Relative to the frame of reference, it seems to me the sparse particles would be travelling closer to the speed of the craft than the dense particles.
The "density front" travels at exactly the speed of sound, but it consists of nearly static particles (not static from the frame of reference, from the frame of reference they are moving backward at nearly the speed of sound), these static particles are the relevant V.
The sparse particles just in front of the dense ones are accelerating to get more sparse. From the perspective of the reference frame, they are therefore moving 'backward' at slightly less than the speed of sound, making there relative velocity closer to that of the reference frame. So lower density and lower velocity. and that doesn't even account for additional compression which I don't even know enough to do armchair reasoning on.
So, I'm the farthest thing from an expert, but this is why it doesn't seem to make sense to me.
In all seriousness though I'm going through your post to see if you've found a gaping problem =). I don't think there can be different density velocity ratios at any point of displacement in the wave's reference frame because the same net number of particles has to pass through each point or you start making a permanent buildup on one side or the other of that point, which you can't do because in the reference frame of the still air that point is moving at the speed of sound.
A moving point passes by the same number of unique particles at the speed of sound as it would if it were going the speed of turtle (if you ignore thermal dispersion).
"the same net number of particles has to pass through each point"
Agreed: the corollary to the "the sparse particles just in front of the dense ones" is the "sparse ones just behind the next wave of dense ones", which are, in fact, decelerating, or moving backward even closer to the speed of sound than the dense ones relative to the reference frame. So individual particles oscillate back and forth, but net effect is no movement (to the reference frame of the average speed of the particles, which is a third reference frame :-) )
Surely that animation exaggerates how little net molecule displacement occurs. I'm not sure what would cause many of the molecules to reverse direction while in the low-pressure part of the wave.
The pressure (also density) maximum is the velocity maximum.
Shouldn't you put the front of the craft at the pressure minimum and the back of the craft at the pressure maximum? Then the wave would be pushing you along.
The wave won't push you along at the speed of sound; at any point on the wave from the wave's reference frame (the speed of sound) there is a net flow of particles heading the opposite direction, unless your amplitude gets so high that average particle velocity in some places starts to exceed the speed of sound, in which case you don't have a sound wave anymore I don't think.
I agree about the particles moving in the waves frame, but what you are talking about is drag, I think. The pressure gradient still produces a net force on the object. How big it is compared with other forces, such as drag, I have no idea.
The difference between the dense particles just behind the craft with maximal drag and sparse particles just in front, means a pressure differential pushing the vehicle forward
The guy launches rockets and builds electric sports cars ... I tend to think he has a plan. Allowing the speculation to persist might improve that plan but I suspect it was viable on it's own (and perhaps the waiting period was simply to allow some small scale testing to occur).
To be honest that is what my money was originally on.. that or this just being some sort of self-constructed mythology for himself, sort of like free wirelessly transmitted power was for Tesla perhaps (though more 'intentionally' and less 'mistakenly/delusionally').
As time goes on he keeps getting more and more specific with his deadline for going public though. First it was "eventually", then it was "sometime after Tesla is profitable", then it was "sometime later this year", now we've actually got a date to look forward to. I now think that he actually is thinking of something.
You know... this remark got me thinking, and it turns we've been here before as a society, with remarkably similar technology (superficially, at least) and technologists hyping it up a little. Look up Beach Pneumatic Transit - the first New York City subway, in a tube, powered by compressed air. Which is kind of cool: http://en.wikipedia.org/wiki/Beach_Pneumatic_Transit
"A tube, a car, a revolving fan! Little more is required. The ponderous locomotive, with its various appurtenances, is dispensed with, and the light aerial fluid that we breathe is the substituted motor!" -- http://www.columbia.edu/~brennan/beach/chapter2.html
Trains in tubes and promises of dramatic changes in the way people think of transportation! People thought they would be building tubes all over the countryside to move trains around... and then they went and invented the electric-multiple-unit subway train which took off instead. :P
Somewhere, someone is reading this over a data connection going over some fiber that has been pulled through an old unused pneumatic tube mail system that was installed in a subway tunnel.
Or even if he does have a design planned, he might consider "creating other usable designs" as a deliberate side effect of stirring up speculation. He seems to be motivated by saving the world in general more than personally making a lot of money.
All this speculation reminds me of the hype surrounding the Segway launch. I recall it being being touted as a game-changer, a revolution in transportation that would change the way cities were built...
[The Segway] will be to the car what the car was to the horse and buggy (Dean Kamen)[1]
John Doerr, predicted Segway would rack up $1 billion in sales faster than any company in history [1]
The Segway was demonstrably inferior to commonplace alternatives on simple metrics alone: speed, capacity, cost, safety, comfort.
It was only hyped because it was "cool".
If the hyperloop, however it works, can duplicate the capabilities of a high speed rail system in terms of passenger throughput, speed, and waiting time and do so safely at much lower cost then even if was the uncoolest thing in the world it would still be of immense practical benefit.
> The Segway was demonstrably inferior to commonplace alternatives on simple metrics alone: speed, capacity, cost, safety, comfort.
Metrics are like statistics, in that they can also mislead. It's really about the experience in specific contexts.
> It was only hyped because it was "cool".
Actually, it failed because it just looked dorky. (Which Steve Jobs predicted in his secret meeting with Dean Kamen.) Good tech badly marketed sometimes still doesn't sell.
"What does everyone think about the design?" asked Doerr, switching subjects.
"What do you think?" said Jobs to Tim. It was a challenge, not a question.
"I think it's coming along," said Tim, "though we expect—" "I think it sucks!" said Jobs.
His vehemence made Tim pause. "Why?" he asked, a bit stiffly.
"It just does."
"In what sense?" said Tim, getting his feet back under him. "Give me a clue."
"Its shape is not innovative, it's not elegant, it doesn't feel anthropomorphic," said Jobs, ticking off three of his design mantras.
"You have this incredibly innovative machine but it looks very traditional." The last word delivered like a stab.
...
"Screw the lead times. You don't have a great product yet! I know burn rates are important, but you'll only get one shot at this, and if you blow it, it's over."
Dorky was just the icing on top, the reason why it failed was practicality.
It cost many times more than even high end bicycles, without being faster, without being able to be used on streets, without having as much cargo capacity, and while depriving you of exercise.
It cost many times more than a scooter, while being slower, having far less range, less cargo capacity, and not being usable on streets.
And so on.
If it had cost $200 it might have had a chance to find a niche, but at $3k or so it's just a toy.
It cost many times more than even high end bicycles, without being faster, without being able to be used on streets, without having as much cargo capacity, and while depriving you of exercise.
It cost many times more than a scooter, while being slower, having far less range, less cargo capacity, and not being usable on streets.
What you are saying highlights the reason it failed, while missing the point of the device.
It was not for the bicycle use case. It was not meant to be faster or to be used on the streets. You can carry a couple of modest panniers worth of cargo, and touring-bike loads would again be besides the point. It was meant to deprive you of exercise.
The Segway was meant to create a "new" use case and market segment in the same way that the iPhone and iPad did. (You can find plenty of objections analogous to the ones you list for the iPhone and iPad.) In that kind of context, dorky is going to kill you.
at $3k or so it's just a toy.
What Steve Jobs understood was that it's okay to start out as a toy when creating a new market segment. However, you have to be cool enough while being cheap enough. The Segway had a too high a price point and a too low of a cool factor.
Most of the value of air travel is in its speed and thus convenience. Personally I have yet to fly to a destination that was incapable of being reached by automobile. There are circumstances where the tradeoffs stop being worthwhile, but comparing anything "high speed" to the Concorde is a red herring.
Why is this always brought up? I fly several times a month. While the TSA is an annoyance and has silly policies, they have always been curteous and efficient. The only consideration I have for the TSA is that I can't bring knives on the plane and I need an extra 15 minutes for the line. Other than that they are innocuous to me.
I don't find the experience of the TSA remotely like being a criminal. It's rather clear you have no idea what criminals are treated like.
Generally the TSA x-rays my bags looking for weapons and makes me walk through a metal detector, then I go on my way. Sometimes the line is 15-20 minutes, though usually it's less than 5. Sometimes there's a millimeter wave body scanner that some might find intrusive - personally I couldn't care less if a TSA employee sees my junk, and those that object can opt for a pat down. Those that object to being touched might be better served by a therapist than a plane ride.
This objection to flying because of the TSA is a psychological problem on your part and has nothing to do with reality. Unless you are carrying prohibited items - knives, liquids, etc - you will almost never encounter a problem with the TSA. Sure, the rule may be arbitrary and ridiculous, but they are not particularly onerous or oppressive either. I certainly make comments on bad policies and advocate for change. The system is nowhere close to the gestapo crazies seem to make it out to be.
Of course, you're likely psychotically obsessed so this will mean nothing to you, but get some help.
That's nice for you that you don't mind an invasion of privacy and think that those who do need to see a therapist. I love how you pretend to diagnosis mental health issues over the internet, maybe I should get into that game...
Your claim that they do not treat people as criminals because you don't mind or encounter trouble is laughable. Some of us don't have a case of Stockholm Syndrome to sooth the abuse.
Of course as someone who sympathizes with and advocates for your aggressors you won't understand where I am coming from, but get some help.
I can only extrapolate how criminals are treated from how we dealt with "detainees" in Iraq. The biggest difference is that at ECP2 in Fallujah, we only stuck our hands down the pants of people who we were detaining.
You represented that TSA treats you like a criminal, which implies a vastly different type of treatment than what actually occurs.
TSA have always treated me and everyone I know decently. Airport security is basically the same as it was 30 years ago. It's really disgusting and irresponsible to attack the TSA for carefully and respectfully enforcing regulations. I have no problem attacking idiotic regulations and regulators.
I have a lot of anxiety about being trapped—once you enter security it's difficult to justify leaving before your flight, which is inevitably delayed, and all along you have to pay hand over fist just to get the same bottle of water you could have bought for a tenth the price at the gas station outside the airport. Oh, and all of this is on top of the stress of being mistakenly identified as a criminal.
And, of course, there's the taxpayer money wasted—if we're going to employ that many people it may as well be doing something useful rather than attempting to stop all possible methods of bringing down an explosive tin can tens of thousands of feet in the air.
what are the implications of serious damage to the pipe/waveguide? Either explosives from the inside or outside, or just damaging the support struts.
If it's using the air-hockey principle, I'd expect reduced forward pressure to below the limit on which the vehicle can float, so it starts to skid along the ground, hopefully with enough inter-car spacing that you don't get a pileup.
A less catastrophic situation might be, what happens if the pipe has a relatively minor leak due to subsidence or whatever? Just a loss of efficiency, or loss of function?
The Segway hype was so generic it could have been anything: it didn't offer any concrete metric to justify it.
A system allowing to travel LA to SF in 30 minutes, without the hassle involved with air travel, WOULD be revolutionary, regardless of how good or bad is the marketing department of its company.
No one predicted this would be the problem, and indeed most people still haven't come to Graham's conclusion. In that sense, concrete metrics are irrelevant. The hyperloop is just as likely a priori to have some sort of similar fatal flaw. This is the problem with getting too excited about any new particular device; there's too much that can go wrong between zero and revolutionary.
If this is truly the main reason, then I'm sad that we live in the world full of assholes.
> But when he rides the Segwell, they shout abuse from their cars: "Too lazy to walk, ya fuckin homo?"
> Why do Segways provoke this reaction? The reason you look like a dork riding a Segway is that you look smug. You don't seem to be working hard enough.
Can't or are not allowed to? Because Segway sightseeing trips are quite popular in big european cities, and from what I can tell, the devices works very well on both roads and pavements.
Only american tourists do that.
They are courteous and the Segways are silent, but something still irks me about them.
The tourers mostly look quite fit so probably they could just walk instead. Why bring your whole Segway caravan into walking areas of old towns?
Not allowed to, in many US localities. Segways are too fast for sidewalks, posing danger to pedestrians. But they're not fast enough to merge with car traffic on a road.
Where do they travel in European cities? Bicycle paths?
That gives a funny perspective on the "we'll [have to] redesign cities around this!" hype claim...
Regarding seeing them being used by tourists etc. I imagine the prohibition exists when framed in 'this will change everything - everyone will have one!' context, which is different from the reality of 'these are actually rubbish - almost nobody wants one'.
The first mobile phone users looked like smug jerks and show offs as well (What, are you too lazy to walk to a wired phone ? Are you so important that people must be able to contact you at any time ?) , yet the functionality offered was so useful that in the end everybody followed suit.
But you give a major difference: the functionality it offered was so useful.
While I'd love a Segway, it's usefulness is much less than my cellphone to me. Maybe if cities had been redesigned around it, things would be different
For me, the appeal is that I live a 20 minute walk from the train station I use for my commutes. A lot of the time I don't mind that walk, or I take the bus. I don't have a car. A Segway would make the bus uninteresting except in really bad weather - it'd be about as fast and not tie me to the bus schedule. It'd also make dragging shopping around easier.
But those are slight conveniences, and conveniences that are even less of a deal for someone with a car (who'd just drive their shopping home), and that has become less important as time has passed: These days I have a shortcut to a countdown display for my local bus stops on my phone, so while I sometimes have to wait, when leaving home I can wait in my living room and walk out just in time for the bus, and when returning I always know if it's worth waiting for the bus or starting to walk or flag down a taxi. And we get the shopping delivered to our door step, in a one hour time slot every week, and if we forget to order, they automatically put together an order that is ok based on our usual order pattern, so grocery shopping is totally off my radar.
I still think it'd be great if Segway's get to the point where they become accepted, and maybe they still can (around London, there's tons of people on silly looking kick scooters, some of which are motorized, so clearly some people are prepared for alternatives...).
But they'd first become revolutionary if they reach a sufficient level of use displacing cars that it'd change city cores, and that, I'm afraid would take a miracle or a lot of time.
Not everyone can ride a bike. SV 20-somethings seem to not understand that we can't design the whole world around bikes. As you get older the appeal of a bike for transportation to all but the most devoted geriatric athlete diminishes.
"As you get older the appeal of a bike for transportation to all but the most devoted geriatric athlete diminishes."
This just isn't true. The reason that Americans give up cycling as they get older is because it's inconvenient. Plenty of cities in other countries make cycling convenient, so a lot more people do it. Sure, there's a substantial portion of the population (15-20%?) who aren't physically capable of cycling, but that doesn't mean that getting closer to 40% of people commuting on bikes like Amsterdam does is impossible.
If you are going to stick a motor on something, better a bike frame than a podium. Not everyone can stand for as long as they need to get somewhere... The form factor of a bike is far more accommodating than that of a segway.
Funny you should mention glass. Doerr's firm is backing it too through the Glass Collective.
Doerr has been equally bullish about Google Glass. Still, Glass is fast developing a stigma, and it’s not even on the market yet: It’s been called a “Segway for your face.” [1]
The author appears to have confused group velocity (the speed of the wave) with particle velocity (the speed of the air molecules). This is a very basic notion of how waves work -- the waves move, not the medium.
In this case, the wave (and the vehicle) would be moving at the speed of sound, but the air particles they hit wouldn't. They're basically still stationary. There is no magical force to bring them up to the speed of sound before they hit the vehicle. Hence, the drag is not reduced.
I'm a physicist, but by no means an expert on sound. There are more details on how sound actually works on this page: http://mysite.du.edu/~jcalvert/waves/soundwav.htm. A relevant quote: "v [the particle velocity] is much less than the phase [wave] velocity of sound" (note: phase and group velocity are equal for sound in air).
You read it wrong; at no point were any particles in the wave assumed to be going the speed of sound; that's why when you look from the vehicles reference you see a standing wave but at every point on it particles are still flowing towards the vehicle. The picture says it is in a sound-speed reference frame, but it probably confused you if you didn't read that.
At no point is the air doing anything but apply drag to the vehicle's movement; there is just a sweet spot to minimize drag, but it isn't minimized to zero.
Read through this thread a bit and you'll see me talking about the exact same difference of propagation of a disturbance vs displacement/velocity of individual particles...
It is probably my fault cause I sort of wrote the post as I worked out the concept and that ended up muddying a lot of the writing. And I'm not a physicist so I'm sure I didn't quite state everything in a very traditional way...
Just some info: Transonic/supersonic and near-speed-of-sound aerodynamics differ from traditional low velocity aerodynamics (I think the threshold is approximately 0.25Vs, so up to 1/4 of the speed of sound, I am a bit rusty on that). After that point you can't ignore compressibility phenomena, meaning that the density is no longer a constant, but also becomes a variable. You may be able to reduce drag by going very high in the atmosphere where the air is very thin (10^-6). Speed of sound also is an equation of the density and the temperature.
This is an intriguing proposal, but one that I think it ultimately flawed. Once a wave is strong enough for there be to appreciable density differences (NOT the usual case for sound waves), the usual wave equation for sound does not apply [1]. In the case of such "Very Strong Sound Waves", you have a non-linear wave equation and thus the shape of your wave is no longer fixed as it moves. Eventually, you end up with shock wave, where the front of your wave is a discontinuity.
Why is this problematic? Well, once you have a shock wave (e.g., a wave crashing on the beach), the physics gets a lot more complicated. You are basically riding an explosion in a tube.
At this point, it no longer safe to me to neglect factors like dissipation. Your shock wave is going to heat up the air and eventually fizzle out. If you want to keep it going, you'll need to be continually supplying tremendous amounts of energy at exactly the right time along your tube. You'll also have to be continually cooling or cycling the air to relieve the waste energy.
To me, it seems a lot simpler and more reliable (not to mention safer) to simply evacuate your tube, which, I believe, is the original hyperloop idea.
That's a great link.. should help see how far this could be practically taken.
When the wave is very strong the heat generated by compression isn't dissipated adiabatically the wave starts losing energy to waste heat; if you increase the wavelength you again move back to the adiabatic regime. How far can you take it? I don't know, I'd like to see some numbers and that's probably what I'd work on next if I keep looking into this.. probably won't until after Elon's announcement.
For extreme cases of high-amplitude waves where the particle velocity itself is getting close to the speed of sound, I definitely don't know what all happens, but somewhere in the write-up or comments here I at least had going that far as a bound on how far you could push things before you didn't really even have sound waves anymore.
"To me, it seems a lot simpler and more reliable (not to mention safer) to simply evacuate your tube, which, I believe, is the original hyperloop idea."
Musk has said on the record that it's not an evacuated tube.
Presumably the pressure wave is maintained by a continuous array of big-ass subwoofers along the whole length of the tube - If this is the case, then keeping the noise pollution down will be a bit of a challenge - unless some sort of active-noise cancellation technology is used for the outside.
Hmmm... This should not be too tricky, since you are generating the original signal yourself, but if one of the exterior noise-cancellation speakers breaks down - it's gonna be LOUD.
What I remember from physics class makes me think this isn't viable.
If you have sound moving through the tube, you have energy pushing the sound. Either you have to keep the whole tube 'humming' or you have to send people off in a blast wave. With the humming idea, you might be able to create vacuums that travel around the tube at the speed of sound (sound works by changing the density of air, oscillating from high pressure to low pressure), and then you can move vehicles around the tube at the speed of sound with very little drag.
So then you need some way to keep the vehicles floating, and you need to get them to the speed of sound in the first place (rail gun?). I'm going to pretend that we have a cheap way to do both of those things.
So, how expensive would it be to keep 100s of miles of hyperloop humming with a sound powerful enough to create vacuums large enough to fit transportation units in? Even if you are only using cars large enough to hold 1 person and a suitcase, you are going to need a lot of energy powering the sound waves throughout the tube.
You might be able to do some acoustics-like engineering to keep the sound loud at little energy cost, but I don't think that solar power above the tunnel is going to be enough. Using this model, Musk would need a handful of technological advances up his sleeve.
So I think the big 'secret' that makes a hyperloop viable is not this one. Then again, with the Tesla and his space adventures, he has had to deal with at least a handful of difficult obstacles. So maybe he is expecting to develop multiple technologies to make this viable.
The point of this approach was not to keep the whole tube humming (that would have almost as much friction loss as just circulating all the air in the whole loop), but rather just send waves in small bundles.
If you read my post it has nothing to do with vacuums and instead somewhat counter-intuitively keeps the vehicle within the densest part of the sound wave the entire time.
Seriously? Compared to that design evacuating the tunnel would make a lot of sense, as would going a lot slower than the speed of sound.
Now when Elon says it's not an evacuated tunnel, and also (indirectly) that you'll be traveling more or less exactly at the speed of sound, I'm leaning quite heavily towards the OP.
Not travelling through pressurized air.... travelling with the pressurized air. The idea behind the article I linked is that the entire system moves as a cohesive mass -- air, vehicles, and all.
Someone should build a prototype of such a tube and see if it's efficient. The mystery around Hyperloop generates a lot of ideas that should be tested. Railroad infrastructures are ageing, maybe some tuberoads can replace them.
I remember doing the math in my undergraduate physics studies. Air molecules actually do not move very far when a vibration (ie. sounds) goes through them. Amazingly, high frequency sounds move air back and forth only a few angstroms.
I can't find a link describing the calculation. This link talks about how the change in pressure is equivalent to "140 molecules for every million molecules"
http://www.silcom.com/~aludwig/musicand.htm
So there is no way you are going to create a bubble of vacuum!
Not trying to create a bubble of vacuum (though that was my old idea =).. then I realized what you lost gained by low density you paid for in high velocity).
Also, the idea here isn't involving high frequency sound.
I think the best you could do would be to stay near the trailing end of the pressure wave. This would be where the air was moving (slightly) in the same direction as your travel. You would also travel through the lowest density.
But I suspect you'd always be better off by simply evacuating the tube as much as possible.
Or possibly there is a medium other than air being considered, one in which the speed of sound was much lower at a given density. Perhaps interesting things could happen if the working fluid was a refrigerant and the sound wave was intense enough to induce a phase change cycle.
I'm confused by this... If the air molecules are staying roughly still, but the density of the air surrounding the vehicle rises by a factor of n, isn't the vehicle colliding with n times as many particles as it would have otherwise? How is this more efficient?
Is the velocity in the drag equation relative to the vehicle, or to a stationary frame of reference?
Edit: Or is the point that the velocity of the air particles within the density peak is at its maximal forward-traveling rate before they start to loop back around and form their ellipse?
I'm starting to think Elon has absolutely nothing planned, and just wanted to see what everyone thought he was doing, to help bring about all these awesome ideas for high speed travel :)
I think the problem with that idea is you have to keep the superconductor very cold, which might be too expensive for large objects that need to levitate for 30 minutes.
Sorry, let me clarify your statement: You spent 4 hours in the airport (or getting there, parking, getting sodomized by security) and 1 hour flying. Then another 30-60 minutes disembarking. So you spent around 6 hours in transit from SF to LA.
6 hours compared to 30 minutes (or more likely, 1.5 hours including the necessary boarding / unboarding) is a VAST difference.
It's amazing how easy it is to get in and out of different countries. Even getting on the ship is pretty easy.
I don't think there'll be much security theatre until a train gets blown up - most of the theatre so far seems to be reactive. "An idiot has explosives in his shoes. He is so incompetent that he tries to light it with a match" and now everyone has to take their shoes off.
Even if it did, the amount of "lobby time" would still be drastically lessened just based on frequency of departures and decoupling of passengers and elimination (presumably) of the checked baggage situation.
TSA security checkpoints suck, but IME they "only" represent about 15 or so minutes of the extra time required for airport lobby time (on average; sometimes more sometimes less. Which is at least 14 minutes too many, but hardly the whole 1-4 hour overhead often cited).
Most of the overhead of plane travel in terms of airport and tarmac waiting time is due to deadlocking problems that occur in coordinating all the passengers into a single vehicle that is as full as possible (to maximize the airline's profit per trip), so you get a very uneven/lumpy demand curve based on when flights are scheduled, all sorts of complexity due to the system of having to check bags into a separate physical compartment, etc. A continually operating system where you could just show up whenever, your bags stay with you for the ride, etc could easily smooth that out. Solve the deadlocking issue (and most of the hyperloop guesses I've seen do) and even if the security checkpoint stuff stays mostly the same you'll still have a far more efficient embark/disembark system.
True. In Europe we don't have TSA and yet one still would be wise to arrive at least an hour before departure (if one has checked baggage; half an hour otherwise) to an airport which is usually located 30+ minutes from the center of the city.
Times always add up like this - 0.5h to get to the airport, 1.5h on the airport, X h of flight and then up to 0.5h to leave the airport and another 0.5h to get to the city.
That's a fair point - I think most of us are just currently hoping that it won't.
I'd like to think that if Elon were running it (doesn't look like he wants to though), it wouldn't be a problem. He's a brilliant engineer who designs systems to overcome difficult problems. The 'security theatre' is just a consequence of an extremely poorly-designed system. I'm pretty sure someone like Elon could exploit modern sensing equipment and AI/ML techniques to build a system that is demonstrably better than, say, the TSA, and doesn't require anyone's personal space to be invaded. Who knows - maybe we'll get lucky and 'secure, 90 second check-in' be an integral feature of his design?!
This sort of rational sensibility isn't going to stop the TSA from power-grabbing and mission-creeping their way into any new transportation system. They'll get their tendrils in the pie, sure as the sunrise. So will a million other government bureaucracies.
Isn't the point that these things do not have much kinetic energy at all? The whole scheme wouldn't make sense if you still had to invest the same amount of power as for a conventional train.
Kinetic energy = 1/2 m * v^2. Hyperloop trains wouldn't have "much" less energy, because the scaling factor on velocity is so high that your savings on train weight don't mean much.
You'd be surprised. Just a week and a half ago ago a large section of Lac-Mégantic, a town east of Montreal, Quebec, was levelled by an unattended train that started rolling in the middle of the night. It was carrying a large load of oil, which ignited when the train derailed in the middle of the town.
Let's review the situation. We have a quite high speed transportation system in modern aircraft. We choose not to disrupt cities by building them downtown. (And "we" choose all those security/time trade-offs.)
You suggest that we will tear up the hearts of LA and SF to build direct train-tubes, and then we'll let people breeze on board?
You can put a train station mostly underground, with only a relatively small area aboveground. An airport is going to be 4 square miles, completely above ground, an entirely different story.
Currently with the only "fast" train in the US, you don't need to get on early, or go through special security. Why would this be different?
Are those tubes bulkier than current train/metropolitans ? Even cities like Rome dig underground to build urban transport, even if in those cities hearts you can find more than just soil.
I thought the reason we don't build airports in the middle of our cities is that jet engines are quite noisy and could cause lot of property damage (not to mention discomfort) if operated next to other buildings.
Sound: a vacuum and a high pressure alternating ... Using wind would be far cheaper and better I think :-)
I mean really really low sound frequencies are the same anyway. (As far as my physics go)
In case this is unclear to anyone; all transonic, supersonic, or hypersonic flight/movement causes a 'continuous' sonic boom. A Bell X-1 at Mach 1.06 causes a continuous sonic boom along it's path, as does a Mach 2 Concorde and a Mach 2.6 Browning 50 cal machine gun bullet. "Sonic booms" are not discrete events that occur when you cross the 'sound barrier' or continuous when you stay at it. They are continuous at it and past it, not stopping until your velocity drops down below it again.
GIF that does a good job of explaining this: http://upload.wikimedia.org/wikipedia/commons/e/e4/Doppleref... That leading edge where all the circles are kind of meeting up? That is where the sonic boom is. It continuously sweeps across the landscape behind the source, as long as the source is moving faster than the speed of sound.
Going faster tightens that pressure wave cone, but there are a lot of other factors too. Vehicle geometry seems to be a pretty dominating factor for example, longer aircraft have less severe sonic booms. Depending on the shape of your aircraft you may or may not get several shockwaves originating from different points that after a distance combine to form a larger shockwave. Altitude is a biggie too, the higher you are the less intense it will be.
I'm all the opposite. It's amazing how many different solutions where proposed since the Elon Musk teased the Hyperloop. If nothing else, the Hyperloop sparked imagination everywhere.
Even if most proposed solutions are impractical, the very fact that they are out there now, for others to see, think about and tinker with, is a big win.
If this works, I wonder about the logic of making it a SF-LA thing? At least, there should be another use case.
Why not go from Silicon Valley to a mountain area where you've bought a large area of land, ready to build on?
You could get investments from all over the tech industry, since it would lower living costs (and increase the maximum number) of the people that Silicon Valley can have (less infrastructure and living area "load").
Use the sales slogan "let's supersize the Silicon Valley!" for this new commuting solution.
Here's a crazy thought: Let's get outside the West Coast bubble here and think about this in a vastly more practical manner when it comes to population density and distance between urban cores.
Every time I hear this project spoken of, I have to hear people who live in the Bay Area talking about "SF to LA in half an hour"
I think what would be much more sensible would be "NY to Boston in 15 minutes" and then extending it to Philadelphia and DC. Where would the line go after it hit SF? Portland and Seattle? Denver? The populations of these places don't support the cost of the infrastructure. The east coast makes much more sense for this project.
You are assuming that there are not millions upon millions of people who can't justify flying from Boston to New York due to the fact that the car trip (when you factor in arrival at airport 90 mins ahead of time) isn't drastically slower than flying.
I say this as a seasoned east coast corporate whore. Many, many business travellers are forced to just drive from New York to Boston due to the fact that the trip is 3 and a half hours long in a car. NYC to DC is about 3 hours 44 minutes by car. These are distances which are just short enough to make a company tell an employee to drive instead of fly, but long enough that nobody in their right mind would want to commute this way on a semi-regular basis.
Not counting Baltimore, the East Coast corridor has over 35 million people in the big city's metro area.
If the price of this service is expected to be similar to air travel, then I get it (SF-LA), if this is simply about selling speed for a premium price...... but I think this is really about doing it faster AND cheaper. If its efficient enough, this could lead to a decoupling of workplace from home location, the way telecommuting was supposed to.
This makes much more sense. Perhaps I am biased from my East Coast viewpoint, but these things have to be built for everyone, not just tech enthusiasts. The East Coast has many more destinations that could benefit from this. For me right now, it's an hour to Boston and five to NYC. Philadelphia is maybe seven, DC a little more. If the hyperloop performs as Musk says it will, it would be 40 minutes from Boston to DC - commuting distance. That would completely revolutionize this side of the country. I could work in NYC but enjoy all the comfort of New England.
>>I could work in NYC but enjoy all the comfort of New England.
The station cost will probably be high; it will be hard to have "side tracks". (No fan-out, you could say.)
So if there is a station in e.g. NY/LA, the housing costs for the other end station(s) ought to rapidly close with the big-city end station. It is just a way of opening a larger area for commuting.
So, there won't be that much comforts of New England.
My point was that with a HL the areas with high people pressure could continue to grow (I selected Silicon Valley because HN is a California-centric place, for good and bad. I'm in Europe.)
True. It will probably be relatively expensive, at least at first. Still, if it's moderately priced (<$100) I would be much more willing to take long-distance trips down the coast. As it is, I rarely go to NYC or Philadelphia because of the time and/or cost. Maybe not commute, but certainly visit with some regularity.
2 reasons nobody has (surprisingly) mentioned yet:
- Trains: the Acela is established and successful, already taking about half of the passengers on the Eastern corridor.
- Right of way: (to borrow one of your sentences) the population density of thses places [East Coast] drives up the cost of the infrastructure.
Another factor might be that the design is better optimized for 400 miles than for 200. The capsule acceleration phase is necessarily long and energy-intensive, so you want to optimize that over longer distances. It's the same reason that high-speed trains don't have stops every 20 miles.
Well, he lives on the West Coast, and likely prefers to solve problems he faces more often first. If it works, there is nothing stopping one being built on the East Coast, but as long as the West Coast is thinking of, designing, and building the thing, I see no problem with it starting out here.
Putting on my well-worn cynic hat, I wonder how much SV's anti-remote attitude is influenced by people whose inflated property values depend on SV's anti-remote attitude.
Building this thing will be expensive. SF-LA is probably best place in US if you optimize for traffic volumes and capital needs.
I seriously doubt that this is going to happen between SF-LA first. If this is feasible idea, he will be able to sell it to Japan, China and EU countries first.
The "density front" travels at exactly the speed of sound, but it consists of nearly static particles (not static from the frame of reference, from the frame of reference they are moving backward at nearly the speed of sound), these static particles are the relevant V.
The sparse particles just in front of the dense ones are accelerating to get more sparse. From the perspective of the reference frame, they are therefore moving 'backward' at slightly less than the speed of sound, making there relative velocity closer to that of the reference frame. So lower density and lower velocity. and that doesn't even account for additional compression which I don't even know enough to do armchair reasoning on.
So, I'm the farthest thing from an expert, but this is why it doesn't seem to make sense to me.