Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Hyperloop

spacex.com

Post reply on HN
Print view View original

941–950 of 983 posts

Re: Hyperloop

#941

Post by foley »

fooqux wrote: post #869
lessnonymous wrote: post #505

Earlier quoted context omitted.

2.8/km² Australia And here you can travel from most parts of Melbourne to most parts of Sydney with just two train changes. One at a Melbourne hub to the interstate trains and one at Sydney to the local system. Even so, we feel our train systems suck too.

That figure is meaningless considering Australia is a large piece of largely uninhabited land, with two or three metropolitan areas on the coasts. Unless you can take a train into the center of Australia, in which case I apologize.

Actually you can, rather expensive though.

Re: Hyperloop

#942

Post by jarek »

FrojoS wrote: post #923
jarek wrote: post #899

Earlier quoted context omitted.

In case it wasn't clear, I was voicing my doubt that any company would actually build such a line for $6B claimed by Musk, not an opinion that it was unduly expensive.

Infrastructure projects like this a usually not financed by companies. The I-5 wasn't either.

And that was a poke at Silly Valley's tendency to see private funding and companies as solution to all of its woes (Sidecar, Avego, et al) ;)

Re: Hyperloop

#943

Post by ceol »

vannevar wrote: post #891
mncolinlee wrote: post #877

Earlier quoted context omitted.

Having run for state office three times in Minnesota, I can respond to some of this. Politicians aren't all afraid to take risks, especially when they believe a particular policy they like will live on and be remembered. Our former governor Jesse Ventura overcame incredible resistance and media scorn to get our first light rail line built. Almost all casual observers thought major health care reform was impossible in…

Though I'm not sure you intended it, this is an excellent summary of why the US doesn't have a decent mass transit system. Even if you get past the formidable political opposition to any public transit system, you must contend with a coalition of that opposition plus an assortment of interests that want a different system, possibly because it looks better on paper (hey, Hyperloop!) but more commonly because it benefi…

The US will never have a decent mass transit system due to its sheer size.

Re: Hyperloop

#944

Post by dudus »

dragonwriter wrote: post #361
dudus wrote: post #333

In Brazil the building of a new high speed train between São Paulo and Rio was just delayed for the third for for lack of interested companies to build the system. The estimated cost is at US$ 17B. There are not earthquakes in Brazil and the length should be around 500km. It seems like a better candidate than SF-LA. just saying,

California is more able to attract interested private operators because the availability of potential passengers with money to spend on fares is substantially greater.

I thought high speed train was supposed to be cheaper than airplane. Or at least stay at the same price range.

São Paulo - Rio is actually the 3rd most busy airplane route in the world. With over 7.7M passengers in 2012. [1]

[1] http://www.amadeus.com/web/amadeus/en_US-US/Amadeus-Home/New...

Re: Hyperloop

#945

Post by JulianMorrison »

DonPedro wrote: post #931
eru wrote: post #916

Earlier quoted context omitted.

You could just build the tubes bending upwards slightly, so that the sag will pull them straight.

No you could not. The steel tube will expand and contract as temperatures change. Along most of the route, that longitudinal movement of the tube will be in the 10s and 100s of feet, which means that the "valley" could be anywhere on the tube according to temperature.

Also, tubes will resonate and vibrate as vehicles go by. This could be actively damped at the pylons though, like they already considered doing for ground subsidence.

Re: Hyperloop

#946

Post by DannyBee »

thrownaway2424 wrote: post #830
DannyBee wrote: post #822

Earlier quoted context omitted.

We'll have to agree to disagree. I've been in plenty of places like SF, which, when under pressure, simply make up statistics or change what they mean. It's simply not a "fact beyond argument", when the only source of this "fact" are a group with a very strong vested interested in high numbers and a history of not truth telling. The 100-200 units number only came out after a lot of pushing. They claim there are 22,00…

I'm sorry that you don't know what it means for construction to be approved. It means the units will be built in the future. This isn't Sim City. If you are feeling exceptionally lazy and only have time to look outside your bubble once, go to Market between 7th and 9th. The new building on 8th between Market and Mission has over 1900 units (over 1400 units net of what were demolished) and the one at 55 9th Street has…

You seem to be deliberately misrepresenting what i'm saying in order to argue about things i'm not claiming, so i'm just not going to continue this discussion.

You also seem like a bit of a dick.

Re: Hyperloop

#948

Post by PeterisP »

mhandley wrote: post #736
adventured wrote: post #649

Earlier quoted context omitted.

This system would seem very weak to criminals / terrorists / whatever firing bullets at it. It would be exceptionally difficult to track where the shot/s came from, and it would cause serious pressure problems.

Even if the pressure problems could be countered, a bullet hole is likely to leave a pretty ragged profile on the inside of the steel tube. The specification calls for the air bearing skis to ride 0.5 to 1.3mm off the tunnel wall. They'd need to be pretty robust to take hitting the ragged edge of a bullet hole at 700mph.

The specification for the tube is inch-thick steel. Most bullets not meant for tanks would leave a dent, not a hole.

Re: Hyperloop

#950

Post by DonPedro »

krasin wrote: post #904
VladRussian2 wrote: post #903

Earlier quoted context omitted.

Mach value is lower for lower pressure, about 250 m/s for hyperloop proposal

Wolfram Alpha disagrees. It says: Mach(20 C, 1 atm): 343.051 m/s Mach(20 C, 0.1 atm): 343.182 m/s Not much higher, but definitely not lower. http://www.wolframalpha.com/input/?i=speed+of+sound+in+dry+a... Unfortunately, it refuses to show Mach(20 C, 0.001 atm), since the lowest supported pressure is 0.098 atm.

I'll go out on a limb here and wager that SpaceX engineers know the Mach value for various permutations of temperature and air density. But I might be wrong...
Post reply on HN