Ad Astra is Brad Pitt’s hardest film

In two of his starring roles this year, Brad Pitt shows the full gamut of his range.

Quentin Tarantino's Once Upon A Time In Hollywood saw the 55-year-old US actor play stuntman Cliff Booth, who ekes out a living in 1960s Los Angeles.

Fast forward to sci-fi adventure Ad Astra, which opens here tomorrow, where he portrays Major Roy McBride, an astronaut who embarks on an odyssey to the far reaches of our solar system to track down his vanished father (Tommy Lee Jones).

Pitt also serves as a producer on the film through his company Plan B, which also produced director James Gray's The Lost City Of Z (2016).

At the Venice Film Festival world premiere of Ad Astra, Pitt explained what drew him to the project and opens up about the challenging but fulfilling journey he took with Gray.

What were your memories of first meeting Gray at the Sundance Film Festival in 1995?

I had called him up after seeing (his 1994 feature film debut) Little Odessa. We just became immediate friends. We always talked about doing something together. Ad Astra was the one that finally lined up for us.

Were you drawn at all to the idea of the mystery of this character's journey?

Definitely. Now, for example, with Quentin, it is okay; his dialogue is so specific and I know his vernacular, so I have a really good idea of where we are going to land.

But with this film, I didn't at all. These were big and very difficult ideas to get across in two hours, in a film format. I had no idea how we were going to get there. I am not sure James even knew, but it was worthy of the journey.

When we got to editing this film, I would call this the hardest film I have ever been a part of. That was surprising to me, but it was also joyful because I feel like if you think you know exactly how everything should be done, you are done.

Surprising how?

Just how delicate it was in the editing process. One line of voice-over, or a music cue, could so easily tip the cart over, and we would have to pick it back up and start back again. This was consistent through the whole film, it was really challenging in that way.

There are definite influences from Joseph Conrad's novel Heart Of Darkness, which became the (1979) movie Apocalypse Now. That had a famously challenging shoot, but the finished film is widely considered to be a masterpiece.

We had to keep reminding ourselves, they didn't have that thing figured out.

I mean, there are literally stories about how many times Martin Sheen had to redo the voice-over, and how they had to reach out to others that helped hone that voice-over. They didn't even know how to end it until then. We weren't sure how to end ours. There were definite parallels in the making of this movie.

At the same time, the protagonist's journey is quite different. Did that strike you?

In retrospect, I think we were originally heading towards that dark night of the soul, where our character has to go to the farthest reaches of our solar system to find himself utterly alone, to not have anyone else to rely on, or any TV to distract, or any drugs to escape with. So he is really left having to confront the self - with all of its grief, buried pain and regret.

Going back to those ideas about masculinity we have grown up with - that we must be strong at all times, that we must not show weakness, that we must be capable, and that we must not let anyone disrespect us, which is the one that always makes me laugh. Talk about a fool's errand.

In my life, I have come to believe that it is being open - for your kids, for your loved ones, your friends and yourself - that you have to look at. You have to be able to fully acknowledge yourself, know yourself. Or constantly trying to know yourself and being open about that with others.

You spent much of Once Upon A Time In Hollywood driving around the sun-kissed streets of Los Angeles. Is it fair to say that being dispatched into the dark of space, with so much zero gravity wire work, represented a slightly more complicated technical challenge?

Slightly. Doing the zero gravity stuff on Ad Astra was a bit like putting on a Peter Pan stage production.

You are strung up on wires and you are in tight, confined spaces, and it is not like you are just hanging, because only bits of your body are hanging. And you are being pulled in all sorts of uncomfortable areas, and yet you have to project the calm and relaxed state of zero gravity.

You do get used to that. Then you can get to the place where emotions can still come out and you are not just sitting there strained, trying to hold your skull up while blood is rushing to your head and you are feeling literal pressure.

Meanwhile, wearing the spacesuit was like putting on a garbage bag, and then putting a snowmobile suit over the top of it.

On every film we do, there is a relative degree of discomfort. With Cliff, every morning I had to put on the scar prosthetics. It comes with the territory. We have grown to expect that.