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Thread: The US Air Force is developing the world's fastest "Hyperloop" train

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    The US Air Force is developing the world's fastest "Hyperloop" train

    I don't know if we can embed this type of video from msn.com, and I couldn't find it on YouTube, but here it is:

    The US Air Force is working on its own version of the Hyperloop — and it just set a world record


    While I was looking for the clip on YouTube I did find this though:

    [Just for clarification this is not the video about the Air Force's research, click the link above for that.]

    Last edited by bsbray, 26th April 2016 at 15:51.

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    bsbray:

    Some details about hyperloop as EM has conceptualized it:

    1. Pod moving at high speeds inside a tube.

    2. Tube with a near vacuum environment to reduce air resistance acting on the moving pod.

    3. Pod floats on a cushion of air scooped up from the front side.

    4. Pod powered by electromagnetic stator components positioned at 50 yard intervals within the tube (acceleration zones obviously have a smaller interval) and a corresponding induction coils on the pod (rotor). That makes for a working principle based on a linear induction motor design.


    Problems with the Air Force Implementation of the above concepts.

    1. Air Force Pod is not tested in a tube.

    2. Reduced air resistance of a near vacuum operating environment of the pod is absent as the Air Force pod seems to be operating at normal atmospheric pressure in open air.

    2.a Even if it where to operate in a tube, the rocket exhaust would "pressurize" the tube, as a result operations would require constant use of big vacuum pumps to restore the vacuum environment.

    3. Electromagnetic levitation requires the entire track to be composed of stator components instead of using "pulse stations" at 50 yard intervals.

    I would say is is a video of a primitive magleve test more than it is about a hyperloop test.

    Primitive because magleves can also be made with the characteristics of a linear motor. Obviously modules would be more complex as the rotor (pod) and stator (track) need to incorporate two functions, levitation and propulsion.

    Even supposing a yard of this more complex module could cost the same as the hyperloop's simpler unifunction (propulsion) rotor and stator modules, the track would still be 50 times more expensive because of the placements of these components.

    My view: the Air force experimentation is a device that does not compete with the hyperloop.

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    I'm sure these guys in the Air Force are on the ball with everything you're talking about lcamm. I realize it wasn't in a vacuum tube, but if it were, of course theoretically it should go even faster. But I'm wondering if this isn't just to get it going very quickly to the target speed, at which point in a vacuum it should require no additional energy.

    In a vacuum environment, accelerating the vehicle to its travel speed is going to take by far the most energy. Then if it were anything close to a perfect vacuum at that point, the vehicle would maintain that speed indefinitely with little/no additional energy being required, which is the real prize here.

    Anyway the important thing is that the research is being done, trial and error is going on and some tinkering and experimentation are going to lead to new ideas and possibilities. What's important about a branch of the US military getting involved in this, besides the very deep pockets, is that we're hearing about it publicly, unlike lots of other technologies that the military has developed. So this seems to be a way of legitimizing the idea and more tacit endorsing of the US military of alternative forms of transportation and energy (the Navy is already working on water-powered ships).

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    I hear you bsbray. Maybe this is just about putting scientists to work; those scientists who have to be given something to do. Maybe it is about politics more than it is about transportation.

    I think this is vaporware, any money put into researching this will never be seen again.

    The only way it may make sense is if where used on the moon. And even there magnetic levitation is mostly a gimmick with the low gravity and all.

    The hyperloop is different because each problem is solved in the most simple way. Plus you don't have forces working against each other (rocket propulsion vs vacuum pumps)

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    Quote Originally posted by lcam88 View Post
    The only way it may make sense is if where used on the moon. And even there magnetic levitation is mostly a gimmick with the low gravity and all.
    Magnetic levitation is not so much a matter of combating gravity as it is a means for combating friction and inertia on the one hand, and greatly reducing the number of moving components on the other hand.

    A maglev system doesn't need to exert any mechanical force on the track in order to get (and keep) itself moving, and the maglev guiding system also helps stabilize the train during relatively high speed turns because the magnetic fields keep the train on the track. There's also no "wear & tear", no wheel spin during acceleration, no friction, no loss of traction because of frost on the tracks, et al. The motor and drive systems are also mostly maintenance-free in comparison to a conventional train.

    And of course, there's also no fossil fuel as a propellant, nor are there any overhead power lines (which can also suffer because of frost). Power is derived from the track itself by way of induction.
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    Indeed Aragorn.

    Inertia is unaffected, acceleration still consumes energy. We don't have a system that acts like a feather with the weight of a train; no inertial dampeners implied. The main difference is that the systems that deliver energy obviously are engineered around magnetics rather than engines, transmissions and wheels.

    The track needs to withstand equal and opposite forces that the maglev may exerts to accelerate and levitate, even if there are no "mechanical" linkages. A bridge still needs to withstand the weight of the track and the train that may pass over it.

    As to maintenance, wear & tear issues, that comes down to how well the engineering is done. Even conventional trains can be near maintenance free when they are well engineered. A poorly engineered maglev system may be more costly if, for example, the stator coils are not laminated properly. I do agree with you though, if we consider the best practical implementation, that the maglev system would indeed require less maintenance than a similarly engineered wheeled system.

    I think it is fitting to mention power consumption. A wheeled rail system does not consume any energy when it is not accelerating, the wheels support the weight and roll along with 10x less resistance than road and tire equivalents. The maglev will consume energy the whole time it is levitated, even if the cart is not moving along the track, just to maintain "floatation" of the cart. Even if you consider the best case scenario with superconductors, refrigeration still consumes.

    Certainly there is reduced friction over the wheeled rail system, but that reduction is certainly several orders of magnitude smaller than the energy required for levitation. We can expect maglevs to consume more energy even with reduced friction.

    I think the main advantage of maglevs is not efficiency, it is about the capability to reach higher speeds. That consideration comes with the presumption that power is "unlimited". That is how I see it.

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    Quote Originally posted by lcam88 View Post
    [...]

    I think it is fitting to mention power consumption. A wheeled rail system does not consume any energy when it is not accelerating, the wheels support the weight and roll along with 10x less resistance than road and tire equivalents. The maglev will consume energy the whole time it is levitated, even if the cart is not moving along the track, just to maintain "floatation" of the cart. Even if you consider the best case scenario with superconductors, refrigeration still consumes.

    Certainly there is reduced friction over the wheeled rail system, but that reduction is certainly several orders of magnitude smaller than the energy required for levitation. We can expect maglevs to consume more energy even with reduced friction.
    Actually, no, that is not true. At the moment, there are two main implementations of maglev designs.

    • One implementation has the train, when at rest, sitting on top of the rails, just like with a wheeled train. As such, it also starts accelerating at first like any normal, wheeled train, but once it picks up enough speed and the motor develops enough power, it'll transition to full magnetic levitation.

    • The other implementation uses permanent magnets to maintain the levitation and impermanent magnets for propulsion. Therefore, even when it's powered down, this type of train will still be hovering over the rails because of magnetic repulsion.

    Quote Originally posted by lcam88 View Post
    I think the main advantage of maglevs is not efficiency, it is about the capability to reach higher speeds. That consideration comes with the presumption that power is "unlimited". That is how I see it.
    They certainly can reach higher speeds, yes, and this would especially be the case for a maglev train inside a vacuum tunnel system. Out in the open air, maglevs can reach speeds of up to 560 km/h, but inside a vacuum tunnel network, they might be able to attain speeds well in excess of 2500 km/h. After all, the biggest encumbrance on account of speed is the aerodynamic drag coefficient, which increases exponentially while the speed increases linearly.

    For instance, if we define the drag coefficient of a vehicle going 50 km/h as Cx(50), then when said vehicle travels at 100 km/h, the drag coefficient will not be 2 * Cx(50) (= Cx(50) + Cx(50)), but rather Cx(50)² (= Cx(50) * Cx(50)).

    Not only does this mean that you will be needing an increasingly bigger amount of additional power just to go a little bit faster still, but at such high speeds, the heat caused by friction with the air will also become a serious problem.
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    I hear you.

    Energy increases to the square of velocity. (E = mv*v) Air resistance should increases by the square of v as well... R = v^2 * (aero coefficient) * (front cross secional area) * (viscosity constant of air @ nominal pressure)...

    The speed of maglevs in a vacuum environment will be initially limited by the curves built into the track, then by imperfections or undulations on the facing surfaces.

    I hadn't thought of permanent magnets built into the track for levitation. :/

    An induction motor develops torque when there is "slip" between the rotor (pod) and the "movement" of the stator field (track). You are saying, basically, that induction does not need to happen on both functions of the system (propulsion and levitation), it is sufficient on only one (propulsion) to then power the pod.

    The hyperloop system Elon Musk (EM) conceptualized uses a cushion of air for levitation purposes. A "hovercraft" within a tube. How exactly it starts moving and lifts off is an implementation issue. There may be wheels to help it move along until it can scoop up enough air to "lift off". It obviously would need to pass though an air-lock that separates the vacuum tube environment from the station. Passengers shouldn't need O2 masks to get on board!

    Because hyperloop levitation does not use magnetics, the magnetics of the system doesn't need to extend every bit of the tube. Rather magnetic modules that induct power to the pod and propel it down the tube can be spaced 50 yards or maybe even 100 yards apart when the pod is already up to speed... Or during startup, perhaps much closer together. The interval could increase as pod speed increases.

    Since the hyperloop pod is scooping up air as it moves along, air resistance force that we are calling drag is being used to push the air along and compressing it to a certain point. The conceptual pod Mr Musk shared has a type of turbine compressor wheel setup to grab air from that high pressure zone for use in levitation. Because of that, it can be said that propulsion energy is also used for levitation.

    Since air is part of proper functioning of the system, a perfect vacuum is undesirable; perhaps it can also be described as a low pressure environment. Obviously the lower the pressure the faster the pod would need to go to scoop up enough air to levitate. The faster it would need to go, the more wheels need to be robust during lift-off and landing.

    Perhaps added complexity of pressurized tanks to assist starting and stopping could be used instead of wheels?

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    Quote Originally posted by lcam88 View Post
    [...]

    The speed of maglevs in a vacuum environment will be initially limited by the curves built into the track, then by imperfections or undulations on the facing surfaces.

    I hadn't thought of permanent magnets built into the track for levitation. :/

    An induction motor develops torque when there is "slip" between the rotor (pod) and the "movement" of the stator field (track). You are saying, basically, that induction does not need to happen on both functions of the system (propulsion and levitation), it is sufficient on only one (propulsion) to then power the pod.
    Well, the whole concept is rather complex, so I'm simply going to defer to the Wonkypedia article.
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    Wonky indeed. There are different implementation options but the basic physics remains. Air force rockets being an examination of such an implementation.

    I wonder if the compressor turbine wheel could be eliminated all together in EM hyperloop concept. The moving pod "flies" through the tube. Micro-parachute concept of sorts; Im thinking of that Mission Impossible clip where Cruise takes a micro-parachute and jumps into a ventilation shaft to exit...

    No need for vacuum pumps either... When the pod nears the end of its destination, the kinetic energy of the pod can be used to drive air out of the tube. No need for regenerative breaking or other energy recovery systems.
    Last edited by lcam88, 27th April 2016 at 18:12.

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    By the time this technology is implemented they'll probably have figured out some really cool, unexpected ideas. With dedicated teams of engineers developing these things for weeks/months/years, I'd be disappointed with anything less.

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    And there's already a company working on vacuum tube transport:



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    Quote Originally posted by Aragorn View Post
    Well, the whole concept is rather complex, so I'm simply going to defer to the Wonkypedia article.
    I think this Wonky article explains the physics of maglevs better. A linear motor is basically the same thing but with components laid out straight rather than forming a loop. It isn't necessarily complicated, but there are a few details that are not completely intuitive. There are a few other details to consider as well, but mostly they have to do with "configuration differences".

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