The solar power sail is an original Japanese concept in which electric power is generated by thin-film solar cells attached on the solar sail membrane.Japan Aerospace Exploration Agency(JAXA)successfully demonstrated ...The solar power sail is an original Japanese concept in which electric power is generated by thin-film solar cells attached on the solar sail membrane.Japan Aerospace Exploration Agency(JAXA)successfully demonstrated the world’s first solar power sail technology through IKAROS(Interplanetary Kite-craft Accelerated by Radiation of the Sun)mission in 2010.IKAROS demonstrated photon propulsion and power generation using thin-film solar cells during its interplanetary cruise.Scaled up,solar power sails can generate enough power to drive high specific impulse ion thrusters in the outer planetary region.With this concept,we propose a landing or sample return mission to directly explore a Jupiter Trojan asteroid using solar power sail-craft OKEANOS(Oversize Kite-craft for Exploration and AstroNautics in the Outer Solar System).After rendezvousing with a Trojan asteroid,a lander separates from OKEANOS to collect samples,and perform in-situ analyses in three proposed mission sequences,including sending samples back to Earth.This paper proposes a system design for OKEANOS and includes analyses of the latest mission.展开更多
A solar power sail demonstrator“IKAROS”demonstrated solar sailing technology in 2010.The membrane of the spinning solar sail IKAROS is estimated to be deformed toward the Sun.The deformation was kept even under low ...A solar power sail demonstrator“IKAROS”demonstrated solar sailing technology in 2010.The membrane of the spinning solar sail IKAROS is estimated to be deformed toward the Sun.The deformation was kept even under low spin-rate.Previous studies suggest that curvature of thin-film solar cells on the membrane increases the out-of-plane stiffness by finite element analysis.Shape,out-of-plane stiffness,and natural frequency of membranes have to be predicted for solar sails with thin-film devices,such as thin-film solar cells,dust counters,and reflectivity control devices in order to reduce the margins of sail size and propellant mass against disturbance solar pressure torque acting on the membrane.In this paper,the effect of a curved thin-film device on the natural frequency of a rectangle membrane under uniaxial tension was investigated.Three types of membranes were evaluated:a membrane with a curved thin-film device,a membrane with a flat thin-film device,and a plane membrane.Geometric nonlinear finite element analysis and eigenvalue analysis were conducted to investigate the natural frequencies under varying tension.The simulations were verified by vibration experiments.It was found that under low tension,the natural frequency of the membrane with the curved thin-film device is significantly higher than that of the others and that under high tension,the natural frequency of the membrane with the thin-film device is slightly lower than that of the plane membrane.In addition,parametric analysis on the curvature of the thin-film device shows that natural frequency at low tension is sensitive to the curvature.The eigenvalue analysis of a whole solar sail with the curved thin-film devices also suggests that the curvature remarkably affects the vibration modes.In conclusion,curved thin-film devices have a significant impact on the out-of-plane stiffness of a membrane under low tension.展开更多
The Japanese interplanetary probe Hayabusa2 was launched on December 3,2014 and the probe arrived at the vicinity of asteroid 162173 Ryugu on June 27,2018.During its 1.4 years of asteroid proximity phase,the probe suc...The Japanese interplanetary probe Hayabusa2 was launched on December 3,2014 and the probe arrived at the vicinity of asteroid 162173 Ryugu on June 27,2018.During its 1.4 years of asteroid proximity phase,the probe successfully accomplished numbers of record-breaking achievements including two touchdowns and one artificial cratering experiment,which are highly expected to have secured surface and subsurface samples from the asteroid inside its sample container for the first time in history.The Hayabusa2 spacecraft was designed not to orbit but to hover above the asteroid along the sub Earth line.This orbital and geometrical configuration allows the spacecraft to utilize its high-gain antennas for telecommunication with the ground station on Earth while pointing its scientific observation and navigation sensors at the asteroid.This paper focuses on the regular station-keeping operation of Hayabusa2,which is called“home position”(HP)-keeping operation.First,together with the spacecraft design,an operation scheme called HP navigation(HPNAV),which includes a daily trajectory control and scientific observations as regular activities,is introduced.Following the description on the guidance,navigation,and control design as well as the framework of optical and radiometric navigation,the results of the HP-keeping operation including trajectory estimation and delta-V planning during the entire asteroid proximity phase are summarized and evaluated as a first report.Consequently,this paper states that the HP.keeping operation in the framework of HPNAV had succeeded without critical incidents,and the number of trajectory control delta-V was planned fficiently throughout the period.展开更多
文摘The solar power sail is an original Japanese concept in which electric power is generated by thin-film solar cells attached on the solar sail membrane.Japan Aerospace Exploration Agency(JAXA)successfully demonstrated the world’s first solar power sail technology through IKAROS(Interplanetary Kite-craft Accelerated by Radiation of the Sun)mission in 2010.IKAROS demonstrated photon propulsion and power generation using thin-film solar cells during its interplanetary cruise.Scaled up,solar power sails can generate enough power to drive high specific impulse ion thrusters in the outer planetary region.With this concept,we propose a landing or sample return mission to directly explore a Jupiter Trojan asteroid using solar power sail-craft OKEANOS(Oversize Kite-craft for Exploration and AstroNautics in the Outer Solar System).After rendezvousing with a Trojan asteroid,a lander separates from OKEANOS to collect samples,and perform in-situ analyses in three proposed mission sequences,including sending samples back to Earth.This paper proposes a system design for OKEANOS and includes analyses of the latest mission.
基金This work was supported by JSPS KAKENHI Grant Number 17H01349 and the ISAS/JAXA solar power sail preparation team.
文摘A solar power sail demonstrator“IKAROS”demonstrated solar sailing technology in 2010.The membrane of the spinning solar sail IKAROS is estimated to be deformed toward the Sun.The deformation was kept even under low spin-rate.Previous studies suggest that curvature of thin-film solar cells on the membrane increases the out-of-plane stiffness by finite element analysis.Shape,out-of-plane stiffness,and natural frequency of membranes have to be predicted for solar sails with thin-film devices,such as thin-film solar cells,dust counters,and reflectivity control devices in order to reduce the margins of sail size and propellant mass against disturbance solar pressure torque acting on the membrane.In this paper,the effect of a curved thin-film device on the natural frequency of a rectangle membrane under uniaxial tension was investigated.Three types of membranes were evaluated:a membrane with a curved thin-film device,a membrane with a flat thin-film device,and a plane membrane.Geometric nonlinear finite element analysis and eigenvalue analysis were conducted to investigate the natural frequencies under varying tension.The simulations were verified by vibration experiments.It was found that under low tension,the natural frequency of the membrane with the curved thin-film device is significantly higher than that of the others and that under high tension,the natural frequency of the membrane with the thin-film device is slightly lower than that of the plane membrane.In addition,parametric analysis on the curvature of the thin-film device shows that natural frequency at low tension is sensitive to the curvature.The eigenvalue analysis of a whole solar sail with the curved thin-film devices also suggests that the curvature remarkably affects the vibration modes.In conclusion,curved thin-film devices have a significant impact on the out-of-plane stiffness of a membrane under low tension.
文摘The Japanese interplanetary probe Hayabusa2 was launched on December 3,2014 and the probe arrived at the vicinity of asteroid 162173 Ryugu on June 27,2018.During its 1.4 years of asteroid proximity phase,the probe successfully accomplished numbers of record-breaking achievements including two touchdowns and one artificial cratering experiment,which are highly expected to have secured surface and subsurface samples from the asteroid inside its sample container for the first time in history.The Hayabusa2 spacecraft was designed not to orbit but to hover above the asteroid along the sub Earth line.This orbital and geometrical configuration allows the spacecraft to utilize its high-gain antennas for telecommunication with the ground station on Earth while pointing its scientific observation and navigation sensors at the asteroid.This paper focuses on the regular station-keeping operation of Hayabusa2,which is called“home position”(HP)-keeping operation.First,together with the spacecraft design,an operation scheme called HP navigation(HPNAV),which includes a daily trajectory control and scientific observations as regular activities,is introduced.Following the description on the guidance,navigation,and control design as well as the framework of optical and radiometric navigation,the results of the HP-keeping operation including trajectory estimation and delta-V planning during the entire asteroid proximity phase are summarized and evaluated as a first report.Consequently,this paper states that the HP.keeping operation in the framework of HPNAV had succeeded without critical incidents,and the number of trajectory control delta-V was planned fficiently throughout the period.