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NPC Construction Vessels for these stations are deployed at some stage during the plot. There isn't a mission associated with them and they will work away in the background without player intervention.These CVs will be replaced if they are destroyed if stage 1 of their station has not been built. If they are destroyed after that, they won't be and the station won't extend further. However even if they are not destroyed, these stations do not become fully extended.
It's not possible to deploy Trade Agents to these CVs so you'll either need to be nearby them and order wares remotely, or if you have a Trade Computer their offers will remain known for a while but can become inaccurate over time. Since the local system is unable to produce most of the wares needed for station manufacture and NPC galaxy traders may have other priorities, these stations may not be constructed promptly without player intervention.
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