system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] When a ship separates, what are the regulations for loss of a part?

For example, if we have, say, a ship that separates its saucer empty as a distraction against the Borg, and the Stardrive with all the crew and people runs back home with no damage, would they ever rebuild the saucer? If they did, would they give the new saucer'd ship a new designation and name, or keep the old one on the Stardrive? Or is the regulation in that case just "Always decommission the half-ship, build a new one."?

To be clear, I am not asking if it IS the same ship, I'm familiar with Theseus' Paradox. I'm asking if they'd keep the name and designation.
gpt
I think the stardrive, even without the large emblazonment of the name and registration, would determine if it gets a new name or not.

If the saucer limps back they'd either decommission the ship or, if there was a construction project it could be used on, they'd change it's name and registry.

But if the stardrive just dips out, you've got the engine and most of the weapons from the old ship (everything that would determine its general displacement in the fleet), you could either rebuild the ship and send it back on its mission, use the stardrive alone (if it's essential to keep as many ships in service as possible), or mothball it with the intention of pulling it out later for either use.