“China is investigating how to build ultra-large spacecraft that are up to 0.6 mile (1 kilometer) long. But how feasible is the idea, and what would be the use of such a massive spacecraft?“https://www.livescience.com/mega-spaceship-china-proposal.html
The original title of the Live Science post linked above is “China wants to build…” but this is incorrect. The National Natural Science Foundation of China is proposing a feasibility study. This is not the same thing as “China wants to build a kilometer-long ship.”
Likely the study will find out that it’s just too expensive and not worth it in terms of effort, resources, and maintenance costs. But it may show the benefits of setting up a base on the Moon and then sending materials there to be 3D-printed for future exploration or human colonies elsewhere.
Sending up a ginormous ship from Earth is foolhardy. Figuring out how to build stuff in space is much smarter.