Date of Award

Fall 3-28-2025

Access Type

Dissertation - Open Access

Degree Name

Doctor of Philosophy in Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

Morad Nazari

Committee Advisor

Morad Nazari

First Committee Member

Richard Prazenica

Second Committee Member

Troy Henderson

Third Committee Member

Elisa Capello

Fourth Committee Member

Jeffrey Smith

Fifth Committee Member

Sergey V. Drakunov

College Dean

James W. Gregory

Abstract

Over the past half-century, humanity has gained extensive experience conducting manned spaceflight near Earth. Arguably, "near Earth" could even include the Moon — the most distant destination humans have reached. However, "near" in this work primarily refers low Earth orbit (LEO). One could argue that we have not truly left Earth since the Apollo, as spacecraft in some LEOs remain subject to atmospheric drag thus emphasizing their continued connection to Earth's immediate environment. Reflecting on this, it becomes clear that humanity has largely remained bound to Earth’s immediate vicinity since the Apollo missions reached the Moon. However, that is set to change. As of this writing, the Artemis II mission is gearing up to launch, carrying astronauts further from Earth than ever before. This milestone alone is a significant achievement, but the ambitious goals of the Artemis program and the Moon-to-Mars campaign bring forward an array of new challenges. For scientists and engineers who are designing these missions, these challenges highlight the complexity and excitement of venturing beyond what we know.

Many of these challenges revolve around autonomy. It is unrealistic to expect a pilot to physically man the joystick of a spacecraft during the vast majority of its mission, and the distances are simply too vast, and speeds too great for human reaction time, regardless of how augmented those human operators may be. Instances of direct human control during interplanetary flight are rare and generally limited to atmospheric reentry or manual override scenarios. When considering objectives such as moving cargo between distant points in space, performing proximity operations and docking in arbitrary orbits, and navigating and landing on celestial bodies without spaceports, communications infrastructure, or landing lights and with unknown surface properties, robust autonomy transitions from a luxury to a mission-critical requirement.

Legacy deep-space guidance, control and navigation (GN&C) methods, which rely heavily on ground-based sequencing schemes, are intolerant to unplanned events or off-nominal scenarios. Some examples of these include the Mars Climate Orbiter, which plunged to its destruction due to human error, specifically a confusion between SI and imperial units; the loss of Israel's Beresheet lander due to a loss of communications with ground stations and a lack of onboard autonomy; the near-loss of the CAPSTONE mission due to a stuck thruster and an inability to perform onboard fault detection and isolation; the recent loss of the ispace HAKUTO-R lander due it misidentifying a faulty sensor that was actually providing correct elevation data, leading to it hovering thousands of feet above the lunar surface until fuel was depleted and it plunged to its destruction. What these missions have in common is that all of them could have been spared these hardships if the spacecraft had been equipped with more robust onboard autonomy and the ability to make its own decisions in the absence of valid commands from ground stations.

Implementing this capability, however, presents several significant technical challenges. Computational limitations of flight-proven systems and the challenge of developing and proving more capable, radiation-hardened equipment are significant bottlenecks. Equally important, however, is the development of theoretical methodology that can handle the numerous constraints of real spaceflight. One approach begins by considering the special Euclidean group SE(3). SE(3) is a smooth manifold and Lie group representing the space of 3-dimensional rigid-body transformations, comprising of a semidriect product of SO3 (rotations) and $\mathbb{R}^3$ (translations). This formulation is especially advantageous during scenarios in which there is an unavoidable nonlinear coupling between translational and rotational motion. Examples of these scenarios are vehicles experiencing solar radiation pressure, gravity gradient torques, and relative motion problems such as rendezvous, proximity operations, and docking. SE(3)'s use of rotation matrices avoids the singularities of Euler angles and the unwinding issues associated with quaternion representations.

Recent work has explored these benefits within the geometric mechanics framework, demonstrating that robust filtering is possible using an unscented Kalman filter (UKF) on SE(3) and its tangent bundle \TSE. Furthermore, a novel filtering method in the field of rigid body dynamics, the discriminative Kalman filter (DKF), has also been developed on SE(3), and extended to include discriminative methods using the unscented transform, called the discriminative unscented Kalman filter (DUKF). It has been demonstrated in simulations that these methods are effective for spacecraft GN&C even in the presence of large measurement and process noise. This has been taken a step further - in the estimation of not only of states, but of parameters such as mass properties and moments of inertia, and even components of dynamical environments such as gravitational parameters and nonspherical elements.

As these methods have been developed over the last five years, simplifying assumptions have been relaxed, and an increasing degree of realism has been worked into the simulations. This has provided a necessary bridge between theory and application as we prepare to test some of the methods discussed herein on flight hardware - namely JAXA's HTV-X spacecraft and the Dragon XL deep space logistics vehicle. Both of these vehicles must consider of not only mass property uncertainties, but also the changing values of those mass properties. Circumstances such as fuel depletion, slosh dynamics, and oscillations of solar panels and antennae may cause the controller currently used in this field to become unstable. To address these and other challenges, an extension of a Morse-Lyapunov controller to consider tracking control, changing mass properties, and even thermal loads is demonstrated herein.

This thesis introduces a framework for the implementation of autonomous guidance, navigation, and control for spacecraft systems in the presence of broad state and parameter uncertainties. It introduces a methodology for the estimation of states, parameters, and even dynamic environments, and a method for simultaneous control of all six degrees of freedom even in the presence of those uncertainties. This work does not claim universality, but rather provides a robust set of tools applicable across a wide range of realistic scenarios. A skilled engineer may apply these tools to achieve the results they seek with only some gain tuning, a set of broad yet realistic assumptions, and a solid understanding of their measurement model.

Download

Share

COinS