
SpaceX is livestreaming a hyperloop pod competition - MilnerRoute
https://tech.slashdot.org/story/17/01/29/2336244/spacex-is-livestreaming-a-hyperloop-pod-competition
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ChuckMcM
So really the hyperloop is just the highway system Elon expects to have on
Mars :-)

More seriously I find engineering challenges like this are the single best way
to motivate students, it gives them a real problem (no spherical cows or
massless pulleys) that tests their ability to create engineering solutions.

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aaronblohowiak
And his idea to have the drilling solution for cities is really because you'd
need to drill a lot on mars for habitats. You need 5 meters of Martian soil to
provide equivalent protection to earth atmosphere

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mulmen
Wow! Do you have a source? I'd love to know more about that. When you say
protection do you mean from radiation or do you mean to trap an earth-like
atmosphere in the rock?

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NamTaf
Radiation, I believe. Mars has barely enough atmosphere to protect from the
various things Earth's atmosphere protects us from, so we have to go
underground (or come up with some hefty structure) to not get gradually
scorched.

Also, my guess would be that 5m of rock probably isn't good enough at trapping
gases.

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baking
It is Earth's magnetic field that primarily protects us from solar flares.

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NamTaf
Yes, I was talking about other radiation, eg: UV. That said, 5m of rock is way
overkill for UV rays since they're blocked by opaque objects. It would be
perhaps more helpful in its ability to weather small meteor impacts that
routinely burn up in Earth's atmosphere. I understand that Earth's magnetic
field is the primary defence against charged particles (eg: solar flares), but
in saying that it's necessary to note that Mars' magnetic field is
substantially less than Earth's, so rock would help there too.

What I was trying to say in a round-about way is that it's not the atmosphere
option that the parent postulated, because 5m of rock wouldn't, in my mind,
produce enough of a secure boundary to contain an atmosphere in it. I could be
wrong there, though - maybe it is secure enough in the right sediment!

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baking
Sorry, my point was that even if Mars had a thick atmosphere (after
terraforming) you would still need underground bunkers for protection from
solar flares and perhaps habitation. A thick roof is insufficient because the
charged particles travel in a corkscrew path so you need thick shields on all
sides. This is because it lacks a magnetic field and a large enough artificial
one is impractical.

EDIT: Also at last years trial, Musk said that a hyperloop design on Mars
might not need tubes at all since the atmosphere is thin enough.

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NamTaf
Right, I misunderstood what you were saying.

Also, yes, the hyperloop isn't directly relevant to Mars for that very reason
- the atmosphere is annoyingly thin from a reentry point of view (enough that
you have to protect against heating from it, but not enough that it can be
used to bleed off all that velocity from orbit) but that means it's not really
an issue if you want to push something fast through it. That said, I wasn't
making any comment about the hyperloop itself rather the parent post's
comments about why digging tunnels on Mars might be necessary.

Not sure why my posts attracted downvotes though (not necessarily from you),
but whatever.

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djrogers
Link to the SpaceX site one star of slashdot:

[http://www.spacex.com/hyperloop](http://www.spacex.com/hyperloop)

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shade23
Could someone replace the HN link to this? The current link just redirects to
a slashdot forum page.

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soheil
Seems like there should be a separate competition for designing the tube. For
example why should the radius of the tube be what it is, why have a center
rail instead of two rails or side tracks, should the tube have some sort of
inner coating? What if it should be a double tube, a tube within a tube, for
sound/temperature isolation and to reduce vibrations, and to reduce the risk
of depressurization due to outside impact kinda like a double-haul oil tanker?
Can it be made out of glass (that'd be kinda cool to look at/out of)? How
close to vacuum the pressure and thick the walls of the tube should be?

Can someone double check my work here: In the webcast they mentioned it will
take 30mins to depressurize the tube. The length of the tube is 1mi. For
example from LA to SF is roughly 400 miles if the final pump is twice stronger
it'll take 6000mins or 4 days to depressurize, I'm assuming they will only
need to do this once and have gates to maintain the main tube's pressure near
areas of loading/unloading.

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the8472
a longer tunnel would likely have more pumps along the track. I don't think
you should extrapolate from this small-scale model.

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smbullet
It definitely doesn't scale linearly. They had a section of the tube only
several meters long for vacuum testing pods and that took 15 minutes to
depressurize. It's likely bigger/more pumps would be used.

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annerajb
Woudn't the need for depressuration be removed if using airlock since you only
have to depressurize the airlock volume?

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vidarh
To some extent, but part of the reason for having pumps is that it removes the
need to make the tube fully airtight - the idea being that it's likely to be
cheaper to build a tube that is largely airtight and use pumps to deal with
leaks than to build one that can keep a vacuum over time.

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firefoxd
I passed there yesterday on my way home. It was surprising to see the long 1
mile tube literally on the closed side walk.

It was past 6 and I shared an uber ride with one of the contestant. He was
very secretive of his work but was excited about it.

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gizmo
This is really cool. For people just tuning in: this is a test of pods in a
vacuum tube travelling by their own power. Designed by students. A pod just
got 94km/hr top speed.

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flukus
> A pod just got 94km/hr top speed.

Why is that impressive?

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AtheistOfFail
decent aerodynamics?

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nothrabannosir
Isn't it a vacuum?

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rmccue
It's specifically _not_ a vacuum, but rather a low pressure system.

> Just as aircraft climb to high altitudes to travel through less dense air,
> Hyperloop encloses the capsules in a reduced pressure tube. The pressure of
> air in Hyperloop is about 1/6 the pressure of the atmosphere on Mars. This
> is an operating pressure of 100 Pascals, which reduces the drag force of the
> air by 1,000 times relative to sea level conditions and would be equivalent
> to flying above 150,000 feet altitude. A hard vacuum is avoided as vacuums
> are expensive and difficult to maintain compared with low pressure
> solutions.

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stephen_g
You're using faulty definitions there. Even outer space is not a 'true'
vacuum. Any pressure lower than atmospheric pressure is considered a partial
vacuum.

100 Pascals in a lab would be considered a 'medium' vacuum. And in a tube the
size of an actual full-size hyperloop, even that will probably be _extremely_
difficult and expensive to achieve.

I think the hyperloop will end up being technologically unviable mostly
because of the cost and the limitations of technology (like the expansion
joints that will be required on a decently long track), but I hope I'm wrong
on that. It may lead to new innovations which will be good.

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rmccue
You're right, I'm using vacuum as a layman's term, and shorthand for "hard
vacuum" as mentioned in the paper. [0] The paper refers to the Hyperloop
system as a "a low pressure (vs. almost no pressure) system".

[0]:
[http://www.spacex.com/sites/spacex/files/hyperloop_alpha.pdf](http://www.spacex.com/sites/spacex/files/hyperloop_alpha.pdf)
(p3)

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imaginenore
If you haven't seen the technical criticisms of Hyperloop, Thunderf00t has an
interesting video:

[https://www.youtube.com/watch?v=RNFesa01llk](https://www.youtube.com/watch?v=RNFesa01llk)

I haven't seen most of the issues he raises addressed.

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zenir
It's a partial vacuum not a full vacuum. Stopped watching at that point..

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e2e8
I don't think that objection, by itself, invalidates the the video author's
criticisms. According to Wikipedia, the hyperloop is intended to have a
pressure of 100 Pa or 0.1 % of atmospheric pressure[1]. That is not much
different from a prefect vacuum for the purposes of an approximate engineering
calculation.

[1]
[https://en.wikipedia.org/wiki/Hyperloop](https://en.wikipedia.org/wiki/Hyperloop)

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Animats
No, the air in the tube matters, at least in Musk's original design, which has
the pod running on a very thin air cushion. In practice, most designs are
maglev, for which a hard vacuum is best.

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e2e8
But that amount of air may not matter too much for the points discussed in the
video which have to do with strength, seals, etc.

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nether
There's also a single non-university group: Reddit's rLoop,
[http://rloop.org/](http://rloop.org/).

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foota
Now this is podracing!

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justifier
they just showed a pov of a pod moving through the hyperloop

it was cool to see the tires on the pod spinning as they made contact at the
beginning and the end of the loop but be still while moving through the loop

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frik
1967 Bay Area Gravity Vacuum Transit next to BART track ... sounds like
Hyperloop

[https://en.wikipedia.org/wiki/Pneumatic_tube#In_public_trans...](https://en.wikipedia.org/wiki/Pneumatic_tube#In_public_transportation)

Using the well known pneumatic vaccum tube not just for parcels but for public
transport is not a new idea. There have been such transports for some time
long in the past. The current question will the first such public transport in
this century be built in US or in China or somewhere else. The Transrapid
magnetic train was built in Shanghai China (called Maglev there) by Siemens
from Germany, another such cool idea that has little usage - but it works like
a charm there with 430km/h on a elevated 30km track for more than 10 years.

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tamal
Hyperloop utilizes an evacuated vacuum chamber. It's different than a
pneumatic tube concept.

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modeless
They just said it takes 30-40 minutes to evacuate the tube every time they
open it. I expected them to have some kind of airlock to help with that.

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ethbro
The only airlock necessary regular operation is for the introduction of
squishy meat into the pods, no?

I'd be curious what kind of compression you would need to make air bladders
seal around a door.

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TearsInTheRain
Anyone have a vod of the stream?

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SkyRocknRoll
Here is a video on facebook.

[https://www.facebook.com/dailybreeze/videos/1015491266465432...](https://www.facebook.com/dailybreeze/videos/10154912664654326/)

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coss
Any information on how students tested their pods?

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baking
There was a ten step process. There was a stationary vacuum test to assure
that the components would operate in a vacuum, there was a moving open air
test on a rail, and the final moving test in the mile long low-pressure tube.
The other 7 steps were design and safety reviews and a check of the control
system. 3 of the 27 teams passed the first 9 steps and participated in the
final speed test.

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capkutay
So is this a legitimate step closer to having the hyperloop or is it more of a
hiring/PR stunt for SpaceX?

Has anyone confirmed that the hyperloop could survive a seismic event?

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djsumdog
I feels very publicity. I wonder what they make this kids sign in order to
join the competition. I bet SpaceX gets to keep the intellectual property.
Seems like a cheap way to get a bunch of engineering ideas.

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Twirrim
[http://www.spacex.com/sites/spacex/files/2016_0831_hyperloop...](http://www.spacex.com/sites/spacex/files/2016_0831_hyperloop_competition_ii_rules.pdf)

I did a quick bit of looking around, rather than making accusations about the
company. So far I find no indication in any of the rules I've found for the
competitions that SpaceX is running that would suggest any such thing.

It's probably worth pointing out that SpaceX isn't much involved in Hyperloop.
Elon published the idea, and has mostly left it up to other groups to work on
/ produce.

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RA_Fisher
It's hard to celebrate achievements that can be linked back to Elon knowing
that he's lending legitimacy to Trump.

