Countries in Europe and Asia are filled with high-speed bullet trains, bringing passengers from Paris to London or Tokyo to Kyoto within 2.5 hours. But hyperloops theoretically could bring passengers from Los Angeles to San Francisco in 45 minutes. The hyperloop concept gained popularity in 2013 when Elon Musk wrote his Hyperloop Alpha paper, but the US still doesn't have one. So what's the holdup? It all comes down to technology, money, and construction. Virgin Hyperloop is on its way to developing the first hyperloop, testing a 107-mph run in November using maglev technology.