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Comment Re:flywheel (Score 4, Interesting) 245

Pumped storage costs about $200 million per GWh of electricity stored to build. It needs specific geography, high and low reservoirs close to each other to reduce losses pumping water uphill over long distances. It also needs a guaranteed supply of water, lots of it and the sunny parts of the US where large amounts of solar power are being generated are distinctly lacking in water to the point of being either deserts or often in drought conditions during the summer. Pumped storage is also lossy, typically about 65% efficient round-trip.

Mass battery technology costs about ten times as much as pumped storage ($2 million per MWh for sodium/sulfur batteries from NGK), flywheels are a bit less but still a lot more than pumped storage. Cheaper methods of energy storage like compressed air tend to be very lossy.

Grid gas, coal and nuclear generators don't need storage as they either run flat out to meet the instantaneous demand and they can throttle back in quieter times. At the moment intermittent wind and solar generators use the grid as free storage but the more intermittent power that is added to the generating mix the more that storage will be needed to deal with peak inputs and debits. Getting wind and solar farm operators to pay for this extra storage probably isn't going to happen, sadly.

Comment Re:Since nuclear is "too cheap to meter"... (Score 1) 258

The taxpayers want cheap electricity which is why coal and gas are the big players in the US electricity generating market at the moment despite the deaths and sickness extracting and burning those fuels involves. The nuclear industry paid the waste disposal levy (about 50 cents per nuclear MWh IIRC) by adding it to the bill the consumers paid for their electricity, sent the money to the US Government which said "Thanks very much for the free money" and didn't hold up their end of the bargain by taking away and properly disposing of the spent fuel as the law requires. This went on for decades, the generators started having to spend money on on-site long-term storage (dry-casking) and went to court to get permission to stop paying the levy too. They've been dancing like crazy (to use your metaphor) while the Government has been playing the part of a gold-digging wallflower.

As for disposal costs Finland is building a hard-rock geological repository for their spent nuclear fuel at the moment. It's basically a long spiralling deep tunnel at Onkalo adjacent to one of their nuclear power plants. Cost of building it and operating it for a century is currently calculated at 818 million Euros, they have 1.4 billion Eu saved already in their waste disposal fund from previous electricity levies and of course that fund will continue to increase over the next century anyway.

Comment Re:Since nuclear is "too cheap to meter"... (Score 4, Interesting) 258

US law requires the US government to collect and deal with spent nuclear fuel as it is regarded as a stategic material. The same law requires the power generating companies to pay a levy to the government per MWh of nuclear electricity generated for this to be done. As I recall they've paid (or rather the consumers have paid) over $30 billion since the levy was introduced.

The power companies are now paying for on-site dry-cask storage of spent fuel since the US government isn't actually doing what they've been paid to do, that is take away the spent fuel and deal with it. They have stopped paying the levy after a court agreed with them and they are using some of those savings to fund the local dry-cask storage they need.

The taxpayers have benefited from over $30 billion of free money gifted to the government by the electricity generating companies, it's not the other way around.

Comment Re:Thrust also matters. (Score 1) 211

The thrust to weight ratio of the rocket motor only really matters near the end of a burn when the motor weight becomes a significant part of the total vehicle mass at that time after hundreds of tonnes of fuel and propellant have been expended. It's a good thing to have a lightweight motor but shaving a hundred kilos off the motor mass isn't as important as boosting the Isp by, say, ten seconds as that boost improves the performance all the way through the burn and has a much bigger impact on payload to orbit with given hardware. SpaceX have been working hard to improve Isp, of course -- the Merlin first-stage 1D motors are a lot better than the original flight motors they started their operations with and they now have optimised upper-stage versions of the 1D for vacuum with improved Isp figures.

I know other manufacturers have looked at methane-oxygen engines in the past but not progressed with them. Why they didn't I'm not sure. LOX/RP-1 has a good track record and decades of actual operation to work with (which SpaceX took advantage of), LOX/CH4 is more of a leap in the dark. Building a big LOX/CH4 motor as the first flight item is another big step and obviates the cheap multi-motor Falcon vehicle platform SpaceX have been developing over the past few years.

Comment Re:Competition is good. (Score 1) 211

Most new airline designs are slower than 1970s models (and that's not including Concorde and the Tu-144 either), for fuel efficiency reasons. They're much more reliable and safer, can carry more passengers and freight further per tonne of fuel, cheaper to operate and cycle gate-to-gate, cleaner, quieter etc. but not faster.

Comment No miracles (Score 4, Informative) 211

There are no miracles in rocket engine design. The RD-180 has pretty much the best performance to be wrung out of a sea-level-to-altitude LOX/RP-1 motor in terms of efficiency. SpaceX is still playing catchup in that area, trading off the lower cost per Merlin motor for a lower Isp from a simpler design.

As for the Raptor the "new" liquid-methane/oxygen fuel mix it will burn has the potential to produce a higher Isp than the current mainstream LOX/RP-1 mix used in motors like the Merlin, the RD-180 etc. but it comes with downsides -- it means a redesign of the rocket structure to support fully cryogenic tankerage (although not requiring the sorts of extreme temps or processing LH needs), launchpad facilities for fuelling and defuelling rockets will need to be revamped, liquid methane is half the density of RP-1 so the tanks and the rocket structure need to be larger and heavier to contain equivalent amounts of fuel and so on.

Comment Re:Proves point (Score 4, Informative) 140

The final stage that was meant to put the two satellites into their proper orbit was a Fregat-MT upper stage built by the Russians and supplied as part of the complete Soyuz stack.

The satellites have their own motors used for station-keeping, trimming orbit etc. but I doubt they have enough fuel to move themselves to the planned orbit. Even in the wrong orbit the satellites will still work and provide position data to GPS receivers but they will not provide the sort of whole-sky coverage originally planned. They are high enough that they're not likely to deorbit within the next few years at least.

The complete Galileo constellation is intended to consist of twenty-four working satellites and six spares so ESA and the Galileo consortium have some leeway. They might revamp the deployment schedule to use fewer Soyuz launches and more Ariane V launches for the rest of the constellation though unless the Russians can explain what went wrong with the Fregat-TM and guarantee it won't happen again.

Comment Re:Pick your units of radiation... (Score 2) 190

Ten trillion nuclear disintegrations of potassium-40 occur in a cubic kilometre of seawater every second. A single nuclear disintegration per second is a becquerel (Bq). Usually Bq are qualified by being associated with a mass or volume, Bq/litre or Bq/kg. Radioactivity in seawater is usually measured in terms of litres but if you make the sample size big enough (cubic kilometres) the numbers can look really scary.

Comment Re:Pick your units of radiation... (Score 4, Interesting) 190

A cubic kilometre of seawater contains about 10 trillion becquerels of the naturally-occurring potassium K-40 isotope. That's ten fucking disasters per cubic kilometre using your scale and there's a lot of seawater on this planet (1.3 billion cubic kilometres according to most sources).

Comment Re:Aluminium (Score 1) 365

Modern nuclear reactors can load-follow quite well, swinging output by 30% in fifteen minutes thanks to newer control tech and a lot of operational experience over the past 50 years. Load-following can even be done somewhat with older second-generation LWR plants. It's not actually done much since baseload nuclear power is very cheap in terms of fuel consumption and refuelling tends to be done at fixed intervals anyway. Other thermal generators like gas where the fuel is a major part of the cost of operations are normally used to top-up baseload stations -- in the UK the nuclear generators run full-out as much as possible with gas filling in much of the rest and coal as a cheap backstop, limited by pollution and carbon controls.

Comment Re:Aluminium (Score 1) 365

Most renewable generators get a guaranteed minimum payment for electricity they feed into the grid (in the UK where I live windfarm operators get about £145 per MWh) so the "excess" production is not free, it is paid for by the grid operators and ultimately the consumers even if it is not needed sometimes. If the renewable generators stored their excess production and dispatched it into the grid at times of low output that would be a different story, but that would cost them money so they don't do that. The round-trip efficiency losses are even more reason for them not to build storage into their operations.

Comment Re:Aluminium (Score 3, Informative) 365

Storage costs money. Lots of storage costs lots of money. Storage wastes energy too -- pumped hydro, the cheapest form of bulk energy storage has an input-to-output efficiency of about 65 percent. Baseload coal, gas and nuclear generation doesn't need storage to be useful and meet demand 24/7/365 unlike intermittent renewable generating capacity, but no-one ever adds the cost of storage to the cost of renewables when comparing prices.

Comment Re:Serously? (Score 1) 398

You mean like the major Japanese Army command centre in Hiroshima? Or the extensive Naval dockyards and repair facilities in Nagasaki, close to where the Allied invasion was going to hit the beaches in Kyushu? Nagasaki was actually a secondary target due to bad weather over the primary target, a place called Kokura Arsenal which might give you an idea why it was on the target list.

In reality the atomic bombs were used because they were ready to be used, just one more wonder weapon in a war filled with wonder weapons. They contributed to the decision by the Japanese War Party, the military/political group in power at the time, to surrender but it was mostly down to the Russians declaring war on Japan on the 9th of August 1945 and promptly destroying the last major Japanese army outside Japan itself, the million plus Manchurian occupation force with embarrassing ease.

Comment Re:Early days of KIA repeated (Score 1) 431

Diesel engines typically run at twice the compression ratio of a gasoline/petrol engine. They also last a lot longer than petrol engines in my experience. This may be because they are designed to deal with the higher compression and greater loads on crankshaft bearings etc. from day one. They do tend to be heavier than gasoline engines of the same power and torque though.

Submission + - Ask Slashdot: What's the best rapid development language to learn today? 2

An anonymous reader writes: Many years ago, I was a coder—but I went through my computer science major when they were being taught in Lisp and C. These days I work in other areas, but often need to code up quick data processing solutions or interstitial applications. Doing this in C now feels archaic and overly difficult and text-based. Most of the time I now end up doing things in either Unix shell scripting (bash and grep/sed/awk/bc/etc.) or PHP. But these are showing significant age as well.

I'm no longer the young hotshot that I once was—I don't think that I could pick up an entire language in a couple of hours with just a cursory reference work—yet I see lots of languages out there now that are much more popular and claim to offer various and sundry benefits.

I'm not looking to start a new career as a programmer—I already have a career—but I'd like to update my applied coding skills to take advantage of the best that software development now has to offer.

Ideally, I'd like to learn a language that has web relevance, mobile relevance, GUI desktop applications relevance, and also that can be integrated into command-line workflows for data processing—a language that is interpreted rather than compiled, or at least that enables rapid, quick-and-dirty development, since I'm not developing codebases for clients or for the general software marketplace, but rather as one-off tools to solve a wide variety of problems, from processing large CSV dumps from databases in various ways to creating mobile applications to support field workers in one-off projects (i.e. not long-term applications that will be used for operations indefinitely, but quick solutions to a particular one-time field data collection need).

I'm tired of doing these things in bash or as web apps using PHP and responsive CSS, because I know they can be done better using more current best-of-breed technologies. Unfortunately, I'm also severely strapped for time—I'm not officially a coder or anything near it; I just need to code to get my real stuff done and can't afford to spend much time researching/studying multiple alternatives. I need the time that I invest in this learning to count.

Others have recommended Python, Lua, Javascript+Node, and Ruby, but I thought I'd ask the Slashdot crowd: If you had to recommend just one language for rapid tool development (not for the development of software products as such—a language/platform to produce means, not ends) with the best balance of convenience, performance, and platform coverage (Windows, Mac, Unix, Web, Mobile, etc.) what would you recommend, and why?

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