Hyperloop lets you travel on a resonant acoustic wave? • Hacker News Board

Re: Hyperloop lets you travel on a resonant acoustic wave?

#91

Post by andrewcooke » Mon, Jul 29, 2013, 2:28 PM UTC

jessriedel wrote: post #81

andrewcooke wrote: post #75

Earlier quoted context omitted.

it's slightly less wrong, as far as i can see - http://www.acooke.org/cute/HyperloopW0.html

I read your post, but I don't understand why the first link can't work. Is there a problem with a wave propagating along the tube with essentially infinite envelope? Here's a nice animation: http://www.acoustics.org/press/151st/WaveVectorDemosmall.gif In other words: decompose the standing wave into its forward and backward components and just keep the forward one. This is not the same thing as the air having a net v…

you may be right; perhaps i have only remembered solutions with boundary conditions that would not allow such a solution. i will try to think things through again and perhaps do the maths. thanks.

Re: Hyperloop lets you travel on a resonant acoustic wave?

#92

Post by ethanbond » Mon, Jul 29, 2013, 4:45 PM UTC

radarsat1 wrote: post #88

> 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 eith…

It doesn't need to be a standing wave, it doesn't need to be from LA - NY (it only needs to be the length of the train), and it doesn't need to be in an enclosed tube.

Re: Hyperloop lets you travel on a resonant acoustic wave?

#93

Post by ethanbond » Mon, Jul 29, 2013, 4:47 PM UTC

jboydyhacker wrote: post #26

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

Just like a normal train would - you route off the main track. As far as actually stopping it, it could just be a "rail gun in reverse" which would allow it to regain a huge portion of its energy upon deceleration.