Poul Anderson’s 1962 After Doomsday is a standalone science fiction novel.
Twenty years after first contact with galactic civilization, humanity has assimilated much off-world technology. The Americans send a mission of exploration, the USS Benjamin Franklin, to the core of the galaxy and back. The Franklin returns to an Earth scoured clean of life, orbited by alien missiles.
At least three hundred humans have survived the apocalypse: the three hundred on board the Franklin. Thanks to American views on staffing potentially dangerous missions, all three hundred are men.