A Journey Too Far Plus Imposter

Contains two stories. "A Journey Too Far" is about an astronaut who returns to Earth after a long journey to find an Earth devoid of humans, but populated by robots and androids who are at war with each other.
"Imposter" is about a robotics engineer who poses as an android to escape Earth and go to a terradome on Mars before a giant asteroid hits Earth. He is pulled from the ship's passenger list because of a feud with the man in charge of the project. A few of his androids will go, however, to perform menial and hazardous tasks.