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Sigmetnow

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Re: The Hyperloop
« Reply #150 on: August 31, 2017, 03:26:51 PM »
Elon Musk: We took the SpaceX/Tesla Hyperloop pusher pod for a spin by itself a few days ago to see what it could do when not pushing student pods (some need a push to get going, e.g. passive maglev). Got up to 355 km/h (220 mph) before things started [fire emoji]. Kind of like racing with a tugboat. Maybe able get past 500 km/h (about half speed of sound) next month with a few tweaks or maybe tiny pieces …
https://www.instagram.com/p/BYckipugds5/
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Sigmetnow

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Re: The Hyperloop
« Reply #151 on: October 12, 2017, 04:35:27 PM »
Hyperloop One becomes ‘Virgin Hyperloop One’ with new investment
Quote
Hyperloop One has been rebranded as ‘Virgin Hyperloop One’ following an unspecified investment by the company.

Virgin Group founder Richard Branson said that the investment was a good fit for the company …

“Ever since our creation, Virgin has been known for disruption and investing in innovative companies. From our airlines to our trains to our spaceline, we have long been passionate about innovation in transport too, especially the development of technology that could transform people’s lives. This is just the latest example. Importantly, Virgin Hyperloop One will be all-electric and the team is working on ensuing it is a responsible and sustainable form of transport too.” ...
https://electrek.co/2017/10/12/hyperloop-one-virgin-investment/
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Sigmetnow

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Re: The Hyperloop
« Reply #152 on: October 19, 2017, 12:00:38 AM »
The "other" major hyperloop company, Hyperloop Transportation Technologies (HTT), has a "viable" and insurable product, according to Munich Re insurance company.
HTT and Munich Re have formed a strategic partnership
Quote
Germany's Munich Re was tasked with carrying out a risk report of HTT's project and found it was feasible.

"Although as yet unproven in real-world testing, the Hyperloop technology is likely to be viable, and represents a realizable integrated system," Munich Re said in a report released on Tuesday. ...
https://www.cnbc.com/2017/10/17/hyperloop-transportation-technologies-viable-can-be-insured.html
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Bob Wallace

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Re: The Hyperloop
« Reply #153 on: October 19, 2017, 02:12:24 AM »
Quote
the Hyperloop technology is likely to be viable

Sounds like a group of normally very cautious people haven't found a fatal flaw.

Sigmetnow

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Re: The Hyperloop
« Reply #154 on: October 19, 2017, 02:48:14 AM »
Quote
the Hyperloop technology is likely to be viable

Sounds like a group of normally very cautious people haven't found a fatal flaw.

And they're willing to back that up with money.  Or with a partnership, anyway.
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Bob Wallace

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Re: The Hyperloop
« Reply #155 on: October 19, 2017, 03:36:34 AM »
I'd like to see how they are dealing with tube expansion in the heat and how the system would deal with an abrupt tube loss - where a section might be blown up or in another way destroyed. 

There must be a good answer or we wouldn't see so many groups getting involved. 

TerryM

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Re: The Hyperloop
« Reply #156 on: October 19, 2017, 06:10:25 AM »
Munich re is no joke & no small potatoes. Their agreement that this is viable and insurable amounts to a huge endorsement.
Terry

Bob Wallace

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Re: The Hyperloop
« Reply #157 on: October 20, 2017, 09:27:17 PM »

Sigmetnow

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Re: The Hyperloop
« Reply #158 on: October 21, 2017, 02:40:44 PM »
Cross-post from Boring thread:

Elon Musk:  @APTA_info @baltimoresun Not ready to do a proper announcement yet, but maybe in a month or so. Maryland has been awesome to work with and just wanted to say thanks.
     https://twitter.com/elonmusk/status/921419557918597120

Elon Musk to start hyperloop project in Maryland, officials say
Quote
Maryland has given transportation pioneer Elon Musk permission to dig tunnels for the high-speed, underground transit system known as a hyperloop that Musk wants to build between New York and Washington.

Hogan administration officials said Thursday the state has issued a conditional utility permit to let Musk’s tunneling firm, The Boring Co., dig a 10.3-mile tunnel beneath the state-owned portion of the Baltimore-Washington Parkway, between the Baltimore city line and Maryland 175 in Hanover.

It would be the first portion of the underground system that Musk says could eventually ferry passengers from Washington to New York, with stops in Baltimore and Philadelphia, in just 29 minutes. Maryland’s approval is the first step of many needed to complete the multibillion-dollar project.

Gov. Larry Hogan toured a site in Hanover that aides said could become an entry point for the hyperloop. The state does not plan to contribute to the cost of the project, aides said.
 ...
http://www.baltimoresun.com/news/maryland/politics/bs-md-hyperloop-in-baltimore-20171019-story.html

Edit:  This appears to be the location:  https://goo.gl/maps/qy6awSFSPCL2

39°08'42.0"N 76°45'04.6"W

Milestone Parkway, near the lower "295" label:
« Last Edit: October 21, 2017, 03:12:43 PM by Sigmetnow »
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Sigmetnow

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Re: The Hyperloop
« Reply #159 on: October 30, 2017, 12:43:16 AM »
If you are going to dream... dream big!  :)  An unconventional, un-"border wall" concept.

http://www.upworthy.com/trump-wanted-border-wall-designs-he-kind-of-got-the-exact-opposite
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Sigmetnow

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Re: The Hyperloop
« Reply #160 on: November 30, 2017, 03:44:41 AM »
Elon Musk:  The Boring Company will compete to fund, build & operate a high-speed Loop connecting Chicago O’Hare Airport to downtown
https://twitter.com/elonmusk/status/936060082290167808

Chicago seeking parties to fund, build, operate O’Hare express train
https://chicago.suntimes.com/news/city-seeking-parties-to-fund-build-operate-ohare-express-service/

Fred Lambert asked:  Can you clarify what's a "high-speed loop"? I assume we are not talking hyperloop? Is it the previously unveiled electric skate concept?
Musk: Kinda.  A Loop is like a Hyperloop, but without drawing a vacuum inside the tube. Don’t need to get rid of air friction for short routes.
https://twitter.com/elonmusk/status/936062403606822913

Fred Lambert:  That makes sense. So people are still traveling in electric-powered pods on rails?
Musk: Electric pods for sure. Rails maybe, maybe not.
https://twitter.com/elonmusk/status/936066967173193729
« Last Edit: November 30, 2017, 04:01:33 AM by Sigmetnow »
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Sigmetnow

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Re: The Hyperloop
« Reply #161 on: November 30, 2017, 04:03:41 AM »
Rails.  Meh.  So last century. ;D
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Bob Wallace

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Re: The Hyperloop
« Reply #162 on: November 30, 2017, 04:39:33 AM »
So maglev subway cars?  That makes sense to me for short run stuff like this.  Even 100 MPH with no stops along the way would be great.

Tor Bejnar

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Re: The Hyperloop
« Reply #163 on: December 19, 2017, 07:56:36 PM »
Virgin Hyperloop One reaches new record speed in test loop, raises another $50 million, and Branson becomes Chairman
Electrek.co

Quote
They say that they achieved a test speed record “of nearly 387 kilometers per hour” (240 miles per hour, 107 meters per second) at their ‘Devloop’ test track in Nevada.
...
The test was performed in a complete hyperloop system with a working pod and the tube depressurized down to “the equivalent air pressure experienced at 200,000 feet above sea level.”

Earlier this year, the company announced that it plans to have working hyperloop systems deployed by 2021.

Corporate and leadership topics are included (in fact lead) the article.  (Let's hear it for the "Me Too" movement!)
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Sigmetnow

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Re: The Hyperloop
« Reply #164 on: January 09, 2018, 05:34:03 PM »
“We see hyperloop as the high-speed backbone for mass transit networks, [it’s] far from just a pod in a tube. It’s a means to provide a seamless routing experience across multiple transportation modes.”

New Virgin Hyperloop One Details Revealed at the 2018 Consumer Electronics Show
https://futurism.com/virgin-hyperloop-one-reveal-consumer-electronics-show/
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Rob Dekker

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Re: The Hyperloop
« Reply #165 on: January 25, 2018, 06:43:07 AM »
I'm trying to compare energy use by airliners to energy use by MagLev, just to see if, and under which constraints, the concept of HyperLoop makes sense.

In this video of a successful Hyperloop pod :



they claim that they had to supply the electric equivalent of 3,000 hp (which is 2.2 MW) to levitate and propulse the pod.

Does anyone have any more info on how heavy this pod is ? Or energy use data on other MagLev prototypes ?
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Rob Dekker

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Re: The Hyperloop
« Reply #166 on: January 25, 2018, 08:53:38 AM »
And did Hyperloop present any numbers on how much power it will cost to maintain a vacuum in their tube ? And with airlocks (at start and finish) included ?
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Bob Wallace

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Re: The Hyperloop
« Reply #167 on: January 25, 2018, 09:04:56 AM »
I haven't seen any data on the energy needed to evacuate the tube.

I would think the airlocks would not be much of a load.  Assume the pod moves into an airlock and within less than a meter from the closed door.  A door closes behind the pod.  The total space to be filled or evacuated on departure is just the space around the pod.  Since the pod would enter at a slow speed the airlock could be a 'tight fit' for the pod and the distance between pod and doors very small.

Comparing energy use between planes and a maglev train may not tell you much.  The plane uses a lot of energy to reach altitude but then cruises in a low pressure atmosphere.  The maglev is shoving lots of air out of its way for its entire journey.

The Hyperloop would not have to achieve cruising altitude or shove aside air.

Sleepy

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Re: The Hyperloop
« Reply #168 on: January 25, 2018, 09:36:34 AM »
You have this one:
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170001624.pdf
Quote
Figure 12 shows how the power and energy consumption change with tube pressure. As expected, high tube pressures require lower power for a given leakage rate while requiring a higher power output from the onboard compressor for a given compressor ratio. Thus total annual energy cost increases for very low pressures, due to the vacuum system managing the air leakage, and increases for very high pressures, due to increased power demand from the compressor. The second plot in fig. 12 shows that this relationship produces a pressure at which energy cost is minimal. In this case, the energy consumption is minimal at about 200 Pa for a leakage of 3 kg s. Energy consumption increases fairly rapidly as pressure is increased beyond this minimum value. It is important to note that this exact value is dependent on the leakage rate, compressor pressure ratio, and whether or not regenerative braking is used to recover battery energy (no regenerative braking is assumed in this analysis). However, this relationship is crucial because it means that there exists a pressure that optimizes energy cost and that energy cost can increase rapidly if deviations from this optimum point exist. A higher fidelity model can be used to determine exactly what value of pressure optimizes energy consumption for a given configuration. A more detailed examination of the effects that leakage has on optimum pressure will be conducted next.

Quote
Figure 13 shows the pressure at minimum energy consumption and cost vs. the leakage rate of the tube. The tube pressure that optimizes cost increases as the leakage rate increases. This trend is reasonable because the increasing leakage rate increases the power required for the vacuum pumps to maintain the tube pressure, which is offset by increasing the pressure that the vacuum is required to maintain. This relationship is critical because it reveals a coupling between tunnel leakage and energy consumption that system designers must consider. As fig. 13 reveals, changes in the leakage rate can have a significant effect on energy consumption and energy cost. In fact, the cost penalty becomes even more substantial when operating at a suboptimal pressure. If the designer wants to optimize the system by minimizing the energy consumption, then more accurate modeling or empirical studies will be necessary to determine operating pressure. Furthermore, the assumption made that the leakage rate is constant is likely not indicative of a real system. Leakage, and therefore the optimal tunnel pressure, is also presumably a function of passenger pod frequency. System designers would need to account for variable tube pressure when sizing the battery, compressor motor, and tube diameter in order to give the operator flexibility to change the tube pressure with pod frequency. This would allow the Hyperloop system to adapt to changing operating conditions to more closely track optimal design configurations in real time. Further research with higher fidelity modeling is necessary to further characterize the benefits of variable tunnel pressure.

Edit; I was reluctant to add more since quoting from PDFs can be a bloody mess, but here's the last part of the conclusion as well:
Quote
A full model system study was performed to analyze the net energy usage of maintaining the tube operating pressure as a function of the leakage rate of air into the tube. The results show that the energy usage from this system is of the same order of magnitude as the energy required to propel the passenger pod. Furthermore, the two systems have opposite sensitivities with respect to tube pressure. As the tube pressure is lowered, the energy needed to propel the pod drops, but the energy required to maintain the vacuum goes up. The results show that there is an optimal tube operating pressure that is heavily dependent on the leakage rate. The higher the leakage rate is, the higher the optimal tube operating pressure becomes.

This work also extends previous research that shows traveling at speeds above Mach 0.8 is likely not practical. The tube size invariably becomes too large, given the coupling between tube size and pod travel speed. We refine that analysis to include the effects of boundary layer growth along the passenger pod. The data shows that boundary layer growth amplifies the coupling between tube size and travel speed and hence is an important consideration in Hyperloop design. As a result, further research on the modeling and implementation of active flow control is recommended due to its potential to significantly reduce required tube size.

Finally, net energy usage is found to be relatively insensitive to pod length. Therefore, the system would scale favorably to much higher passenger capacities than originally proposed. This also gives the operator freedom to vary capacity by lengthening or shortening pods, meaning travel capacity can be optimized to meet market demand without prohibitive costs to the operator.
Although the models presented in this paper are not of high fidelity, the trends and trade studies identified provide valuable insight into the engineering behind the Hyperloop concept and how these physical relationships can inform future design efforts. The open source, modular nature of this system model will allow future researchers to modify, adapt, and improve the model to include more specific subsystems and higher fidelity modeling as needed. The modeling platform is intended to serve as a publicly accessible baseline that is easy to expand and delve deeper into this unique multidisciplinary system.
« Last Edit: January 25, 2018, 09:48:35 AM by Sleepy »
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Rob Dekker

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Re: The Hyperloop
« Reply #169 on: January 26, 2018, 05:41:55 AM »
Thank you Sleepy !
That NASA article is really interesting.
I learned a lot reading it, and I would like to share some of the basic findings that stand out :

1) From Fig.13 (which you show), it appears clear that the majority of energy use will go to keeping the (near)vacuum in place. Which means that keeping this tube air-tight (less than 1 kg/sec) is absolutely crucial.
In my opinion, that requirement is going to be very hard to reach, especially knowing that they are going to have to install some flexible seals that can absorb thermal expansion (day/night) differences of the tube. As soon as there is ANY minor leak over the full track, pumping energy costs go up extremely rapidly. So that is a BIG problem.

2) The paper describes quite nicely that speeds close to MACH 1 will be very hard to achieve. The main issue is the airflow around the pod, which would start to 'stall' and create shockwaves if the speed is high and the cross surface area of the tube is not large enough.
Their figure 10 shows that convincingly, and looking at that exponential graph, it seems to me that Hyperloop should be happy if they will obtain maximum sustained speeds of 1/2 MACH (some 600 km/hour). Beyond that they will get into serious friction and shockwave issues.

3) The thickness of the steel appears to be quite large for a safe tube. Fig 8 suggests some 3 cm thick steel for a tube at sea level with a cross section of 20 m^2.
That's a LOT of steel for a tube of any reasonable distance (like SFO - LA).

4) If we would forget about the vacuum tube altogether, and just run a MagLev without the tube, the costs would be much, much lower.
We would not need any of the steel, nor any seals, nor airlocks, we would not have to waste ANY energy on any pumping, and we could still obtain speeds of up to 400-500 km/hour with reasonable energy costs (which is already close to the speeds of 1/2 MACH where Hyperloop starts to show problems).

Here is an article that explains that MagLev energy costs are comparable with High Speed Rail (HSR), which is another possible solution for links like SF-LA:
http://large.stanford.edu/courses/2010/ph240/ilonidis2/

The main take-away is that Hyperloop may be able to double the speed of HSR, but the costs are going to be much higher, and the technology to keep the tubes leak-free is simply not compatible with other issues like thermal expansion.

It seems to me that putting a vacuum tube around a Maglev (which is what Hyperloop is) is simply not worth the extra expense and technological trouble.

Just running HSR seems to be able to reach competitive speed to Hyperloop, and a much more practical and lower cost solution for distances like SF-LA. And they would have bathrooms in the cars. And windows to enjoy the ride. And a restaurant.
« Last Edit: January 26, 2018, 06:04:10 AM by Rob Dekker »
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Bob Wallace

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Re: The Hyperloop
« Reply #170 on: January 26, 2018, 07:12:42 AM »
Taking the pods into tunnels eliminates the thermal expansion problems and makes sealing a lot easier.

People will not get out of a plane and into a maglev for long trips.

Sleepy

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Re: The Hyperloop
« Reply #171 on: January 26, 2018, 12:21:46 PM »
Yeah Rob, nice summary and pretty much the same spots that I looked at.
Vacuum will be a real world problem. Also tunneling, but we know a lot more about tunneling.

Where are we today?
Here in Sweden we just said no to HSR (320km/h completion in 2035). The Swedish Society for Nature Conservation also said no due to the negative environmental impacts from building bridges and tunnels. They support the Swedish Transport Administrations proposal of 250km/h.
 
There are three major groups here, No1 wants to build 320km/h HSR, No2 wants 250km/h, No3 says no for a number of reasons, to expensive or we just don't need it, also a lot of people wants to wait for autonomous cars and the Hyperloop...
And as we know from the other thread, the only feasability study there is for the hyperloop here, is the one between Stockholm and Helsinki, estimated at € 19 billion.
https://forum.arctic-sea-ice.net/index.php/topic,856.msg139788.html#msg139788
It would be interesting to see a new study that considered the findings from that NASA study above.

Estimated costs for HSR, according to Sverigeförhandlingen is € 25 billion.
http://sverigeforhandlingen.se/
That would be the largest infrastructure venture in Sweden for 150 years...

My opinion? What I've tried to express above is today's reality here. Time's up. Everywhere I look, people act like we have eons of time available. Unless something changes drastically, the World will be close to +2°C in 2035. There are easier ways to mitigate, we might not like them, but the longer we wait, the worse it gets.

I'm all in for any solution outhere to eliminate emissions; that is cost effective, proven to work and ready to be used at latest in 2035.
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numerobis

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Re: The Hyperloop
« Reply #172 on: January 26, 2018, 01:19:34 PM »
I read the NASA study as suggesting Mach 0.8 — same speed as airliners.

At 0.02 atm, water boils at room temperature. Water leaks (quite common in tunnels) would have to get snuffed out.

The case for these taking the place of high-speed rail seems pretty weak. Whether a trip is going to take one hour or two isn’t that relevant. For long-distance travel, it could be viable to use more energy than aviation, if that means the energy is deployed more cleanly.

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Re: The Hyperloop
« Reply #173 on: January 26, 2018, 01:48:31 PM »
Why they chose 0.8:
Quote
Figure 10 indicates how the tube area and energy consumption change over a range of Mach numbers. As is indicated in previous research, tube area begins to increase rapidly around Mach 0.8. 1 Beyond this Mach number, small increases in Mach number result in a large increase in tube area, which will have a large impact on capital cost and energy consumption during pump down. Conversely, fig. 10 indicates that tube area, and therfore material cost, grows slowly with Mach number for Mach numbers below 0.8. Based on these results, it is estimated that any system level optimization of cost with respect to Mach number will likely result in a Mach number near 0.8. For this reason, a Mach number of 0.8 will be used in subsequent analyses to obtain reasonable evaluations of design trades and system behavior.
Adding Fig10 as well.
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numerobis

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Re: The Hyperloop
« Reply #174 on: January 26, 2018, 03:15:13 PM »
On the other hand, this study simply rejects supersonic speeds. I wonder how bad it would be.

It all feels pretty pointless though. Fun engineering questions; not likely to ever be built given the cost.

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Re: The Hyperloop
« Reply #175 on: January 26, 2018, 05:14:33 PM »
Taking the pods into tunnels eliminates the thermal expansion problems and makes sealing a lot easier.

People will not get out of a plane and into a maglev for long trips.

Putting hyperloops underground might be a necessity in the US for a whole 'nother reason.  If above-ground, imagine a vandal in a rural location, armed with a hunting rifle and armor-piercing bullets.  We have folks like that in this country.  One vandal with a few tens of dollars of bullets could incapacitate hundreds of miles of transport in minutes.  And do it again the next week.

Bob Wallace

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Re: The Hyperloop
« Reply #176 on: January 26, 2018, 05:20:44 PM »
Quote
At 0.02 atm, water boils at room temperature. Water leaks (quite common in tunnels) would have to get snuffed out.

So leaked water would vaporize.  What would that mean in terms of system operation?  The small amount of air remaining in the tunnel would be humid?  Would that be an operational problem?

This would be a fully lined tunnel.  Sealed to allow a partial vacuum.  Likely to have big water leak problems?  If there is a leak of any sort it seems that it would be quickly sealed. 

Sigmetnow

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Re: The Hyperloop
« Reply #177 on: January 26, 2018, 08:11:20 PM »
Some ideas from Elon Musk’s original white paper on the Hyperloop:

The vehicle is streamlined to reduce drag and features a compressor at the leading face to ingest oncoming air for levitation and to a lesser extent propulsion. Aerodynamic simulations have demonstrated the validity of this ‘compressor within a tube’ concept.  (Page 14)

4.1.3. Compressor
One important feature of the capsule is the onboard compressor, which serves two purposes. This system allows the capsule to traverse the relatively narrow tube without choking flow that travels between the capsule and the tube walls (resulting in a build-up of air mass in front of the capsule and increasing the drag) by compressing air that is bypassed through the capsule.  (See P. 17 for details of the mechanics)

4.2. Tube
The main Hyperloop route consists of a partially evacuated cylindrical tube that connects the Los Angeles and San Francisco stations in a closed loop system (Figure 2). The tube is specifically sized for optimal air flow around the capsule improving performance and energy consumption at the expected travel speed. The expected pressure inside the tube will be maintained around 0.015 psi (100 Pa, 0.75 torr), which is about 1/6 the pressure on Mars or 1/1000 the pressure on Earth. This low pressure minimizes the drag force on the capsule while maintaining the relative ease of pumping out the air from the tube. The efficiency of industrial vacuum pumps decreases exponentially as the pressure is reduced (Figure 13), so further benefits from reducing tube pressure would be offset by increased pumping complexity.
(P. 24)
——————

Overcoming the Kantrowitz Limit

Whenever you have a capsule or pod (I am using the words interchangeably) moving at high speed through a tube containing air, there is a minimum tube to pod area ratio below which you will choke the flow. What this means is that if the walls of the tube and the capsule are too close together, the capsule will behave like a syringe and eventually be forced to push the entire column of air in the system. Not good.

Nature’s top speed law for a given tube to pod area ratio is known as the Kantrowitz limit. This is highly problematic, as it forces you to either go slowly or have a super huge diameter tube. Interestingly, there are usually two solutions to the Kantrowitz limit – one where you go slowly and one where you go really, really fast.

The latter solution sounds mighty appealing at first, until you realize that going several thousand miles per hour means that you can’t tolerate even wide turns without painful g loads. For a journey from San Francisco to LA, you will also experience a rather intense speed up and slow down. And, when you get right down to it, going through transonic buffet in a tube is just fundamentally a dodgy prospect.

Both for trip comfort and safety, it would be best to travel at high subsonic speeds for a 350 mile journey. For much longer journeys, such as LA to NY, it would be worth exploring super high speeds and this is probably technically feasible, but, as mentioned above, I believe the economics would probably favor a supersonic plane.

The approach that I believe would overcome the Kantrowitz limit is to mount an electric compressor fan on the nose of the pod that actively transfers high pressure air from the front to the rear of the vessel. This is like having a pump in the head of the syringe actively relieving pressure.

It would also simultaneously solve another problem, which is how to create a low friction suspension system when traveling at over 700 mph. Wheels don’t work very well at that sort of speed, but a cushion of air does. Air bearings, which use the same basic principle as an air hockey table, have been demonstrated to work at speeds of Mach 1.1 with very low friction. In this case, however, it is the pod that is producing the air cushion, rather than the tube, as it is important to make the tube as low cost and simple as possible.

That then begs the next question of whether a battery can store enough energy to power a fan for the length of the journey with room to spare. Based on our calculations, this is no problem, so long as the energy used to accelerate the pod is not drawn from the battery pack.

This is where the external linear electric motor comes in, which is simply a round induction motor (like the one in the Tesla Model S) rolled flat. This would accelerate the pod to high subsonic velocity and provide a periodic reboost roughly every 70 miles. The linear electric motor is needed for as little as ~1% of the tube length, so is not particularly costly.

———-

Can it Really be Self-Powering?

For the full explanation, please see the technical section, but the short answer is that by placing solar panels on top of the tube, the Hyperloop can generate far in excess of the energy needed to operate. This takes into account storing enough energy in battery packs to operate at night and for periods of extended cloudy weather. The energy could also be stored in the form of compressed air that then runs an electric fan in reverse to generate energy, as demonstrated by LightSail.

http://www.spacex.com/sites/spacex/files/hyperloop_alpha-20130812.pdf
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numerobis

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Re: The Hyperloop
« Reply #178 on: January 26, 2018, 08:59:27 PM »
Quote
At 0.02 atm, water boils at room temperature. Water leaks (quite common in tunnels) would have to get snuffed out.

So leaked water would vaporize.  What would that mean in terms of system operation?  The small amount of air remaining in the tunnel would be humid?  Would that be an operational problem?

This would be a fully lined tunnel.  Sealed to allow a partial vacuum.  Likely to have big water leak problems?  If there is a leak of any sort it seems that it would be quickly sealed.

What it means is that the huge layer of air-impermeable rock doesn't protect from having to pump out a lot of gas, you'd still need to make it have an impermeable skin (tunnels tend to be wet).

Bob Wallace

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Re: The Hyperloop
« Reply #179 on: January 26, 2018, 10:10:27 PM »
Quote
At 0.02 atm, water boils at room temperature. Water leaks (quite common in tunnels) would have to get snuffed out.

So leaked water would vaporize.  What would that mean in terms of system operation?  The small amount of air remaining in the tunnel would be humid?  Would that be an operational problem?

This would be a fully lined tunnel.  Sealed to allow a partial vacuum.  Likely to have big water leak problems?  If there is a leak of any sort it seems that it would be quickly sealed.

What it means is that the huge layer of air-impermeable rock doesn't protect from having to pump out a lot of gas, you'd still need to make it have an impermeable skin (tunnels tend to be wet).

The Boring tunnels are fully lined with grouted concrete sections.  The tunnel is essentially a concrete tube buried underground.  There's no bare earth exposed.

TerryM

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Re: The Hyperloop
« Reply #180 on: January 27, 2018, 02:10:13 AM »
The recent discussions re. air pressure, or lack thereof, in the tubes brings questions to mind.


The pods are going to require close to atmospheric pressure. Just as water boils at low pressure, so does human blood. It's a problem that's been successfully dealt with in high altitude passenger planes, but it will add complexity, weight, and cost to pod construction.


Has anyone shown what type of compressor the pods will be utilizing? The exhaust from these must necessarily become the input for all following pods. It would seem as though a very large scoop would be required in order to access enough of the rarified atmosphere to provide the high pressure required to elevate the pod. Wouldn't such a scoop have an adverse effect on streamlining?


Final question.
Is the entire tube evacuated or are their airlocks throughout the run? Zipping through airlocks at speed must create difficulties, but otherwise a failure at any point would be catastrophic for everyone in the tube. Imagine the wind that would rush through the structure should a single airlock fail. Imagine being in a pod at 700 mph suddenly being buffeted by beyond hurricane speed wind?


Terry

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Re: The Hyperloop
« Reply #181 on: January 27, 2018, 02:57:07 AM »
Airliners are pressurized.

TerryM

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Re: The Hyperloop
« Reply #182 on: January 27, 2018, 03:33:28 AM »
Airliners are pressurized.
The pod, operating in a vacuum will also require pressurization.
Terry

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Re: The Hyperloop
« Reply #183 on: January 27, 2018, 04:26:25 AM »
Airliners are pressurized.
The pod, operating in a vacuum will also require pressurization.
Terry

Exactly.  The pods will be pressurized when in the stations by simply opening the door.  As the pod travels additional air can be pulled from the tube to maintain pressure.

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Re: The Hyperloop
« Reply #184 on: January 27, 2018, 04:30:57 AM »
The Boring tunnels are fully lined with grouted concrete sections.  The tunnel is essentially a concrete tube buried underground.  There's no bare earth exposed.

Concrete is NOT airtight. It leaks like crazy, especially at the levels of vacuum they are talking about (100 pa). So we still need that steel tube, even inside an bored tunnel.

Which brings up an additional problem of what to do if the steel tube gets damaged deep under a mountain (after some catastrophic accident). How are you going to replace that section ?
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Re: The Hyperloop
« Reply #185 on: January 27, 2018, 05:33:05 AM »
The approach that I believe would overcome the Kantrowitz limit is to mount an electric compressor fan on the nose of the pod that actively transfers high pressure air from the front to the rear of the vessel. This is like having a pump in the head of the syringe actively relieving pressure.

It would also simultaneously solve another problem, which is how to create a low friction suspension system when traveling at over 700 mph. Wheels don’t work very well at that sort of speed, but a cushion of air does. Air bearings, which use the same basic principle as an air hockey table, have been demonstrated to work at speeds of Mach 1.1 with very low friction. In this case, however, it is the pod that is producing the air cushion, rather than the tube, as it is important to make the tube as low cost and simple as possible.

Oh, man. There are just so many issues with these statements, it is hard to know where to begin.

If you want to use the air taken in to lift up the entire pod, that compressor need to increase the pressure from 100 Pa to about sea-level pressure (100,000 Pa), so it can actually provide some 'pressure' to the bottom of the pod. You are going to need a hell of a compressor for that.
And they want to power that compressor from a battery ?

And about that compressor, if it is to 'suck in' 100 Pa air, it needs to run at insane RPMs. At that pressure it needs to run at least 10 times faster than a jet engine. And if a blade would come off, it will easily penetrate the 3 cm of steel of the tube, causing a catastrophic breakdown of the system.

Either way, they should at least TEST the heck out of a system like that. Like, build a pod with that compressor in front, create a vacuum tube of 100 Pa, long enough to test the pod behavior under 0.8 MACH speeds, and at a realtime scale (not the smaller versions they are testing with now).
They are going to need a MUCH longer test tube than the 3/4 mile tube they use now.

And then there is the issue of penetration of the tube leading to a complete and catastrophic failure (death) of anyone anywhere in the tube at the time.

Here is a good overview of the issues that have so far been COMPLETELY ignored by the Hyperloop guys :



If you still like the Hyperloop, I have a solar road to sell to you.
« Last Edit: January 27, 2018, 06:44:17 AM by Rob Dekker »
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Re: The Hyperloop
« Reply #186 on: January 27, 2018, 07:07:56 AM »
Quote
Concrete is NOT airtight.

And if the concrete sections are coated with an air tight substance?

Rob, there's a large number of engineers working on the various 'loop projects.  It's probably best to assume that not all are incompetent.  Some of them are Boeing engineers (the airplane company), some are SpaceX, and others are full time employees of high level engineering and manufacturing firms.

There may be a fatal flaw that will mean that the 'loop will never work but there's an awful lot of brainpower acting if there's a good chance it will. 

We don't know if Boring will be able to bring down the time to dig and cost of tunnels.  Let's let that play out a bit.

We don't know how the pod will operate at higher speeds.  How about we wait until there's enough tube to test it out?

Quote
Here is a good overview of the issues that have so far been COMPLETELY ignored by the Hyperloop guys

How do you know that?  Are you privy to the engineering meetings?  Do you think people involved in the various projects have sealed themselves off from Youtube?



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Re: The Hyperloop
« Reply #187 on: January 27, 2018, 08:15:38 AM »
Either way, they should at least TEST the heck out of a system like that. Like, build a pod with that compressor in front, create a vacuum tube of 100 Pa, long enough to test the pod behavior under 0.8 MACH speeds, and at a realtime scale (not the smaller versions they are testing with now).
They are going to need a MUCH longer test tube than the 3/4 mile tube they use now.
Yeah, and larger. Adding image below.
Quote
The tube size will need to be around twice as large as originally proposed by the Tesla/SpaceX team. The tube diameter is closely tied to the maximum speed the pod travels at.

The main reason for using a vacuum pump on a heat pump installation, is to evaporate and withdraw water from the system, you need at least 500 microns of vacuum. 100Pa is ~750 microns. Lower micron numbers mean a stronger vacuum. 0 microns is a perfect vacuum while 760,000 microns is the measurement of a space with no vacuum at sea level. The main reason for leakage in HVACs is often the copper flare flanges. Stressed installers often fail on those and eventually the refrigerant will leak out. And that is a brass nut tightening on the copper flange itself. That copper flange needs to be perfectly made and the flare fitting must be perfect. Still they can leak. The larger pipes on domestic heat pumps are often 3/8-1/2 inch. Rather thin and they dont have pods at supersonic speeds travelling inside them. Only refrigerant at high pressure.

Edit; Maybe I should point out the additional reason a bit better. If you have the time, you can vacuum the system and leave it for an hour or so, then check the vacuum again. You want to see zero movement on the manometer. That's a simple first test that many HVAC engineers never does because it takes time. A lot of, not so serious, installers never even use a vacuum pump, they just pressurize the system. Another step that is rarely performed on domestic heat pump installations, is to check (and if needed re tighten) the nuts after a period of operation. If you do those simple steps and use a sniffer to check for leaks after installation, then hold your thumbs that there's not a manufacturing error in the rest of the piping. Which do happen occasionally.

I would really like to see a real world installation of the Hyperloop that can maintain 750 microns with a pod travelling though at mach 0.8. This would then have to be done many, many times over an extended period without any failiures.
« Last Edit: January 27, 2018, 09:14:47 AM by Sleepy »
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Rob Dekker

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Re: The Hyperloop
« Reply #188 on: January 27, 2018, 08:54:47 AM »
Quote
Concrete is NOT airtight.

And if the concrete sections are coated with an air tight substance?

Bob, there is a reason why they need 3 cm steel tube to keep the risk of tube collapse at a minimum. You are not going to prevent that collapse with a 'tight substance' somehow 'coated' to the concrete. Do you have any idea how much 100,000 Pa pressure really is and what it can do to a large surface ? Please read the comment that Sleepy just posted, on what it takes to seal a vacuum chamber.

Quote
Rob, there's a large number of engineers working on the various 'loop projects.  It's probably best to assume that not all are incompetent.  Some of them are Boeing engineers (the airplane company), some are SpaceX, and others are full time employees of high level engineering and manufacturing firms.

I know. But we don't hear too much from these engineers, do we ?

All we hear about is the hype from marketing people, who are unrealistically optimistic about this project, and no answers to some very basic challenges as outlined by thunderf00t in the video I posted above.
« Last Edit: January 27, 2018, 09:37:06 AM by Rob Dekker »
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Sleepy

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Re: The Hyperloop
« Reply #189 on: January 27, 2018, 09:24:57 AM »
Rob, openmdao is an open souce project, that's were the above image comes from.
http://openmdao-plugins.github.io/Hyperloop/baseline.html
There's a LOT more useful numbers in that documentation.
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Re: The Hyperloop
« Reply #190 on: January 27, 2018, 09:48:41 AM »
I must say, the boring company idea of digging smaller tunnels faster makes some sense, but the hyperloop with its vacuum and zipping pods on air cushions is totally batshit crazy from a technical perspective, with all respect to Elon. I haven't considered some of the details before. (Thank you all). I am certain that if this does get built somewhere, its details will be far different.

Sigmetnow

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Re: The Hyperloop
« Reply #191 on: January 27, 2018, 03:10:35 PM »
...
If you want to use the air taken in to lift up the entire pod, that compressor need to increase the pressure from 100 Pa to about sea-level pressure (100,000 Pa), so it can actually provide some 'pressure' to the bottom of the pod. You are going to need a hell of a compressor for that.
And they want to power that compressor from a battery ?

And about that compressor, if it is to 'suck in' 100 Pa air, it needs to run at insane RPMs. At that pressure it needs to run at least 10 times faster than a jet engine. And if a blade would come off, it will easily penetrate the 3 cm of steel of the tube, causing a catastrophic breakdown of the system.
...

Musk again:
Quote
Hyperloop Passenger Capsule

The maximum width is 4.43 ft (1.35 m) and maximum height is 6.11 ft (1.10 m). With rounded corners, this is equivalent to a 15 ft2 (1.4 m2) frontal area, not including any propulsion or suspension components.

The aerodynamic power requirements at 700 mph (1,130 kph) is around only 134 hp (100 kW) with a drag force of only 72 lbf (320 N), or about the same force as the weight of one oversized checked bag at the airport.
Quote
The air processing occurs as follows (Figure 10 and Figure 11) (note mass counting is tracked in Section 4.1.4):
Hyperloop Passenger Capsule
1. Tube air is compressed with a compression ratio of 20:1 via an axial compressor.
2. Up to 60% of this air is bypassed:
a. The air travels via a narrow tube near bottom of the capsule to
the tail.
b. A nozzle at the tail expands the flow generating thrust to mitigate
some of the small amounts of aerodynamic and bearing drag.
3. Up to 0.44 lb/s (0.2 kg/s) of air is cooled and compressed an additional
5.2:1 for the passenger version with additional cooling afterward.
a. This air is stored in onboard composite overwrap pressure vessels.
b. The stored air is eventually consumed by the air bearings to
maintain distance between the capsule and tube walls.
4. An onboard water tank is used for cooling of the air.
a. Water is pumped at 0.30 lb/s (0.14 kg/s) through two intercoolers (639 lb or 290 kg total mass of coolant).
b. The steam is stored onboard until reaching the station.
c. Water and steam tanks are changed automatically at each stop.
5. The compressor is powered by a 436 hp (325 kW) onboard electric
motor:
a. The motor has an estimated mass of 372 lb (169 kg), which
includes power electronics. ...

Musk’s SpaceX designs, builds and operates rocket engines that control super-compressed, hyper-cooled propellant and lift tons of weight through the shock of atmospheric Max Q supersonics and on to the vacuum of space.  And survive re-entry forces, to land back on earth.  Repeatedly.  You really think you know more than they do?  Really?

People who say it cannot be done should not interrupt those who are doing it.

Shared Humanity

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Re: The Hyperloop
« Reply #192 on: January 27, 2018, 04:05:53 PM »
I must say, the boring company idea of digging smaller tunnels faster makes some sense, but the hyperloop with its vacuum and zipping pods on air cushions is totally batshit crazy from a technical perspective, with all respect to Elon. I haven't considered some of the details before. (Thank you all). I am certain that if this does get built somewhere, its details will be far different.

And if it ever gets built, it will rarely be duplicated but merely an attraction for tourists who want to ride it kind of like the arch in St. Louis.

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Re: The Hyperloop
« Reply #193 on: January 27, 2018, 04:18:25 PM »
I must say, the boring company idea of digging smaller tunnels faster makes some sense, but the hyperloop with its vacuum and zipping pods on air cushions is totally batshit crazy from a technical perspective, with all respect to Elon. I haven't considered some of the details before. (Thank you all). I am certain that if this does get built somewhere, its details will be far different.
Yes, but the idea is beautiful isn't it? ;)
Here are some other thoughts from a recent BBC podcast, Tech Tent and the first 8 minutes or so:
http://www.bbc.co.uk/programmes/w3csvrvg
Anita Sengupta says that everything is on track for the first commercial operation in 2021 with 700mph or 1127km/h. Maybe she never read that NASA study above?

Gareth Dennis, a railway engineer:
For high-speed rail, the curves have to be 10km long, and that's only at 200mph to 250mph. Hyperloop's going to be hurtling along at 700mph so the track will almost have to be dead straight.

Dr Colin Brown from the Institution of Engineering: The engineering challeges are absolutely enormous. Thermal expansion is one of the real world classic problems. And a further if, do we want to ride it?

I'm going too bookmark this post and check back in 2021. With a reservation, If I'm still alive.
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Bob Wallace

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Re: The Hyperloop
« Reply #194 on: January 27, 2018, 05:40:21 PM »
Quote
we don't hear too much from these engineers, do we ?

We don't.  But they continue to work on the project without pay.  Why would they continue to do so if they felt the idea would never work?

Quote
For high-speed rail, the curves have to be 10km long, and that's only at 200mph to 250mph. Hyperloop's going to be hurtling along at 700mph so the track will almost have to be dead straight

If in tunnels any needed turns can be extremely gradual.  If there is a need for a sharp turn speed can be dropped and the turn banked.

Quote
do we want to ride it?

I certainly do.  After it has been proven out (if it is).  The general plan is to run a system for a year hauling only freight before a human would be allowed to ride. 

I find myself uncomfortable in supporting the Hyperloop because I do not have the engineering background to deal with some of the issues.  But I look at the people who are involved and this isn't one guy with a wild idea.  There are lots of experienced engineers and lots of university engineering departments spending time on developing the idea.

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Re: The Hyperloop
« Reply #195 on: January 27, 2018, 06:39:50 PM »
It seems very odd that the plan is to store steam in the pod.  I guess they can't condense it because they have no adequate heat sink.  Pressurized steam is very dangerous stuff. I guess they can't release it into the tube because of the hazards of too much water vapor in the tube. 

Buildup of excess heat in the pod looks like it could be a big problem.  Maybe they'll need to have a load of dry ice at each stop.  Can't vent the CO2 into the pod, buildup of CO2 could be an issue even without that.  But a system to vent the CO2 to the rear into the tube might work.

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Re: The Hyperloop
« Reply #196 on: January 27, 2018, 09:18:42 PM »
...
Gareth Dennis, a railway engineer:
For high-speed rail, the curves have to be 10km long, and that's only at 200mph to 250mph. Hyperloop's going to be hurtling along at 700mph so the track will almost have to be dead straight.

Dr Colin Brown from the Institution of Engineering: The engineering challeges are absolutely enormous. Thermal expansion is one of the real world classic problems. And a further if, do we want to ride it?
...

 I refer you, once again, to Elon Musk’s white paper on the Hyperloop.

Quote
4.4. Route
The Hyperloop will be capable of traveling between Los Angeles and San Francisco in approximately 35 minutes. This requirement tends to size other portions of the system. Given the performance specification of the Hyperloop, a route has been devised to satisfy this design requirement. The Hyperloop route should be based on several considerations, including:
1. Maintaining the tube as closely as possible to existing rights of way (e.g., following the I-5).
2. Limiting the maximum capsule speed to 760 mph (1,220 kph) for aerodynamic considerations.
3. Limiting accelerations on the passengers to 0.5g.
4. Optimizing locations of the linear motor tube sections driving the capsules.
5. Local geographical constraints, including location of urban areas,
mountain ranges, reservoirs, national parks, roads, railroads, airports, etc. The route must respect existing structures.
For aerodynamic efficiency, the velocity of a capsule in the Hyperloop is typically:
300 mph (480 kph) where local geography necessitates a tube bend radii < 1.0 mile (1.6 km)
• 760 mph (1,220 kph) where local geography allows a tube bend > 3.0 miles (4.8 km) or where local geography permits a straight tube.
These bend radii have been calculated so that the passenger does not experience inertial accelerations that exceed 0.5g. This is deemed the maximum inertial acceleration that can be comfortably sustained by humans for short periods. To further reduce the inertial acceleration experienced by passengers, the capsule and/or tube will incorporate a mechanism that will allow a degree of ‘banking’.

http://www.spacex.com/sites/spacex/files/hyperloop_alpha-20130812.pdf#page40

Route maps, with bend radii mapped to the curves, at the link!

Quote
Specially designed slip joints at each stations will be able take any tube length variance due to thermal expansion. This is an ideal location for the thermal expansion joints as the speed is much lower nearby the stations. It thus allows the tube to be smooth and welded along the high speed gliding middle section.
http://www.spacex.com/sites/spacex/files/hyperloop_alpha-20130812.pdf#page40

Come on, I know, ”but it’s California!” — the paper does have lots of cool stuff in it. ;)
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Re: The Hyperloop
« Reply #197 on: January 27, 2018, 09:26:53 PM »
And why do you keep repeating that, Sig?
We have access to the same Internet here in Europe and you are ignoring a lot of comments. As a small example from this thread here's my reply #312 including an image from that old hyperloop white paper:
https://forum.arctic-sea-ice.net/index.php/topic,856.msg139689.html#msg139689
And here's your reply #330 to Bob:
https://forum.arctic-sea-ice.net/index.php/topic,856.msg139853.html#msg139853
Do you think I've read that paper? Do you think Bob has? I know I have and I think Bob has.

Elon offers many quotes:
Quote
I don't spend my time pontificating about high-concept things; I spend my time solving engineering and manufacturing problems.

It's OK to have your eggs in one basket as long as you control what happens to that basket.

Elon Musk
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Re: The Hyperloop
« Reply #198 on: January 27, 2018, 09:41:51 PM »
And why do you keep repeating that, Sig?
We have access to the same Internet here in Europe and you are ignoring a lot of comments. As a small example from this thread here's my reply #312 including an image from that old hyperloop white paper:
https://forum.arctic-sea-ice.net/index.php/topic,856.msg139689.html#msg139689
And here's your reply #330 to Bob:
https://forum.arctic-sea-ice.net/index.php/topic,856.msg139853.html#msg139853
Do you think I've read that paper? Do you think Bob has? I know I have and I think Bob has.

Elon offers many quotes:
Quote
I don't spend my time pontificating about high-concept things; I spend my time solving engineering and manufacturing problems.

It's OK to have your eggs in one basket as long as you control what happens to that basket.

Elon Musk

Because I keep seeing comments bringing up potential problems, sounding like they are the first person to have thought of them, but which have already been addressed in that paper? 
People who say it cannot be done should not interrupt those who are doing it.

Sleepy

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Re: The Hyperloop
« Reply #199 on: January 27, 2018, 09:50:33 PM »
Feel free to ignore other engineers out there in the real world if you wish. You have repeatedly posted that five year old paper. I've already read it.
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