General > General Technical Chat
The Hyperloop: BUSTED
EEVblog:
--- Quote from: mtdoc on July 29, 2016, 04:55:25 am ---That is a completely fair assessment and one I would not argue with but it is completely different than TF's attempt at "busting" it.
--- End quote ---
You're taking it too literally. He's just pointing out the various problems.
In essence what he's saying is the same thing, it's just not going to be practical.
--- Quote ---The difference is that the solar roadways claims regarding solar output (and therefore benefit of the roadway) are easily and verifiably false where as the possibility of building a hyperloop with the benefits as envisioned by Musk is unknown - despite TFs elaborating on some of the challenges. They may turn out to be insurmountable - but at this point that is an unknown.
--- End quote ---
Unknown? Rubbish. It something you can easily do back-of-the-envelope calcs on to ascertain the potential problems as TF has done.
You just don't like to admit that ultimately he's going to be right.
I can smell this engineering disaster a mile again, I'm surprised you can't.
Someone:
--- Quote from: EEVblog on July 29, 2016, 04:38:32 am ---
--- Quote from: Mark_Of_Sanity on July 29, 2016, 04:28:31 am ---Where as with the vactrain i.e. Hyperloop, the supposed benefit is frictionless travel.
Maglev to get rid of wheel friction and a vacuum environment to get rid of air resistance.
--- End quote ---
Why bother?
I've been on a MagLev train at 430kmh, it works, it's safe, it's robust, and it's fast enough.
To go through orders of magnitude more engineering complexity, safety, and security to get the only tangible benefit which is double the speed seems pretty darn stupid to me.
--- End quote ---
You could use the same argument to suggest that "high speed rail" as extensively used in Germany and the UK at half the speed and half the cost again would be sufficient. Maglev has some unique features making it attractive for short routes (Airport-CBD links are just about perfect) but its not a sure thing.
Externalising costs of the infrastructure makes air travel more cost effective than rail at the moment, and the hyper loop appears to be no more energy efficient than conventional rail so its hard to find much attractive about it.
Mark_Of_Sanity:
I disagree, sure it maybe impractical but we don't know that for sure until we really test it out.
Here's an excerpt from wikipedia page on drag,
"Power
The power required to overcome the aerodynamic drag is given by: ...
Note that the power needed to push an object through a fluid increases as the cube of the velocity. A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7.5 kW) to overcome air drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW).[16]
With a doubling of speed the drag (force) quadruples per the formula. Exerting four times the force over a fixed distance produces four times as much work. At twice the speed the work (resulting in displacement over a fixed distance) is done twice as fast. Since power is the rate of doing work, four times the work done in half the time requires eight times the power."
So in light of that problem, an engineer wondering as to how much better a train would function in a low pressure environment, or
a vacuum, isn't a completely disconnected thought, unlike with the solar roadway project.
And suppose that doubling of the speed came for roughly the same energy expense as a train traveling half that speed through
air at 1atm? That would be getting a level of performance that would normally require 8 times more power!
Now lets use the transrapid as an example, which I am fairly sure is the one you rode if this was in China.
Again wiki states,
"The normal energy consumption of the Transrapid is approximately 50 to 100 kilowatts (67 to 134 hp) per section for levitation and travel, and vehicle control. The drag coefficient of the Transrapid is about 0.26. The aerodynamic drag of the vehicle, which has a frontal cross section of 16 m2 (172 sq ft), requires a power consumption, at 400 km/h (249 mph) or 111 m/s (364 ft/s) cruising speed, given by the following formula ... 3.53MW"
So under the hyperloop concept, assuming the utmost ideal result, you would be getting double the normal performance
at 3.53MW instead of 28.24MW!
That seems worth trying out imo.
mtdoc:
--- Quote from: EEVblog on July 29, 2016, 05:23:08 am ---It something you can easily do back-of-the-envelope calcs on to ascertain the potential problems as TF has done.
--- End quote ---
I think pointing out potential problems is very different than "busting" something. As others have said, it dilutes the "busted brand". It will just lead to a boy-who-cried-wolf phenomenon.
How easy would it have been to do back of the envelope calculations to ascertain the potential problems of proposed NASA missions 60 years ago?
I've already said that i don't think it is likely to be built but TFs videos did not convince me that it will be because of insurmountable technical difficulties - It's too soon to say IMHO. But i'll admit I say that simply as a science/technically literate outside observer and not as an engineer.
In any case I'm glad companies like Hyperloop One are attempting to overcome the technical hurdles. It will be fun to see how far they get.
I am dissapointed that TF seems to be tryiing to milk the success of the solar roadways "Busted" videos and in that way is guilty himself of using hype to sell a product.
EEVblog:
--- Quote from: Someone on July 29, 2016, 05:40:31 am ---You could use the same argument to suggest that "high speed rail" as extensively used in Germany and the UK at half the speed and half the cost again would be sufficient.
--- End quote ---
Maybe, but at some point planes are going to beat them.
--- Quote ---Maglev has some unique features making it attractive for short routes (Airport-CBD links are just about perfect) but its not a sure thing.
--- End quote ---
Sure, but from a practical engineering point of view I know where I'd put my development money.
--- Quote ---Externalising costs of the infrastructure makes air travel more cost effective than rail at the moment, and the hyper loop appears to be no more energy efficient than conventional rail so its hard to find much attractive about it.
--- End quote ---
Agreed, especially with all the problems.
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