Science and Technology News

Saturday, June 30, 2012

Improving The Hand Grenade


By Eric Kowal, RDECOM

As far as the design of the basic hand grenade goes, essentially it has been frozen in time.

The first pull-pin design with a lever and delayed fuze dates back to May 1915 and is often referred to as the grandfather to the current variation.

“The basic technology is almost 100 years old,” said Richard Lauch, a Picatinny Arsenal engineer, referring to the Mills Bomb No. 5.

The Mills bomb is the popular name for a series of prominent British hand grenades.  They were the first modern fragmentation grenades and named after William Mills, a hand grenade designer.

Lauch, who served in the U.S. Marine Corps, has been on a mission to modernize the hand grenade so that it is safer as well as easier to use and cheaper to produce.

During the last year and half of his Marine service, Lauch was primary marksmanship instructor in the Weapons Training Battalion at Marine Corps Recruit Depot, San Diego, Calif.

While he was assisting in training recruits on the proper use of the M67 hand grenade, Lauch became intimately familiar with what he saw as the grenade’s deficiencies.
 The current grenade fuze design only allows for a right-handed user to throw it in the upright position. A lefty has to hold the grenade upside down to safely pull the pin.

Also, the current fuze consists of an explosive train that is in-line from production through usage; thus, it is always “armed.”

In a grenade, the explosive train is the sequence of events that begins when the handle is released. That initiates a mechanical strike on a primer, which ignites a slow-burning fuze to provide time for the grenade to be thrown before the fuze sets off the primary explosive.

In an “in-line” explosive train, the sequence is always in-place and ready.  Until it is removed, a pin in the handle is the only thing that prevents the sequence from being initiated.

Lauch believes his design is safer because a lefty or righty holds the grenade no differently, and because the grenade can only be armed by rotating the explosive chain in line

Provocative Prescription for Chemical Evolution in Plants


Researchers speculate "specialized metabolism" was key to terrestrial takeover of plants

"Plants produce a repository of structurally diverse chemicals ..." That's how a new paper begins that proposes some provocative ideas about how plants developed the wide assortment of chemicals they use to sustain life and how they developed other chemicals that may or may not contribute to their immediate survival, but instead often ensure reproductive success in changing, earth environments.

In a June 29 journal Science review paper, Joseph P. Noel, a lead investigator at the Salk Institute for Biological Studies and the Howard Hughes Medical Institute, and colleagues speculate that plant chemodiversity results from rapid and sometimes unanticipated evolutionary steps.

Noel, along with Jing-Ke Weng and Ryan Philippe also with the Salk Institute, theorize that a very early form of chemical reactions that occurred in the prebiotic soup paved the way for production of chemicals important to the survival of the earliest cellular organisms--chemicals including those essential for building nucleic acids--biological molecules such as DNA, RNA and proteins necessary for encoding, transmitting and expressing genetic information.

The researchers speculate these chemical processes, now catalytically robust, evolved into separate pathways both in early plants and in their aquatic ancestors.

One pathway--having chemical processes termed primary metabolism--allowed the production of life-sustaining chemicals.

The other pathway produced chemicals that no longer carry life sustaining functions. Instead, these chemicals have more subtle effects on plants' fitness, or reproductive success in their local environments.

In the paper, the researchers hypothesize these secondary chemical processes arose from the more conserved, life-sustaining processes and term them "specialized metabolism."

"Understanding how plants evolved their ability to synthesize secondary metabolites--such a vast and diverse array of chemicals--is a challenging problem," said Parag Chitnis, director of NSF's Division of Molecular & Cellular Biosciences, which funded Noel's research. "In this article, Dr. Noel and his colleagues present an attractive and plausible explanation."

Noel, Weng and Philippe speculate that specialized metabolism is more malleable than life-sustaining metabolic processes, and that specialized metabolic systems can evolve rapidly to produce new "tailor-made molecules" as means to adapt to ever-changing environments.

"Primary metabolism likely arose from promiscuous primeval metabolic reactions and evolved toward greater catalytic precision and efficiency," the researchers write in their article. "Specialized metabolism likely emerged from primary metabolism."

According to the researchers, specialized metabolism likely permitted more and varied chemical reactions and natural products because the enzymes responsible for their synthesis were more flexible in ways scientists are only now beginning to understand at the molecular level.

The upshot was the emergence of secondary chemical reactions that produce color in flowers; rubber for vehicle tires; flavor, smells, nutrition and browning in fruits and wine; natural plant antibiotics; fragrances to attract pollinators and repel herbivores, and even the characteristic aroma and flavor of the cabbage and tomato families.

"Plant secondary metabolism generates a huge diversity of chemicals that are not only very important to the plant, but also for humans," said Greg Warr, a program manager in NSF's Division of Molecular & Cellular Biosciences. "For example, we often depend on plant products for nutrition, fuel, biorenewable chemicals, clothing, shelter and pharmaceuticals."

What's more, Noel and colleagues speculate the depth of specialized metabolism likely mirrored the takeover of Earth by plants that form the essential core of the global food network. As primary metabolism produced life-sustaining chemical reactions, specialized metabolism gave rise to secondary chemical reactions that allowed plants to adapt to geographically dispersed environments, many of which are challenging to other forms of life.

For example, some metabolites, plant hormones regulate various aspects of plant growth and development in response to environmental cues, while others act as ultraviolet sunscreens and prevent dehydration.

"The ability of these complex biological systems in plants to evolve quickly to solve problems of plant survival and reproduction, will ultimately teach us the lessons learned over a 500 million year old experiment plants have been conducting since the dawn of terrestrial life," said Noel.

"Without this ongoing experiment, humankind and all the animal life we know of on the terrestrial earth would cease to exist."

The researchers hope the Science review paper will help provide a provocative and more informed set of hypotheses regarding the amazing tapestry of plant chemistry while also posing still unanswered but fundamental problems to life. "It will certainly guide future research in this important area," said Chitnis.

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Hubble, Swift Detect First-Ever Changes In An Exoplanet Atmosphere


J. D. Harrington
Headquarters, Washington
202-358-5241
j.d.harrington@nasa.gov
 
Lynn Chandler
NASA Goddard Space Flight Center, Greenbelt, Md.
301-286-2806
lynn.chandler-1@nasa.gov

WASHINGTON -- An international team of astronomers using data from NASA's Hubble Space Telescope has made an unparalleled observation, detecting significant changes in the atmosphere of a planet located beyond our solar system.

The scientists conclude the atmospheric variations occurred in response to a powerful eruption on the planet's host star, an event observed by NASA's Swift satellite.

"The multiwavelength coverage by Hubble and Swift has given us an unprecedented view of the interaction between a flare on an active star and the atmosphere of a giant planet," said lead researcher Alain Lecavelier des Etangs at the Paris Institute of Astrophysics (IAP), part of the French National Scientific Research Center located at Pierre and Marie Curie University in Paris.

The exoplanet is HD 189733b, a gas giant similar to Jupiter, but about 14 percent larger and more massive. The planet circles its star at a distance of only 3 million miles, or about 30 times closer than Earth's distance from the sun, and completes an orbit every 2.2 days. Its star, named HD 189733A, is about 80 percent the size and mass of our sun.

Astronomers classify the planet as a "hot Jupiter." Previous Hubble observations show that the planet's deep atmosphere reaches a temperature of about 1,900 degrees Fahrenheit (1,030 C).

HD 189733b periodically passes across, or transits, its parent star, and these events give astronomers an opportunity to probe its atmosphere and environment. In a previous study, a group led by Lecavelier des Etangs used Hubble to show that hydrogen gas was escaping from the planet's upper atmosphere. The finding made HD 189733b only the second-known "evaporating" exoplanet at the time.

The system is just 63 light-years away, so close that its star can be seen with binoculars near the famous Dumbbell Nebula. This makes HD 189733b an ideal target for studying the processes that drive atmospheric escape.

"Astronomers have been debating the details of atmospheric evaporation for years, and studying HD 189733b is our best opportunity for understanding the process," said Vincent Bourrier, a doctoral student at IAP and a team member on the new study.

When HD 189733b transits its star, some of the star's light passes through the planet's atmosphere. This interaction imprints information on the composition and motion of the planet's atmosphere into the star's light.

In April 2010, the researchers observed a single transit using Hubble's Space Telescope Imaging Spectrograph (STIS), but they detected no trace of the planet's atmosphere. Follow-up STIS observations in September 2011 showed a surprising reversal, with striking evidence that a plume of gas was streaming away from the exoplanet.

The researchers determined that at least 1,000 tons of gas was leaving the planet's atmosphere every second. The hydrogen atoms were racing away at speeds greater than 300,000 mph. The findings will appear in an upcoming issue of the journal Astronomy & Astrophysics.

Because X-rays and extreme ultraviolet starlight heat the planet's atmosphere and likely drive its escape, the team also monitored the star with Swift's X-ray Telescope (XRT). On Sept. 7, 2011, just eight hours before Hubble was scheduled to observe the transit, Swift was monitoring the star when it unleashed a powerful flare. It brightened by 3.6 times in X-rays, a spike occurring atop emission levels that already were greater than the sun's.

"The planet's close proximity to the star means it was struck by a blast of X-rays tens of thousands of times stronger than the Earth suffers even during an X-class solar flare, the strongest category," said co-author Peter Wheatley, a physicist at the University of Warwick in England.

After accounting for the planet's enormous size, the team notes that HD 189733b encountered about 3 million times as many X-rays as Earth receives from a solar flare at the threshold of the X class.

Hubble is a project of international cooperation between NASA and the European Space Agency. Swift is operated in collaboration with several U.S. institutions and partners in the United Kingdom, Italy, Germany and Japan. NASA's Goddard Space Flight Center in Greenbelt, Md., manages both missions.

For images and video related to this finding, visit http://go.nasa.gov/Osbvfi.
 
For more information about Swift, visit http://www.nasa.gov/swift.
 
For more information about Hubble, visit http://www.nasa.gov/hubble.

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Friday, June 29, 2012

NASA'S Cassini Finds Probable Subsurface Ocean on Saturn Moon


Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown@nasa.gov
 
Jia-Rui C. Cook
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0850
jccook@jpl.nasa.gov

WASHINGTON -- Data from NASA's Cassini spacecraft have revealed Saturn's moon Titan likely harbors a layer of liquid water under its ice shell.

Researchers saw a large amount of squeezing and stretching as the moon orbited Saturn. They deduced that if Titan were composed entirely of stiff rock, the gravitational attraction of Saturn would cause bulges, or solid "tides," on the moon only 3 feet (1 meter) in height. Spacecraft data show Saturn creates solid tides approximately 30 feet (10 meters) in height, which suggests Titan is not made entirely of solid rocky material. The finding appears in today's edition of the journal Science.

"Cassini's detection of large tides on Titan leads to the almost inescapable conclusion that there is a hidden ocean at depth," said Luciano Iess, the paper's lead author and a Cassini team member at the Sapienza University of Rome, Italy. "The search for water is an important goal in solar system exploration, and now we've spotted another place where it is abundant."

Titan takes only 16 days to orbit Saturn, and scientists were able to study the moon's shape at different parts of its orbit. Because Titan is not spherical but slightly elongated like a football, its long axis grew when it was closer to Saturn. Eight days later, when Titan was farther from Saturn, it became less elongated and more nearly round. Cassini measured the gravitational effect of that squeeze and pull.

Scientists were not sure Cassini would be able to detect the bulges caused by Saturn's pull on Titan. By studying six close flybys of Titan from Feb. 27, 2006, to Feb. 18, 2011, researchers were able to determine the moon's internal structure by measuring variations in the gravitational pull of Titan using data returned to NASA's Deep Space Network (DSN).

"We were making ultrasensitive measurements, and thankfully Cassini and the DSN were able to maintain a very stable link," said Sami Asmar, a Cassini team member at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "The tides on Titan pulled up by Saturn aren't huge compared to the pull the biggest planet, Jupiter, has on some of its moons. But, short of being able to drill on Titan's surface, the gravity measurements provide the best data we have of Titan's internal structure."

An ocean layer does not have to be huge or deep to create these tides. A liquid layer between the external, deformable shell and a solid mantle would enable Titan to bulge and compress as it orbits Saturn. Because Titan's surface is mostly made of water ice, which is abundant in moons of the outer solar system, scientists infer Titan's ocean is likely mostly liquid water.

On Earth, tides result from the gravitational attraction of the moon and sun pulling on our surface oceans. In the open oceans, those can be as high as two feet (60 centimeters). While water is easier to move, the gravitational pulling by the sun and moon also causes Earth's crust to bulge in solid tides of about 20 inches (50 centimeters).

The presence of a subsurface layer of liquid water at Titan is not itself an indicator for life. Scientists think life is more likely to arise when liquid water is in contact with rock, and these measurements cannot tell whether the ocean bottom is made up of rock or ice. The results have a bigger implication for the mystery of methane replenishment on Titan.

"The presence of a liquid water layer in Titan is important because we want to understand how methane is stored in Titan's interior and how it may outgas to the surface," said Jonathan Lunine, a Cassini team member at Cornell University. "This is important because everything that is unique about Titan derives from the presence of abundant methane, yet the methane in the atmosphere is unstable and will be destroyed on geologically short timescales."

A liquid water ocean, "salted" with ammonia, could produce buoyant ammonia-water liquids that bubble up through the crust and liberate methane from the ice. Such an ocean could serve also as a deep reservoir for storing methane.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The mission is managed by JPL for NASA's Science Mission Directorate in Washington. DSN, also managed by JPL, is an international network of antennas that supports interplanetary spacecraft missions and radio and radar astronomy observations for the exploration of the solar system and the universe. The network also supports selected Earth-orbiting missions. Cassini's radio science team is based at Wellesley College in Massachusetts.

For more information about the mission, visit http://www.nasa.gov/cassini.

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