Pub Date : 2025-01-17DOI: 10.1016/j.actaastro.2025.01.029
Markus T. Koller , Marius Eggert , Markus Kranz , Lorenz Maurer , Jakob Meier , Robin Müller , Robin Schweigert , Jonas Weihrauch , Felix Gerstenberger , Wolfgang Guter , Torsten Torunski , Sabine Klinkner
An advanced electronic load circuit was developed to characterise the current–voltage curves of seven metal-wrap-through triple-junction solar cells and four conventional quadruple-junction solar cells produced by AZUR SPACE GmbH. This solar cell experiment was launched aboard the EIVE nanosatellite in June 2023 and has been operational since October 2023. The evaluation of over 5,000 individual curves highlights the need for precise compensation of temperature, sun angle error, and solar flux effects. The corrected data show excellent agreement with ground measurements obtained from solar simulator testing of the same cells.
{"title":"Design and first results of the solar cell experiment on EIVE","authors":"Markus T. Koller , Marius Eggert , Markus Kranz , Lorenz Maurer , Jakob Meier , Robin Müller , Robin Schweigert , Jonas Weihrauch , Felix Gerstenberger , Wolfgang Guter , Torsten Torunski , Sabine Klinkner","doi":"10.1016/j.actaastro.2025.01.029","DOIUrl":"10.1016/j.actaastro.2025.01.029","url":null,"abstract":"<div><div>An advanced electronic load circuit was developed to characterise the current–voltage curves of seven metal-wrap-through triple-junction solar cells and four conventional quadruple-junction solar cells produced by AZUR SPACE GmbH. This solar cell experiment was launched aboard the EIVE nanosatellite in June 2023 and has been operational since October 2023. The evaluation of over 5,000 individual curves highlights the need for precise compensation of temperature, sun angle error, and solar flux effects. The corrected data show excellent agreement with ground measurements obtained from solar simulator testing of the same cells.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 627-643"},"PeriodicalIF":3.1,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143173889","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 : 2025-01-17DOI: 10.1016/j.actaastro.2025.01.040
Jing Zhang , Jianlin Liu , Wanjing Jia , Jiayin Li , Chao Sun , Jiachen Nie , Tian Liu , Hetong Wang , Xuerui Ma , Li Ding
NASA has proposed long-duration lunar and Mars habitats operate at 8.0 psia / 32 % O2 atmosphere (the equivalent air altitude [EAA] = 1213 m) nominally with an optional depress to 7.6 psia / 32 % O2 (EAA = 2100 m). To investigate the design extension of atmosphere for emergency scenarios and the biomechanical responses of astronauts performing physical tasks in hypobaric hypoxia, this study analyzed the work performance, upper limb muscles activation and kinematics of ten male participants during repetitive manual material handling (MMH) of 25 kg boxes to fatigue at normobaric normoxia (NN, FiO2 = 20.9 %) and acute hypobaric moderate (MH, FiO2 = 13.6 %) and severe (SH, FiO2 = 11.8 %) hypoxic exposure. The results indicated a significant work performance decrement for per five MMH repetitions at SH (mean ± SD: 76.49 ± 17.47 s) compared to NN (53.09 ± 14.84 s) (P < 0.01). The normalized root mean square (RMS, %MVC) of brachioradialis and erector spinae at fatigue states was significantly higher than those during the starting stage at NN and MH (P < 0.05). The mean power frequency (MPF) of brachioradialis was significantly higher in MH and SH than that in NN (P < 0.01). Both MPF and zero crossing rate (ZCR) of brachioradialis and erector spinae muscles post-MMH were significantly reduced compared to pre-MMH (P < 0.05). Elbow flexion and upper limb acceleration remained unaffected by changes in oxygen levels and fatigue state (P > 0.05). This study provides valuable insights for the design of hypoxic atmospheres in extraterrestrial habitats, as well as for astronaut physical fatigue monitoring and safety protection.
{"title":"Effects of acute hypoxic exposure in extraterrestrial habitats on work performance and biomechanical parameters of manual material handling","authors":"Jing Zhang , Jianlin Liu , Wanjing Jia , Jiayin Li , Chao Sun , Jiachen Nie , Tian Liu , Hetong Wang , Xuerui Ma , Li Ding","doi":"10.1016/j.actaastro.2025.01.040","DOIUrl":"10.1016/j.actaastro.2025.01.040","url":null,"abstract":"<div><div>NASA has proposed long-duration lunar and Mars habitats operate at 8.0 psia / 32 % O<sub>2</sub> atmosphere (the equivalent air altitude [EAA] = 1213 m) nominally with an optional depress to 7.6 psia / 32 % O<sub>2</sub> (EAA = 2100 m). To investigate the design extension of atmosphere for emergency scenarios and the biomechanical responses of astronauts performing physical tasks in hypobaric hypoxia, this study analyzed the work performance, upper limb muscles activation and kinematics of ten male participants during repetitive manual material handling (MMH) of 25 kg boxes to fatigue at normobaric normoxia (NN, FiO<sub>2</sub> = 20.9 %) and acute hypobaric moderate (MH, FiO<sub>2</sub> = 13.6 %) and severe (SH, FiO<sub>2</sub> = 11.8 %) hypoxic exposure. The results indicated a significant work performance decrement for per five MMH repetitions at SH (mean ± SD: 76.49 ± 17.47 s) compared to NN (53.09 ± 14.84 s) (P < 0.01). The normalized root mean square (RMS, %MVC) of brachioradialis and erector spinae at fatigue states was significantly higher than those during the starting stage at NN and MH (P < 0.05). The mean power frequency (MPF) of brachioradialis was significantly higher in MH and SH than that in NN (P < 0.01). Both MPF and zero crossing rate (ZCR) of brachioradialis and erector spinae muscles post-MMH were significantly reduced compared to pre-MMH (P < 0.05). Elbow flexion and upper limb acceleration remained unaffected by changes in oxygen levels and fatigue state (P > 0.05). This study provides valuable insights for the design of hypoxic atmospheres in extraterrestrial habitats, as well as for astronaut physical fatigue monitoring and safety protection.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 345-356"},"PeriodicalIF":3.1,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143174225","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}
This article presents a comprehensive study of the resilient mobility of a four-wheeled lunar rover under various internal and external environmental conditions. The proposed and analyzed mobility approach enhances the adaptability and robustness of a rover with limited resources in harsh environments. An innovative omnidirectional inching locomotion technique was introduced to reinforce access to challenging terrain. This technique was compared with conventional locomotion methods through drawbar pull tests and analyzes using resistive force theory (RFT). Emphasis was placed on functional isolation during actuator failure, achieved by implementing a one-way clutch mechanism. This resilient design ensures the core functionality of the rover and mitigates resource wastage in critical scenarios. The experimental and analytical results highlight the capability of the rover to manage potential actuator failures, offering valuable insights into its adaptability to demanding lunar-like environments. This work demonstrates the capacity of the rover to overcome challenges and efficiently navigate diverse terrain, making it a promising candidate for lunar exploration and construction.
{"title":"Resilient mobility of a four-wheeled planetary rover with active suspension","authors":"Jorge Ruben Casir Ricano, Sota Yuasa, Ryota Hino, Tomoki Koshi, Tatsuya Oyama, Kenji Nagaoka","doi":"10.1016/j.actaastro.2025.01.030","DOIUrl":"10.1016/j.actaastro.2025.01.030","url":null,"abstract":"<div><div>This article presents a comprehensive study of the resilient mobility of a four-wheeled lunar rover under various internal and external environmental conditions. The proposed and analyzed mobility approach enhances the adaptability and robustness of a rover with limited resources in harsh environments. An innovative omnidirectional inching locomotion technique was introduced to reinforce access to challenging terrain. This technique was compared with conventional locomotion methods through drawbar pull tests and analyzes using resistive force theory (RFT). Emphasis was placed on functional isolation during actuator failure, achieved by implementing a one-way clutch mechanism. This resilient design ensures the core functionality of the rover and mitigates resource wastage in critical scenarios. The experimental and analytical results highlight the capability of the rover to manage potential actuator failures, offering valuable insights into its adaptability to demanding lunar-like environments. This work demonstrates the capacity of the rover to overcome challenges and efficiently navigate diverse terrain, making it a promising candidate for lunar exploration and construction.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 418-429"},"PeriodicalIF":3.1,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143174321","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 : 2025-01-16DOI: 10.1016/j.actaastro.2025.01.039
Junli Wang , Zhi Deng , Yuhang Zhang , Chen Liu , Wenli Chen , Jian Wu
Unlike the Earth environment, the Martian atmosphere is mainly composed of carbon dioxide, which is characterized by low temperature and low density, resulting significant effects on the aerodynamic characteristics of air vehicles than those observed at the earth's atmosphere. In this study the effects of working fluids and the geometric designs of airfoils on the aerodynamic performance of 3D wing operating under Martian atmospheric conditions is performed, employing the experimental and numerical approaches. In addition, considering the operating environment of MARS, the effects of Reynolds and Mach numbers have also been studied at a larger scale. The results show that the working fluid does not significantly affect the aerodynamic performance of the wing, which is observed greatly sensitive to the variations in the flow Reynolds numbers, having lesser dependency on the Mach number. And the geometric design of airfoils is observed to greatly influence the wing aerodynamics operating at Martian conditions. Additionally, the numerical results present detailed insights on the stall onset for each operating conditions accompanied by the transformation of small-size high-frequency vortex shedding to large-size low-frequency vortex shedding.
{"title":"Studies on the effect of working fluid and the geometric design of airfoils on the aerodynamic performance of air vehicles operating in Martian atmosphere","authors":"Junli Wang , Zhi Deng , Yuhang Zhang , Chen Liu , Wenli Chen , Jian Wu","doi":"10.1016/j.actaastro.2025.01.039","DOIUrl":"10.1016/j.actaastro.2025.01.039","url":null,"abstract":"<div><div>Unlike the Earth environment, the Martian atmosphere is mainly composed of carbon dioxide, which is characterized by low temperature and low density, resulting significant effects on the aerodynamic characteristics of air vehicles than those observed at the earth's atmosphere. In this study the effects of working fluids and the geometric designs of airfoils on the aerodynamic performance of 3D wing operating under Martian atmospheric conditions is performed, employing the experimental and numerical approaches. In addition, considering the operating environment of MARS, the effects of Reynolds and Mach numbers have also been studied at a larger scale. The results show that the working fluid does not significantly affect the aerodynamic performance of the wing, which is observed greatly sensitive to the variations in the flow Reynolds numbers, having lesser dependency on the Mach number. And the geometric design of airfoils is observed to greatly influence the wing aerodynamics operating at Martian conditions. Additionally, the numerical results present detailed insights on the stall onset for each operating conditions accompanied by the transformation of small-size high-frequency vortex shedding to large-size low-frequency vortex shedding.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 297-310"},"PeriodicalIF":3.1,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990244","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 : 2025-01-16DOI: 10.1016/j.actaastro.2024.12.051
Binfeng Pan, Yunting Ran, Mengxin Zhao
This paper introduces an innovative generalized Gaussian smoothing homotopy method for solving nonlinear optimal control problems using the indirect method. Compared to the original smoothing homotopy methods, this approach leverages a multivariate Gaussian function to smooth both state and costate variables, extending the convolution process beyond the time domain to all unknown variables. By utilizing the separability property of the Gaussian kernel, the multivariate convolution is decomposed into univariate convolutions along each dimension, allowing independent and efficient computation. Additionally, the Gauss–Chebyshev quadrature technique is employed to approximate these univariate convolutions, further reducing computational complexity. The convergence of the method is demonstrated through challenging numerical examples, showcasing its superiority over Gaussian smoothing homotopy method.
{"title":"Generalized Gaussian smoothing homotopy method for solving nonlinear optimal control problems","authors":"Binfeng Pan, Yunting Ran, Mengxin Zhao","doi":"10.1016/j.actaastro.2024.12.051","DOIUrl":"10.1016/j.actaastro.2024.12.051","url":null,"abstract":"<div><div>This paper introduces an innovative generalized Gaussian smoothing homotopy method for solving nonlinear optimal control problems using the indirect method. Compared to the original smoothing homotopy methods, this approach leverages a multivariate Gaussian function to smooth both state and costate variables, extending the convolution process beyond the time domain to all unknown variables. By utilizing the separability property of the Gaussian kernel, the multivariate convolution is decomposed into univariate convolutions along each dimension, allowing independent and efficient computation. Additionally, the Gauss–Chebyshev quadrature technique is employed to approximate these univariate convolutions, further reducing computational complexity. The convergence of the method is demonstrated through challenging numerical examples, showcasing its superiority over Gaussian smoothing homotopy method.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 311-321"},"PeriodicalIF":3.1,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990245","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 : 2025-01-15DOI: 10.1016/j.actaastro.2025.01.008
Mani Kakavand, Zheng H. Zhu
This paper develops a geometric mechanics framework for de-spinning massive asteroids using miniature tethered tugs during the post-capture phase of asteroid redirection missions. The excessive mass disparity between the asteroids and the tug, combined with weak solar gravity in heliocentric orbits at several astronomical units from the Sun, renders the tug-asteroid system severely ill-conditioned. This condition poses challenges for accurately integrating the de-spinning dynamics numerically over extreme long durations. To address these issues, this paper derives the relative equations of motion of the tug-asteroid system via Hamilton’s principle and Lie group theory within a structure-preserving methodology that incorporates tether libration and asteroid attitude dynamics. The asteroid de-spinning control scheme is synthesized through energy shaping to establish system passivity via tether tension control to ensure bounded stability. A discrete-time Lie group Hamiltonian variational integrator is derived based on the Symplectic Partitioned Runge-Kutta method for high accuracy. The strict asymptotic stability of the proposed passivity-based control is proved theoretically. The framework is applied to de-spin asteroids at 1 and 3 astronomical units from the Sun. Numerical results demonstrate enhanced stability over extremely long time integration, which is critical for such missions. Finally, the impact of variations in asteroid’s moment of inertia and initial conditions is analyzed parametrically, revealing that small changes can significantly affect mission duration and the required tether length.
{"title":"Geometric mechanics framework for tethered de-spinning of massive asteroids by small tug using passivity-based control","authors":"Mani Kakavand, Zheng H. Zhu","doi":"10.1016/j.actaastro.2025.01.008","DOIUrl":"10.1016/j.actaastro.2025.01.008","url":null,"abstract":"<div><div>This paper develops a geometric mechanics framework for de-spinning massive asteroids using miniature tethered tugs during the post-capture phase of asteroid redirection missions. The excessive mass disparity between the asteroids and the tug, combined with weak solar gravity in heliocentric orbits at several astronomical units from the Sun, renders the tug-asteroid system severely ill-conditioned. This condition poses challenges for accurately integrating the de-spinning dynamics numerically over extreme long durations. To address these issues, this paper derives the relative equations of motion of the tug-asteroid system via Hamilton’s principle and Lie group theory within a structure-preserving methodology that incorporates tether libration and asteroid attitude dynamics. The asteroid de-spinning control scheme is synthesized through energy shaping to establish system passivity via tether tension control to ensure bounded stability. A discrete-time Lie group Hamiltonian variational integrator is derived based on the Symplectic Partitioned Runge-Kutta method for high accuracy. The strict asymptotic stability of the proposed passivity-based control is proved theoretically. The framework is applied to de-spin asteroids at 1 and 3 astronomical units from the Sun. Numerical results demonstrate enhanced stability over extremely long time integration, which is critical for such missions. Finally, the impact of variations in asteroid’s moment of inertia and initial conditions is analyzed parametrically, revealing that small changes can significantly affect mission duration and the required tether length.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 406-417"},"PeriodicalIF":3.1,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143174274","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 : 2025-01-15DOI: 10.1016/j.actaastro.2025.01.033
Yuanjun Zhang , Zhengbo Yang , Chaoliang Mu , Yuchen Zhang , Hao Zhu , Lidong Wang
Solid paraffin wax doped with sodium borohydride powder can achieve hypergolic ignition in contact with 90 % hydrogen peroxide. This phenomenon is mainly due to the intense redox reaction of sodium borohydride with 90 % hydrogen peroxide, which exotherms and increases the ignitability in solid paraffin fuels. In this study, drop-on-solid tests were conducted under atmospheric conditions to quantify the ignition delay time, which was observed to be lower than 5 ms, indicating that hypergolic ignition in this innovative system is both rapid and efficient, and to characterize the spontaneous ignition behavior. The results obtained confirm the practical feasibility of hypergolic ignition for the selected propellant combinations. In this study, a hybrid rocket motor prototype was designed for engine firing test, and the results showed that the engine combustion efficiency was higher than 87 % under low oxidant-fuel ratio conditions. Its low-delay characteristic makes it suitable for use in areas requiring fast response such as satellite attitude and orbit control.
{"title":"Hypergolic ignition of green propellant: Testing of 90 % hydrogen peroxide with paraffin wax including sodium borohydride","authors":"Yuanjun Zhang , Zhengbo Yang , Chaoliang Mu , Yuchen Zhang , Hao Zhu , Lidong Wang","doi":"10.1016/j.actaastro.2025.01.033","DOIUrl":"10.1016/j.actaastro.2025.01.033","url":null,"abstract":"<div><div>Solid paraffin wax doped with sodium borohydride powder can achieve hypergolic ignition in contact with 90 % hydrogen peroxide. This phenomenon is mainly due to the intense redox reaction of sodium borohydride with 90 % hydrogen peroxide, which exotherms and increases the ignitability in solid paraffin fuels. In this study, drop-on-solid tests were conducted under atmospheric conditions to quantify the ignition delay time, which was observed to be lower than 5 ms, indicating that hypergolic ignition in this innovative system is both rapid and efficient, and to characterize the spontaneous ignition behavior. The results obtained confirm the practical feasibility of hypergolic ignition for the selected propellant combinations. In this study, a hybrid rocket motor prototype was designed for engine firing test, and the results showed that the engine combustion efficiency was higher than 87 % under low oxidant-fuel ratio conditions. Its low-delay characteristic makes it suitable for use in areas requiring fast response such as satellite attitude and orbit control.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 277-285"},"PeriodicalIF":3.1,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143174318","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 : 2025-01-14DOI: 10.1016/j.actaastro.2025.01.020
E. Fantino , R. Flores , G. Donnarumma , D. Canales , K.C. Howell
Near-Earth Objects (NEOs) are asteroids, comets and meteoroids in heliocentric orbits with perihelion below 1.3 au. Similarly to the population of the Main Asteroid Belt, NEOs are primordial bodies, and their study can improve our understanding of the origins of the Solar System. With a catalog of over 30 000 known asteroids and approximately 100 listed short-period comets, the NEO population represents an inventory of exploration targets reachable at a significantly lower cost than the objects of the Main Asteroid Belt. In addition, the materials present in these bodies could be used to resupply spacecraft en route to other destinations. The trajectories of past missions to NEOs have been designed with the patched-conics technique supplemented by impulsive and/or low-thrust maneuvers and planetary gravity assist. The transfer times range from some months to a few years, and the close-approach speeds relative to the target have been as high as 10 km/s. The design technique described in this work leverages the invariant structures of the circular restricted three-body problem (CR3BP) to connect the Earth’s vicinity with NEOs in low-eccentricity and low-inclination trajectories in close proximity to the terrestrial orbit. The fundamental building blocks of the method are periodic orbits around the collinear points L and L of the Sun-Earth CR3BP. These orbits are used to generate paths that follow the associated hyperbolic invariant manifolds, exit the sphere of influence of the Earth and reach NEOs on nearby orbits, thus enabling robotic as well as crewed exploration missions to targets in the terrestrial region and asteroid deflection operations. The strategy is simple, can be applied to depart either a libration point orbit or a geocentric orbit, and offers attractive performance features.
{"title":"Direct low-energy trajectories to Near-Earth Objects","authors":"E. Fantino , R. Flores , G. Donnarumma , D. Canales , K.C. Howell","doi":"10.1016/j.actaastro.2025.01.020","DOIUrl":"10.1016/j.actaastro.2025.01.020","url":null,"abstract":"<div><div>Near-Earth Objects (NEOs) are asteroids, comets and meteoroids in heliocentric orbits with perihelion below 1.3 au. Similarly to the population of the Main Asteroid Belt, NEOs are primordial bodies, and their study can improve our understanding of the origins of the Solar System. With a catalog of over 30 000 known asteroids and approximately 100 listed short-period comets, the NEO population represents an inventory of exploration targets reachable at a significantly lower cost than the objects of the Main Asteroid Belt. In addition, the materials present in these bodies could be used to resupply spacecraft en route to other destinations. The trajectories of past missions to NEOs have been designed with the patched-conics technique supplemented by impulsive and/or low-thrust maneuvers and planetary gravity assist. The transfer times range from some months to a few years, and the close-approach speeds relative to the target have been as high as 10 km/s. The design technique described in this work leverages the invariant structures of the circular restricted three-body problem (CR3BP) to connect the Earth’s vicinity with NEOs in low-eccentricity and low-inclination trajectories in close proximity to the terrestrial orbit. The fundamental building blocks of the method are periodic orbits around the collinear points L<span><math><msub><mrow></mrow><mrow><mn>1</mn></mrow></msub></math></span> and L<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> of the Sun-Earth CR3BP. These orbits are used to generate paths that follow the associated hyperbolic invariant manifolds, exit the sphere of influence of the Earth and reach NEOs on nearby orbits, thus enabling robotic as well as crewed exploration missions to targets in the terrestrial region and asteroid deflection operations. The strategy is simple, can be applied to depart either a libration point orbit or a geocentric orbit, and offers attractive performance features.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 333-344"},"PeriodicalIF":3.1,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143174226","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 : 2025-01-14DOI: 10.1016/j.actaastro.2025.01.011
Michael Matessa
Previous work has developed algorithms for decoding the meaning of an interstellar message from a distant civilization (Matessa, 2022). What about the inverse problem: if you have a concept like the mass of an object that you want to discuss, how can you create a message with that concept that can be easily decoded? This paper describes algorithms for creating a sequence of symbols that introduce concepts leading from basic mathematics to a target concept. The algorithms work with a data structure containing an expression form that relates concepts, a precondition of concepts that have been introduced previously in the message, and a postcondition of concepts that should be understood after the expression form is presented. These algorithms have been implemented in software, and results are shown for creating a message given a target concept. Messages that are created by the algorithms in this paper can be decoded by the algorithms in Matessa (2022). By developing algorithms, it is hoped that message encoding and decoding can grow from an art done by individuals to a science done with algorithms.
{"title":"Algorithms for encoding interstellar messages","authors":"Michael Matessa","doi":"10.1016/j.actaastro.2025.01.011","DOIUrl":"10.1016/j.actaastro.2025.01.011","url":null,"abstract":"<div><div>Previous work has developed algorithms for decoding the meaning of an interstellar message from a distant civilization (Matessa, 2022). What about the inverse problem: if you have a concept like the mass of an object that you want to discuss, how can you create a message with that concept that can be easily decoded? This paper describes algorithms for creating a sequence of symbols that introduce concepts leading from basic mathematics to a target concept. The algorithms work with a data structure containing an expression form that relates concepts, a precondition of concepts that have been introduced previously in the message, and a postcondition of concepts that should be understood after the expression form is presented. These algorithms have been implemented in software, and results are shown for creating a message given a target concept. Messages that are created by the algorithms in this paper can be decoded by the algorithms in Matessa (2022). By developing algorithms, it is hoped that message encoding and decoding can grow from an art done by individuals to a science done with algorithms.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"229 ","pages":"Pages 161-165"},"PeriodicalIF":3.1,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142989647","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 : 2025-01-14DOI: 10.1016/j.actaastro.2025.01.013
Diego Navarro-Tapia , Andrés Marcos , Marc Hirth
This article studies and provides a plausible solution to address the effects of micro-particle impacts on the LISA mission. The influence of these undesired events are analysed using a set of 8 worst-case impact conditions from an ESA database of more than 200,000 impacts that captures the anticipated micro-meteoroid environment that the LISA spacecraft may encounter in a span of its envisioned 6.5 years of mission. Based on the results of this analysis, a novel operational mode called SCIHOLD is proposed to provide fast recovery from micro-meteoroid impacts. The performance of the SCIHOLD mode is validated using a LISA high-fidelity, non-linear simulator in two steps. Firstly, the identified 8 worst-case impacts are evaluated in nominal and dispersed conditions in a Monte Carlo campaign, and secondly, larger impacts beyond the ones in the database are simulated to assess the recovery limits of the proposed recovery mode. The results show that the proposed operational mode is successful in recovering the LISA spacecraft from the impacts, and most importantly, that this is achieved with a mean overall recovery time of 92.5 s, a considerable reduction compared to a full re-acquisition scenario typically lasting hours.
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