Solar Power Sail Research Articles

Sample return system of OKEANOS—The solar power sail for Jupiter Trojan exploration

The Japan Aerospace Exploration Agency had planned a sample return from the Jupiter Trojans using a solar power sail in its Oversize Kite-craft for Exploration and AstroNautics in the Outer Solar system (OKEANOS) mission. Solar power sail is an extended concept of solar sail consisting of a sail membrane covered with flexible solar arrays. OKEANOS is capable of generating a large amount of power sufficient to drive high-specific-impulse ion engines in the outer solar system, thus making it possible to perform sample return from the Jupiter Trojans. Various innovative technologies are needed to realize such a challenging mission in the distant space. Specifically, OKEANOS deploys a small lander to ensure the safety and save propellant of the mother spacecraft. The lander collects samples of the asteroid, and separates them into different groups, namely, those for in-situ analysis and those for return. After completing the in-situ analysis, the lander lifts off the asteroid, docks with the mother spacecraft, and delivers the samples to the reentry capsule mounted on the mother spacecraft. The reentry capsule is designed so that it can manage the reentry speed of 15 km/s. Although OKEANOS was proposed as a Japanese large-class mission and advanced to the final selection, it was not selected because of a cost issue. However, its sample return concept is inherited by small- and massive-body explorations coming in the next generations. In this paper, we report the state-of-the-art technologies that enable sample returns from the outer solar system, which were developed through the OKEANOS mission study.

Analytical Investigation of Global Deployed Shape of a Spinning Solar Sail Membrane

In this paper, the deployed shape of spinning square solar sails was investigated through dynamic nonlinear finite element analysis of the full model of the solar power sail of the world’s first solar sail: Interplanetary Kite-craft Accelerated by Radiation of the Sun (IKAROS). The on-orbit photographs of IKAROS revealed that the sail membrane was deformed toward the sun and the membrane maintained its deployed shape during very low-spin-rate operations. To clarify the mechanism of the deformation and high stiffness, the authors of the present study previously performed deployed shape analyses of one-quarter of one square sail by employing Abaqus and reported that the phenomenon was probably caused by curvatures of thin-film devices attached to the membrane. In this study, a finite element model of the entire square sail of IKAROS was created. Furthermore, deployed shape analysis under several combinations of curvatures and spin rates was conducted by employing the dynamic solver “Abaqus/Explicit.” The results indicated that the sail deformations were induced by the curvatures of thin-film devices and that umbrella and saddle shapes appeared owing to the curvatures. The results also indicated that the electric harnesses between the sail and spacecraft supported the sail shape when the spin rate was low.

Solar electric propulsion by a solar power sail for small spacecraft missions to the outer solar system

Outer solar system exploration by a small spacecraft using a solar power sail is investigated. A solar power sail is an extended form of a solar sail that has thin-film solar cells attached over its surface. This concept makes it possible to generate a large amount of power with less weight resources than conventional means. Thereby, even a small spacecraft, which has a strong constraint on available resources, can drive high-power ion thrusters to obtain large ΔV. Combining electric propulsion with gravity assists allows the spacecraft to reach the outer solar system using less propellant. The spacecraft can not only survive by means of solar power in the outer solar system, but also drive electric thrusters there to perform challenging missions such as asteroid or comet rendezvous. In this paper, a framework for exploring the outer solar system using a 50-kg-class small spacecraft is presented. The characteristics of solar electric propulsion under the solar power sail model are disclosed, and a design scheme for missions to the outer planets and beyond are addressed. Providing the specific design of the 50-kg-class solar power sail-craft, Centaur rendezvous mission design is performed as a feasibility study.

Solar power sail membrane prototype for OKEANOS mission

This paper reports on the manufacturing and evaluation of a solar power sail membrane prototype for the OKEANOS project. The in-house prototype was built by the Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency. Mechanical and electrical evaluation tests were conducted. The membrane, thin-film solar cells, reflectivity control devices were good condition after the manufacturing and handling. The improvements in the manufacturing process and design were found. The manufacturing process and design were fundamentally established. After the prototype, improvement plans for the manufacturing process and design were tried. We have a prospect of manufacturing the flight model sail and continue to the development.

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 IKAROS 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.

Influence of thin-film device with curvature on natural frequency of rectangle membrane under uniaxial tension

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.

Science exploration and instrumentation of the OKEANOS mission to a Jupiter Trojan asteroid using the solar power sail

An engineering mission OKEANOS to explore a Jupiter Trojan asteroid, using a Solar Power Sail is currently under study. After a decade-long cruise, it will rendezvous with the target asteroid, conduct global mapping of the asteroid from the spacecraft, and in situ measurements on the surface, using a lander. Science goals and enabling instruments of the mission are introduced, as the results of the joint study between the scientists and engineers from Japan and Europe.

薄膜デバイスの反りおよび曲げ剛性を考慮したIKAROS展張形状の評価

IKAROS is a solar power sail demonstrator launched by JAXA in 2010. IKAROS successfully deployed its large sail by a centrifugal force due to the spin motion of the spacecraft body and obtained a solar power sail navigation. In the evaluation of IKAROS membrane shape, some unexpected phenomena were observed; (1) tether connecting IKAROS membrane and main body got loose in spite of normal spin rate, and (2) the membrane was not warped by photon pressure in spite of low spin rate. The purpose of this paper is to understand generation mechanisms about these unexpected phenomena. Because thin-film devices of thin-film solar cell and reflectivity control device are multilayer film structures, curves occur. The bending stiffness of IKAROS membrane is increased due to the curve. This paper presents the multi-particle model of the membrane considering curve and bending moment of thin-film device. The membrane shape is estimated by numerical simulations and the influence of the thin-film device is made clear.

Shape Estimation of Gossamer Structures Using Distributed Sun-Angle Measurements

This paper proposes a novel approach to monitor the shape of gossamer structures, such as solar sails, using sun-angle measurements obtained directly on the sail membrane. These measurements can be easily provided by already installed thin-film solar arrays or dedicated low-impact sensors. A general nonlinear least-squares formulation is first presented, and then it is reduced to a linear least-squares problem for large sails. A rank deficiency is observed in the estimation method, but it is avoided by considering measurements at multiple epochs, reconstructing a time-averaged shape. Multiparticle models of the Japan Aerospace Exploration Agency’s IKAROS and solar power sail are used to evaluate the performance of the method. The method provides accurate shape estimation with errors of 0.1–0.5 m. Including additional sensors in critical locations can help reduce the error when a low number of sensors is used. In addition, the forces and torques generated by solar radiation pressure are computed and compared with the multiparticle model data. The presented results suggest that the proposed method can easily provide continuous shape estimation of gossamer structures such as solar sails.

Report on the workshop for Jupiter Trojan Exploration by Solar Power Sail

Report on the workshop for Jupiter Trojan Exploration by Solar Power Sail

Demonstration of Sail Deployment by IKAROS and Improvement for Next Solar Power Sail Mission

Demonstration of Sail Deployment by IKAROS and Improvement for Next Solar Power Sail Mission

OS1217 ソーラー電力セイルにおけるシューレース構造を用いた新たな機構の提案

A solar power sail demonstrator IKAROS, which was launched in 2010, could accelerate and decelerate by receiving solar radiation pressure to its membrane surface in outer space. However, the membrane surface becomes uneven easily, because the membrane is very thin. The unevenness causes swirling motion, changing the spin rate and deterioration of the power conversion efficiency. In this study, we proposed a shoelace structure to solve this problem. Effect of a shoelace structure for connecting divided sails on stress fields of sails was analyzed by using ABAQUS. Experimental design using orthogonal table revealed the conditions for reducing the compressive stress. In addition, optimal angle in consideration of the interaction has been derived.

G1900105 ソーラー電力セイルにおけるブリッジ構造の膜面応力場に及ぼす影響

G1900105 ソーラー電力セイルにおけるブリッジ構造の膜面応力場に及ぼす影響

On-orbit Result and Analysis of Sail Deployment of World's First Solar Power Sail IKAROS

On-orbit Result and Analysis of Sail Deployment of World's First Solar Power Sail IKAROS

Challenges and Results on Attitude Control Operation of World’s First Solar Power Sail IKAROS

Challenges and Results on Attitude Control Operation of World’s First Solar Power Sail IKAROS

Development and Operation Summary of World’s First Solar Power Sail IKAROS

Development and Operation Summary of World’s First Solar Power Sail IKAROS

Microparticle impact calibration of the Arrayed Large-Area Dust Detectors in INterplanetary space (ALADDIN) onboard the solar power sail demonstrator IKAROS

The Arrayed Large-Area Dust Detectors in INterplanetary space (ALADDIN) is an array of polyvinylidene fluoride (PVDF) based dust detectors aboard the solar power sail demonstrator named IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun). The total sensor area of ALADDIN (0.54m2) is the world׳s largest among the past PVDF-based dust detectors. IKAROS was launched in May 2010 and then ALADDIN measured cosmic dust impacts for 16 months while orbiting around between 0.7 and 1.1 AU. The main scientific objective of ALADDIN is to reveal number density of ≥10-μm-sized dust in the zodiacal cloud with much higher time-space resolution than that achieved by any past in-situ measurements. The distribution of ≥10-μm-sized dust can be also observed mainly with the light scattering by optical instruments. This paper gives the scientific objectives, the instrumental description, and the results of microparticle impact calibration of ALADDIN conducted in ground laboratories. For the calibration tests we used Van de Graaf accelerators (VdG), two-stage light gas guns (LGG), and a nano-second pulsed Nd:YAG laser (nsPL). Through these experiments, we obtained depolarization charge signal caused by hypervelocity impacts or laser irradiation using the flight spare of 20-μm-thick PVDF sensor and the electronics box of ALADDIN. In the VdG experiment we accelerated iron, carbon, and silver microparticles at 1–30km/s, while in the LGG experiment we performed to shoot 100׳s-μm-sized particles of soda-lime glass and stainless steel at 3–7km/s as single projectile. For interpolation to ≥10-μm size, we irradiated infrared laser at the energy of 15–20mJ directly onto the PVDF sensor. From the signal analysis, we developed a calibration law for estimation of masses of impacted dust particles. The dynamic range of ALADDIN corresponds from 9×10−14kg to 2×10−10kg (4−56μm in diameter at density of 2.0g/cm3) at the expected impact velocity of 10km/s at 1 AU on the IKAROS inbound orbit. It was found that ALADDIN has ability to measure spatial densities of interplanetary dust particles larger than 10μm in size by setting the sensor threshold to an output voltage of 1V.

Mission Analysis of Sample Return from Jovian Trojan Asteroid by Solar Power Sail

Mission Analysis of Sample Return from Jovian Trojan Asteroid by Solar Power Sail

折り目剛性を考慮した宇宙膜構造の非対称展開挙動の解析

A solar power sail demonstrator “IKAROS” deployed its square large membrane successfully by centrifugal force. The deployment consisted of two stages. The flight data suggest that the membrane deployment in the second stage was remarkably non-synchronous. This paper reproduces the non-synchronous deployment behavior using a small experimental model deployed in a vacuum chamber. Then, two kinds of finite-element analyses are conducted to show that the effect of membrane creases may have caused the non-synchronous deployment.