Mr. Musk on Monday harked back to the days of the late-1990s tech bubble — when no idea seemed too big or too expensive — by showing off plans for a project that seems the stuff of science fiction.
The first unanswered question among many for Mr. Musk’s ambitious vision is who exactly would build this 400-mile transportation system. Mr. Musk suggested someone else should do it. But if no one takes the baton, he might do it. Or not.
Beyond that, the details of who would pay for Hyperloop, how it would be built and how long it would take are also unclear. But Mr. Musk theorized that if he devoted all of his energy, he could have a prototype done within one to two years. He estimated the project would cost around $6 billion and tickets would cost $20 per trip.