viernes, 6 de noviembre de 2009
Einstein's Cosmic Speed Limit
[Host] Light, we all know it travels at well, the speed of light, or does it? When it comes to the structure of space and time, could light be the key to unlocking the final secrets of the universe? Answers may lie in the journey of two photons across seven billion light years of space, recorded by the Fermi Gamma-ray Space Telescope. And these two tiny particles have just opened up a whole new chapter in our understanding of light, gravity, and the universe around us.
[Julie McEnery] We're really excited because we've captured rare experimental evidence probing the fundamental structure of space and time. [Host] Meet NASA's gamma-ray detectives. Led by project scientist Julie McEnery, they're searching for clues about the high-energy mysteries of our universe. But, they'll need more than a magnifying glass this. The team's one of kind tool? The Fermi satellite. Fermi looks at gamma-rays, the highest-energy form of light and it just surprised everyone with a discovery about the fabric of space and time.
[Julie McEnery] So you might be thinking, two tiny particles of light, why is that important? Well you have to look at the very large and the very small together to understand the universe as a whole. So far, Einstein's Theory of Relativity, which describes space and time as a smooth fabric that's distorted, or bent by massive objects, has been a spectacularly sucessful explaination of gravity and the large scale behavior of the universe. Whereas Quantum Mechanics, another spectacularly successful model describes the workings of atoms subatomic particles and some of the fundamental forces of nature. Scientists have never been able to reconcile the two. Both Relativity and Quantum Mechanics are equally fundamental in their own regimes. So scientists want to find a theory of everything that describes the universe as a whole. And the observations that we've made these two photons with Fermi takes us one step closer to achieving the goal of having a Theory of Everything that combines the most sucessful aspects of Quantum Mechanics and Relativity into one unified theory.
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[Host] To add to this puzzle, other telescopes have observed gamma rays with different wavelengths arriving at Earth at different times. According to Einstein's Special Theory of Relativity, all forms of electromagnetic radiation from radio and infrared, to visible light, to X-rays and even gamma-rays moves at the same speed. So what would explain these differences in arrival times? One simple idea is that maybe the photons were just emitted at different times. More interestingly though, maybe there was something in the very fabric of space that was causing the higher-energy particle to slow down. If this is true, could Einstein have been wrong? Could a higher-energy particle move slower than the speed of light?
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Several ideas, which attempt to reconcile relativity and quantum mechanics suggest that space and time are not actually smooth and uniform. But are instead a seething froth when seen at the smallest scale. Like bubble wrap viewed from far away, at human scales this texture would be invisible. A low -energy, long wavelength photon is unaffected by the lumpiness of space. But a high-energy, short wavelength photon is hindered by the froth. This makes it move more slowly than lower-energy radiation, so it breaks Einstein's law that all light particles must travel at the same speed. However, this explanation had little experimental proof either way--until Fermi arrived.
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[Julie] We observed a gamma-ray burst. A gamma-ray bust is a huge explosion. That gamma-ray burst produced a large number of photons, one of which had enormous energy, and very short wavelengths. Those photons travelled seven billion year to reach us, and yet the highest energy, the shortest wavelength of photon arrived within 900 milliseconds of the lower-energy photons. That's a little bit like racing two speed-boats, one through water and the other through molasses, and having them arrive at the same time; it just doesn't happen. Because Fermi saw no delay in the arrival time of the two photons, it confirms that space and time is smooth and continuous as Einstein had predicted. And it shuts the door on several theories of everything that had predicted that space and time might be foamy enough to interfere with light.
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[Host] So, if space-time really isn't just invisible bubble wrap, what is it? Fermi's eliminated some ideas from the mix, and that means we're one step closer to potentially unifying Relativity and Quantum Mechanics. After all, science is a process of elimination, and unless we keep eliminating, we may never know if this Theory of Everything actually exists, hidden in the math of our universe. But for now, we'll have to keep searching for clues beyond our small planet, because the answers truly lie among the stars.
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jueves, 5 de noviembre de 2009
El Vehículo de Retorno de Tripulación el X-38 Encuentra Nuevo Hogar
Uno de los tres Vehículos de Retorno de Tripulación X-38 de la NASA de prueba que voló en el Centro de Investigación de Vuelo Dryden de la NASA en la Base de la Fuerza Aérea,California, hace una década, ha encontrado un nuevo hogar en el corazón de América.
En esta imagen de los vuelos de prueba en 1999, el vehículo de investigación X-38 se deja caer del avión nodriza B-52 de la NASA inmediatamente después de ser liberado de la viga del ala del B-52. Más de 30 años antes, este mismo B-52 lanzaba los originales vehículos de cuerpo sustentador probados por la NASA y la Fuerza Aérea en lo que ahora es llamado el Centro de Investigación del Vuelo Dryden y el Centro de Pruebas del Vuelo de la Fuerza Aérea.
El artefacto de cuerpo sustentador sin alas fue tranferido el fin de semana pasado desde el Centro Espacial Johnson de la NASA en Houston al Museo del Espacio y el Aire, situado justo al lado de la carretera interestatal 80 en Ashland, Nebraska, a unos 20 kilómetros al sureste de Omaha. El X-38 se suma a la creciente colección de vehículos aeroespaciales y otros dispositivos historicos del museo.
El traslado del segundo X-38 construido al museo cuenta con una conexión de ajuste, ya que los vehículos X-38 eran lanzados desde el aire desde el famoso avión nodriza B-52B 008. El bombardero B-52 sirvió de columna vertebral del Comando del Aire Estratégico de la Fuerza Aérea durante la historia del comando.
Antes de la cancelación, el programa del X-38 era el desarrollo de la tecnología de los vehículos propuestos que podrían regresar hasta siete tripulantes de la Estación Espacial Internacional a la Tierra en caso de una emergencia. Estos vehículos se habrían llevado a la estación espacial en la bodega de un transbordador espacial y serían acoplados a los puertos. Si surgiera una emergencia que obligara a la tripulación de la ISS a salir de la estación espacial, un Vehículo de Retorno de Tripulación sería desacoplado y los retornaría a la Tierra de igual forma como el transbordador espacial, aunque el vehículo desplegaría un paracaídas para el descenso y aterrizaje final.
Credit de la Foto: NASA / Carla Thomas
Estudios Antárticos del Hielo Marino.
Un iceberg es visto por la ventana de un avión de Investigación DC-8 de la NASA, cuando volaba a 2.000 pies sobre el Mar de Amundsen en la Antártida Occidental el miércoles 21 de octubre de 2009. Este fue tomado en el cuarto vuelo científico sesiones de la Operación de la NASA de hielo puente aéreo misión científica de la Tierra para estudiar capas de hielo de la Antártida, el hielo marino, y las plataformas de hielo.
En el punto medio de esta campaña de campo, siete vuelos sobre la Antártida se han completado en los primeros 13 días de la Operación Puente de Hielo. La misión está en camino de completar sus 17 vuelos previstos a mediados de noviembre.
Qué el objetivo de vuelo sea trasladado en un día determinado depende principalmente de las difíciles condiciones meteorológica de la Antártida. Varios de los instrumentos de a bordo no pueden recoger datos a través de las nubes. Hasta ahora, dos vuelos han sido cancelados en el último minuto debido a la nieve en el aeropuerto de Chile austral.
A partir del aterrizaje del vuelo del 27 de octubre, los objetivos cumplidos incluyen: tres vuelos sobre los glaciares, dos sobre el hielo marino, uno sobre la plataforma de hielo Getz, y otro para estudiar la topografía de la capa de hielo en la aproximación más cercana de la misión al Polo Sur.
Crédito de la Imagen: NASA / Jane Peterson
http://www.nasa.gov/multimedia/imagegallery/image_feature_1507.html
miércoles, 4 de noviembre de 2009
Aerial View of Ares 1-X Launch
We're pleased to share with you today some really unique video coverage from last week's Ares I-X launch. A Cessna Skymaster aircraft, flying at 12,000 feet in the vicinity of booster splashdown and equipped with a gyro-stabilized camera, captured this high-definition video. This footage gives us some extremely valuable engineering data, as well as spectacular footage of the recovery sequence in rarely seen detail.
First a few words to preview what you will see after booster burnout, as some of the events happen quickly. First you'll see the thrust plume diminish followed by a brief flash, which is the firing of the booster deceleration motor, then a smaller flash on the side of the booster, which is the tumble motor firing. Then after a couple minutes of descent, you will see the drogue chute deploy to stabilize the booster tail-down. Then, the forward skirt assembly is jettisoned and the drogue pulls it up and away from the booster. The three main parachutes follow immediately, and you will be able to see how one deflates and a second remains only partially inflated. Right before water impact, if you look closely at the nozzle, you will see the jettison of the nozzle extension and then booster splashdown. Finally, you will see the drogue lowering the forward skirt assembly in a second splashdown event just to the left of the booster.
The first stage flew very precisely and smoothly through ascent. Our primary interests on ascent included vehicle control margins, roll stability and also an assessment of thrust oscillation. We saw very positive results with respect to controllability. The roll control system only fired three times during all of ascent, while our preflight analysis predicted as many as 20 firings of the RoCS system. So, this is an excellent outcome. Also, we saw minimal vibration due to thrust oscillation, both in the data and from onboard cameras. The pressure oscillations from the Ares I-X booster were well within historical levels seen on shuttle flights.
As the booster burns out, you see here a flash during the firing of the booster deceleration motor, then, you see here the firing of the booster tumble motor. The booster begins to rotate and separate from the upper stage. You notice also that the upper stage begins to rotate. This was expected, as the upper stage did not have a control system. In fact, the separation event for Ares I-X was more challenging than Ares I design conditions. Because we only had four segments of propellant, we burned out at lower altitude and higher dynamic pressures -- 90 pounds per square foot for Ares I-X, as compared to only 10 pounds per square foot for Ares I. So, this resulted in a stress case separation and was very successful.
One thing to watch here during the descent of the booster is the trailing smoke from the nozzle. This helps us see the flight path of the descent, which initially is horizontal to the Earth, and later as the vehicle slows will become more vertical. Early on in our engineering assessments for Ares I-X we were concerned we might have a nose-first re-entry of the booster because of the forward-end weight of the fifth segment simulator. About a year ago, we had calculated up to 20 percent probability of nose-first re-entry, which would have likely resulted in burn-up of the parachute assembly and loss of the booster. After several refinements to our weight and balance of the booster, we got our predictions down to only a 3 percent probability of nose-first re-entry, which proved to be valid on our I-X flight test, as the vehicle stabilized nozzle-down for most of the descent. Several oscillations can be seen in the booster orientation, and as speed decreases, the flight path becomes nearly vertical as seen by the trailing smoke plume.
It is interesting to note that during the vertical descent there is a slow oscillation and the booster is actually at about 110-degree angle of attack to the flight path as the drogue chute deploys. This results in several dramatic oscillations under the drogue, but it performs beautifully and the booster stabilizes nicely after about four oscillations.
Watch closely at the top of the booster here as the forward skirt extension is jettisoned and pulled away by the drogue. This entrains the risers of the three main parachutes for their initial inflation to the "reefed," or partially inflated, position. All three chutes make it to this first inflation position but the chute on the left quickly deflates and fails, trailing a streamer, which appears to strike the chute in the middle, perhaps damaging it as well.
So, just prior to water entry we essentially have 1 1/2 chutes suspending the booster. Also, at this point you can see the nozzle extension pyrotechnically severed at the bottom of the booster, just before water entry. The booster hits at a higher velocity than planned, which causes a hard slapdown and buckling of the aft segment motor case. This has also been experienced in the shuttle program. A total of 11 chute deployment failures have occurred in the life of the shuttle program, most recently on STS-128. So, we have abundant data here to resolve this for future missions. Ares I-X was also a parachute stress test, as the booster was nearly 40,000 pounds heavier than an Ares five segment booster due to the hardware in the fifth segment simulator. The parachutes were a world-record-setting 150-foot diameter, and were tested at total payload weight for the first time during Ares I-X.
Now that the booster is down in the water, watch for the drogue and forward skirt extension to enter into the image just to the left of the booster. All of these sequences worked exactly as designed. Today, the booster is on dock at Cape Canaveral and is undergoing teardown inspections. In the next few days, we will be able to recover the data recorders and begin the detailed data analysis of the entire flight.
lunes, 2 de noviembre de 2009
El Spirit Embebido en Suelo Blando en Marte mientra los Ingenieros Idean métodos para Liberarlo.
Este punto de vista de la cámara panorámica del Rover Explador de Marte, el Spirit de la NASA muestra el terreno que rodea el lugar llamado "Troy", donde el Spirit se insertó en el suelo blando durante la primavera de 2009. Los cientos de imágenes combinadas en esta fotografía fueron tomadas a partir del 1906 avo día marciano (o sol) de la misión Spirit en Marte (14 de mayo de 2009) y termina en el Sol 1943 (20 de junio de 2009).
Cerca del centro de la imagen, en la distancia, se encuentra la Colina Husband, donde el Spirit tomó fotos de la cumbre en el 2005. Por la escala, las huellas paralelas son de aproximademente 1 metro (39 pulgadas). La huella de la derecha es más evidente porque el Spirit se estuvo dirigíendose hacia atrás, arrastrando su rueda delantera derecha, la cual no gira.
El suelo brillante en el primer plano del centro es material blando en el cual el Spirit se insertó después de que las ruedas de ese lado cortan una capa superior mas oscura. La composición de las diferentes capas del suelo en el sitio se convirtió en el objeto de intensa investigación por las herramientas del brazo robótico del Spirit.
En las últimas semanas, los ingenieros han estado utilizando vehículos de prueba en la Tierra para simular la extracción del Spirit atrapado en la arena. Mientras que los síntomas similares a la amnesia en los últimos días podría retrasar el inicio de las maniobras planeadas para el Spirit orientadas hacia su extracción, el equipo del Rover Explorador de Marte sigue estando optimista. "Si ellos son intermitentes y poco frecuentes, que son una molestia que nos hace retroceder un día o dos cuando se producen. Si la condición se vuelve persistente o frecuente, tendremos que ir a una estrategia alternativa que las evite dependiendo de la memoria flash" dijo el Gerente del Proyecto John Callas del Laboratorio de Propulsión a Chorro de la NASA.
En estos eventos de amenesia, el Spirit falla en grabar la información de las actividades del día en la memoria del computador- memoria "flash" no volatil que guarda la información cuando el rover se apaga para sus periodos de conservación de energía.
El Spirit ha trabajado en Marte por más de 69 meses en lo que fue planeado originalmente como una misión de tres meses.
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