Pub Date : 2024-11-14DOI: 10.1016/j.actaastro.2024.11.020
Jinyao Zhu , Jia Ma , Jinbao Chen , Chen Wang , Yunfeng Li , Zhihao Fan , Chaoyu Lu
Traditional lunar landers face challenges due to strict flatness requirements at landing sites and the need to avoid complex terrains, which significantly limits their exploration capabilities and success rates. Additionally, their focus on stable landings often compromises their maneuverability, reducing adaptability to various lunar terrains. To address these issues, this study introduces a walkable cat-legged lander (WCLL) inspired by feline landing mechanisms. The WCLL integrates features from both traditional landers and rovers, enabling it to perform high-load landings and navigate effectively across diverse lunar surfaces. It utilizes magnetorheological dampers to dissipate impact energy and employs a soft-landing control method, achieving stable landings under various conditions, including vertical velocities of 3 m/s, payloads of 1280 kg, slopes of 15°, and horizontal disturbances at speeds of 2 m/s. Compared to the Chang'e−3 lander, the WCLL shows a 66.7 % increase in slope adaptability and a 22.6 % improvement in resistance to horizontal disturbances. Finally, experimental validation confirms the accuracy of the simulation model, providing valuable insights for future lunar exploration robot design.
{"title":"Improving landing stability and terrain adaptability in Lunar exploration with biomimetic lander design and control","authors":"Jinyao Zhu , Jia Ma , Jinbao Chen , Chen Wang , Yunfeng Li , Zhihao Fan , Chaoyu Lu","doi":"10.1016/j.actaastro.2024.11.020","DOIUrl":"10.1016/j.actaastro.2024.11.020","url":null,"abstract":"<div><div>Traditional lunar landers face challenges due to strict flatness requirements at landing sites and the need to avoid complex terrains, which significantly limits their exploration capabilities and success rates. Additionally, their focus on stable landings often compromises their maneuverability, reducing adaptability to various lunar terrains. To address these issues, this study introduces a walkable cat-legged lander (WCLL) inspired by feline landing mechanisms. The WCLL integrates features from both traditional landers and rovers, enabling it to perform high-load landings and navigate effectively across diverse lunar surfaces. It utilizes magnetorheological dampers to dissipate impact energy and employs a soft-landing control method, achieving stable landings under various conditions, including vertical velocities of 3 m/s, payloads of 1280 kg, slopes of 15°, and horizontal disturbances at speeds of 2 m/s. Compared to the Chang'e−3 lander, the WCLL shows a 66.7 % increase in slope adaptability and a 22.6 % improvement in resistance to horizontal disturbances. Finally, experimental validation confirms the accuracy of the simulation model, providing valuable insights for future lunar exploration robot design.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"226 ","pages":"Pages 860-875"},"PeriodicalIF":3.1,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702666","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}
On January 20, 2024, Smart Lander for Investigating Moon (SLIM) landed on the Moon. Vision-Based Navigation (VBN) was used to estimate the position of the spacecraft accurately and autonomously during the descent phase, and it was successfully used in each of the seven regions. Obstacle detection was also performed 50 m above the lunar surface, successfully identifying safe points within the field of view of the navigation camera. As a result, SLIM was the first mission to realize pinpoint lunar landing technology with 100 m accuracy. This paper details the VBN operational concept and developed components, as well as the flight results of VBN in SLIM’s lunar landing operations.
{"title":"Vision-based navigation and obstacle detection flight results in SLIM lunar landing","authors":"Takayuki Ishida , Seisuke Fukuda , Kazuki Kariya , Hiroyuki Kamata , Keiki Takadama , Hirohisa Kojima , Shujiro Sawai , Shinichiro Sakai","doi":"10.1016/j.actaastro.2024.11.002","DOIUrl":"10.1016/j.actaastro.2024.11.002","url":null,"abstract":"<div><div>On January 20, 2024, Smart Lander for Investigating Moon (SLIM) landed on the Moon. Vision-Based Navigation (VBN) was used to estimate the position of the spacecraft accurately and autonomously during the descent phase, and it was successfully used in each of the seven regions. Obstacle detection was also performed 50 m above the lunar surface, successfully identifying safe points within the field of view of the navigation camera. As a result, SLIM was the first mission to realize pinpoint lunar landing technology with 100 m accuracy. This paper details the VBN operational concept and developed components, as well as the flight results of VBN in SLIM’s lunar landing operations.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"226 ","pages":"Pages 772-781"},"PeriodicalIF":3.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661039","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 : 2024-11-12DOI: 10.1016/j.actaastro.2024.10.069
Xiaokang Liu , Xiaolin Xiang , Xiaoyu Yu , Qingfei Fu , Lijun Yang , Jingxuan Li
This paper presents a detailed comparative analysis and discussion of two typical predictive methods for combustion instability in long flame combustion chambers: the coupled method and the decoupled method. Using large eddy simulation (LES), the coupled method directly predicts stability in typical long flame combustion chambers. In the decoupled method, stability in the combustion chamber is predicted by combining a low-order acoustic network for long flames with flame responses and mean parameters from numerical simulations. The research results indicate that the coupled method provides full-field information, while the decoupled method neglects certain factors, such as the coupling between combustion and acoustics. However, the decoupled method can directly determine combustion instability based on the growth rate of oscillation modes. The flow field undergoes periodic changes, with the region of fluctuation in the combustion heat release rate gradually increasing, resembling vortex development, which ruptures upon encountering the wall due to radial constraints. Furthermore, in the decoupled method, the periodic changes in the flow field are controlled by the frequency of incoming flow disturbances, whereas in the coupled method, they are controlled by the acoustic frequency of the combustion chamber. In the coupled method, the coupling among disturbances and the acoustic disturbances at the boundaries amplifies the disturbances, causing the radial scale of the fluctuation region in the combustion heat release rate to increase along the axial direction and approach a fixed value faster than in the decoupled method.
{"title":"On the two approaches for the combustion instability predictions in a long-flame combustor","authors":"Xiaokang Liu , Xiaolin Xiang , Xiaoyu Yu , Qingfei Fu , Lijun Yang , Jingxuan Li","doi":"10.1016/j.actaastro.2024.10.069","DOIUrl":"10.1016/j.actaastro.2024.10.069","url":null,"abstract":"<div><div>This paper presents a detailed comparative analysis and discussion of two typical predictive methods for combustion instability in long flame combustion chambers: the coupled method and the decoupled method. Using large eddy simulation (LES), the coupled method directly predicts stability in typical long flame combustion chambers. In the decoupled method, stability in the combustion chamber is predicted by combining a low-order acoustic network for long flames with flame responses and mean parameters from numerical simulations. The research results indicate that the coupled method provides full-field information, while the decoupled method neglects certain factors, such as the coupling between combustion and acoustics. However, the decoupled method can directly determine combustion instability based on the growth rate of oscillation modes. The flow field undergoes periodic changes, with the region of fluctuation in the combustion heat release rate gradually increasing, resembling vortex development, which ruptures upon encountering the wall due to radial constraints. Furthermore, in the decoupled method, the periodic changes in the flow field are controlled by the frequency of incoming flow disturbances, whereas in the coupled method, they are controlled by the acoustic frequency of the combustion chamber. In the coupled method, the coupling among disturbances and the acoustic disturbances at the boundaries amplifies the disturbances, causing the radial scale of the fluctuation region in the combustion heat release rate to increase along the axial direction and approach a fixed value faster than in the decoupled method.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"226 ","pages":"Pages 814-826"},"PeriodicalIF":3.1,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661016","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 : 2024-11-12DOI: 10.1016/j.actaastro.2024.11.018
Yi-Lung Huang , Jordan H. Hsieh , Wei-Cheng Wang , Yueh-Heng Li
This study investigated the discharge voltage characteristics of an argon-fed lanthanum hexaboride heaterless hollow cathode to assess the influence of flow rate, discharge current, background pressure, and applied magnetic field strength. Decreasing the flow rate from 15 to 3 sccm led to a considerable increase in discharge voltage and peak-to-peak oscillation, particularly for flow rates below 5 sccm. Subsequently, variation in discharge current was tested at 4–7 A; this test revealed that the discharge voltage decreases from 53 to 48 V as the discharge current increases, while the peak-to-peak oscillation increases by approximately 2 V with the rise in discharge current. At high background pressures (8.1 × 10−4 Torr), the discharge voltage decreased by 15 V, and the peak-to-peak oscillation was maintained at 5 V. Furthermore, the spectral analysis of the discharge voltage indicated the occurrence of high-energy oscillations at 10–500 kHz owing to ionization instability. The discharge voltage decreased when the strength of an externally applied axial magnetic field increased from 0 to 118 G. Such a result can be attributed to increased ionization (caused by the applied magnetic field) in the emitter and cathode-keeper region, thereby decreasing sheath potential on the emitter surface.
本研究调查了氩气馈电六硼化镧无加热器空心阴极的放电电压特性，以评估流量、放电电流、背景压力和外加磁场强度的影响。将流速从 15 sccm 降低到 3 sccm 会导致放电电压和峰峰振荡显著增加，尤其是流速低于 5 sccm 时。随后，测试了放电电流在 4-7 A 时的变化；测试显示，随着放电电流的增加，放电电压从 53 V 下降到 48 V，而峰峰振荡则随着放电电流的增加而增加约 2 V。在高背景压力（8.1 × 10-4 托）下，放电电压降低了 15 V，峰-峰振荡保持在 5 V。此外，放电电压的频谱分析表明，由于电离不稳定性，在 10-500 kHz 处出现了高能振荡。当外部施加的轴向磁场强度从 0 G 增加到 118 G 时，放电电压降低。这种结果可归因于发射极和阴极保持区的电离增加（由施加的磁场引起），从而降低了发射极表面的鞘势。
{"title":"Investigation of discharge voltage characteristics of a lanthanum hexaboride heaterless hollow cathode","authors":"Yi-Lung Huang , Jordan H. Hsieh , Wei-Cheng Wang , Yueh-Heng Li","doi":"10.1016/j.actaastro.2024.11.018","DOIUrl":"10.1016/j.actaastro.2024.11.018","url":null,"abstract":"<div><div>This study investigated the discharge voltage characteristics of an argon-fed lanthanum hexaboride heaterless hollow cathode to assess the influence of flow rate, discharge current, background pressure, and applied magnetic field strength. Decreasing the flow rate from 15 to 3 sccm led to a considerable increase in discharge voltage and peak-to-peak oscillation, particularly for flow rates below 5 sccm. Subsequently, variation in discharge current was tested at 4–7 A; this test revealed that the discharge voltage decreases from 53 to 48 V as the discharge current increases, while the peak-to-peak oscillation increases by approximately 2 V with the rise in discharge current. At high background pressures (8.1 × 10<sup>−4</sup> Torr), the discharge voltage decreased by 15 V, and the peak-to-peak oscillation was maintained at 5 V. Furthermore, the spectral analysis of the discharge voltage indicated the occurrence of high-energy oscillations at 10–500 kHz owing to ionization instability. The discharge voltage decreased when the strength of an externally applied axial magnetic field increased from 0 to 118 G. Such a result can be attributed to increased ionization (caused by the applied magnetic field) in the emitter and cathode-keeper region, thereby decreasing sheath potential on the emitter surface.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"226 ","pages":"Pages 760-771"},"PeriodicalIF":3.1,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661038","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 : 2024-11-10DOI: 10.1016/j.actaastro.2024.11.017
M.V. Chernyshov, K.E. Savelova
The translational effects of gas streams, which form after the triple-shock configurations at Mach reflection of blast waves with normal main shock (so-called stationary Mach configurations), were analyzed. Unlike in the case of an elevated explosions of fuel as rocket starts in initially stagnant air, which is considered here as a private case, it was supposed that this shock-wave structure moves in a preceding flow with arbitrary velocity (and corresponding flow Mach number). Analyzing relations of the dynamic pressures across the slipstream, which emanates from the triple point of the Mach reflection, it was shown that the flows after the triple-shock configuration usually differ much in their translational action on surrounding objects. It was found and discussed that some configurations drag the objects initially situated above and below the triple-point trajectory in opposite directions. Moreover, the “trigger” structure was found that remains previous flow drag action on the object above the triple-point trajectory, but switches it to exactly opposite one, if the object is situated below the triple point.
{"title":"Extreme translational impact of triple-shock configurations of blast waves in a confined volume of an orbital station","authors":"M.V. Chernyshov, K.E. Savelova","doi":"10.1016/j.actaastro.2024.11.017","DOIUrl":"10.1016/j.actaastro.2024.11.017","url":null,"abstract":"<div><div>The translational effects of gas streams, which form after the triple-shock configurations at Mach reflection of blast waves with normal main shock (so-called stationary Mach configurations), were analyzed. Unlike in the case of an elevated explosions of fuel as rocket starts in initially stagnant air, which is considered here as a private case, it was supposed that this shock-wave structure moves in a preceding flow with arbitrary velocity (and corresponding flow Mach number). Analyzing relations of the dynamic pressures across the slipstream, which emanates from the triple point of the Mach reflection, it was shown that the flows after the triple-shock configuration usually differ much in their translational action on surrounding objects. It was found and discussed that some configurations drag the objects initially situated above and below the triple-point trajectory in opposite directions. Moreover, the “trigger” structure was found that remains previous flow drag action on the object above the triple-point trajectory, but switches it to exactly opposite one, if the object is situated below the triple point.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"226 ","pages":"Pages 876-891"},"PeriodicalIF":3.1,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702601","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}
The work is devoted to the study of gasification of porous material under the conditions of a gas generator of a propulsion system. A low-temperature gas generator for producing combustible gases can be included in a solid fuel engine. The effect of urotropine particle size on the characteristics of its gasification under the conditions of a low-temperature gas generator was experimentally studied. For this purpose, urotropine particles of various fractions were used: 2–3, 3–5, 5–7 and 7–10 mm. It is shown that there is a particle size value above which the gasification characteristics are practically independent of this parameter. The effect of particle size on gasification characteristics only appears for particle size values below a certain size. This is explained by a decrease in the permeability of the porous bed as the particle size decreases.
{"title":"Effect of particle size on gasification of solid fuel in a low-temperature gas generator","authors":"M.V. Salganskaya, A. Yu Zaichenko, D.N. Podlesniy, M.V. Tsvetkov, Yu Yu Tsvetkova, E.A. Salgansky","doi":"10.1016/j.actaastro.2024.11.016","DOIUrl":"10.1016/j.actaastro.2024.11.016","url":null,"abstract":"<div><div>The work is devoted to the study of gasification of porous material under the conditions of a gas generator of a propulsion system. A low-temperature gas generator for producing combustible gases can be included in a solid fuel engine. The effect of urotropine particle size on the characteristics of its gasification under the conditions of a low-temperature gas generator was experimentally studied. For this purpose, urotropine particles of various fractions were used: 2–3, 3–5, 5–7 and 7–10 mm. It is shown that there is a particle size value above which the gasification characteristics are practically independent of this parameter. The effect of particle size on gasification characteristics only appears for particle size values below a certain size. This is explained by a decrease in the permeability of the porous bed as the particle size decreases.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"226 ","pages":"Pages 648-652"},"PeriodicalIF":3.1,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660954","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 : 2024-11-09DOI: 10.1016/j.actaastro.2024.11.015
Eduardo Sebastián , Germán Martínez , Miguel Ramos , Michael D. Smith , Verónica Peinado , Luis Mora , Mark T. Lemmon , Álvaro de Vicente-Retortillo , Javier de Lucas , Ricardo Ferrándiz , José A. Rodríguez-Manfredi
This article describes a novel procedure and algorithm used for the in-flight calibration of the Thermal Infrared Sensor (TIRS) onboard the Mars 2020 mission. The purpose is to recalibrate the responsivity of TIRS’ IR detectors as they degrade following surface operations and exposure to harsh environmental conditions. Using data from in-flight calibration campaigns conducted through sol 800 of this mission, we report the time evolution of the responsivity for the different IR detectors, as well as the final performance achieved by the algorithm in the real operating environment. Moreover, we analyzed changes in responsivity as a function of TIRS geometric design and environmental factors, e.g., detector orientation, direct exposure to prevailing winds and solar radiation, electrostatic properties of the detector filter, and atmospheric dust concentration. We concluded that dust deposition on the detectors' filter during landing, and later during operation is the most likely cause of the degradation observed in the various channels, with gravitational sedimentation and the capacity of the filters to accumulate electrostatic charge being key factors. The relative and absolute degradation of the TIRS is similar to those reported by other Martian missions and instruments with similar orientations, and to date, it has shown no signs of cleaning after more than a year on the surface of Mars. Accounting for changes in responsivity during the mission is critical to maintaining the reliability of TIRS measurements, which will later be made available in NASA's Planetary Data System for the benefit of the scientific community.
{"title":"In-flight calibration of the MEDA-TIRS instrument onboard NASA's Mars2020 mission","authors":"Eduardo Sebastián , Germán Martínez , Miguel Ramos , Michael D. Smith , Verónica Peinado , Luis Mora , Mark T. Lemmon , Álvaro de Vicente-Retortillo , Javier de Lucas , Ricardo Ferrándiz , José A. Rodríguez-Manfredi","doi":"10.1016/j.actaastro.2024.11.015","DOIUrl":"10.1016/j.actaastro.2024.11.015","url":null,"abstract":"<div><div>This article describes a novel procedure and algorithm used for the in-flight calibration of the Thermal Infrared Sensor (TIRS) onboard the Mars 2020 mission. The purpose is to recalibrate the responsivity of TIRS’ IR detectors as they degrade following surface operations and exposure to harsh environmental conditions. Using data from in-flight calibration campaigns conducted through sol 800 of this mission, we report the time evolution of the responsivity for the different IR detectors, as well as the final performance achieved by the algorithm in the real operating environment. Moreover, we analyzed changes in responsivity as a function of TIRS geometric design and environmental factors, e.g., detector orientation, direct exposure to prevailing winds and solar radiation, electrostatic properties of the detector filter, and atmospheric dust concentration. We concluded that dust deposition on the detectors' filter during landing, and later during operation is the most likely cause of the degradation observed in the various channels, with gravitational sedimentation and the capacity of the filters to accumulate electrostatic charge being key factors. The relative and absolute degradation of the TIRS is similar to those reported by other Martian missions and instruments with similar orientations, and to date, it has shown no signs of cleaning after more than a year on the surface of Mars. Accounting for changes in responsivity during the mission is critical to maintaining the reliability of TIRS measurements, which will later be made available in NASA's Planetary Data System for the benefit of the scientific community.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"226 ","pages":"Pages 791-802"},"PeriodicalIF":3.1,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661090","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 : 2024-11-09DOI: 10.1016/j.actaastro.2024.10.065
Christian Bianchi, Lorenzo Niccolai, Giovanni Mengali
Reinforcement learning is used to design minimum-time trajectories of solar sails subject to the typical sources of uncertainty associated with such a propulsion system, i.e., inaccurate knowledge of the sail’s optical properties and the presence of wrinkles on the sail membrane. A proximal policy optimization (PPO) algorithm is used to train the agent and derive the control policy that associates the optimal sail attitude with each dynamic state. First, the agent is trained assuming deterministic unperturbed dynamics, and the results are compared with optimal solutions found by an indirect optimization method, thus demonstrating the effectiveness of this approach. Next, two stochastic scenarios are analysed. In the first, the optical coefficients of the sail are assumed to be random variables with Gaussian distribution, which leads to random variations in the sail characteristic acceleration. In the second scenario, wrinkles on the sail membrane are taken into account, resulting in a misalignment of the thrust vector with respect to a perfectly smooth surface. Both phenomena are modelled based on experimental measurements available in the literature in order to perform realistic analyses. In the stochastic scenarios, Monte Carlo simulations are performed using the trained policies, demonstrating that the reinforcement learning approach is capable of finding near time-optimal solutions, while also being robust to the sources of uncertainty considered.
{"title":"Robust solar sail trajectories using proximal policy optimization","authors":"Christian Bianchi, Lorenzo Niccolai, Giovanni Mengali","doi":"10.1016/j.actaastro.2024.10.065","DOIUrl":"10.1016/j.actaastro.2024.10.065","url":null,"abstract":"<div><div>Reinforcement learning is used to design minimum-time trajectories of solar sails subject to the typical sources of uncertainty associated with such a propulsion system, i.e., inaccurate knowledge of the sail’s optical properties and the presence of wrinkles on the sail membrane. A proximal policy optimization (PPO) algorithm is used to train the agent and derive the control policy that associates the optimal sail attitude with each dynamic state. First, the agent is trained assuming deterministic unperturbed dynamics, and the results are compared with optimal solutions found by an indirect optimization method, thus demonstrating the effectiveness of this approach. Next, two stochastic scenarios are analysed. In the first, the optical coefficients of the sail are assumed to be random variables with Gaussian distribution, which leads to random variations in the sail characteristic acceleration. In the second scenario, wrinkles on the sail membrane are taken into account, resulting in a misalignment of the thrust vector with respect to a perfectly smooth surface. Both phenomena are modelled based on experimental measurements available in the literature in order to perform realistic analyses. In the stochastic scenarios, Monte Carlo simulations are performed using the trained policies, demonstrating that the reinforcement learning approach is capable of finding near time-optimal solutions, while also being robust to the sources of uncertainty considered.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"226 ","pages":"Pages 702-715"},"PeriodicalIF":3.1,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661036","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 : 2024-11-09DOI: 10.1016/j.actaastro.2024.11.013
David B. Spencer , Didier Alary , Valentin Eder , Peter Martinez , Stijn Lemmens , Kawamoto Satomi , Morgane Lecas , Jose María Hermoso
Adherence to debris mitigation guidelines is critical for future robust space traffic management (STM). Debris mitigation guidelines are reviewed and their effectiveness at managing the space object population are contrasted against the means to comply with the guidelines. Specific concerns related to the deployment of large constellations are detailed to provide potential trade-offs for consideration in enhanced tracking systems to enable safe and efficient STM practices. The balance between reducing future debris deposition and minimizing the operational burden on satellites to maintain reliable operations are examined.
{"title":"Effective compliance to technical regulations - Why is compliance to the orbital debris mitigation rules so poor?","authors":"David B. Spencer , Didier Alary , Valentin Eder , Peter Martinez , Stijn Lemmens , Kawamoto Satomi , Morgane Lecas , Jose María Hermoso","doi":"10.1016/j.actaastro.2024.11.013","DOIUrl":"10.1016/j.actaastro.2024.11.013","url":null,"abstract":"<div><div>Adherence to debris mitigation guidelines is critical for future robust space traffic management (STM). Debris mitigation guidelines are reviewed and their effectiveness at managing the space object population are contrasted against the means to comply with the guidelines. Specific concerns related to the deployment of large constellations are detailed to provide potential trade-offs for consideration in enhanced tracking systems to enable safe and efficient STM practices. The balance between reducing future debris deposition and minimizing the operational burden on satellites to maintain reliable operations are examined.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"226 ","pages":"Pages 839-845"},"PeriodicalIF":3.1,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661017","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}
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