In what way is this a solar sail? It's a drag sail. From the article, it seems to me that the sun doesn't propel it any more than the sun propels my car.
It would be interesting to see if the magsail or electric sail concepts are developed as well. The simplest design appears to be the electric sail, which only needs radial conductive wires (easy to manufacture and deploy, although it needs to be launched well outside the Earth's magnetosphere).
I see that this is expected to, as one outcome, help reduce further space junk in orbit. I wonder what impact existing space junk - which is predominately small pieces of metal orbiting the earth at speed - would have on the sails?
Without knowing its altitude, even the 70-120 day lifespan makes it a target. I wonder how resistant a 10m^2 piece of thin polymer sheet would be to a lazy 2-inch screw hurtling into it?
"For reasons engineers still don't fully understand, NanoSail-D spontaneously ejected itself." Best line of the article!
Is it a sail or a drag parachute?
Not quite. According to the article, the Japanese deployed a solar sail with a Venus probe. This, though, is the world's first solar sail on a probe designed for Earth orbit.