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View Diary: Elon Musk Unveils Hyperloop Ultra-Rapid-Transit Conceptual Work (247 comments)

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  •  Wow, congratulations. (0+ / 0-)

    You actually read what you were debating about halfway into the debate about it.  Kudos to you, want a cookie?

    The rocket jet flow requirements are .16 lb/s at 110 psi
    This is for a rocket that operates with about 1/6th of the weight of the hyperloop and at speeds that are mach 5 in normal atmosphere.
    First off, comparing a hypersonic air slipper with a subsonic slipper is an absurdity, shocks will render it to having completely different performance characteristics.  Secondly, the rocket is operating in normal atmospheric condition, so that furthermore not only renders the comparison moot.  Third, it's idiotic taking an air gap conclusion from skis with one set of dimensions, shapes,  and operating conditions and saying that they're going to automatically apply to a set of totally different skis in a totally different set of conditions; the pressure requirements and distances will vary tremendously (you can go all the way up to several meters separation on an air cushion if you add stubby wings - look up "ground effect vehicle").  And lastly, they've already done CFD sims, these are the numbers the CFD sims yield.
    At any given moment there will be approximately 5 shuttles in each tube (3 in transit and 2 accelerating/braking)  This means there will need to be a system-wide evacuation system that can continually remove all of this constantly venting air, to maintain the very high vacuum.
    (Must Find Wall To Bang Head Into

    The air is coming from the compressor.  That means, from the tube itself.  It's coming from the tube, and leaving to the tube.  There is no net change.  These aren't rocket engines venting exhaust.  The tube remains the same pressure.  The whole point of hyperloop is that it's a self-contained low pressure system.  There's no way on earth that a ~350kW compressor would have trouble producing the required flow and pressure rates when the vehicle itself is moving at hundreds of miles per hour - it's only 15-20% of the total that would be shunted to the skis.

    If vacuum is not maintained then the operational speeds will drop due to the significant drag coefficient, more air will need to be vented and the air capacity will be drained.
    1/1000th of an atmosphere is enough to render the pressure low enough that a reasonable-sized onboard battery bank and compressor can move all of the air from in front of the vehicle to behind it.  So there's really no point to going further, as energy requirements and construction difficulty rises tremendously trying to go all the way to a hard vacuum.
    So why not a maglev?
    Because maglev costs a bloody fortune, which is why it's been so little utilized.  The whole point is economical low energy transport.  Air cushion will always beat maglev hands-down in cost effectiveness.

    Já þýðir já. Nei þýðir nei. Hvað er svona erfitt við það?

    by Rei on Wed Aug 14, 2013 at 08:27:14 AM PDT

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