[Knut]

For structural integrity, the giant tube likely would be steel rather than the beautiful clear fantasy material seen in promotional materials. If the steel is welded together, it will be extremely resistant to air leaks, but it will thermally expand and contract as one giant mass, which would require a lot of engineering to allow the structure to move freely. If the system instead is made of a great number of small steel tubes connected by joints, those joints must be able to maintain the integrity of the vacuum. And the engineering must be perfect: If one joint fails, the result is catastrophic.

https://bigthink.com/the-future/elon...erloop-193494/