| 11. |
- Bazzocchi, Michael C. F., et al.
(författare)
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Low-thrust orbit transfer of Arjuna-type asteroids
- 2016
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Ingår i: AIAA/AAS Astrodynamics Specialist Conference, 2016. - Reston, Virginia : American Institute of Aeronautics and Astronautics. - 9781624104459
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Konferensbidrag (refereegranskat)abstract
- This paper investigates the accessible low-thrust transfer trajectories for a near-Earth asteroid transfer mission. The target asteroids considered are Arjuna type asteroids, which are characterized by their Earth-like orbital paths including low-eccentricity and low-inclination. The asteroid range is characterized by specific semi-major axes and transfer angles to provide an overall assessment of the potential Arjuna transfer domain. A single hovering ion beam spacecraft is employed for the task of asteroid redirection. The method utilizes a continuous thrust over the duration of the transfer maneuver to redirect the asteroid to an Earth bound orbit. The transfer model employs a minimized form of Gauss's variational equations to determine the available trajectories for asteroid redirection. The transfer model employs, in addition to the aforementioned orbital equations, spacecraft thruster and sizing metrics, as well as mission cost analysis formulae. The system parameters and orbital transfer paths are assessed with regards to key mission parameters, namely, timeframe for redirection, number of orbital revolutions, system mass, propellant mass, thrust, power, system cost, and financial return rate
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| 12. |
- Bazzocchi, Michael C.F., et al.
(författare)
-
Stochastic optimization of asteroid three-dimensional trajectory transfer
- 2018
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Ingår i: Acta Astronautica. - : Elsevier. - 0094-5765 .- 1879-2030. ; 152, s. 705-718
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Tidskriftsartikel (refereegranskat)abstract
- In this work, an approach to designing near-optimal nonplanar transfer trajectories for asteroids is introduced, taking into account the uncertainty in asteroid parameters. The approach is demonstrated using a specific known Near-Earth Asteroid (NEA) as a model for the transfer scenario. The designed trajectory redirects the NEA from its current orbit about the Sun to a new orbit in the Earth-Moon system. The approach utilizes a low-thrust redirection method, namely the ion beam method, to execute the transfer; however, the work can be extrapolated to most low-thrust redirection methods. Asteroid parameters, such as absolute magnitude, albedo and density, are modelled, and a Monte Carlo analysis is employed to investigate the redirection maneuver in light of the expected variation in parameters. The trajectory transfer is modelled in three dimensions through the use of pseudo-equinoctial shaping, and is subsequently optimized. Due to the large design space created by the 21 decision variables, the optimization is parsed into two main steps; first, a global optimization that employs a genetic algorithm, followed by a local optimization that utilizes sequential quadratic programming to refine the result from the global optimization. Lastly, the results of the Monte Carlo analysis for the near-optimal trajectory transfer of the NEA are discussed.
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| 13. |
- Bazzocchi, Michael C. F., et al.
(författare)
-
Study of Arjuna-Type Asteroids for Low-Thrust Orbital Transfer
- 2018
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Ingår i: Journal of Spacecraft and Rockets. - : American Institute of Aeronautics and Astronautics. - 0022-4650 .- 1533-6794. ; 55:1, s. 37-48
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the accessible low-thrust transfer trajectories for a near-Earth asteroid transfer mission. The target asteroids considered are Arjuna-type asteroids, which are characterized by their Earth-like orbital paths including low eccentricity and low inclination. The asteroid range is characterized by a specific range of semimajor axes and transfer angles to provide an overall assessment of the potential Arjuna transfer domain. A single hovering ion beam spacecraft is employed for the task of asteroid redirection. The method uses a continuous thrust over the duration of the transfer maneuver to redirect the asteroid to an Earth-bound orbit. The transfer model employs a minimized form of Gauss's variational equations to determine the available trajectories for asteroid redirection. The transfer model employs, in addition to the aforementioned orbital equations, spacecraft thruster and sizing metrics as well as mission cost analysis formulae. The system parameters and orbital transfer paths are assessed with regard to key mission parameters, namely, time frame for redirection, number of orbital revolutions, system mass, propellant mass, thrust, power, system cost, and financial return rate
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| 14. |
- Emami, Reza, et al.
(författare)
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Engineering design pedagogy : a performance analysis
- 2020
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Ingår i: International journal of technology and design education. - : Springer. - 0957-7572 .- 1573-1804. ; 30:3, s. 553-585
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Tidskriftsartikel (refereegranskat)abstract
- Cornerstone design courses have become a major part of engineering curricula, where students with different personality types and learning styles work together to design, develop, build, and demonstrate the functionality of a prototype within the duration of a term. This study analyzes student and team performance against gender, personality types, and learning styles in a second-year engineering design course. Further, the correlations between several assessment mechanisms are studied, and the effects of three different instructional design approaches on students’ performance are explored. Data have been collected on student performance and psychometrics, including marks, gender, personality type, and learning style from 2001 to 2018. To identify students’ personality types and learning styles, Myers–Briggs Type Indicators (MBTI) and Neil Fleming’s Learning VARK tests were administered. To evaluate students’ performance in the course, a number of assessment mechanisms have been defined. Several statistical methods are used to analyze data, and to determine correlation between datasets. Over nearly two decades of marks, gender, MBTI, and VARK data for 2637 students are presented for an engineering design course. The results demonstrated that there was no significant difference in performance across most assessments based on gender or gender distribution on a team. A better performance was observed from VK bimodal and quadmodal learning styles in most assessment mechanisms. Further, certain MBTI groups, namely, judging types outperformed their peers in engineering design assessments, with interesting interplay between MBTI dimensions for specific assessments and team dynamics. Traditional assessment mechanisms, such as engineering notebook and design proposals, are shown to be good predictors of student success. Lastly, scaffolded design activities and front-loading of lecture content were shown to be beneficial for student learning. There is negligible performance difference between female and male students in the engineering design course. Students whose preferred learning styles align with the assessment themes showed better performance in the course. The outcomes of this paper can be readily applied by instructors for design of assessment mechanisms, course materials, team formation, and instructional design.
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| 15. |
- Hakima, Houman, et al.
(författare)
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A Deorbiter CubeSat for Active Orbital Debris Removal
- 2018
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Ingår i: Advances in Space Research. - : Elsevier. - 0273-1177 .- 1879-1948. ; 61:9, s. 2377-2392
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Tidskriftsartikel (refereegranskat)abstract
- This paper introduces a mission concept for active removal of orbital debris based on the utilization of the CubeSat form factor. The CubeSat is deployed from a carrier spacecraft, known as a mothership, and is equipped with orbital and attitude control actuators to attach to the target debris, stabilize its attitude, and subsequently move the debris to a lower orbit where atmospheric drag is high enough for the bodies to burn up. The mass and orbit altitude of debris objects that are within the realms of the CubeSat’s propulsion capabilities are identified. The attitude control schemes for the detumbling and deorbiting phases of the mission are specified. The objective of the deorbiting maneuver is to decrease the semi-major axis of the debris orbit, at the fastest rate, from its initial value to a final value of about 6,471 km (i.e., 100 km above Earth considering a circular orbit) via a continuous low-thrust orbital transfer. Two case studies are investigated to verify the performance of the deorbiter CubeSat during the detumbling and deorbiting phases of the mission. The baseline target debris used in the study are the decommissioned KOMPSAT-1 satellite and the Pegasus rocket body. The results show that the deorbiting times for the target debris are reduced significantly, from several decades to one or two years.
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