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NASA

NASA Successfully Tests 'Flying Saucer' Craft, New Parachute 49

As reported by the Associated Press, via the Washington Post, an update on the promised (and now at least mostly successful) new disc-shaped craft and parachute technology intended for a NASA mission to Mars, though applicable to other space missions as well: A saucer-shaped NASA vehicle launched by balloon high into Earth’s atmosphere splashed down in the Pacific Ocean on Saturday, completing a successful test on Saturday of technology that could be used to land on Mars. Since the twin Viking spacecraft landed on the red planet in 1976, NASA has relied on the same parachute design to slow landers and rovers after piercing through the thin Martian atmosphere. The $150 million experimental flight tested a novel vehicle and a giant parachute designed to deliver heavier spacecraft and eventually astronauts. Despite small problems like the giant parachute not deploying fully, NASA deemed the mission a success. ... [T]he parachute unfurled — if only partially — and guided the vehicle to an ocean splashdown about three hours later. At 110 feet in diameter, the parachute is twice as big as the one that carried the 1-ton Curiosity rover through the Martian atmosphere in 2011. Coatta said engineers won't look at the parachute problem as a failure, but as a way to learn more and apply that knowledge during future tests. ... A ship was sent to recover a "black box" designed to separate from the vehicle and float. Outfitted with a GPS beacon, the box contains the crucial flight data that scientists are eager to analyze. "That's really the treasure trove of all the details," Coatta said. "Pressure, temperature, force. High-definition video. All those measurements that are really key to us to understanding exactly what happens throughout this test."
Music

Secret of the Banjo's Unique Sound Discovered By Nobel Prize-Winning Physicist 101

KentuckyFC (1144503) writes The banjo is a stringed instrument that produces a distinctive metallic sound often associated with country, folk and bluegrass music. It is essentially a drum with a long neck. Strings are fixed at the end of the neck, stretched across the drum and fixed on the other side. They are supported by a bridge that sits on the drum membrane. While the instrument is straightforward in design and the metallic timbre easy to reproduce, acoustics experts have long puzzled over exactly how the instrument produces its characteristic tones. Now David Politzer, who won the Nobel prize for physics in 2004, has worked out the answer. He says the noise is the result of two different kinds of vibrations. First there is the vibration of the string, producing a certain note. However, the drum also vibrates and this pushes the bridge back and forth causing the string to stretch and relax. This modulates the frequency of the note. When frequency of this modulation is below about 20 hertz, it creates a warbling effect. Guitar players can do the same thing by pushing a string back and forth after it is plucked. But when the modulating frequency is higher, the ear experiences it as a kind of metallic crash. And it is this that gives the banjo its characteristic twang. If you're in any doubt, try replacing the drum membrane with a piece of wood and the twang goes away. That's because the wood is stiffer and so does not vibrate to the same extent. Interesting what Nobel prize-winning physicists do in their spare time.

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