02 September 2013
23 Mai 2013
Darüber rätseln Mathematiker seit 270 Jahren: Lässt sich jede ungerade Zahl größer als fünf als Summe von drei Primzahlen darstellen? Nun will ein Peruaner die legendäre Vermutung von Goldbach bewiesen haben. Eine Überprüfung durch Kollegen steht noch aus.
via SPIEGEL ONLINE - Schlagzeilen http://www.spiegel.de/wissenschaft/mensch/beweis-fuer-schwache-goldbachsche-vermutung-a-901111.html
21 Mai 2013
We're going to need a bigger 'chute
Having honed its oceanic recovery skills, the US was ready to pitch for the Moon with Apollo. Work on the Apollo command module actually began in 1961 - before Gemini - but its "Earth landing system" (ELS) required some extra parachute power to support the capsule's greater weight.
The Apollo 14 command module splashes down on 9 February, 1971
Following reentry, the command module's forward heat shield was jettisoned at an altitude of 7,000m. Drogue 'chutes then slowed it to around 200km/h, until at 3,300m they too were jettisoned and three pilot parachutes pulled out the mains, before splashdown at 35km/h.
Crushable ribs at the first point of capsule contact with the water absorbed some of the impact energy, after which the presumably largely unrattled crew awaited recovery.
The Apollo 11 command module after splashdown in 1969. Pic: NASA
The USSR, meanwhile, had it own lunar ambitions, which ultimately resulted in the highly successful Soyuz spacecraft. Before Soyuz rose from the drawing board, the Voskhod programme deployed a Vostok descent module with the added luxury of solid-fuel braking rocket strapped to the capsule's parachute lines.
Having ditched the Vostok's original cosmonaut ejector seat, this cushioning was essential for ground landings. The Soyuz capsule - a hemisphere atop a barely-angled conical body sitting on a convex heat shield - uses three solid-fuel braking engines which fire just above the ground to do the same job.
Soyuz TMA-04M touches down on 17 September, 2012. Pic: NASA/Carla Cioffi
Soyuz TMA-02M after touchdown in Kazakhstan in 2011. Pic: NASA/Bill Ingalls
Shortly after launch, thing began to go seriously wrong. One of the spacecraft's solar panels failed to unfold, starving the vehicle of power. Breakdown of the automatic stabilisation system and other glitches prompted a mission abort.
Although the spacecraft reentered the atmosphere intact, the main parachute didn't deploy, and Komarov crashed to Earth, becoming the first space flight fatality.3
In 1971, cosmonauts Vladislav Volkov, Georgi Dobrovolski and Viktor Patsayev were killed when their Soyuz 11 capsule depressurised prior to reentry, although recovery crews weren't aware of the fatal accident until the vehicle landed normally in Kazakhstan.
Soyuz has since, however, provided years of reliable service, including servicing the International Space Station.
Soyuz TMA-7 as seen from the International Space Station in October 2005. Pic: NASA
China too has benefited from Soyuz tech, with the capsule for its Shenzhou manned missions reportedly an upscaled version of the Russian design, complete with a trio of braking engines to soften the blow.
The Shenzou 9 capsule lands in Inner Mongolia on 29 June 2012
Next page: Floating Dragons
via www.theregister.co.uk http://www.theregister.co.uk/2013/05/21/reentry_tech/page2.html
20 Mai 2013
Im Jahr der Jubiläen sollte sich die SPD endlich eingestehen: Neben Merkels CDU-light finden die Sozialdemokraten keinen politischen Platz. Es gibt aber eine Lösung. Sie wäre ganz im Sinne August Bebels. Aber bislang fehlt der Partei dafür der Mut.
via SPIEGEL ONLINE - Schlagzeilen http://www.spiegel.de/politik/deutschland/jakob-augstein-ueber-150-jahre-spd-keine-linken-nirgends-a-900785.html
18 Mai 2013
From the wind tunnels the made commercial aviation possible to the analog machines that preceded the computer, a visual history of the spirit of innovation presently unworthy of the government’s dollar.
Among the great joys of spending countless hours rummaging through archives is the occasional serendipitous discovery of something absolutely wonderful: Case in point, these gorgeous black-and-white photographs of vintage NASA (and NASA predecessor NACA) facilities, which I found semi-accidentally in NASA’s public domain image archive. Taken between the 1920s and 1950s, when the golden age of space travel was still a beautiful dream, decades before the peak of the Space Race, and more than half a century before the future of space exploration had sunk to the bottom of the governmental priorities barrel, these images exude the stark poeticism of Berenice Abbott’s science photographs and remind us, as Isaac Asimov did, of NASA’s enormous value right here on Earth.
NACA's first wind tunnel, located at Langley Field in Hampton, VA, was an open-circuit wind tunnel completed in 1920. Essentially a replica of the ten-year-old tunnel at the British National Physical Laboratory, it was a low-speed facility which involved the one-twentieth-scale models. Because tests showed that the models compared poorly with the actual aircraft by a factor of 20, a suggestion was made to construct a sealed airtight chamber in which air could be compressed to the same extent as the model being tested. The new tunnel, the Variable Density Tunnel was the first of its kind and has become a National Historic Landmark. (April 1, 1921)
The Variable Density Tunnel arrives by rail from the Newport News Shipbuilding and Dry Dock Company. The Tunnel was installed at Langley. (February 3, 1922)
Workmen in the patternmakers' shop manufacture a wing skeleton for a Thomas-Morse MB-3 airplane for pressure distribution studies in flight. (June 1, 1922)
A Langley researcher ponders the future, in mid-1927, of the Sperry M-1 Messenger, the first full-scale airplane tested in the Propeller Research Tunnel. Standing in the exit cone is Elton W. Miller, Max M. Munk's successor as chief of aerodynamics. (1927)
16-foot-high speed wind tunnel downstream view through cooling tower section. (February 8, 1942)
Free-flight investigation of 1/4-scale dynamic model of XFV-1 in NACA Ames 40x80ft wind tunnel. (August 18, 1942)
Engine on Torque Stand at the Aircraft Engine Research Laboratory in Cleveland, Ohio, now known as the John H. Glenn Research Center at Lewis Field. Torque is the twisting motion produced by a spinning object. (April 15, 1944)
Detail view of Schlieren setup in the 1 x 3 Foot Supersonic Wind Tunnel. (October 26, 1945)
Boeing B-29 long range bomber model was tested for ditching characteristics in the Langley Tank No. 2 (Early 1946)
Looking down the throat of the world's largest tunnel, 40 by 80 feet, located at Ames Aeronautical Laboratory, Moffett Field, California. The camera is stationed in the tunnel's largest section, 173 feet wide by 132 feet high. Here at top speed the air, driven by six 40-foot fans, is moving about 35 to 40 miles per hour. The rapid contraction of the throat (or nozzle) speeds up this air flow to more than 250 miles per hour in the oval test section, which is 80 feet wide and 40 feet high. The tunnel encloses 900 tons of air, 40 tons of which rush through the throat per second at maximum speed. (1947)
Analog Computing Machine in the Fuel Systems Building. This is an early version of the modern computer. The device is located in the Engine Research Building at the Lewis Flight Propulsion Laboratory, now John H. Glenn Research Center, Cleveland Ohio. (September 28, 1949)
Guide vanes in the 19-foot Pressure Wind Tunnel at Langley Aeronautical Laboratory, National Advisory Committee for Aeronautics, form an ellipse 33 feet high and 47 feet wide. The 23 vanes force the air to turn corners smoothly as it rushes through the giant passages. If vanes were omitted, the air would pile up in dense masses along the outside curves, like water rounding a bend in a fast brook. Turbulent eddies would interfere with the wind tunnel tests, which require a steady flow of fast, smooth air. (March 15, 1950
24-foot-diameter swinging valve at various stages of opening and closing in the 10ft x 10ft Supersonic Wind Tunnel. (May 17, 1956)
A television camera is focused by NACA technician on a ramjet engine model through the schlieren optical windows of the 10 x 10 Foot Supersonic Wind Tunnel's test section. Closed-circuit television enables aeronautical research scientists to view the ramjet, used for propelling missiles, while the wind tunnel is operating at speeds from 1500 to 2500 mph. (8.570) The tests were performed at the Lewis Flight Propulsion Laboratory, now John H. Glenn Research Center. (April 21, 1957)
8ft x 6ft Supersonic Wind Tunnel Test-Section showing changes made in Stainless Steel walls with 17 inch inlet model installation. The model is the ACN Nozzle model used for aircraft engines. The Supersonic Wind Tunnel is located in the Lewis Flight Propulsion Laboratory, now John H. Glenn Research Center. (August 31, 1957)
The Gimbal Rig, formally known as the MASTIF of Multiple Axis Space Test Inertia Facility, was engineered to simulate the tumbling and rolling motions of a space capsule and train the Mercury astronauts to control roll, pitch and yaw by activating nitrogen jets, used as brakes and bring the vehicle back into control. This facility was built at the Lewis Research Center, now John H. Glenn Research Center at Lewis Field. (October 29, 1957)
Lockheed C-141 model in the Transonic Dynamics Tunnel (TDT). By the late 1940s, with the advent of relatively thin, flexible aircraft wings, the need was recognized for testing dynamically and elastically scaled models of aircraft. In 1954, NASA's predecessor agency, the National Advisory Committee on Aeronautics (NACA), began converting the Langley 19-foot Pressure Tunnel for dynamic testing of aircraft structures. The old circular test section was reduced to 16 x 16 feet, and slotted walls were added for transonic operation. The TDT was provided with special oscillator vanes upstream of the test section to create controlled gusty air to simulate aircraft response to gusts. A model support system was devised that freed the model to pitch and plunge as the wings started oscillating in response to the fluctuating airstream. The TDT was completed in 1959. It was the world's first aeroelastic testing tunnel. (November 16, 1962)
Alas, the names of the photographers — as is often the case with creators working on the government dollar — were not preserved. If you recognize any, get in touch and help credit them.
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via Brain Pickings http://www.brainpickings.org/index.php/2013/05/17/vintage-nasa-facilities/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+brainpickings%2Frss+%28Brain+Pickings%29
15 Mai 2013
Fanbois versus PHDs: the science community votes
"A lot of people get frustrated," Grazier said of BSG's following. "You have to have a good sense of when the science can be stretched and not be absolute. I found it's people with a little science education who will give us grief online. People with a lot of science education are more forgiving. They'd say: 'You did this here. If you did this, it might work.' The people with PHDs in physics are more willing to give us leeway. That's counter-intuitive!"
A clear sci-fi fan, Grazier gets frustrated with films that try to artificially ramp up the dramatic content when the science itself would have been dramatic enough. Just "getting it right" can create the impact - something he aimed for in BSG.
Grazier cites 1998's blockbuster Armageddon, when a "planet-killing" asteroid the size of Texas - Texas is the US' second largest state with 261,797 square miles of land FYI - is bearing down on Earth, and roughnecks led by Bruce Willis swing into action. Grazier claims it lost him less than a minute from the start of the film.
"In the first 39 seconds, we see the K-T Impact of the asteroid that killed the dinosaurs. Had they had a science adviser, it would have been more dramatic," he reckons.
"Charlton Heston said in his best Moses voice [over]: 'It hit with the force of 10,000 nuclear weapons.' It was more like 41 million. It was only four to six miles across, maybe 10, but that was a lot of energy, and had they checked on the science they could have made it much more dramatic. They didn't and they just picked some number out of a hat."
Smaller than Texas, but just as bad: how the K-T Impact might have looked according to NASA
Details for Grazier clearly lend credibility and sell a story. He's a huge fan of 2010: The Year We Make Contact over the more widely acclaimed 2001: A Space Odyssey, also by Arthur C. Clarke. Why? Details.
"When they approach Discovery [the ship that's home to the murderous Hall 9000] in orbit around Jupiter's moon Io and it's covered in sulphur, which it would be because it's a volcanic moon, I thought: 'How cool is that?' That's a level of detail they didn't have to do but they thought about it."
"That movie is influential for me in terms of how much the science is right. There are a few places where they say: 'Come take a leap with me,' such as adding mass to Jupiter to turn it into a star and the fact the moons didn't vaporize, but that was one that was real influential for me because of the level of detail and how well they got the science right."
It was details that got him hooked on BSG too, when Moore was touting his idea. Grazier was attending Galacticon, celebrating the anniversary of the original Battlestar Galactica series, where Moore showed clips from the then up-coming miniseries.
"The moment I realized I wanted to work on the show was [when] they were lining up a Viper in a launch tube, and you see the wind swirling down and the water condensing as it swirls down the launch tube. That was the moment when I said: 'I so want to work on that.'"
He asked a film industry contact for an interview with Moore and got it. Grazier got five minutes, and Moore asked about Grazier's military background, which turned up the fact Moore was also ex-RTC. A recommendation helped nail it.
How did Grazier end up as a science adviser before that? Studying as a UCLA grad student, he pitched an unsolicited manuscript to Paramount for an episode of Voyager with a writing partner. The studio got 3,000 such manuscripts a year with the vast majority rejected, but Grazier's was read. He was asked to pitch more and one of the people he pitched was Voyager's Michael Taylor, who went on to join the BSG crew.
To infinity and beyond
Since then, Grazier's worked on Syfy's Eureka - set in an Oregon town populated by boffins working for the Global Dynamics corporation - and consulted on Warner Bros.' planned space thriller Gravity, and the pilot of NBC's political and science thriller The Event. When The Reg last spoke to Grazier, he'd been filming a series for National Geographic on - yes - space. It covers stars, things you can mine in space, and the effects of travel in space on the body.
Despite his TV and film commitments, Grazier says he's not a full-time science consultant or adviser. His job remains with NASA and Cassini. But sci-fi does leak into his daily life: Grazier describes his office as "nirvana" with its life-size poster of a Cylon Centurion, a 4x6 poster from Eureka and models of the USS Enterprise and a Klingon Bird of Prey.
He has, he says, a dream job. Two dream jobs, in fact: science and science fiction. For someone who was a kid when man landed on the Moon and the first episodes of Star Trek hit US TV, that's hard to beat. ®
You can find out more about The Science of Battlestar Galactica, including where to buy it, here.
via www.theregister.co.uk http://www.theregister.co.uk/2010/11/03/the_science_of_battlestar_galactica/page4.html