Saturday, 30 October 2010

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge

Space Tourism’s Rubbery Rockets May Spur Climate Change

Posted: 29 Oct 2010 03:38 PM PDT

Suborbital spaceflights that rely on rubber-based rocket fuel could shrink icecaps, alter the ozone layer and affect global temperatures, according to a new study.

Yet the study authors' assumptions about the number of rocket launches per year and the chemistry of rocket exhaust have raised questions about their conclusions among space-tourism companies and climatologists not involved in the study.

Atmospheric scientists who performed the research probed the effects of belching ultrafine soot high into the stratosphere, where — unlike the troposphere below it — there isn't rain and wind to quickly filter soot out of the air. Rubber-based rocket fuel burned with nitrous oxide is the preferred propellant of the burgeoning space-tourism industry, and chemists suspect such hybrid engines emit sooty black carbon. Closer to Earth, the stuff has been shown to soak up extra radiation from the sun and contribute to climate change.

"This study was a natural extension of the climate-research community gaining a greater and greater appreciation of black carbon in terms of global radiative forcing," said Martin Ross, an atmospheric scientist at The Aerospace Corporation in El Segundo, California, and leader of the research funded in part by his employer. "Soot is a very large issue in the troposphere," Ross said, but its behavior isn't well-understood at higher altitudes.

To model the effects of space tourist launches on the Earth's atmosphere, Ross and his colleagues used the open-source Whole Atmosphere Community Climate Model Version 3, or WACCM3, one of the most-advanced computer models available to study impacts to global climate.

They ran two supercomputer-powered simulations for two weeks, one as a control and another modeling the impact of 1,000 suborbital flights per year for the next four decades. That many flights, according to the study, would annually deposit more than 1.3 million pounds of soot into the stratosphere.

"We looked at the stated business plans from corporations that are planning to build vehicles for space tourism," Ross said. "If you go to their websites, they'll say things like, 'we plan to launch once per day.' We found 1,000 per year is well within stated objectives of the industry."

On average, according to the simulation, the soot pushed polar ocean temperatures up by 1.8 Fahrenheit degrees, melted 5 to 15 percent of sea ice and depleted 1 percent of tropical ozone (while boosting polar ozone by 6 percent).

"We're not making any particular prediction about any system, just taking reasonable guesses at what soot from a hybrid rocket engine looks like and what the launch industry will do in the future," Ross said. "When we put that into a gold-standard model, the effect on the Earth is surprisingly large. In short, we think black-particle carbon from rockets is something that deserves attention."


Their assumptions may not be perfect, said Gerald North, an atmospheric scientist at Texas A&M University who was not involved in the study, but the measured effect is significant enough to warrant further investigation.

While they make assumptions about some unknowns, such as the behavior of soot at high altitudes, North said, "they're careful in expressing this is not the last word" and are "inviting others to take a look."

Ross and Michael Mills, an atmospheric chemist at the National Center for Atmospheric Research in Colorado and a co-author of the study, said that's precisely what the research team sees as the next step. In particular, getting a handle on what's in the emissions of different types of rocket plumes.

"There are few direct high-altitude measurements of rocket plumes. We really need to get aircraft in those and get measurements of soot and other particles," Mills said. "Until then, the sophistication of our models is limited."

To do just that, Ross said The Aerospace Corporation is planning a workshop to bring together under one tent all the stakeholders in science, rocket engineering, space-tourism companies and the government agencies.

"We need to get these players together and exchanging ideas, then ask the policy people to figure out what to do, if anything, with the information," Ross said.

"I think we and others in the industry welcome the opportunity to talk about all of these issues," said George Whitesides, CEO of Virgin Galactic, a space-tourism company that's planning to use hybrid rocket engines. Whitesides wasn't without reservations about the study and its conclusions, however.

"Frankly, I have to admit I wished they talked to us before putting out a paper, but that's OK. Climate issues are deeply important to Virgin, and we take them very seriously," Whitesides said.

Part of the reason the company chose the hybrid rocket design for its SpaceShipTwo was "because of its significantly lower environmental impact than other designs." Whitesides also said 1,000 space tourist launches per year is "guesswork," because the industry is privatized and young.

"I think as we look at this more, we'll find the impact will be far smaller than that set out in the paper," he said. "In any case, I welcome the conversation."

Whether or not peaceable collaborations ensue, both Ross and Mills expressed that carbon soot is something the nascent space tourism industry can't ignore.

"This shows that a new kind and level of emission being deposited directly into the stratosphere could have a significant effect," Mills said. "Companies need to proceed with developing their systems with full knowledge of consequences on the planet."

Images: 1) Virgin Galactic's SpaceShipTwo (center) attached to WhiteKnightTwo. Flickr/Jeff Foust. 2) The average predicted changes after one decade in the ozone layer (top) and regional temperatures (bottom) caused by 1,000 hybrid rocket launches per year for 40 years. Ross et al. 3) Average seasonal soot deposition, in grams per square meter, in the stratosphere predicted by Ross et al.'s simulation. Ross et al.

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Engineer Finds Secret to Growing Ridiculously Huge Pumpkins

Posted: 29 Oct 2010 11:34 AM PDT

Linus was right after all. Not only does the Great Pumpkin exist, but scientists have figured out how he manages to get so big.

In a sort of self-perpetuating cycle, the bigger a gourd gets, the more physical stress it experiences — thus triggering giant pumpkins to grow even more.

"Their weight generates tension, which pulls cells apart and accelerates growth," says David Hu, a mechanical engineer at the Georgia Institute of Technology in Atlanta, whose team has submitted a paper to a peer-reviewed journal.

Such research doesn't just illuminate the story behind record-setting pumpkins, like the nearly 1,811-pound behemoth recognized this month by Guinness World Records. The work also addresses larger questions of plant development, such as how tissues cope under stress, Hu says.

All giant pumpkins are grown from a single strain, the Atlantic Giant seed, which has a longer growing season than normal pumpkins. The fruits start out round, but once they get to about 220 pounds, they begin to flatten under their own weight, eventually resembling a giant deflated sack.

Wondering how the monsters got so large without splitting, Hu's group squashed regular-sized gourds in the lab to see how much stress they could take before rupturing. The researchers then created a mathematical model of how the fruits could accommodate the stress.

The model predictions matched observations of giant pumpkin dimensions sent in by 50 farmers from around the country. Hu says that plastic, or rreversible, deformation allows the fruit to distribute stresses so it can grow — sometimes adding 50 pounds a day — without breaking.

The New York Botanical Garden, where the world's biggest pumpkin will be carved this weekend, says that a 2,000-pound pumpkin could be grown within the next few years.



Image: Flickr/martine266

Videos: Vimeo/David Hu/Georgia Tech

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The Making of a Mind-Blowing DIY Sun Photo

Posted: 29 Oct 2010 10:42 AM PDT

This stunning portrait of the sun spread like hot plasma all over the internet yesterday. spoke with artist and astrophotographer Alan Friedman to find out how he made it.

Friedman shoots the sky from his backyard in downtown Buffalo, New York. That means the usual celestial candidates — galaxies, nebulae, distant star clusters — are washed out by the glow of the city. But the sun is fair game, as long as the sky is clear and turbulence-free.

"I don't care about sky glow at all," Friedman said. "I just need atmospheric steadiness."

On Oct. 20, Friedman hooked his telescope to a hydrogen-alpha filter, which selects a tiny slice of the visible light spectrum. Hydrogen, the chief component of the sun, radiates strongly in this deep-red light, letting both the sun's outer layers and the feathery filaments that extend away from the disk show up in sharp detail (see photos below).

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Until a few years ago, Friedman says, this kind of filter was only available for research-grade telescopes. They're still not cheap — he got his for around $5,000. Friedman's telescope, which he calls Little Big Man, is small but mighty. The light-collecting aperture is about 3.5 inches wide.

Instead of just snapping a photo, Friedman took 90 seconds of streaming video and selected only the sharpest frames. Each exposure captures about 900 frames, but Friedman threw all but 200 of them away.

In two separate 90-second videos, Friedman zoomed in on the edge of the solar disk to capture wisps of gas arcing along loops of the sun's magnetic field, plus sunspots and the detailed churning of the sun's atmosphere.

Then he inverted the images, making all the dark spots light and the light spots dark. This is an unusual thing for solar photographers to do, he says, but it gives a more authentic view of the sun.

"It's hard to capture the feeling the eye would get looking at the sun without doing that," he said. "It gives a sense of the sun that's both powerful and closer to what you would actually see."

Friedman's camera shoots in black and white, so he also had to add in some color. Although generally he tries to keep his astrophotos as true to science as possible, he took some artistic liberties with the color choice.

"This was a Halloween image," he said. The sun couldn't be anything but orange.

Images: Alan Friedman

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Stone Agers Sharpened Skills 55,000 Years Earlier Than Thought

Posted: 29 Oct 2010 08:20 AM PDT

Stone toolmakers living in southern Africa 75,000 years ago pushed the cutting edge in more ways than one. These intrepid folk sharpened the thin tips of heated stone spearheads using a forceful technique previously dated to no more than 20,000 years ago, a new study finds.

This stone toolmaking method, called pressure flaking, was invented and used sporadically in Africa before spreading to other continents, according to a team led by archaeologist Vincent Mourre of the University of Toulouse-Le Mirail in France. Having a flexible repertoire of toolmaking methods aided the survival of modern humans who left Africa beginning around 60,000 years ago, the scientists propose in the Oct. 29 Science.

The finding fits with the idea that symbolic art, rituals and other forms of modern human behavior developed gradually over hundreds of thousands of years, not in a burst of cultural innovation marked by cave paintings and other creations that appeared after 50,000 years ago in Western Europe.

Excavations of sediment dated to 75,000 years ago in South Africa's Blombos Cave produced stone artifacts displaying signs of pressure flaking, Mourre and his colleagues say.

"The Blombos evidence for pressure flaking is the oldest we know," says anthropologist and study coauthor Paola Villa of the University of Colorado Museum of Natural History in Boulder.


Blombos Cave and nearby sites of comparable age previously yielded engraved pigment chunks, decorated ostrich eggshells and heat-treated stone artifacts.

Southern Africans occasionally made items with symbolic meanings and used special forms of toolmaking beginning 100,000 years ago or more, Villa suspects. These practices flourished in and out of Africa starting about 40,000 years ago, in her view.

Pressure flaking consists of trimming the edges of a finished tool by pressing with a bone point hard enough to remove thin slices of rock. This process creates the narrow, evenly spaced grooves found on flint tools from Europe's 20,000-year-old Solutrean culture and prehistoric Native American groups.

Wider, more irregular grooves characterize 36 pressure-flaked Blombos tools, which were made from silcrete, Villa says. This rock, a silica-rich material, is of lower quality than flint and requires heating to ready it for pressure flaking.

Villa and her colleagues identified glossy areas on silcrete tools at Blombos that, they surmise, formed when the stones were pre-heated for pressure flaking. Other marks on the artifacts indicated that they had been attached to handles, probably as spearheads.

By pressure flaking preheated replicas of the Blombos finds made from silcrete and collected near the South African cave, Mourre was able to reproduce marks resembling those on the ancient artifacts.

Toolmakers likely used pressure flaking by 100,000 years ago in East Africa, remarks archaeologist John Shea of Stony Brook University, New York. Several sites there contain stone artifacts, many made from obsidian, that deserve close analysis for pressure-flaking marks, Shea says.

Shea, an expert at making replicas of Stone Age tools, notes that pressure flaking can be taught in 30 minutes to a novice. "It is, literally, so easy a caveman can do it," he says.

Pressure flaking doesn't add much sharpness or strength to a cutting instrument, Shea adds. Blombos toolmakers probably employed this technique to advertise their skill or to denote users' social identity, he proposes.

Archaeologist Curtis Marean of Arizona State University in Tempe calls the evidence for pressure flaking at Blombos "suggestive but not completely convincing." Further work needs to confirm that pressure flaking of replicated silcrete artifacts consistently produces marks like those on the Blombos finds, Marean asserts.

Knowledge of pressure flaking doesn't imply any special mental or toolmaking abilities, he remarks. Like Shea, Marean regards pressure flaking as a simple way to finish shaping tools made from certain types of stone.

"If the authors are correct that pressure flaking occurred at Blombos Cave, the result is important in that that it extends the time range of the technique," Marean says. "But it's not game-changing in our understanding of the origins of complex cognition."

Images: Copyright Science/AAAS 1) Researchers say that evidence of a special sharpening technique appears near the tips of 75,000-year-old stone artifacts from a South African cave, such as the find shown here. Previous signs of this toolmaking method dated to no more than 20,000 years ago. 2) A Still Bay bifacial point from Blombos Cave made on silcrete and finished by pressure flaking, mainly at the tip.

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