Tuesday, November 4, 2008

Forcefields will guard Mars ships from solar ion storms

Boffins crack portable particle-squall brolly tech

A team of top boffins believe that they have cracked one of the main problems of interplanetary travel - that of surviving deadly solar radiation storms. The physicists say they have come up with an idea for a crafty forcefield which could stand off the protoplasm-punishing particle squalls of deep space.

An image of the storm-wracked solar atmosphere

There's plenty of weather on the sun.

Thus far, only a very few people have ever travelled beyond the protection of the Earth's magnetosphere - the Apollo astronauts who went to the Moon in the 1960s and 70s. All other humans in space - including the crews of the present-day International Space Station - have remained within the protective magnetic field of their home planet.

The Apollo missions were reasonably safe because they were brief - only days long. The risk of a major solar radiation storm was minimal. Even so, had there been a serious solar event during an Apollo mission the results might have been disastrous - the more so as there is no lunar atmosphere to protect explorers.

A journey to Mars, however, is projected to take 6 months - and then there's the return trip to consider. Even though the astronauts would be protected by the Martian atmosphere (and the planet itself) during their stay, a year in deep space would be very dangerous. Even normal background radiation could be expected to use up much of an astronaut's lifetime exposure limit.

A solar storm, more or less bound to occur over such a period, would breach the health guidelines and create an unacceptable risk of cancer. A bad particle squall could cause radiation sickness severe enough to incapacitate or even kill a Mars-ship crew on the spot.

But now boffins at the Rutherford Appleton Lab and the Universities of York, Strathclyde and Lisbon have shown that it's possible to generate a "portable magnetosphere" or magnetic forcefield just a few hundred metres across, which would prevent ionised particles reaching a space ship. It had previously been thought that only mighty planetary-scale fields could possibly be effective, but new computer simulations suggest that just a small "hole" in the solar winds could be enough.

“These initial experiments have shown promise," said Dr Ruth Bamford of the Rutherford Appleton lab, rather cautiously.

"It may be possible to shield astronauts from deadly space weather.”

Astronauts in a ship moving through space would find a nifty lightweight forcefield especially useful. Ordinary radiation shielding is extremely heavy, but everything in a spaceship must be as light as possible, every kilo of mass being precious. On the other hand the power required to generate a "magnetic bubble" could be an issue.

The new research would seem to have implications for NASA's plans to build a permanent Moon base, too. While lunar explorers would gain a good deal of protection from the Moon itself, blocking out half the sky, the lack of any atmosphere would see an explorer caught outside his thick-walled underground moon bunker by a solar storm during daylight in serious trouble. Moon rovers and inflatable habitats of the future might find magno-forcefield kit very handy.

Needless to say, reasonably portable forcefields would also be invaluable for the hover tanks, power-armour suits or interplanetary battlecruisers of tomorrow - ideal for resisting deadly particle-cannon blaster beams, krenon rays* etc.

The research is set out in a new paper: The Interactions of a flowing plasma with a dipole magnetic field: measurements and modelling of a diamagnetic cavity relevant to spacecraft protection (R Bamford et al 2008 Plasma Phys. Control. Fusion 50 124025). It's published online here. ®

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Magnetic shield for spacefarers


Lab tests show how to produce a protective 'hole' in the plasma

Future astronauts could benefit from a magnetic "umbrella" that deflects harmful space radiation around their crew capsule, scientists say.

The super-fast charged particles that stream away from the Sun pose a significant threat to any long-duration mission, such as to the Moon or Mars.

But the research team says a spaceship equipped with a magnetic field generator could protect its occupants.

Lab tests are reported in the journal Plasma Physics and Controlled Fusion.

The approach mimics the protective field that envelops the Earth, known as the magnetosphere.

Astronauts' risk

Our star is a constant source of charged particles, and storms that arise on the Sun's surface result in huge numbers of these particles spilling into space.

As well as this plasma, or "solar wind", high velocity particles known as cosmic rays also flood through our galaxy.

The Earth's magnetosphere deflects many of these particles that rain down on the planet, and our atmosphere absorbs most of the rest.

The first time we switched it on, it worked
Ruth Bamford

International space agencies acknowledge that astronauts face a significant risk of ill health and even death if they experience major exposure to this harsh environment.

And even the spacecraft themselves are not immune to the effects. A solar flare crippled the electronics on Japan's mission to Mars, Nozomi, in 2002, for example.

But researchers from the Rutherford Appleton Laboratory (RAL), the Universities of York and Strathclyde, and IST Lisbon have shown how it might be possible to create a portable mini-magnetosphere for spaceships.

People scale

In its experimental set-up, the team simulated the solar wind in the laboratory and used magnetic fields to isolate an area inside the plasma, deflecting particles around the "hole".

It was not initially clear the idea would work, said Ruth Bamford, who led the research.

"There was a belief that you couldn't make a little hole in the solar wind small enough to do this at all," Dr Bamford, from RAL, told BBC News.

"It was believed that you had to have something very large, approaching planetary scale, to work in this way."

The team has had to take into account the physics of plasmas at the comparatively tiny human scale. To create its metre-sized trial, the team used a plasma jet and a simple $20 magnet.

"The first time we switched it on, it worked," said Dr Bamford.

What is more, the trial field seems to adjust itself automatically. "It does have the capacity to be somewhat self-regulating, just like the Earth's magnetosphere is," Dr Bamford explained.

"When it gets a strong push from the solar wind, the bubble gets smaller. The video shows us increasing the pressure of the solar wind, and the shield gets smaller but brighter."

Power issues

Many more experiments are needed, Dr Bamford admits, to understand how best to harness the effect; and a practical implementation is probably 15 to 20 years away.

Magnetosphere graphic (Ruth Bamford)
The approach mimics how the Earth's magnetic field deflects particles

To protect a spaceship and its crew, she said, the craft itself might carry the magnetic field generator. Alternatively, it was possible to envisage a constellation of accompanying ships dedicated to the purpose of providing the umbrella where it was needed most.

The approach will probably also work with a field that is not on constantly, but cycles on and off - conserving the power that is precious on long-term missions. The details of how to cycle the field and control its shape must be hammered out, however.

"There're a lot of things to work out, like control, reliability, weight to launch, and so on," said Dr Bamford.

"I don't think it'll come down to as little as sticking fridge magnets on the outside of the spacecraft."

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Frozen mice cloned - are woolly mammoths next?

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - Japanese scientists have cloned mice whose bodies were frozen for as long 16 years and said on Monday it may be possible to use the technique to resurrect mammoths and other extinct species.

Mouse cloning expert Teruhiko Wakayama and colleagues at the Center for Developmental Biology, at Japan's RIKEN research institute in Yokohama, managed to clone the mice even though their cells had burst.

"Thus, nuclear transfer techniques could be used to 'resurrect' animals or maintain valuable genomic stocks from tissues frozen for prolonged periods without any cryopreservation," they wrote in the Proceedings of the National Academy of Sciences.

Wakayama's team used the classic nuclear transfer technique to make their mouse clones. This involves taking the nucleus out of an egg cell and replacing it with the nucleus of an ordinary cell from the animal to be cloned.

When done with the right chemical or electric trigger, this starts the egg dividing as if it had been fertilized by a sperm.

"Cloning animals by nuclear transfer provides an opportunity to preserve endangered mammalian species," they wrote.

"However, it has been suggested that the 'resurrection' of frozen extinct species (such as the woolly mammoth) is impracticable, as no live cells are available, and the genomic material that remains is inevitably degraded," they said.


Wakayama's team dug out some mice that had been kept frozen for years and whose cells were indisputably damaged. Freezing causes cells to burst and can damage the DNA inside. Chemicals called cryoprotectants can prevent this but they must be used before the cells are frozen.

They tried using cells from several places and discovered that the brains worked best. This is a bit of a mystery, as no one has yet cloned any living mouse from a brain cell.

Many animals have been cloned, starting with sheep, and including pigs, cattle, mice and dogs. Livestock breeders want to use cloning to start elite herds of desirable animals, and doctors want to use cloning technology in human medicine.

"There is hope in bringing Ted Williams back, after all," cloning and stem cell expert John Gearhart of the University of Pennsylvania said in an e-mail. The family of Williams, the Boston Red Sox hitter, had his body frozen by cryogenics firm Alcor after he died in 2002.

Gearhart was only half-joking and said the study "may now stimulate the small industry of freezing parts of us before we die to bring us back in the future."

Mammoths may be the extinct animals that scientists would be most likely to try to clone, as many of the animals have been found preserved in ice.

In July 2007 Russian scientists discovered the body of a baby mammoth frozen in the Arctic Yamalo-Nenetsk region for as long as 40,000 years.

"It remains to be shown whether nuclei can be collected from whole bodies frozen without cryoprotectants and whether they will be viable for use in generating offspring following nuclear transfer," Wakayama's team wrote.

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Nanotubes turn on the tunes

Stretchy carbon sheets act as loudspeakers.

nanoflagThe flexible nanotube loudspeaker even works when attached to a flag (roughly 8 cm by 14.5 cm).Jiang Kaili et al., ACS Nano Letters

Stretchable, flexible, transparent sheets of carbon nanotubes can serve as loudspeakers, Chinese researchers have found1. The loudspeakers can be tailored into any size and shape, they say – and to prove their point, they have put one on a waving flag.

Physicist Kaili Jiang at the Tsinghua-Foxconn Nanotechnology Research Centre in Beijing and his colleagues created their loudspeakers from sheets of parallel carbon tubes, each about 10 nanometres across. When they applied an electric current alternating at an audio frequency to these thin films, they were surprised to find that the material could make sounds as loud as commercial speakers.

"It is so wonderfully simple, that it brings up a strong wave of 'Duh, why didn't I think of that!'," says physical chemist Howard Schmidt at Rice University in Houston, Texas.

The nanotube loudspeakers could be stretched to up to twice their original size without breaking and with little change to the intensity of the sound. Their transparent nature could allow them to be placed on windows, video screens, or paintings, the researchers suggest, and their flexibility could allow them to be wrapped around pillars or even be put on clothing. The researchers have already attached one of the transparent films to the screen of an iPod, to play sound from the device.

A sound like thunder

Conventional loudspeakers generate sound by vibrating back and forth. However, when the researchers shone a laser vibrometer on their nanotube loudspeaker, they found it did not vibrate as it emitted sound.

nanospeakersThe carbon nanotube thin-film loudspeaker produces the same sound even while being stretched up to twice its original size.Jiang Kaili et al., ACS Nano Letters

Instead, it generates sound much as lightning produces thunder. When an electric current is applied to the nanotubes, they heat and expand the air near them, creating sound waves. "The difference is that thunder is not a controlled discharge. With carbon nanotubes, you can control the sound and play music," Jiang says.

The heat generated by these loudspeakers can be controlled by how much power they receive — speakers working at ambient temperatures would be preferred for most consumer applications, he adds.

A similar thermoacoustic effect was seen in the late nineteenth century, leading to an invention dubbed the 'thermophone'. However, this device, made with thin metal films, produced extremely weak sounds.

The scientists found that their device was some 260 times more efficient at generating sound than a platinum thermophone. This is because the nanotube film can both heat up faster and transfer its heat to air more rapidly than a thermophone can.

Hot stuff

“It is so wonderfully simple, it brings up a strong wave of 'Duh, why didn't I think of that!'”

Howard Schmidt
Rice University, Houston, Texas

Previous research from materials scientist Pulickel Ajayan, now at Rice University, and his colleagues had shown that carbon nanotubes could generate sound when exposed to light2. However, Ajayan says that the idea of using nanotubes as loudspeakers was new, and "very imaginative and creative".

"Plainly," Schmidt says, "there are a lot of consumer electronics applications for this idea." He adds that future research could explore how well such loudspeakers perform in liquids, perhaps finding use in underwater sonar or miniaturized ultrasound devices.

Ray Baughman, director of the NanoTech Institute at the University of Texas at Dallas, says that he "could even imagine electronic textile-based clothing for injured soldiers or those who are mentally or physically impaired, where spoken words formulated using sensors and computational capabilities embedded in the clothing might help direct the efforts of doctors".

"In the nearer term, these nanotube sheet loudspeakers might provide an economically attractive alternative to loudspeakers in greeting cards, which now comprise a piezoelectric sandwiched between two electrodes," he adds.

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Has new physics been found at the ageing Tevatron?

The Collider Detector at Fermilab has found hints of new physics (Image: Fermilab)
The Collider Detector at Fermilab has found hints of new physics (Image: Fermilab)

While engineers at the Large Hadron Collider (LHC) race to fix its teething problems and start looking for new particles, its ageing predecessor is refusing go silently into the night.

Last week, physicists announced that the Tevatron particle accelerator at Fermilab in Batavia, Illinois, has produced particles that they are unable to explain. Could it be a sign of new physics?

The Collider Detector at Fermilab (CDF) monitors the particles that spew from collisions between protons and anti-protons, which are accelerated and smashed head-on by the Tevatron. The collision occurs inside the 1.5-centimetre-wide "beam pipe" that confines the protons and anti-protons, and the particles created are tracked by surrounding layers of electronics.

In this instance, the CDF was looking at bottom quarks and bottom anti-quarks that decay into, among other things, at least two charged particles called muons.

The team was in for a big surprise. First, they saw far more muons coming from the collisions than expected. But crucially, some of these muons seemed to have been created outside of the beam pipe: they had left no trace in the innermost layer of the detector.

The CDF team says it is unable to explain such muons using the standard model of particle physics, or from what they know of their detector.

Unknown particle

However, "we haven't ruled out a mundane explanation for this, and I want to make that very clear", says CDF spokesperson Jacobo Konigsberg, who adds that it is important that other experiments verify the effect.

While the CDF team is circumspect, theoreticians are more willing to speculate. If the signal is not spurious, this means that some unknown particle with a lifetime of about 20 picoseconds was produced in the collision, travelled about 1 centimetre, through the side of the beam pipe, and then decayed into muons.

"A centimetre is a long way for most kinds of particles to make it before decaying," says Dan Hooper of Fermilab. "It's too early to say much about this. That being said, if it turns out that a new 'long-lived' particle exists, it would be a very big deal."

Dark matter?

Neal Weiner of New York University agrees. "If this is right, it is just incredibly exciting," he says. "It would be an indication of physics perhaps even more interesting than we have been guessing beforehand."

So what could it be? As it happens, Weiner and Nima Arkani-Hamed of the Institute for Advanced Study in Princeton, New Jersey, and colleagues have developed a theory of dark matter – the enigmatic stuff thought to make up a large proportion of the universe – to explain recent observations of radiation and anti-particles from the Milky Way.

Their model posits dark matter particles that interact among themselves by exchanging "force-carrying" particles with a mass of about 1 gigaelectronvolts.

The CDF muons appear to have come from the decay of a particle with a mass of about 1 GeV. So could they be a signature of dark matter? "We are trying to figure that out," says Weiner. "But I would be excited by the CDF data regardless."

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SolFocus Installing World’s Largest Concentrated Solar Project in Spain

Coating helps solar panels soak up more of the sun

By Julie Steenhuysen

CHICAGO (Reuters) - A new type of reflective coating can make solar panels far more efficient, soaking up nearly all available sunlight from nearly any angle, U.S. researchers said on Monday.

Current solar panels -- which convert energy from the sun into electricity -- absorb only about two-thirds of available sunlight.

But surfaces treated with a coating developed at Rensselaer Polytechnic Institute in Troy, New York, can harvest 96.2 percent of sunlight.

"That is a tremendous savings," Rensselaer's Shawn-Yu Lin, whose study appears in the journal Optics Letters, said in a telephone interview.

Lin said the technology addresses two main problems in current solar cells. It captures more colors of solar spectrum and it captures light from all angles.

"If you look at a solar panel, it looks a bit bluish," Lin said. That is "telling you not all of the blue color is being absorbed. It should look totally dark."

The other problem is that solar panels work best when sun shines directly on them. To solve this, large solar arrays mechanically shift position throughout the day -- much like sunbathers on a beach.

Lin and colleagues think they have found a better solution.

Their coating is made up of seven layers of porous material stacked in such a way that each enhances the antireflective properties of the layer below.

Together they act as a buffer zone, trapping light from all angles. "Your efficiency increases by 30 percent," Lin said.

He thinks the material could be applied to all types of solar cells.

"It's not going to require many added instruments too adopted this technology," he said.

(Reporting by Julie Steenhuysen, Editing by Anthony Boadle)

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