As the recent Virgin Galactic incident highlighted, we're in the tentative stage of space exploration, but Sir Richard Branson and his team remain focused on opening up a frontier that's so far remained tantalisingly out of reach.

For director Christopher Nolan, the subject matter represents the ultimate human experience - and he's delved into that world for his new sci-fi spectacle Interstellar.

Boasting an array of Oscar winners, including Anne Hathaway and Michael Caine, and awe-inspiring visuals, the film travels beyond this galaxy and out into the vast unknown.

"There was only one way to go and that was up... into space and in weight," laughs the movie's lead Matthew McConaughey, who's regained the weight he shed to play an Aids victim in Dallas Buyers Club, a role that earned him an Oscar earlier this year.

"Dallas was a very small, independent film that we shot very quickly - it was very earth-bound. This was much larger," says the 45-year-old Texan. "The shoot went on for five months, but when you're acting in a Chris Nolan film, it feels just as intimate, raw and natural as an independent film. I don't think any of the actors felt overwhelmed by the massive scale of the set pieces."

Set in the near future, the film depicts a time when an agricultural crisis has brought the world to its knees and a team of explorers are tasked with a mission to journey into the universe to find a new home for humankind.

"What is amazing to me is that while the excitement of the story lies in its scope, one of my favourite things about Chris is the heartbeat of humanity he gives his films," adds McConaughey. "No one handles the sheer mass and scale of a world like he does, because it always comes off as something personal."

Nolan, whose movies include the recent Batman franchise and the mind-boggling Inception, only had McConaughey in mind to play Cooper. "He embodies everything we were looking for; the spirit of adventure, a cowboy-like swagger, and the warmth of somebody who's involved with his family first and foremost," says the film-maker.

McConaughey would describe Cooper, a former test pilot and engineer, as "a dreamer and a man out of time".

"He's not supposed to be a farmer but in Interstellar, the world needs farmers, not pilots," explains the father-of-three. "Life has become about growing food and having clean water. We don't need any explorers, we don't need any astronauts, we don't need any bright ideas. Cooper's trying his best to live in this world, and hold things together for his children."

While he and his family work on the homestead, a small group of scientists are sealed off in an underground bunker and gambling their lives on the prospect that somewhere in the universe is a planet that could sustain the human race.

They've salvaged the best available technology from the ruins of the space programme to build three ships, but the one thing they're lacking is an experienced pilot. "Suddenly the dream that Cooper's been chasing all his life is knocking on his door. And it's not just the chance to be a pilot again, but to lead the most important mission of all time," says McConaughey. "The consequence of that opportunity is having to leave his two kids behind though, and what no one can tell him is how long he'll be gone."

Unlike his character, McConaughey didn't have to be parted from his wife Camila and their three young children, Levi, Vida and Livingston for the duration of the shoot. "I was fortunate I had my family with me in Calgary [where Cooper's homestead scenes were shot.]

"I remember the greatest way for me to go to set each day was saying bye to my kids and at the end of the day coming back to them and having that immediacy. Not a phone call. Not 'I'll see you in a few weeks.'"

The Magic Mike actor credits fatherhood with restoring a sense of wonder. "I'm a very logical guy and very early on, kids think logic is a load of baloney. There's no end to any story, it doesn't matter about logic. It reminded me that as we get older, we take some things for granted, but we should travel down the same path and see things [as if it's] for the first time," muses McConaughey whose forty plus films have grossed more than 1billion US dollars since his film debut in the cult classic Dazed And Confused.

One of the perks of his job is travelling the world in the name of work. "That's one of my favourite things in 22 years of doing this," he admits.

Interstellar was no exception, as the entire cast and crew upped sticks to Iceland to shoot scenes for the water and ice planets. Fortunately for McConaughey, he was kept warm and cosy in his spacesuit. "I remember sweating," he laughs. "The crew were pretty jealous!"

Not so great were the crampons, a traction device that's supposed to ease walking on snow, as the actor found the reverse to be true. "Those were a trick and I fell a couple of times."

In the midst of filming on the glacier, production had to batten down in their hotel when a powerful storm blew through the region, with wind so intense, it ripped the asphalt from the streets.

"It was a hairy day," recalls McConaughey. "The wind got up to 50mph and the helicopters had to be grounded, but Iceland was epically beautiful."

Now he's just keen for the film to open and for audiences to witness the sheer scope of Nolan's vision.

"He has an original take on everything and works by his instincts completely. I believe he's constantly letting his reach exceed his grasp. And when you see this film, you'll know it's true, because it's by far the most ambitious film he's ever directed."

EXTRA TIME - BEHIND THE SCENES

:: Christopher Nolan co-wrote the script with his brother Jonathan, but before they honed the script, he tasked his long-term collaborator, the composer Hans Zimmer, with writing a piece of music to reflect the relationship between father and child.

:: Theoretical physicist Kip Thorne acted as executive producer on the film and tested each narrative idea to ensure it would hold up to scientific scrutiny.

:: Six months before filming began, 500 acres of corn were sown for Cooper's farmland, so it had time to achieve its full height

:: The ice planet was filmed on the Vatnajokull glacier in Iceland, which had fallen in the path of volcanic eruptions and turned grey. The water planet was shot in the country's seemingly endless Brunasandur lagoon.

:: A team of highly skilled artists were employed to create the 50ft Lander and 46ft Ranger spacecraft. Each weighing more than 10,000lbs, they were shipped to Iceland and loaded onto trucks, before being reassembled in giant tents on location.

:: Interstellar is released on Friday, November 7