While on the surface, it time ended and teleported me back to the portal. Lost everything inside, but I can recover. I have extras for this reason.
It’s the 2nd time this has happened, but I didn’t die last time so didn’t lose anything.
Perhaps add a teleporter/portal on the surface near where it drops you (in the middle of the radiation zone)? As a structure with a core it would also show up on scans and the map. At least have it take us back to the beginning portal.