In space, how quickly does grape juice turn to wine?

Two California high school students hope to find out soon. Their experiment is one of 15 aboard a rocket scheduled to blast off early Saturday from Cape Canaveral, Fla., to the International Space Station. “We think it’s going to ferment faster,” said Max Holden, a ninth grader at Chaminade College Preparatory in West Hills, Calif.

But there is no guarantee that the seven-inch tube of yeast and grape juice will ever reach its destination.

The launching is a test flight of a spacecraft built by the Space Exploration Technologies Corporation, or SpaceX, of Hawthorne, Calif. The event is slightly historic: if all goes well, the ship will be the first operated by a private company, rather than the government, to supply the space station.

Erring on the side of caution, officials at NASA and SpaceX have stressed that the purpose of the mission is to shake out glitches. “I think there’s a significant chance the mission does not succeed,” said Elon Musk, chief executive of SpaceX.