A Hyperloop sounds to me like a marketed trademarked copyrighted patented implementation of a traditional Launch Loop aka Space Fountain. A wiki link:

http://en.wikipedia.org/wiki/Launch_loop

http://en.wikipedia.org/wiki/Space_fountain

You could buy a kids toy circa 2005 implementing a model of the design using what looks like a shoelace and a blacklight. My kids thought it was pretty cool.

So, take a magnetically controllable loop, like a wagon wheel tire. It'll collapse under its own weight it stood up. Turns out if you spin a rope ridiculously fast it inevitably turns into a circle and can support well over its own weight. Basically you build a linear induction motor to get dragged along and remove the clamps at the appropriate time. Think of how you can ride upside down in a roller coaster as long as you exceed critical speed (too slow and you fall out, whoops)

Compared to a space elevator its well within modern current day tech to build one. I donno if its economically within modern day ability.

Three major problems, if that dude splits at the wrong time its an unholy mess as it augers in, and there's something of a dynamic stability puzzle to stabilize movement and temperature, and finally you need a plan of sorts if the clamp or whatever you call it sticks and hauls the first stage back for another go of it.

One optional problem is to build a loop that stores energy by spinning a bit fast, faster than a vehicle re-entering for a second loop can handle nose first. That makes the "stuck clamp" hollywood disaster even worse. Of course a smart engineer would never do that... would they?

There's a fixation on SSTO, of course. However, aside from economic issues, you can make a real loop thats as worthless as you want, and any delta-v it gives for free to a launch vehicle is a net win. So make a "mere" 10 mile diameter one that only replaces the first stage of a launcher, thats cool. How about reducing the mass fraction for a "SSTO" from 95% to maybe 50%? That would still be cool, even if its not "SSTO".

If you can't mentally handle this rotating stuff, think of it like a really long aircraft carrier catapult... so long it can loop back on itself no problemo. And think of cablecars, although it'll probably be magnetic not literally clamping onto a cable, although that would be a charming steampunk aesthetic.