| 1. |
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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. |
- Bae, Sangjun, 1986, et al.
(författare)
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Multi-objective suborbit/orbit trajectory optimisation for spaceplanes
- 2020
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Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765. ; 170, s. 431-442
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a suborbit to orbit mission profile is analysed for spaceplanes. The proposed mission profile for spaceplanes is currently being considered for multiple earth observation missions and is considered as an extension of the skip re-entry problem which is a highly coupled and nonlinear problem. To solve the problem, we utilise both the Fuzzy Satisfactory Goal Programming (FSGP) method and the Radau Pseudospectral Method (RPM) as the problem includes more than two objective functions conflicting with each other, and needs to be optimised with pre-emptive priorities. A realistic spaceplane model is used with equality and inequality constraints, to demonstrate the feasibility of suborbit-orbit-suborbit manoeuvres through numerical simulations. The simulation results generated by the proposed methodology show that significant propellant savings can be made using multi-objective trajectory optimisation for spaceplanes for future theatre observation missions.
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| 8. |
- Bannova, Olga, 1964, et al.
(författare)
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Designing From Minimum to Optimum Functionality.
- 2011
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Ingår i: Acta Astronautica. - 0094-5765. ; 68:7-8, s. 760-769
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses a multifaceted strategy to link NASA Minimal Functionality Habitable Element (MFHE) requirements to a compatible growth plan; leading forward to evolutionary, deployable habitats including outpost development stages. The discussion begins by reviewing fundamental geometric features inherent in small scale, vertical and horizontal, pressurized module configuration options to characterize applicability to meet stringent MFHE constraints.A proposed scenario to incorporate a vertical core MFHE concept into an expanded architecture to provide continuity of structural form and geometric logic bridging between “minimum” and “optimum”.The paper describes how habitation and logistics accommodations could be pre-integrated into a common Hab/Log Module that serves both habitation and logistics functions. This is offered as a means to reduce unnecessary redundant development costs and to avoid EVA-intensive on-site adaptation and retrofitting requirements for augmented crew capacity. An evolutionary version of the hard shell Hab/Log design would have an expandable middle section to afford larger living and working accommodations.In conclusion, the paper illustrates that a number of cargo missions referenced for NASA’s 4.0.0 Lunar Campaign Scenario could be eliminated altogether to expedite progress and reduce budgets. The plan concludes with a vertical growth geometry that provides versatile and efficient site development opportunities using a combination of hard Hab/Log modules and a hybrid expandable “CLAM” element.
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| 9. |
- Bannova, Olga, 1964, et al.
(författare)
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Space Architecture Education as Part of Aerospace Engineering Curriculum
- 2011
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Ingår i: Acta Astronautica. - 0094-5765. ; 69:11-12, s. 1143-1147
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Tidskriftsartikel (refereegranskat)abstract
- Education is particularly important for new fields. In the case of Space Architecture, there are two core needs: 1.educating the aerospace community about the architect’s process and role within the enterprise; 2.educating space architects and associated specialists about constraints, conditions, and priorities unique to human space systems.These needs can be addressed, respectively, by two key educational tools for the 21st century: 1.introducing the Space Architecture discipline into space system engineering curricula;2.developing Space Architecture as a distinct, complete training curriculum. New generations of professionals with a Space Architecture background, by offering their inherently integrative design approach to all types of space structures and facilities, can help shift professional focus from just engineering-driven transportation systems and “sortie” missions to permanent offworld human presence. Although architectural and engineering approaches share some similarities in solving problems, they also have significant differences. Architectural training teaches young professionals to operate at all scales from the “overall picture” down to the smallest details; to provide directive intention – not just analysis – to design opportunities, to address the relationship between human behavior and the built environment, and to interact with many diverse fields and disciplines throughout the project lifecycle.
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| 10. |
- 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
-
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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| 11. |
- 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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| 12. |
- 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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| 13. |
- 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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| 14. |
- Bruhn, Fredrik, et al.
(författare)
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A Preliminary Design for a Spherical Inflatable Microrover for Planetary Exploration
- 2008
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Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765 .- 1879-2030. ; 63:5-6, s. 618-631
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Tidskriftsartikel (refereegranskat)abstract
- The Spherical Mobile Investigator for Planetary Surface (SMIPS) concept aims at making use of the latest developments within extreme miniaturization of space systems. The introduction of Microelectromechanical Systems (MEMSs) and higher level Multifunctional Microsystems (MMSs) design solutions gives the robot high performance per weight unit. The untraditional spherical shape makes it easily maneuverable and thus provides a platform for scientific investigations of interplanetary bodies. Preliminary investigations of the SMIPS concept show several advantages over conventional robots and rovers in maneuverability, coverage, size, and mass. A locomotion proof-of-concept has been Studied together with a new distributed on-board data system configuration. This paper discusses theoretical robot analysis, an overall concept, possible science, enabling technologies, and how to perform scientific investigations. A preliminary design of an inflatable multifunctional shell is proposed.
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| 15. |
- Cai, Zun, et al.
(författare)
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Effect of combustor geometry and fuel injection scheme on the combustion process in a supersonic flow
- 2016
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Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765. ; 129, s. 44-51
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Tidskriftsartikel (refereegranskat)abstract
- The combustion process in a hydrogen fueled scramjet combustor with a rearwall-expansion cavity was investigated numerically under inflow conditions of Ma=2.52 with stagnation pressure P0=1.6 Mpa and stagnation temperature T0=1486 K. The numerical solver was first evaluated for supersonic reactive flows in a similar combustor configuration where experimental data is available. Wall-pressure distribution was compared with the experiments, and grid independency analysis and chemical mechanism comparison were conducted. The numerical results showed fairly good agreements with the available experimental data under supersonic combustion conditions. Then the numerical solver was used to study the effects of combustor geometry, fuel injection scheme and injection equivalence ratio on the combustion process. It was found that under the same fuel injection condition, the combustor configuration with a rearwall-expansion cavity is in favor of the supersonic combustion mode and present better ability of thermal choking prevention than the other combustor configurations. For the rearwall-expansion cavity combustor, the supersonic flow field was found to be sensitive to the injector position and injection scheme, but not highly sensitive to the injection pressure. Besides, rearwall-expansion cavity with the combined fuel injection scheme (with an injection upstream the cavity and a direct injection on the rear wall) is an optimized injection scheme during the flame stabilization process.
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| 16. |
- Cai, Zun, et al.
(författare)
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Large Eddy Simulation of the fuel transport and mixing process in a scramjet combustor with rearwall-expansion cavity
- 2016
-
Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765. ; 126, s. 375-381
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Tidskriftsartikel (refereegranskat)abstract
- Large Eddy Simulation (LES) was employed to investigate the fuel/oxidizer mixing process in an ethylene fueled scramjet combustor with a rearwall-expansion cavity. The numerical solver was first validated for an experimental flow, the DLR strut-based scramjet combustor case. Shock wave structures and wall-pressure distribution from the numerical simulations were compared with experimental data and the numerical results were shown in good agreement with the available experimental data. Effects of the injection location on the flow and mixing process were then studied. It was found that with a long injection distance upstream the cavity, the fuel is transported much further into the main flow and a smaller subsonic zone is formed inside the cavity. Conversely, with a short injection distance, the fuel is entrained more into the cavity and a larger subsonic zone is formed inside the cavity, which is favorable for ignition in the cavity. For the rearwall-expansion cavity, it is suggested that the optimized ignition location with a long upstream injection distance should be in the bottom wall in the middle part of the cavity, while the optimized ignition location with a short upstream injection distance should be in the bottom wall in the front side of the cavity. By employing a cavity direct injection on the rear wall, the fuel mass fraction inside the cavity and the local turbulent intensity will both be increased due to this fueling, and it will also enhance the mixing process which will also lead to increased mixing efficiency. For the rearwall-expansion cavity, the combined injection scheme is expected to be an optimized injection scheme.
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| 17. |
- Cakir, Bora O., et al.
(författare)
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Reduced order design and investigation of intakes for high speed propulsion systems
- 2022
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Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765. ; 199, s. 259-276
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Tidskriftsartikel (refereegranskat)abstract
- Ramjet propulsion is commonly preferred to power supersonic and hypersonic vehicles for cruising faster than Mach 3. This is an elegant solution owing to the lean architecture which does not embody any rotating parts. Although the geometry of the engine is simple as compared to turbine based configurations, the flow physics through the engine duct is quite complex and the flow speeds modulate between the supersonic and subsonic regimes multiple times. The design and performance analysis of ramjet engines are vital to ensure that propulsion system can satisfy the flight trajectory requirements. Therefore, this study introduces a reduced order holistic approach for design and assessment of the flow development in high-speed propulsion systems composed of generic elements of ramjet/scramjet engine configurations. Accordingly, the intakes designed based on axisymmetric flow templates are used to provide the necessary freestream flow modulation prior to the isolator through which a normal shock assumption is applied. The resultant flow properties are utilized for the combustion module where the flow expansion within the combustor and nozzle components are computed based on 1D steady inviscid flow equations coupled with detailed chemistry approach and JANAF tables. The module was validated and verified with the experimental and numerical data obtained for a dual-mode ramjet/scramjet combustor. Consequently, the parameters such as thrust, fuel consumption and specific impulse are calculated to quantify the engine performance for each design. Finally, the employment of the low fidelity model is demonstrated over a family of ramjet flow paths where the design space is confined based on the requirements of a high-supersonic cruise vehicle.
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| 18. |
- Conte, Davide, et al.
(författare)
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Advanced concept for a crewed mission to the martian moons
- 2017
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Ingår i: Acta Astronautica. - : Elsevier. - 0094-5765 .- 1879-2030. ; 139, s. 545-563
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the conceptual design of the IMaGInE (Innovative Mars Global International Exploration) Mission. The mission's objectives are to deliver a crew of four astronauts to the surface of Deimos and perform a robotic exploration mission to Phobos. Over the course of the 343 day mission during the years 2031 and 2032, the crew will perform surface excursions, technology demonstrations, In Situ Resource Utilization (ISRU) of the Martian moons, as well as site reconnaissance for future human exploration of Mars. This mission design makes use of an innovative hybrid propulsion concept (chemical and electric) to deliver a relatively low-mass reusable crewed spacecraft (approximately 100 mt) to cis-martian space. The crew makes use of torpor which minimizes launch payload mass. Green technologies are proposed as a stepping stone towards minimum environmental impact space access. The usage of beamed energy to power a grid of decentralized science stations is introduced, allowing for large scale characterization of the Martian environment. The low-thrust outbound and inbound trajectories are computed through the use of a direct method and a multiple shooting algorithm that considers various thrust and coast sequences to arrive at the final body with zero relative velocity. It is shown that the entire mission is rooted within the current NASA technology roadmap, ongoing scientific investments and feasible with an extrapolated NASA Budget. The presented mission won the 2016 Revolutionary Aerospace Systems Concepts - Academic Linkage (RASC-AL) competition.
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| 19. |
- Delpech, M, et al.
(författare)
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Flight demonstration of formation flying capabilities for future missions (NEAT Pathfinder)
- 2014
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Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765 .- 1879-2030. ; 105:1, s. 82-94
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Tidskriftsartikel (refereegranskat)abstract
- PRISMA is a demonstration mission for formation-flying and on-orbit-servicing critical technologies that involves two spacecraft launched in low Earth orbit in June 2010 and still in operation. Funded by the Swedish National Space Board, PRISMA mission has been developed by OHB-Sweden (formerly Swedish Space Corporation) with important contributions from the German Aerospace Centre (DLR/GSOC), the French Space Agency (CNES), and the Technical University of Denmark (DTU). The paper focuses on the last CNES experiment achieved in September 2012 that was devoted to the preparation of future astrometry missions illustrated by the NEAT and mu-NEAT mission concepts. The experiment consisted of performing the type of formation maneuvers required to point the two-satellite axis to a celestial target and maintain it fixed during the observation period. Achieving inertial pointing for a LEO formation represented a new challenge given the numerous constraints from propellant usage to star tracker blinding. The paper presents the experiment objectives in relation with the NEAT/mu-NEAT mission concept, describes its main design features along with the guidance and control algorithms evolutions and discusses the results in terms of performances achieved during the two rehearsals.
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| 20. |
- Felicetti, Leonard, et al.
(författare)
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A multi-spacecraft formation approach to space debris surveillance
- 2016
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Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765 .- 1879-2030. ; 127, s. 491-504
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a new mission concept devoted to the identification and tracking of space debris through observations made by multiple spacecraft. Specifically, a formation of spacecraft has been designed taking into account the characteristics and requirements of the utilized optical sensors as well as the constraints imposed by sun illumination and visibility conditions. The debris observations are then shared among the team of spacecraft, and processed onboard of a “hosting leader” to estimate the debris motion by means of Kalman filtering techniques. The primary contribution of this paper resides on the application of a distributed coordination architecture, which provides an autonomous and robust ability to dynamically form spacecraft teams once the target has been detected, and to dynamically build a processing network for the orbit determination of space debris. The team performance, in terms of accuracy, readiness and number of the detected objects, is discussed through numerical simulations.
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| 21. |
- Felicetti, Leonard, et al.
(författare)
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Analytical and numerical investigations on spacecraft formation control by using electrostatic forces
- 2016
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Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765 .- 1879-2030. ; 123, s. 455-469
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Tidskriftsartikel (refereegranskat)abstract
- The paper investigates some analytical and numerical aspects of the formation control exploited by means of inter-spacecraft electrostatic actions. The analysis is based on the evaluation and check of the stability issues by using a sequence of purposely defined Lyapunov functions. The same Lyapunov approach can also define a specific under-actuate control strategy for controlling selected “virtual links” of the formation. Two different selection criteria for these links are then discussed, showing the implications on the control chain. An optimal charge distribution strategy, which assigns univocally the charges to all the spacecraft starting from the charge products computed by the control, is also presented and discussed. Numerical simulations prove the suitability of the proposed approach to a formation of 4 satellites.
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| 22. |
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| 23. |
- Filgas, Robert, et al.
(författare)
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Miniature semiconductor neutron spectrometer HardPix for surface mapping of lunar water
- 2022
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Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765 .- 1879-2030. ; 200, s. 620-625
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Tidskriftsartikel (refereegranskat)abstract
- A current renaissance of lunar exploration enables to search for lunar water deposits directly on the surface of the Moon with robotic rovers. We present a novel miniature semiconductor neutron spectrometer capable of mapping the water deposits using non-invasive detection of neutrons created underground by cosmic rays and thermalized by hydrogen. This prospecting package consists of a radiation detector to monitor the cosmic rays background, a thermal/epithermal neutron detector to measure flux of neutrons moderated by water, and a gamma spectrometer suitable for monitoring local changes of major elemental components of the lunar regolith. Using miniature semiconductor detectors allows to deploy them even on small commercial rovers where resources are extremely limited. The prospecting package is being developed for ispace lunar rover and studied for ESA EL3 rover. It is based on Timepix pixel sensors, with space heritage onboard NASA, ESA and JAXA vessels.
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| 24. |
- Fuglesang, Christer, 1957-, et al.
(författare)
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Realistic sunshade system at L-1 for global temperature control
- 2021
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Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765 .- 1879-2030. ; 186, s. 269-279
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Tidskriftsartikel (refereegranskat)abstract
- So far, space-based geoengineering has rarely been studied from a practical point of view, considered unrealistic as a near-future alternative to fight climate change. This paper evaluates the feasibility of implementing a space sunshade in the vicinity of the first Lagrange point of the Sun-Earth system by the middle of the century. The analysis considers the necessary technological development, the possible trajectories for the shades, and an approximation of the size and cost of the system. It is strongly dependent on the possible optical properties of future solar sails, so an optimal and a more conservative alternative have been studied. With the latter, the shade will be formed by 1.5 x 10(9) sailcraft with a sail area of 2500 m(2) and a total mass of 8.3 x 10(10) kg. In the optimal case, the total mass is 3.4 x 10(10) kg. Each one of these sails will be launched to a 2000 km orbit, from where they will travel for about 600 days to the equilibrium point using solar radiation pressure. The total cost of the mission is estimated to be five to ten trillion dollars, based on a launch cost of US$50/kg. There are two main technological challenges for this to become a reality: the low TRL of the solar sails proposed and the necessary development in the launch vehicle industry given the dimensions of the mission.
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| 25. |
- Gassot, Oriane, et al.
(författare)
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Calathus : A sample-return mission to Ceres
- 2021
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Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765 .- 1879-2030. ; 181, s. 112-129
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Tidskriftsartikel (refereegranskat)abstract
- Ceres, as revealed by NASA's Dawn spacecraft, is an ancient, crater-saturated body dominated by low-albedo clays. Yet, localised sites display a bright, carbonate mineralogy that may be as young as 2 Myr. The largest of these bright regions (faculae) are found in the 92 km Occator Crater, and would have formed by the eruption of alkaline brines from a subsurface reservoir of fluids. The internal structure and surface chemistry suggest that Ceres is an extant host for a number of the known prerequisites for terrestrial biota, and as such, represents an accessible insight into a potentially habitable "ocean world". In this paper, the case and the means for a return mission to Ceres are outlined, presenting the Calathus mission to return to Earth a sample of the Occator Crater faculae for high-precision laboratory analyses. Calathus consists of an orbiter and a lander with an ascent module: the orbiter is equipped with a high-resolution camera, a thermal imager, and a radar; the lander contains a sampling arm, a camera, and an on-board gas chromatograph mass spectrometer; and the ascent module contains vessels for four cerean samples, collectively amounting to a maximum 40 g. Upon return to Earth, the samples would be characterised via high-precision analyses to understand the salt and organic composition of the Occator faculae, and from there to assess both the habitability and the evolution of a relict ocean world from the dawn of the Solar System.
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