Optimization of body configuration and joint-driven attitude stabilization for transformable spacecraft under solar radiation pressure

The solar sail is one of the most promising space exploration systems due to its theoretically infinite specific impulse achieved through solar radiation pressure(SRP).Recently,researchers have proposed“transformable spacecraft”capable of actively reconfiguring their body configurations using actuatable joints.Transformable spacecraft,if used similarly to solar sails,are expected to significantly enhance orbit and attitude control capabilities owing to their high redundancy in control degrees of freedom.However,controlling them becomes challenging due to their large number of inputs,leading previous researchers to impose strong constraints to limit their potential control capabilities.This study focuses on novel attitude control techniques for transformable spacecraft under SRP.We developed two methods,namely,joint angle optimization to obtain arbitrary SRP force and torque,and momentum damping control driven by joint angle actuation.Our proposed methods are formulated in a general manner and can be applied to any transformable spacecraft comprising front faces that can predominantly receive the SRP on each body.The validity of our proposed method is confirmed through numerical simulations.Our study contributes to making most of the high control redundancy of transformable spacecraft without the need for expendable propellants,thus significantly enhancing the orbit and attitude control capabilities.

Quasi-periodic orbits of small solar sails with time-varying attitude around Earth–Moon libration points

This paper proposes new quasi-periodic orbits around Earth–Moon collinear libration points using solar sails.By including the time-varying sail orientation in the linearized equations of motion for the circular restricted three-body problem(CR3BP),four types of quasi-periodic orbits(two types around L1 and two types around L2)were formulated.Among them,one type of orbit around L2 realizes a considerably small geometry variation while ensuring visibility from the Earth if(and only if)the sail acceleration due to solar radiation pressure is approximately of a certain magnitude,which is much smaller than that assumed in several previous studies.This means that only small solar sails can remain in the vicinity of L2 for a long time without propellant consumption.The orbits designed in the linearized CR3BP can be translated into nonlinear CR3BP and high-fidelity ephemeris models without losing geometrical characteristics.In this study,new quasi-periodic orbits are formulated,and their characteristics are discussed.Furthermore,their extendibility to higher-fidelity dynamic models was verified using numerical examples.

Solar power sail mission of OKEANOS

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.

Improvement of sail storage and deployment mechanism for spin-type solar power sail

Deployable membrane structures are expected to be used for large area space structures,such as solar propulsion sails,magnetoplasma sails,drag-deorbiting sails,membrane antennas,and solar power sails.They are lightweight and can be compactly stored at launch.One achievement of the Japan Aerospace Exploration Agency(JAXA)was the successful deployment of a 200 m2 sail using centrifugal force in the IKAROS mission,which was the first solar propulsion sail-craft in history.JAXA has long been studying the technology of spin deployment of sail membranes,and is currently planning the spin deployment of a class sail larger than 2000 m2 as the next step in the development of the IK AROS technology.This paper discusses the unexpected behaviors during on-orbit sail deployment by IKAROS,as well as problems with the sail holding method,and proposes an improved sail storage structure and deployment mechanism for the OKEANOS mission.

Mechanism-free control method of solar/thermal radiation pressure for application to attitude control

Solar radiation pressure(SRP)impinging on spacecraft is usually regarded as a disturbance for attitude motion,but it can be harnessed to solve the very problem it creates.Active SRP control is possible with solar radiation powered thin-film devices such as reflectivity control devices or liquid crystal devices with reflective microstructure.Thermal radiation pressure(TRP)can likewise be used to solve flight attitude problems caused by SRP,TRP,or other factors.TRP on solar cells can be controlled by switching regulators under the control of them,resulting in temperature change.These SRP/TRP controls are free from mechanisms,such as reaction wheels,and thus they do not produce internal disturbances.In addition,the magnitude of SRP/TRP torques is generally much smaller than internal disturbance torques produced by reaction wheels,which creates a potential for precision far beyond that achieved with mechanical controls.This paper summarizes how SRP/TRP can be used by means of numerical simulations of typical control methods.The usefulness of this mechanism-free attitude control is verified for future use on both Earth orbiting satellites and interplanetary spacecraft including solar sails.