This isn't nitpicking. Dealing with the acceleration around curves is going to be a problem for any transit system and at higher speeds it becomes a bigger problem. Unlike bathrooms, this is going to be intrinsic to any system that carries human beings. As the author points out that the hyperloop proposal has significantly higher acceleration than any other high-speed system that he knows about.
So, how did the hyperloop designers decide that 4.9 m/s^2 would be safe? Did they find some study which tested this level of acceleration on average people? Did they conduct their own study which overturned conventional wisdom? Did they look at the research which led to the 4.37 m/s^2 figure and determine that it was fatally flawed? This is a critical issue and if the designers don't explain themselves, then it's fair to assume they made it up.
The hyperloop proposal contains innovative elements (air suspension in evacuated tubes) and elements which are essentially common with many other transit systems (viaducts, human passengers). The designers deserve credit for the former, but they can't sweep the details of the latter under the rug. The point of references is not stylistic and not to name-check previous work. The point is that when you're doing something, which has had lots of previous research, you either use that research to justify your claims or you explain why yours will be different.
> The really interesting, constructive questions: does this low-pressure air cushion thing really work? what are some factors that we need to explore to determine its true efficiency?
Those are interesting questions and if Musk had proposed just the air cushion technology, then that's all we would be talking about. People would build test pieces to validate the technology and then go looking for applications. Instead, Musk choose to also include a specific proposal for a replacement for the LA-SF high-speed rail line and to estimate the costs at a tenth as much. That's what got the most media attention and so that's the aspect the OP chose to criticize.
BTW, you seem to be implying that the OP is a civil engineer or a transportation engineer with an axe to grind, but he's just an amateur and if you look at his other posts you'll see that he has a lot of concerns for reducing the costs of infrastructure projects.
- Do we have studies that estimate the effect of lateral acceleration on motion sickness? What do they indicate (e.g. 0.1% of passengers get it at 4 m/s^2, 2% at 5 m/s^2 etc.)?
- To what extent is motion sickness in HSR comparable to the proposed system? Are the differences (no outside visibility, different vibrations model, possibly different seating) significant and if so how?
- To what extent do potential passengers care about motion sickness? Has anyone compared cost and convenience trade-offs for systems with different expectations of motion sickness e.g. ferry vs. train? How comfortable are passengers with self-medication in such contingencies?
Etc. And motion sickness is only one of hundreds of possible serious weaknesses in this project. But this is inherent in anything that hasn't been tried before; anyone can think of hundreds of ways in which it can go wrong. Does this mean we should never work on anything that isn't fully proven?
You're comparing apples to oranges here. If I understand the OP correctly, the 4.37 m/s^2 (which is a claimed maximum, not actually in practice, but let's ignore that) is in the plane of the ground. Canting will convert that acceleration into a mixture of horizontal and vertical acceleration, as experienced by the passenger. The hyperloop track has 11.1 m/s^2 of acceleration in the plane of the ground based on their path assumptions (= (480km/h = 133 m/s)^2 / 1600 m), which the OP claims can get converted to 5 m/s^2 of vertical acceleration. This 7 times greater than "track specifications" of 0.5-0.67 m/s^2 and 5 times greater than the 0.93 m/s^2 of vertical acceleration coming from the Transrapid's 4.37 m/s^2 in the plane of the ground.
To step back for a minute, the issues with curve radius for high-speed transit have existed since the beginnings of high-speed rail 50 years ago and maybe longer. It's one of the major issues preventing Amtrak from going faster in the Northeast corridor, for example. If there was some easy way (blocking windows, lowering vibrations, changing expectations, self-medication) to deal with it, our first assumption should be that someone's already tried it. If Elon Musk had some new, breakthrough ideas in this regard, then our assumption should be that he would somehow mention it, rather than expecting the Internet to figure it out from the numbers he uses.
In the absence of evidence that any of the thousands of people who have designed high-speed transit allow for such sharp turns, or that the hyperloop designers have any way to mitigate the effects of high acceleration, I think the most likely possibility is that they (some of whom work for SpaceX, remember) used acceleration limits coming from the space program. Since they seem never bothered to compare to look at actual high-speed rail systems, they never noticed how different their assumptions where.
The Hyperloop document was obviously putting a flag up a flagpole to see who salutes. It had a few man-hours of estimations put into it. It looks like that, obviously.
So the numbers need improvement, sure. Its nit-picking when you get all emotional about it and trash the author.
But many of most important (and show-stopping) principles involved are the same, and those are what tend to cause delays and increase costs - things like running into unexpected geology, dealing with NIMBY's, the eminent domain process and so on.
He seems to think that, in between, his colleagues have been perfecting the fine forms of the art and polishing its many facets.
They (we) are. Want to see for yourself? Go to the Transportation Research Board annual meeting in Washington D.C.: http://www.trb.org/AnnualMeeting2014/AnnualMeeting2014.aspx
Except feats that were once fairly common, such as building the Hoover Dam under budget and two years ahead of schedule [1], are in the realm of the mythical these days.
You can say the same about the original elevated Boston Artery, the 19th century railroads, etc. The biggest difference between the mega-projects of old and today involve 1) the environmental process and 2) commitments to worker safety. It's fairly easy to build a project quickly when you don't care about splitting neighborhoods, killing/maiming workers and contaminating soil. The environmental process in particular has been a double-edged sword - it's done well in protecting the environment and communities, but it also provides means for anyone who doesn't like any facet of a project to significanty delay (or kill) it.
I don't see why environmental and safety considerations are such big unknowns, I think we have a pretty good handle on both by now. Are they factoring to build it with pollution and no safety when they estimate the cost and schedule these days?
In fact, if you read about the history of Hoover Dam there were a number of these things that they weren't legally mandated to do back then, but did them anyway. For instance, workers were offered employer-based health insurance (an arrangement that later evolved into what we know today as Kaiser Permanente).
In terms of a specific project, not really. Look at everything that goes into an environmental study: watershed/water quality, affected wildlife/endangered species, noise & vibration, soil contamination, archaeological issues, visual impacts, rodent/pests, etc, etc. On top of that, you have to consider the effects of all of those areas during construction and ongoing operations for 20+ years. And that doesn't even account for NIMBY issues.
When you're getting into the details of a specific project, it can quickly become overwhelming, especially if you have people who may be philosophically opposed to the project hammering you with those issues time and time again.
Are they factoring to build it with pollution and no safety when they estimate the cost and schedule these days?
When you look at a project at a high level, you make general assumptions, but as you get more detailed and you know specifically what kind of equipment
Take for example, tunneling: At the start of a project, your best information tells you that the sand down to 70ft below grade is clay, so you make your cost and construction estimates using this assumption. You get into detailed design and send drill crews out to collect sample borings and you find out that in much of the area where you assumed sand, you actually have bedrock coming up to 10ft below grade. Now you're plans have to change - instead of doing cut-and-cover tunneling everywhere, you have to blast in some sections, which means having to get a blasting contractor, deal with protecting nearby structures, changing traffic patterns to allow for the blasting etc. In the old days, the project would have just blasted, and if someone's foundation got cracked in the process, too bad. Today that won't fly.
edit: just saw your edit
In fact, if you read about the history of Hoover Dam there were a number of these things that they weren't legally mandated to do back then, but did them anyway.
Compare the number of people killed at the Hoover Dam project compared with the number killed during the Big Dig.
That being said, I'm by no means persuaded. If the original technical estimates can't be completely precise, why do they always happen to always be inaccurate on the bad side these days? How come they rarely plan for bedrock and get a lot more clay instead?
Overall, I understand there are new challenges today that older projects didn't encounter. On the other hand, they also had serious challenges that we don't meet (very bad transportation network, frequent strikes, including the wildcat variety, a much less educated workforce etc.) Maybe it's even true that, despite all the new technologies and infrastructure to help us, the cost per unit needs to be higher these days and work needs to proceed more slowly. But that still doesn't explain why projects almost always still run over that higher cost and longer schedule.
I don't have time to find it right now, but I remember reading a study a few years ago that showed most projects to in fact come in on time and on budget. It's the few major projects that make the headlines that have schedule & budget problems, and (to no surprise) those tend to be the projects that have to deal with the most complexities. It's not different than large software projects.
On the other hand, they also had serious challenges that we don't meet
Sure, but they could work around those problems by (literally) throwing bodies at that project and dumping crap into rivers. And some of those things you indentifiy as problems ("very bad transportation network," "less educated workforce") aren't really problems - "less educated" means "cheap": the project just needed to train you to hold a rivet in place or swing a hammer, today's workforce needs to know how to manage complex diesel equipment. "very bad transportation network" means "more room to work": building the Hoover Dam in the boonies is in many respects much less difficult than building the 2nd Avenue subway under a crowded Manhattan or building the Big Dig under a busy Boston. In fact most of the high cost of CA HSR isn't from building the sections in the boonies (which is why they're starting construction there first), it's building the connections into the heavily populated metro areas like San Francisco and LA.
If you ever have the chance (and you're an American), go to a public meeting organized by a huge capital project. Listen to all of the comments (ranging from measured to angry, reasonable to crazy) and keep in mind that the project has to address all of those concerns. That will give you a sense of scale of the problem. In fact I spend this past weekend dealing with concerns that frankly defy the laws of thermodynamics, but the project has to address, which means I spend billing hours debunking it.
edit: enko makes a good point, you could go ulta-conservative with cost estimation, but then every highway widening project becomes a $100 billion undertaking and nothing would ever get done. Projects to set aside 5-15% for continengy and most of the time that's enough. Of course there are outliers, and those are what tend to get attention. You also have times were a project may also set a relatively low budget, but they get back bids from contractors and/or engineering firms that way exceed the budget, so the budget gets increased.
I don’t think we should do the high-speed
rail thing because it’s currently slated
to be roughly $70 billion but if one ratio
is the cost at approval time versus the
cost at completion time of most large
projects I think it’s probably going to be
close to $100 billion.
And, according to this:
http://californiawatch.org/dailyreport/bullet-train-bidder-h...
...the lowest (and winning) bidder for early work on the California HSR has a history of cost overruns, so things aren't starting out so hot.
Your last paragraph seems to say that we don't want accurate estimates because then we might not do the projects. That's the point of knowing the costs. We don't want to do projects that are too expensive.
Large projects, like Hyperloop or HSR, are probably the ones particularly likely to be "outliers" (if indeed projects with overruns are outliers) and big projects are the ones where that damage costs the most, so it's a double whammy.
Meanwhile, if we're now accepting that lowballing is a good idea, as your last paragraph says, then I don't understand why you seem to be defending the original article as Musk must just be lowballing and he expects overruns. It will take a lot of overruns to catch up with the ostensible California HSR budget.
I will say that, with SpaceX, Musk and the government have fixed-price contracts, so SpaceX eats cost overruns. They also have the lowest space cargo delivery cost for their class. This gives me some evidence that Musk could deliver more cheaply and on budget than the linked industry observer expects.
No, my last paragraph says we don't want ultra-conservative estimates because we would definitely not do the projects.
Meanwhile, if we're now accepting that lowballing is a good idea, as your last paragraph says
My last paragraph doesn't say that.
This gives me some evidence that Musk could deliver more cheaply and on budget than the linked industry observer expects.
Perhaps. But if I were a betting man, I think Must will be in for a rude awakening upon discovering the mess that is the public environmental process, as have many other entrepreneurs before him.
Well, an obvious factor is that there is a huge incentive to under-estimate for anyone with an interest in the project's green light. The cheaper a project looks on that initial paper, the more likely it will be approved, and if/when it goes over budget, what are they going to do? Cancel it with the tunnel half dug?
It's a political/societal problem of poor economic ideologies, lowest-bidder pricing and misaligned incentives, coupled with a low aversion to - or even understanding of - economic crime.
And it's by no means limited to these mega-projects. I know a certain software company who specialises in winning contracts by low-balling the price, expecting to argue it up later when all sorts of "unexpected" issues arise - those same issues the losing bids allowed for. Pretty much the same game.
https://twitter.com/TalulahRiley/status/320421724644573184 https://twitter.com/TalulahRiley/status/320422298618302464
Just to toss in an entertaining data point.
And I did not know the Hyperloop would not actually go into LA proper. That's a significant difference to me. That last leg into LA is where a lot of the traffic trauma happens, the part I would most want to avoid.
Ultimately both "sides" need to work with each other. The entrepreneur pushing the envelope, and the engineer making sure things are feasible.
An analog here would be if Musk had a proposal to take an existing, working mode of transit (at least working in prototype) and build it for less. But the current proposal is more like hard sci-fi: goes into enough depth to be back-of-the-envelope plausible, but no detailed engineering or working demonstration, and very hand-wavy cost estimates.
[1] http://en.wikipedia.org/wiki/Comparison_of_orbital_launch_sy...
Buildng projects on the scale of the Hoover Dam (whether under budget and ahead of schedule or not) were never "fairly common".
In all fairness, I would give much more slack to an engineer talking about his field. But, as the author himself points out, almost all civil engineering technology is from the 19th and early 20th century. He seems to think that, in between, his colleagues have been perfecting the fine forms of the art and polishing its many facets. Except feats that were once fairly common, such as building the Hoover Dam under budget and two years ahead of schedule [1], are in the realm of the mythical these days.
[1] http://en.wikipedia.org/wiki/Hoover_dam