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Comment by minikomi | Hacker News Reader

Interesting.. What if if gets shot one direction, presurizing something, which it uses to shoot back the other direction

   waiting for passenger
     SF  [||| <> - - - - - - - - - - - - - - -  ] LA
     pressurized     -->  pretty spaced out "stuff"  
                      
     SF [-| - |- |-  |- <>-| - |- |- -| - |- |- ] LA
                            in transit..

     SF [ - - - - - - - - - - - - - - -  <> ||| ] LA
                                    <-   presurized for return

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Just like everything else in life the system would be subject to the laws of thermodynamics. The act of pressurising air would heat it up, and heat loss would mean that it wouldn't be fully reversible.

I suspect that a fully evacuated system using magnetic propulsion and energy recovery would be more efficient - the turbulent nature of air and the low-quality nature of heat energy would probably work against you to make a pneumatic spring fairly inefficient.

I don't think there's much doubt that an evacuated tube would be very efficient. Not only that, but you could go much faster. Jacques has rejected that hypothesis for other reasons.

"Jacques has rejected that hypothesis for other reasons."

Specifically, due to a specific statement that it is not an evacuated tube.

Well, yes, but he also supplied some arguments why his idea might be better which is what I was referring to.

sounds interesting,but this wont fit well with "it leaves when you arrive".

I always imagined Hyperloop as carriages pushed by a plasma armature, in a rail gun loop. just like a plasma-rail gun.

It's a "loop", so it won't be a single tube, but a torus ("donut"), probably stretched.

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