Master's Projects

Series

Master's Projects

Permanent Link

https://hdl.handle.net/1853/71003

Series Type

Publication Series

Full item page

Publication Search Results

Now showing 1 - 10 of 13

The Design, Assembly, and Testing of Magnetorquers for a 1U CubeSat Mission

(Georgia Institute of Technology, 2019-12-12) Amin, John

Over the next few years Georgia Tech’s Space System Design Lab (SSDL) will design and develop several 1U CubeSat missions starting with GT-1. These missions will include an Attitude Determination and Control Systems (ADCS) utilizing torque rods to control detumble and orbital attitude. This paper describes the design and construction and testing of GT-1’s torque rods and will serve as a resource to help guide future torque rod iterations. The first section details the equations and mathematics behind torque rods. Next, the design section considers factors influencing the magnetic dipole moment including core material, part length, and radius. It then describes the manufacturing and assembly process of torque rods involving core shaping and layer winding. It then describes the test setup to test the torque rod’s magnetic dipole moment and later indicates topics of future work.
X-Ray Pulsar Navigation Instrument Performance and Scale Analysis

(Georgia Institute of Technology, 2019-12-01) Payne, Jacob Hurrell

This thesis investigates instruments for autonomous satellite navigation using measurements of X-ray emissions from millisecond pulsars. A manifestation of an instrument for this purpose, called the Neutron star Interior Composition Explorer (NICER), was launched to the International Space Station in 2017. The NICER instrument was designed to observe X-ray emissions from neutron stars for astrophysics research, and is out of scale in terms of volume, power consumption, mass and mechanical complexity to be useful for small satellite missions. This work surveys the range of existing X-ray observation missions to tabulate collecting areas, focal lengths, and optical configurations from milestone missions which describe the evolution of the state of the art in X-ray observatories. A navigation demonstration experiment, called the Station Explorer for X-ray Timing and Navigation Technology (SEXTANT), was conducted using the NICER instrument. The experimental performance observed from NICER through the SEXTANT navigation demonstration is compared to theoretical predictions established by existing formulations. It is concluded that SEXTANT benefits from soft band (0.3-4 keV) exposure to achieve better accuracy than predicted by theoretical lower bounds. Additionally, investigation is presented on the readiness of a navigation instrument for small satellites using compound refractive lensing (CRL) and derived designs. X-ray refraction achieves a much shorter focal length than grazing incidence optics at the expense of signal attenuation in the lens material. Performance estimates and previous experimental results are presented as a baseline for physical prototypes and ix hardware testing to support future development of a physical instrument. The technological hurdle that will enable this tool is manufacturing precise lenses on a 3- micron scale from materials like beryllium with low atomic mass. Recent X-ray concentrator concepts demonstrate progress towards an implementation that can support a CubeSat scale navigation instrument optimized for soft band (0.3-4 keV) X-rays
Mahalanobis Shell Sampling (MSS) method for collision probability computation

(Georgia Institute of Technology, 2019-12-01) Núñez Garzón, Ulises E.

Motivated by desire for collision avoidance in spacecraft formations, and by the need for accurately computing low kinematic probabilities of collision (KPC) in spacecraft collision risk analysis, this work introduces an algorithm for sampling from non-degenerate, multidi mensional normal random variables. In this algorithm, the analytical relationship between certain probability density integrals of such random variables and the chi-square distribution is leveraged in order to provide weights to sample points. In so doing, this algorithm allows direct sampling from probability density “tails” without unduly penalizing sample size, as would occur with Monte Carlo-based methods. The primary motivation for the development of this algorithm is to help in the efficient computation of collision probability measures for relative dynamic systems. Performance of this method in approximating KPC waveforms is examined for a low-dimensionality dynamic example. However, this method could be applied to other dynamic systems and for probability density integrals other than collision probability measures, allowing for efficient computation of such integrals for problems where analytical results do not exist. Therefore, this method is suggested as an alternative to random sampling algorithms such as Monte Carlo methods or the Unscented Transform.
Closing the Power Budget Architecture for a 1U CubeSat Framework

(Georgia Institute of Technology, 2019-05-01) Tadanki, Anirudh

A 1U CubeSat framework is designed as a baseline for future missions at Georgia Tech’s Space Systems Design Laboratory. The goal of the initial CubeSat is primarily educational, and future iterations intend to demonstrate a low cost and repeatable life-cycle process that overcomes the high turnover of labor faced by most universities. The purpose of the initial CubeSat design is to return detailed ADCS data from the reaction wheel, magnetorquers, and GPS on board. Due to the volume constraints of a 1U form factor, the presented power budget features various power profiles aimed to maximize the lifetime of the CubeSat from a deployment in an orbit similar to the ISS. From this, pointing requirements for the ADCS system can be derived to maximize solar panel exposure to sunlight, and future 1U CubeSats have a better understanding of the tight margins present in the design.
Development of Maneuverable Deep Space Small Satellites

(Georgia Institute of Technology, 2019-05-01) Wilk, Matthew D.

Propulsion systems of some form are required for most CubeSat missions looking to venture beyond Low earth Orbit (LEO). The Lightsey Research Group has been producing additively manufactured satellite thrusters for various missions since 2012 and is experi enced in their designing, manufacturing, testing, and operation of such systems. These thrusters traditionally have been printed using stereolithography (SLA) methods, but new metal printing techniques allow for the use of traditional aerospace aluminum alloys. Metal printing of thrusters allows for the combining of satellite structure with propulsion system piping and tanks contained within the satellite. This research examines the design process for a 1U additively manufactured satellite with propulsion designed into the structure, the design and simulation of a new feedback control scheme for angular momentum manage ment, and documents the efforts made towards radiation tolerant electronics. The sum of works contained within are towards the common goal of enabling more beyond LEO CubeSats.
Coulomb-Force Based Control Methods for an n-Spacecraft Reconfiguration Maneuver

(Georgia Institute of Technology, 2018-05-01) Swenson, Jason C.

In an electrically-charged space plasma environment, spacecraft Coulomb forces are shown as a potential propellant-free alternative for an n-spacecraft formation reconfiguration maneu ver with nd deputy spacecraft. Two Coulomb force based methods (and one method without Coulomb forces) for reconfiguration maneuvers are developed, tested, and evaluated. Method 1a applies Direct Multiple Shooting in order to calculate the optimal thrust inputs of a min imum fuel trajectory. Method 1b uses the results from Method 1a to compare the optimal thrust input to the set of all possible resultant Coulomb force vectors at each point in time along a trajectory. Method 2, formulated from optimal control theory, solves directly for nd spacecraft charge states at each point in time with Clohessy-Wiltshire relative dynamics and minimizes the final relative state vector error. The overall performance of Method 2 is shown to be superior than that of Method 1b in terms of both relative state vector error and total computational time. Furthermore, Method 2 shows performance comparable to the optimal minimum fuel trajectory calculated in Method 1a.
Algorithmic Insufficiency of RSSI Based UKF for RFID Localization Deployment On-Board the ISS

(Georgia Institute of Technology, 2018-05-01) Carnes, Joshua T.

This work evaluates the application of Unscented Kalman Filter (UKF) to generate stochastic localizations of radio frequency identification (RFID) chips in a sensor poor, highly reflective environment. Localization is done through the application of kNN algorithms and UKF methods to assign to reference RFID tags. The research is conducted in response to the needs of NASA for an application on the International Space Station. While the UKF has been shown to be effective on RFID streams, the sensor poor environment and difficult conditions aboard the ISS cause a loss of localization. This work shows that a UKF alone is insufficient for deployment on the ISS and proposes an alternative. Validation methods are proposed, and initial results are generated. Current industry methods are explored as benchmarks for algorithm performance.
Analysis of an Aerotorquer for the Control of CubeSats with Large Torque Requirements

(Georgia Institute of Technology, 2018-04-27) Heron, Matthew R.

Traditionally, Earth-pointing CubeSats have Attitude Control Systems (ACS) that consist of two primary types of actuators – reaction wheels and magnetorquers. Reaction wheels provide the fine attitude control while the magnetorquers prevent reaction wheel saturation. This control scheme may not always meet CubeSat mission requirements, however, for some missions require a spacecraft with a large angular momentum (e.g. CubeSats with spinning instruments). In this case, the gyroscopic stiffness induced by the angular momentum will impose large torque requirements on the ACS to maintain Earth-pointing. This torque requirement on the reaction wheels may cause the wheels to spin up to saturation before the magnetorquers can unload the reaction wheel momenta. This paper analyzes the ACS feasibility and design of a 12U dual-spinning, nadir-pointing satellite. Two distinct ACS schemes are considered. In the first control scheme, the embedded angular momentum of the satellite is offset by a momentum wheel. In the second scheme, the use of an aerotorquer (i.e. drag panel) to provide the required torque is considered.
A Statistical Analysis and Predictive Modeling of Safing Events for Interplanetary Spacecraft

(Georgia Institute of Technology, 2018-04-27) Pujari, Swapnil R.

Unexpected spacecraft failures and anomalies may prompt autonomous on-board systems to change a spacecraft’s state to a ‘safe mode’ in order to isolate and resolve the problem. Future interplanetary missions such as Psyche and the proposed Next Mars Orbiter mission concept, plan to use solar electric propulsion on-board. Continuous operation of the thrusters is necessary in order to achieve their mission objectives. The mo tivation for this paper stems from a need to better predict safing events based on various mission factors such as mission class, destination, duration, etc. Modeling spacecraft inoperability due to a spacecraft entering safe mode is imperative in order to appropriately allocate spacecraft margins and shape design & operations requirements. This paper contributes to the area of safing events by further analyzing trends and dependencies within the available data subsets, and develops predictive models of frequency and recovery times of safing events for interplane tary spacecraft missions. First, the full safing event dataset is split into multiple subsets based on various mission classifiers. By employing the Chi Squared hypothesis test, the degree of dependency between classifiers is assessed. A parametric analysis is conducted using a single and mixture of two Weibull distributions. The optimal parameters that would best fit the full dataset and subsets are computed by a maximization likelihood algorithm. The mean square error and Akaike Information Criteria represent goodness-of-fit criteria for the computed distributions; insight into any inherent bi-modal behavior is identified through these criteria. A supervised learning algorithm is utilized in captur ing and understanding relationships between input and output variables, and utilizing these to predict unknown outcomes. For the safing event database, two Gaussian process models are trained, tested, and deployed: one for time-between-events and the other for recovery durations. By incorporating these Gaussian Process models into a mission simulation framework, a Monte Carlo simulation of the likelihood of inoperability rates is conducted to robustly predict safing events. A greater understanding of the safing event dataset through statistical & parametric analyses, and the development of a Gaussian Process model for predictions enables interplanetary mission planners to make more informed decisions during spacecraft development
Design, Analysis, and Simulation of Attitude Controllers for the MicroNimbus Mission

(Georgia Institute of Technology, 2018-04-20) Li, Jian H.

MicroNimbus is a small satellite mission currently under development at Georgia Tech Space System Design Lab. Its mission is to measure the vertical temperature pro le of the atmosphere. To achieve mission success, the satellite needs to control its attitude in di erent modes throughout the mission, which has motivated a development of several attitude controllers. These controllers include a B-dot controller for detum ble mode, a Nadir-Pointing controller for science mode, a Slew controller for ground station down-link mode, a Sun-Pointing controller for battery charging mode, and a User-De ned Pointing controller for calibration mode. These controllers are designed based their functionality, and the stability characteristics in the closed-loop system. This project includes adapting, designing, and implementing the controllers on a NASA GSFC open source software 42 for a full attitude control simulation. Additionally, the project report discusses the theory behind each of controllers and how it is implemented in the simulation tool. These controllers serve as a baseline design for eventual imple mentation as ight controllers on MicroNimbus and other similar CubeSat mission in the Space System Design Lab.