Hyperloop lets you travel on a resonant acoustic wave?

"Elon Musks final invention will be a time machine. It will only work once before exploding. Before entering it, Elon will turn around and tell us he has done his duty and given us many gifts, and now we must use those gifts to advance mankind. He hopes great things for us.

We beg for him to stay and aid us further. He smiles sadly, He looks at us with his tired but happy eyes, shakes his head, and steps into the machine. He returns to an early 21st century earth...and begins his work once again. As it has always been, as it always shall be."

As a surfer, let me volunteer that it's a bit like a highway onramp: you want to match speed exactly when the front arrives. Tiny adjustments in speed, pitch, yaw, roll, and center of gravity make the difference between making it, falling off the back, and getting eaten.

Mistiming your drop leads to bad outcomes that are directly proportional to the kinetic energy of the wave and are inversely proportional to the depth of the water. This is huge kinetic energy with a distance to the wall of, probably, microns. I want to see how this thing works, but oh, Nelly, what a wipe-out!

Not to be funny, but it seems like every other day has another "hyperloop uses acoustic waves" article. It's a good guess, but it doesn't even contain new speculation (another article went into detailed theorising about how cars would accelerate and decelerate).

Seriously, until we have a solid info, or even a new guess, can we lay off Hyperloop?

The hyperloop is feeling like the segway at the moment. I remember the hype before the reality of the segway and everyone being disappointed when they found out it was just a slightly altered scooter.

For someone who has taken nothing more than undergraduate physics as a requirement for my degree, can someone explain the benefits/risks of using an acoustic wave system over others? Has anyone previously looked at this sort of system for travel? If the wave were to be disrupted and these capsules come to a screeching halt, how fast of a deceleration are we talking about? Never more have I wanted to crack open my physics texts again.

And how will this affect the elephants?

> the tunnel would be opened up to the outside atmosphere. That would immediately ruin the resonance and all capsules should come to a screeching halt.

Correct me if I'm wrong, but my intuition is that this would also lead to quite a bad explosion. I mean, the amount of energy I imagine it would take to initiate a standing wave between LA and NY should be massive, (and certainly not a small amount to maintain it either, though far less than the initial amount if it truly stores the energy well). But if it is _storing_ this energy, then any rupture should release it quite... quickly. No?

A standing wave is not nothing.. it is a huge amount of pressure oscillating back and forth in an underground cavity. A controlled hole in the cavity wall could release it properly, but a crack in the side could effectively lead to rupture, couldn't it?

Another thing, if the air pressure inside the tunnel is indeed quite high, the train cars would also need to be pressurized. This leads to some other potential dangers.. not to mention the time to pressurize would be added to the total trip time.

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.

There's been a lot of speculation on the hyperloop without accounting the 'air-hockey table' comment from Elon. I personally thought it meant using the ground effect.

I can't figure out how the OP proposal differs from Charles Alexander's. Low frequency (long wavelength) waves travel around the tube at the speed of sound. By traveling at the same speed, and correctly choosing a point along the wavefront, one can take advantage of significantly reduced apparent drag. It's implicit in Alexander's suggestion that either (a) the total length of the loop is an integer multiple of the wavelength of the waves, so they are "resonant" in that sense, or (b) the envelope of the wave is much less than the length of the loop. (If neither (a) or (b) held, the wave could not be formed in the first place.)

So what distinction is OP making? That it's resonant, and so definitely (a) and not (b)? I think it would require a calculation of how fast the wave would disperse in the tube, which OP has not done.

I can't wait for Elon Musk to silence all the low self-esteem full-of-envy idiots talking shit about him and mentioning "vaporware" without even understanding how vaporware works! I bet $100 he'll have a prototype to showcase given the engineering power at his disposal.

How might one get on and off this thing at these speeds? Perhaps a 2nd loop near entry/exit points?

Whatever it ends up being, this is exciting!

If the solution involves a tunnel or tube from SF to LA then I fail to see how it can be as cheap as has been claimed. I suggest it's an accelerator that launches capsules ballistically, "skips" them to maintain velocity, and recaptures a good deal of energy on arrival.

Do you ever think that Elon has no plan, but he's just put this idea of a plan out there and let us crowd source a solution. That would be neat way to solve an 'impossible' problem.

6,437km/h (4,000mph) to zero is going to be one hell of a stop.

Like most titles that end with a question mark - "no". Why would you use some kind of acoustic wave system over tried and true maglev?

> it's not an evacuated tunnel

Really? I thought it was already established that the Hyperloop is a vactrain (http://en.wikipedia.org/wiki/Vactrain). Using small cars (say, six passengers) accomplishes the "leaves when you arrive" and putting solar panels on top of the tunnel accomplishes the storing energy part. I wonder what the alternative would be and what its advantages over a vactrain would be.

Thats clearly nothing to think of :P

I have a flight to LA tomorrow. Any chance this will be ready by tonight?