That looks like a more elaborate version of something I thought of as a kid, which was basically a vacuum tube going all around the world (one big torus if you will) with carts on super conductive magnets. I was thinking mainly of connecting Tokyo and New York and some place or other in Europe. Cart drives into the station, station gets sealed off and air pumped into it, then passengers leave and board, the doors get closed and the station sealed, then the thing speeds off at a gazillion miles per hour. Yay! Of course you'd have to start braking long before arrival, but the idea wasn't really about saving time (I could not possibly have anticipated how pampered and stupid grown ups are), it was mostly about saving energy, the idea of near zero friction just fascinated me. Though I was never sure if cooling the magnets and keeping the vacuum up wouldn't be more expensive than the energy saved.

But all that aside: bleh to passengers, think freight! If it's too complicated for people, because they won't use it if it takes as long as taking a plane... even though being a passenger on just one airplane ride is like riding a fat car for a whole year (give or take, it's nuts either way)... then automate it and use it for cargo. Especially since in that case and for a lot of products the vacuum wouldn't matter, the cargo could just ride in open carts and get picked up by robotic arms. Heck, you might even just throw it on while it's moving, and even use hooks to get cargo off without stopping the cart at all. This might seem too tricky... until you realize what marvels are going on in a bog standard HD these days, right? (though I remember a similar invention for passenger buses from MAD Magazine: something about spring-loaded seats haha)

of course it's in comic sans

I agree -- I don't think that any kind of tunnel or tube approach can be done more cheaply than HSR. And I venture to predict that if it is a tunnel or tube concept, it won't succeed in linking LA and SF.

That said, if we take Musk at something close to face value, it has a major advantage that the HSR doesn't: it would be faster than the air route. That would give it at least a fighting chance to draw extremely high ridership and make up for high costs with high revenue.

And if the idea is basically sound, but the implementation is impractical on the SF-LA corridor, then it could be put into use in some other intercity connection with more favorable terrain and lower land costs.

My only guess on this is max capacity. Theoretically if the tube were large enough you could run a few of these a day and carry thousands of people on each one. If you can get the energy consumed per passenger way down, then costs may decrease and a ticket could be much less expensive.

If you could travel hundreds of miles in a half hour, you might make a lot more trips. Changing the cost structure and timing dramatically would change the way people think about long distance travel from something you do once in a while to being as common as going across town for an afternoon.

Obviously this is all far-fetched given today's technology, but I'm just letting myself daydream.

Agreed -- seems like you'd have higher construction costs, higher energy requirements, and similar right-of-way concerns.

Enclosed tunnel: "air column" is a give-away.

This is essentially a vac-train, except instead of a vacuum, the air in the tube is propelled along with the pod.

There will be friction, but only between the air and the inside of the tube. I imagine there'll need to be some kind of "repeaters" to counter-act energy loss, but with so little loss, they could probably be solar-powered; which I think Elon alluded to.