2023 Presenters

View 2023 Presentation Schedule

Session 1 - April 5, 2023

Title of Research

DrMaMP: Distributed Real-time Multi-agent Mission Planning in Cluttered Environment

Abstract
Solving a collision-aware multi-agent mission planning (task allocation and path finding) problem is challenging due to the requirement of real-time computational performance, scalability, and capability of handling static/dynamic obstacles and tasks in a cluttered environment. This paper proposes a distributed real-time (on the order of millisecond) algorithm DrMaMP, which partitions the entire unassigned task set into subsets via approximation and decomposes the original problem into several single-agent mission planning problems. This paper presents experiments with dynamic obstacles and tasks and conducts optimality and scalability comparisons with an existing method, where DrMaMP outperforms the existing method in both indices. Finally, this paper analyzes the computational burden of DrMaMP which is consistent with the observations from comparisons, and presents the optimality gap in small-size problems.

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Title of Research
Mixed-Input Learning for Multi-point Landing Guidance with Hazard Avoidance Part I: Offline Mission Planning based on Multi- Stage Optimization

Abstract
This paper proposes a multi-stage optimization framework based on iterative second-order cone programming (SOCP) to solve the three- dimensional (3D) multi-point landing guidance (MLG) problem with hazard avoidance. The approach is used to generate the optimal offline trajectories for database construction in Part II of this paper, it aims to select a safe landing point while finding an optimal path to the selected landing point with minimum fuel consumption. First, by introducing binary variables associated with quadratic constraints, the MLG problem with hazard avoidance is equivalently reformulated as a quadratically constrained quadratic programming (QCQP) problem. Next, to solve the reformulated QCQP problem, a multi-stage optimization framework, which is combined with the relaxation technique, is introduced. The proposed method includes two main stages. In the first stage, the reformulated problem is relaxed into a nonconvex QCQP problem via ignoring constraints related to the binary variables, which can be solved by the proposed iterative second-order cone programming (SOCP) with random initial guess. Via solving the relaxed QCQP problem with proposed iterative SOCP, the initial guess for the second phase is generated. In the second phase, with the generated initial guess in the first phase, the proposed iterative SOCP can find the local minimum for the equivalently reformulated QCQP problem. Finally, the effectiveness of the proposed method is verified via numerical simulations.

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Title of Research
Understanding Aviation Accidents: Insights from Pilot Surveys and Interviews

Abstract
General Aviation (GA) accidents comprise approximately 94% of all aviation accidents in the United States annually. 75% of these accidents involve pilot-related factors (i.e., pilot actions or conditions). Loss of control means when the flight crew cannot maintain control of the aircraft in flight. With almost half of loss of control accidents being fatal yearly, it continues to be the deadliest cause of GA accidents. The most common approach to understanding accident causation is analyzing historical data from sources such as the National Transportation Safety Board (NTSB) database. In contrast to the extensive investigations into and detailed reports on commercial aviation accidents, GA accident investigations tend to be shorter, and the resulting reports include limited detail on the role of human factors in accidents. Only relying on historical data cannot provide a complete understanding of accident causation. Understanding specific pilot actions and the underlying conditions may help better focus GA training methods to prevent LOC-I accidents. In my research, I surveyed and interviewed pilots to investigate the role of human factors in loss of control accidents. The findings of my work may help in improving pilot training methods and operating procedures to prevent loss of control in the future.

Session 2 - April 7, 2023

Title of Research
Unlocking the Potential of Cislunar Space: Developing Reusable Infrastructure with the 2:1 Resonant Spatial Orbit Family

Abstract
To unlock the full potential of cislunar space, reliable and repeatable transit infrastructure needs to be developed. Currently, trajectory designers must create completely new trajectories for each mission, which is a time-consuming and inefficient process. To address this limitation, this work proposes the 2:1 resonant spatial (3D) family as a candidate set capable of underpinning reusable infrastructure in cislunar space. Through a detailed case study, an example using these orbits as a medium for transfer design in this system is presented, including a discussion on how these trajectories could be used with paired momentum exchange tethers to facilitate payload exchange. This could enable the fast, efficient, and repeatable transit of payloads and satellites through cislunar space without needing to design a new trajectory for every mission. Moreover, and due to the interesting properties of these orbits, they could form the foundation of a reusable space infrastructure able to transport goods and services between different locations in cislunar space, thus increasing efficiency and reducing costs while opening new possibilities for exploration and research in this region. Ultimately, the development of this infrastructure could transform cislunar space from a regime to visit into a destination to stay.

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Title of Research
Cislunar Space Surveillance using Precise Modeling and Approximate Modeling using Bi-circular Restricted Four-body Geometry for Optical Observations

Abstract
The increasing number of launches around the Moon has generated a need to surveil the cislunar space for its active utilization. Optical sensors are an effective and available mean for ground-based (Earth and Moon) and space-based observations. However, optical observations are subject to multiple visibility constraints, which are explored in detail in this paper. The cislunar parameter space for optical observations is also vast. In this paper, using these optical observations, the effects of Earth ground-based, Moon ground-based and space-based observers are examined in a precise high-fidelity model that gives only point solutions as the problem is time-dependent. Another model based on the geometry of the in-plane bi-circular four-body problem (BCR4BP) is utilized to parameterize the visibility conditions in terms of time. Through parameterization, the repeated geometry arising from the BCR4BP model can be found, which in turn, gives repeated visibility. The latter technique avoids computing point solutions and allows for a quick assessment of the entire parameter space. In this paper, a 2:1 resonant orbit is selected for illustration of both, the exact observation constraint techniques and the fast parameter space exploration.

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Title of Research
Non-Convex Shape Inversion from Light Curves

Abstract
Characterizing the shape and attitude of unknown space objects is a core capability for Space Domain Awareness (SDA). As the community’s ambition for new space operations grows, understanding shape and orientation becomes necessary for robust collision avoidance, active debris removal, and long-term orbit propagation. Due to diffraction and atmospheric turbulence, shape information cannot be resolved directly from the ground. Instead, we rely on the observed brightness over time – the “light curve” – for object characterization. While it is relatively simple to estimate a convex shape from a light curve if the attitude profile is known, the complex geometry of self-shadowing renders standard methods inadequate. We introduce a method to estimate the shape of highly nonconvex objects using a modification to Extended Gaussian Image-based methods for convex shape inversion. We establish a relationship between the convex shape closure error and the location and interior angle of prominent concavities. The convex shape is then subdivided and deformed to introduce the estimated concavity. We show that this approach is accurate for a range of nonconvex objects and can be applied to convex objects without introducing spurious shape errors.

Session 3 - April 12, 2023

Title of Research
Parametric study of impact response for an ammonium perchlorate (AP) - hydroxyl-terminated polybutadiene (HTPB) composite material

Abstract
Ammonium perchlorate (AP) and hydroxyl-terminated polybutadiene (HTPB) are the most commonly used oxidizers and polymeric binders in the aerospace solid rocket design industry. The effects of varying the microstructural properties of AP when embedded with HTPB are investigated. In this study, respectives samples of 200 µm and 400µm coarse AP crystals (75% in mass) are embedded with HTPB (25% in mass). An infrared camera in conjunction with a drop- hammer experimental setup provides the impact-induced thermal response undergone in the samples. The thermal images obtained from the camera at millisecond resolution are invaluable and provide information about temperature distribution across these sample surfaces. These images also provide insights into changes in localized heating observed by varying the particle sizes of AP in HTPB which are complex and not easily understood. Results show that variations in the particle sizes play a key role in the distribution and evolution of temperature due to the effects of varying surface area. Understanding these effects helps in selecting efficiencies for desired applications and in improving their mechanical, physical, and chemical properties.

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Title of Research
Effect of manufacturing processes on progressive damage of composites

Abstract
The manufacturing processes of composites involve complex and inter-related procedures that span across multiple physics domains and scales. When a composite undergoes curing during the manufacturing process there are residual stresses that develop in the composite in the manufactured composite part. Also, there are inherent cracks in the manufactured composite part. We aim to compare residual stresses that are developed due to the Cure Hardening Instantaneous Linear Elastic (CHILE) model, and residual stresses developed due to a simple temperature drop from the rubbery state to glassy state during the manufacturing of the composite. Then we use a continuum damage method called the Smeared Crack Approach to model the inherent cracks and account for the progressive damage in the composite as we apply a mechanical load. This approach is useful and is close to reality as it accounts for the residual stresses that arise during the manufacturing processes as well as the inevitable cracks that are formed which reduce the strength of the material.

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Title of Research
Micro Gas Turbine Optimization Through CFD Modeling

Abstract
We investigate and optimize the design of a combustion chamber and rotor within a 1 kW micro gas turbine engine. The use of ceramic 3D printing allows for more complex geometries within a tight space that can survive at high operating temperatures and maintain reasonable efficiencies. The single piece rotor contains both the compressor and turbine side rotor blades. The compressor is shown to be able to compress 20 g/s of air to 3 atmospheres while operating at 100,000 RPM. The compressed air is then directed to the main combustion chamber where 0.118 g/s of gaseous hydrogen is injected through 8 injectors. An overall fuel to air equivalence ratio of 0.2 is to be expected as we aim towards a target turbine inlet temperature of 1200 K. The use of gaseous hydrogen in this engine causes the flame to propagate considerably faster than traditional fuels. We use ANSYS Fluent to model how the air and fuel mixture react while changes are made so that we can maintain the target turbine inlet temperature without causing the walls to heat up past the operating temperature limit.

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Title of Research
Project Polaris: Globalizing Space through Innovation, Culture, and Travel

Abstract
Polaris is an international collaboration that for three years has brought more than 300 students from 30+ different countries to do space in a very innovative way. We simulate a mini-space agency that contributes to the globalization of space by creating local opportunities and promoting collaboration. Polaris is more than engineering; we provide our students with intercultural, social, professional, and even artistic experiences. Some of our achievements include: • 2+ years of theoretical online research on a buoyant rover concept for Titan (Saturn's moon) with help of mentors and panelists from NASA, ESA, SpaceX, and other companies/universities. • Two exchange programs (summers 21'/22') where we brought more than 30 internationals to Costa Rica to participate on the technical project, internships (30), volunteering, and traveling. • Built and integrated an Earth-adapted prototype of the rover in just 21 business days at the Costa Rica Institute of Technology. • Presented five papers at this year's International Astronautical Congress (IAC) in Paris and another international congress in Costa Rica (see attached). • Brought 46 Polarians from 12+ different countries to the IAC (5 of us from Purdue). • Did an artistic project in conjunction with the University of Costa Rica which was presented both in France and CR.

Session 4 - April 14, 2023

Title of Research
A Decision Support Framework for Additive Manufacturing of Space Satellite Systems

Abstract
The space industry has seen promising advance- ments in additive manufacturing (AM) technologies, including the production of rocket engines and spacecraft components. Nevertheless, AM adoption decisions are still complex due to the many considerations, uncertainties, and stakeholders involved. This paper proposes and demonstrates a decision support frame- work – including a utility theory-based decision engine that was developed in-house – to support users in evaluating AM-use options. The key decision attributes (i.e., performance, cost, and time) of a space satellite bracket assembly were identified through a requirements definition process. Utility functions representing different decision-maker risk preferences were defined based on relevant spacecraft operating conditions. Attribute data for machine-material pair options were also quantified using data sheets, AM cost, and build-time models. The utility functions, attribute values, and attribute weights were input to the decision engine software for a machine-material pair recommendation. A sensitivity analysis was conducted by varying the utility functions, attribute weights, build volume, and applying “hard constraints”. The results demonstrated the versatility and applicability of the decision framework and engine in tackling AM machine-material pair selection problems, including for the satellite design and manufacturing use case.

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Title of Research
A Resilience-Oriented Extra-Terrestrial Habitat Design Process

Abstract
The purpose of this research is to develop and demonstrate a resilience-oriented systems design process for extra-terrestrial habitats. The design process will consider characteristics of the habitat’s mission and aid designers in selecting safety features while meeting other system requirements. The result will be a standard process to design habitats that can react to, survive, and recover from both expected and unexpected disruptions. We will use two metrics to help select safety controls. Control Effectiveness measures how well a safety control addresses its target hazard. Resilience Power measures a safety control’s ability to address multiple hazards, including hazards outside its target set. In its first 3 years, the RETHi team has established an extensive database of disruptions that could affect an extra-terrestrial habitat, and safety controls that could mitigate the hazardous states that result from those disruptions. The team built the MCVT, a physics-based virtual testbed that models disruptions and safety controls. Using the metrics and the MCVT, we can compare a habitat’s expected performance when equipped with different safety features. This process will aid habitat designers in selecting which safety controls to include in a mission depending on the mission’s characteristics and the project’s constraints.

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Title of Research
Surviving the Unexpected - Designing and Implementing Safety Controls with Resilience Power

Abstract
Space habitats will face unpredictable environments while being tightly coupled and resource constrained. Therefore, it’s unlikely that the habitats can be designed with many redundant safety controls, or with safety controls that address every possible hazard. Our proposed approach helps identify controls that are likely to be effective against both foreseen and unforeseen hazards. We model systems from a state-based perspective where the system is in one of four distinct types of states at a given time: nominal, hazardous, safe, or accident. Safety controls prevent the system from entering or remaining in a hazardous or accident state or transition the system to a temporary safe state or to a nominal state. We have established an extensive database of disruptions that could affect a lunar habitat, associated safety controls, and a control effectiveness measure which evaluates the effectiveness of a safety control in addressing the hazard for which it is designed. To address the challenge of unforeseen hazards, we are developing ways to design and select sets of safety controls that effectively address hazards for which they were not originally designed. Our hypothesis is that such high “resilience power” safety controls will result in habitats with high resilience. For an initial estimate of resilience power, we implement each safety control for multiple disruptions and record its control effectiveness for each disruption. We are studying concepts from literature on flexibility and agility to refine our measure for resilience power, and to identify ways to design safety controls with high resilience power. Habitats with high resilience power and control effectiveness safety controls should be resilient to both foreseen and unforeseen hazards if our metrics are well-designed. We are testing this hypothesis by running simulations on RETHi’s three test and simulation platforms: the MCVT, CDCM, and CPT.

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Title of Research
Space X-Plain: Analysis of Space Mission Architectures Using Explainable Artificial Intelligence

Abstract
The advent of space exploration promises groundbreaking technological advances, such as on-orbit refueling and spacecraft reusability, however myriad challenges follow as a consequence. From a systems engineering standpoint, the increasing complexity of space missions calls for tools that can aid designers by providing insights on several levels of abstraction - from resources to operations and economics. Given this context, the research proposed here offers a novel methodology using Explainable Artificial Intelligence (XAI) that can assist space mission engineers in the effort of making informative decisions while understanding how different aspects of a mission can affect in their outcomes. The goal of this investigation, then, is to construct a framework using XAI and a System-of-Systems Engineering and demonstrate its application to enable frequent missions to the Moon at a lower cost than previous mission architectures, such as the Apollo program, by implementing reusable mission elements. Using the novel methodology proposed in the context of this testbed, important insights about mission portfolios could be quantitatively measured and explained. Future work, then, can benefit from the integration of these tasks into a single, uniquely defined Machine Learning explainable framework that will enable designing missions in a real scenario with significantly greater ease.

View 2023 Presentation Schedule