3 ms·

This kind of Hyperloop criticism is commonplace, but strikes me as intellectually lazy. Did you read Robotbeat's link? Particularly with respect to to the MNLC

by nkoren 9y ago

This kind of Hyperloop criticism is commonplace, but strikes me as intellectually lazy. Did you read Robotbeat's link? Particularly with respect to to the MNLC Bellows Expansion Joint. > 1) will hold a vacuum Plain wrong. > 2) are available in the 3+ meter diameter that the hyperloop requires This is a simple manufacturing problem, although calling a "problem" seems like an overstatement. Obviously not everything to build a Hyperloop is wholly off the shelf. If there is some reason why this can't be built in larger diameters, then that's certainly not obvious. > 3) provides the smooth inside surface that the hyperloop requires The Hyperloop runs on an air cushion. It's a hovercraft. Millimeter-scale bellows ought not to be a problem. > 4) are economically viable And here, you could be entirely correct, and is why I'm not yet a Hyperloop true believer. I'm not wholly convinced that this kind of machinery can be economical over its whole life-cycle in its intended service environment. But proving that this is the case requires more than glib, hand-wavy assumptions. You need to run the numbers. I have yet to see any Hyperloop critic do that in a remotely convincing fashion, whereas there are many Hyperloop engineers who most assuredly are running numbers. Maybe those calculations are wrong, but the only way to refute them is with better calculations. Anything else is just dogma.

mrguyorama 9y ago
HyperLoop does NOT run on an air cushion (remember, the entire tube is supposed to be nearly evacuated!), but instead floats on a maglev track. He's also missing another requirement: 5) The entire track, including any possible expansion components, valves, inspection hatches, etc etc etc have to be at least mildly tolerant to intentional or accidental damage. Running into a sudden wall of air at 700mph is a good way to destroy any passenger craft in the system.
- jccooper 9y ago
  That depends on the design. In Elon's original paper hyperloop the vehicles have an air bearing.
TeMPOraL 9y ago
RE 4, there are also two "kinds" of economical viability: the fundamental one, derived straight from physical limits, and the usual "market couldn't be bothered with it" one. Knowing Musk's companies, he cares only about the former, and is willing to push through the latter. Thanks to that, fully electric cars with reasonable range are now not only a possibility, but a desirable product every other car company wants to build too. The number crunching should tell in which category of viability Hyperloop is.
- nkoren 9y ago
  Just so. In the 1990s I was part of a group called the Space Access Society, which was a bunch of cranky but idealistic rocket scientists (and enthusiastic amateurs; John Carmack was a constant presence with his Armadillo Aerospace) trying to foster cheap access to space by any means possible. These efforts were regarded with huge levels of skepticism / disinterest / dismissal from NASA and the mainstream aerospace industry, which consistently confused the second kind of viability with the first. When these people couldn't raise and/or manage the funds to actually implement their ideas, this was regarded by many as proof of the physical impossibility of cheap access to space. Most of the industry regarded them as crackpots. Then Elon Musk came along and proved the crackpots right and the industry wrong. He could do this because physics was on the side of the crackpots and always had been, even if the market was not. That's a necessary but not sufficient condition; what he also needed -- and just barely had -- was the financial resources and organisational capacity to go up against the market and win. There are aerospace forums[1] where one can still find smatterings of the old guard insisting that Elon Musk is just a smoke-and-mirrors phenomena; that spaceflight will always be intrinsically expensive because physics (in a hand-wavey, strictly no-calculations kind of way) says it must be so; that the only reason his rockets are cheap is because he's underpaying his workforce and working them to death; that it's impossible to re-use a rocket -- seriously, they're still saying this, even after it's been done three times already; that the Shuttle proved that reusability can never lower the cost of spaceflight, etc. etc. etc. Some of these people have PhDs in aerospace engineering; some of them have worked on the space shuttle. No matter: they're in the throes of a cargo cult, and they're wrong. Physics are right. Do the numbers. Engineering is done with numbers. Analysis without numbers is only an opinion.[2] 1: forum.nasaspaceflight.com/index.php 2: http://spacecraft.ssl.umd.edu/akins_laws.html http://spacecraft.ssl.umd.edu/akins_laws.html
glenstein 9y ago
Thank you for posting this. With all kinds of matter-of-fact comments confidently declaring the impossibility of feasible hyperloop implementations, a lot of those arguments turn out to hinge on random, idiosyncratic details that are not at all the dealbreakers they're made out to be.

by nkoren 9y ago

mrguyorama 9y ago

HyperLoop does NOT run on an air cushion (remember, the entire tube is supposed to be nearly evacuated!), but instead floats on a maglev track. He's also missing another requirement: 5) The entire track, including any possible expansion components, valves, inspection hatches, etc etc etc have to be at least mildly tolerant to intentional or accidental damage. Running into a sudden wall of air at 700mph is a good way to destroy any passenger craft in the system.

jccooper 9y ago
That depends on the design. In Elon's original paper hyperloop the vehicles have an air bearing.

TeMPOraL 9y ago

RE 4, there are also two "kinds" of economical viability: the fundamental one, derived straight from physical limits, and the usual "market couldn't be bothered with it" one. Knowing Musk's companies, he cares only about the former, and is willing to push through the latter. Thanks to that, fully electric cars with reasonable range are now not only a possibility, but a desirable product every other car company wants to build too. The number crunching should tell in which category of viability Hyperloop is.

nkoren 9y ago
Just so. In the 1990s I was part of a group called the Space Access Society, which was a bunch of cranky but idealistic rocket scientists (and enthusiastic amateurs; John Carmack was a constant presence with his Armadillo Aerospace) trying to foster cheap access to space by any means possible. These efforts were regarded with huge levels of skepticism / disinterest / dismissal from NASA and the mainstream aerospace industry, which consistently confused the second kind of viability with the first. When these people couldn't raise and/or manage the funds to actually implement their ideas, this was regarded by many as proof of the physical impossibility of cheap access to space. Most of the industry regarded them as crackpots. Then Elon Musk came along and proved the crackpots right and the industry wrong. He could do this because physics was on the side of the crackpots and always had been, even if the market was not. That's a necessary but not sufficient condition; what he also needed -- and just barely had -- was the financial resources and organisational capacity to go up against the market and win. There are aerospace forums[1] where one can still find smatterings of the old guard insisting that Elon Musk is just a smoke-and-mirrors phenomena; that spaceflight will always be intrinsically expensive because physics (in a hand-wavey, strictly no-calculations kind of way) says it must be so; that the only reason his rockets are cheap is because he's underpaying his workforce and working them to death; that it's impossible to re-use a rocket -- seriously, they're still saying this, even after it's been done three times already; that the Shuttle proved that reusability can never lower the cost of spaceflight, etc. etc. etc. Some of these people have PhDs in aerospace engineering; some of them have worked on the space shuttle. No matter: they're in the throes of a cargo cult, and they're wrong. Physics are right. Do the numbers. Engineering is done with numbers. Analysis without numbers is only an opinion.[2] 1: forum.nasaspaceflight.com/index.php 2: http://spacecraft.ssl.umd.edu/akins_laws.html http://spacecraft.ssl.umd.edu/akins_laws.html

glenstein 9y ago

Thank you for posting this. With all kinds of matter-of-fact comments confidently declaring the impossibility of feasible hyperloop implementations, a lot of those arguments turn out to hinge on random, idiosyncratic details that are not at all the dealbreakers they're made out to be.