Follow Slashdot stories on Twitter


Forgot your password?

Slashdot videos: Now with more Slashdot!

  • View

  • Discuss

  • Share

We've improved Slashdot's video section; now you can view our video interviews, product close-ups and site visits with all the usual Slashdot options to comment, share, etc. No more walled garden! It's a work in progress -- we hope you'll check it out (Learn more about the recent updates).


Comment: Re:Just a distraction from the real fail... (Score 1) 39

by ultranova (#49157569) Attached to: Uber Discloses Database Breach, Targets GitHub With Subpoena

There could be hundreds of legitimate accesses of that file. If the hacker was indeed using a hidden IP address to access the database, but his real IP to download the gist, how are Uber going to determine that from all the other legitimate accesses?

Why would they? They'll simply rise a lawsuit demanding damages against them all. Since that's a civil suit, the accused need to prove their innocence, which will take years and absurd amounts of money - or they can settle out of court with Uber for a couple thousand dollars.

Nothing personal, just business.

Comment: Re:It's almost like the Concord verses the 747 aga (Score 1) 139

by Rei (#49157171) Attached to: Hyperloop Testing Starts Next Year

What sort of claim is that? Since when do oxygen masks need 20kPa to function? And secondly, if there's "problematic loading on the capsules" from too much pressure on the pressure-compromised capsule, then your pressure is also way too high inside. Which means that you've repressurized the tube way too much. So the solution is: Don't do that!

Comment: Re:It's almost like the Concord verses the 747 aga (Score 1) 139

by Rei (#49157159) Attached to: Hyperloop Testing Starts Next Year

Branching at full speed is probably not possible with the Hyperloop as designed; the skis are curved to match the diameter of the tube, with a ~1mm clearance with the tube surface, so there is no passive tube design that could accommodate a "switch". In order to continue from Section A to either Section B or Section C, you'd have to make an intermediate length of tube several hundred meters long that could be physically moved at one end from B to C, with sub-millimeter precision

Wait, meaning that while it's technically possible, but it'd be really tricky to accomplish? Gee, I wish I had written something like "Branching would be really tricky, but there's no physical barriers" at the top of my post ;)

The reason is threefold: drag continues to increase at higher speeds regardless of the speed of sound

Drag is reduced in the first place by using hydrogen even at a given pressure. And you can use 1/4th the pressure and still maintain lift because you're moving four times as fast. And given how few reboosts are needed from LA to SF in the base case, a few more per unit distance hardly seems limiting.

If you consider that the steel Hyperloop pipe draped across 30m-spaced pylons will approximate a vertical sine wave, then at 700mph the allowable sag is only about 5cm

Irrelevant because earthquakes impose far more deflection that you have to be able to counter (and that the proposal calls for countering) than a craft moving past.

Mechanical braking from 1500mph in the event of an emergency is also a non-starter

What, you're picturing drum brakes or something? You're moving at high speeds in a giant steel tube. Magnetic braking couldn't possibly be easier.

a 700mph capsule will incur about 2g's of aerobraking deceleration

Where are you getting this from? Even if the tube was instantly full pressure (which it wouldn't be), a streamlined shape will not experience 2Gs at 700mph, any more than a passenger jet losing full engine power does. And anyway, 10g horizontal is not fatal even if that was the case. The average untrained individual, properly restrained, can tolerate 10g for a minute without even loss of cognitive function.

Comment: Re:It's almost like the Concord verses the 747 aga (Score 1) 139

by Rei (#49157121) Attached to: Hyperloop Testing Starts Next Year

Not only that, but if your craft is travelling four times as fast, you're sweeping through four times as much gas per unit time to compress under the skis.

Hydrogen has all sorts of advantages. And the very low pressures prevent most of the negatives. The only one that I don't know about and would require testing would be what sort of reaction would one see as a craft moves past, with any residual oxygen. If I had to guess, I'd guess that you will get some combustion, but the craft moves past so fast and the mixture will decompress so fast, I would think the rate would be quite limited.

Comment: Re:It's almost like the Concord verses the 747 aga (Score 1) 139

by Rei (#49157115) Attached to: Hyperloop Testing Starts Next Year

First off, if servicing that requires full de/repressurization is some sort of frequent event, then the whole concept is doomed for reasons entirely unrelated to anything in this discussion. Secondly, 1/5 ton of hydrogen at industrial rates is about $200. Whoop-di-doodle-doo. And the advantage is being able to travel at mach freaking 4, not about the reduction of drag at a given speed (which is, FYI, true also).

Comment: Re:It's almost like the Concord verses the 747 aga (Score 1) 139

by Rei (#49157107) Attached to: Hyperloop Testing Starts Next Year

As someone else already mentioned, it uses low pressure air because the "trains" are ground-effect aircraft, not maglev. They need air.

Secondly, the pumping budget to overcome leaks is so small, both in terms of capital and ongoing costs, that you could increase them by an order of magnitude and not have any sort of practical effect on the budget. Whatever factor you increase over the baseline increases the factor you can replace air by. You don't need 100%.

Comment: Re:It's almost like the Concord verses the 747 aga (Score 1) 139

by Rei (#49157097) Attached to: Hyperloop Testing Starts Next Year

You think keeping hundreds of miles of tubing is really going to be cheap? Go look at a highway budget sometime.

Because Hyperloop is a highway? The closest analogy is a pipeline. Except that the environmental hurdles for building an oil pipeline raise the cost dramatically. Yet Musk's budget in Hyperloop Alpha is well higher than that of an equivalent diameter per mile.

Then consider ... Then consider ... Then consider ... Then consider...

And when you're done with that, then consider that every last thing you mention here was analyzed in detail in the Hyperloop Alpha proposal, which you apparently never read.

Comment: Re: Authority (Score 5, Interesting) 119

Does the FCC even have the authority to do that? Under what legal theory does an unelected federal regulatory commission have the authority to overrule state government laws on matters of state government interest? Don't get me wrong, I'm glad to see such laws go, as they're a major competition inhibitor, but how does the FCC have any authority in this?

Congress has clear authority to regulate interstate commerce, under the Constitution. Unlike some other things Congress has tried to regulate, it is very clear that the Internet is interstate commerce.

Having said that, the question that remains is whether Congress can delegate their lawmaking authority to some government bureaucracy. The correct answer to that question is probably no. But I know there are many people who would argue that point.

The last time the courts ruled on this, the ruling was that the FCC had ceded power and couldn't claim it back without the will of god. Or Congress, or something.

Not even close. The Supreme Court ruled that the FCC could not impose the rules it had tried to impose, BECAUSE it had not classified internet companies as Title II common carrier communications companies. So what the FCC did here, quite properly (if you accept that they have any authority to do it at all), was to re-classify internet providers as Title II common carriers.

There are many implications to this that people haven't been discussing much. It depends on the exact language of the rules when they go into effect. But the OLD rules for Title II common carriers stipulated that your communications can't be legally "intercepted" without a warrant. So deep packet inspection by ISPs is probably out the window.

Comment: Re:fees (Score 1) 360

It is a big fucking deal because there are long running threads of economic thought which oppose capitalism yet support free markets, and to conflate the two (and equivalently to conflate socialism with a command economy) creates a false dichotomy between capitalist free markets and statist socialism, ignoring and erasing the possibilities of non-capitalist free markets and non-statist socialism.

You're arguing against something I didn't even say. Why?

I'm not going to even bother dignifying the rest with an answer. I didn't see anybody dispute any of this so there is no point in arguing about it.

Kiss your keyboard goodbye!