Folding solar panels for satellites
Satellites need electricity to run electronics, mostly for communications and control systems, but also, if they're up there for scientific purposes, for whatever experiments they're doing. Most - not all - of these satellites use solar panels as power sources. You probably know that the Voyager spacecraft used nuclear cells for power. That's because they were travelling out of the solar system and sunlight out there is very weak.
But most panels are destined for smaller satellites that have no humans nearby. So laboriously unfolding complex shapes, or assembling individual components is not the ideal way of doing it.
A Japanese scientist called Koryo Miura came up with a method of folding panels so that all the satellite needs to do is extend the panel in one direction - diagonally. The fold is called the Miura-ori, and is based on parallelograms. The whole panel folds down into a rectangle, which can be long or short, depending on the shape of the parallelograms.
I've made two out of paper. One has nearly rectangular parallelograms, and the other has nearly diamond-shaped ones. The nearly square one folds into a very compact shape. The other one folds into a long rectangular bundle.
I find these patterns and the technique fascinating and enormously aesthetic. What's more, it's something you can try at home during a lockdown.