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      CommentAuthorAngus
    • CommentTimeAug 13th 2013 edited
     
    You can, but then you have to pump like hell. Not going to help your efficiencies.
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      CommentAuthoralsetalokin
    • CommentTimeAug 13th 2013 edited
     
    I want to see the vacuum pumps. Has anyone worked with vacuum systems? And I don't mean Hoovers.

    Imagine that you have the equivalent of a pinhole leak every 100 meters along the length of the tube, and that you have to airlock in and airlock out a capsule every thirty seconds at the ends. What is the total pump power needed to maintain your tube at 0.1 kPa?
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      CommentAuthorAngus
    • CommentTimeAug 13th 2013 edited
     
    I figured back of my head that the total emission of steam would fill 60 km of the tube at the 100Pa pressure. The trains run at distances a bit less than that (from memory). It constitutes the equivalent of a pretty serious leak.

    I think they would have to carry the heat with the vehicle, just as proposed, and dump it off as a lump at the end. Scary stuff.
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      CommentAuthoralsetalokin
    • CommentTimeAug 13th 2013 edited
     
    I wasn't even thinking of the steam, just the air.

    OK, before you fire off a capsule, you chill it by immersing in LHe until its water-ice subhull is nice and cold, then you fire it off. By the time it gets to wherever it's going it has warmed up and the water is liquid again, and you get your phasechange energy storage in the various ice-n transitions from a few K back up to 400 K or so. In other words, you remove the heat before you start, not after.
    • CommentAuthorkorkskrew
    • CommentTimeAug 13th 2013
     
    I get it. Steam wouldn't condense at that pressure and temperature. Sorry, I'm slow today.
    • CommentAuthorjoshs
    • CommentTimeAug 13th 2013
     
    Posted By: pcstru
    Posted By: korkskrewOk, so maybe he's god-ish.

    Too far?


    The heat is an engineering problem. I think Al has one the solution - you vent the steam. There are a number of ways to do that but they might fall into two usefully distinct problems; either you deal with a high humidity environment (yuch!) or you contain it and drop it off in managed 'packets'. So perhaps every so often you have a kind of siding - you decouple part of the car and it tracks into the siding while the passenger section goes onward. The heat package is decelerated and parked while it's heat is recycled. A previously dropped off container is accelerated and joins the car, couples in and starts supplying fresh coolant. That's viable technically (if running a tube with stations between the cities is). The question is how efficient it is (how much does it add to the build and running costs).

    Bollocks? Probably.
    I think the basic problem of shedding the kinds of energies they need to while racing down essentially an evacuated gun barrel is a BIG elephant in the middle of the room kind of problem to go along with the other elephant in the middle of the room problems this proposal suffers.
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      CommentAuthorAngus
    • CommentTimeAug 13th 2013 edited
     
    Posted By: alsetalokinOK, before you fire off a capsule, you chill it by immersing in LHe until its water-ice subhull is nice and cold, then you fire it off. By the time it gets to wherever it's going it has warmed up and the water is liquid again, and you get your phasechange energy storage in the various ice-n transitions from a few K back up to 400 K or so. In other words, you remove the heat before you start, not after.


    Sounds just as reasonable as the other. And certainly easier to store the liquid phase than the gas. Just pack the bottom with Blue Ice (TM)
  1.  
    Posted By: alsetalokinThe tube needs to be a torus, or rather a coaxial set of tubes. IOW, there needs to be a central, smaller tube along the axis of the main tube, and the passenger capsules ride along this central tube like donuts on a stick. Each capsule accommodates two commuters in luxurious head-to-toe wraparound comfort. The heat is transferred to the inner tube electrically/radiatively by induction coils, which can also be used to brake the capsule by eddy current braking. The inner tube has coolant flowing through it from end to end. Rapidly.
    FetalRail. Remember when this was the way it was?
    • CommentAuthorjoshs
    • CommentTimeAug 13th 2013
     
    Posted By: alsetalokinThe tube needs to be a torus, or rather a coaxial set of tubes. IOW, there needs to be a central, smaller tube along the axis of the main tube, and the passenger capsules ride along this central tube like donuts on a stick. Each capsule accommodates two commuters in luxurious head-to-toe wraparound comfort. The heat is transferred to the inner tube electrically/radiatively by induction coils, which can also be used to brake the capsule by eddy current braking. The inner tube has coolant flowing through it from end to end. Rapidly.
    Then there is the small problem of crossing the outer ring in order to connect the inner ring to the outside world. I think King Angus is closer provided one could come up with sufficiently materials that are sufficiently emissive at the required coolant temperatures.
    • CommentAuthorjoshs
    • CommentTimeAug 13th 2013
     
    Posted By: korkskrew
    Posted By: AngusSee my post way long ago where I also pointed out you can't vent steam into a 100 Pa tube atmosphere.

    People aren't keeping up here...
    Sorry, I missed that. Why can't you just vent to a 100 Pa pressure?
    Because the huge thermal mass that you vent won't make it 100Pa anymore. Consider for instance venting near special sections with extra capacity air pumps. Those pumps would have to remove the injected flow before the next pod hits at mach 0.9+. Have you ever seen what entrained droplets due to steam turbines? It is not pretty.
  2.  
    Drop molten blobbies behind you onto the pipe floor. The next guy trashes those blobbies and drops more. BlobbieRail. Because Travel Is Messy.
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      CommentAuthorAngus
    • CommentTimeAug 13th 2013
     
    Posted By: joshsThen there is the small problem of crossing the outer ring in order to connect the inner ring to the outside world.


    No problem. You just make the capsule out of a self-healing gel that reforms around the support struts as it passes them. Simples, really...
    • CommentAuthorjoshs
    • CommentTimeAug 13th 2013
     
    It has some parallels and anti-parallels to rocketry. In this case you have lots of energy that you need to dispose of more of less like a used booster. The problem is that you can't just dump it. Anything that the vehicle sheds of significant volume directly impacts the delicate balance of projectile / gun barrel areas and volumes.
    • CommentAuthorjoshs
    • CommentTimeAug 13th 2013
     
    Posted By: Angus
    Posted By: joshsThen there is the small problem of crossing the outer ring in order to connect the inner ring to the outside world.


    No problem. You just make the capsule out of a self-healing gel that reforms around the support struts as it passes them. Simples, really...
    So you saw "The Abyss" and "The Dome". I get it. They will fix the physical problems with CGI and editing tricks.
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      CommentAuthormaryyugo
    • CommentTimeAug 13th 2013
     
    Posted By: Andrew PalfreymanDrop molten blobbies behind you onto the pipe floor. The next guy trashes those blobbies and drops more. BlobbieRail. Because Travel Is Messy.
    Yes, I agree. It's all sort of a bad joke.
  3.  
    So far I think my precooled ultracold capsule is the best idea. Naturally.
    • CommentAuthorLakes
    • CommentTimeAug 13th 2013
     
    Posted By: Andrew PalfreymanDrop molten blobbies behind you onto the pipe floor. The next guy trashes those blobbies and drops more. BlobbieRail. Because Travel Is Messy.
    The instant you mentioned Blobbie...
    Mr Blobby
    Oh, the horror of it all....

    If you are going WTF???, here's some reading for you....
    http://en.wikipedia.org/wiki/Mr_Blobby
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      CommentAuthormaryyugo
    • CommentTimeAug 13th 2013
     
    But amidst the praise has been a growing chorus of skeptics who are either underwhelmed by the plans or who are skeptical that Hyperloop can be built. Many compared the hype surrounding Hyperloop to the buzz that accompanied the debut of Segway scooter in 2001, which never really caught on with the public.

    Twitter user @mozumder wrote, "I don't really see what the big deal is about the #hyperloop. Elon's report is on par with an undergrad thesis."

    Richard White, a professor of American history at Stanford and author of Railroaded: The Transcontinentals and the Making of Modern America, was also skeptical.

    "It doesn't seem plausible to me," White told The New York Times. "I'm suspicious about everything, especially cost."

    Musk says he thinks his system can be built for $6-10 billion, depending on whether it will be able to transport cars or not.

    "You can't even build the Bay Bridge for that much money," White said, referring to the still-unfinished renovations of the Bay Bridge connecting San Francisco and Oakland, which are expected to cost $6.3 billion.

    Twitter @RiaRomano worried about the safety of Hyperloop: "Is it just me or does anyone else think the Hyperloop sounds dangerous? No room for error at those speeds."

    Safety Concerns

    Musk acknowledges in his paper that there are risks, but argues that the system is safer than airplanes, trains, or automobiles.

    For one thing, because Hyperloop's capsule will travel in an enclosed space, it will be immune to wind, ice, fog, and rain.

    Furthermore, because the capsule will cover the vast majority of its route by coasting, it will not require continuous power, Musk writes. The capsule's life support system will be powered by two or more lithium ion battery packs and will not be affected by blackouts.

    As in airplanes, oxygen masks can also be deployed inside the Hyperloop capsules in the event of a sudden depressurization.

    "Once the capsule reached the destination safely it would be removed from service," Musk writes.


    http://news.nationalgeographic.com/news/energy/2013/08/130813-elon-musk-hyperloop-praise-skepticism/

    Life support system? Sudden depressurization? **shudder** This is not an airplane that can descend! It's stuck where it is, how it is, and with another train closing in extremely fast from behind. What fun!
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      CommentAuthorDerrickA
    • CommentTimeAug 13th 2013
     
    Posted By: Lakes
    Posted By: Andrew PalfreymanDrop molten blobbies behind you onto the pipe floor. The next guy trashes those blobbies and drops more. BlobbieRail. Because Travel Is Messy.
    The instant you mentioned Blobbie...
    Mr Blobby
    Oh, the horror of it all....

    If you are going WTF???, here's some reading for you....
    http://en.wikipedia.org/wiki/Mr_Blobby


    I've noticed Mr. Blobby never caught on in America. Probably, because the quota for inept buffoons has already been exceeded on Capitol Hill.
  4.  
    How about this: emergency valves open to the outside atmosphere to re-pressurize the tube in case of emergency. Would also help slow down the pods coming up behind.