Pub Date : 2025-01-10DOI: 10.1016/j.actaastro.2025.01.016
Dengliang Liao, Xingyi Pan, Zhengtao Wei, Ti Chen
A scheme for the on-orbit autonomous assembly and reconfiguration of the ultra-large space structure inspired by Vicsek fractal is developed in this paper. The grouped and staged strategy is applied to the structure consisting of 125 rigid modular satellites and two flexible modular ones. Each assembly action is divided into pre-assembly and docking steps, while the reconfiguration involves dispersal, unit reconfiguration and reassembly phases. The dynamics model of satellites is established based on the Clohessy-Wiltshire equations and rotation matrix. Relative position and attitude controllers are designed for the mission, where a collision avoidance controller is combined in the pre-assembly step particularly. The Lyapunov stability is analyzed and the proposed strategy is demonstrated by both numerical simulations and an experiment on air-bearing testbed.
{"title":"Assembly and reconfiguration of space structure using heterogeneous satellite swarms","authors":"Dengliang Liao, Xingyi Pan, Zhengtao Wei, Ti Chen","doi":"10.1016/j.actaastro.2025.01.016","DOIUrl":"10.1016/j.actaastro.2025.01.016","url":null,"abstract":"<div><div>A scheme for the on-orbit autonomous assembly and reconfiguration of the ultra-large space structure inspired by Vicsek fractal is developed in this paper. The grouped and staged strategy is applied to the structure consisting of 125 rigid modular satellites and two flexible modular ones. Each assembly action is divided into pre-assembly and docking steps, while the reconfiguration involves dispersal, unit reconfiguration and reassembly phases. The dynamics model of satellites is established based on the Clohessy-Wiltshire equations and rotation matrix. Relative position and attitude controllers are designed for the mission, where a collision avoidance controller is combined in the pre-assembly step particularly. The Lyapunov stability is analyzed and the proposed strategy is demonstrated by both numerical simulations and an experiment on air-bearing testbed.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 166-180"},"PeriodicalIF":3.1,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143173527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-10DOI: 10.1016/j.actaastro.2025.01.010
Justine Tansley , Nicolas Miché , Marco Bernagozzi , Simon Cahill , Anastasios Georgoulas , Matteo Santin , Rachel Forss
The present observational study simultaneously measured four key factors (arterial oxygenation, superficial tissue oxygenation, peripheral skin temperature, toe systolic pressure) to determine the impact on lower limb perfusion in altered gravity conditions. 24 healthy test subjects (16 male, 8 female) took part onboard a series of parabolic flights. When comparing lower limb perfusion values to 1G (control/Earth's gravity) the study found: 1) no significant difference between arterial oxygenation values in hyper or microgravity was detected when using a pulse oximeter; 2) a significant difference in superficial tissue oxygenation in hyper and microgravity was detected by white light spectroscopy; 3) a significant difference in skin temperature of the foot was detected by thermography in hyper and microgravity; 4) an insufficient sample could be obtained for toe systolic pressure. Reduction in superficial tissue oxygenation and peripheral skin temperature in microgravity compared to 1G, potentially suggests a reduction in blood flow. White light spectroscopy and thermography devices demonstrated they functioned as usual in altered gravity conditions potentially offering a quick, reliable method of assessing the acute effects of hyper and microgravity on lower limb perfusion. These methods may be useful to predict healing potential when injuries occur and highlight early warning signs of tissue damage due to poor perfusion. However, additional work to further establish the impact on oxygen transport in the superficial tissues in both acute and sustained microgravity would be beneficial.
{"title":"Gravity effects on lower limb perfusion observed during a series of parabolic flights","authors":"Justine Tansley , Nicolas Miché , Marco Bernagozzi , Simon Cahill , Anastasios Georgoulas , Matteo Santin , Rachel Forss","doi":"10.1016/j.actaastro.2025.01.010","DOIUrl":"10.1016/j.actaastro.2025.01.010","url":null,"abstract":"<div><div>The present observational study simultaneously measured four key factors (arterial oxygenation, superficial tissue oxygenation, peripheral skin temperature, toe systolic pressure) to determine the impact on lower limb perfusion in altered gravity conditions. 24 healthy test subjects (16 male, 8 female) took part onboard a series of parabolic flights. When comparing lower limb perfusion values to 1G (control/Earth's gravity) the study found: 1) no significant difference between arterial oxygenation values in hyper or microgravity was detected when using a pulse oximeter; 2) a significant difference in superficial tissue oxygenation in hyper and microgravity was detected by white light spectroscopy; 3) a significant difference in skin temperature of the foot was detected by thermography in hyper and microgravity; 4) an insufficient sample could be obtained for toe systolic pressure. Reduction in superficial tissue oxygenation and peripheral skin temperature in microgravity compared to 1G, potentially suggests a reduction in blood flow. White light spectroscopy and thermography devices demonstrated they functioned as usual in altered gravity conditions potentially offering a quick, reliable method of assessing the acute effects of hyper and microgravity on lower limb perfusion. These methods may be useful to predict healing potential when injuries occur and highlight early warning signs of tissue damage due to poor perfusion. However, additional work to further establish the impact on oxygen transport in the superficial tissues in both acute and sustained microgravity would be beneficial.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 286-296"},"PeriodicalIF":3.1,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143174320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-10DOI: 10.1016/j.actaastro.2025.01.027
Lixiang Li , Christian Ingabire , Daolun Liang , Ji Li , Yunan Zhou , Yue Jiang , Dekui Shen
Compared to casting process, the advantages of additive manufacturing (AM) technology, such as the elimination of mold requirements, and enhanced adaptability to complex geometries, render it highly promising for applications involving the configuration of energy release gradients, and regulation of combustion processes. To explore the disparities in mechanical performance and combustion characteristics of printed and casted propellants, a computed tomographic scanner and a universal testing machine were employed to characterize the pore structure and tensile strength. A visual online detection experimental system was established to investigate the combustion characteristics under 1–9 atm, with the condensed combustion products (CCPs) being diagnosed. Results indicate that the printed sample exhibits a lower porosity, a higher density, and a greater tensile strength. Under identical pressure, the radial flame diffusion of printed strand is weaker, whereas the axial diffusion is stronger. The burning rates and combustion temperatures of the printed strand consistently exceed those of the casted strands, with this disparity progressively widening during pressure increasing. Moreover, the printed strand exhibits enhanced combustion stability. The diagnostic results indicate that the CCPs can be categorized into smoke oxide particles (SOPs), spherical agglomerates (SAGs) and irregular agglomerates (IAGs), and the particle size of the printed strand is smaller than that of the casted strand under high pressures. The printed strand exhibits characteristic of complete combustion at lower pressures, as evidenced by the obvious high XRD peak of Al2O3 and the higher combustion efficiency. The AM process reduces the porosity of propellant, thereby intensifying the consumption rate of reactants, and increasing the combustion intensity. This study contributes to a deeper understanding of the application of AM on the solid propellants.
{"title":"Comparative study on mechanical properties and combustion characteristics of additive manufacturing/casting composite solid propellants","authors":"Lixiang Li , Christian Ingabire , Daolun Liang , Ji Li , Yunan Zhou , Yue Jiang , Dekui Shen","doi":"10.1016/j.actaastro.2025.01.027","DOIUrl":"10.1016/j.actaastro.2025.01.027","url":null,"abstract":"<div><div>Compared to casting process, the advantages of additive manufacturing (AM) technology, such as the elimination of mold requirements, and enhanced adaptability to complex geometries, render it highly promising for applications involving the configuration of energy release gradients, and regulation of combustion processes. To explore the disparities in mechanical performance and combustion characteristics of printed and casted propellants, a computed tomographic scanner and a universal testing machine were employed to characterize the pore structure and tensile strength. A visual online detection experimental system was established to investigate the combustion characteristics under 1–9 atm, with the condensed combustion products (CCPs) being diagnosed. Results indicate that the printed sample exhibits a lower porosity, a higher density, and a greater tensile strength. Under identical pressure, the radial flame diffusion of printed strand is weaker, whereas the axial diffusion is stronger. The burning rates and combustion temperatures of the printed strand consistently exceed those of the casted strands, with this disparity progressively widening during pressure increasing. Moreover, the printed strand exhibits enhanced combustion stability. The diagnostic results indicate that the CCPs can be categorized into smoke oxide particles (SOPs), spherical agglomerates (SAGs) and irregular agglomerates (IAGs), and the particle size of the printed strand is smaller than that of the casted strand under high pressures. The printed strand exhibits characteristic of complete combustion at lower pressures, as evidenced by the obvious high XRD peak of Al<sub>2</sub>O<sub>3</sub> and the higher combustion efficiency. The AM process reduces the porosity of propellant, thereby intensifying the consumption rate of reactants, and increasing the combustion intensity. This study contributes to a deeper understanding of the application of AM on the solid propellants.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 43-54"},"PeriodicalIF":3.1,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142967833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-09DOI: 10.1016/j.actaastro.2025.01.026
Juan Miguel Sánchez-Lozano , Eloy Peña-Asensio , Valentin T. Bickel , David A. Kring
Properly designed astronaut traverses are decisive for the science return and safety of crewed lunar missions to the Moon. Their development and planning are challenged by numerous parameters involved and the difficulty of determining their relative importance. Investigating the potential of Multi-Criteria Decision-Making (MCDM) techniques for lunar exploration within the context of Artemis III, this paper demonstrates the effective application of the well-established Analytic Hierarchy Process (AHP) and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). AHP is utilized to derive weights for evaluating criteria, informed by inputs from scientists and engineers, emphasizing the geological interest and temperature of Permanently Shadowed Regions (PSR), followed by the slope profile of the traverse, although weighting is conditioned by expert background. TOPSIS is then applied to objectively rank astronaut traverses to PSRs at sites 001 and 004, situated on the ‘Connecting Ridge’ region. This analysis not only identifies a particular traverse from site 001 that is significantly superior to others but also conducts a sensitivity analysis to assess the impact of challenging-to-quantify criteria such as geological interest. These findings underscore the considerable potential of MCDM techniques to enhance decision-making in lunar missions, thereby promising to improve the efficacy, science return, and safety of future Artemis missions through a systematic approach to complex trade-off decision landscapes.
{"title":"Prioritizing astronaut traverses on the Moon: A multi-criteria decision-making approach","authors":"Juan Miguel Sánchez-Lozano , Eloy Peña-Asensio , Valentin T. Bickel , David A. Kring","doi":"10.1016/j.actaastro.2025.01.026","DOIUrl":"10.1016/j.actaastro.2025.01.026","url":null,"abstract":"<div><div>Properly designed astronaut traverses are decisive for the science return and safety of crewed lunar missions to the Moon. Their development and planning are challenged by numerous parameters involved and the difficulty of determining their relative importance. Investigating the potential of Multi-Criteria Decision-Making (MCDM) techniques for lunar exploration within the context of Artemis III, this paper demonstrates the effective application of the well-established Analytic Hierarchy Process (AHP) and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). AHP is utilized to derive weights for evaluating criteria, informed by inputs from scientists and engineers, emphasizing the geological interest and temperature of Permanently Shadowed Regions (PSR), followed by the slope profile of the traverse, although weighting is conditioned by expert background. TOPSIS is then applied to objectively rank astronaut traverses to PSRs at sites 001 and 004, situated on the ‘Connecting Ridge’ region. This analysis not only identifies a particular traverse from site 001 that is significantly superior to others but also conducts a sensitivity analysis to assess the impact of challenging-to-quantify criteria such as geological interest. These findings underscore the considerable potential of MCDM techniques to enhance decision-making in lunar missions, thereby promising to improve the efficacy, science return, and safety of future Artemis missions through a systematic approach to complex trade-off decision landscapes.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 77-89"},"PeriodicalIF":3.1,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142975196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper proposes a method of capturing small celestial bodies (SCB) by multi-tethered spacecraft formation (MTSF), and the system design and experimental verification are carried out. This method can be used in SCB exploration deep sampling to provide penetration force between the drilling equipment and the star soil. Firstly, the composition and operation flow of the encirclement capture system is described, and the encirclement load unit is designed. The dual quaternion describes the rigid body position and attitude coupling motion, and the Arbitrary Lagrange–Euler and the Absolute Nodal Coordinate Formulation (ALE-ANCF) method describes the variable length tether motion. The dynamic model of the variable length MTSF system is established. Finally, a hybrid formation test platform of air-floating node (AFN) and unmanned air vehicle (UAV) is constructed to simulate the capture process of a three-node spacecraft on the scaled model of a SCB. The results show that the AFN and the UAV cooperatively carry the tether retracting and releasing device to form the encirclement configuration and converge to the desired position and attitude. Finally, the tether configuration realizes the slinging of the SCB scale model, which verifies the feasibility of the encirclement method.
{"title":"Design and experimental verification of multi-tethered spacecraft formation encircled to capture small celestial body system","authors":"Yu Yang, Yixin Huang, Hao Tian, Yuchen Zhu, Changzheng Qian, Yang Zhao","doi":"10.1016/j.actaastro.2025.01.015","DOIUrl":"10.1016/j.actaastro.2025.01.015","url":null,"abstract":"<div><div>This paper proposes a method of capturing small celestial bodies (SCB) by multi-tethered spacecraft formation (MTSF), and the system design and experimental verification are carried out. This method can be used in SCB exploration deep sampling to provide penetration force between the drilling equipment and the star soil. Firstly, the composition and operation flow of the encirclement capture system is described, and the encirclement load unit is designed. The dual quaternion describes the rigid body position and attitude coupling motion, and the Arbitrary Lagrange–Euler and the Absolute Nodal Coordinate Formulation (ALE-ANCF) method describes the variable length tether motion. The dynamic model of the variable length MTSF system is established. Finally, a hybrid formation test platform of air-floating node (AFN) and unmanned air vehicle (UAV) is constructed to simulate the capture process of a three-node spacecraft on the scaled model of a SCB. The results show that the AFN and the UAV cooperatively carry the tether retracting and releasing device to form the encirclement configuration and converge to the desired position and attitude. Finally, the tether configuration realizes the slinging of the SCB scale model, which verifies the feasibility of the encirclement method.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 65-76"},"PeriodicalIF":3.1,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142975149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-09DOI: 10.1016/j.actaastro.2025.01.018
J.W. Elmer, J.S. Bellino
Future construction of large-scale space structures will need to exploit natural space resources for raw materials such as iron from asteroids, which is expected to be a key element due to its availability in near-Earth objects. Although the relative availability of iron-nickel asteroids makes them attractive candidates for space manufacturing, they contain defects and inhomogeneous concentrations of elements such as carbon, phosphorous, and sulfur, along with brittle intermetallic phases, cracks, and voids, that limits their usefulness in their native state. Refinement of the meteoritic metal microstructure and chemistry will be required to render them useful as structural elements that can be fabricated by casting, thermomechanical processing, or welding. This study investigates the vacuum induction melting and casting of a Canyon Diablo Group 1AB-MG coarse octahedrite meteorite demonstrating, as a first step, that cast material can be produced with a refined and more homogeneous microstructure. However, additional metallurgical refinement is still needed to reduce the phosphorous and sulphur content to produce high quality meteoritic steels or alloys for space construction.
{"title":"Induction melting, casting, and weldability of a group IAB iron meteorite","authors":"J.W. Elmer, J.S. Bellino","doi":"10.1016/j.actaastro.2025.01.018","DOIUrl":"10.1016/j.actaastro.2025.01.018","url":null,"abstract":"<div><div>Future construction of large-scale space structures will need to exploit natural space resources for raw materials such as iron from asteroids, which is expected to be a key element due to its availability in near-Earth objects. Although the relative availability of iron-nickel asteroids makes them attractive candidates for space manufacturing, they contain defects and inhomogeneous concentrations of elements such as carbon, phosphorous, and sulfur, along with brittle intermetallic phases, cracks, and voids, that limits their usefulness in their native state. Refinement of the meteoritic metal microstructure and chemistry will be required to render them useful as structural elements that can be fabricated by casting, thermomechanical processing, or welding. This study investigates the vacuum induction melting and casting of a Canyon Diablo Group 1AB-MG coarse octahedrite meteorite demonstrating, as a first step, that cast material can be produced with a refined and more homogeneous microstructure. However, additional metallurgical refinement is still needed to reduce the phosphorous and sulphur content to produce high quality meteoritic steels or alloys for space construction.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 578-590"},"PeriodicalIF":3.1,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143173864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-09DOI: 10.1016/j.actaastro.2025.01.023
Xiucong Sun , Yuan Wang , Jianli Su , Jian Li , Ming Xu , Shengzhou Bai
This study proposes a rapid algorithm to achieve relative orbit transfer based on constant-vector thrust acceleration control, where the magnitude and direction of the thrust acceleration are constant in the tangential–normal–out-of-plane (TNH) frame. Based on the presented linearized thrust-control matrix, which is used to construct the first-order relationships between the relative position, velocity, and the constant-vector thrust acceleration, two analytical approximate solutions are presented for two types of relative orbit transfer problems: the one-vector thrust acceleration solution to the relative orbit transfer problem, which only requires the final relative position, and the double-vector thrust acceleration solution to the relative orbit transfer problem, which requires the final relative position and velocity. Furthermore, for the cases where the magnitude constraint of the thrust provided by the engine is required, fast-iterative algorithms are proposed to obtain the one-vector acceleration solution and the double-vector acceleration solution that satisfy the magnitude constraint strictly. The simulation results showed that the proposed methods are rapid, accurate, and easy to implement, demonstrating their wide application potential for engineering practice.
{"title":"Relative orbit transfer using constant-vector thrust acceleration","authors":"Xiucong Sun , Yuan Wang , Jianli Su , Jian Li , Ming Xu , Shengzhou Bai","doi":"10.1016/j.actaastro.2025.01.023","DOIUrl":"10.1016/j.actaastro.2025.01.023","url":null,"abstract":"<div><div>This study proposes a rapid algorithm to achieve relative orbit transfer based on constant-vector thrust acceleration control, where the magnitude and direction of the thrust acceleration are constant in the tangential–normal–out-of-plane (TNH) frame. Based on the presented linearized thrust-control matrix, which is used to construct the first-order relationships between the relative position, velocity, and the constant-vector thrust acceleration, two analytical approximate solutions are presented for two types of relative orbit transfer problems: the one-vector thrust acceleration solution to the relative orbit transfer problem, which only requires the final relative position, and the double-vector thrust acceleration solution to the relative orbit transfer problem, which requires the final relative position and velocity. Furthermore, for the cases where the magnitude constraint of the thrust provided by the engine is required, fast-iterative algorithms are proposed to obtain the one-vector acceleration solution and the double-vector acceleration solution that satisfy the magnitude constraint strictly. The simulation results showed that the proposed methods are rapid, accurate, and easy to implement, demonstrating their wide application potential for engineering practice.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 715-735"},"PeriodicalIF":3.1,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143173859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-08DOI: 10.1016/j.actaastro.2024.12.058
Karel Hernández Bandrich, Steven G. Tragesser
The design of a tethered spacecraft to image exoplanets using the solar gravitational lens (SGL) is investigated. This mission would require the spacecraft to travel to a distance of at least 547 AU from the sun, where the semi-infinite focal line of the SGL begins, and rasterize pixel by pixel the exoplanet image, which could have a diameter on the order of 1 km. In addition, the spacecraft would need to perform trajectory control to stay within the time-varying focal line, which moves due to, among other factors, the orbit of the exoplanet about its parent star. Rotating tethered spacecraft provide an interesting potential mission architecture, as they do not require thrust to achieve coverage of the roughly 1 km image, reserving it instead only to perform center of mass trajectory control. Equations of motion are derived for collinear configurations with two and three subsatellites, and tether retrieval and deployment laws are developed that take into account the geometry of the Archimedean spiral—ideal for imaging or interferometry applications. Trajectory control schemes with one and two thrusters in the case of two subsatellites and three thrusters in the case of three subsatellites are considered. In addition, the vibrational behavior of the viscoelastic tethers is analyzed. Simulations are carried out for realistic conditions in an example mission to image a hypothetical Earth-like exoplanet. The results reveal some inherent challenges of covering the entire image plane with two subsatellites, which the three-subsatellite configuration addresses. Results also show that no vibration control is necessary as the vibration amplitude is negligible. Estimates of the total imaging time are 2.5 months for a two-subsatellite spacecraft and 16.8 days for a three-subsatellite configuration.
{"title":"Exoplanet imaging along a time-varying focal line using tethered spacecraft","authors":"Karel Hernández Bandrich, Steven G. Tragesser","doi":"10.1016/j.actaastro.2024.12.058","DOIUrl":"10.1016/j.actaastro.2024.12.058","url":null,"abstract":"<div><div>The design of a tethered spacecraft to image exoplanets using the solar gravitational lens (SGL) is investigated. This mission would require the spacecraft to travel to a distance of at least 547 AU from the sun, where the semi-infinite focal line of the SGL begins, and rasterize pixel by pixel the exoplanet image, which could have a diameter on the order of 1 km. In addition, the spacecraft would need to perform trajectory control to stay within the time-varying focal line, which moves due to, among other factors, the orbit of the exoplanet about its parent star. Rotating tethered spacecraft provide an interesting potential mission architecture, as they do not require thrust to achieve coverage of the roughly 1 km image, reserving it instead only to perform center of mass trajectory control. Equations of motion are derived for collinear configurations with two and three subsatellites, and tether retrieval and deployment laws are developed that take into account the geometry of the Archimedean spiral—ideal for imaging or interferometry applications. Trajectory control schemes with one and two thrusters in the case of two subsatellites and three thrusters in the case of three subsatellites are considered. In addition, the vibrational behavior of the viscoelastic tethers is analyzed. Simulations are carried out for realistic conditions in an example mission to image a hypothetical Earth-like exoplanet. The results reveal some inherent challenges of covering the entire image plane with two subsatellites, which the three-subsatellite configuration addresses. Results also show that no vibration control is necessary as the vibration amplitude is negligible. Estimates of the total imaging time are 2.5 months for a two-subsatellite spacecraft and 16.8 days for a three-subsatellite configuration.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 391-405"},"PeriodicalIF":3.1,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143173396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-07DOI: 10.1016/j.actaastro.2025.01.007
Farouk Abdulhamid, Brendan P. Sullivan, Sergio Terzi
The emergence of the new space economy, driven by national space agencies' efforts to reduce costs and promote independent commercial space stations, has led to the rise of private entities such as SpaceX, RedWire, and Blue Origin. This shift, coupled with the anticipated withdrawal of government bodies and the development of smaller, cost-effective commercial space stations, is expected to lead to changes in the design, manufacturing, and logistics of space infrastructure. Currently, the characteristics of space structures are inherently limited by launch constraints, affecting mass, volume, and costs. To address these challenges, the concept of Factory in Space (FIS) has been introduced, significantly impacting space exploration by enabling direct servicing, manufacturing, and assembly of space systems in orbit, thereby circumventing launch limitations. This paper provides an overview of current research and development efforts regarding the various technologies and materials explored for FIS applications, with an emphasis on manufacturing and related technologies. The concept of a closed-loop factory reinforces the crucial role of in-situ material utilization (ISMU), and Additive Manufacturing (AM) is identified as particularly advantageous due to its speed, flexibility, and customizability, offering clear benefits over traditional manufacturing methods. Lastly, the paper identifies areas for further research to advance the potential of FIS, highlighting significant progress in in-space manufacturing.
{"title":"Factory in space: A review of material and manufacturing technologies","authors":"Farouk Abdulhamid, Brendan P. Sullivan, Sergio Terzi","doi":"10.1016/j.actaastro.2025.01.007","DOIUrl":"10.1016/j.actaastro.2025.01.007","url":null,"abstract":"<div><div>The emergence of the new space economy, driven by national space agencies' efforts to reduce costs and promote independent commercial space stations, has led to the rise of private entities such as SpaceX, RedWire, and Blue Origin. This shift, coupled with the anticipated withdrawal of government bodies and the development of smaller, cost-effective commercial space stations, is expected to lead to changes in the design, manufacturing, and logistics of space infrastructure. Currently, the characteristics of space structures are inherently limited by launch constraints, affecting mass, volume, and costs. To address these challenges, the concept of Factory in Space (FIS) has been introduced, significantly impacting space exploration by enabling direct servicing, manufacturing, and assembly of space systems in orbit, thereby circumventing launch limitations. This paper provides an overview of current research and development efforts regarding the various technologies and materials explored for FIS applications, with an emphasis on manufacturing and related technologies. The concept of a closed-loop factory reinforces the crucial role of in-situ material utilization (ISMU), and Additive Manufacturing (AM) is identified as particularly advantageous due to its speed, flexibility, and customizability, offering clear benefits over traditional manufacturing methods. Lastly, the paper identifies areas for further research to advance the potential of FIS, highlighting significant progress in in-space manufacturing.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 90-112"},"PeriodicalIF":3.1,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143174219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-07DOI: 10.1016/j.actaastro.2025.01.004
Shao Nie, Fei Qin, Jinying Ye, Xianggeng Wei, Guoqiang He
One of the principal research subjects within the field of rocket-based combined cycle (RBCC) engines has been the ejector mode, which has been the focus of research for a considerable period of time. The objective of this paper is to present a detailed analysis to the ejector mode of kerosene-fueled RBCC engine. The matching mechanism of the diffusion and afterburning (DAB) mode was obtained through a combination of experiment, theoretical modeling, and numerical simulation. The thrust gain of the sea-level ejector mode was subsequently analyzed. The findings indicate that: (1) In the DAB mode, the requirement of the thermal or geometric throat area ratio is small. The difficulty in organizing the thermal throat has led to the use of a geometric throat to achieve choking on the engine. The results of the model calculation indicate that a thrust gain of 25.2 % for a sea-level ejector mode can be achieved by employing a throat area ratio of 1.83. (2) For the sea-level ejector mode, the mixing requirement can be satisfied when the length of the mixing section reaches 4 times the hydraulic diameter of the rocket nozzle outlet's section. The use of a throat area ratio of 1.8 allows for a thrust gain of 15.9 % in the sea-level ejector mode. The presence of fuel pylons has been observed to reduce thrust gain. (3) The matching mechanism of sea-level ejector mode is revealed. When the rocket flow rate, bypass ratio, combustion organization and throat area ratio match, the maximum thrust gain can be achieved.
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