In the spaceship, the astronauts have normal gravity though the ship is not spinning to create it. In the spacewalk scenes, they are weightless.
When David is being attacked in his home & somehow loses the link with his replica self, he should have contacted Earth from the spaceship to send someone to help at his house instead of immediately trying to go back into his replica on Earth that had already been subdued.
When David chose to transfer his consciousness back to Earth he didn't know that his replica had been tied up and incapacitated. Even if a message from the spaceship reached Earth immediately it would take at least minutes for help to be sent to his house. By returning to Earth he was attempting to protect his family immediately.
When David chose to transfer his consciousness back to Earth he didn't know that his replica had been tied up and incapacitated. Even if a message from the spaceship reached Earth immediately it would take at least minutes for help to be sent to his house. By returning to Earth he was attempting to protect his family immediately.
A space mission requiring astronauts to remain in space for six years is not feasible. Astronauts experience numerous adverse medical effects besides loss of muscle mass and bone density, including changes in the immune system, increased risk of cancer, increased risk of cataracts, and increased risk of heart disease. With the current record for the longest time in space being 438 days, there is no telling how sick a person will be after 2,190.