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Daniel Guggenheim School of Aerospace Engineering

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Analytical Model for Sparing Policy Analysis and Optimization for Space Habitat Operations

2024-08 , Maxwell, Andrew J. , Ho, Koki

The inclusion of operational sparing policies in early system definition can ensure that spares’ allocations can optimally meet desired system reliabilities consistent with the planned maintenance of a crewed vehicle. This approach is critical for long-duration crewed missions where mass allocations are constrained and lack of safe abort contingencies limit options in the event of significant system degradation, especially in the environmental control and life support systems. This paper presents an analytical model for analyzing and optimizing sparing policies as part of an overall evaluation of the probability of sufficiency for a system configuration. The repair transition parameters are varied to change the state visitation probabilities that drive a change in the probability of sufficiency observed for a given mass allocation. These parameters are optimized using a particle swarm optimizer to identify the preferred strategy for a desired allocation mass.

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Uncertainty-Based Methodology for the Development of Space Domain Awareness Architectures in Three-Body Regimes

2024-04-29 , Gilmartin, Matthew Lane

The past decade has seen a massive growth in interest in lunar space exploration. An increase in global competition has led a growing number of countries and non-governmental organizations towards lunar space exploration as a means to demonstrate their industrial and technological capabilities. This increase in cislunar space activity and resulting increase congestion and conjunction events poses a significant safety impact to spacecraft on or around the moon. This risk was demonstrated on October 18th 2021 when India’s Chandrayaan 2 orbiter was forced to maneuver to avoid a collision with NASA’s Lunar Reconnaissance Orbiter. In order to mitigate the safety impacts of increased congestion, enhanced space traffic management capabilities are needed in the cislunar regime. One foundational component of space traffic management is space domain awareness (SDA). Current SDA infrastructure, a network of earth-based and space-based sensors, was designed to track objects in near-earth orbits, and is not suitable for tracking objects in distant, non-Keplerian cislunar orbits. As a result, new infrastructure is needed to fill this capability gap. The cislunar regime presents a number of challenges and constraints that complicate the SDA architecture design space. Unlike the near-earth regime, cislunar space is a three-body environment, violating many of the simplifying assumptions and models that are used in the near-earth domain. Furthermore, instability in cislunar dynamics means that state uncertainty plays a much more dominant role in system performance. This research identified three technology gaps exposed by the transition to the cislunar regime, that impede the ability of designers to explore the design space and perform many-query analyses, such as design optimization. A new uncertainty-based methodology was then proposed to both address these gaps and enhance design space exploration. The first technology gap identified was a reliance on three-body dynamics violate analytic two-body models of spacecraft motion, meaning that cislunar trajectories must be numerically integrated at much greater computational cost. A method was proposed that combines surrogate modeling techniques with and orbit family approach to develop an analytic parametric model of spacecraft motion. An experiment was carried out in order to interrogate the efficacy of this approach. Multiple surrogate models were generated using the approach, and each was compared to the state-of-the-art numerical integration approach. The surrogate modeling approach was found to greatly reduce the computational cost required to determine the initial state of an arbitrary periodic cislunar trajectory, while maintaining comparable accuracy to existing full-order methods. Of the surrogate model formulations tested, the interpolation methods were found to have the best combination of accuracy and speed for the proposed application. The second technology gap identified was a reliance on Gaussian distributions in most tracking filter implementations. In non-linear domains such as the cislunar regime Gaussian distributions may deviate from a Gaussian shape when propagated through the system's non-linear dynamics. This creates convergence issues that limit the robustness of tracking schemes that rely on Gaussian characterizations of uncertainty. This in turn creates a need to characterize the realism of Gaussian uncertainty approximations of potentially non-Gaussian uncertainty distributions. The characterization of uncertainty realism was identified to be a computationally intensive process, limiting the breadth of potential design space exploration. To ameliorate this issue a surrogate modeling process was proposed for the development of models to characterize the realism of uncertainty estimates produced by tracking filters. An experiment was executed to evaluate the efficacy of this approach. The surrogate modeling process was found to greatly improve the computational cost of the full-order analysis. While the surrogate models were found to have non-negligible errors, these errors were on the same order of magnitude as the variability of the full-order model. Of the models tested, the model based on boosted decision trees was found to have the best balance of speed and accuracy. This massive increase in computational efficiency enables designers to evaluate much larger volumes of design cases using the same hardware. The third identified technology gap was the exponential increases in the computational cost required to evaluate tracking uncertainty using full-order cislunar SDA simulations, as the number and diversity of systems in an SDA system increases. As a result of this ballooning computational cost, detailed uncertainty quantification can rapidly become intractable in a many-query analysis context, limiting the scope of design space exploration and uncertainty quantification. A surrogate modeling method was proposed to provide a volumetric assessment of tracking performance at reduce the computational cost compared to existing methods. As part of this proposed approach, changes in tracking uncertainty were evaluated with respect to the search volume. Changes in uncertainty were evaluated using a novel equivalent radius metric to estimate the rate of information gain of information gain for individual sensor systems which is then aggregated for the overall architecture. As part of this approach, field surrogates and reduced order models were investigated as potential techniques to improve the computational cost and quality of the generated surrogate models. An experiment was performed to investigate the efficacy of the proposed method in comparison to the existing methods. The generated surrogate models were found to significantly reduce the computational cost of the tracking analysis. Furthermore, this experiment found scalar surrogate models to provide the most accurate modeling of the full-order models. The field surrogates generally under-performed their scalar counterparts in terms of goodness-of-fit. Of the models tested, the scalar boosted decision tree model was found to have the best balance of speed and accuracy. In practice, this model offered was able to reduce the computational cost of evaluating SDA architecture tracking performance by several orders of magnitude, enabling designers to increase the breadth of design space exploration by similar orders of magnitude. Finally, each of the developed modeling approaches were integrated into a unified methodology, named VENATOR, to evaluate \gls{SDA} architectures. A demonstration experiment was proposed, wherein the proposed VENATOR uncertainty-based methodology was compared to a state-of-the-art methodology using equivalent full-order analyses. The experiment was broken into two phases. In the first phase, both frameworks were used to evaluate the same architecture. Next, in the second phase, the VENATOR uncertainty-based methodology was used to evaluate a simple optimization problem. The first phase of this analysis found the VENATOR uncertainty-based methodology to offer an improvement in computational cost of over three orders of magnitude. During the second phase, a simple optimization was run using the VENATOR uncertainty-based methodology, evaluating over 82,000 cases in a total of 1.6 days. A short design space exploration was carried out, identifying the Pareto front of non-dominated cases, to demonstrate the utility of this approach. Using the run time of the state-of-the-art system when evaluating a single architecture, it was estimated that using this reference methodology would have taken over 14 years to evaluate the same number of cases using the same hardware. This massive increase in computational efficiency allows designers to greatly increase the breadth of design space exploration, enabling them to examine far larger case loads, reducing design risk and increasing design knowledge. For this reason, the uncertainty-based methodology was deemed to be a significant improvement over the state-of-the-art methodologies.

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An Approach for Risk-Informed UAS Mission Planning in Urban Environments to Support First Responders

2024-04-27 , Pattison, Jeffrey T.

The past decade has seen a tremendous increase in the use of Unmanned Aerial Systems (UAS). What was once exclusively used by the military is now a critical component for a wide range of applications, including deliveries and logistics, construction, and law enforcement. Police departments around the world are beginning to see the potential UAS have for responding to emergency events. These UAS can reduce response times, be used to deescalate events, and provide crucial information to ground personnel prior to arrival. However, introducing UAS provides significant difficulties. Human operators and pilots are required to ensure safe operations and regulatory compliance. The Federal Aviation Administration has imposed strict regulations on the use of UAS in populated areas, restricting the autonomous capabilities of UAS. For UAS to be able to operate more autonomously with less human input, additional safety measures and assurance of acceptably safe operations are required. This thesis explores how to incorporate risk assessment into UAS mission planning for emergency response to introduce additional safeguards without significantly sacrificing the UAS response capability. The major areas of research studied in this thesis include UAS risk estimation methods, UAS route planning with risk incorporated, and optimizing a system of UAS to respond to emergencies when risk is considered. Because UAS are relatively new compared to manned aircraft, UAS lack historical flight data required for risk assessment like manned aircraft. A new machine learning model is proposed that can be used for evaluating UAS risk in a more time efficient manner than the physics-based modeling and simulation methods commonly used for risk estimation. Response time is critical for emergency events, and the route a UAS takes to reach the emergency directly affects its ability to respond. This work also studies various route planning methods that can account for UAS risk to find a suitable route planning configuration that meets the demands for using UAS as a first responder. Another critical component to the response time is intelligently selecting UAS launch locations. The performance of Integer Linear Programming, Genetic Algorithms, and a hybrid algorithm are compared to determine the most suitable method for finding the optimal launch locations to minimize response time for a system of three UAS when ground risk is incorporated into the emergency response route planning. Using a software in the loop flight simulator and a vehicle simulation environment, an overarching experiment demonstrates the effectiveness of the proposed approach for incorporating risk into mission planning to see how the proposed approach impacts UAS emergency response.

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Methodological Improvements for the Integration of Spacecraft Trajectory Optimization into Conceptual Space Mission Design

2024-04-27 , Bender, Theresa Elizabeth

As humans continue to send spacecraft further into space and explore uncharted territories, the implementation of space mission design becomes of paramount importance. Trajectory design and optimization is a key element of space mission design that provides information on the specific route a vehicle will take, as well as numerical estimates pertaining to fuel consumption and transfer time. Due to the complexity, high computational costs, and long runtimes of high-fidelity trajectory analyses, less accurate methods are typically used. Low-fidelity estimates provide sufficient accuracy for initial analyses; however, they often lack valuable information about the trajectory that is important to consider during the conceptual design phase. The overall objective of this research is to develop methodological improvements for spacecraft trajectory design and optimization that provide increased flexibility and better enable trajectory considerations to be incorporated into conceptual mission design studies. This research proposes a design space exploration-based approach to the integration of trajectory design and optimization into conceptual space mission design. It aims to provide a strong characterization of the design space and understanding of the problem behavior, as well as be better suited for early phase design studies that possess unknown or evolving mission requirements. The first phase of this research introduces a design of experiments and sensitivity analysis into the traditional trajectory design process in order to identify the behaviors, sensitivities, and trends of trajectory optimization problems. A regression-based approach for the selection of initial guesses is proposed in order to perform more efficient design studies and gain additional insight about the relationships between variables. The second phase of this research investigates the integration of additional evaluation criteria, namely robustness and sensitivity analyses, that are often performed independent of the trajectory design problem. A methodology is proposed for their quantification and integration into design space exploration studies so that they may be analyzed and visualized alongside performance-based metrics. The third phase of this research integrates mission design considerations into this parametric environment through the superimposition of constraints onto the design space, which results in a set of feasible trajectories that meets performance, robustness, stability, and mission design requirements and constraints. The overarching methodology is then applied to a cislunar demonstration in order to illuminate how its application results in trade studies between trajectory design and other mission design considerations that are more comprehensive and flexible than the traditional design approach allows.

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Development of an autonomous surveying vehicle for underground lunar environments

2024-04-29 , Jagdish, Nikita

With impending plans for establishing the first long-term lunar base camp, there is a need to find sustainable habitation sites on the Moon. Discovered in 2009, underground lunar lava tubes have shown potential as future habitation sites and have been proposed for devoted exploratory missions. These underground environments could provide protection from the drastic changes in temperature, radiation, and other extreme conditions on the Moon. However, they have only been observed by lunar orbiters and little is known about their internal structure or suitability for habitable structures. Various on-ground robotic systems have been proposed to do this initial survey, but ground vehicles have a high risk of being immobilized in the event of rough terrain. This project aimed to begin the development of an Autonomous Surveying Vehicle (ASV) as a candidate to explore these lava tubes. The ASV will feature a self-contained, refillable propulsion system that provides full mobility, allowing the vehicle to explore the lava tubes with high agility and multiple short-span surveying missions. The propulsion system will utilize an inert cold gas as its propellant to preserve the natural environment and avoid contamination of any potential resources in the lava tubes. The vehicle will also be equipped with on-board sensors, such as inertial sensors and LiDAR, and an autonomous navigation system to simultaneously map and traverse the tubes. The ASV will be compact and inexpensive compared to other proposed systems, putting forth a simpler option for an initial survey of the tubes to determine whether a more extensive exploratory mission is warranted. The vehicle will also be applicable for other surveying missions, such as above-ground environments that are inaccessible or hazardous for rovers and humans. This thesis outlines the mission goals and requirements and begins the development of a prototype cold gas propulsion system for the ASV.

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Permuted proper orthogonal decomposition for analysis of advecting structures

2024-04-27 , Ek, Hanna Maria

This work is motivated by the large and ever-increasing amounts of data from studies in experimental and computational fluid dynamics, and the desire to extract and analyze coherent structures from such datasets. Specifically, this thesis is concerned with vortex patterns in turbulent shear flows, which appear as advecting structures in planar measurements or slices through three-dimensional computational domains. Space-only proper orthogonal decomposition (POD) is one of the most widely used techniques for the analysis of coherent structures and decomposes mean-subtracted data into the space-time separated form q^' (x,t)=∑_j =〖a_j (t) ϕ_j (x) 〗. This method is optimal in the spatial inner product and targets high energy spatial structures, but it is sensitive to input data alignment and cannot effectively handle translations. This work applies a re-orientation of the space-time coordinates in the POD framework, and the modified POD method, referred to as permuted POD (PPOD), is the focus of this thesis. PPOD decomposes data as q^' (x,t)=∑_j =〖a_j (n) ϕ_j (s,t) 〗, where x=(s,n) is a general spatial coordinate system, s is the coordinate along the bulk advection direction in curvilinear space, and n=(n_1,n_2 ) are the mutually-orthogonal directions normal to s. PPOD is optimal in the s,t inner product and, thus, targets advecting structures via their s,t correlations. Specifically, the PPOD modes, ϕ_j (s,t), portray advection as diagonal features in s,t space, where the slope of the features corresponds to the phase speed. Hence, these speeds are a natural output of the decomposition and can vary in an arbitrary and dispersive manner along the s coordinate. Generally, the PPOD modes have arbitrary s,t dependences, and a single mode can describe a broadband or multi-frequency disturbance, as well as time-varying characteristics, such as transient and intermittent dynamics. Additionally, one- and two-dimensional Fourier transforms of the PPOD modes provide useful alternative ways to portray the modal characteristics. For example, the wavenumber-frequency spectrum provides a compact visualization of disturbance advection velocity or dispersion. The PPOD properties are considered through the analysis of data from three high Reynolds number advection-dominated flows: an acoustically forced reacting wake, a swirling annular jet, and a jet in cross flow (JICF), and the results are compared with those from space-only POD. In the wake and swirling jet cases, the leading PPOD and space-only POD modes focus on similar features: advecting shear layer structures. However, low-rank approximations of the wake flow, which is characterized by a broad range of spectral and wavenumber content, show clear differences in the methods’ ability to capture the spatial and temporal information. For equal low-rank approximations, space-only POD provides higher-fidelity spatial reconstructions, while PPOD provides higher-order frequency content. In contrast, the leading PPOD and space-only POD modes for the JICF datasets capture different types of flow structures: advecting shear layer vortices (SLVs) and bulk jet flapping, respectively, while the SLVs are spread over lower energy modes in the case of space-only POD. This shows that the s,t inner product allows the PPOD method to directly target the SLVs, despite them containing a smaller fraction of the energy compared to the jet flapping. Additionally, the leading PPOD mode captures key characteristics of the SLV dynamics for each of the JICF cases, including those typical of convectively and globally unstable JICF, as well as intermittent characteristics and minor time-dependent differences or shifts in the dynamics. On the other hand, higher-order space-only POD approximations are required for comparable descriptions of these dynamics, and the rank depends on the operating conditions and stability characteristics of the JICF.

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Volatile molecular species and their role in planetary surface morphology and spacecraft design and performance

2024-04-27 , Macias Canizares, Antonio

The geologic processes that govern the surface morphology of ice-covered, airless (i.e., without atmospheres) bodies in the Solar System have gained increasing interest over the past several decades, both for the scientific questions such worlds present, and for the relevance for future in-situ exploration. Though engineering capabilities for landing spacecraft, such as terrain relative navigation and hazard avoidance, can mitigate against meter and sub-meter scale hazards, it is nevertheless important to understand the morphological evolution and steady state of the surface ice on these worlds. Considerable work has been dedicated to the large- and small-scale geology of these worlds, but much remains to be understood about the centimeter- to meter-scale morphology of these icy, cryogenic (~100 K) surfaces. One specific hypothesis, is that blade-like structures, called penitentes, form on the surface of Europa, and rise up to 15 meters in height, though it has been argued that the physics of penitente formation, as applied for such a hypothesis, does not apply to the exosphere and surface conditions of Europa. Interestingly, penitente-like structures have been observed on Pluto, which does have a significant, albeit seasonal, atmosphere. Penitentes are also predicted to form under certain conditions on Mars though they have yet to be observed. On Earth, penitentes are made from compact snow or ice and achieve quasi-stability in high-altitude, low-latitude regions, as the result of sublimation and melting processes, and importantly, they only occur in regions of net sublimation (or melting) loss of water. Penitentes are erosional features that form as a series of corrugated ridges and troughs that run parallel to the path of the Sun across the sky, and mature structures often yield fields of individual spikes or blades, which bear some resemblance to a pair of hands praying toward the Sun, hence the name ‘penitentes.’ The first sightings of penitentes date back to the era of Darwin, who, on a perhaps anecdotal note during his travel through Chile and La Plata, described the characteristic shape of penitentes as “...pinnacles or columns...,” and hypothesized their formation process: “...the columnar structure must be owing to a ‘metamorphic’ action, and not to a process during deposition.” As it turns out, Darwin was correct since deposition during snowfall is the end of the life cycle for a penitente field on Earth. More importantly, Darwin described in his journal the possible hazards for travel and commerce as he experienced different scenarios during his journey. Darwin attributed the discovery of Penitentes to Scoresby and later to Colonel Jackson. Nevertheless, the true discoverers were the local inhabitants who had already named places like Cerro de los Penitentes (Hill of the Penitents) and Rio de los Penitentes long before Darwin arrived. It should be noted that during the XIX century, these snow structures might not have been locally referred to as penitentes, and even nowadays, the name penitentes is often termed after the physical process causing their formation and not their characteristic shape. Hence, places such as the Cerro de los Penitentes were most likely named after the penitents (repenting people) from the church. To advance our understanding of the surface morphology of airless, ice-covered worlds, and to address the limitations of current models, the work in this dissertation focused on developing numerical models that accurately represent the irradiance and physical evolution of ice on such worlds and used those models to investigate the possible presence of penitentes on Europa and their hazardous implications for a future lander.

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An Investigation of the Susceptibility and Practical Mitigation of Pitch-Roll Resonance in Fin-Stabilized Liquid Sounding Rockets

2024-04-29 , Nagarajan, Rithvik

Sounding rockets are suborbital vehicles designed to carry scientific payloads and perform experiments in the upper atmosphere. Recently, there has been a focus on reusable liquid sounding rockets to allow faster launch rates and lower costs per mission. Georgia Tech’s Yellow Jacket Space Program aims to contribute to this field by developing a series of liquid rockets with the goal of launching a sub-orbital payload to the Karman line. One of these rockets, Darcy II, experienced a catastrophic anomaly mid-flight. Like other fin-stabilized sounding rockets, Darcy II was designed with a high length-to-diameter ratio for drag optimization. This made the craft susceptible to roll-yaw resonance, where the vehicle spins close to the pitch natural frequency. Previous literature has shown roll-resonant vehicles can exhibit abnormal rolling and yawing motion beyond predictions by linear theory. Referred to as roll lock-in and catastrophic yaw, respectively, these effects can cause an excessive angle of attack and induce high structural loads. This thesis investigates the susceptibility of liquid sounding rockets to roll resonance, using the Darcy-Series rockets as case studies. Drawing from previous literature on roll resonance dynamics, additions are made to a 6DOF numerical simulation – integrating fluid models, configurational asymmetries, and non-linear aerodynamics with Monte Carlo variables. A sensitivity analysis on model components highlights characteristics of liquid rockets that influence roll resonance. This research examines the contribution of roll resonance to the Darcy II anomaly and through this, validates the numerical simulation. Subsequently, a Monte Carlo simulation is established as a practical method to assess the susceptibility of future liquid sounding rocket designs to the roll resonance phenomenon. This method is applied to the Darcy Space design, revealing a high susceptibility to roll resonance. Mitigation strategies are presented by analyzing the effect of fin design and configurational asymmetries on simulation outputs. Additionally, a simple roll control scheme is designed that takes advantage of existing liquid rocket infrastructure. Four attitude control thrusters are fired once in pairs, implementing a bang-bang roll control scheme designed to prevent roll lock-in using minimal amounts of propellant. This research evaluates the effectiveness of this control system in mitigating roll resonance issues.

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Modeling and Simulation of Flow Transients inside a Multi-Stage Axial-Centrifugal Compressor

2024-04-27 , Jing, Zhenhao

In this work, an unsteady mean line flow model for multi-stage axial and centrifugal compressors is developed, where the blade rows, i.e., rotors and stators, are modeled as successive diffusing stream tubes in their own stationary or rotating reference frames. Thus, the compressor flow is “driven” by the added velocity at frame transformations instead of being driven by a user-input aerodynamic force, which is perpendicular to the flow direction. The developed mean line flow model features a series of physics-based modeling approaches that distinguishes itself from most unsteady compressor models. The aforementioned frame transformations between stationary and rotating reference frames are accommodated by inter-domain boundary conditions (interfaces), which allow acoustic waves to propagate the discontinuity in flow properties created by the frame transformation. Such a discontinuity accommodated by the interfaces is also used as a compact loss zone to include various loss models intended to capture the individual physical phenomenon. Thus, the energy addition at frame transformations and the loss models jointly predict the compressor aerodynamic performance, hence removing the need for user-input compressor performance. A series of steady-state and unsteady simulations are performed and presented. Several sensitivity studies on selected individual loss models are presented for steady-state simulations to reveal their influence. During compressor rig tests, the flow transients are simulated to investigate the surge process and choke/unchoke response. A novel rig test approach enabling measurement of equilibrium characteristics on the unstable side is proposed and simulated. In order to simulate compressor flow transient in real working conditions in a gas-turbine engine, a lumped-parameter combustor-turbine model is developed and coupled with the compressor model. Such an approach enabled the simulation of gas turbine transients, including fast engine acceleration and deceleration and the effects of heat transfer in those engine transients. A novel active energy management strategy, which uses an electric starter/generator (ES/G) to enhance gas turbine acceleration, is proposed and simulated. A similar approach using ES/G to assist recovery from surges is also examined by simulation, and the necessary ES/G power for such a task is evaluated.

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Autonomous and Robust Monocular Simultaneous Localization and Mapping-Based Navigation for Robotic Operations in Space

2024-04-27 , Dor, Mehregan

The theoretical background, the synthesis, and the implementation details of estimation frameworks for target-relative spacecraft rendezvous and proximity operations (RPO) and small body probing and surveying (SBPS) predicated on modern simultaneous localization and mapping (SLAM) are considered. The challenges arising in the application of pure visual monocular SLAM to spacecraft relative navigation by testing an off-the-shelf algorithm, ORB-SLAM, on real satellite servicing image sequences, were identified. It is additionally determined that the inclusion of inertial measurement unit-based (IMU) factors, predominantly used in visual-inertial simultaneous localization and mapping (viSLAM), may not provide observability of the ambiguous scale or of the inertial motion over extended arcs, and moreover would not facilitate the smoothing problem. A comprehensive SLAM framework, predicated on monocular image feature point tracking and sensor fusion for on-the-fly navigation and map building is proposed. The work is contrasted to the state-of-the-art methods which instead exploit stereo imaging. A factor graph approach, allowing for the incorporation of asynchronous measurements of diverse modalities, and the inclusion of kinematic and dynamic constraints, is selected. A new relative dynamics factor predicated on the chaser-target relative orbital mechanics is devised and then augmented with the existing relative kinematics factor of Setterfield et al. to account for non-inertial motion of the target center of mass. AstroSLAM, an algorithm solving for the navigation solution of a spacecraft under motion in the vicinity of a small body by exploiting monocular SLAM, sensor fusion, and RelDyn motion factors, is proposed. The developed motion factor encodes a hybrid inertial rate gyro sensor model and vehicle dynamics model, based on the spacecraft-small-body-Sun system, incorporating realistic perturbing effects, which affect the motion of the spacecraft in a non-negligible manner. The RelDyn factor is readily specialized to the spacecraft rendezvous problem by removing the target gravitational pull variable. The data shows that RelDyn out-performs the state-of-the-art preintegrated IMU accelerometer factors, commonly used in visual-inertial SLAM solutions, in one instance of a legacy NASA small body surveying mission and in one instance of an in-lab-generated dataset. On-the-fly target dynamical parameter estimation, such as the center of mass location, the spin vector, and the gravity parameter, is also demonstrated. An existing robotics procedure, dubbed structure from small-motion (SfSM), is leveraged to tackle the challenge of map initialization with small camera baseline and weak-perspective projection

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