SCIENCE AND EDUCATION
Prasen Vinchurkar
Voyager spacecraft head for interstellar space
19:45 May 19, 2011
Artist concept of NASA's Voyager spacecraft (Image: NASA/JPL-Caltech)
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The last time we checked on the Voyager 1 & 2 they were hurtling towards the edge of the solar system at over 37,000 mph (60,000 km/h). The car-sized spacecraft are now and incredible 11 billion miles (17 billion km) and 8 billion miles (14 billion km) from Earth respectively - they are the longest continuously operated spacecraft in deep space and having traveled further than any man-made object, they will soon become the first to enter the realm of interstellar space. NASA recently held a briefing on the achievements of the program which gives us the opportunity to ponder where the Voyagers are, where they are going and the amazing scientific discoveries realized so far in their 33 year journey.
Built by NASA's Jet Propulsion Laboratory in Pasadena, California, Voyager 2 was launched on Aug 20, 1977, closely followed by Voyager 1 on Sept 5. It was a special year because there was a rare planetary alignment of the outer planets, which meant the spacecraft would be able to visit all four giant gas planets; Jupiter, Saturn, Uranus and Neptune.
Flybys of Jupiter, Saturn, Uranus and Neptune
The Voyager twins' primary five year mission was to explore Jupiter (which was reached in 1979) and Saturn (1980). The spacecraft captured images of the planets, their larger moons and Saturn's rings making some amazing discoveries. The mystery of Jupiter's Red Spot was found to be a massive hurricane three times the diameter of Earth and just one of many huge storms on the planet. Saturn's rings were revealed to be made of a mish mash of icy particles- some as large as a house. Io, one of Jupiter's moons, was observed to have eight active volcanoes, where previously Earth was the only known world to experience volcanic eruptions.
Voyager 2, propelled further by Jupiter and Saturn's gravity, continued to Uranus in 1986 and Neptune in 1989. Breathtakingly close up pictures were taken of the planets, their moons and the system of rings and magnetic fields those planets possess. Notable discoveries included the fact that Uranus has its north pole tipped on its side facing the sun and spins vertically. Neptune the most remote giant planet has the fastest winds in the solar system that travel at over 1,200 mph (2,000 kph). Like Jupiter, it has a Great Dark Spot of its own, a giant storm about the size of Earth. Triton, a moon of Neptune is the coldest measured object in the Solar System. It has a surface temperature of -390°F (-235°C) with geysers spewing nitrogen gas into the atmosphere.
The Voyager spacecraft rewrote the textbooks on the four gas giants revealing the complexity and diversity of our solar system. On its way out of our solar system, Voyager 1 was asked to look back and take more photograph before the cameras were turned off. The "Pale Blue Dot" photograph was taken from a record distance of more than four billion miles from Earth and is part of the resulting is 60 frame mosaic of the solar system. In the photo, the Earth appears as a tiny dot 0.12 pixels in size, giving us a mind-boggling reminder of just how small we are in the vastness of space.
Still making discoveries and performing tricks
Voyager 1 will soon be the first probe to go outside our solar system. Using the gravitational force of Saturn and Jupiter, it swung North of the planetary plane and onwards to interstellar space. It is now over 117 times further from the Sun than we are and at this distance, the Sun is very dim - 1/10,000 as bright as it is here on Earth.
Voyager 2 is traveling at a slower speed, it is approximately 3 billion kilometers closer to us than Voyager 1 and heading south of the planetary plane.
The spacecraft is an incredible workhorse performing new tricks and old ones after long periods of time have passed. Voyager 1 was recently asked to perform a scan using its low energy charge particle instrument. This required a maneuver not performed since the Pale Blue Dot photograph was taken in 1990. The spacecraft was asked to rotate 70 degrees to scan data in three dimensions, hold for three to five hours and then swing back around to celestial lock.
Voyager 1 is currently in a type of "deadzone" called the heliosheath, a region where the solar wind is made turbulent by its interaction with the interstellar medium. The purpose of this scan, which will be repeated every three months, is to use the spacecraft's low energy charge particle instrument to determine when it passes beyond the very edge of our Sun's influence. Scientists believe that there are only a few more years of travel left before Voyager breaks free and can truly be called a traveler amongst the stars.
The signals traveling at the speed of light now take 13 hours one way to reach Earth from Voyager 2, and 16 hours one way from Voyager 1. To help put the distance into perspective; typical signals from Mars missions take 10 minutes one way. The signals are now so feint that they require the largest antennas on Earth to track them.
Equipment onboard Voyager
The Voyager spacecraft are identical. The size and weight of a small car, they are made up of a 10 sided main structure called the bus, a high-gain antenna, three booms that hold scientific instruments, the power supply and two other antennae. The main antenna is 12 feet (3.7 meters) across and looks like a satellite dish. This antenna is how the Voyagers receive commands from Earth and send data they gather back. No matter where a Voyager spacecraft is in space, the high gain antenna always points towards the Earth.
The spacecraft are powered by a radioisotope thermoelectric generator, in essence a nuclear battery. Pellets of plutonium release heat through natural decay and are converted into electricity using a series of thermocouples. It is a safe, reliable and long lasting power source expected to be finally depleted somewhere around 2025. Voyager's thrusters are fueled by hydrazine and there is enough on board to last another 60 years as fuel is only used to reorient the spacecraft. It uses about 1.6 grams per day.
Voyager carries various scientific instruments along with three computers that share just 68 KB of memory. Engineers developed a self repairing, programmable command processor with multiple modules that are able to determine errors by comparing past data.
The "Sounds of Earth"
The spacecraft are famous for carrying identical golden phonograph recordings titled the "Sounds of Earth." The records contain a cultural time capsule, images, natural sounds, spoken greetings in over 50 languages and musical selections from different cultures and eras. The records are 12 inches (30cm) across and made from gold plated copper. They contain sounds and images selected to illustrate the diversity of life and culture on Earth and it is hoped that one day they may communicate a story of our world to extraterrestrials. A gold plated aluminum cover was designed to protect the records from micrometeorite bombardment which also has etched into it scientific hieroglyphics. The cover shows an explanatory diagram on how to play the recordings. It displays our cosmic address illustrating the 16 closest pulsars and also an atomic clock that explains Voyager's launch date. The diagram appears on both the inner and outer surfaces of the cover as the outer diagram will be eroded in time.
The records should not to be confused with the simpler metal plaques on Pioneers 10 and 11 which were launched in 1972. The plaques were designed to show scientifically minded extraterrestrials when Pioneer was launched, from where and by whom. They present amongst other things, a male raising his right hand in a gesture of goodwill.
A "Noah's Ark of human culture"
The golden records were a much more ambitious message than the Pioneer plaques, created as a "Noah's Ark of human culture". Over 100 pictures illustrating Earth were collated, each like a tile in a large mosaic of life on Earth. The designers wanted to make sure the drawings and images had a planetary perspective so they present the Earth, our solar system, people doing mundane activities such as eating and drinking as well as showing our anatomy and DNA structures. Plants and animals are included along with scenes from around the world such as a Thai craftsman, a Turkish old man, a gymnast and a schoolroom. Various landmarks, the Golden Gate Bridge, the Sydney Opera House, the Great Wall of China, the Taj Mahal and UN buildings are also documented.
Over 90 minutes worth of sounds are included ranging from natural sounds like storms and volcanoes to human made sounds like a mother kissing her child and airplane and rocket takeoffs. Greetings in over 50 different languages, from Arabic to Zambian, and 27 pieces of music including Beethoven, Bach, Mozart, world music from China, Japan, India and Peru, and a rock n roll track, "Johnny B Good" by Chuck Berry (no Rolling Stones as falsely shown by the Hollywood movie Starman).
The future of Voyager
Once outside the heliosphere, Voyager 1 will take measurements of the vast clouds that envelope our solar system. These clouds are remnants of stars that exploded five to ten million years ago. NASA hopes to operate Voyager until 2025 when it will then be left to wander throughout the galaxy for another 1000 million years.
The spacecraft are still functioning and thriving after more than 30 years. Robust, durable and built from 1970s components, the transistors are still functioning brilliantly today. They have exceeded their design specifications and the loftiest dreams of their makers. They have already made an amazing contribution to our civilization and many great discoveries are still to come.
Voyager 1 is on a trajectory to reach star AC+79 in about 40000 years. Voyager 2 has is on its way to the vicinity of star Sirius, a mere 296,000 years away.
You can keep up to date with how far the Voyagers are from home with NASA's real-time odometer.
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Prasen Vinchurkar
Nanoscience & Nanotechnology
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Prasen Vinchurkar
By Ben Coxworth
15:52 May 25, 2011
Scientists have created a thin handheld microscope that can obtain high-quality images in a fraction of the time required by traditional scanning microscopes (Photo: Fraunhofer)
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With conventional microscopy, if a scientist wishes to obtain a high-resolution image of a relatively broad area, they typically have to use a microscope that scans across that area in a grid pattern, recording many images one point at a time. Those images are then joined together to form one complete picture. Such systems take a long time to perform a scan, so both the microscope and the subject must be held still while it's taking place. Researchers from Germany's Fraunhofer Institute for Applied Optics and Precision Engineering, however, have created a thin, handheld microscope that can reportedly obtain similar-quality images in less than one second.
Unlike a scanning microscope, that records many single images one after the other, the Fraunhofer microscope uses an array of tiny lenses to record a comparable number of images all at once. As with the scanning microscope, these are subsequently combined to form one complete image.
The new microscope's imaging system consists of three glass plates, stacked one on top of the the other like pancakes. Each plate is covered with a matrix of the tiny lenses, both on its top and bottom surfaces. Looking down through the plates from above, each tiny lens lines up both with its counterpart on the other side of its plate, and with the other lenses that occupy the same location on the other plates. Microscopic details are therefore imaged through a stack of six tiny lenses, along with two achromatic lenses. These stacks of lenses are called channels, and it is the images produced by the multiple channels that are digitally joined together, side-to-side and top-to-bottom, to create the complete picture.
Because it has an optical length of just 5.3 millimeters, the microscope is able to maintain a very flat profile.
To make the lenses, the scientists start by coating a glass plate with photoresistant emulsion, covering it with a mask in the pattern of the lens matrix, then exposing it to UV light. Emulsion exposed to the light hardens, while the emulsion protected by the mask washes away when exposed to a special solution. This leaves a matrix of tiny cylinders, which are then heated. This causes them to partially melt, and form into spherical lenses. The lens-covered plate is then used to create a die, which in turn can be used for mass production - glass substrates are coated with a clear liquid polymer, the lens die is pressed down into that, the polymer takes on the shape of the lens array, and is then hardened using UV light.
The microscope is currently still in the prototype stage, and probably won't go into production for at least one or two years. Once it does, it could be used to examine suspicious skin blemishes, check documents for authenticity, or various other applications. It is currently capable of imaging of objects the size of a matchbox, in one pass.
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Prasen Vinchurkar
Thorium: A safer alternative for nuclear power generation?
20:26 May 26, 2011
Thorium could provide a cleaner and more abundant alternative to uranium (Photo: Three Mile Island Nuclear Power Plant/ Lyndi & Jason via Flickr)
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The world's growing need for energy, the limits of our supply of fossil fuels and concern about the effects of carbon emissions on the environment have all prompted interest in the increased use of nuclear power. Yet the very word "nuclear" carries with it an association of fear. People are concerned about the waste produced by reactors, the possibility of catastrophic accidents as highlighted by recent events in Japan and the link between nuclear power and nuclear weapons. Yet what if there existed a means of nuclear power generation with which these risks were drastically reduced?
The answer could be thorium - an element occurring as a silvery metal that's more abundant, cleaner and can produce more bang-per-buck in energy terms than uranium. So how does thorium differ from uranium and plutonium, and why isn't it being used? First, a quick run-down on how nuclear energy works.
What is nuclear power?
The word "nuclear" refers to the nucleus, or dense center of the atom. In a nuclear power reactor, these nuclei are split into smaller parts through a process known as fission. A sub-atomic particle known as a neutron strikes the nucleus of an atom of suitable fuel (particular isotopes of the heavy elements uranium and plutonium) breaking it into its component parts. Each fission results in the release of energy in the form of electromagnetic radiation and kinetic energy in the fragments of the split nucleus. This effect is twofold; the release of energy will produce heat, and the release of neutrons, which can in turn fission other atoms.
In material that has typically been employed as nuclear fuel, this reaction occurs in a "chain reaction" and is self-sustaining. When this is occurring, the reactor can be said to be"'critical". In a fission weapon, a mass of plutonium or uranium in excess of critical is assembled very quickly, with a flood of neutrons from a device known as an "initiator". The release of energy is extremely rapid and results in a massive explosion.
In a nuclear power reactor, the reaction is far slower and more controlled - the heat produced can be harnessed to boil water to spin turbines for the generation of electricity and this has been in practice for decades. The use of nuclear reactors for power generation began on 27 June 1954 at the Obninsk power plant in the former Soviet Union and has continued in numerous countries to this day.
There are of course, some significant problems with nuclear power. Fission reactions will always result in the production of radioactive waste products which require secure storage and pose a health risk to humans and the environment. There is the possibility that the operators may lose control of the fission chain reaction resulting in an accidental release of this material (often referred to as a "meltdown"). There's also the concern that reactors may also be used for the production of material suitable for nuclear weapons.
Modern nuclear reactors
The two main types of reactors used for commercial power generation are the pressurized water reactor (PBR) and the boiling water reactor (BWR), which both typically make use of uranium in the form of uranium oxide fuel rods. The criticality of the reactor is managed by control rods, which when inserted absorb neutrons that would otherwise cause the chain reaction to continue. The reactor can be shut down, or "scrammed", by the rapid insertion of these control rods. However, this is a manual process and there is a possibility of an error occurring.
Criticality, fertility and the potential of thorium
The element thorium, named after the Norse god of thunder, may provide a safer alternative as a fuel. The key difference between thorium and other nuclear fuels is that it cannot sustain a chain reaction on its own. Fissile fuels like uranium and plutonium are able to sustain a chain-reaction, yet fission can also be achieved in material like thorium that is not fissile but fertile - i.e. it can produce fissile material, if neutrons are provided from an outside source.
Thorium is estimated to be three to four times more plentiful than uranium in the Earth's crust and has the advantage of being found in nature in the one isotope, which makes it suitable as a nuclear fuel as it need not be enriched to separate the right isotope. For convenience, thorium fuel can be used in the form of a liquid molten salt mixture.
Accelerator Driven System
Fission occurs in thorium when atoms absorb a neutron to become a heavier isotope and quickly decay into an isotope of the element protactinium and then an isotope of uranium, which is fissioned when struck by an additional neutron. The number of neutrons produced is not sufficient for a self-sustained chain reaction.
A particle accelerator could be used to provide the necessary neutrons for fission to occur in thorium and a nuclear reactor making use of such an outside neutron source would be known as an 'accelerator driven system' (ADS).
The notion of the ADS is credited to Carlo Rubbia of the European Organisation for Nuclear Research (CERN) joint winner of the 1984 Nobel Prize for Physics. The ADS would likely be far smaller than other reactors and if the accelerator were to be turned off, the nuclear reaction would cease, although it should be noted that even in a reactor which is not critical, the heat from the decay of materials can be significant and cooling is required.
In a thorium reactor, quantities of other fuels could be included, without the fuel being capable of sustaining a chain reaction, and thus the reactor could be used to provide energy from disposing of material such as plutonium from disassembled nuclear weapons. It's also possible to ensure that the reactors are designed in such a way that it is not possible to extract fissile material, which can be used to manufacture nuclear weapons.
Though all nuclear reactors will produce waste products, a reactor fulled by thorium will produce far less long-lived waste products than one fueled by uranium or plutonium, with waste decaying to the same level of radioactivity as coal ashes after 500 years.
Thorium also produces more energy from the same amount of material compared to uranium.
"Two hundred tonnes of uranium can give you the same amount of energy you can get from one tonne of thorium," Rubbia told the BBC News in a recent interview.
Towards a thorium reactor
Though several reactors have made use of thorium for experimental purposes, a thorium power reactor is not as yet a reality. Countries like Russia, India and China are looking at the use of thorium and such a reactor may one day soon be a viable energy source.
So why has it taken so long for thorium to hit the nuclear power agenda? The key reason seems to be that because it can't be used to make a nuclear bomb, it was largely ignored during the Manhattan project and in the development of nuclear power stations that followed.
Google sponsored some lectures on LIFTR (LIquid Fluoride Thorium Reactor) technology a few years back. You can find them on YouTube if you do a search. Some very good (and technical) information there. Almost all upside. Almost no downside. (Nothing is perfect) Significantly greener than oil, gas or the current state of nuclear. If you take into account the massive amount of pollution created by the production of photo-voltaic it's even greener than that and doesn't consume thousands of acres of delicate desert land. Have a look.
dwreid
- May 26, 2011 @ 09:55 pm PDT
This ain't new, the idea has been around for some time... but it's time someone build one using Thorium rather than Uranium...
Windmaster Hiroaki
- May 26, 2011 @ 11:24 pm PDT
What's the environmental impact of the mining process like compared to uranium? And where are the main deposits of the stuff located, internationally speaking? (as in, what countries would stand to gain/lose from a Thorium reactor revolution mining wise).
Earl Leonard
- May 27, 2011 @ 01:15 am PDT
A nuke dummy I almost fell for the hook. The grid is the issue. Individual power no grid no stock holders, no officers to drive the cost of energy up so the sale of planes, boats and fast cars can continue unabated.
The Grid comes down, get ready with individual power sources, Red Dawn is the model, and the Grid makes us vulnerable to Canadians looking for a beach.
The fossil fuel revolution comes to an end before we all suffocate. Nuke ends before we cook ourselves to death, Fukushima is a four letter for GE.
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Patrick McGean
- May 27, 2011 @ 07:37 am PDT
Get a grip guys. This is just old hogwash: In 2008 a report from the Norwegian Radiation Protection Authority (NRPA) revealed that thorium-based nuclear energy plants - once vaunted as a clean alternative type of nuclear energy - have the same negative environmental consequences as their uranium-based cousins do. The NRPA report dealt with the environmental consequences of potential thorium related industry in Norway. The report takes on various aspects of the thorium fuel cycle from mining and extraction, fuel production, reactor operation and waste handling. The report concludes that the environmental consequences of using thorium-based nuclear power will result in the same problems the world faces today with uranium bases reactors. "The NRPA invalidated that thorium is kind nuclear power, as many have earlier asserted," said Nils Bohmer, nuclear physicist with Bellona, a Norwegian based environmental organization. "Using thorium leads to highly radioactive nuclear waste and the risk of accidents will always be present." According to the NRPA, thorium-based nuclear energy, uncontrolled chain reactions and, in the worst case, meltdowns can occur. The NRPA also asserts that thorium-based nuclear energy will produce long-lasting radioactive waste that will demand the same handling as highly radioactive waste from current nuclear reactors. The NRPA report also points out that it is impossible to give a full value oversight of all potential environenmental consequences of thorium-based nuclear energy. The report shows that each form of thorium extraction, whether by open-pit mining or underground mining, will lead to negative burdens on the environment. Extraction will produce radioactive waste in the form of slag heaps that can lead to an escalation of radiation for humans and the environment, and the spread of radioactivity. Earlier, many had asserted that thorium technology cannot be used for weapons purposes. Even though this would be more difficult than with current technology, the NRPA report shows that this will continue to be possible. In the 1950s, the United States accomplished its first test explosion with uranium 233, which is the material thorium-based energy production produces. Additionally, highly enriched or plutonium is required as an additive to thorium to produce a chain reaction. These are materials that can be abused for weapons grade purposes.
Dawg
- May 27, 2011 @ 07:47 am PDT
Go,Thor!
HAMMER DOWN!
{^,^}
Griffin
- May 27, 2011 @ 07:53 am PDT
Thorium is highly abundant and easily attainable. It runs on a low pressure system, so much safer than present day high pressure Nuclear reactors. It's also nearly 100% efficient. Here are some figures from Kirk Sorenson's Google presentation:
6600 tonnes of thorium (500 quads) is equal to one of the following in the list below:
- 5.3 billion tonnes of coal (128 quads)
- 31.1 billion barrels of oil (180 quads)
- 2.92 trillion m3 of natural gas (105 quads)
- 65,000 tonnes of uranium ore (24 quads)
more figures.
6 kg of thorium metal in a liquid-fluoride reactor has the energy equivalent (66,000 MW*hr electrical*) of:
- 230 train cars (25,000 MT) of bituminous coal or,
- 600 train cars (66,000 MT) of brown coal or,
- 440 million cubic feet of natural gas (15% of a 125,000 cubic meter LNG tanker),
- or, 300 kg of enriched (3%) uranium in a pressurized water reactor.
Kirk Sorenson is an expert on the matter, check his site for how things are developing: http://energyfromthorium.com/about/
Fabrizio Pilato
- May 27, 2011 @ 08:32 am PDT
Um the grid does need a serious upgrade. but the grid is good silly rabbit. If you live on a farm and don't have a family sure you can have some wind mills, most people live in burbs or cities.. What then? No one wants solar panels even with subsidies they are 30-40 cents per kwh, and then you have to charge something to get through the night.. then it gets to a $1 per kwh. No thanks I think we will keep the grid and just build more nuclear plants.
Michael Mantion
- May 27, 2011 @ 08:59 am PDT
Thorium is very abundant. but then again so is uranium, especially all the spent fuel that could be reprocessed.
Michael Mantion
- May 27, 2011 @ 09:01 am PDT
One of the promising things about Thorium reactors is that they can be built significantly smaller than current Uranium based reactors. It's possible that a town could purchase and install their own reactor rather than relying on grid power. There even is a proposal for a portable reactor designed for remote site power and heat generation.
http://nextbigfuture.com/2011/05/thorenco-llc-presents-little-40-mw.html
Eletruk
- May 27, 2011 @ 09:16 am PDT
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