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Japan Exploration Agency (JAXA) launched a powered solar sail “Interplanetary Kite-craft Accelerated by Radiation Of the Sun (IKAROS)” on May 21, 2010. One of the primal technologies demonstrated at IKAROS is the spin-deployment of the sail whose diameter is 20 m class. After the launch, two-step deployment operation was performed and successful expansion of the sail was confirmed. This paper shows the flight data and observed dynamic motion during the deployment. At the quasi-static first stage deployment, the spin rate of main body shows little oscillation after each step and then damped quickly. The damping ratio of the spin rate after a later step of deployment is estimated by curve-fitting to be 0.0127. At the dynamic second stage deployment, the nutation motion is maintained within ±1.5 deg/s and the spin rate of main body is converged quickly about 60s after the deployment start. These flight result and observed dynamic motion during the deployment are compared with the results of numerical simulations using multi-particle model. These results show that the multi-particle model can simulate the global behavior of membrane sufficiently except the dumping motion of in-plane oscillation between the main body and the expanded membrane.

In this paper, the spring-mass system model developed for simple numerical simulations of thin membranes is enhanced by taking into account the properties of buckling and creases. The model is applied to the numerical simulations of centrifugal deployments of folded square membranes that are small-scale models for solar sail spacecraft “IKAROS”. First the folding and deployment methods are reviewed. Then the formulation of the enhanced spring-mass system model is explained. Numerical simulations of the centrifugal deployments of two kinds of folded square membranes with different crease intervals are performed and the numerical results are compared with the corresponding experimental results. The deployment behaviors are discussed and the validity of the spring-mass system model is examined.

In the operation of a solar power sail IKAROS, curved thin-film solar cells were assumed to make the membrane deformed. The deformation caused propellant consumption to counteract windmill torque. For a next solar power sail in the Japan Aerospace Exploration Agency, we conducted experiments and finite element simulations of a simplified model of a part of the solar power sail to understand the effect of a small curved thin-film on wrinkles in a thin membrane under uniaxial tension force. We compared shapes of the membrane with the curved thin-film solar cell under varying tension force. Main findings are that wrinkle lines near both lateral sides of a small curved thin film are bended by curvature of the film and occur under varying tension force.

The small solar power sail demonstrator IKAROS was developed and launched in 2010 by JAXA and deployed its large membrane successfully. Through IKAROS's on-orbit operation, one of the most critical problems was a sail's shape imbalance during the sail deployment sequence. This paper focuses on the evaluation and consideration of the sail's imbalance through high vacuum experiments using a scale-down sail model. The experimental results obtained using the specially designed rotating mechanism and a small scale model lead to a hypothesis of the reason for the IKAROS's imbalanced deployment. The experimental results are extrapolated up to IKAROS's scale, using dimensionless analyses.