Like the title says, I'm trying to find the name of a story I read in an anthology in the early 1980s. It was about an AI-controlled spaceship that returns to Earth after fighting aliens in the constellation Sagittarius. The ship is very irreverent for an AT, which I loved as a teenage reader.
I remember a slew of details - The ship was robotic because of the distances involved. - The ship was the only survivor of a fleet that was built and sent off to fight the aliens. - The ship gets back to Earth and discovers that the fighting knocked it into an parallel universe where mankind stopped exploring space at the end of the Apollo program.
There's a scene where two old rockets are launched at the spaceship and the AI is appalled by how primitive they are. And the attack causes the ship to realize that it is orbiting an alternate Earth because that is the only way to explain why it looks the same but they don't know what the ship is: their own creation.
The spaceship also determines that the alien threat exists in this universe as well and that the Earth is unaware of the danger headed its way.
Realizing that it must do something to provoke humanity to prepare for the alien onslaught the AI transmits a threat to all nations and crashes into the Earth but in a way calculated to preserve enough of itself that humanity can salvage the technology from ships remains.
It was a great yarn to me and I really liked how the jaded and snide AI ends up nobly sacrificing itself to get humanity to prepare for a looming threat. I know it was the first story in an anthology but have long-since lost the book.
I'd love to find it and re-read to see if it's even half as good as I thought it was. Thanks.