The physical tests one has to go through before being allowed up in space are "the easiest and most trivial part of any astronaut selection".
Take it from former astronaut and commander of the International Space Station (ISS) Chris Hadfield - a man who has dedicated more than 30 years of his life to space research and logged more than 4,000 hours in space.
But most people would probably remember the moustachioed 58-year-old Canadian as the astronaut who performed a cover of David Bowie's Space Oddity while floating in space. The video, which he posted on YouTube during his final ISS mission in 2013, was shared in the wake of the music icon's death and has since garnered more than 37 million views.
Now, Mr Hadfield is putting his experience to use on the BBC show, Astronauts: Toughest Job In The Universe, which puts 12 participants through the rigorous process that space agencies use to select potential astronaut candidates.
He is no stranger to the process, having been involved in several astronaut selections for Nasa (National Aeronautics and Space Administration) and Canadian Space Agency.
He is joined on the show by industry experts, namely anaesthetist and trauma doctor Kevin Fong and space psychologist and director of the Centre for Space Medicine at University College London Iya Whiteley.
The candidates - of whom there is an even split of six men and six women - include a secondary school science teacher, a Royal Air Force pilot and a nuclear engineer.
Filming took place over 45 days in England, Wales, Germany, Sweden and the United States, where there are various space agency facilities.
"The fact that we were putting all the astronaut candidates through various tests and they were getting eliminated as we went, made it quite intense the whole way," he says.
1 Where did the idea for the show come from?
When I started talking to the BBC about the show a few years ago, the real objective for us was to let people see what an astronaut selection is like and what it entails, from the point of view of the space agency and the astronaut candidate.
I wanted it to be a real insight for the viewer, so he would ask, "Hey, is that something that I could do?".
In Nasa's last selection, 18,300 people applied for 12 positions. The proportions here were about the same - thousands of people from across the United Kingdom applied.
2 Is the show like a reality TV series?
Firstly, (the tests) were representative of what astronauts do and, secondly, wherever possible, identical to the type of testing we do in real space agency astronaut selections.
Just like in any of the space agency selections, as it goes on - either for medical reasons, skills, demonstrated capabilities or judgment - people get eliminated.
It's not reality TV, it's reality. That's the big difference. The people that applied were so competent and qualified that it made it very difficult.
3 What are some of the misconceptions about what it takes to be an astronaut?
Most people have a misunderstanding of what is involved in being trusted to fly a spaceship.
You need to be physically healthy and in reasonable shape, but tests are not just physical.
We have leadership tests where we put people in a stressful situation where unexpected things happen.
We also put them in very realistic space-type situations where they have to operate a complex piece of machinery they've never seen before to do a space task. There are mental tasks, acuity tests, memory tests.
4 Memory tests seem to figure frequently in space cadet selection. What was one of the biggest mental challenges you faced in your career?
When you get to orbit, you're essentially alone, with just you and your crew, so there's an enormous amount of things you need to learn and understand and then accurately remember.
For me, it was learning the most complicated machine that we've ever built, which was the space shuttle.
That task of learning something so deeply and completely and then flying it only once, but also having to remember everything - that was one of the most difficult things for me.
That's part of the reason we take candidates who have advanced technical university degrees because we test them really heavily on their memory.
5 What else do people frequently get wrong about training to become an astronaut?
With something like the "vomit comet" (a specially fitted aircraft that provides brief near-weightless environments for training astronauts), people get it all backwards.
It's not just about going for a ride. It's just a way to momentarily simulate weightlessness - like being underwater where we use the buoyancy to simulate weightlessness - and then you use that for a purpose. That might be evaluating a piece of space hardware or performing a particular task and to see if it can be done properly in weightlessness, so that when we get to orbit, hopefully, we can do it right.
6 When you were an astronaut just starting out with the Canadian Space Agency in 1992, was there anything that tripped you up?
When I showed up as an astronaut, we had not been cooperating with the Soviet Union.
But at that point, it was falling apart to what was becoming Russia and, within a few years, we were cooperating very heavily.
Suddenly, I needed to speak Russian, so I started studying it.
Not only that, but I also went on to become a pilot of a Russian spaceship. I helped to build the Russian space station and had Russian crew members who worked for me.
How do you test somebody to have that type of ability or raw capability?
I didn't know that on the day I got hired that I'd to learn to speak (the language) well enough to be the commander of a Russian spaceship.
7 What are you proudest of in your 35-year career?
When I was born in 1959, no one had ever flown in space, so space flight is younger than I am.
I was lucky enough to be in the Canadian space programme in the early stages and almost everything I did in space was a first for Canada, including becoming the first fully qualified space shuttle astronaut and the first Canadian to command the International Space Station.
All of those things were important and difficult for me, but they opened the door for other Canadians in the future. Our new astronauts have so many more opportunities available to them.
8 How would you like to be remembered?
As someone who helped open the doors to exploring the universe.
As we go from early exploration to permanently living on the space station, like we have for the last 17 years, to starting to build a permanent base on the moon and further, I hope I'm remembered as a person who worked his entire life to build and contribute to the foundations that have allowed all of that to happen.
• The Asia premiere of Astronauts: Toughest Job In The Universe airs on BBC Earth (StarHub Channel 407) next Monday at 10.30pm. It is available on BBC Player as catch-up.