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 43

VISORS Mission Orbit & Dynamics Simulation Using a Realtime Dynamics Processor

(Georgia Institute of Technology, 2023-12-01) Kimmel, Elizabeth

VIrtual Super-resolution Optics using Reconfigurable Swarms (VISORS) is a precision formation-flying mission which uses two 6U CubeSats with a Science Mode separation distance of 40 meters to emulate a 40-meter focal length diffractive optic telescope. Due to the novelty of the technology used to achieve the stringent relative positioning requirements, the dynamics of these orbits must be simulated to verify the concept of operations (ConOps), the commercial spacecraft bus flight software (FSW), the guidance, navigation, and control (GNC) formation-keeping algorithm, and the attitude determination and control system (ADCS) performance, among others. Verifying these aspects helps ensure that issues such as reaction wheel saturation, pointing errors, or collision risks, among others, do not arise during the mission. This paper describes the work done in simulating the spacecraft dynamics during the mission’s Science Operations using COSMOS to interface with the Realtime Dynamics Processor (RDP) and spacecraft bus Engineering Design Unit (EDU) provided by Blue Canyon Technologies (BCT).
Development of an Autonomous Distributed Fault Management Architecture for the VISORS Mission

(Georgia Institute of Technology, 2023-08-01) Paletta, Antoine

CubeSat formations have been identified as a new paradigm for addressing important science questions, but are often early adopters of new technologies which carry additional risks. When these missions involve proximity operations, novel fault management architectures are needed to handle these risks. Building on established methods, this paper presents one such architecture that involves a passively safe relative orbit design, interchangeable chief-deputy roles, a formation level fault diagnosis scheme, and an autonomous multi-agent fault handling approach. This architecture focuses on detecting faults occurring on any member of a spacecraft formation in real time and performing autonomous decision making to resolve them and keep the formation safe from an inter satellite collision. The NSF-sponsored Virtual Super-resolution Optics with Reconfigurable Swarms (VISORS) mission, which consists of two 6U CubeSats flying in formation 40 meters apart as a distributed telescope to study the solar corona, is used as a case study for the application of this architecture. The underlying fault analysis, formulation of key elements of the fault detection and response strategy, and the implementation as flight software for VISORS are discussed in the paper.
Development of an Autonomous Distributed Fault Management Architecture for the VISORS Mission

(Georgia Institute of Technology, 2023-05-01) Paletta, Antoine

CubeSat formations have been identified as a new paradigm for addressing important science questions, but are often early adopters of new technologies which carry additional risks. When these missions involve proximity operations, novel fault management architectures are needed to handle these risks. Building on established methods, this paper presents one such architecture that involves a passively safe relative orbit design, interchangeable chief-deputy roles, a formation level fault diagnosis scheme, and an autonomous multi-agent fault handling approach. This architecture focuses on detecting faults occurring on any member of a spacecraft formation in real time and performing autonomous decision making to resolve them and keep the formation safe from an inter satellite collision. The NSF-sponsored Virtual Super-resolution Optics with Reconfigurable Swarms (VISORS) mission, which consists of two 6U CubeSats flying in formation 40 meters apart as a distributed telescope to study the solar corona, is used as a case study for the application of this architecture. The underlying fault analysis, formulation of key elements of the fault detection and response strategy, and the implementation as flight software for VISORS are discussed in the paper.
Lessons Learned in University Production of CubeSat Propulsion Systems

(Georgia Institute of Technology, 2023-05-01) Glaser, Mackenzie J.

The Space Systems Design Lab (SSDL) at the Georgia Institute of Technology (GT) designs and manufactures propulsion systems for CubeSats using green monopropellant and cold gas propulsion technologies. Over the history of building these systems, a variety of off-nominal behaviors and nonconformances have been observed including contamination by foreign object debris, higher than acceptable leak rates, and inconsistent performance. Root cause investigations have been conducted where appropriate for individual systems and the identified root causes have included manufacturing defects, incomplete cleaning processes, and improper parts sizing. This paper collects and identifies historic off-nominal behaviors and nonconformances observed in SSDL-built propulsion systems and discusses the investigations of the root causes of these behaviors. These root cause issues are outlined and compared to present suspected systemic issues in propulsion system production. Root cause issues on each unit are added up based on the larger category of cause including design, assembly and test processes, or facilities used to conduct these processes. Frequency of causes over the whole propulsion program are used to confirm trends in root causes. Based on these trends, best practices are highlighted to prevent failures on future systems and ensure the highest possible quality of hardware.
Refill Strategy for Two Tank Gold Gas Propulsion Systems

(Georgia Institute of Technology, 2023-05-01) Wood, Samuel

Cold gas propulsion systems using a saturated liquid-vapor mixture as propellant often use separate tanks for storage and actuation. The pressure of a plenum is regulated via refills from a storage tank. Without a propellant management device, simple pressure-controlled refills can inject unwanted liquid into the plenum. This phenomenon leads to unpredictable thrust and a lower-than-expected specific impulse. These undesirable characteristics are mitigated by using a model-based closed-loop refill strategy. A valve flow equation is combined with system characterization data to approximate the average mass flow between the storage tank and plenum. Refill valve opening and closing times are controlled to allow the system to reach steady state prior to refilling or actuating. Controller operation is tested and validated on integrated cold gas systems in orientations that allow either liquid or gas to be in contact with the plenum refill port. These simulated worst-case and best-case on-orbit conditions are tested across the system’s full temperature operating range. This paper describes the model development, integrated hardware testing, and improved system performance associated with the model-based plenum refill strategy. These findings enable two-tank cold gas propulsion systems using pressure-controlled refilling to deliver more repeatable system operation.
Deep Space Relay Architecture for Communication and Navigation

(Georgia Institute of Technology, 2023-05-01) Carter, Paul

The Deep Space Relay architecture explored in this paper is intended to provide communication and navigation services to Mars surface users and spacecraft in the Mars vicinity. The relay orbiters making up this architecture will be placed in strategic heliocentric orbits near Mars so as to mitigate the Mars superior conjunction problem for optical communications, and at the same time provide a good geometry for deep space navigation. Design trades are performed to ensure that the relay architecture is optimal in its roles as both a communication provider and navigation provider. Geometric constraints are identified that allow the relay architecture to provide continuous optical link coverage throughout the time period from 2030-2060. An optimal and minimal relay architecture is identified that meets these geometric constraints while also maximizing the data return of the optical link and providing a suitable geometry for trilateration-based navigation with the fewest relay orbiters possible. The communication performance of this optimal relay geometry is assessed through an analysis of the additional access time and data return it provides. On the navigation side, the performance of the optimal architecture is assessed based on access and a geometric dilution of precision (GDOP) analysis. An expanded architecture is introduced which adds a relay in a Mars halo orbit to the minimal architecture for additional communication and navigation benefits.
Operations Systems Engineering for the Lunar Flashlight Mission

(Georgia Institute of Technology, 2023-05-01) Hauge, Michael

Lunar Flashlight, a 6U CubeSat developed by NASA’s Jet Propulsion Laboratory (JPL) and operated by students at the Georgia Institute of Technology (GT), was launched in December 2022 with a mission to demonstrate novel small satellite technologies, including a first-of-its-kind green monopropellant system, and to map surface water ice in permanently shadowed regions of the lunar south pole using near-infrared laser reflectometry. While responsible for tactical operation of the spacecraft, including commanding and telemetry monitoring, GT students have also taken on strategic roles as operations systems engineers. The team has maintained, developed, and refined models of spacecraft subsystems as well as coordinated the project’s approach to anomaly response and fault protection. This paper reports how flight data and post-launch experiences have influenced the development and refinement of these models and approaches, and how in turn this systems engineering work has allowed the team to make more efficient use of the spacecraft’s capabilities, especially in dynamic anomalous situations, by taking advantage of margins, synthesizing data, and adapting flight rules and constraints. In-flight anomalies have required substantial rework of the mission’s concept of operations, and anomaly management and resolution has leaned heavily on modeling and predictions from the operations systems engineers. Working closely with JPL subject matter experts, the GT operations team has made full use of available data, including telemetry and observed system behavior, to swiftly recognize and address anomalies, support strenuous recovery efforts, and make possible a realignment of the concept of operations to achieve mission success despite significant challenges.
Best Practices and Considerations for Planning and Conducting Integration of University CubeSats

(Georgia Institute of Technology, 2022-12-01) Rawson, William

This paper seeks to serve as a resource for students entering the integration phase of a CubeSat project by compiling best practices and practical considerations from several projects in the Space Systems Design Lab at the Georgia Institute of Technology. The integration phase can be a particular challenge for university CubeSat programs given the value of practical experience in performing these activities and the challenge of managing a student workforce with constant turnover. The topics covered include best practices for planning the integration phase of a project, considerations when performing integration activities, and the characteristics of good assembly procedures. Although the focus is on spacecraft-level integration of CubeSats in a university setting, many of the considerations are applicable outside the academic setting and to subsystem-level integration activities as well. Finally, a case study will be presented illustrating the planning of integration activities for the VISORS mission, a two 6U CubeSat formation-flying mission
Integration and Testing of a 2U Cold-Gas Propulsion System for the SunRISE Mission

(Georgia Institute of Technology, 2022-08-01) Shirazi, Kian E.

The Georgia Tech (GT) Space Systems Design Laboratory (SSDL) is building six identical cold-gas propulsion systems to provide the necessary maneuvering capabilities required by the SunRISE mission. The mission plans to observe low frequency emissions from the Sun by utilizing an array of CubeSats that will formation fly to create a large radio telescope in space. The cold-gas system design is based on the lab’s heritage design used for previous missions, namely BioSentinel, which leverages additive manufacturing to create a highly optimized propulsion system for the CubeSat form factor. The unique system consists of mainly a singular printed multifunctional structure encompassing tanks, plumbing, and nozzles, and utilizes a two-phase propellant to maximize the amount of propellant stored in the restricted volume and hence the total impulse provided by the system. This report provides a brief overview of the system design and its purpose in the SunRISE mission, while detailing the integration process and extensive testing campaign each flight unit goes through before they are delivered for integration with the spacecraft.
Investigation and Analysis into Establishing a Cislunar PNT System and Performing a Soft Landing on the Lunar Surface

(Georgia Institute of Technology, 2022-05-01) Ramanathan, Keshav

With an expected increase in human activity in and around the lunar environment, Georgia Tech, along with GTRI, has proposed two projects to get involved in this sector. One project focuses on Cislunar PNT, which attempts to establish a satellite architecture for PNT in the Cislunar environment. The other project is Lunar ISRU, which desires to soft land a spacecraft on the lunar surface to perform energy capture resource utilization. For an initial phase I study, the Space Systems Design Laboratory (SSDL) team investigated currently proposed requirements and architectures from literature for a Cislunar PNT architecture. Additionally, analysis was performed to simulate a transfer from a NRHO orbit to the lunar surface through an intermediate low lunar parking orbit for Lunar ISRU. From this research, the goal for a more detailed analysis is to create a navigation algorithm simulation package to apply to the chosen system architecture for Cislunar PNT and achieve an optimal and efficient landing for the Lunar ISRU spacecraft on the Moon’s surface