Space ship manned by only AI returns home to a different earth, back in time

Question

I read this short story 30 years or more ago.

A space ship is returning home to Earth from a battle. There are no people on board this ship, only an AI and the ship's computer. When the ship tries to contact Earth it gets no immediate response. The ship attempts to make contact for some time and then is successful with Houston Control (I think).

The AI discovers that it is on a different Earth from the one it is from and that it has also traveled back in time. (The enemy the fleet that it fought still exists).

The space ship comes from an Earth were the Greek empire did not get destroyed.

In the end the AI crashes the ship on the Capitol and gets destroyed, but the computer survives so that the human race has the knowledge of how to build ships and defend against the enemy.

Does anyone know the name of this story?

Answer 1

This is Helbent 4 by Stephen Robinett. It's a very amusing story, with the last NASA Houston employee sweeping out Mission Control (prescient!). Helbent 4 has been fighting the Spacethings and can't make the Earth understand the threat, so ends up crashing into the Capitol to get Earth to take the threat seriously (They think he is the spacething).

I read it in "The 1976 World's Best SF", and my room-mate had the Robinett collection "Projections". Wonder whatever happened to Robinett?

(addendum: I just thumbed through the story, and I don't see anything about the Greek empire. There is some information about the alternate timeline but it's mostly just slightly changed from ours: President Harry S. Therman and Darwin's Origin of the Genus, for example. I still think this is what you're looking for, though, everything else matches.)