'A curveball all the time': How the CSA tests potential astronauts

Astronaut candidate Zen Mariani speaks to CTV's Your Morning Monday, March 13, 2017.

A finalist in the Canadian Space Agency's search for new astronauts says the testing process is a non-stop adrenaline rush of physical and psychological testing, in which they "throw you a curveball all the time."

Zen Mariani says it's been an "incredible experience" to make it to the shortlist of 32 candidates who are competing to be one of the two who will be selected for the job later this summer.

"They do such a good job with the testing," Mariani, who has a PhD in physics from the University of Toronto, told CTV's Your Morning on Monday. He says he's faced a variety of challenges, from the beep test (a common endurance exercise in high school gym class), to unexpected crisis situations, such as being told to escape from a submerged helicopter.

"They don't tell you what they're testing you on and you're behind a door," he said. Each time that door opens to a new test, Mariani says he gets pushed to his mental and physical limits. "They evaluate to see how you respond to those stressful situations," he said. "There's this continual adrenaline rush that you're going through, and it just doesn't stop."

Mariani says he's wanted to be an astronaut since his parents took him to see the film "Apollo 13" when he was a boy. "As soon as I saw that movie I was like, 'That looks awesome, I want to do that.'"

The Canadian Space Agency has narrowed its pool of candidates down to 32 from an original field of 3,772. The CSA is expected to whittle the numbers down to 20, before announcing its two selections in the summer.