Using data from automatic surface weather stations, buoys, lidar and Doppler, the diurnal variation and the three-dimensional structure of the sea breezes near the sailing sites of the Good Luck Beijing- 2006 Qingdao ...Using data from automatic surface weather stations, buoys, lidar and Doppler, the diurnal variation and the three-dimensional structure of the sea breezes near the sailing sites of the Good Luck Beijing- 2006 Qingdao International Regatta from 18 to 31 August 2006 are analyzed. Results show that excluding rainy days and days affected by typhoon, the sea breezes occur nearly every day during this period. When Qingdao is located at the edge of the subtropical high at 500 hPa, the sea breeze is usually stronger, around 3-4 m s^-1. It starts at around 1100 to 1300 LST and lasts about 6 hours. The direction of the sea breeze tends to be southeasterly. When Qingdao is under the control of the subtropical high, the sea breeze is usually weaker, less than 2.5 m s^-1 throughout the day, and begins later, between 1300 and 1500 LST. In this case, the direction of the sea breeze is variable from easterly to southeasterly. Most sea breezes in Qingdao are very shallow, up to 300 meters deep. Strong sea breezes can reach 1.5 km in depth and can push as far as 100 km inland. If the Huanghai sea breeze moves inland and meets the sea breeze of the Jiaozhou Bay in the western part of Qingdao, the sea breeze will strengthen and form three boundaries due to the interaction of the two sea breezes.展开更多
Solar sailing is a promising propellant-free approach to propelling spacecraft in space.However, the propelling efficiency of conventional solar sail spacecraft is limited by their areato-mass ratios. This paper propo...Solar sailing is a promising propellant-free approach to propelling spacecraft in space.However, the propelling efficiency of conventional solar sail spacecraft is limited by their areato-mass ratios. This paper proposes a novel design of micro solar sails with area-to-mass ratios above 100 m^(2)/kg for next-generation chip-scale spacecraft. Bilayer thin films developed by Microelectromechanical Systems(MEMS) technologies were patterned into grid microstructures, and theoretical analysis of a sail prototype was conducted. The electro-thermal and thermo-mechanical models of the solar sail in geospace were established by taking effects of Joule heating, solar radiation, and thermal re-emission into consideration, enabling rapid prediction of its threedimensional(3-D) reconfiguration from the as-released two-dimensional(2-D) microstructure.Adjustment of the Chip Sail's acceleration arising from the sail's morphing was also analytically modeled. Fabrication and characterization of the sail prototype made of multiple Al/Ni_(50)Ti_(50) bilayer beams were accomplished. In-situ SEM imaging of the sail prototype in vacuum chamber witnessed an active and continuous 3-D reconfiguration under Joule heating, and over 90° deformation was detected by applying a DC voltage of 0.078 V. Theoretical and experimental work on the solar sail with at least 10 times higher area-to-mass ratios than conventional ones will lay a solid foundation for efficient solar sailing.展开更多
The election of Donald Trump as US President worries some of the people about reversal of globalization.As Trump talked a lot against globalization,they believe that his election is the beginning of the end of globali...The election of Donald Trump as US President worries some of the people about reversal of globalization.As Trump talked a lot against globalization,they believe that his election is the beginning of the end of globalization.Furthermore,a series of events such as the Brexit and展开更多
This paper attempts to analyze the symbolism that is embodied in"Sailing to Byzantium"and to further understand the spiritual freedom W. B. Yeats expressed in the poem. Studying the contrasts of the symbols ...This paper attempts to analyze the symbolism that is embodied in"Sailing to Byzantium"and to further understand the spiritual freedom W. B. Yeats expressed in the poem. Studying the contrasts of the symbols and the eternity and holy spirit carried by Byzantium, we can understand Yeats' life philosophy, and finally reach his spiritual freedom which perpetuates itself in art.展开更多
In this paper the performance of a BOC-50＇ sailing yacht model in calm water and in realistic sea states is investigated experimentally. A scaled model of the hull form with the keel-bulb configuration has been teste...In this paper the performance of a BOC-50＇ sailing yacht model in calm water and in realistic sea states is investigated experimentally. A scaled model of the hull form with the keel-bulb configuration has been tested in the towing tank of the LSMH of NTUA. During the tests the calm water resistance and the dynamic responses, including the added resistance in waves were recorded. Results referring to the resistance, the side force, the CG displacement, the pitch as well as the vertical accelerations of the model at the bow, the CG and the stern are presented. Moreover, by using a Velocity Prediction Program the polar and the stability diagram of the tested sailing yacht were calculated. Useful conclusions about the dynamic behavior of the model were obtained.展开更多
As the greatest lyric poet of the 20th century,Yeats fully expresses his pursuit of eternal spiritual home in his poem“Sailing to Byzantium”.This paper analyzes the text and discusses how the poet strives to pursue ...As the greatest lyric poet of the 20th century,Yeats fully expresses his pursuit of eternal spiritual home in his poem“Sailing to Byzantium”.This paper analyzes the text and discusses how the poet strives to pursue his spiritual home,so as to deepen our readers’understanding of“eternity”theme in the poem.Seeking the Spiritual Home—Sailing to Byzantium.展开更多
Mr. Du Yuzhou, President of China National Textile and Apparel Council, is still steering the country’s flagship of textile industry. The wheelman has proactively been engaged in promoting the m ark etizatio n proces...Mr. Du Yuzhou, President of China National Textile and Apparel Council, is still steering the country’s flagship of textile industry. The wheelman has proactively been engaged in promoting the m ark etizatio n process with his open- minded, insightful thoughts and free trade philosophy.展开更多
Solar sail technology has been proposed and developed for space explorations with advantages of low launch cost,no-propellant consumption,and continuous thrust,which has great potentials in earth polar detection,inter...Solar sail technology has been proposed and developed for space explorations with advantages of low launch cost,no-propellant consumption,and continuous thrust,which has great potentials in earth polar detection,interstellar explorations and etc.The development of solar sail has made significant progress in structural design,manufacturing,materials,orbit transfer,and stability control in the past few decades,which makes meaningful contributions to astronomy,physics,and aerospace science.Technological breakthroughs of Solar Radiation Pressure(SRP)propulsion and interstellar transfer have been achieved in current solar sail missions.However,there are still many challenges and problems need to be solved.This paper attempts to summarize the research schemes and potential applications of solar sailing in space missions from the viewpoint of key technologies,so as to provide an overall perspective for researchers in this field.Analyses of the key technologies of solar sailing system design are provided.Finally,challenges and prospective development of solar sailing are discussed.展开更多
Purpose The concept of virtual exercise is still a nascent domain for therapeutic intervention.In light of the importance of exercise and the fast development of digital technologies,virtual exercise possesses a promi...Purpose The concept of virtual exercise is still a nascent domain for therapeutic intervention.In light of the importance of exercise and the fast development of digital technologies,virtual exercise possesses a promising potential for future development.Sailing is a recreational exercise that has helped the rehabilitation of patients with neurological and physiological disorders and improved their quality of life.However,challenges exist in implementing physical sailing as an intervention,due to the cost and the extent of uncertainty of this sport.While studies remain limited,over the past twenty years,simulated sailing that combines virtual reality with complex motor learning and optimum decision-making is emerging as a potential digital exercise that possesses broad therapeutic applications for future exploration.This review aims to have a more complete understanding of the clinical application of virtual sailing as an emerging exercise therapy.Methods Literature searches were performed using PubMed,EMBASE and MEDLINE bibliographic databases for research articles published from January 1994 to January 2024(inclusive).We performed a Strength,Weakness,Opportunity and Threat(SWOT)analysis to evaluate the implementation of virtual sailing as a new therapeutic intervention,opening unanswered questions for future investigation.Results Out of 205 articles searched from databases,31 advanced to full-text screening and 7 articles were eligible for inclusion in this narrative review.This review summarises the application and therapeutic efficacy of virtual sailing in improving both motor and psychosocial functions.We also shared our perspectives on developing virtual sailing as an exercise therapy for treating neurodegenerative diseases,focusing on pre-clinical and clinical evidence as well as the proposed mechanism by which virtual sailing could influence neural plasticity in the central nervous system.Conclusion Virtual sailing is a promising exercise therapy feasible for future implementation,although large-scale trial studies involving a diverse range of clinical conditions are required.展开更多
Significant propellant mass saving can be obtained with the use of complex multiple intermediate flyby maneuvers for conventional propulsion systems,and trip time also decreases for a portion of the proper solar sail ...Significant propellant mass saving can be obtained with the use of complex multiple intermediate flyby maneuvers for conventional propulsion systems,and trip time also decreases for a portion of the proper solar sail missions.This paper discusses the performance of gravity assist(GA)in the time-optimal control problem of solar sailing with respect to sail lightness number and the energy difference between the initial and final orbit in the rendezvous problem in a two-body model,in which the GA is modeled as a substantial change in the velocity of the sailcraft at the GA time.In addition,this paper presents a method to solve the time-optimal problem of solar sailing with GA in a full ephemeris model,which introduces the third body’s gravity in a dynamic equation.This study builds a set of inner constraints that can describe the GA process accurately.Finally,this study presents an example for evaluating the accuracy and rationality of the two-body model’s simplification of GA by comparison with the full ephemeris model.展开更多
Shortest path routing protocol intends to minimize the total delay between every pair of destination node and source node. However, it is also well-known that shortest path routing suffers from uneven distribution of ...Shortest path routing protocol intends to minimize the total delay between every pair of destination node and source node. However, it is also well-known that shortest path routing suffers from uneven distribution of traffic load, especially in dense wireless networks. Recently, several new routing protocols are proposed in order to balance traffic load among nodes in a network. One of them is Circular Sailing Routing （CSR） which maps nodes on the surface of a sphere and select routes based on surface distances. CSR has been demonstrated with better load balance than shortest path routing via simulations. However, it is still open that what load distribution CSR can achieve. Therefore, in this paper, we theoretically analyze the traffic load distribution of CSR in a dense circular wireless network. Using the techniques developed by Hytti and Virtamo, we are able to derive the traffic load of any point inside the network. We then conduct extensive simulations to verify our theoretical results with grid and random networks.展开更多
【正】At the 60thanniversary of the China University of Petroleum,I just,on behalf of the China University of Petroleum(Beijing),extend my genuine congratulations and sincere gratitude to all our overseas and domestic...【正】At the 60thanniversary of the China University of Petroleum,I just,on behalf of the China University of Petroleum(Beijing),extend my genuine congratulations and sincere gratitude to all our overseas and domestic alumni,students,faculty and staff.For sixty years,from the start to nowadays,from a weak university to a strong one,it has cultivated over 20,0000 outstanding talents for petroleum industries in China.Students of the China University of Petroleum are sprinkling across the country,like brilliant bright pearls,throughout each corner of the world.At the 60thanniversary of the China University of Petroleum,the alma mater kindly informs each of you that the展开更多
The law of big fish swallowing little fish has expired when it comes to the era of new economy.What prevails nowadays in the sea of commerce is quick fish swallowing slow fish.In the Internet economy,small companies a...The law of big fish swallowing little fish has expired when it comes to the era of new economy.What prevails nowadays in the sea of commerce is quick fish swallowing slow fish.In the Internet economy,small companies are not destined to lose to giants,but slow ones are doomed to become prey of their quick counterparts. The swiftly rising Yongkang Group has made a breakthrough in dental treatment by translating the law into practice.It is called"Law of the Sea."‘Law of the Sea’展开更多
A considerable number of Chinese consumers are taking up the hobby of yachting, reflecting the nation's growing wealth A yacht is an extremely luxurious toy, costing perhaps millions of dollars. Despite this, yach...A considerable number of Chinese consumers are taking up the hobby of yachting, reflecting the nation's growing wealth A yacht is an extremely luxurious toy, costing perhaps millions of dollars. Despite this, yachting has caught on in China in the last 10 years. At the Taihu Lake in Wuxi City, Jiangsu Province, an American-invested yacht展开更多
The orbits of solar sails can be changed by adjusting the sail’s attitude through external control torques.The resulting momentum will be changed,either provided by a typical attitude control subsystem or by a propel...The orbits of solar sails can be changed by adjusting the sail’s attitude through external control torques.The resulting momentum will be changed,either provided by a typical attitude control subsystem or by a propellantless device.This paper investigates the extra momentum input and fuel consumption for a typical attitude control subsystem.The minimum-time transfer trajectories are designed for two rendezvous missions using both indirect and direct methods,generating continuous and discrete attitude histories,respectively.The results show that the momentum variation is almost wholly due to the solar radiation pressure.The feasibility of using tip-mounted microthrusters for attitude control is evaluated.The results show that less than0.1 kg of propellant are required for an interplanetary transfer mission when pulsed plasma thrusters with a specific impulse of700 s and a thrust of 150 mN are mounted at the tip of a 20 m square solar sail.The fuel consumptions of two transfer missions indicate that a tip-mounted pulsed plasma thruster is a viable technique for the attitude control of a solar sail.展开更多
Since the 1960s,an increasing interest in space propulsion methods(a)not-high-limited in energy(e.g.,electric rocket propulsion)and(b)involving no propellant(space sailing),has been advancing from theoretical,numerica...Since the 1960s,an increasing interest in space propulsion methods(a)not-high-limited in energy(e.g.,electric rocket propulsion)and(b)involving no propellant(space sailing),has been advancing from theoretical,numericalsimulation,and technological viewpoints.In particular,among the propulsion concepts of type(b),solar-photon sailing(SPS)has received greater and greater attention.展开更多
On December 12,2020,I cast off with Argo,my trusty boat,for a solo voyage across the Atlantic.As we departed San Sebastian at dawn,the exhaustion from preparation already had me longing for sleep,which was a strange d...On December 12,2020,I cast off with Argo,my trusty boat,for a solo voyage across the Atlantic.As we departed San Sebastian at dawn,the exhaustion from preparation already had me longing for sleep,which was a strange desire on the very first day of what was to be a 70⁃day expedition.展开更多
基金supported by National Natural Science Foun-dation of China Grant (Grant No. 40705017)the Chinese Academy of Sciences Grant (Grant No. 2004-2-7)the Natural Science Foundation of Shandong Province Grant(Grant No. Q2007E03)
文摘Using data from automatic surface weather stations, buoys, lidar and Doppler, the diurnal variation and the three-dimensional structure of the sea breezes near the sailing sites of the Good Luck Beijing- 2006 Qingdao International Regatta from 18 to 31 August 2006 are analyzed. Results show that excluding rainy days and days affected by typhoon, the sea breezes occur nearly every day during this period. When Qingdao is located at the edge of the subtropical high at 500 hPa, the sea breeze is usually stronger, around 3-4 m s^-1. It starts at around 1100 to 1300 LST and lasts about 6 hours. The direction of the sea breeze tends to be southeasterly. When Qingdao is under the control of the subtropical high, the sea breeze is usually weaker, less than 2.5 m s^-1 throughout the day, and begins later, between 1300 and 1500 LST. In this case, the direction of the sea breeze is variable from easterly to southeasterly. Most sea breezes in Qingdao are very shallow, up to 300 meters deep. Strong sea breezes can reach 1.5 km in depth and can push as far as 100 km inland. If the Huanghai sea breeze moves inland and meets the sea breeze of the Jiaozhou Bay in the western part of Qingdao, the sea breeze will strengthen and form three boundaries due to the interaction of the two sea breezes.
基金Supported by Excellent Youth Science Fund Project(Overseas)of Shandong Province,China(No.2023HWYQ-029)China Postdoctoral Science Foundation(No.2023MD744219)+3 种基金Zhejiang Province Selected Funding for Postdoctoral Research Projects,China(No.ZJ2023040)Youth Project of Natural Science Foundation of Shandong Province,China(No.ZR2023QE127)China National University Student Innovation and Entrepreneurship Development Program(No.202310422009)Major Basic Research Program of the Natural Science Foundation of Shandong Province,China(No.ZR2019ZD08).This research was in part carried out at the Center for Functional Nanomaterials(CFN),Brookhaven National Laboratory(BNL),which is supported by the U.S.Department of Energy,Office of Basic Energy Sciences,under Contract No.DE-SC0012704.
文摘Solar sailing is a promising propellant-free approach to propelling spacecraft in space.However, the propelling efficiency of conventional solar sail spacecraft is limited by their areato-mass ratios. This paper proposes a novel design of micro solar sails with area-to-mass ratios above 100 m^(2)/kg for next-generation chip-scale spacecraft. Bilayer thin films developed by Microelectromechanical Systems(MEMS) technologies were patterned into grid microstructures, and theoretical analysis of a sail prototype was conducted. The electro-thermal and thermo-mechanical models of the solar sail in geospace were established by taking effects of Joule heating, solar radiation, and thermal re-emission into consideration, enabling rapid prediction of its threedimensional(3-D) reconfiguration from the as-released two-dimensional(2-D) microstructure.Adjustment of the Chip Sail's acceleration arising from the sail's morphing was also analytically modeled. Fabrication and characterization of the sail prototype made of multiple Al/Ni_(50)Ti_(50) bilayer beams were accomplished. In-situ SEM imaging of the sail prototype in vacuum chamber witnessed an active and continuous 3-D reconfiguration under Joule heating, and over 90° deformation was detected by applying a DC voltage of 0.078 V. Theoretical and experimental work on the solar sail with at least 10 times higher area-to-mass ratios than conventional ones will lay a solid foundation for efficient solar sailing.
文摘The election of Donald Trump as US President worries some of the people about reversal of globalization.As Trump talked a lot against globalization,they believe that his election is the beginning of the end of globalization.Furthermore,a series of events such as the Brexit and
文摘This paper attempts to analyze the symbolism that is embodied in"Sailing to Byzantium"and to further understand the spiritual freedom W. B. Yeats expressed in the poem. Studying the contrasts of the symbols and the eternity and holy spirit carried by Byzantium, we can understand Yeats' life philosophy, and finally reach his spiritual freedom which perpetuates itself in art.
文摘In this paper the performance of a BOC-50＇ sailing yacht model in calm water and in realistic sea states is investigated experimentally. A scaled model of the hull form with the keel-bulb configuration has been tested in the towing tank of the LSMH of NTUA. During the tests the calm water resistance and the dynamic responses, including the added resistance in waves were recorded. Results referring to the resistance, the side force, the CG displacement, the pitch as well as the vertical accelerations of the model at the bow, the CG and the stern are presented. Moreover, by using a Velocity Prediction Program the polar and the stability diagram of the tested sailing yacht were calculated. Useful conclusions about the dynamic behavior of the model were obtained.
文摘As the greatest lyric poet of the 20th century,Yeats fully expresses his pursuit of eternal spiritual home in his poem“Sailing to Byzantium”.This paper analyzes the text and discusses how the poet strives to pursue his spiritual home,so as to deepen our readers’understanding of“eternity”theme in the poem.Seeking the Spiritual Home—Sailing to Byzantium.
文摘Mr. Du Yuzhou, President of China National Textile and Apparel Council, is still steering the country’s flagship of textile industry. The wheelman has proactively been engaged in promoting the m ark etizatio n process with his open- minded, insightful thoughts and free trade philosophy.
基金co-supported by the Natural Science Foundation of China(No.51905527)China Scholarship Council(No.202104910450).
文摘Solar sail technology has been proposed and developed for space explorations with advantages of low launch cost,no-propellant consumption,and continuous thrust,which has great potentials in earth polar detection,interstellar explorations and etc.The development of solar sail has made significant progress in structural design,manufacturing,materials,orbit transfer,and stability control in the past few decades,which makes meaningful contributions to astronomy,physics,and aerospace science.Technological breakthroughs of Solar Radiation Pressure(SRP)propulsion and interstellar transfer have been achieved in current solar sail missions.However,there are still many challenges and problems need to be solved.This paper attempts to summarize the research schemes and potential applications of solar sailing in space missions from the viewpoint of key technologies,so as to provide an overall perspective for researchers in this field.Analyses of the key technologies of solar sailing system design are provided.Finally,challenges and prospective development of solar sailing are discussed.
基金supported by the Swinburne University of Technology Research Seed Fundthe 2023 Barbara Dicker Brain Science Foundation Medical Research Grant to JX.
文摘Purpose The concept of virtual exercise is still a nascent domain for therapeutic intervention.In light of the importance of exercise and the fast development of digital technologies,virtual exercise possesses a promising potential for future development.Sailing is a recreational exercise that has helped the rehabilitation of patients with neurological and physiological disorders and improved their quality of life.However,challenges exist in implementing physical sailing as an intervention,due to the cost and the extent of uncertainty of this sport.While studies remain limited,over the past twenty years,simulated sailing that combines virtual reality with complex motor learning and optimum decision-making is emerging as a potential digital exercise that possesses broad therapeutic applications for future exploration.This review aims to have a more complete understanding of the clinical application of virtual sailing as an emerging exercise therapy.Methods Literature searches were performed using PubMed,EMBASE and MEDLINE bibliographic databases for research articles published from January 1994 to January 2024(inclusive).We performed a Strength,Weakness,Opportunity and Threat(SWOT)analysis to evaluate the implementation of virtual sailing as a new therapeutic intervention,opening unanswered questions for future investigation.Results Out of 205 articles searched from databases,31 advanced to full-text screening and 7 articles were eligible for inclusion in this narrative review.This review summarises the application and therapeutic efficacy of virtual sailing in improving both motor and psychosocial functions.We also shared our perspectives on developing virtual sailing as an exercise therapy for treating neurodegenerative diseases,focusing on pre-clinical and clinical evidence as well as the proposed mechanism by which virtual sailing could influence neural plasticity in the central nervous system.Conclusion Virtual sailing is a promising exercise therapy feasible for future implementation,although large-scale trial studies involving a diverse range of clinical conditions are required.
文摘Significant propellant mass saving can be obtained with the use of complex multiple intermediate flyby maneuvers for conventional propulsion systems,and trip time also decreases for a portion of the proper solar sail missions.This paper discusses the performance of gravity assist(GA)in the time-optimal control problem of solar sailing with respect to sail lightness number and the energy difference between the initial and final orbit in the rendezvous problem in a two-body model,in which the GA is modeled as a substantial change in the velocity of the sailcraft at the GA time.In addition,this paper presents a method to solve the time-optimal problem of solar sailing with GA in a full ephemeris model,which introduces the third body’s gravity in a dynamic equation.This study builds a set of inner constraints that can describe the GA process accurately.Finally,this study presents an example for evaluating the accuracy and rationality of the two-body model’s simplification of GA by comparison with the full ephemeris model.
基金supported by National Natural Science Foundation of China under No. 60903151Beijing Natural Science Foundation under No. 4122070+1 种基金Scientific Research Foundation for the Returned Overseas Chinese Scholars from State Education Ministry of ChinaUS National Science Foundation under Nos.CNS-0915331 and CNS-1050398
文摘Shortest path routing protocol intends to minimize the total delay between every pair of destination node and source node. However, it is also well-known that shortest path routing suffers from uneven distribution of traffic load, especially in dense wireless networks. Recently, several new routing protocols are proposed in order to balance traffic load among nodes in a network. One of them is Circular Sailing Routing （CSR） which maps nodes on the surface of a sphere and select routes based on surface distances. CSR has been demonstrated with better load balance than shortest path routing via simulations. However, it is still open that what load distribution CSR can achieve. Therefore, in this paper, we theoretically analyze the traffic load distribution of CSR in a dense circular wireless network. Using the techniques developed by Hytti and Virtamo, we are able to derive the traffic load of any point inside the network. We then conduct extensive simulations to verify our theoretical results with grid and random networks.
文摘【正】At the 60thanniversary of the China University of Petroleum,I just,on behalf of the China University of Petroleum(Beijing),extend my genuine congratulations and sincere gratitude to all our overseas and domestic alumni,students,faculty and staff.For sixty years,from the start to nowadays,from a weak university to a strong one,it has cultivated over 20,0000 outstanding talents for petroleum industries in China.Students of the China University of Petroleum are sprinkling across the country,like brilliant bright pearls,throughout each corner of the world.At the 60thanniversary of the China University of Petroleum,the alma mater kindly informs each of you that the
文摘The law of big fish swallowing little fish has expired when it comes to the era of new economy.What prevails nowadays in the sea of commerce is quick fish swallowing slow fish.In the Internet economy,small companies are not destined to lose to giants,but slow ones are doomed to become prey of their quick counterparts. The swiftly rising Yongkang Group has made a breakthrough in dental treatment by translating the law into practice.It is called"Law of the Sea."‘Law of the Sea’
文摘A considerable number of Chinese consumers are taking up the hobby of yachting, reflecting the nation's growing wealth A yacht is an extremely luxurious toy, costing perhaps millions of dollars. Despite this, yachting has caught on in China in the last 10 years. At the Taihu Lake in Wuxi City, Jiangsu Province, an American-invested yacht
基金supported by the National Natural Science Foundation of China(Grant No.11272004)China’s Civil Space Funding
文摘The orbits of solar sails can be changed by adjusting the sail’s attitude through external control torques.The resulting momentum will be changed,either provided by a typical attitude control subsystem or by a propellantless device.This paper investigates the extra momentum input and fuel consumption for a typical attitude control subsystem.The minimum-time transfer trajectories are designed for two rendezvous missions using both indirect and direct methods,generating continuous and discrete attitude histories,respectively.The results show that the momentum variation is almost wholly due to the solar radiation pressure.The feasibility of using tip-mounted microthrusters for attitude control is evaluated.The results show that less than0.1 kg of propellant are required for an interplanetary transfer mission when pulsed plasma thrusters with a specific impulse of700 s and a thrust of 150 mN are mounted at the tip of a 20 m square solar sail.The fuel consumptions of two transfer missions indicate that a tip-mounted pulsed plasma thruster is a viable technique for the attitude control of a solar sail.
文摘Since the 1960s,an increasing interest in space propulsion methods(a)not-high-limited in energy(e.g.,electric rocket propulsion)and(b)involving no propellant(space sailing),has been advancing from theoretical,numericalsimulation,and technological viewpoints.In particular,among the propulsion concepts of type(b),solar-photon sailing(SPS)has received greater and greater attention.
文摘On December 12,2020,I cast off with Argo,my trusty boat,for a solo voyage across the Atlantic.As we departed San Sebastian at dawn,the exhaustion from preparation already had me longing for sleep,which was a strange desire on the very first day of what was to be a 70⁃day expedition.
