In the movie Gravity, Sandra Bullock is the sole survivor of her space shuttle colliding with a Russian satellite—experienced astronaut George Clooney has just sacrificed himself to get her to safety. But at that point, there are still 40 minutes left to the movie, so, inevitably, she’s not safe at all. Instead, her refuge at the International Space Station has caught on fire. Astrophysical inaccuracies aside, the scene captures how perilous fire could be in outer space. It’s a calamity NASA has spent decades working to avoid by making all of its technology as fire-resistant as possible. Despite that effort, fires in space could happen, and NASA knows that for long missions, like ones to Mars, astronauts need to be prepared to handle them. But explorers can’t prepare for something they don’t understand, so NASA is starting some fires—in space—to find out exactly how they work. Watch the video above to see the largest fire humans have ever (intentionally) lit in space, and learn what it could mean for astronauts who might one day find themselves facing an unintentional one.