I found a video of the Dutch team testing the 'unfolding' mechanism used in the NCLE. It looks like a spool that unwinds.

NCLE antenna deployment test - 25x: https://www.youtube.com/watch?v=hca3MeX-8rw

Web page with video: https://www.isispace.nl/projects/ncle-the-netherlands-china-...

OK, I get it.

It's like an extreme version of metal tape measures. Which are ~flat when rolled up, and then curve enough when unrolled to become ~rigid. But in this case, they seem to become almost cylindrical when unrolled.

I know that it's likely an old design. It's just that I know nothing about satellite design.

Some early Amateur Radio satellites (Project OSCAR) literally did use silver-plated steel tape measures.

http://www.rfcafe.com/references/popular-electronics/oscar-3...

Many university-grade cubesats use tape measure antennas today. They can be easily stored during launch by wrapping them around the satellite body, secured with nylon fishing wire and then released by burning through the nylon with a NiChrome heating element.

Aside- I was talking to a friend who works at a satellite company. He mentioned that one of the forthcoming missions, they are sending up a space-based 3D printer that prints trusses since it's more compact to send up the printer and feedstock than long structural elements. I wonder if you could print your antenna in space to get a larger one (but folding is probably more parsimonious).