SpaceX Hyperloop team aims for new high-speed acceleration and braking test record

By Greg S ยท 13 replies
Apr 9, 2018
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  1. Elon Musk made a few announcements over the weekend, including some updates on the Hyperloop pod. During the next phase of testing, the vehicle will be accelerated to half the speed of sound and then attempt to stop within a total distance of 1.2 kilometers.

    Achieving such high speeds over a short distance will undoubtedly place the Hyperloop pod under significant stress. Even Musk has his own skepticism, saying that it "could easily end up being shredded metal," but finds the concept of rapid transit to be fascinating.

    In previous tests by other entrepreneurs, the Virgin Hyperloop One managed to reach a top speed of 192mph and stop in less than 440 meters or slightly over a quarter of a mile. Doubling the speed and upping the distance by a factor of three provides enough room for a possible success, but there is good reason for questions to be raised.

    Not only does raising speed increase temperatures and forces that a pod must endure, the amount of power required to hurdle the capsule down a tube will be significantly increased. During the last record breaking attempt in August 2017, it took over 2.3 megawatts of power. This next test could require exponentially more power, potentially up to 10MW or more.

    Although Musk declined to provide an exact date for testing, progress is still evident on the Hyperloop project. The Boring Company is working in Maryland on a tunnel that could eventually be used as part of a Hyperloop transit system. The end goal is to reach speeds nearing 800mph and shuttle people between Washington D.C. and New York City in under 30 minutes.

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  2. VitalyT

    VitalyT Russ-Puss Posts: 3,922   +2,281

    Is it gonna be 193mph for 441 meters this time? I will be just as impressed as the last time.

    We may see the promised 800mph some time in the next century.
     
    wiyosaya and Uncle Al like this.
  3. Uncle Al

    Uncle Al TS Evangelist Posts: 4,007   +2,494

    Still reminds me of Spam in a can ...... just faster!
     
    VitalyT and wiyosaya like this.
  4. wiyosaya

    wiyosaya TS Evangelist Posts: 2,623   +1,238

    I would like to know what the G-forces are. That is something that needs to be considered for this thing to carry passengers - especially since I would think that few passengers are going to be able to cope with high G-forces unless they are in excellent physical shape. Without knowing the G-forces, this sounds like yet another exercise in Musk showmanship to convince shareholders he can actually do something.

    As I see it, this showmanship strategy of his will wear thin if he does not watch himself, and an interest in high-speed transportation is not a commitment to developing something useful.
     
  5. mbrowne5061

    mbrowne5061 TS Evangelist Posts: 902   +458

    If that is really how much power it requires, then this will never catch on as mass transit. 10MW to move only a handful of people at a time?
     
  6. Weedonald

    Weedonald TS Rookie


    I have taken the TGV and high speed trains in Germany that reach 240 km per hour and felt no g forces at all. Flying in a jet plane at 640 mph there are no g forces at all, maybe at 800 mph there might be but we won't be seeing that anytime soon apparently.
     
  7. Urgelt

    Urgelt TS Enthusiast Posts: 65   +37

    It's not clear from the article if the 'speed of sound' is the speed of sound at sea level air pressure or if it's the 'speed of sound' in the low-pressure environment provided by the hyperloop tunnel. It's an important distinction.
     
  8. Fobus

    Fobus TS Booster Posts: 85   +52


    I don't think you understand what G forces are then... it's acceleration, not something to do with particular speed. G forces are most pronuonced during the initial speed up. It takes a lot more to sustain G forces already going at 640.
     
  9. Evernessince

    Evernessince TS Evangelist Posts: 2,709   +1,816

    I suspect that a commercial version of the hyperloop won't go too much faster than an Airplane. I'm no engineer and have no idea if it's possible to reduce the amount of g-force felt by passengers.
     
  10. wiyosaya

    wiyosaya TS Evangelist Posts: 2,623   +1,238

    Like @Fobus said, it is the acceleration that causes G-forces.
    From the article:
    Accelerating up to half the speed of sound and then decelerating in the specified distance just might generate significant g-forces, which is why I questioned what the g-forces are. 1.2 kilometers is about 3/4 mile. I have not done the math, but I expect that the g-forces involved would be something greater than one.
     
  11. cliffordcooley

    cliffordcooley TS Guardian Fighter Posts: 10,231   +4,157

    Stress testing finds any weakness in design. That is the point in doing these test. This amount of acceleration will not be used in public transport. Slow acceleration, slow deceleration, and as fast as possible between those two ranges is the idea. But if the system doesn't hold up under high G-Force, there is no need in thinking it will hold up long-term under less G-Force transporting people.
     
    CrazyDave likes this.
  12. erickmendes

    erickmendes TS Evangelist Posts: 387   +154

    How much pollution you think an airplane churns out burnning oil? Also, hyperloop pods can travel one after other in rapid sucession.
     
  13. wiyosaya

    wiyosaya TS Evangelist Posts: 2,623   +1,238

    I get what you are saying, but I still think this test is for show, to set new records, etc.

    At the very least, this might be a test to determine a stopping distance for the train as it currently is, however, in real life, there will be significantly more mass and it will take much more energy dissipation to stop it (directly proportional to the square of the train's velocity), not to mention it will take significantly more energy to accelerate it to any speed. EDIT: stresses on an unloaded train will also be significantly different from those on a loaded train, too.

    If the design intent is to move people, and maintain, for instance, an acceleration of 1G when accelerating or decelerating, then there is no point, at least as I see it, in stressing it to this level. It falling apart during this test is relatively meaningless if it will never experience similar acc/deceleration in practical use. My viewpoint is certainly limited since I am not part of the test, and thus it seems, as I said above, like this is nothing more than a "for show" test - like Musk scheduled the Falcon Heavy launch earlier this year a day or two before the Tesla earnings report to deflect away from how much money Tesla is losing. The next Tesla earnings report is scheduled for May 2, 2018. To me, the scheduling of this test seems fishy - though the article does not mention the date.

    Edit: I will add that expectations for the Tesla's earnings again are somewhere around -$4.50 per share - another loss.
     
    Last edited: Apr 10, 2018
  14. mbrowne5061

    mbrowne5061 TS Evangelist Posts: 902   +458

    I promise you, it is not in the 'MW/person' range. The Dreamliner uses 2x engines, and in its most powerful configuration (GE's GEnex-1B76 engines) uses 76,100 lbf for each engine. This works out to just 0.2MW of power. Divide that by the number of people on the plane. Even if it is just a single passenger, you're still 50x more efficient because this Hyperloop is still getting its energy largely from fossil fuels as well. Of course, this is just the electrical requirements of the system - never mind the monumental amount of energy it takes to pull and maintain a vacuum on a closed mechanical system. I hope this is just a misprint, the energy required, or this tech is DOA.

    Rapid succession wouldn't save power. That's not how power works - electrical or mechanical - not even a little. The energy requirements per pod don't go down. If it changes the efficiency of the system at all, it would likely make it less efficient.
     
    erickmendes likes this.

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