It's a visceral experience because you've got the noise, the vibration, the raw power of the rocket.
The centrifuge doesn't give you that experience.
And so when you're sat on the rocket, you're also fully aware of the whole launch day that's preceded that, the environment that you're being watched by family and friends.
And it's incredible, all the emotion as well as the level of professionalism you need to have to check the rocket and make sure everything's working well.
So nothing truly prepares you for launch day.
Among astronauts, it is a common and understandable observation that the rest of one's life can be laden with a certain anticlimactic quality.
After that, then what?
For this week's guest, the answer would appear to be why not go back?
British astronaut Tim Peake, who spent six months aboard the International Space Station from December 2015 to June 2010, 2016, hopes to return to space as part of the UK's first astronaut mission.
In the meantime, Tim is the author of the Tremendous the Human Story, part history of spaceflight, part memoir.
I'm Andrew Muller and I spoke to Tim Peake for the big Interview.
Tim Peake, welcome to the big interview.
Thank you very much.
Great to be here.
Well, first of all, we were thinking of doing this as a sort of reflection on what it is like to have been in space, but it turns out that that might not be the end of the story.
Yeah, well, I've always said never say never kept the doors open and lots is happening in the commercial space environment.
It's really exciting and it's kind of new era of space exploration.
So, yeah, there could be a potential future mission ahead.
So if all goes well, and we will talk about this in the ensuing half hour or so, your book does demonstrate that none of this stuff is easy, but if it is all as easy as it can possibly be, do you have a vague idea for a departure?
D no, not at all at the moment, but I would imagine it would be within the next couple of years because things do move fairly quickly now in the commercial space environment.