Doomsday Machine - 1972

Doomsday Machine, also known as Escape from Planet Earth (video title), is an American science fiction film mostly filmed in 1967 but completed without the original cast or sets in 1972.
A spy 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.
Production of Doomsday Machine began in 1967 under Herbert J. Leder's direction under the titles Armageddon 1975 and Doomsday Plus Seven. Production stopped on the film before it was completed (presumably due to funding problems), and the unfinished footage lay in storage for several years. Production resumed in 1972, though without benefit of access to the original cast members, costumes or sets.