[Aqueous]

Elon Musk said it was nearly impossible to get injured in his system. Which means that any aircraft travel is out, because all it takes is an engine failure to kill everyone on board.

The safety reason is a big reason why I'm going with the underground tubes between LA and SF.

[ronaldx]

Flight is still the safest form of transport (per passenger mile, it's hardly even close) e.g. http://news.bbc.co.uk/1/hi/uk/736582.stm

Engine failure doesn't kill people, because you can typically glide to a landing. Speculatively, if you got your glide ratio perfect and launched high enough, you might not need an engine to get between LA and SF.

[Aqueous]

Anything looks good next to cars :-)

But yeah, flight is comparatively one of the safest ways to travel. But, in principle, it is still quite risky. A lot has to go right for an aircraft to successfully take off, fly, and land. Air speed must be maintained, the engines must remain mechanically sound, landing gear must be operating correctly, hydraulics on the wing and tail flaps must be operating, the pilot must be competent and alert. Countless systems must be working correctly. Any one of these things going wrong can result in mass casualties. Statistically our standards of operation are so high that flight is effectively safer than the automobile or trains or even lightning, as the article points out. But 1 in 12 million is still far from the effective 100% safety that Musk is promising for hyperloop.

[Nogwater]

That would be one hell of a glide ratio. A little research on Wikipedia tells me that modern sailplanes get a glide ratio of something like 50:1. It's roughly 350 miles from LA to SF, so you're looking at launching from about 37,000 ft. This sounds doable, but I don't know if it really works like that. Can they keep the same glide ratio at that altitude? What about weather conditions? What about Elon's claim of 30 minutes for the trip?

[throwaway_yy2Di]

To be fair, if he's comparing to human-driven cars, every mode of transport is "nearly impossible" to get injured in. That clause doesn't really constrain anything.

[thomasjoulin]

I don't think it can be underground, since Musk said it would cost $6 billion to build. Also, the plan is to build something similar for east-west coast travel, and underground would be even less possible.

[softbuilder]

The other consideration aside from cost is that seismic activity, even minor, can skew a tunnel. (Edit: for deep tunnels, that is. I have no idea about tunnels right below the surface.) That's bad news at high speed. I've given the tunnel approach some thought.[1]

And I keep hearing people trying to apply Hyperloop to coast-to-coast travel, but I don't recall Elon every saying anything about that long of a distance. In fact I recall him specifically talking about "the right city pairs", which implies some kind of distance limit.

[1] http://www.youell.com/matt/writing/?p=1050

[dancryer]

In an interview, Elon said that the system could work underground but that it would be more cost effective above ground...

[eyesee]

I do wonder if there's something specific about LA to SF that enables the low low cost Elon's suggesting. Like the fact that they share a coastline with the Pacific Ocean.

The $6 billion cost seems too good to be true for any transportation system that would require significant land acquisition. California is set to spend some $60 billion on a train between these cities, and most of that cost is for right-of-way.

[Justsignedup]

the time to travel between ny and sf can be the time it takes me to come to work. they'd make that 6 billion back in a month.

[larrydag]

The construction cost alone for building a tunnel underground would be in the several billion dollars. I don't think it will be underground. At least not most of it.

[prawn]

"He believes it could work either below or above ground." (From Wikipedia.)