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Daniel Guggenheim School of Aerospace Engineering

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https://hdl.handle.net/1853/70742

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College of Engineering

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Aerospace Design Group

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Aerospace Systems Design Laboratory (ASDL)

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Air Transportation Laboratory

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Cognitive Engineering Center

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Space Systems Design Laboratory (SSDL)

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https://finding-aids.library.gatech.edu/agents/corporate_entities/106

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Publication Search Results

Now showing 1 - 10 of 18

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, 2019-12-06) 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 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.
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.
Using sample-based continuation techniques to efficiently compute subspace reachable sets and Pareto surfaces

(Georgia Institute of Technology, 2019-11-11) Brew, Julian

For a given continuous-time dynamical system with control input constraints and prescribed state boundary conditions, one can compute the reachable set at a specified time horizon. Forward reachable sets contain all states that can be reached using a feasible control policy at the specified time horizon. Alternatively, backwards reachable sets contain all initial states that can reach the prescribed state boundary condition using a feasible control policy at the specified time horizon. The computation of reachable sets has been applied to many problems such as vehicle collision avoidance, operational safety planning, system capability demonstration, and even economic modeling and weather forecasting. However, computing reachable volumes for general nonlinear systems is very difficult to do both accurately and efficiently. The first contribution of this thesis investigates computational techniques for alleviating the curse of dimensionality by computing reachable sets on subspaces of the full state dimension and computing point solutions for the reachable set boundary. To compute these point solutions, optimal control problems are reduced to initial value problems using continuation methods and then solved. The sample-based continuation techniques are computationally efficient in that they are easily parallelizable. However, the distribution of samples on the reachable set boundary is not directly controlled. The second contribution presents necessary conditions for distributed computation convergence, as well as necessary conditions for curvature- or uniform coverage-based sampling methods. Solutions to multi-objective optimization problems are generally defined using a set of feasible solutions such that for any one objective to improve it is necessary for other objectives to degrade. This suggests there is a connection between the two fields with the potential of cross-fertilization of computational techniques and theory. The third contribution explores analytical connections between reachability theory and multi-objective optimization with investigation into properties, constraints, and special cases.
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.
Development of multi-functional structures for small satellites

(Georgia Institute of Technology, 2018-11-13) Stevenson, Terry

Improvements in miniature electronics have allowed CubeSats and other small satellites to perform increasingly complex missions. In contrast to typical space missions, many small satellites are more limited by available volume than by mass, since they must fit into small deployment pods. This available volume can be used more efficiently by taking advantage of advanced manufacturing techniques, particularly 3D printing. Hollow elements can be printed into the structure that can be used to store and transport fluid. In this way, the structure of the satellite can become multifunctional; it still provides structural support, but can also encompass fluid handling systems, such as cold gas thrusters. This concept was applied to produce a propulsion system for an interplanetary 6U CubeSat called BioSentinel. By printing the thruster from a ceramic-like material, the propellant tanks are able to fill more of the available volume than would have been possible with conventionally produced parts. Incorporating the nozzles and piping into the structure also reduces the number of pressure seals required. The BioSentinel thruster has been manufactured and tested, and will launch with the first flight of the Space Launch System in 2020. This technology was also applied to design a CubeSat structure that is entirely 3D printed, and incorporates a propulsion system into a metal structure. This improves the maneuverability of the spacecraft while also increasing volume efficiency, and allows the nozzle geometry to be optimized for specific missions. Finally, these techniques were applied to design a printed structure for a Venus atmospheric sampling probe called Cupid’s Arrow. The probe has an integrated propulsion system and a separate fluid path for collecting and storing atmospheric gas samples. This development of multifunctional structures improves the state of the art in small satellite design and enables more volumetrically efficient space missions.
Spacecraft visual navigation using appearance matching and multi-spectral sensor fusion

(Georgia Institute of Technology, 2018-05-17) McBryde, Christopher Ryan

The approach taken in this research is to apply terrestrial techniques to improve spacecraft navigation. First, appearance matching is used as a common framework for both object identification and pose estimation and is made more robust using background randomization. Consequently, a spacecraft imaging simulation environment is created to both generate the necessary training images as well as verify the systems performance. Additionally, results for multiple sensors are fused to improve the identification and pose estimation as well as increase the operating range over more of the orbit. The result of this research is that a robust method is demonstrated for object identification and pose estimation of a spacecraft target. A single framework accomplishes both tasks and may be further enhanced using multiple sensors. Appearance matching and sensor fusion will help enable the next generation of spacecraft visual navigation.
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.