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| 2. |
- Albers, Roland, et al.
(författare)
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Magnetospheric Venus Space Explorers (MVSE) mission : a proposal for understanding the dynamics of induced magnetospheres
- 2024
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Ingår i: Acta Astronautica. - : Elsevier. - 0094-5765 .- 1879-2030. ; 221, s. 194-205
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Tidskriftsartikel (refereegranskat)abstract
- Induced magnetospheres form around planetary bodies with atmospheres through the interaction of the solar wind with their ionosphere. Induced magnetospheres are highly dependent on the solar wind conditions and have only been studied with single spacecraft missions in the past. Without simultaneous measurements of solar wind variations and phenomena in the magnetosphere, establishing a link between both can only be done indirectly, using statistics over a large set of measurements. This gap in knowledge could be addressed by a multi-spacecraft plasma mission, optimized for studying global spatial and temporal variations in the magnetospheric system around Venus, which hosts the most prominent example of an induced magnetosphere in our solar system. The MVSE mission comprises four satellites, of which three are identical scientific spacecraft, carrying the same suite of instruments probing different regions of the induced magnetosphere and the solar wind simultaneously. The fourth spacecraft is the transfer vehicle which acts as a relay satellite for communications at Venus. In this way, changes in the solar wind conditions and extreme solar events can be observed, and their effects can be quantified as they propagate through the Venusian induced magnetosphere. Additionally, energy transfer in the Venusian induced magnetosphere can be investigated. The scientific payload includes instrumentation to measure the magnetic field, electric field, and ion–electron velocity distributions. This study presents the scientific motivation for the mission as well as requirements and the resulting mission design. Concretely, a mission timeline along with a complete spacecraft design, including mass, power, communication, propulsion and thermal budgets are given. This mission was initially conceived at the Alpbach Summer School 2022 and refined during a week-long study at ESA's Concurrent Design Facility in Redu, Belgium.
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| 3. |
- Amini, Kasra, et al.
(författare)
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Lighting and illumination investigation of long-term residence on Mars for the case of a set of designed Martian Habitat Units (MHUs)
- 2022
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Ingår i: Acta Astronautica. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0094-5765 .- 1879-2030. ; 192, s. 210-232
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Tidskriftsartikel (refereegranskat)abstract
- Addressing the subject matter of human missions on Mars, the Martian Habitat Units (MHUs) are presented as a comprehensive solution. MHUs are designed in clusters of 10 units, each capable of serving as long-term habitats for 9 scientific crew members. The life-style requirements of the units are targeted at an imitation of cultural thriving life we all know of, and not a mere survival-type shelter expecting the first people to step foot on Mars. One aspect of many challenging issues to be addressed in such complex settings is the lighting and illuminance condition of the said habitats, which in the context of Mars, and generally deep space missions being far from the sun will certainly lead to an arduous task. To check the validity of the argument and assess the extent to which the natural light level available on the surface of Mars will be sufficient for the daily requirements of the crew and mission in terms of illuminance, the current manuscript presents thorough and detailed simulations and analyses on the availability evaluation of natural lighting in the site location of MHUs, namely Valles Marineris, Melas Chasma. In this paper solar irradiation parameters on Mars are calculated based on the previous research which resulted in global, direct and diffuse irradiance at 12 different Martian solar times. The simulations are distributed over the Martian year and its day-time, and for two extreme orientations of MHUs in their circular surrounding cluster, namely East/West and South/North units. The distribution of illuminance for each case, and trend comparison studies are then accompanied by numerical values and analyses on the percentage to which the natural lighting conditions on Mars have been shown to be sufficient as a fraction of the whole lighting load of the habitats, which is to be compensated using artificial sources. The corresponding values are shown to fall well in the range of 35-45% of the total lighting loads. Also, as the results of the simulations show, due to the consistency of the glazed parts of the designed facade through all exterior surface of the MHU, natural lighting sufficiency percentage does not show a significant difference between two simulated orientations. This fact further approves the circular orientation premise of the MHUs in their cluster.
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| 4. |
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| 5. |
- Anthony, Niklas, et al.
(författare)
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Laboratory experiments with a laser-based attachment mechanism for spacecraft at small bodies
- 2021
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Ingår i: Acta Astronautica. - : Elsevier. - 0094-5765 .- 1879-2030. ; 189, s. 391-397
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of two sets of experiments that investigate laser-based metal-to-rock attachment techniques. Asteroids and comets have low surface gravity which pose a challenge to landers with moving parts. Such parts can generate torques and forces which may tip the lander over or launch it into deep space. Thus, if a lander on a small body is to have moving parts, the spacecraft must be equipped with an anchoring mechanism. To this end, we sought to use a laser to melt and bind a piece of metal mimicking a part of a spacecraft to a rock mimicking the surface of a typical asteroid. In the first set of experiments, extra material was not fed in during the processing. The second set were performed using a standard wire feeder used in laser welding, which added metal to the experiment during processing. During the first experiments, we discovered that a traditional weld, where two melt pools mix and solidify to form a strong bond, was not possible—the melt pools would not mix, and when they did, the resulting weld was extremely brittle. The second set of experiments resulted in a physico-mechanical bond, where a hole was drilled with a laser, and a wire was melted and fed into the hole. These latter experiments were successful in forming bonds as strong as 115 N. Such an attachment mechanism can also be used to maneuver small boulders on asteroid surfaces, to redirect small, monolithic asteroids, or in space-debris removal.
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| 6. |
- Anthony, Niklas, et al.
(författare)
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Laser-induced spallation of minerals common on asteroids
- 2021
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Ingår i: Acta Astronautica. - : Elsevier. - 0094-5765 .- 1879-2030. ; 182, s. 325-331
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Tidskriftsartikel (refereegranskat)abstract
- The ability to deflect dangerous small bodies in the Solar System or redirect profitable ones is a necessary and worthwhile challenge. One well-studied method to accomplish this is laser ablation, where solid surface material sublimates, and the escaping gas creates a momentum exchange. Alternatively, laser-induced spallation and sputtering could be a more efficient means of deflection, yet little research has studied these processes in detail. We used a 15-kW Ytterbium fiber laser on samples of olivine, pyroxene, and serpentine (minerals commonly found on asteroids) to induce spallation. We observed the process with a high-speed camera and illumination laser, and used X-ray micro-tomography to measure the size of the holes produced by the laser to determine material removal efficiency. We found that pyroxene will spallate at power densities between 1.5 and 6.0 kW cm−2, serpentine will also spallate at 13.7 kW cm−2, but olivine does not spallate at 1.5 kW cm−2 and higher power densities melt the sample. Laser-induced spallation of pyroxene and serpentine can be two- to three-times more energy efficient (volume removed per unit of absorbed energy) than laser-induced spattering, and over 40x more efficient than laser ablation.
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| 7. |
- Barabash, Victoria, Dr, et al.
(författare)
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Development of a competence ecosystem for the future space workforce: strategies, practices and recommendations from international master programs in northern Sweden
- 2022
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Ingår i: Acta Astronautica. - : Elsevier. - 0094-5765 .- 1879-2030. ; 197, s. 46-52
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Tidskriftsartikel (refereegranskat)abstract
- Requirements from the global labor market have substantially changed in recent years. Graduate and post-graduate students with excellent subject knowledge, deep understanding of modern working methods, technicaland higher-order thinking, engineering intuition and problem-solving skills are in great demand. They should also have professional skills such as well-developed abilities in communication and teamwork, usually in an international work environment. This review discusses the advantages of multidisciplinary study environment, educational strategies such as student-oriented teaching, project-based learning with its applicability to a“real-world” setting, active learning techniques, development of entrepreneurial skills, lessons learned and best practices from the international Master Program in Spacecraft Design and the Joint Master Program in SpaceScience and Technology – SpaceMaster at Luleå University of Technology in northern Sweden. The importance of complementarity between formal, informal and non-formal learning methods for science and engineering studentshas been specifically highlighted. Connections to the world of work, through active industry involvementin the education in a systematic way, e.g. External Advisory Board, shared services and facilities, joint projectsand supervision of Master and PhD students, is recognised as a key success factor for professional training. A structural combination of modern pedagogical tools, strategic partnership with industry, business entities, academic partners and up-to-date multidisciplinary labs creates the conceptual framework for a CompetenceEcosystem for fostering a new generation of space scientists and engineers.
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| 8. |
- Bazzocchi, Michael C.F., et al.
(författare)
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Comparative analysis of redirection methods for asteroid resource exploitation
- 2016
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Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765 .- 1879-2030. ; 120, s. 1-19
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Tidskriftsartikel (refereegranskat)abstract
- An in-depth analysis and systematic comparison of asteroid redirection methods is performed within a resource exploitation framework using different assessment mechanisms. Through this framework, mission objectives and constraints are specified for the redirection of an asteroid from a near-Earth orbit to a stable orbit in the Earth-Moon system. The paper provides a detailed investigation of five redirection methods, i.e., ion beam, tugboat, gravity tractor, laser sublimation, and mass ejector, with respect to their capabilities for a redirection mission. A set of mission level criteria are utilized to assess the performance of each redirection method, and the means of assigning attributes to each criterion is discussed in detail. In addition, the uncertainty in physical characteristics of the asteroid population is quantified through the use of Monte Carlo analysis. The Monte Carlo simulation provides insight into the performance robustness of the redirection methods with respect to the targeted asteroid range. Lastly, the attributes for each redirection method are aggregated using three different multicriteria assessment approaches, i.e., the analytical hierarchy process, a utility-based approach, and a fuzzy aggregation mechanism. The results of each assessment approach as well as recommendations for further studies are discussed in detail.
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| 9. |
- Bazzocchi, Michael C.F., et al.
(författare)
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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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| 10. |
- Bodin, Per, et al.
(författare)
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System test results from the GNC experiments on the PRISMA in-orbit test bed
- 2011
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Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765 .- 1879-2030. ; 68:7, s. 862-872
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Tidskriftsartikel (refereegranskat)abstract
- The PRISMA in-orbit test bed will demonstrate guidance, navigation, and control strategies for spacecraft formation flying and rendezvous. The project is funded by the Swedish National Space Board and the prime contractor is the Swedish Space Corporation. The project is further supported by the German Aerospace Center, the Technical University of Denmark, and the French Space Agency. PRISMA was launched on June 15, 2010 and after three weeks of operations, all on-board systems and units have passed an initial commissioning phase. Separation of the two PRISMA satellites from each other is expected by mid-August 2010. PRISMA consists of two spacecraft: MAIN and TARGET. The MAIN spacecraft has full orbit control capability while TARGET is attitude controlled only. The Swedish Space Corporation is responsible for three groups of guidance, navigation, and control experiments. These experiments include GPS- and vision-based formation flying during which the spacecraft will fly in passive as well as forced motion. The three experiments are: autonomous formation flying, proximity operations with final approach/recede maneuvers, and autonomous rendezvous. This paper presents system test results from two of these experiments as obtained with the flight-ready system. The system tests consist of a series of simulations performed on the flight model spacecraft with a large amount of hardware in the loop.
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