So California is spending $70 billion on a high-speed rail network between Los Angeles and San Francisco. This trains on this network would travel at 200mph (4 hours) and trips would cost $50-100 each way. Elon Musk proposes covering this same route with a new system: 35 minutes travel time, $20 each way, with a project cost of $6-10 billion. A train, accelerated by electromagnetic linear motors (like a less-powerful railgun), which travels through a tube with a reduced air pressure (air is pumped out, but there's no vacuum requirement, which is hard to make work). This train, using a water-cooled compressor in it's nose, would be capable of flying through this tube at just under the speed of sound (685mph) by sucking in air and ejecting it through panels which act as the 'wheels' of this train, by creating a powerful air-bearing between the train and tunnel (like how air hockey works). The entire system is powered by electricity, which is supplied via solar panels on the tunnel, which is capable of creating enough power to power electric recharge stations along it's route (which would be following the CA Interstate 5 highway for the majority of the route). It's unlikely that Musk's system would go ahead due to politics, but seriously, he needs to develop a time machine or supersized mind eraser so that he can make everyone believe he was born in the US, so that he could become US President.