SpaceX is livestreaming a hyperloop pod competition | Hacker News Reader

SpaceX is livestreaming a hyperloop pod competition

tech.slashdot.org

211 pointsMilnerRoute72 comments

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.

In high school we built and competed in a model solar car race. It was great fun and we learned numerous concepts like aerodynamics and torque.

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

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?

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.

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

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!

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.

The minimum pressure in the test track was 0.125 psi (teams using an air cushion could request a higher pressure and presumably if there was a leak the pressure could be higher than the minimum) while the air pressure on Mars is 0.087 psi.

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.

A balloon does a bloody good job of trapping gas, and so does the paper thin aluminium of an aircraft at altitude, or the tin cans of space stations, or an even better example, a bigelow space station. why do you find it so hard to believe a denser material like rock would be able to?

I'm sure you're concerned about fissures and other gas leaks, but 5 metres of most rock is going to do a pretty bloody good job, and I don't think anyone is saying we are going to be living in raw rock hewn caves - putty up the cracks or line with some other material and you're done

Protection from the Solar Wind (charged particles) primarily during solar flares.

http://www.caseyhandmer.com/home/mars

This was my first engineering design challenge and I have to agree with you: working on this from scratch was incredibly fun and is really what allowed me to find my love in engineering. I wish to do more of this type of design work when I graduate, but I'm aware that these things are usually reserved for more senior positions. Nonetheless it was a blast and something to work towards in the future.

Link to the SpaceX site one star of slashdot:

http://www.spacex.com/hyperloop

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

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.

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

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.

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

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.

The tube design is not final. They included a variety of features to allow some flexibility in designing pods. The radius is smaller than a full-scale hyperloop. Depressurization is not catastropic, as it would be for an oil tanker, so there is no need for a double hull. In fact, some leakage is expected. The real tubes will have airlocks. The test track was originally going to have airlocks, but they were scrapped for complexity.

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.

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.

It's not by their own power, there's a pusher vehicle bringing them up to speed.

The pusher is only accelerating the test vehicles up to a fraction of that, so that they can achieve levitation and after that the vehicle is under its own power.

It wouldn't make for much of a competition if the SpaceX vehicle was the one doing all the work.

Almost no pods have any kind of self propulsion. IIRC the whitepaper states the use of linear accelerators on the tube I-beams to propel the pod. That hasn't been integrated in the competition so the teams just coast at the pusher's 94km/h

The pushers max speed was 80 km/h. The Warr team accelerated past that to hit 94.

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

Why is that impressive?

decent aerodynamics?

Aerodynamics are negligible in a vacuum.

Isn't it a vacuum?

No. There's enough air pressure to potentially lift and cushion the pod in the pipe (at least in the original plan). However most pod designs (I think) use magnetic levitation for lift.

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.

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.

A true vacuum is literally impossible. It's not a category that can exist in nature, because particles aren't actually little balls that bounce around. Every volume has some probability of a particle being in it in the great universal configuration space. It can have an expected number of particles < 1, but never zero.

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 (p3)

It's impressive because these students are breaking new ground. One competitor just said they didn't know anything about batteries in vacuum, just for one example, and had to bring in an expert on that, among other challenges.

94km/h is a first step towards 1200km/h.

It's also a short track and 1/2 scale (1/8th volume) cars making 94km/h fairly difficult.

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

https://www.youtube.com/watch?v=RNFesa01llk

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

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

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

That's like saying there's no difference between 99.9℅ the speed of light and going all the way there, from an engineer perspective. Turns out, one of these requires an infinite more expenditure of energy than the other. Similarly, if you're evacuating a tube by removing gave the gas at a time, 1/1000 is attainable. 0? Not so much.

I don't disagree but that is not issue here. The issue is that for the purposes of discussing the mechanics of the tube like strength, seals, safety etc. the small amount of air left in the tube should not throw off simple calculations by too much.

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.

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.

That, and AFAIR original design had a system to pull the air from the front to the back, thus lowering the drag while reducing the need for lower air pressure.

There's no such thing as a 'full vacuum' in the real world. If you think that invalidates the arguments in the video then that likely means that you need to do more research on vacuum systems...

The whole video has been discredited.

Why? By whom? This statement alone isn't very helpful.

https://www.youtube.com/results?search_query=thunderf00t+hyp...

Thanks for the link, but would you add a bit of a summary?

Here is the /r/hyperloop thread discussing the video https://www.reddit.com/r/hyperloop/comments/4udod1/the_hyper...

There's also a single non-university group: Reddit's rLoop, http://rloop.org/.

Now this is podracing!

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

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

https://en.wikipedia.org/wiki/Pneumatic_tube#In_public_trans...

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.

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

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.

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.

That was the plan, but it turned out too complicated.

They only expected a few teams to pass all the checks to be ready to compete today, so that was not something they needed to focus on for this competition.

Anyone have a vod of the stream?

Here is a video on facebook.

https://www.facebook.com/dailybreeze/videos/1015491266465432...

Any information on how students tested their pods?

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.

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?

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.

A bit of googling doesn't turn up any mention of that sort of sketchy business. This seems like a pretty standard, innocuous publicity/recruiting event.

The world already has enough scandals without inventing fictional ones.

http://www.spacex.com/sites/spacex/files/2016_0831_hyperloop...

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.

Since the only practical application of this is on Mars, I wonder if intellectual property rights will matter.

Does it matter? They have built a prototype, has anyone else done that on this scale?

Experimenting with a decent sized model seems like a pretty big step towards having something workable.

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

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