For once the video shows a real prototype. At the moment it can't be steered but the whole thing works by virtue of rotors made out of solar cells and extreme light weight. Worth a watch.

I don't think the rotor is made from solar cells. See the solar cells get covered up at 158 seconds:

https://youtu.be/bf7RjMUXomE?si=PZsAkrJeQ4ichWaw&t=158

...but the electrostatic motor is pretty cool, and is key to the ultra light weight.

I misunderstood the article. Thanks for the correction.

Related: https://news.ycombinator.com/item?id=40989075