With nukes those fuel rods are decaying over time no matter what you do so that's another reason to have them run flat out until it's time to shut down for maintainance or refuelling.
Technically, yes they decay, but no it doesn't actually have a significant effect. U235 (the fissile fuel in enriched uranium) has a half life of 700 million years, so even if you waited that long, you'd still have half the fuel left. MOX uses a mix of U235, Pu239, and U233. The shortest (Pu239) has a half life of 24,000 years, so even if you left it standing for 100 years, you'd still have 99.7% of the plutonium left. The other sort-of fuel is U238, which absorbs a neutron turning into Pu239 which is a fuel during the reactor operation. U238 has a half life of 4.5 billion years.
In other words, you can leave the fuel sitting around for human timescales without a problem or significant loss.
Unused fuel rods don't decay much, it's true, but once you start using them, they fill up with short-lived fission products which will decay and produce heat at a high level over days and weeks, even if you quench the fission reaction entirely. You have to remove that heat (which is why some form of cooling is needed in nuke plants for weeks after they shut down to stop the fuel melting or burning) and so it is economically very desirable to use it to generate power and to use that power.
So using a fission reactor to respond to day or week long variations in demand is horribly inefficient and expensive. Gas plant is much easier to start up and shut down, as in wind, while solar (PV to be specific) generates power when it does, but uses no fuel (except hydrogen in the core of the sun, which is not in shortage) so you can just dump the power.
If people thought sea level was rising and it isn't they will admit to being wrong about that.
To convince people that the whole picture of AGW is wrong in broad terms, would need a much wider-ranging set of inconsistent data, and preferably an equally consistent model that fitted all the observations better and either fitted, or revised, known physics, in a sensible way.
Just looked. There are small differences. I see about.1 degree at each end difference between the 5-year means in the two graphs, well within the error bars. If you have the underlying numbers we could look at the statistical signiificance of this
However, what you need to understand is that there is not a single thermometer somewhere that measures the global temperature. There are thousands, and the same ones have not been used consistently in different ways across 100+ years. They are moved, replaced, read at different times, etc,. etc.
So the data in either of those graphs is the result of a lot of difficult and careful analysis (which is published and peer-reviewed). From time to time improvements in theory, more computing power and new data (for instance about the behaviour of the instruments) lead to improvedments in the techniques of that analysis. Since everyone has been pretty cautious, trying NOT to be alarmist, these improvements usually make the picture more alarming, as some of the caution proves to have been unnecessary.
So no smoking gun just science at work. All the information you need to follow the process in detail is in the public domain, although you need to be prepared to read a few tens of thousands of pages of hard maths to make sense of it.
I should say by the way that sometimes people do make mistakes. They range from the trivial (typing 2035 instead of 2350) to serious, but they are picked up and corrected pretty quickly by other scientists.
We can deduce (from the properties of the cosmic microwave background) the ratio of photon-interacting mass with gravitational mass in the very early universe. We can also deduce (from the relative proportions of light isotopes in the universe) the absolute density of baryons.
These two match up near enough.
So we know there are baryons we haven't spotted yet, and we know that there isn't much apart from baryons around that interacts with photons.
Whatever standard you adopt needs to be reproducable within the limits of the best current measurements by any other technique. Otherwise when people want a stable reproducible result they will use the other technique and the standard won't have worked. Measuring volume of water, purity, temperature and pressure is just not precisely reproducible enough
e and pi are numbers. You need actual physical constants like the mass of a proton or Planck's cpnstant.
It is indeed just a matter of choosing "close enough factor", but close enough (to avoiding needing to redo or change any measurements that anyone uses) is pretty close, about one part in 100 billion. Being sure that we have done that is the hard part.
Instead of putting just one camera (which would definitely NOT gather enough light at this size), they're massively parallelized it. They've put millions of pinholes camera on the chip and are using post processing to reconstruct the final image out of the tons of tiny pinhole views.
I think there are more pinholes of a variety of different shapes, and fewer sensor pixels than your description might suggest.
Anomaly is a technical term. If you want to compare how exceptionally warm January 2016 was with how exceptionally warm September 2015 was you need to remove the "normal" difference between September and January (and maybe a few smaller effects like the shift in the months of up to 18 hours due to leap years). The outcome of this is a number called the "temperature anomaly" which described how much hotter that month was than the same month in the average of a set of baseline years.
The booster isn't strong enough. Much of it is about as thick, and as strong, as a coke can (but much bigger). There are just enough structural ribs and the like to support the load during launch (and after landing) but if you grab it in the wrong place it will just break. The mass is mostly at the bottom (engines) so I gather it's quite stable once it's sitting on its feet and they weld covers over the feet to hold it in place for the voyage home.
The article seems to discuss a number of different ideas for a Lunar South Pole telescope with different purposes and limitations.
The liquid mirror idea seems to come from http://science.nasa.gov/scienc.... They talk about a non-metallic liquid with a very thin layer of silver leaf (actually solid, but so thin and flexible that it follows the curve of the liquid) as the mirror.
Since it's at the pole and pointing straight up, tracking isn't really a concern. You can rotate the camera once per month, either phyically or electronically to keep the image steady. It can only basically do one job, which is to take ultra-deep field photographs of areas of the sky close to the pole and spectra of objects in that field, but that would be enough to do a lot of interesting science.
It's a fairly easy calculation. A 30m diffraction-limited telescope working in violet light (300nm) has an angular resolution of about 300nm/30m (radians) which is about 10^-8 radians. At the distance of the moon (4 x 10^8 m) that is about 4m, So theoretically the Apollo descent stage might be about 1 pixel across. In reality, I don't think adaptive optics yet allows diffraction limited imaging at such short wavelengths, so I would expect the best achievable resolution to be more like 10m.
The biggest advantage of the Moon is that you can fasten your telescope down and use the mass of the Moon to absorb heat and vibration. In space you need to deal with them. There are also designs for small-scale processing units that will make "mooncrete" from lunar dust (and a small percentage of additives) or extract aluminium, which might be useful for the structure. There are crater bottoms at the South pole of the moon which are in permanent darkness with nearby mountain peaks in permanent light (for power collection).
You also have the prospect of astronauts visiting if you need repairs/upgrades your robot can;t do.
Earth-sun L2 (where Gaia) is, is the other serious contender -- a very stable environment, but out of reach for humans and requiring a little fuel for station-keeping.
The ariticle I read about these in also mentioned the top of the Dome A in antarctica as a serious contender -- very still dry cold air all winter, compacted snow as a building material and relatively cheap and hospitable for humans.
There is no suggestion or prospect of doing long baseline optical interferometry with any of these telescopes, mainly because no one knows how to do it. Optical interferomteres cover at most 100m or so.
The reason for wanting one of these telescopes in the Northern hemisphere is simply so it can see the Northern sky.
Reprocessing fission waste has proved expensive, difficulyt and prone to accidents and leaks everywhere that it's been tried. It's not impossible, but you end up dealing with a mixture of hot radioactive nitric acid and insoluble radioactive sludge of unknown composition, using only remote handling. The plants all had a lot of down-time, stuck valves, corrosion problems,....
The comment is a about the general frequency of water. For Earth if you want a lot of water, Ceres or a well-chosen comet seem like the best choices at the moment, with the craters at the South pole of the Moon a bit of a long-shot. If you just need a few tons you may as well send it up from Earth. Finding water in the outer system is not a surprise, but finding so much on Mars and Ceres was a bit unexpected.
Nope, CH4 freezes solid at 90,7K (versus LOX boiling at 90,2K). And it becomes way too viscous as it approaches its freezing point. That doesn't mean that they can't share a common bulkhead, but it does complicate it for long-term storage (aka, Mars missions)
Fair point, but it does simplify things more than LH2+LOX would be, or even RP1+LOX if you found a way to synthesize kerosene on Mars.
Those boiling points are presumably at 1 atmosphere, but there is nothing special about that pressure. If you pressurise the LOX tank a little you can probably get them both liquid in the thermal contact at 95-100K.
The higher density, lower compressibility and higher latent heat of vapourisation of methane all make it easier to pump than LH2, saving mass and complexity.
Current blades are trucked in one piece (per blade) which is impressive to see. Three of them were parked on I-5 outside of Patterson, California a few months ago. There are a lot of net videos and photos which convey the scale.
Even at the current size they can't get through many highway interchanges and local intersections. The larger ones won't be able to ship in one piece at all.
"ship" is the point. These are designs of offshore turbines. They would probably make the blades in shipyards and transport them on a barge directly to the site.
Mega installation which require mega capital which allow power companies to centralize production, control distribution, and charge consumers.
It is more efficient and less prone to failure to have distributed production with small scale wind turbines, photovoltaic, etc. on peoples' homes. But then, well, where's the profit to the established interests?
It's not more efficient. It may be more desirable for several reasons, but with wind turbines for efficiency (power produced per dollar spent) you want the big and high up. This especially applies if you are building them offshore as is proposed in this case, because buildign the base and getting there to do maintenance are high costs that depend on the number of turbines, not the power produced.
It's also not less prone to failure, at least for some definitions of failure, in that the wind is much steadier out at sea an a few hundred meters up. A professional maintenance and inspection regime also helps.
Their calibration involved a reference point for one of the lasers that had to be precisely positioned. This was done by having a rigid metal bar with a polished end, covered by a very black cap with a pinhole in it. The point on the end of the bar visible through the pinhole was meant to be the reference.
Unfortunately someone scratched the end of the cap a little and no one noticed. The shiny metal in one of the scratches got picked up as the reference instead of the pinhole. As a result it was too close to the mirror by the thickness of the cap (a millimeter or so). That was enough to lead them to carefully polish the mirror to slightly the wrong shape.
They did, I believe, ignore contradictory results from another basically much less accurate method of testing the mirror, since the laser was giving consistent results and was the superior method.
Falcon 9 is actually just a two stage rocket, so the second stage ends up in orbit. Recovering it would mean using fuel to deorbit and having a heat shield capable of withstanding reentry. Even just recovering the engine would be a pretty major operation.
If you wanted to avoid wasting this element then lifting it a little higher into a stable orbit (perhaps via an ion drive tug) and then making use of it for something there would make more sense.
Slashdot Mirror
Do you have links? I'd be interested in knowing more about the Westinghouse designs in particular.
With nukes those fuel rods are decaying over time no matter what you do so that's another reason to have them run flat out until it's time to shut down for maintainance or refuelling.
Technically, yes they decay, but no it doesn't actually have a significant effect. U235 (the fissile fuel in enriched uranium) has a half life of 700 million years, so even if you waited that long, you'd still have half the fuel left. MOX uses a mix of U235, Pu239, and U233. The shortest (Pu239) has a half life of 24,000 years, so even if you left it standing for 100 years, you'd still have 99.7% of the plutonium left. The other sort-of fuel is U238, which absorbs a neutron turning into Pu239 which is a fuel during the reactor operation. U238 has a half life of 4.5 billion years.
In other words, you can leave the fuel sitting around for human timescales without a problem or significant loss.
Unused fuel rods don't decay much, it's true, but once you start using them, they fill up with short-lived fission products which will decay and produce heat at a high level over days and weeks, even if you quench the fission reaction entirely. You have to remove that heat (which is why some form of cooling is needed in nuke plants for weeks after they shut down to stop the fuel melting or burning) and so it is economically very desirable to use it to generate power and to use that power.
So using a fission reactor to respond to day or week long variations in demand is horribly inefficient and expensive. Gas plant is much easier to start up and shut down, as in wind, while solar (PV to be specific) generates power when it does, but uses no fuel (except hydrogen in the core of the sun, which is not in shortage) so you can just dump the power.
The answer, of course, is yes and no.
If people thought sea level was rising and it isn't they will admit to being wrong about that.
To convince people that the whole picture of AGW is wrong in broad terms, would need a much wider-ranging set of inconsistent data, and preferably an equally consistent model that fitted all the observations better and either fitted, or revised, known physics, in a sensible way.
Just looked. There are small differences. I see about .1 degree at each end difference between the 5-year means in the two graphs, well within the error bars. If you have the underlying numbers we could look at the statistical signiificance of this
However, what you need to understand is that there is not a single thermometer somewhere that measures the global temperature. There are thousands, and the same ones have not been used consistently in different ways across 100+ years. They are moved, replaced, read at different times, etc,. etc.
So the data in either of those graphs is the result of a lot of difficult and careful analysis (which is published and peer-reviewed). From time to time improvements in theory, more computing power and new data (for instance about the behaviour of the instruments) lead to improvedments in the techniques of that analysis. Since everyone has been pretty cautious, trying NOT to be alarmist, these improvements usually make the picture more alarming, as some of the caution proves to have been unnecessary.
So no smoking gun just science at work. All the information you need to follow the process in detail is in the public domain, although you need to be prepared to read a few tens of thousands of pages of hard maths to make sense of it.
I should say by the way that sometimes people do make mistakes. They range from the trivial (typing 2035 instead of 2350) to serious, but they are picked up and corrected pretty quickly by other scientists.
We can deduce (from the properties of the cosmic microwave background) the ratio of photon-interacting mass with gravitational mass in the very early universe.
We can also deduce (from the relative proportions of light isotopes in the universe) the absolute density of baryons.
These two match up near enough.
So we know there are baryons we haven't spotted yet, and we know that there isn't much apart from baryons around that interacts with photons.
Whatever standard you adopt needs to be reproducable within the limits of the best current measurements by any other technique. Otherwise when people want a stable reproducible result they will use the other technique and the standard won't have worked. Measuring volume of water, purity, temperature and pressure is just not precisely reproducible enough
e and pi are numbers. You need actual physical constants like the mass of a proton or Planck's cpnstant.
It is indeed just a matter of choosing "close enough factor", but close enough (to avoiding needing to redo or change any measurements that anyone uses) is pretty close, about one part in 100 billion. Being sure that we have done that is the hard part.
Instead of putting just one camera (which would definitely NOT gather enough light at this size), they're massively parallelized it. They've put millions of pinholes camera on the chip and are using post processing to reconstruct the final image out of the tons of tiny pinhole views.
I think there are more pinholes of a variety of different shapes, and fewer sensor pixels than your description might suggest.
Anomaly is a technical term. If you want to compare how exceptionally warm January 2016 was with how exceptionally warm September 2015 was you need to remove the "normal" difference between September and January (and maybe a few smaller effects like the shift in the months of up to 18 hours due to leap years).
The outcome of this is a number called the "temperature anomaly" which described how much hotter that month was than the same month in the average of a set of baseline years.
On that timescale, there are plenty of ways of controlling that, perhaps most simply moving the Earth,
Read different tech sites, or just browse the amazon catalogue. Some people are interested in new ideas.
Just don't the top 0.1mm of the glass. You lose a few TB of capacity, but now the data is below any scratches.
The booster isn't strong enough. Much of it is about as thick, and as strong, as a coke can (but much bigger). There are just enough structural ribs and the like to support the load during launch (and after landing) but if you grab it in the wrong place it will just break. The mass is mostly at the bottom (engines) so I gather it's quite stable once it's sitting on its feet and they weld covers over the feet to hold it in place for the voyage home.
The article seems to discuss a number of different ideas for a Lunar South Pole telescope with different purposes and limitations.
The liquid mirror idea seems to come from http://science.nasa.gov/scienc.... They talk about a non-metallic liquid with a very thin layer of silver leaf (actually solid, but so thin and flexible that it follows the curve of the liquid) as the mirror.
Since it's at the pole and pointing straight up, tracking isn't really a concern. You can rotate the camera once per month, either phyically or electronically to keep the image steady. It can only basically do one job, which is to take ultra-deep field photographs of areas of the sky close to the pole and spectra of objects in that field, but that would be enough to do a lot of interesting science.
It's a fairly easy calculation. A 30m diffraction-limited telescope working in violet light (300nm) has an angular resolution of about 300nm/30m (radians) which is about 10^-8 radians. At the distance of the moon (4 x 10^8 m) that is about 4m, So theoretically the Apollo descent stage might be about 1 pixel across. In reality, I don't think adaptive optics yet allows diffraction limited imaging at such short wavelengths, so I would expect the best achievable resolution to be more like 10m.
This article explores the pros and cons of the three sites (Antarcita, Moon and L2) in some depth
http://citeseerx.ist.psu.edu/v...
The biggest advantage of the Moon is that you can fasten your telescope down and use the mass of the Moon to absorb heat and vibration. In space you need to deal with them. There are also designs for small-scale processing units that will make "mooncrete" from lunar dust (and a small percentage of additives) or extract aluminium, which might be useful for the structure. There are crater bottoms at the South pole of the moon which are in permanent darkness with nearby mountain peaks in permanent light (for power collection).
You also have the prospect of astronauts visiting if you need repairs/upgrades your robot can;t do.
Earth-sun L2 (where Gaia) is, is the other serious contender -- a very stable environment, but out of reach for humans and requiring a little fuel for station-keeping.
The ariticle I read about these in also mentioned the top of the Dome A in antarctica as a serious contender -- very still dry cold air all winter, compacted snow as a building material and relatively cheap and hospitable for humans.
There is no suggestion or prospect of doing long baseline optical interferometry with any of these telescopes, mainly because no one knows how to do it. Optical interferomteres cover at most 100m or so.
The reason for wanting one of these telescopes in the Northern hemisphere is simply so it can see the Northern sky.
Reprocessing fission waste has proved expensive, difficulyt and prone to accidents and leaks everywhere that it's been tried. It's not impossible, but you end up ....
dealing with a mixture of hot radioactive nitric acid and insoluble radioactive sludge of unknown composition, using only remote handling. The plants all had a lot of down-time, stuck valves, corrosion problems,
The comment is a about the general frequency of water. For Earth if you want a lot of water, Ceres or a well-chosen comet seem like the best choices at the moment, with the craters at the South pole of the Moon a bit of a long-shot. If you just need a few tons you may as well send it up from Earth. Finding water in the outer system is not a surprise, but finding so much on Mars and Ceres was a bit unexpected.
Nope, CH4 freezes solid at 90,7K (versus LOX boiling at 90,2K). And it becomes way too viscous as it approaches its freezing point. That doesn't mean that they can't share a common bulkhead, but it does complicate it for long-term storage (aka, Mars missions)
Fair point, but it does simplify things more than LH2+LOX would be, or even RP1+LOX if you found a way to synthesize kerosene on Mars.
Those boiling points are presumably at 1 atmosphere, but there is nothing special about that pressure. If you pressurise the LOX tank a little you can probably get them both liquid in the thermal contact at 95-100K.
The higher density, lower compressibility and higher latent heat of vapourisation of methane all make it easier to pump than LH2, saving mass and complexity.
Current blades are trucked in one piece (per blade) which is impressive to see. Three of them were parked on I-5 outside of Patterson, California a few months ago. There are a lot of net videos and photos which convey the scale.
Even at the current size they can't get through many highway interchanges and local intersections. The larger ones won't be able to ship in one piece at all.
"ship" is the point. These are designs of offshore turbines. They would probably make the blades in shipyards and transport them on a barge directly to the site.
Mega installation which require mega capital which allow power companies to centralize production, control distribution, and charge consumers.
It is more efficient and less prone to failure to have distributed production with small scale wind turbines, photovoltaic, etc. on peoples' homes. But then, well, where's the profit to the established interests?
It's not more efficient. It may be more desirable for several reasons, but with wind turbines for efficiency (power produced per dollar spent) you want the big and high up. This especially applies if you are building them offshore as is proposed in this case, because buildign the base and getting there to do maintenance are high costs that depend on the number of turbines, not the power produced.
It's also not less prone to failure, at least for some definitions of failure, in that the wind is much steadier out at sea an a few hundred meters up. A professional maintenance and inspection regime also helps.
Their calibration involved a reference point for one of the lasers that had to be precisely positioned. This was done by having a rigid metal bar with a polished end, covered by a very black cap with a pinhole in it. The point on the end of the bar visible through the pinhole was meant to be the reference.
Unfortunately someone scratched the end of the cap a little and no one noticed. The shiny metal in one of the scratches got picked up as the reference instead of the pinhole. As a result it was too close to the mirror by the thickness of the cap (a millimeter or so). That was enough to lead them to carefully polish the mirror to slightly the wrong shape.
They did, I believe, ignore contradictory results from another basically much less accurate method of testing the mirror, since the laser was giving consistent results and was the superior method.
Falcon 9 is actually just a two stage rocket, so the second stage ends up in orbit. Recovering it would mean using fuel to deorbit and having a heat shield capable of withstanding reentry. Even just recovering the engine would be a pretty major operation.
If you wanted to avoid wasting this element then lifting it a little higher into a stable orbit (perhaps via an ion drive tug) and then making use of it for something there would make more sense.