Capricorn One (1978) on Netflix

When the head of NASA's manned Mars missions discovers that the capsule meant to carry the astronauts will suffer a catastrophic failure, he forces the three astronauts to participate in a hoax by broadcasting their 'Mission' from a studio built at a now abandoned air force base. Over the many months of the mission, the astronauts send broadcasts to Earth on their progress and all goes well until their space capsule burns up on re-entry. They soon realize that the only way for the hoax to be maintained is for them to die and they make a desperate attempt to escape their captors. Throughout this period, an investigative reporter gets wind of the fact that something is amiss with man's first mission to Mars and slowly puts together the pieces of the mystery.