The Radiant Dome (Perry Rhodan No. 2)

In this alternate universe, USSF Major Perry Rhodan and his three fellow astronauts blasted off in a three stage rocket to the Moon in 1971. The first stage of the rocket was chemical, the second and third stages were nuclear. After crashing on the Moon due to a strange radio interference, they discover a massive crashed alien spaceship with an aged male scientist (Khrest), a female commander (Thora), and a crew of 500.