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Comment: Re: A giant lagoon dam (Score 1) 174

by Rei (#49167981) Attached to: World's First Lagoon Power Plants Unveiled In UK

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.

Comment: Re: A giant lagoon dam (Score 1) 174

by Rei (#49167805) Attached to: World's First Lagoon Power Plants Unveiled In UK

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.

Comment: Re:Viewing Launches (Score 1) 22

by Bruce Perens (#49166815) Attached to: SpaceX Falcon 9 Launches Dual Satellite Mission

With luck, they'll start incorporating our radio transceivers. I hear that SpaceX flies with several USRPs now, so that's not completely unrealistic. That might be as close as I can get. Anyone who can get me a base invitation, though, would be greatly appreciated and I'd be happy to do some entertaining speeches while there. I need a base invite for Vandenberg, too. I got in to the official viewing site for the first try of the last launch (and that scrubbed too), but this next one is on Pad 6.

Comment: Viewing Launches (Score 3, Interesting) 22

by Bruce Perens (#49164783) Attached to: SpaceX Falcon 9 Launches Dual Satellite Mission

I was in Florida to speak at Orlando Hamcation and went to see the DISCOVR launch at Kennedy Space Center. I paid $50 to be at LC-39 for the launch, an observation tower made from a disused gantry on the Nasa Causeway between the pads and the Vehicle Assembly Building. A crawler was parked next door! A hot sandwich buffet, chips, and sodas were served. It was cold and windy! I watched for a few hours and unfortunately the launch scrubbed due to high stratospheric winds.

The next day, Delaware North Corporation, which operates tourism at KSC, decided not to open LC-39 or the Saturn 5 center for the launch. This was the third launch attempt and I guess they decided most people had left. I was annoyed.

The closest beach was going to be closed in the evening, it's a sensitive ecological area. I ended up seeing the launch from Jetty Park. This turned out not to be such a great location, the tower wasn't visible at all and the first 10 seconds of the rocket in flight were obscured before we saw it over a hill.

What's a better viewing location?

Comment: Re:It's almost like the Concord verses the 747 aga (Score 1) 155

by Rei (#49158079) Attached to: Hyperloop Testing Starts Next Year

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.

Comment: Re:It's almost like the Concord verses the 747 aga (Score 1) 155

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) 155

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) 155

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) 155

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 2) 155

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%.

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