Hyperloop

[kevin99]

The Chinese did not disappoint. They beat everyone coming up with something at least humorous, a rare quality I am afraid.

The US is still debating why hyperloop does not work. Wake up, it only costs $6 billions! hardly anything the Chinese will frown upon, if the cool factor is so huge. And just for the coolness, the Chinese will throw $6 billions into the loop.

Thanks for sharing.

Here is the Hyperloop video.

 

[vfx]

The Daily Show covered it tonight.

 

[vfx]

How hot will a metal tube sitting in the California desert get?

 

[stevezzzz]

How hot will a metal tube sitting in the California desert get?

Hmmm, if it's well shaded by solar PV panels it will float at ambient temperature except when the sun is low; then it'll run above ambient by some amount.

 

[Palpatine]

With all of those solar panels on top, are air conditioners out of the question to cool the air inside of the tube?

 

[Norbert]

There's a similar criticism at http://greatergreaterwashington.org/post/19848/musks-hyperloop-math-doesnt-add-up/. That article's point is mainly that the maximum throughput of the Hyperloop is much less than the proposed train system, and that the Hyperloop's capacity is false because the car spacing has to be greater for safety. I have no comment on the train ridership projections except that they are quite controversial. However, the assertion that the spacing between cars would have to be increased for safety is at best disingenuous IMHO. The assumption is that the spacing can't be less than that required to stop a car, so at .5 g the spacing would have to be increased to 80 seconds, thereby decreasing the hourly capacity. Assuming that the emergency stopping rate is the same as normal stopping seems ridiculous to me since in an emergency, passenger safety would trump passenger comfort. There are many street legal cars that can safely stop at over 1g and, with a solid metal tube surrounding the Hyperloop cars to push against, an emergency braking system that stops at the required 1.2 g seems perfectly save and reasonable.

Agree. Additionally, on a freeway, cars are driving much closer to each other than they need to stop. They take into account that the car ahead won't stop in an instance (except in an extreme accident). An automated system within a tube can surely respond much faster than a human driver on the freeway. Even in case this might mean that in an extreme accident, a following car might crash into the preceding one, that's still only 2 * 28 people affected, versus a whole train with hundreds of people, when one element in a long train, or something on the track, causes an accident.

 

[NoMoGas]

The Daily Show covered it tonight.

You mean panned the ever-loving-sh** out of it... with mis-information and mockery (aka Elon=Tony Stark)

It was funny... but still stung a bit. The ending was great Elon "I don't have time to build this" "John Oliver (incredulously) "Then why the F*%# am I here?"

 

[vfx]

I'd say this was more good natured ribbing.

Track to the Future - The Daily Show with Jon Stewart - 08/14/13 - Video Clip | Comedy Central


At the very very end there was almost a wink with that smile.

 

[gregincal]

With all of those solar panels on top, are air conditioners out of the question to cool the air inside of the tube?

Actually since the water is to cool the compressed air stream then each capsule is acting as an air conditioner, since that's what air conditioners do; compress an airstream, cool it and then decompress it again.

 

[Ben W]

There's a similar criticism at http://greatergreaterwashington.org/post/19848/musks-hyperloop-math-doesnt-add-up/. That article's point is mainly that the maximum throughput of the Hyperloop is much less than the proposed train system, and that the Hyperloop's capacity is false because the car spacing has to be greater for safety. I have no comment on the train ridership projections except that they are quite controversial. However, the assertion that the spacing between cars would have to be increased for safety is at best disingenuous IMHO. The assumption is that the spacing can't be less than that required to stop a car, so at .5 g the spacing would have to be increased to 80 seconds, thereby decreasing the hourly capacity. Assuming that the emergency stopping rate is the same as normal stopping seems ridiculous to me since in an emergency, passenger safety would trump passenger comfort. There are many street legal cars that can safely stop at over 1g and, with a solid metal tube surrounding the Hyperloop cars to push against, an emergency braking system that stops at the required 1.2 g seems perfectly save and reasonable.

The author's math is off by a factor of 2. If I'm traveling at 760mph and decelerate at 0.5g, it does take 68 seconds to stop. But my average speed during deceleration is only 380mph! So if the car 30 seconds ahead of me stops on a dime, I would only have to decelerate at 0.57g (and stop in 60 seconds) to avoid a collision. No doubt the systems onboard would be capable of even more rapid deceleration in a true emergency.

 

[Norbert]

The author's math is off by a factor of 2. If I'm traveling at 760mph and decelerate at 0.5g, it does take 68 seconds to stop. But my average speed during deceleration is only 380mph! So if the car 30 seconds ahead of me stops on a dime, I would only have to decelerate at 0.57g (and stop in 60 seconds) to avoid a collision. No doubt the systems onboard would be capable of even more rapid deceleration in a true emergency.

Also, I don't think it is an absolute requirement that the airlock has to complete its de/pressurization in 30 seconds, as there could be more than one, operating in parallel (if really necessary). And, it would probably be just a minor additional cost (if not already planned) to have more bays in the station than necessary to run at full speed, if in practice that would actually be necessary to avoid delays in the whole system due to a potential delay of a single pod. (I think the example with a cell phone is bogus in any case, as with trains at short stops, subways, buses, or taxis, you can't go back either. They are gone in a matter of seconds).

 

[sp4rk]

I'd say this was more good natured ribbing.

Track to the Future - The Daily Show with Jon Stewart - 08/14/13 - Video Clip | Comedy Central


At the very very end there was almost a wink with that smile.

Maybe I am / we are too close to this project ... but I found that insulting.
Or did I lose my sense of humor next door?

 

[Norbert]

Maybe I am / we are too close to this project ... but I found that insulting.
Or did I lose my sense of humor next door?

Just the silly kind of thing a Jon-Stewart-replacement might do when given the task to do a comedy on something as out of the ordinary as a hyperloop, proposed by someone as out of the ordinary as Elon, when even experts are not sure what to make of it.

 

[JRP3]

I LOL'd. If an idea can't stand up to ridicule it's probably not a great idea to begin with.

 

[pete8314]

I thought it was OK. Did anyone catch the Moment of Zen at the end? More genius from network news.

Moment of Zen - "Elton" Musk - The Daily Show with Jon Stewart - 08/14/13 - Video Clip | Comedy Central

I'd love to see Elon on the Daily Show (when Jon is back)...despite the obvious comedy angle, they do occasionally have inspiring guests.

 

[sp4rk]

I LOL'd. If an idea can't stand up to ridicule it's probably not a great idea to begin with.

I guess I agree with you, although I find him ridiculing a man I highly respect. Then again, many ridiculed the Model S, ... and still do.
I do like John Stewart ... but not watched him in years.
And British humour SUCKS. I should know!

 

[Ben W]

Now that I think about it, I wonder how the emergency braking system is going to work without destroying the tube in the process. The passenger capsule at full speed has about 240kWh of kinetic energy. With 30-second (10km) spacing between capsules, in an emergency, the capsule will have to bleed off that energy in less than a minute, for a power rate of about 15 megawatts. If the capsule is in one of the "coasting" sections of the loop, that's one heck of a lot of power to dissipate into a smooth polished 1" thick steel tube.

I would think the only reasonable solution for this would be to quickly pressurize the tube ahead of the capsule, and use the air pressure to do most of the braking. The air will heat up a lot; one kilometer of hyperloop at 1 atmosphere contains about 12000 cubic meters of air, or 14 tons. The energy of "aerobraking" is enough to heat up this volume of air by 72 degrees Kelvin (130 °F). For perspective, that would take 70 °F room-temperature air and raise it to 200 °F. So even once the capsule coasts to a stop, the air surrounding it is going to be pretty toasty.

 

[TonyWilliams]

Reverse thrust, like a rocket or jet aircraft.

The emergency stop can be augmented by bottles of stored energy to release with braking.

 

[Norbert]

I thought it was OK. Did anyone catch the Moment of Zen at the end? More genius from network news.

Moment of Zen - "Elton" Musk - The Daily Show with Jon Stewart - 08/14/13 - Video Clip | Comedy Central

I'd love to see Elon on the Daily Show (when Jon is back)...despite the obvious comedy angle, they do occasionally have inspiring guests.

He actually was on the daily show (with Jon Stewart):

Exclusive - Elon Musk Extended Interview Pt. 1 - The Daily Show with Jon Stewart - 04/10/12 - Video Clip | Comedy Central

- - - Updated - - -

So even once the capsule coasts to a stop, the air surrounding it is going to be pretty toasty.

Let's hope the capsule would press that hot air out of the (opened) tube, and pull in fresh air behind it. Or something.

Elon was mentioning the importance of negative feedback. Curious about any update that will address at least some of the many concerns being voiced currently...

 

[pete8314]

He actually was on the daily show (with Jon Stewart):

Exclusive - Elon Musk Extended Interview Pt. 1 - The Daily Show with Jon Stewart - 04/10/12 - Video Clip | Comedy Central

Awesome, thanks for the link, it's a good interview.