Doomsday Machine (1976)

Spies discover that the Red Chinese have built a doomsday machine capable of destroying the surface of the Earth, and that they plan to use it within a matter of days. Meanwhile, Project Astra, a manned U.S. space mission to Venus, is in its final hours before launch when it is taken over by the military and nearly half of its all-male crew is replaced by women. The reason for this becomes apparent when, shortly after Astra leaves orbit, the Earth is completely destroyed in a global cataclysm! Is the human race doomed? What dangers and wonders await the crew of the Astra on their journey to Venus? —yortsnave