SAN FRANCISCO — Commuters in Missouri face the prospect of trading their grinding highway slog for a 700-mph hyperloop that is still in testing and would carry high-speed rail type prices....
https://www.usatoday.com/story/tech/2018/01/30/missouri-ready-700-mph-commutes/1078842001/
Hyperloop, or just more hyberbole?
The article implies use of I-70 ROW. That will get thrown out quickly since a path designed for 70 MPH will generate excessive lateral and vertical forces for passenger comfort and perhaps for safety. The corridor would work, but will require substantial ROW acquisition costs plus bridges and tunnels.
Hype unless someone comes up with billions of dollars. It is very difficult for an entity that has to recover its capital costs to compete with cheap highway and air systems that do not recover their costs.
I'm only surprised USA Today didn't mention the use of 'safe' thorium-cycle power to run it.
This has the hallmarks, to me, of some Elon Musk propaganda reaching a particularly gullible target.
Or perhaps a story published two months early.
Where is the perpetual motion machine?
Never too old to have a happy childhood!
BaltACD Where is the perpetual motion machine?
Johnny
I imagine he'll get YUGE government grants to build one. That's what he's all about, isn't it?
54light15 I imagine he'll get YUGE government grants to build one. That's what he's all about, isn't it?
I know that's what I'M all about, fer shure!!!
Ed
Talk in the St. Louis media, is the potential to merge the St. Louis and Kansas City metro areas. At these speeds it could be done. Not just this city pair, but nationwide, such an advance in transportation could help alleviate rural blithe and unemployment in said areas.
I don't think any of us has the expertise to blatantly state this can't be done.
If this was some proposal to build a high tech steam engine that pulls neuvo Pullman cars at 700 mph, you guys would be all over it.
BLS53I don't think any of us has the expertise to blatantly state this can't be done.
I for one have the expertise, and the experience, to blatantly state it's dumb, dumb, dumb, and shouldn't be tried 'as touted in the story'. Perhaps you could get those modules to go that fast, in a perfect world under ideal conditions with ideal equipment, at enormous grading and construction expense. Wouldn't be long before you killed someone in them, with those running clearances close to the ground. We will leave all the wonderful neighbor objections and permits and government stuff and so forth out; I say because it's unnecessary to look at the idea seriously much further, but you are welcome to argue the case on engineering merits if you can find them.
You can't even spell 'nouveau' and you're questioning expertise? I'll be the first to state that any proposal to pull Pullman cars with the kind of steam you (or Davidson Ward) probably have in mind at a quarter that speed would be silly, even though I could probably tell you how to design and build it 'in principle' (for 175mph, that is). I wouldn't even haul Pullmans at 120mph with reciprocating steam, no matter how good. That ship sailed and sank long ago. Modern steam for high speed involves things like a bottoming combined cycle, or as the French practice it today, nuclear reactions.
Maybe he meant nuevo Pullman cars? I say Muy Bueno!
Nobody ever talks about Hyperloop throughput. Even Musk. If it takes, say 5 minutes to load and launch the six passenger vehicle before the next one is ready ot load, then that's only 72 people an hour per tube.
A highway can do 1900 vehicles and hour.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
oltmanndIf it takes, say 5 minutes to load and launch the six passenger vehicle before the next one is ready ot load, then that's only 72 people an hour per tube.
When I was studying PRT at Princeton, it was assumed that there was substantial parallel loading and 'marshaling' of the individual modules, so that actual guideway occupancy much closer to theoretical capacity could be reached.
Some of the advantage for the 'transport system' elements goes away if you have to use a reduced-pressure tube, because the roughing pumps, let alone finishing pumps, for all the separate introductions at a high-volume station start to add up to considerable operating cost. A common assumption seemed to be that the electricity fairy's cousin, the vacuum fairy, would provide ample 'nothing' at any degree of scale-up.
Another fun issue is, even with the counterpart of CBTC, what's a proper noncontact following distance for controlled noncontact vehicles at 700mph? And if they are brought selectively in contact for optimized emergency braking, under what 'emergency' conditions do the fancy approach-speed matching and energy transfer algorithms remain reliably fully operational?
Trust me when I say much of this was done to death in the '70s and a great deal of relevant basic physics has not changed in ways that care about Moore's-Law reduction in control technology costs or processing power.
Although I feel this idea is just industrial strength pie-in-the-sky dreaming, I do wonder. Can a 700 mph bullet carrying passengers and freight(?!) deal with the curves and hills prevalent on every piece of Missouri that I’ve seen up close? Or does it need a straight, flat tube? If it’s darned near impossible to build a water or gas pipeline without the occasional leak, how do you build a high-test tube to be air tight, especially allowing for what must be some pretty high pressure conditions?
Thanks to Chris / CopCarSS for my avatar.
Murphy SidingCan a 700 mph bullet carrying passengers and freight(?!) deal with the curves and hills prevalent on every piece of Missouri that I’ve seen up close? Or does it need a straight, flat tube?
It doesn't need to be quite as 'straight and flat' (actually chord of arc) as some of the vacuum subway proposals 50 years or more ago; those were built as far underground in places as microwave relays were placed above ground for the same distance to give straight pathing on a round Earth.
It is relatively easy to calculate maximum lateral acceleration on vehicles entering and then sustaining curves, both vertical and transverse. At 700mph even fairly gentle 'nap of the earth' following, or directional change, will have to be slow. Technically the requirements fall off some as you approach stations where all traffic stops, as longitudinal acceleration becomes a factor that affects achievable speed even at some distance. But, as for much current high-speed rail construction, you're basically talking about almost the whole of the line being either in tunnels or cuts or on substantial fills/bridges. Which of course is one big reason the Boring Company has Godot and is doing planning to increase TBM speeds. It helps of course if your stations are essentially at the apices of any required compass-direction changes. If it’s darned near impossible to build a water or gas pipeline without the occasional leak, how do you build a high-test tube to be air tight, especially allowing for what must be some pretty high pressure conditions? This is actually one of the least of the worries, as we are talking about subatmospheric pressure throughout - no more than about 14.7psi radially inward and on a cylindrical guideway substantially balanced, well within hoop stress of even fairly light construction. I presume there will be disc burst valves in case the vacuum is broken with vehicles still moving at high speed causing compression waves, but it remains to be seen whether more serious forms of pressure or shock relief would be needed. I suspect it is easy to incorporate impermeable membranes or external sealants in a concrete tube structure to make it effectively vacuum-resistant even after many years of environmental exposure; I can certainly think of materials and ways to accomplish what is needed, so why would Musk's team have more difficulty? The deeper issue is how you make the structure relatively lightweight, inexpensive enough to construct and place rapidly in its 'infrastructure', and still be tolerant of the vehicle pad loads for presumably somewhat unbalanced loading and shifts at peak velocity. In my opinion relatively small deflections or cumulative effect of temperature may cause geometric difficulties leading to the equivalent of a 'head crash' on a hard drive; the resulting forces cannot cause the vehicle to execute even slight deflection either at its nose or centroid. I won't discuss terrorism, but it causes bigger problems here than diversion of concentrated H2O2 did for the Oxford Cycle.
If it’s darned near impossible to build a water or gas pipeline without the occasional leak, how do you build a high-test tube to be air tight, especially allowing for what must be some pretty high pressure conditions?
This is actually one of the least of the worries, as we are talking about subatmospheric pressure throughout - no more than about 14.7psi radially inward and on a cylindrical guideway substantially balanced, well within hoop stress of even fairly light construction. I presume there will be disc burst valves in case the vacuum is broken with vehicles still moving at high speed causing compression waves, but it remains to be seen whether more serious forms of pressure or shock relief would be needed. I suspect it is easy to incorporate impermeable membranes or external sealants in a concrete tube structure to make it effectively vacuum-resistant even after many years of environmental exposure; I can certainly think of materials and ways to accomplish what is needed, so why would Musk's team have more difficulty?
The deeper issue is how you make the structure relatively lightweight, inexpensive enough to construct and place rapidly in its 'infrastructure', and still be tolerant of the vehicle pad loads for presumably somewhat unbalanced loading and shifts at peak velocity. In my opinion relatively small deflections or cumulative effect of temperature may cause geometric difficulties leading to the equivalent of a 'head crash' on a hard drive; the resulting forces cannot cause the vehicle to execute even slight deflection either at its nose or centroid.
I won't discuss terrorism, but it causes bigger problems here than diversion of concentrated H2O2 did for the Oxford Cycle.
I am wondering what the human tolerable acceleration and deceleration 0-700-0 is in both time and distance. Just because the 'vessel' can go 0-700-0 doesn't mean that paying humans would find such G loadings accepable.
Godot? So they are 'Waiting for Godot'...seems appropriate.
Don't just sit there, buy a flamethrower!
These are seated pax, so accelerations comparable to modern high-speed trains are acceptable, and very likely those encountered in comparable road vehicles might be endurable in the 'pod' provided, with acceleration having a higher 'comfort' threshold than deceleration. The likely profile (if I were doing something like this) would involve initial slow ramp of acceleration rate to about 1.5fpsps, then sustained acceleration as high as 1g (call it 32fpsps), all transitions carefully managed to minimize jerk. I do not have experiential data for the best transition from high acceleration to sustained cruise, but it should not involve much more than a few seconds. Call the speed 1025fps for convenience and you can work out any desired acceleration profile by sequential addition; this gives a little over half a minute at 1g peak; even at transit-car acceleration all the way it's under 7 minutes. Peak decel will be somewhat less, and while it's a bit involved to figure distance-to-speed directly, it's easy just to add the distances for fixed times under acceleration (s=1/2at^2)and sum them for an approximation.
Here is a link to a paper
As an interesting 'aside' in this respect, remember that you can get within a relativistic hair of lightspeed by accelerating at 1g for less than a year...
MiningmanGodot? So they are 'Waiting for Godot'...seems appropriate.
Very appropriate when you know it's their name for the TBM they bought. I'm still impressed with the name they gave their 'tunneling research division'.
My recollection is that jet airliners typically accelerate at about 1/3rd g, so that woulld get up to 700MPH in about 100 sec and traveling about 10 miles in the process. Same in reverse for normal deceleration. Emergency deceleration is another story, 1g deceleration will take 22 seconds to bring the pod to a stop, covering close to 1.5 miles. Higher deceleration rates sound like a really bad idea for the general public, so throughput might be 4 pods per minute at best.
I'm getting the impression that Elon Musk was thinking this would be a scaled up Matterhorn Bobsled.
The "tubes" have me a bit puzzled as well. Above ground tube would have to have some sort of expansion/compression bellows at regular intervals. Being under vacuum, they don't have the internal pressure against buckling as with a pipeline, so they will need some sort of stiffening. Underground would relieve much of the temperature variation issues as with welded rail in a long tunnel, but keeping it vacuum tight will be a maintenance nightmare. They would almost certainly need at least three bores so that one could be out of service for maintenance.
The final question is how much does 700MPH buy you if it takes an hour to get to/from the station?
OvermodAnother fun issue is, even with the counterpart of CBTC, what's a proper noncontact following distance for controlled noncontact vehicles at 700mph? And if they are brought selectively in contact for optimized emergency braking, under what 'emergency' conditions do the fancy approach-speed matching and energy transfer algorithms remain reliably fully operational? Trust me when I say much of this was done to death in the '70s and a great deal of relevant basic physics has not changed in ways that care about Moore's-Law reduction in control technology costs or processing power.
I'm good with parallel loading/unloading. Not so good with vehicle spacing/fleeting. If you functionally "train" the vehicles, you still need spacing between the "trains" for accel/decel. I don't think aircraft carrier catapult and arresting wire accel/decel would be much fun. You could probably beat the tranist standard of 2 or 3 mph/sec, though. Maybe 1/3G would be okay? Who knows.
Like you said, it's just 400 year old kinematics.
When I was working with high-speed PRT I used a peak acceleration of 10fpsps, which correlates reasonably with 1/3g. Note how much smaller this is than the figure for a Tesla P100 in Ludicrous+ mode. Leaving proper safety concerns aside for a moment (see below) since vehicles accelerating at the same rate with intervehicle proportional control can assume similar headway to those at steady speed, there can be a 'ripple' in headway within the tube so that only at times of differential acceleration are there longer intervehicle or inter'train' spacings.
What was to happen, at least some of the time, in practice was that vehicles 'fleeting' over a given section of the fixed guideway network would physically come into contact and snub up to each other; in some cases they would physically couple and then remain locked as long as possible. This allowed a fleeted consist to accelerate and move as if it were a single vehicle, with appropriate aerodynamics,shock management, etc. if within an evacuated tube or other form of fixed guideway.
The joker, of course, is what happens if a pad-based Hyperloop car suffers sudden attitude or structural change that bangs it into the tube wall and might essentially stop it near short. "Safe" control couldn't predict which car would suffer such an instability, and so would need to provide safe following distance for each vehicle that was not specifically incorporated into a train; you can then get a bound on throughput for one tube by summing all the delays, calculated nose to nose to account (unlike NAJPTC) for nonzero car length and using the 'crash stop' minimum distance, to get a bound on the "critical path" value. That is not small for the vehicle size Musk is using, but there is another issue.
When calculating maximum emergency deceleration, I think it is not immoral to use emergency restraint and energy-absorbing devices as part of the solution for the passengers. In the original planning for 225mph passenger trains in the early '70s, one scenario was the train coming to a stop essentially constrained to a straight line with a fixed obstruction at the end, and net even of controlled crush at the nose this would result in very high deceleration of passengers to keep them out of the seatback ahead. This is further complicated by considerations of aortic dissection and other high-speed trauma. But if the torso of the passenger is continually decelerated through about 33 inches of properly-counteracting foam or other conformal structure, they can be brought to rest from that speed alive.
I see no way in Hades that could be done from anywhere near 700mph and there are plenty of opportunities for clever folks to find out just how fast a Hyperloop car could be made to come to a stop.
I still think that by the time you get done paying for all this stuff, hybrid small airliners with autonomic control in an implemented FAA regional system, with regional rail and then Uber/Lyft-style last-few-miles with fully autonomous control, represents both a far better and far more easily implemented solution, with comparable end-to-end times, than anything a comparable investment in Hyperloop would do. If you want very high speed for your infrastructure dollar, build one of Arnold Miller's speed-of-sound-in-hydrogen subways ... or even Salter's version from the '60s, not an overpriced PRT kludge.
Or you could bring back Roadtowns for new development...
Overmod . A description of what happens on crowed road ways. Or as some of my friends call it an accordian effect.
blue streak 1Overmod . A description of what happens on crowded roadways. Or as some of my friends call it an accordian effect.
What's fun is to do a mathematical model of why the slowing and speeding up persists sometimes a very long time after a blockage in traffic flow has been relieved, in what ought to be clear traffic lanes. Almost as fun as modeling why buses so often run in packs...
Overmod Or you could bring back Roadtowns for new development...
"Keep them rolling!"
The story had interesting examples of sabotage and accidents. Also interesting in predicting the general location of I-5 30 years before it was built.
erikem"Keep them rolling!"
Actually, I was thinking of something far cooler than Mr. Heinlein's idea: Edgar Chambless' ideas from circa 1910, one of America's counterparts to Italian Futurism. Turn the Ville Radieuse on its side, and make it work right.
If you are going to associate real-estate development with 'take rate' for high-speed and low-speed coordinated transit, you can't do much better. In my not-so-humble 'higher'-architectitiptitoploftical opinion...
"architectihoo ha?" Sound like weapons-grade Balonium.
54light15"architectihoo ha?" Sound like weapons-grade Balonium.
It's a pun on a quote from Finnegan's Wake.
Slainte!
54light15Slainte!
Sláinte agad-sa!
Look who just got "verbal" approval for the Hyperloop, amongst other things.
http://www.bbc.com/news/technology-40677604
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