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Fascinating Rosetta Image Captures Philae's Comet Bounce

stevelinton Re:Fucking disaster (69 comments)

Really?

Hard to know where to start. Firstly the whole landing was just a small part of the mission. The orbiter is still up there and, all being well, will follow the comet in to
perihelion, observing all the way.

Secondly, think about the trade-offs of planning a space probe. You can make things more robust and more redundant, design more conservatively, etc. reducing the risk of things failing, but that costs you mass and power (and possibly money) which are rigidly limited. So you would have to take fewer instruments. The design optimises the expected science return by taking some risks.

The lander was intrinsically high risk, because no one had any idea what the surface of a comet is like. They had to gave it a bunch of different ways of hanging on designed around some plausible guesses. The lander has no propulsion at all (those mass trade-offs again), so it has to put up with wherever it hits. They knew solar power on the surface was uncertain, so they had enough juice in the non-rechargable battery to do the highest priority science.

In the event, two systems failed -- the cold gas hold down thruster and the harpoons. No one knows why yet, but building systems on a very tight mass budget that can work after 10 years in space is not easy. In addition, the surface of the comet seems to be harder than anyone really expected.

Given the challenges, getting any science at all back from the lander is amazing and a bonus to the main mission which is the orbiter.

about a week ago
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Denmark Faces a Tricky Transition To 100 Percent Renewable Energy

stevelinton Re:Are renewable energy generators up to task ? (488 comments)

My guess, before 40 years there'll be a spray-on solar PV coating you can put on your existing roof. Basically like a printable OLED in reverse. We shall see.

about two weeks ago
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Denmark Faces a Tricky Transition To 100 Percent Renewable Energy

stevelinton Re:Are renewable energy generators up to task ? (488 comments)

The cost is down to reasonable levels already, and a lot of it is installation, which would be much reduced if you were reroofing or building new anyway. But I was looking 10-15 years out, by which point they are on track to be so cheap they probably undercut decent slates.

about two weeks ago
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Denmark Faces a Tricky Transition To 100 Percent Renewable Energy

stevelinton Re:Real problems, but there are also solutions (488 comments)

HVDC (high voltage DC) transmission lines are economical up to several thousand miles. Hydrogen pipelines even further. You can bring solar North from New Mexico or hydro down from Alaska to the great plains.

You can also move demand. The Icelandic economy is an interesting one. Apart form a certain amount of dried cod, they basically have only one natural resource to export -- energy. They have geothermal and hydro coming out of their ears. However they're in the middle of the Atlantic, so they can't build power lines to anywhere with demand. So they have to find proxies for the energy. They import Bauxite and export aluminium and a few similar processes. They are looking very hard at exporting liquid hydrogen, or chemical proxies for hydrogen, like ammonia. The most fun one though is search results. People are building compute farms their and exporting the results.

about two weeks ago
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Denmark Faces a Tricky Transition To 100 Percent Renewable Energy

stevelinton Re:Are renewable energy generators up to task ? (488 comments)

New and replacement roofs could be dealt with by building codes. That gets you a lot of the way in a few decades.

In my view, saving the planet from catastrophic warming is a totally appropriate use of government power.

about two weeks ago
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Denmark Faces a Tricky Transition To 100 Percent Renewable Energy

stevelinton Re:Are renewable energy generators up to task ? (488 comments)

The cost (per GW) is coming down incredibly fast at the moment as production ramps up. Pretty soon it will be comparable to new
coal plant, even ignoring carbon costs.

You are right that not every roof is ideal. With current technology you can usefully cover about half of roof space. For new houses it's not hard to use a single-pitched roof design facing South for many buildings (or a flat roof on which you can put pitched panels.

Eventually, I suspect the solar cell becomes a layer that you paint or print onto every roof tile you make, and is probably cheap enough that you just use them everywhere and don't worry about it.

about two weeks ago
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Denmark Faces a Tricky Transition To 100 Percent Renewable Energy

stevelinton Re:Cost nothing to run? (488 comments)

Modern designs don't have gearboxes.

about two weeks ago
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Denmark Faces a Tricky Transition To 100 Percent Renewable Energy

stevelinton Re:Real problems, but there are also solutions (488 comments)

There will need to be a range of solutions certainly, but there are lots of candidates. They need proving out at scale, and not all will succeed but a few examples:

Pumped water storage will hold gigawatt hours easily,
hydro plants can be designed to let you take their (fairly fixed) annual capacity out in bursts, if you like..

  Denmark is a bit flat, but it's also not far from Norway.

On a timescale of days you have some warning from the weather forecast, so you can shut down some industrial processes
and you can spin up cheap gas plants. Since the gas plant is just backup it can be relatively cheap and inefficient. If you are that purist, you can regenerate the methane from CO2 and hydrogen (from electrolysis) or make it from organic waste.

It's not simple, but the existing grid isn't simple. We need to devote the same energy, plus modern IT to solving a slightly different problem.

about two weeks ago
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Denmark Faces a Tricky Transition To 100 Percent Renewable Energy

stevelinton Real problems, but there are also solutions (488 comments)

There are real problems, but there are also solutions. You can do much more to control demand on shortish timescales. No one will notice or care if the aircon or heating to their huge office building switches off for a few minutes, or if their electric car only charges 90% of minutes it is plugged in for.

about two weeks ago
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Denmark Faces a Tricky Transition To 100 Percent Renewable Energy

stevelinton Re:Are renewable energy generators up to task ? (488 comments)

There is a tool at http://re.jrc.ec.europa.eu/pvg... for estimating the lost efficiency of solar panels due to clouds etc. For Denmark it gives about 27%. From wikipedia efficiency of commercial cells is typically 21.5%, so about 200 W/m^2. So after losses lets say 140 W/m^2 times half the time (the sun is up on average) so 70 W/m^2 average over the year. There are about 7000 hours in the year, so we get about 500 KWh/m^2/yr.

The total energy consumption of Denmark (wikipedia, and probably not including vehicle fuel) is about 200 TWh/yr (and dropping steadily), so that's about 400 million m^2, or a 20 km square.

Now no one is suggesting using purely PV solar for a whole country, but it does suggest that replacing all roofs with solar roofs, or covering a few large redundanct industrial parks would get you quite a lot of the way.

Actually Denmark is open and windy, so wind is a much better call there.

about two weeks ago
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Earth's Oxygen History Could Explain "Darwin's Dilemma" In Evolution

stevelinton Re:A matter of perspective (78 comments)

There is fossil record of bacteria back to over 3.5 billion years before present.

about two weeks ago
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Earth's Oxygen History Could Explain "Darwin's Dilemma" In Evolution

stevelinton Re:A matter of perspective (78 comments)

There were eukaryotes and photosynthesis by 3 billion years before present. They became slowly more sophisticated but nothing fundamentally new happened until about 700 million years bp.

about two weeks ago
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Fusion Reactor Concept Could Be Cheaper Than Coal

stevelinton Re:The $50,000 question... more energy out than in (315 comments)

In fact we do. If you look at the corona of the sun, little bits of plasma get trapped in magnetic fields and heated to hot that fusion happens. Since the magnetic fields are shifting, they are not contained for long, but they are. By controlling the fields, we can get longer containment.

about a month and a half ago
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Fusion Reactor Concept Could Be Cheaper Than Coal

stevelinton Re:The $50,000 question... more energy out than in (315 comments)

You're confusing magnetic and inertial confinement fusion. The tiny gold capsules are inertial confinement -- you zap the capsule with a short and very intense burst of energy, compressing it and getting fusion until it flies apart. Essentially a very very tiny H-bomb.

In magnetic confinement you hold the a much less compressed but very very hot gas in place with magnetic fields while it fuses relatively slowly. Current experimental designs tend to run in pulses of a few seconds or minutes, but engineering refinements should lead to ones that burn continuously, with more fuel being added and "ash" (helium) removed.

As you make tokamaks bigger they get more efficient, because there is less surface for the energy to leak out of, compared to the volume of plasma. ITER is designed to achieve scientific break-even -- more power out of the reaction than is used to run the magnets etc. The next stage will be a reactor that achieves actual power generation -- more electricity out the whole plant than goes in. This is harder because or turbine inefficiency etc. Because of the scaling up thing, if these do produce useful power it will be gigawatts.

What UW have is a variation of the magnetic confinement setup, generating the magnetic fields in a different way. Their calculations suggest that it will scale up cheaper and efficient than the current favourite design (a tokamak), but this remains to be demonstrated.

about a month and a half ago
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Solar Could Lead In Power Production By 2050

stevelinton Re:Electricity from Oil? (167 comments)

Depends where you look. The atmosphere hasn't warmed, but the oceans have. All the models and evidence suggest that this shift is cyclical and will reverse.

about 2 months ago
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WD Announces 8TB, 10TB Helium Hard Drives

stevelinton Re:When can we stop selling party balloons (296 comments)

Interesting. The last sentence on the Wikipedia page for helium:

"Helium is a finite resource and is one of the few elements with escape velocity, meaning that once released into the atmosphere, it escapes into space."

So how does that work?

At a given temperature the typical velocity of a gas molecule depends on its mass. The lighter, the faster.
Helium is the only gas molecule that is stable in the atmosphere and has a typical velocity near the top of the atmosphere that is faster than Earth's escape velocity, so it slowly diffuses up to the top and then is gradually lost to space.

about 3 months ago
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The Star That Exploded At the Dawn of Time

stevelinton Re:Why can't hydrogen cool? (55 comments)

Basically the conditions (temperature, density, amount of ionizing radiation around) thought to apply, the gas would be made up of atoms that tend to simply bounce off one another when they collide. This doesn't change the total energy in random motion of the cloud, ie the temperature.

More complex atoms or molecules can interact in more complicated ways when they collide, so that part of the energy ends up as vibration in a molecule, or extra energy of an electron in an excited state. These vibrating molecules or excited atoms then relax back to their ground state releasing a photon and so actually cooling the cloud.

about 3 months ago
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Ask Slashdot: Do 4G World Phones Exist?

stevelinton 4G only in big cities (259 comments)

There's no 4G outside Edinburgh & Glasgow at the moment I believe, but there is good 3G covering pretty much all the Universities and their surroundings and good wifi in the university buildings. If she's coming to St Andrews (statistically likely) there is definitely no 4G.

about 6 months ago
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The Rise and Fall of Supersymmetry

stevelinton Re:is there an xkcd comic for this? (138 comments)

. For one thing, string theory will probably need to be scrapped.

Not because of this. Supersymmetry and string theory address different problems and are more or less independent.

about 9 months ago

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