We don’t have personal jetpacks or hoverboards yet, but one piece of futuristic travel might be on its way. Later today, entrepreneur Elon Musk of Tesla motors fame will announce plans for a mass transit system he is calling the Hyperloop. Musk describes the mysterious Hyperloop as a “cross between Concorde, a rail gun and an air hockey table,” that will transport rider from one side of the U.S. to the other in about 45 minutes. So what is the hyperloop? Here’s one guess before the official announcement.