3 ms·

There are also very real technical questions to be considered with holding a vacuum over that much pipe, especially when there's gonna be some seismic activity,

There are also very real technical questions to be considered with holding a vacuum over that much pipe, especially when there's gonna be some seismic activity, potential for sabotage etc. I'm not sure that it really is economically viable unless there's some kind of incredibly durable and flexible material to be had which is as easy to use as concrete, about as cheap as concrete, but basically magical spiderwebs.

kbenson 9y ago
It's not a vacuum, it's a partial vacuum (1 millibar). Apparently that's supposed to make it much easier to achieve with pumps, even with leaks.
- QAPereo 9y ago
  For it to be enough of the vacuum to yield real benefits in terms of The fluid dynamics of the air of the tunnel, it needs to be hard enough to be hard to achieve as in this case. It is easier to achieve than the kind of vacuum NASA might want to draw to test devices, or that somebody with a Watt balance might need, but honestly that only goes to show how horrendously difficult it is to pull that kind of vacuum
  - kbenson 9y ago
    There are plenty of breakdowns of the specific numbers that were given in the proposal. If you know enough to contradict one of those assessments or have enough knowledge of the engineering and current technology required to assess the proposal as a whole, feel free to submit your own numbers or point to the assessment you believe best covers the reality of the situation. Otherwise, definitive statements about small portions of a rather large and complicated proposal that don't provide evidence for their assertions aren't really worth reading. Sorry if that comes across as harsh (it's less directed at you, and more towards the situation as a whole), but this topic is so fraught with people making assertions based on rumors and assumptions rather than the actual data presented that there's a real problem wading through the misinformed to get to the useful information.
    - QAPereo 9y ago
      If you have those numbers to share, great, otherwise...
      - kbenson 9y ago
        The original proposal is available.[1] It includes enough numbers to make estimates of the physics involved. If you want to see what's essentially two youtubers arguing over the physics involved, check this[2] out. It gets a little petty by the end, but there is copious physics and math demonstrated, which you can assess yourself (along with whether the assumptions they make are valid). They do, specifically, go over what would be required to achieve the level of partial vacuum specified, as well as what would be required to safely achieve controlled rapid pressurization in an emergency. Or you can do a little googling. There's plenty of people that have jumped in with an assessment, and just about as many that have come after to refute some or all of their work. 1: http://www.spacex.com/sites/spacex/files/hyperloop_alpha.pdf http://www.spacex.com/sites/spacex/files/hyperloop_alpha.pdf 2: https://www.youtube.com/playlist?list=PLSPi1JFx4_-Gz0Fm0qq2KUz4c22UbZCco https://www.youtube.com/playlist?list=PLSPi1JFx4_-Gz0Fm0qq2K...
TallGuyShort 9y ago
I was wondering if there were updates about this myself. There's been lots of work talked about researching the fluid / heat & weight dynamics, but very little about maintaining the vacuum - which seems to me a more fundamental problem here...
- simias 9y ago
  I'm also interested to know what's the plan in case of a brutal rupture of the tunnel. A wall of air rushing through the pipe to meet a car traveling at supersonic speed doesn't sound very pleasant. Maybe they just plan to make the pipe sturdy enough that it wouldn't be a practical concern?
  - QAPereo 9y ago
    Thicker pipe = $$$

kbenson 9y ago

It's not a vacuum, it's a partial vacuum (1 millibar). Apparently that's supposed to make it much easier to achieve with pumps, even with leaks.

QAPereo 9y ago
For it to be enough of the vacuum to yield real benefits in terms of The fluid dynamics of the air of the tunnel, it needs to be hard enough to be hard to achieve as in this case. It is easier to achieve than the kind of vacuum NASA might want to draw to test devices, or that somebody with a Watt balance might need, but honestly that only goes to show how horrendously difficult it is to pull that kind of vacuum
- kbenson 9y ago
  There are plenty of breakdowns of the specific numbers that were given in the proposal. If you know enough to contradict one of those assessments or have enough knowledge of the engineering and current technology required to assess the proposal as a whole, feel free to submit your own numbers or point to the assessment you believe best covers the reality of the situation. Otherwise, definitive statements about small portions of a rather large and complicated proposal that don't provide evidence for their assertions aren't really worth reading. Sorry if that comes across as harsh (it's less directed at you, and more towards the situation as a whole), but this topic is so fraught with people making assertions based on rumors and assumptions rather than the actual data presented that there's a real problem wading through the misinformed to get to the useful information.
  - QAPereo 9y ago
    If you have those numbers to share, great, otherwise...
    - kbenson 9y ago
      The original proposal is available.[1] It includes enough numbers to make estimates of the physics involved. If you want to see what's essentially two youtubers arguing over the physics involved, check this[2] out. It gets a little petty by the end, but there is copious physics and math demonstrated, which you can assess yourself (along with whether the assumptions they make are valid). They do, specifically, go over what would be required to achieve the level of partial vacuum specified, as well as what would be required to safely achieve controlled rapid pressurization in an emergency. Or you can do a little googling. There's plenty of people that have jumped in with an assessment, and just about as many that have come after to refute some or all of their work. 1: http://www.spacex.com/sites/spacex/files/hyperloop_alpha.pdf http://www.spacex.com/sites/spacex/files/hyperloop_alpha.pdf 2: https://www.youtube.com/playlist?list=PLSPi1JFx4_-Gz0Fm0qq2KUz4c22UbZCco https://www.youtube.com/playlist?list=PLSPi1JFx4_-Gz0Fm0qq2K...

TallGuyShort 9y ago

I was wondering if there were updates about this myself. There's been lots of work talked about researching the fluid / heat & weight dynamics, but very little about maintaining the vacuum - which seems to me a more fundamental problem here...

simias 9y ago
I'm also interested to know what's the plan in case of a brutal rupture of the tunnel. A wall of air rushing through the pipe to meet a car traveling at supersonic speed doesn't sound very pleasant. Maybe they just plan to make the pipe sturdy enough that it wouldn't be a practical concern?
- QAPereo 9y ago
  Thicker pipe = $$$