When I saw this tweet, I got worried.
NASA Webb Telescope on Twitter: ""Liftoff from a tropical rainforest to the edge of time itself..."
Get out your tissues and watch Webb placed into its @ariane5 rocket fairing, then moved to its launch pad. Witness again our historic launch and the start of Webb's epic million-mile (1.5 million km) journey. (link)" / Twitter
The video showed the Ariane 5 rocket in its assembly building, the JWST being lowered into place on top of it, the fairing also lowered into place, then the rocket going out on its launch pad to its launch site, then the rocket's launch, then the JWST being released from the rocket's upper stage.
However nice that video was, it seemed to be filler, and I wondered what had happened to deployment of the mid-booms. I was concerned about the disasters that Skylab and Galileo suffered.
Skylab -
Skylab: First U.S. Space Station | Space
It was built from the third stage of a Saturn V rocket and launched atop the first two stages. About a minute into the launch, a micrometeoroid shield got ripped off of it by the air rushing by, and that ripped off one of the solar arrays and damaged the other.
The first astronauts to visit the station put into place a replacement sunshield and they fully deployed the remaining solar array.
They were the first of three crews, with three astronauts each, staying in space 28, 68, and 84 days. However, a fourth mission was canceled.
Galileo project
The Galileo spacecraft was a Jupiter orbiter and atmosphere probe that was launched in 1989, arriving at Jupiter in 1995. On the way, it made three gravity-assist flybys, one of Venus then two of the Earth, and it also flew by two asteroids, returning pictures of them.
After the Venus flyby, it opened its high-gain antenna. That was much like an umbrella, with 18 graphite-epoxy ribs and a wire-mesh fabric for reflecting wadio waves. The spacecraft was launched with the antenna folded up, with the ribs' ends in sockets on the antenna's central pole. But the antenna did not fully open it. Only 15 ribs moved outward, with 3 stuck in place. The spacecraft's operators were unable to unstick those 3 ribs, and they did the rest of the mission using the spacecraft's low-gain antenna.
Galileo did not return very many pictures, though it did return some of Jupiter's four big moons, and its operators felt satisfied that it had done much of what it was sent to do.
Looking at
James Webb Space Telescope (JWST) - YouTube I find that it has a series: "Elements of Webb". In order, gold, beryllium, Kapton, carbon, silicon
Kapton is not a chemical element, but a kind of plastic that is stable over a very large temperature range: 4 to 673 K (-269 to 400 C).
Back to JWST deployment, the deployment of the mid booms was delayed for checking out the opening of the sunshield covers. But one of them is now deployed, as I write this.