>The Hyperloop pods will travel[...] about 30 seconds apart in the tube. They will have a maximum deceleration of 0.5 gs [...] it will take a pod 68.4 seconds to come to a full stop.<p>>That's a pretty significant issue because safe vehicle operation means never getting closer to the vehicle ahead than the distance it will take you to stop. [...] That means that the minimum separation between pods is probably closer to 80 seconds or more.<p>Two flawed assumptions in here:<p>1. 0.5 g is the maximum deceleration under normal conditions (see p. 58 in Musk's PDF). Emergency braking would obviously be capable of more. The linear accelerators themselves are spec'd to be capable of 1g, and there's an onboard emergency braking system on top of that.<p>2. A vehicle that crashes doesn't stop immediately, but continues on its direction of motion due to inertia. That's why the two second rule is plenty safe on highways [1], even though expected vehicle stopping times are six seconds or more [2].<p>Furthermore, the article is basically an attack on maximum capacity, but that's not a real issue. The system is economically viable if it can get passengers from point A to point B at comfort and cost levels (including recouping investment) that compare favorably with other means of transportation; Musk cites $20 per ticket, which the article doesn't dispute Maximum capacity can always be expanded if the economics work otherwise.<p>[1] <a href="http://en.wikipedia.org/wiki/Two-second_rule" rel="nofollow">http://en.wikipedia.org/wiki/Two-second_rule</a><p>[2] <a href="http://www.csgnetwork.com/stopdistinfo.html" rel="nofollow">http://www.csgnetwork.com/stopdistinfo.html</a>
Aren't we arguing about the wrong things here? The hyperloop is actually something worth having as it will get you from SF to LA in 30 mins. Even if it costs more and takes less people than HSR, it's still far better than HSR for actually getting you between the two cities in the kind of time people would like. If you could set up these 30 min hops between cities all over the world, you will <i>improve humanity as a whole</i>. That's something worth attempting.<p>If capacity becomes an issue, you could just add more tracks. If the cost is wrong (and it no doubt is), why is nobody coming up with the real cost so we can compare this properly? Hand waving about 'too low!' is only useful for arguing, not for finding a solution. Are there other ways that the cost could be brought down?
So his point about spacing may be true for loading and unloading, but it is not for emergency stops. You can exceed .5g's in am emergency. With appropriate restraints, 4 or 5g's would be possible.<p>The larger problem is: if you can build a hyper loop track at 10% of the cost, you can build an ultra light conventional "train" on the same pylons and with lighter weight,cheaper, track. It would run at maybe 200 or 250pm and hence with reduced capacity. At best Musk's cost claims are a capacity/cost trade off. At worst, they are suspect. I think they are suspect, especially given the extreme tolerances of the tube
Comparing the theoretical capacity of the Hyperloop vs the High Speed Rail is only one fact to consider. Musk correctly points out the High Speed Rail is in theory way more dangerous. And, possibly more significantly, it is just too slow. To expect travel consumers to opt to max-out the so-called High Speed Rail capacity is wishful thinking. The real "high speed" capability of the Hyperloop make it more likely consumers would opt to max out its capacity, at which point more capacity can be added (by adding a parallel loop), and it is still cheaper than the High Speed Rail.
In the engineering field, I've found there's an issue with a subset of engineers where they get some kind of enjoyment out of saying why something <i>can't</i> be done without providing any suggestions or improvements to make it possible. They just feel the need to be negative and list reasons why something won't work. It's unfortunately common, it's unproductive, and it really gets kind of annoying after a while.
There may be some valid points in there, but I don't consider it very productive to get this kind of info from this source. I'm not sure what their agenda is, but it clearly doesn't have anything to do with economics or transportation. From the authors recent articles, I have my doubts he would approve of anything that isn't initiated by government. Consider this article <a href="http://greatergreaterwashington.org/post/19330/supreme-court-limits-communities-control-over-their-growth/" rel="nofollow">http://greatergreaterwashington.org/post/19330/supreme-court...</a><p>Since I lack the expertise to know myself whether the numbers are plausible or will work out, I need to rely on the expertise of others. And one of my ways of evaluating the expertise of others is if they appear to be guided by facts or by an agenda.
Part of the problem is that HSR is fast, technically feasible, heavily used, and economically viable in France, Germany, China, Japan, and other places.<p>So, the most useful analysis would be:<p>1. What factors are preventing HSR from being fast, technically feasible, heavily used, and economically viable in the United States? (More concretely, why does California's HSR suck so much when it's been demonstrated that HSR doesn't necessarily have to suck?) Demographics (e.g. population density and layout)? Political and legal constraints? Terrain? Culture?<p>2. How does the Hyperloop mitigate or sidestep these problems, due to its superior specifications or design differences from HSR?<p>3. For additional insight, what would California's HSR have had to do differently to mitigate or bypass these issues, and would it even have been possible?
People have largely missed the salient points of Elon's proposal:<p>1) If America cannot understand the potential and purpose of innovative technology, it is doomed to slide into socio-economic, scientific, and technological poverty. The point is that building a slow and expensive HSR is stupid, and people have approved it solely because they are, similarly, too stupid to envision what is possible. The primary point of building the Hyperloop is not to move people physically, but to move them intellectually.<p>2) the Hyperloop, as designed by Elon, has zero emissions. We should do it for that reason alone, otherwise we are genuinely too stupid to exist, which fact says more about us than any debate. If we do not begin building zero-emissions systems, the debate will not matter because we will be gone.<p>3) Capacity problems are not an issue. Elon has intelligently anticipated a diminishing requirement to physically move people because of the improvement of telepresence technology. If you still need to travel as much as you did ten years ago, you are an idiot. This trend will only increase. Elon is too savvy to mention this explicitly, but he no doubt understands that the need to move people physically is declining. The HSR will be mostly empty if it opens in 2024 with the capacity required in 2014.<p>4) Our entrenched institutions have failed us, not because of anything specific that they have done wrong, but simply because they are entrenched. We should build the Hyperloop for no other reason than a little revolution being a good thing, now and again.
It seems some people don't quite understand what the big deal is about not terminating outside the major population centers.<p>For people from the east coast, imagine a train system that claimed to connect New York and DC, but actually terminated in Manville, NJ and Bowie, MD.
The most important issue in terms of long-term cost-effectiveness is how much it will actually be used, and how much of the time it is actually full. High Speed Rails or any trains for that matter, are plagued by the inefficiency of having to run at a set schedule regardless of how many tickets are sold, and they ultimately don't justify their own existence in most of America. The hyperloop, aside from attracting new people who otherwise wouldn't have considered rail travel, also has the benefit of having smaller capacity and being able to adapt to demand more quickly. With no stops between SF and LA, if there are no passengers at a certain time, you just don't send the vehicle -its that simple.
The capacity constraint accusation on the grounds of spacing and max G is pretty bogus. Firstly, there's nothing wrong with running at far more than 0.5g in an emergency. You think a plane stays below 0.5g when it crash lands? You just have to make sure people aren't badly injured, not pamper them - and make sure such emergencies are very rare.<p>Where the author really gets it wrong though is in saying "Maybe he can resolve that by using larger pods. But of course, a larger pod will weigh more. And that will probably mean using stronger steel for the tubes, which means that the cost will go up".
That would be true, but if you're happy to resolve the issue with larger pods then you should be equally happy to resolve it with groups of smaller pods travelling at smaller separations. A 737-800 seats around 150 people. Hyperloop passenger capsules seat 30. So no one should have any conceptual issue with running 5 hyperloop capsules in convoy with separation of a couple of seconds. This 'couple of seconds' still means almost 1km, so they're certainly not sharing the same segments of tube, so you don't need to scale the tube design at all. It's still dirt cheap, and you have plenty of capacity, and it's still MUCH safer than a plane because if one capsule has a fault the others following can still likely stop in time (given they're all decelerating at roughly the same speed).
Isn't it incorrect to simply compare the capacity of the Hyperloop vs. the High Speed Rail. Shouldn't the transport time also be taken into account?<p>I mean, simplifying of course, if the Hyperloop can carry ~3,000 from A to B in 30 minutes, and the High Speed Rail can carry ~12,000 from A to B in 2 hours, which is better? In this scenario wouldn't they be equal?
Even if he is right and the math does not add up, I do not think that Musk is likely go to all this trouble to try and boost Tesla sales in California in 2026, which is the earliest that HSR is planned to get anywhere close to connecting LA and San Francisco, and even then it actually only gets as far as San Jose, the San Francisco bit is scheduled to open in 2029.<p>I can't see a plan involving the idea that in 2029 Tesla would be so dependent on Californian sales rather than global, that it would seek to stop a local rail network from progressing. Especially a plan so convoluted as to involve actually taking time out from running a rocketship business, car company and solar power company, in order to design a rail network that according to the theory, you do not want built.