colorful PHOTOS

greece

HISTORY TIME Άλωση της Κωνσταντινούπολης

Madonna 'Vogue': Live at Paris Olympia 2012 OFFICIAL HD VIDEO

Vitamin A Swimwear Show at Miami Swim Fashion Week Summer 2013 ft Bikini...

Ford Raptor vs Ram Runner! - Head 2 Head Episode 14

Disc Ch The 9 11 Tapes Chaos in the Sky.720p

Where we you on 9/11?
Ask just about anybody, and they can tell you exactly where they were when the twin towers fell. For most, that's when the tragedy started to unfold. But the truth is the day's events began long before the first plane hit and continued long after.

For the first time, you'll hear the stories of real Americans who were at the heart of what happened on September 11, 2001. You'll hear actual recordings from air traffic controllers as they watched the first plane fly into the World Trade Center. Listen to audio recordings taken from flight UA93 before it crashed into a Pennsylvania field. See how defense teams raced to send fighter jets to intercept any incoming planes to the pentagon, but unfortunately arrived too late.

To get a sneak peek of the audio featured in this special, check out our video clips.
These recordings are incredibly powerful stories released for the first time that will help us all understand 9/11 in a whole new way.

Conteo Regresivo UFC 150: Henderson vs Edgar

Red Bull X-Fighters Munich Wrap

Speed Flying from the Mont Blanc with beautiful Mountain Scenerie

Enjoy the magnific footages from the speed riding of Mont Blanc, French Alps. 

Mont Blanc meaning -White Mountain-, is the highest mountain in the Alps. It rises 4,810m above sea level and is ranked 11th in the world in topographic prominence.

(Film Banff Mountain Film Festival World Tour)

Clearing the Smoke The Science of Cannabis 720p HD

learing the Smoke, reveals how cannabis acts on the brain and in the body to treat nausea, pain, epilepsy and potentially even cancer.
Extensive interviews with patients, doctors, researchers and skeptics detail the promises and the limitations of medicinal cannabis. Even though the video has an American perspective, marijuana use is illegal throughout many countries of the world for reasons that are not clear.
This video is important because it mainly investigates the scientific basis underlying the medical benefits of marijuana use instead of focusing on the social, political and legal hysteria that have been attached to it.

Plan B iLL Manors LIVE 2012 OFFICIAL HD Director's Cut - Full Show

Perseid Meteor Shower Peaks This Weekend: What You May See

by Joe Rao, SPACE.com Skywatching Columnist

Date: 10 August 2012 Time: 06:00 AM ET

FOLLOW US

SHARE

NASA astronaut Ron Garan took this photograph during the Perseid meteor shower on Aug. 13, 2011 from the International Space Station. CREDIT: NASA/Ron Garan (@Astro_Ron)  View full size image

This is the weekend of the peak of the annual Perseid meteor shower and most meteor forecasts predict the annual "shooting star" display will be at its best during the overnight hours of late Saturday (Aug. 11) into the early Sunday.

The Perseid meteor shower occurs each year in late July and early August when the Earth passes through the dusty remains of the comet Swift-Tuttle. In the night sky, the meteor shower appears to radiate out of the constellation Perseus, hence, its name: Perseid meteor shower.

French astronomer, Jérémie Vaubaillon of the The Institut de Mecanique Celeste et de Calcul des Ephemerides (IMCCE) has generated a plot of Earth’s passage through this year’s Perseid meteor swarm. Itshows that our planet will be passing through the greatest concentration of dusty material between approximately 0400 hours and 1300 hours UT on Aug. 11.

This is perfect timing for North America, as it means that the best viewing for the meteor shower will come during the predawn hours on Sunday. [Spectacular Perseid Meteor Shower Photos]

Seeing the Perseids

Over the years I’ve grown accustomed to receiving e-mails from SPACE.com readers who said that they were disappointed with how the Perseid meteor shower performed for them. After all, didn’t most online websites and the mainstream media promise that at their peak the Perseids would produce up to 100 meteors per hour? In most cases, people tend to see far fewer numbers. So why is that?

The number of meteors that you will see will depend on two factors: the time of night observed and sky conditions. An experienced observer in a perfectly clear and dark sky (one in which you can see the faintest stars visible to the unaided eye) with the radiant directly overhead, might theoretically see as many as 100 Perseids per hour. This oft-advertised number is called the shower’s Zenithal Hourly Rate or ZHR.

Such ideal conditions, however, rarely occur in reality.

This NASA sky map shows the location in the northern sky where the Perseid meteor shower will appear to radiate from in 2012. The Perseid meteor shower peaks every August and appears to fly out of the constellation Perseus.
CREDIT: NASA/JPL

View full size image

First, let’s take into account the altitude of Perseid radiant (where the meteors will appear to dart from).  During the evening hours, the radiant in the Perseus constellation will start off low in the east-northeast sky, but gradually it will climb higher during the night. As a result, the number meteors will correspondingly increase. [Take the Meteor Shower Quiz]

In the table included with this guide, the altitude of the radiant at a particular time (for viewers at latitude 40 degrees north) is given, along with the corrected percentage amount that you’re likely to see.Based on the table, after about 2:30 a.m. you should be seeing at least 80 percent of the predicted ZHR.  But there’s another, more important factor to also take into account.

This chart depicts the position (in degrees above the horizon) that the Perseid meteor shower radiant will appear in the northeastern sky in August 2012. Your closed fist held out at arm's length covers 10 degrees of the night sky.
CREDIT: Joe Rao

View full size image

Near city lights? Expect fewer meteors

That other factor is light pollution. Unfortunately, very few of us are blessed with perfectly dark, pristine skies. One way to judge how dark your skies are would be to check out the bowl of the Little Dipper. 

The brightest star in the bowl is Kochab, which is a second magnitude star on the scale used by astronomers to denote brightness (higher numbers mean dimmer objects, negative number objects are extra bright). The other three stars are 3rd, 4th and 5th magnitude. 

The Perseid meteors appear to radiate from a point between the constellations Perseus and Cassiopeia, in the northeastern section of the sky. The 2012 Perseid meteor shower display peaks on Aug. 12.
CREDIT: Starry Night Software

View full size image

If you can easily see all four stars in the bowl, you probably have a limiting magnitude of 6, which means you’ll see about 63 percent of the ZHR. If you can barely see the faintest star in the bowl, you have a 5th magnitude sky, so you’ll only be seeing about 25 percent of the ZHR. If only 3 stars are visible, you only have a fourth magnitude sky and you’ll probably see only about 10 percent of the ZHR.

For example, let's say you are out looking for the Perseid meteor shower at 4 a.m. on Aug. 12. You can just about make out all four stars in the bowl of the Little Dipper, so you have a 5th magnitude sky; that’s not too bad. 

The Perseid radiant stands 60 degrees above the horizon, so you’re expecting to see 100 Perseids per hour, but here’s the reality check: 90 percent of 100 is 90 meteors an hour. But then, factoring in sky conditions based on light pollution, 25 percent of 90 give you just 23.

Many of the Perseids tend to be quite bright, so probably 23 per hour for these specific conditions is a bit conservative, but unless you can get yourself to a truly dark and remote location, your hourly rates are likely to be closer to 23 than 100.

Meteor Shower Mania: How Well Do You Know 'Shooting...

Meteor showers can be awesome night sky sights, but how well do you know your shooting star facts? Find out here and good luck!

0 of 10 questions complete

Great balls of fire!

During your meteor watch you might catch sight of a few outstandingly bright meteors. You may even see a fireball that leaves a long enduring vapor trail lasting for many seconds, or a bolide, which is an exploding meteor whose flight across the sky ends with a silent, strobe-like flash capable of casting a shadow.

Just seeing one of these kinds of meteors can make your whole night worthwhile. 

So remember this if you’re out late Saturday night or early Sunday morning looking for Perseids: It’s quality, not necessarily quantity.

Editor's note: If you snap an amazing photo of the 2012 Perseid meteor shower that you'd like to share for a possible story or image gallery, send images and comments (including name and location) to managing editor Tariq Malik at tmalik@space.com.

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.

ΟΙ ΟΜΟΡΦΙΕΣ ΤΟΥ ΠΛΑΝΗΤΗ ΜΑΣ.

2013 Bridalwear by International Flavours | White Gallery Bridal Collect...

LONDON - White Gallery Bridal Collections in London presents a preview of the International Flavours 2013 collection which includes crafted mermaid gowns and sleek dresses by Lusan Mandongus/Annasul Y, unique ball gowns from Elizabeth Stuart, sleek gowns and puffy shoulders from Sanyukta Shrestha, embellished and pleated skirts from Kisui, unique headwear from Victoria Kyriakides, fringed gowns from Yolan Cris, and satin and silk refinery from Victorio & Lucchino Novias/Raimon Bundo. 

Hair by Joseph Koniak and makeup by Benefit

Transformed X-48C Makes Successful First Flight

Transformed X-48C Makes Successful First Flight

 

 

The remotely operated X-48C Blended Wing Body aircraft lifts off Rogers Dry Lake at Edwards Air Force Base, Calif., on its first test flight Aug. 7. The sub-scale technology demonstrator, modified from the prior X-48B configuration, is entering a new flight test phase in a partnership between NASA and The Boeing Company's Phantom Works research and technology division. (NASA / Carla Thomas) › View Larger Image

EDWARDS AFB, Calif. - The remotely piloted X-48C aircraft successfully flew for the first time on Aug. 7, 2012, at Edwards Air Force Base in California's Mojave Desert.

The aircraft, designed by the Boeing Co. and built by Cranfield Aerospace Ltd. of the United Kingdom, is flying again in partnership with NASA. The new X-48C model, which was formerly the X-48B Blended Wing Body aircraft, was modified to evaluate the low-speed stability and control of a low-noise version of a notional, future Hybrid Wing Body (HWB) aircraft design. The HWB design stems from concept studies being conducted by NASA's Environmentally Responsible Aviation project of future potential aircraft designs 20 years from now.

"We are thrilled to get back in the air to start collecting data in this low-noise configuration," said Heather Maliska, X-48C project manager at NASA's Dryden Flight Research Center. "Our dedicated team has worked hard to get the X-48C off the ground for this first flight and we are excited to learn about the stability and control characteristics of this low-noise configuration of the Blended Wing Body."

Primary changes to the C-model from the B-model, which flew 92 flights at NASA Dryden between 2007 and 2010, were geared to transforming it to an airframe noise-shielding configuration. External modifications included relocating the wingtip winglets inboard next to the engines, effectively turning them into twin tails. The aft deck of the aircraft was also extended about two feet to the rear. Finally, the project team replaced the X-48B’s three 50-pound-thrust jet engines with two 89-pound-thrust engines.

Because handling qualities of the X-48C will be different than those of the X-48B, the project team developed flight control system software modifications, including flight control limiters to keep the airplane flying within a safe flight envelope. This will enable a stronger and safer prototype flight control system suitable for future full-scale commercial hybrid or blended wing aircraft.

"We are very pleased to begin flight tests of the X-48C," said Mike Kisska, Boeing X-48C project manager. "Working with NASA, we’ve successfully passed another milestone in our work to explore and validate the aerodynamic characteristics and efficiencies of the blended wing body concept."

Additionally, the upcoming flight experiments with the X-48C will help researchers further develop methods to validate the design’s aerodynamics and control laws, including a goal of reducing aerodynamic drag through engine yaw control tests.

During the planned second block of flight testing this fall, NASA will test engine yaw control software incorporated in the X-48C’s flight computer. This research will use asymmetric engine thrust to create yaw, or nose left or right movements, for trim and for relatively slow maneuvers.

NASA's Aeronautics Research Mission Directorate and Boeing are funding the X-48 technology demonstration research effort, which supports NASA’s goals of reduced fuel burn, emissions and noise.

The X-48C retains most dimensions of the B-model, with a wingspan just longer than 20 feet, and a weight of about 500 pounds. The aircraft has an estimated top speed of about 140 mph, and a maximum altitude of 10,000 feet.

The Air Force Research Laboratory, Dayton, Ohio, is also a member of the project team.

For more information about NASA's Aeronautics Research Mission Directorate, visit:

http://www.aeronautics.nasa.gov

For more about NASA Dryden Flight Research Center, visit:

http://www.nasa.gov/centers/dryden

 

- end -

2012 Tecate Score Baja 500 by Cactus Films

Rider of the Year II Preview HQ

Getaways Bora 1080 Full HD

Inside Syria's War

This powerful exclusive is the first film to access the Free Syrian Army's secret labyrinth of caves and also holds a rare interview with the FSA leader. A fascinating insight to how the battle for Syria is being fought.

"Please don't film!" one fighter says, as two rebels argue in the pitch black over the presence of a journalist. In this increasingly violent war the rebels have been using their local knowledge to great advantage. And these 3,000 year old caves are of huge strategic importance. "The army besieged us many times and we always slipped through." But local knowledge will only go so far and the rebels are hard pressed to counter the might of the Syrian army with limited resources. As one failed test run of a home-made mortar shows, they don't have much to work with. They are disheartened by months of fighting without help. "America and Europe hide behind the Russian veto. They lie to us." Even the head of the Free Syrian Army, Colonel Riad al-Assad, is unable to help. As rebel groups come to him for guidance he can only encourage coordination. When asked about the suicide bomb that killed the minister of defence he says, "This is an integral part of the revolutionary action. It could break the regime's back." As things get increasingly desperate, anything that hastens the end of the bloodshed in Syria will form a part of their strategy. 

Female Fighters of Kurdistan - Iraq

Fighting to carve a homeland in a region not known for its women's rights, the female guerrillas of the Kurdish Liberation Movement have quite a challenge ahead. Can they really equal their male comrades?
"It is not right to consider a woman fragile", argues one female fighter. For the armed women of PJAK - a rebel group fighting for Kurdish independence in the mountains of northern Iraq, Turkey and Iran - their mission is to defend women from the "persecution" of sharia law, whilst also creating a Kurdish homeland. Their male comrades support their vision of an emancipated Kurdish nation; "women are much better than men at leadership and organisation", one PKK fighter insists. It isn't an easy path: "You are not allowed to be a guerrilla and have a family. You will be distracted". Yet from their remote mountain outpost this ragtag group are determined that their sacrifices will lead to "equality and equity".
VBS.tv

Madonna Live At The Paris Olympia 2012 HD Directors Cut - Full Show

2013 Ferrari F12 Berlinetta: The Grandest Tourer

this episode of Ignition, Carlos Lago heads to Italy to test out the fastest and most powerful production Ferrari ever made, the 2013 F12 Berlinetta. The trip begins with spirited hot laps around the legendary Fiorano test circuit, then moves to the winding road to see how this V-12 beast behaves as a grand tourer.

mars time

Curiosity Takes Us Back to Mars

Posted on Aug 06, 2012 01:51:53 AM | Administrator Charles Bolden | 0 Comments    |

NASA is back on Mars – and getting ready for the next mission to the Red Planet! After an astounding 154 million mile journey and a harrowing landing that demonstrated cutting-edge technology, Curiosity, the largest rover ever sent to another planet, is in place and ready to work. This robotic laboratory will seek answers to one of humanity’s oldest questions as it investigates whether conditions have favored development of microbial life on the Red Planet. The mission is a critical planetary science mission -- and a precursor to sending humans to the Red Planet in the 2030’s, a goal set forth by President Obama. It’s another great leadership moment for our nation and a sign of the continued strength of NASA’s many programs in science, aeronautics and human spaceflight. It’s also important to remember that the $2.5 billion investment made in this project was not spent on Mars, but right here on Earth, supporting more than 7,000 jobs in at least 31 states. With the retirement of the Shuttle program after its final flight in July 2011, some have suggested that NASA’s leadership in the exploration of space, including our extraordinary successes on Mars, was coming to an end. Nothing could be further from the truth. The Curiosity mission is only the latest in a long list of extraordinary NASA missions that established the United States as the undisputed world leader, and it will help guarantee that remains the case for many years to come. When our Orion deep space crew vehicle takes its first test flight in 2014, it will travel farther into space than any spacecraft designed for humans has flown in the 40 years since our astronauts returned from the moon. In 2017, NASA’s Space Launch System (SLS), a heavy-lift rocket that will provide an entirely new capability for human exploration beyond low Earth orbit, will launch Orion. We also reached a critically important milestone in May when SpaceX became the first private company to send a spacecraft -- the Dragon cargo capsule -- to the International Space Station and return it with cargo intact. This successful mission ushered in a new era in spaceflight -- and signaled a new way of doing business for NASA. And just a few days ago, we announced the next step in the Obama Administration’s aggressive plan to once again launch our astronauts from U.S. soil on spacecraft built by American companies. As part of our commitment to maintain American leadership in the exploration of Mars beyond the Curiosity mission, NASA will launch the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter next year. Earlier this year, I directed NASA’s science mission director, along with the head of human exploration, Chief Technologist, and Chief Scientist to develop a more integrated strategy to ensure that the next steps for Mars exploration will support the nation’s planetary science objectives as well as our human exploration goals. They are looking at many options, including another robotic mission to land on Mars in this decade. I am so proud of the NASA team that has made tonight’s challenging milestone possible. However, tomorrow we begin to plan for the next great challenge -- and start compiling incredible scientific data from Curiosity. For the past 50 years, NASA has specialized in doing the hard things. Thanks to the ingenuity of our teams across America and the world, we are poised for even greater success. For more information about Curiosity and NASA's missions to Mars, visit: http://www.nasa.gov/mars   The Mars Science Laboratory (MSL) team in the MSL Mission Support Area react after learning the the Curiosity rove has landed safely on Mars and images start coming in at the Jet Propulsion Laboratory on Mars, Sunday, Aug. 5, 2012 in Pasadena, Calif. The MSL Rover named Curiosity was designed to assess whether Mars ever had an environment able to support small life forms called microbes. Photo Credit: (NASA/Bill Ingalls)

Strength in Numbers Official Trailer

Strength in Numbers is a rally call to connect all mountain bikers, regardless of location or language or discipline. The film captures a true way of life, from the world's best pros to those who are just learning to love the sport. Shot over two years in some of mountain biking's most iconic locations, Anthill's signature style combines compelling stories with core action to create a shared experience that unites all riders. Come join us!

http://anthillfilms.com/strengthinnumbers

Africa - Into The Wild - VenTribe κενυα

Kurdish rebels storm Turkey border post

Kurdish rebels storm Turkey border post

Government combat helicopters deployed after rebels attack post in Kurdish southeast, killing at least 19 combatants.

At least 19 people have been killed in southeastern Turkey after a battle between soldiers and members of a Kurdish separatist group, the local provincial governor has said. Six soldiers, two government-paid village guards and 11 Kurdish rebels were killed in the fighting near the village of Gecimili in Hakkari province, Governor Orhan Alimoglu said on Sunday. The incident occurred near the Iraqi border early on Sunday, he said, adding that 15 soldiers had also been wounded. Local media reported that the rebels fired on the army outpost in Hakkari with rocket launchers just after midnight. The military sent in reinforcement following the raid, using attack helicopters to fire on the rebels' escape routes, state-run TRT television reported. The raid on the army post follows similar assaults in the Kurdish-dominated southeast that have prompted the army to launch an all-out offensive against Kurdistan Workers' Party (PKK) bases in the area. The Turkish ground-and-air operation, one of the biggest in years, was launched about two weeks ago to drive out the rebels in the town of Semdinli, also in Hakkari province. About 2,000 soldiers are involved in the offensive, private NTV television reported on Sunday. "A serious and strong operation is under way in Semdinli," Besir Atalay, the Turkish deputy prime minister, said last week. Fighting between the Turkish state and the PKK has claimed tens of thousands of lives since 1984, when the group first took up arms.

MARS! H AΠΟΣΤΟΛΗ!

Mars Science Laboratory (MSL, or Curiosity) is a Mars rover launched by NASA on November 26, 2011. It is currently en route to the planet, scheduled to land in Gale Crater at 05:31 UTC on August 6, 2012. Its objectives include searching for evidence of conditions favorable to life, studying the Martian climate, studying Martian geology, and collecting data for a future manned mission to Mars.

n Aug.04.12 , In MSL Picture of the Day by artemis | 0 Comments

In the above depicted scene, thrusters on the backshell of the spacecraft’s aeroshell are firing to adjust the orientation of the spacecraft during the guided entry manoeuvres

One set of instruments carried on the heat shield of the spacecraft’s entry vehicle serves specifically to gather data about the Martian atmosphere and performance of the heat shield for use in designing future systems for descending through planetary atmospheres: the Entry, Descent and Landing Instrument (MEDLI) Suite.F. McNeil Cheatwood is the principal investigator,NASA’s Langley Research Center, Hampton, Virginia.
Michael Wright is the Deputy principal investigator, NASA’s Ames Research Center, Moffett Field, California.

The MSL Entry, Descent and Landing Instrument (MEDLI) Suite consists of a set of sensors attached to the heat shield of the Mars Science Laboratory.
MEDLI will take measurements eight times per second during the period from about 10 minutes before the vehicle enters the top of the Martian atmosphere until after the parachute has opened, about four minutes after entry.

The measurements will be analyzed for information about atmospheric conditions and performance of the entry vehicle.
MEDLI was installed to learn for future landings on Mars. NASA’s Exploration Systems Mission Directorate (which has responsibility for planning human missions beyond Earth orbit) and Aeronautics Research Mission Directorate (which invests in fundamental research of atmospheric flight) have funded MEDLI.

The heating and stress on the heat shield will be the highest ever for an entry vehicle at Mars. This is due to the mass of the entry vehicle (2,431 kilograms, or 5,359 pounds after jettison of the spacecraft’s cruise stage), the diameter of its heat shield (4.5 meters, or 14.8 feet) and the speed at which the vehicle will enter the atmosphere (6.1 kilometers per second, or 13,645 miles per hour),

Experience gained with this mission will aid planning for future missions that could be even heavier and larger, such as would be necessary for a human mission to Mars.

Models of the Martian atmosphere, heating environments, vehicle aerodynamics, and heat-shield performance, among other factors, were employed in designing the Mars Science Laboratory entry vehicle.

Ofcourse we don’t know everything or precisely. To account for those uncertainties, the design incorporates large margins for success. However, that margin comes at a cost of additional mass. The goal of MEDLI is to better quantify these atmospheric entry characteristics and possibly reduce unnecessary mass on future Mars missions, by collecting data on the performance of the Mars Science Laboratory entry vehicle during its atmospheric entry and descent.

MEDLI consists of seven pressure sensors (Mars entry atmospheric data system sensor, or MEADS), seven plugs with multiple temperature sensors (Mars integrated sensor plug, or MISP) and a support electronics box.

Data from the entry vehicle’s inertial measurement unit, which senses changes in velocity and direction, will augment the MEDLI data. Each of the temperature-sensing plugs has thermocouples to measure temperatures at four different depths in the heat shield’s thermal protection tiles, plus a sensor to measure the rate at which heat shield material is removed due to atmospheric entry heating.

Analysis of data from the pressure sensors and inertial measurement unit will provide an altitude profile of atmospheric density and winds, plus information about pressure distribution on the heat shield surface, orientation of the entry vehicle and velocity.

Data from the temperature sensors will be used to evaluate peak heating, distribution of heating over the heat shield, turbulence in the flow of gas along the entry vehicle’s surface, and in-depth performance of the heat shield material.

This sounds all as if landing on Mars is 1+1=2. It will not surprise you to learn that this is not the case. The span of time from atmospheric entry until touchdown is not predetermined. That timespan hinges on atmospheric density (more density gives more drag, means faster slow down of the spacecraft. How long you have for touchdown obviously also depends on the elevation of the Mars terrain you are going to land on. When you land on a high plateau you will meet the ground sooner than when you plan to land on a deep vallis.

As it is impossible to send commands to the landing spacecraft while it is landing (due to commands not being able to fly to space faster than the speed of light and the fact that Mars is at best over 3 minutes away at that speed of light) the complete landing sequence has to be preprogrammed, but also be highly adaptable to the circumstances of the landing

The Mars Science Laboratory has been fitted with a guided entry technique which enables the spacecraft to respond and adapt to the atmospheric conditions it encounters more effectively than any previous Mars mission. The span between the moment the spacecraft passes the entry interface point and a successful touchdown in the target area of Gale Crater could be as short as about 380 seconds or as long as about 460 seconds.

Times for the opening of the parachute could vary by 10 to 20 seconds for a successful landing. 
The largest variable during EDL is the length of time the spacecraft spends on the opened parachute. Curiosity could be hanging below a fully inflated chute as briefly as about 55 seconds or as long as about 170 seconds.

Times given in the EDL description below (as well as on the image of the EDL sequence) are given for one typical landing with a touchdown 416 seconds after entry.

The intense period called the entry, descent and landing (EDL) phase of the mission begins when the spacecraft reaches the top of the Martian atmosphere, traveling at about 13,200 miles per hour (5,900 meters per second).

EDL ends about seven minutes later with the rover stationary on the surface. From just before jettison of the cruise stage, 10 minutes before entry, to the cutting of the sky crane bridle, the spacecraft goes through six different vehicle configurations and fires 76 pyrotechnic devices, such as releases for parts to be separated or deployed.

The top of Mars’ atmosphere is a gradual transition to interplanetary space, not a sharp boundary. The atmospheric entry interface point — the navigators’ aim point during the flight to Mars — is set at 3,522.2 kilometers (2,188.6 miles) from the center of Mars.

That altitude is 131.1 kilometers (81.46 miles) above the ground elevation of the landing site at Gale Crater, though the entry point is not directly above the landing site. While descending from that altitude to the surface, the spacecraft will also be travelling eastward relative to the Mars surface, covering a ground-track distance of about 630 kilometers (about 390 miles) between the atmospheric entry point and the touchdown target.

Ten minutes before the spacecraft enters the atmosphere, it sheds the cruise stage. The Mars Science Laboratory Entry, Descent and Landing Instrument (MEDLI) Suite begins taking measurements.

A minute after cruise stage separation, nine minutes before entry, small thrusters on the back shell halt the two-rotation-per-minute spin that the spacecraft maintained during cruise and approach phases. Then, the same thrusters on the back shell orient the spacecraft so the heat shield faces forward, a maneuver called “turn to entry.”

After the turn to entry, the back shell jettisons two solidtungsten weights, called the “cruise balance mass devices.” Ejecting these devices, which weigh about 75 kilograms (165 pounds) each, shifts the center of mass of the spacecraft. During the cruise and approach phases, the center of mass is on the axis of the spacecraft’s stabilizing spin.

Offsetting the center of mass for the period during which the spacecraft experiences dynamic pressure from interaction with the atmosphere gives the Mars Science Laboratory the ability to generate lift, essentially allowing it to fly through the atmosphere. The ability to generate lift during entry increases this mission’s capability to land a heavier robot, compared to previous Mars surface missions.

The spacecraft also manipulates that lift, using a technique called “guided entry,” to steer out unpredictable variations in the density of the Mars atmosphere, improving the precision of landing on target.

During guided entry, small thrusters on the back shell can adjust the angle and direction of lift, enabling the spacecraft to control how far downrange it is flying. The spacecraft also performs “S” turns, called bank reversals, to control how far to the left or right of the target it is flying. These maneuvers allow the spacecraft to correct position errors that may be caused by atmosphere effects, such as wind, or by spacecraft modelling errors. These guided entry maneuvers are performed autonomously, controlled by the spacecraft’s computer in response to information that a gyroscope-containing inertial measurement unit provides about deceleration and direction, indirect indicators of atmospheric density and winds.

During EDL, more than nine-tenths of the deceleration before landing results from friction with the Mars atmosphere before the parachute opens. Peak heating occurs about 75 seconds after atmospheric entry, when the temperature at the external surface of the heat shield will reach about 3,800 degrees Fahrenheit (about 2,100 degrees Celsius). Peak deceleration occurs about 10 seconds later. Deceleration could reach 15 g, but a peak in the range of 10 g to 11 g is more likely.

After the spacecraft finishes its guided entry maneuvers, a few seconds before the parachute is deployed, the back shell jettisons another set of tungsten weights to shift the center of mass back to the axis of symmetry. This set of six weights, the “entry balance mass devices,” each has a mass of about 25 kilograms (55 pounds). Shedding them re-balances the spacecraft for the parachute portion of the descent.

The parachute, which is 51 feet (almost 16 meters) in diameter, deploys about 254 seconds after entry, at an altitude of about 7 miles (11 kilometers) and a velocity of about 900 miles per hour (about 405 meters per second).

About 24 more seconds after parachute deployment, the heat shield separates and drops away when the spacecraft is at an altitude of about 8 kilometers (5 miles) and traveling at a velocity of about 125 meters per second (280 miles per hour).

As the heat shield separates, the Mars Descent Imager begins recording video, looking in the direction the spacecraft is flying. The imager records continuously from then through the landing. The rover, with its descent-stage “rocket backpack,” is still attached to the back shell on the parachute.

The terminal descent sensor, a radar system mounted on the descent stage, begins collecting data about velocity and altitude.

The back shell, with parachute attached, separates from the descent stage and rover about 85 seconds after heat shield separation. At this point, the spacecraft is about 1,6 kilometers (1 mile) above the ground and rushing toward it at about 80 meters per second (about 180 miles per hour).

All eight throttleable retrorockets on the descent stage, called Mars landing engines, begin firing for the powered descent phase.

After the engines have decelerated the descent to about 0.75 meters per second  (1.7 miles per hour), the descent stage maintains that velocity until rover touchdown.

Four of the eight engines shut off just before nylon cords begin to spool out to lower the rover from the descent stage in the “sky crane” manoeuvre. The rover separates its hard attachment to the descent stage, though still attached by the sky crane bridle and a data “umbilical cord,” at an altitude of about 20 meters (about 66 feet), with about 12 seconds to go before touchdown.

The rover’s wheels and suspension system, which double as the landing gear, pop into place just before touchdown. The bridle is fully spooled out as the spacecraft continues to descend, so touchdown occurs at the descent speed of about 0.75 meters per second (about 1.7 miles per hour).

When the spacecraft senses touchdown, the connecting cords are severed and the descent stage flies out of the way, coming to the surface at least 150 meters (492 feet) from the rover’s position, probably more than double that distance.

Soon after landing, the rover’s computer switches from entry, descent and landing mode to surface mode.

This initiates autonomous activities for the first Martian day on the surface of Mars, Sol 0. The time of day at the landing site is mid afternoon — about 3 p.m. local mean solar time at Gale Crater.

Curiosity’s Seven Minutes of Terror

Author: artemis

Visit Authors Website  |  All Articles From This Author

Cia Maritima Swimwear Summer 2013: Bikini Models at Miami Swim Fashion W...

ΤΙ ΜΑΓΙΟ ΘΑ ΦΟΡΕΣΕΤΕ ΦΕΤΟΣ?