131–140 of 517 posts
Lots of comments about how this is not feasible, but wasn't spaceX's vision of a reusable rockets similarly not feasible at the outset and they've since been making some quite considerable progress towards this.
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I dont know if this an elephant in the room. I'm guessing engineers have thought about this and just not discussed it publicly. They have some pretty smart guys. Also to nitpick, from "the ends of a viable hyperloop track will have to move hundreds of meters" - this doesn't have to be true. There can be absorption points along the track. Overlaps. Or maybe they tunnel the entire way where its cooler. Or wrap the tunn…
> There can be absorption points along the track Sure, but these have to hold a vacuum. No one has figured out a way to do that.
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No. The paper gets this badly wrong. It looks only at the incremental thermal expansion between pylons, and neglects the fact that in a sealed tube the thermal expansion will be cumulative. "These would absorb the small length changes between pylons due to thermal changes, as well as long form subtle height changes." [emphasis added] The cumulative expansion is dealt with in a single sentence: "A telescoping tube, si…
sealed telescoping tube between pylons then?
Keeping a plain miles-long tube at at least 90% vacuum seems pretty hard to me, especially when needing to deal with evacuations and possible breakages. Why not divide the tubes into discrete sections gated by movable airtight caps that side away while passing through? If one section repressurizes due to evacuation or some other fault, so be it.
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> This sounds like such an insane proposition relative to the Dropbox we know today. Does it? If you used WebDAV then you can mount a share in Windows or Linux even over the Internet, and windows at least is good at caching it while you're offline for short periods. For someone who has their own always-on Apache it seems like this would replicate most of the use cases for Dropbox. I think the point that's being misse…
> For someone who has their own always-on Apache I’m just guessing on numbers, but that probably describes <1% of the population. Most people think Apache is a word used only to describe helicopters.
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What about building a high speed train? Proven technology, works in a lot of countries. LA to SF in 2 hours. Is it really that bad?
It'll be more like 3 hours, and it will end up costing around $100 billion. It would be dramatically cheaper and faster to subsidize free plane tickets between LA and SF for the next 50 years. HSR works well in places with high density and competent infrastructure construction strategies. California has neither.
$100bn is too expensive to make sense but I don't understand why it should cost that much. There are not that many tunnels needed, esp. if you start/end north of LA and south of SF. European rail projects are also expensive but still a fraction of the cost.
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Branson's missing a d from his almost nominatively-determining name — the guy's got a talent for self publicity over challenging the incumbency, which for the most part he hasn't since launching Virgin Airlines and Megastores, which were both back in the 80s.
"Branson's missing a d from his almost nominatively-determining name" Wat? Edit: This has been a fun puzzle. I read the Wikipedia article for "Nominative determinism" and I've been swapping the letter "d" into various positions of his first and last name trying to figure it out. No luck yet!
When are we going to address the elephants in the room? Just the tube alone: - largest pressure vessel in the world. How do you keep it at near vacuum? - Thermal expansion over such a large distance, especially if the top of the tube is warmer than the bottom. - Safety, how does an evacuation look like if the tubes are sealed?. There are many more. Some how I feel like this is a "pipe" dream. Lots of marketing, very…
Out of curiosity, have you ever built anything big? I say this because the tone of your comment is dismissive, however it seems quite low-effort. I can translate your criticisms into criticisms of building subways in 1863: - if you build a subway it will be the biggest underground railway ever built. - Rocks. They could fall in front of a subway car and cause a huge accident. - safety. what if all the lights and powe…
The engineering has never been a problem, vacuum-tube trains are an idea that's been around for centuries. [1] Removing friction and air resistance is a simple physics problem, and there are already operational maglev [2] trains so putting them in a low-pressure tunnel is not a major revolution. The real issue is the viability of such a transport because of the cost, complexity, and construction effort involved. We (…
"We can barely build a high-speed rail line effectively...' There is no high-speed rail line in the United States. The nearest thing to high-speed rail is the Acela Express, which hits 240kph on 40km of track. But this is weaksauce by modern standards.
Something I wrote a while ago.... w/ back of the napkin calculations....... Why I wouldn’t invest a money into Hyperloop - Stabilizing a single fault line risk pylon is more than $250K. - How many million are needed for vacuum pumps to evacuate 100+ million cubic feet of of pipe to 100 Pa? - Hot air discharge needs to go somewhere. For every 1 bar pressure, you need ~200 to ~400 cubic meters of volume which is larger…
Assuming your are correct and Branson knows it because he hired good engineering advisers. Why would Branson get involved ? - It is a cool project he wants to be part of and he is willing to pay to see. (I would probably do that) - The benefit is not to reach the goal but all the technology that will be invented trying to reach the goal.
Branson is notorious for burning other peoples’ money. Look at Virgin Galactic: it’s New Mexicans’ [1] and Floridians’ [2] tax money plus some duped Emiratis [3]. (They also pre-sold tickets [4].)
[1] https://www.theguardian.com/us-news/2015/oct/04/space-travel...
[2] http://www.airnewstimes.co.uk/space-florida-promises-virgin-...
[3] https://dealbook.nytimes.com/2009/07/28/uaes-aabar-takes-sta...