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posted by n1 on Friday July 14 2017, @09:09AM   Printer-friendly
from the levitating-shopping-carts dept.

Submitted via IRC for AndyTheAbsurd

Hyperloop One claims that its prototype ultra-fast train has completed a first full systems test in a vacuum, reaching a speed of 70 mph. The sled was able to magnetically levitate on the track for 5.3 seconds and “reached nearly 2Gs of acceleration,” according to the company.

The test was conducted privately but Hyperloop One offered some video that included footage from testing. Based on that footage plus a few seconds of additional b-roll shared with media, a lightweight skeleton sled uses a linear motor to accelerate, levitates briefly, and then comes to a halt as the brakes are applied.

Hyperloop One was created as an answer to a challenge from Tesla and SpaceX CEO Elon Musk, who wrote a white paper envisioning a mode of transportation that would send pods at speeds greater than 700mph using a low-friction environment and levitation using air bearings.

Source: Ars Technica


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  • (Score: 2) by PiMuNu on Friday July 14 2017, @10:29AM (11 children)

    by PiMuNu (3823) on Friday July 14 2017, @10:29AM (#539049)

    > They're proposing to built a tubular vaccum chamber thousands of times larger than any ever made before, for less money than a high speed rail line(!)

    Don't forget the maglev...

    > One microscopic breach anyway in that tube and the entire thing collapses

    Why?

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  • (Score: 2) by Arik on Friday July 14 2017, @11:27AM (9 children)

    by Arik (4543) on Friday July 14 2017, @11:27AM (#539065) Journal
    Not sure why I answered the guy that basically said the same thing instead of you when you posted first. Sorry.

    But the answer is because objects under vacuum are bearing a constant, heavy load of atmospheric pressure. What happens to things that bear constant loads when their ability to bear that load is suddenly impaired, whether by outside damage or long term strain or corrosion or what have you? They can and do collapse catastrophically. One tiny little flaw starts a chain reaction and in a fraction of a second everything is suddenly different.

    Maintaining a vacuum is hard, and it's very stressful on the machinery. The worlds largest vacuum chamber (NASAs SPF) is only 37mx30m surrounded by thick concrete etc., and it is not expected to hold day after day week after week - most of the time it's at normal pressure so that extremely meticulous maintenance can be maintained. They're talking about building a *300 mile long* vacuum chamber out of thin steel tubes and maintaining constant vacuum through summer days and winter nights year round.

    With passengers flying down it at 600mph.

    He's selling the Brooklyn Bridge, he just updated it.

    --
    If laughter is the best medicine, who are the best doctors?
    • (Score: 2) by PiMuNu on Friday July 14 2017, @11:58AM (8 children)

      by PiMuNu (3823) on Friday July 14 2017, @11:58AM (#539076)

      A vacuum cleaner maintains similar pressure differential (I looked it up, wikipedia said vacuum cleaner is at 0.2 bar, so 0.8 bar pressure differential vs 0.999 bar pressure differential for hyperloop). The difference isnt so huge. Typically, pressure vessels are hard (e.g. diving bottles) because you get ~ few 100 bar. I don't think vacuum vessels are very tricky. I found this

      http://engineersedge.com/material_science/pressure_vessel_required_shell_thickness_chart_13162.htm [engineersedge.com]

      I had to convert the units; 1 bar is 14.5 psi and 160 inches is 4 metres; so they need 3/16 inches of steel to cope with a few bar overpressure. I assume this chart is for overpressure (i.e. dealing with more pressure inside than outside), I didnt quickly find the equivalent for underpressure but I don't think it will be very much different. The point is it is standard engineering.

      ==

      I thought you might claim that an air leak will cause catastrophic failure because the maglev train has to be able to cope aerodynamically with entering non-zero air pressure. That would be a reasonable statement, but needs detailed study to demonstrate passenger safety.

      • (Score: 2) by Arik on Friday July 14 2017, @12:20PM (6 children)

        by Arik (4543) on Friday July 14 2017, @12:20PM (#539084) Journal
        As I said, the tube can cope with the pressure normally. The issue is that you have several hundred miles of it exposed to the environment and every inch would have to be *meticulously* maintained. Even then this is dangerous, because we simply can't control each and every variable all the time and the slightest screw up here would likely result in hundreds of casualties. We can't always predict metal fatigue with 100% accuracy. Best case it has to be offline most of the time while maintenance is being done. Remember you can't so much as replace a screw anywhere in this tube without clearing the entire length of passengers.

        Ok so you pay out the nose for numerous maintenance crews and have them crawling the entire length of it day and night. And you don't hesitate to take it offline for maintenance, even though that costs you tons of money and sends unhappy would-be customers to the competition. Can't take chances, so you do the right thing, good for you.

        You know what probably happens next? One of the maintenance guys drops a wrench and it hits the tube. Boom. Catastrophic failure.

        "I thought you might claim that an air leak will cause catastrophic failure because the maglev train has to be able to cope aerodynamically with entering non-zero air pressure."

        That's a perfectly valid point but it is weaker. Clearly this thing isn't going to work right with the vacuum compromised in any way - otherwise we wouldn't be going to all the trouble of making it run in vacuum right? Losing vacuum is going to be very bad. But it seems reasonable to expect they *could* cover that possibility programmatically by bringing everything to a halt in a controlled manner. There doesn't seem to be anything in their current plans about regular escape hatches for frightened passengers to crawl out of in such an event, and if we were going into real depth I would certainly bring this up - but the whole catastrophic failure at 600mph thing is just more important and less debateable.
        --
        If laughter is the best medicine, who are the best doctors?
        • (Score: 2) by PiMuNu on Friday July 14 2017, @01:01PM (5 children)

          by PiMuNu (3823) on Friday July 14 2017, @01:01PM (#539099)

          > As I said, the tube can cope with the pressure normally. The issue is that you have several hundred miles of it exposed to the environment and every inch would have to be *meticulously* maintained.

          I just disagree. A long stretch of tunnel will presumably have gate valves installed (standard tech, albeit bigger) so sections can be taken down for maintenance. Maintenance outages are what is done on e.g. UK trains and roads, where long stretches of railway and lanes of motorway are taken down every weekend for maintenance. Random result from google:

          https://www.gov.uk/government/news/night-closures-planned-for-m6-cheshire-smart-motorway [www.gov.uk]

          I don't see that this scheme is super dangerous/sensitive like you say. Its a couple inches thick steel walled tunnel. A dropped wrench is not going to blow it up.

          This is just not high tech. If it splits, it doesn't explode or anything - that happens to gas bottles at hundreds of bar, but not a pressure vessel at 1 bar. It just lets up the pressure in the tunnel. Oh dear, we close off a section of tunnel and get a bus to bring the passengers out, or send in the rescue train, or whatever scheme they invent. Everyone grumbles because they are a couple of hours late to work.

          • (Score: 2) by Arik on Friday July 14 2017, @01:28PM (4 children)

            by Arik (4543) on Friday July 14 2017, @01:28PM (#539103) Journal
            "I just disagree. A long stretch of tunnel will presumably have gate valves installed (standard tech, albeit bigger) so sections can be taken down for maintenance. "

            That's a good idea, but (correct me if I'm wrong) not one that seems to appear in their plans. But I'll give it to you, so you can seal a section and repressurize it and work on it, wonderful!

            But you don't want to do that when you have a whole procession of passenger cars hurtling down the tunnel toward that section at 600mph+. Obviously you have to first stop adding passengers, second wait for those already in to complete their journey, then THIRD you can take the section down for maintenance. This process, assuming their own projections, means a minimum of 35 minutes PLUS the actual time required on-site, for each incident.

            But more importantly, it means that no matter how badly you may need to shut it down NOW you MUST wait the 35 minutes for it to clear.

            You're not just stopping a mag sled that's running in a vacuum at 600mph+ with significant mass on a dime. Plus as I said their plans offer no hint as to any exit capabilities in the transit tube, even were it feasible to stop the sled without killing the passengers.

            "https://www.gov.uk/government/news/night-closures-planned-for-m6-cheshire-smart-motorway"

            Oh come on! That's a motorway, it's not pressurized, individual cars have their own motors and drivers (and steering) etc. The situations have virtually nothing in common, that's a joke?

            --
            If laughter is the best medicine, who are the best doctors?
            • (Score: 2) by PiMuNu on Friday July 14 2017, @01:56PM

              by PiMuNu (3823) on Friday July 14 2017, @01:56PM (#539110)

              > Oh come on! That's a motorway, it's not pressurized, individual cars have their own motors and drivers (and steering) etc.
              > The situations have virtually nothing in common, that's a joke?

              My point was for the bureaucracy - shutting down for maintenance is an accepted practice in modern transport infrastructure.

              I reckon agree to disagree. I just think you are massively overegging the challenges. Anyway, hope they figure it out...

            • (Score: 1) by khallow on Saturday July 15 2017, @02:47AM (2 children)

              by khallow (3766) Subscriber Badge on Saturday July 15 2017, @02:47AM (#539445) Journal

              But you don't want to do that when you have a whole procession of passenger cars hurtling down the tunnel toward that section at 600mph+. Obviously you have to first stop adding passengers, second wait for those already in to complete their journey, then THIRD you can take the section down for maintenance. This process, assuming their own projections, means a minimum of 35 minutes PLUS the actual time required on-site, for each incident.

              Or you can divert those vehicles to another tunnel. I think the real problem with something like this is what happens when a huge stretch of the track is damaged. I don't buy that a minor leak can cascade to total collapse. But there are several sorts of accidents and sabotage that can take out a long stretch of track, say a raging forest fire, large airplane that crashes along the length of the Hyperloop, or a diligent saboteur with a lot of explosives. Replacing a lot of track lengths at once may be very difficult to do especially, if the manufacture of these components has been scaled down to maintenance level replacement. While most such normal rail is relatively easy to replace in comparison.

              • (Score: 2) by Arik on Saturday July 15 2017, @05:55AM (1 child)

                by Arik (4543) on Saturday July 15 2017, @05:55AM (#539477) Journal
                "Or you can divert those vehicles to another tunnel. "

                There are only to be 2 - one running each way. Their plans are quite explicit on that.

                I'm not saying this thing can't be built. I'm saying it would either be 1) tremendously and unacceptably prone to cause death if completed as presented and 2) if modified enough to avoid 1 it will no longer be competitive economically. The whole pitch here is the idea that not only can this be done, but it can be done safely and inexpensively, and that is simply bullshit. You can run add backup lanes and figure out SOME way to guide a mag sled hurtling along at 600miles an hour into it safely, you can wrap your steel tubes in concrete and more steel and install sensors and servos and...it's already going to cost orders of magnitude more to build and operate. And it no longer looks good next to the alternatives. And there are still LOTS of devils left to solve... no this is not a technology project. It may be, as another poster suggested, quite a successful scheme to get VC to develop components wanted for an entirely different project instead, but it certainly will never and could never work as advertised.

                --
                If laughter is the best medicine, who are the best doctors?
                • (Score: 1) by khallow on Saturday July 15 2017, @12:32PM

                  by khallow (3766) Subscriber Badge on Saturday July 15 2017, @12:32PM (#539523) Journal

                  There are only to be 2 - one running each way. Their plans are quite explicit on that.

                  I don't take their plans seriously at this point. A lot of what they would need to know about viable infrastructure, they'll learn later.

                  you can wrap your steel tubes in concrete and more steel and install sensors and servos and...

                  You're not presenting a serious argument either. A double shell would work here. The outer shell would shield from most external impacts and provide structural integrity, and the inner shell maintain the vacuum (including a safety margin for dents and such). You don't need massive infrastructure just to maintain a volume of vacuum. We already have companies that make large and often complex steel tubes for the oil industry and such. That infrastructure can be retooled to make Hyperloop sections, should that turn out to be a viable idea.

      • (Score: 2, Insightful) by Anonymous Coward on Friday July 14 2017, @05:28PM

        by Anonymous Coward on Friday July 14 2017, @05:28PM (#539211)

        A vacuum cleaner maintains similar pressure differential

        One pinprick through a vacuum cleaner hose starts a chain reaction and in a fraction of a second, BOOM! 🎆 Up you go in a cloud of mushrooms! ☁️🍄 Your city, too. It's Hiroshima all over again. MAN WAS NOT MEANT TO KNOW THE POWER OF THE VACUUM!!!

  • (Score: 0) by Anonymous Coward on Friday July 14 2017, @11:10PM

    by Anonymous Coward on Friday July 14 2017, @11:10PM (#539391)

    https://www.youtube.com/watch?v=T9bpUfWy8Wg [youtube.com]

    Something about like this.

    and this

    https://www.youtube.com/watch?v=AL4k9BGv_Gg [youtube.com]

    and this

    https://www.youtube.com/watch?v=G-3WiTMgSQ8 [youtube.com]

    That is about what it will be like. Remember with these vids were not 'total near vacuum' like they are talking about in the hyperloop.

    I have 0 doubt they will make a very long track. Manage to maglev a train in it in a vacuum. But they have a serious engineering problem they are not even talking about. It is a science experiment I learned in 5th grade with some water and steam and a sealed tin can.

    The atmosphere weighs quite a bit. Also nature abhors a vacuum.

    If they just get collapse it should not be a total loss. But if they get a rupture (likely) it would probably be a near total loss for most of the system.