291–300 of 517 posts
Despite the fact there are more billionaires than ever, it's funny how small the group of bold innovators are. It always seems to be the same few people.
I'd argue that Bill Gate's work has a better return of investment for society.
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sigh another "deadly wall of air" theory ala Thunderf00t? Hasn't this been debunked already? "A little bit of physics is a dangerous thing." * A bullet or piece of debris would likely leave a hole much smaller than the diameter of the tube. A breach 1/10th the diameter of the tube will admit 1/100ths as much the air. * Even if there was a whole-tube breach, the "wall of air" will rapidly slow down and smear out into…
> ala Thunderf00t Just watched one of his videos on this--interesting and thank you for the pointer. Agree with you on his overstating the deadliness of pressure pulses. 30 kg of TNT is a lot of energy, certainly enough to knock your infrastructure out of commission for a couple days. The "everyone dies if the tube is punctured" argument is hyperbolic, though. The materials science problem is the thermal expansion. A…
Right... you can probably solve that with a bucket of white paint. Worst case you cover it with an aluminum shield- aluminum does not absorb infrared radiation and will reflect 99.9% of ambient heat. Since the proposal included covering large sections of the tube in solar panels that isn't even a significant change.
The original Hyperloop paper quotes its design pressure as “about 1/6 the pressure of the atmosphere on Mars” [1]. Martian atmospheric pressure is “about 0.6% of Earth's mean sea level pressure” [2]. So 0.1% of Earth’s surface pressure, or a 1,000:1 pressure change. To put that in perspective, the Boeing 787’s GEnx-2B67, the most powerful GEnx engine variant, generates a 43:1 pressure ratio [3]. To get a sense of the…
Solve the mass-scale construction and maintenance efficiency problem and we can get all kinds of cool things like hyperloops, space elevators, and fancy megacities.
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sigh another "deadly wall of air" theory ala Thunderf00t? Hasn't this been debunked already? "A little bit of physics is a dangerous thing." * A bullet or piece of debris would likely leave a hole much smaller than the diameter of the tube. A breach 1/10th the diameter of the tube will admit 1/100ths as much the air. * Even if there was a whole-tube breach, the "wall of air" will rapidly slow down and smear out into…
> ala Thunderf00t Just watched one of his videos on this--interesting and thank you for the pointer. Agree with you on his overstating the deadliness of pressure pulses. 30 kg of TNT is a lot of energy, certainly enough to knock your infrastructure out of commission for a couple days. The "everyone dies if the tube is punctured" argument is hyperbolic, though. The materials science problem is the thermal expansion. A…
The Chuo Maglev makes the Hyperloop One look like a toy project. Watch the video. They have a production-quality train, with tourists and whiny kids riding it, going 500km/h. They've hit 603km/h in tests, but don't run it that hard normally. This is the first section of track between Tokyo and Osaka via Nagoya. Planned opening to Nagoya is 2027. Japan's Alps are in the way. They're tunneling straight through. Longest tunnel segment is 25km and it's being drilled now. 90% of the Tokyo-Nagoya segment will be in tunnel. Stations in Tokyo and Nagoya are under construction. The line will probably run 3-4 trains an hour each way, like the existing Shinkansen.
Hyperloop potentially has a higher speed to 900-1200km/h, but that may not be achieved in practice. The Chuo Shinkansen has a turn radius of 8km, and passengers don't have to be strapped in. Hyperloop would need 4x the radius to go twice as fast with the same ride quality. Laying out a route with a 24km turn radius severely limits where track can go.
Strapping everybody in and pulling 0.5G sustained is not going to go over with customers. Commercial aircraft usually stay within +-0.25G. Maybe 0.5G in mild turbulence, and customers don't like it.
But that's kind of what Elon Musk does: he Dunning-Krugers himself into a new industry every couple of years, using a simplified, undergraduate physics level of analysis to find something that (to an optimistic non-field-expert) looks like a better solution to the problem.
And the most annoying thing of all is that he usually succeeds. Often in spite of his original idea being technically wrong. For instance, Falcon 9 was supposed to be recovered with parachutes... that didn't work, and people who were working on vertical landing rockets told them that, but at the time Elon just rolled his eyes and said "just use parachutes." But SpaceX/Elon found out the idea didn't work and switched to the "correct" solution and got it to work operationally (and with paying customers) much faster than people who had been working on the problem for years before.
The moral of the story is that it's often better to be able to execute fast even if you start out wrong than to take your time with the right answer.
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sigh another "deadly wall of air" theory ala Thunderf00t? Hasn't this been debunked already? "A little bit of physics is a dangerous thing." * A bullet or piece of debris would likely leave a hole much smaller than the diameter of the tube. A breach 1/10th the diameter of the tube will admit 1/100ths as much the air. * Even if there was a whole-tube breach, the "wall of air" will rapidly slow down and smear out into…
> ala Thunderf00t Just watched one of his videos on this--interesting and thank you for the pointer. Agree with you on his overstating the deadliness of pressure pulses. 30 kg of TNT is a lot of energy, certainly enough to knock your infrastructure out of commission for a couple days. The "everyone dies if the tube is punctured" argument is hyperbolic, though. The materials science problem is the thermal expansion. A…
The heat will quickly conduct to the other side. It's one of the main reasons for choosing steel. Add white paint to that (or solar panels) and you'll have reduced heat absorption to a minimum.
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I remember that thread. Hilarious.
One of my favorites is on Slashdot. If you go there and search for 'VMware' then you can find it. When VMware was first announced and demoed, the commenters at Slashdot declared things like it was fake, it was stupid, it was a waste, it would never work, or that dual booting was a better solution. They largely concluded that virtual machines weren't a thing and happily congratulated themselves for their brilliant ins…
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Note that downthread, they've already moved the goalpost from "these pumps are technologically impossible" to "but they'll need a lot of them!" https://news.ycombinator.com/item?id=15459820
> Note that downthread they've already moved the goalpost from "these pumps are technologically impossible" to "but they'll need a lot of them!" I never said vacuum pumps are "technologically impossible". My original comment references the Space Power Facility [1] and categorises the vacuum problem as an engineering problem. A hard one, but engineering nonetheless. The comment you link to [2] replies to someone claim…
What exactly is the problem here? Is it because the top of the tube is exposed to direct sunlight? I thought it was supposed to be covered in solar panels anyway. Is it still a materials science problem if the tubes are shaded, because providing a structure that shades something with expansion from direct sunlight exposure seems quite a bit easier than to do so while trying to keep vacuum to a particular level.
The biggest problem people have with Hyperloop is because it certainly seems like Elon Musk just waltzed into the high speed rail debate and Dunning-Krugered some crazy scheme that doesn't look anything at all like conventional approaches to the problem and thus doesn't jive with any common sense we might have built up around different transport methods. But that's kind of what Elon Musk does: he Dunning-Krugers hims…