Doomsday Machine, 1972 film

Doomsday Machine, also known as Escape from Planet Earth (video title), is an American science fiction film filmed in 1967 but completed without the original cast or sets in 1972.

Plot:
A spy (Essie Lin Chia (fr)) discovers that the Chinese government has created a doomsday device (the “key” to which, “only Chairman Mao has”) capable of destroying the Earth and it will be activated in 72 hours. Soon after, Astra – a two-year return mission to Venus by the United States Space Program – has its time of launch speeded up and half of the male flight crew are replaced by women shortly before take-off, including one Russian. Shortly before blastoff military alerts are put into effect.