The sun is dying, and with it, all of humanity. As a last gasp, earthlings send a crew of astronauts on a mission to reignite it.

With the new sci-fi film Sunshine, Danny Boyle advances his genre-tweaking career, which also includes the mordant Shallow Grave, the drug-culture classic Trainspotting and the socio-zombie mashup 28 Days Later. Sunshine, which stars Cillian Murphy, Michelle Yeoh, Rose Byrne and Chris Evans, opens on July 20.

Wired News spoke with Boyle about making space convincing, his ride on the "vomit comet" and how Star Wars killed serious science fiction.

Wired News: Is it true Sunshine was inspired by an article in a scientific journal?

Danny Boyle: (Screenwriter) Alex Garland's a nut for the journals. He sent me a first draft with this amazing high-concept idea: a trip to save the sun. As far as we can find, there's never been a film about the sun, yet it's the single most important thing you could jeopardize.

WN: It's become rare for real science to intrude on sci-fi cinema.

Boyle: Hard-core sci-fi has gone out of fashion, hasn't it? There was a strong strain of it into the '70s that tried to depict space realistically, but it's been replaced. Alien, one of the great masterpieces, was quickly followed by Star Wars. And Star Wars, of course, led everyone to fantasy sci-fi, that playground where anything goes. You can imagine any creature, on any planet. And they all talk English.

WN: What did you do to keep it real?

Boyle: We tried to be strict. At the end of the film, there's obviously no way a man could reach out his arm and touch the sun. But the beginning of the film is absolutely based in as rigid a realism as we could do. We consulted NASA about it, and had scientific advisors with us the whole time.

WN: It's just a movie, though, so your storytelling must have collided with the hard science.

Boyle: I loved doing all the science research but I have to be honest: My brain doesn't really do maths. To really do the physics, you need to do the maths, because everything is explicable. You can't encompass it in your brain on a visual level without doing the equations. Ultimately, I had to be loyal to the story. I had no loyalty to the physics. I'm a sham storyteller and quite proud of that. You sacrifice what you need to for the story.

WN: What Hollywood clichés did you try to avoid?

Boyle: We resisted the studio's attempts to turn this into a disaster movie, where you keep cutting back to Earth. Our principle was always to trap the audience in the ship with the astronauts, and keep them there in this claustrophobic space. We didn't want it to be objective, with you watching it coolly. We wanted you to feel the journey pass through you. We spent a lot of our time and our resources to try and make that happen, to take people to the surface of the sun.

WN: Did you worry that it would be a letdown for the audience once they got there? You don't want the sun to look like a light bulb covered in red crepe paper.

Boyle: (Laughs) On a technical level, the sun was everything. You've got to make it plausible on a sci-fi level. And beyond that, whatever you think of the story or the characters, the journey needs to be visceral. You need to take the audience on the journey with you.

I was dead honest with (visual effects supervisor Tom Wood). I told him I don't understand how CGI works. I described what I wanted, and he had to match it or better it. It was as simple as that. Sometimes it would come back and I couldn't believe what I was seeing. It was extraordinary.

WN: How did you convince the actors they were on a spaceship instead of on a soundstage?

Boyle: One of my obsessions was that I didn't want this to be a green-screen or blue-screen film, to have the actors looking at a blank screen that would be replaced months later by some astonishing effect that they weren't aware of and therefore couldn't react to. I wanted to make sure that everyone understood what they were looking at, that they'd see something that would allow them to act accordingly.

So we spent a lot of money on stuff that was never going to be seen, creating live effects on the stages for the actors to look at. People said, "You are just wasting money. It'll all get replaced by CG." I said, "I know it's going to be replaced. It's not there because I don't know what I'm doing. It's there to make the actors experience it." My fear with CG is that actors look bored or they overact, that they can't find where to pitch it. I think our approach makes the CG feel organic to the film, instead of a late arrival hitched on.

In the end, all realism is based on the question: "Do you believe that actor? Do you believe that moment?" It's simple as that for me, whether you are dealing with drug addicts in Trainspotting or an incredibly sophisticated mission to the stars. It's the same benchmark, really: "Do you believe?"

WN: I know you talked to astronauts and researched real-world space programs, in part to give the cast the sense of vulnerability of astronauts have out in space.

Boyle: It's just unbelievable. (I read) one bit about the lunar landing module. Neil Armstrong said you could put your fist through it. If you just punched it hard or leant on it wrong, your hand would go through like a biscuit tin. Two hundred thousand miles from earth in a biscuit tin (laughs)!

WN: How did those experiences affect the actors?

Boyle: It added to the group dynamic. It's almost like a siege mentality. They are so fragile and vulnerable – it just helps psychologically to get the actors in the zone. That's what you do this work for, all this research and getting them to talk to real astronauts. Hopefully some of it rubs off.

WN: And you put them in zero gravity simulators.

Boyle: Yeah, we did some weightlessness. I did the vomit comet, where you get 30 seconds of weightlessness. If you ever have three grand to spare, I can't think of a better way to spend it. It absolutely changes you.

WN: The film covers some of the same thematic material as 2001: A Space Odyssey and Solaris, films you've described as masterpieces. Were you worried about following in those footsteps?

Boyle: There are certain things you bump into and can't avoid. You can't be in a state of denial. You have to acknowledge that you'll be following their footsteps, because it's quite a narrow corridor, really.

WN: What is it about those films that makes them masterpieces?

Boyle: They stretch the mind. They use space to stretch the mind to what's possible. What happens to you out there, in this endless space that's also claustrophobic? Your body can't step outside the steel tube because everything is poised to destroy you, but your mind can. It can bend out there.

WN: Will you ever do another sci-fi film?

Boyle: No! I When I was making Sunshine, it suddenly struck me: No director has ever gone back into space, with the exception of franchise directors. If you look at the record, you'll find that's true. I now know why.