The number of grammatical cases is irrelevant. Question: What's the difference between a grammatical case without stem changes and a postposition (opposite of a preposition? Answer: A space.

  That which is challenging, apart from stem changes, is the same thing that is challenging with helper words in general: when to use what with what. Picture a person learning English and trying to remember what to use with what. "I was scolding her.... over it? for it? about it? to it? around it?" "We were unhappy.... over it? for it? about it? to it? around it?" "She was dedicated.... over it? for it? about it? to it? around it?" And so forth. It's the same for people trying to learn which declension case to use in which context. But if the declensions are just suffixes without stem changes, then they're no different from postpositions. And often stem changes where they occur follow pretty predictable rules, often for pronunciation reasons.

I'm sorry, but I agree with that. If you on the UK want us to dam up our rivers and build roads out to geothermal areas and tap into our resources, and raise our local power prices in the process, all for the benefit of the UK, our government better damn well profit as much as possible from it and reduce our taxes / improve our services in exchange for that.

Unfortunately, xB and xD do not agree.

Readily replaceable intakes?

Seriously, fuck the fish.

You could find fans for a plan like that...

Better negotiate the contract during a Sjálfstæðisflokkurinn / Framsóknarflokkurinn (conservative) government. Samfylkingin would approve it under the condition that the Icelandic government's share of the sales are so high that you would barely save any money on the imported power, and Vinstri Grænir would outright reject it no matter what you offered. But Sjálfstæðisflokkurinn and Framsóknarflokkurinn would let you dam up whatever rivers you want and take gigawatts of power in exchange for a handful of shiny trinkets and a couple magic beans.

And how do we know that the real benefit doesn't come from hitting yourself with birch branches?

zblockquote>See: Cabin_Pressurization [wikipedia.org]

A person needs at least 20kPa *from the mask to breathe*. Not 20kPa *ambient pressure*. Please learn to read.

The "problematic loading on the capsules" is from the high speed aerodynamics, not the ambient pressure

Aerodynamic loading = pressure. If you have high loadings, you have high pressures. Period.

Are you talking about what I was talking about? I was talking about an electric motor, not a fuel-driven one.

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!

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.

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.

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).

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%.

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.

I don't think it does but for the definition to work it will have to have some sort of sensible criteria to separate them from asteroids

It does - gravity high enough to deform it into a sphere.