I cannot speak to the technical issues (a very critical and very interesting take is here) but I wonder where the real gain is (there is a Musk pdf overview of the hyperloop here). You can already fly LA to San Francisco in about an hour. Is saving that time so important, noting that in the best case scenario the hyperloop still takes 35 minutes?
You might object that such a plane trip takes far more than an hour, all things considered. But a hyperloop trip also will involve getting to the station, parking, waiting for departure, and perhaps TSA security as well. What is supposed to be the net time gain, all things considered? It would be cheaper to let up on the TSA procedures a bit, and even if we don’t do that surely there is no “regulatory arbitrage” case per se for building a hyperloop (“the TSA won’t budge, so I have this new and easy-to-implement idea…”).
Flying is carbon-negative, but of course building and running a hyperloop would be too. In any case, it is hard to believe that a hyperloop is the marginally cost effective way to reduce carbon emissions, compared to say shutting down some more dirty coal or pricing traffic congestion.
How about putting working wireless, or maybe cable TV, into all LA to SF plane flights? That would make time in the plane a lot more like time on the couch and in essence lower the time cost of flying. We could even teach people to read books or let them keep their Kindles on during take-off, a rumored change which may even be in the works.
In other words, the whole Hyperloop thing seems to me like a publicity stunt. I’m still waiting on that 24-7 Kindle access thing.
The binding constraint for a lot of transport improvements is getting the land rights (can it all be on top of I-5? how much do pylons cost?) and overcoming local opposition. I say the hyperloop proposal only makes that harder.
When it comes to transportation at least, There is a Great Stagnation.
p.s. under the counterfactual where the thing is built, what would the price be? Here is some skepticism from Brad Plumer.