mitigates the severity of the aerothermal environment on the vehicle's body flaps and reserves control power for transient maneuvers. A numeric predictor-corrector entry guidance algorithm was developed to accommodate the range of vehicle trim angle-of-attack profiles possible when steady-state body flap deflections are prohibited. Results show that the guidance algorithm is capable of steering the vehicle to a desired target from low-Earth orbit while satisfying a reasonable suite of trajectory constraints, including limits on peak heat rate, peak sensed deceleration, and integrated heat load. Uncertainty analyses confirm this result and show that the vehicle maintains significant performance robustness to expected day-of-flight uncertainties. Additionally, parametric scans over mission design parameters of interest indicate a high level of exibility is available for the low-Earth orbit return mission. Together, these results indicated that the proposed entry strategy is feasible: crewed lifting bodies may be effectively flown without steady-state body flap deflections.
Drag Modulation Flight Control System Options for Planetary Aerocapture

(Georgia Institute of Technology, 2013-01) Putnam, Zachary R. ; Braun, Robert D.

Drag modulation flight control may provide a simple method for controlling energy during aerocapture. Several drag modulation flight control system options are discussed and evaluated, including single-stage jettison, two-stage jettison, and continuously-variable drag modulation systems. Performance is assessed using numeric simulation with real-time guidance and targeting algorithms. Monte Carlo simulation is used to evaluate system robustness to expected day-of-flight uncertainties. Results indicate that drag modulation flight control is an attractive option for aerocapture systems at Mars where low peak heat rates enable the use of lightweight in inflatable drag areas. Aerocapture using drag modulation at Titan is found to require large drag areas to limit peak heat rates to non-ablative thermal protection system limits or advanced lightweight ablators. The large gravity well and high peak heat rates experienced during aerocapture at Venus make drag modulation flight control unattractive when combined with a non-ablative thermal protection system. Significantly larger drag areas or advances in fabric-based material thermal properties are required to improve feasibility at Venus.
Guided Entry Performance of Low Ballistic Coefficient Vehicles at Mars

(Georgia Institute of Technology, 2012-03) Meginnis, Ian ; Putnam, Zachary R. ; Clark, Ian G. ; Braun, Robert D. ; Barton, Gregg H.

Current Mars entry, descent, and landing technology is near its performance limit and is unable to land payloads on the surface that exceed approximately 1 metric ton. One option for increasing landed payload mass capability is decreasing the entry vehicle’s hypersonic ballistic coefficient. A lower ballistic coefficient vehicle decelerates higher in the atmosphere, providing additional timeline and altitude margin necessary for heavier payloads. This study analyzed the guided entry performance of concept low ballistic coefficient vehicles at Mars. A terminal point controller guidance algorithm was used to provide precision targeting capability. Accuracy at parachute deploy, peak deceleration, peak heat rate, and integrated heat load were assessed and compared to a traditional vehicle to determine the effects of lowering the vehicle ballistic coefficient on entry performance. Results from this study suggest that while accuracy at parachute deploy degrades with decreasing ballistic coefficient, accuracy and other performance metrics remain within reasonable bounds for ballistic coefficients as low as 1 kg/m2. As such, this investigation demonstrates that from a performance standpoint, guided entry vehicles with large diameters may be feasible at Mars.