Countdown to Orion's lift-off: Spacecraft to embark on historic test flight that will usher in a new age of space exploration
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The countdown has begun for the maiden launch of the Orion spacecraft which could herald the dawn of a new era in space exploration.
Orion was set to launch at 12.05 GMT (07:05 local time) today, but a boat has now strayed into the restricted waters around the launch sight, which has delayed the launch by around 10 minutes.
Orion will be catapulted around the Earth twice in a 4.5 hour journey, before re-entering the atmosphere at 20,000 mph (32,000 kph).
Today's mission is unmanned, but in the future Nasa hopes to use Orion to put astronauts back on the moon by 2020 and take them to Mars in the 2030s.
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The countdown begins: At 12.05 GMT (07:05 local time) today, Orion will be catapulted around the Earth twice in a historic 4.5 hour test flight
This is the first mission since the Apollo moon landings to take a spacecraft built for manned flight into deep space beyond the limit of orbiting satellites.
According to Nasa, the roads leading into Kennedy Space Centre in Florida have been packed since dawn.
The atmosphere has been described as reminiscent of the shuttle-flying days. 'Go Orion!!' is splashed across a hotel billboard in nearby Cocoa Beach.
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Orion is being developed alongside the world's most powerful rocket, the Space Launch System (SLS), which is due to unveiled in 2017 or 2018.
Together, they will allow Nasa to send humans into deep space to destinations such as Mars.
For today's launch, Orion has been strapped to Delta IV-Heavy rocket – currently the largest launch system in the world. Three RS-68 engines will produce about two million pounds of thrust at lift-off.
Live: Nasa's Orion spacecraft launch
Today's mission is unmanned, but in the future Nasa hopes to use Orion to put astronauts back on the moon by 2020 and take them to Mars
The launch should give engineers the opportunity to check the performance of Orion's critical heat shield, which is likely to experience temperatures in excess of 2,000C (4,000F)
At the earliest Orion might carry passengers is 2021; asteroids are on the space agency's radar sometime in the 2020s and Mars, the grand prize, in the 2030s
Five and a half minutes after launch, at an altitude of around 200 miles (320km), fuel will have run out on both the Delta IV's main and booster engines.
A couple of seconds later, the entire bottom end – or the 'first stages' of the rocket - will detach, while the second stage engine will ignite to take Orion to a higher orbit.
The upper stage's protective fairings will then be jettisoned, along with the launch abort system, which is designed to protect the astronauts in the cause of an emergency during launch.
After two hours, and one orbit of Earth, the second-stage rocket will be ignited again, moving Orion up to an altitude of 3,600 miles (5,800 km).
This is 15 times the distance to the ISS and will cause Orion to travel through the high-radiation Van Allen Belts.
At three hours after lift-off, Orion will hit its peak altitude and then slowly start its descent back to Earth
The flight program has been loaded into Orion's computers well in advance, allowing the spacecraft to fly essentially on autopilot.
It should give engineers the opportunity to check the performance of Orion's critical heat shield, which is likely to experience temperatures in excess of 2,000ºC (4,000°F).
Its re-entry speed into the atmosphere will be close to 20,000mph (30,000km/h) – similar to speed of a capsule coming back from the moon.
The dry run, if all goes well, will end with a Pacific splashdown off Mexico's Baja coast and Navy ships will recover the capsule for future use.
WHAT ARE THE KEY FLIGHT MILESTONES DURING ORION'S MAIDEN JOURNEY AROUND EARTH?
Down to Earth: Orion is expected to have a rapid re-entry speed into the atmosphere close to 30,000km/h (20,000mph), according Nasa
One minute, 25 seconds after liftoff, Orion goes supersonic.
Four minutes after liftoff, two of the Delta 4's three liquid-fueled boosters are jettisoned.
Five minutes, 30 seconds, the last booster burns out and separates from the upper-stage engine.
Six minutes, 15 seconds, with the second-stage burning, three protective panels separate from Orion's mock-up service module. Five seconds later, the launch escape system is jettisoned.
Seventeen minutes, the second-stage engine shuts down, leaving Orion in its initial orbit 115- by 552 miles (185- by 888 km) above Earth.
Three hours, after a second burn of the upper-stage engine, Orion passes through intense radiation in the Van Allen Belts and reaches its peak altitude of 3,600 miles (5,800 km).
Three hours, 23 minutes, Orion separates from its service module and the Delta upper stage and prepares to return to Earth.
Three hours, 57 minutes, Orion fires its steering thrusters to position itself for atmospheric re-entry.
Four hours, 13 minutes, Orion, trave;ling at 20,000 mph (32,000 km/h) reaches upper limits of Earth's atmosphere.
Four hours, 15 minutes, Orion experiences peak heating of about 4,000 degrees Fahrenheit (2,200 Celsius).
Four hours, 19 minutes, parachutes begin deploying to slow Orion's descent.
Four hours, 23 minutes, Orion lands in the Pacific Ocean, 600 miles (965 km) off the coast of Baja California. Recovery teams will retrieve the capsule and take it to San Diego, California.
Five and a half minutes after launch, at an altitude of around 200 miles (320km), fuel will have run out on both the Delta IV's main and booster engines. A couple of seconds later, the entire bottom end – or the 'first stages' of the rocket - will detach, while the second stage engine will ignite to take Orion to a higher orbit
Flight sequence: Five and a half minutes after launch, at an altitude of around 200 miles (320km), fuel will have run out on both the Delta IV's main and booster engines
The spacecraft is rigged with 1,200 sensors to gauge everything from heat to vibration to radiation.
Programme manager Mark Geyer said: 'We're going to test the riskiest parts of the mission. Ascent, entry and thinks like fairing separations, Launch Abort System jettison, the parachute, plus the navigation and guidance - all those things are going to be tested.
'Plus, we'll fly into deep space and test the radiation effects on those systems.'
A crucial test will come when Orion flies through the Van Allen belts, which are two layers of charged particles orbiting around Earth.
'The ISS would not have to deal with radiation but we will, and so will every vehicle that goes to the moon,' Geyer told the BBC.
'That's a big issue for the computers. These processors that are now so small - they're great for speed but they're more susceptible to radiation.
'That's something we have to design for and see how it all behaves.'
Another key test will be on the heat shield on Orion's base, designed to protect the craft from the searing temperatures of atmospheric re-entry, is 16.5ft (five metres) across and is the biggest, most advanced of its kind ever made.
On this flight, Orion will reach close to 4,000 degrees, not quite the 5,000 degrees that would be generated from a moon mission, but close enough for a shakedown.
That's why Orion will aim for a 3,600 miles (5,800 km) peak altitude to pick up enough speed to come back fast and hot.
Even though the Orion bristles with the latest technology, it bears a strong resemblance to the Apollo command module that carried Neil Armstrong to the moon in 1969.
Test flight: Orion will make two big laps around Earth before re-entering the atmosphere at 20,000 mph (32,200 km/h). Pictured is an artist's impression of the Orion craft in orbit
Even though the Orion bristles with the latest technology, it bears a strong resemblance to the Apollo command module that carried Neil Armstrong to the moon in 1969
Poised: Orion awaits launch in Florida. This the first attempt to send a spacecraft capable of carrying humans beyond a couple hundred miles of Earth since the Apollo moon mission
But at 11ft (3.6 metres) tall with a 16.5ft (5 metres) base, Orion is much larger than the old-time Apollo capsules, and is designed to carry four astronauts rather than three.
The earliest Orion might carry passengers is 2021; asteroids are on the space agency's radar sometime in the 2020s and Mars, the grand prize, in the 2030s.
'We're approaching this as pioneers,' said William Hill of Nasa's exploration systems development office.
'We're going out to stay eventually. ... It's many, many decades away, but that's our intent.'
However, Nasa has yet to develop the technology to carry out manned surface operations on Mars.
But no one at Nasa is pleased with such a poky pace. At best, it will be seven years before astronauts fly Orion - anywhere.
On track: In the months leading up to launch, Orion has been rigorously tested as engineers prepare it for a journey beyond low Earth orbit
By comparison, it took eight years from the time President John Kennedy announced his intentions of landing a man on the moon - before John Glenn had even rocketed into orbit - to Neil Armstrong and Buzz Aldrin's lunar bootprints in 1969.
Given the present budget situation, 'it is what it is,' said Kennedy Space Center's director Robert Cabana, a former astronaut. And the presidential election ahead could bring further delays and uncertainties.
Lockheed Martin is handling the £236 million ($370 million) test flight, and Nasa will be overseeing its operation.
Nasa's last trip beyond low-Earth orbit in a vessel built for people was Apollo 17 in December 1972.
'This is just the first of what will be a long line of exploration missions beyond low Earth orbit,' said Bill Hill, deputy associate administrator for Exploration Systems Development.
'In a few years we will be sending our astronauts to destinations humans have never experienced. It's thrilling to be a part of the journey now, at the beginning.'
'This is just the first of what will be a long line of exploration missions beyond low Earth orbit,' said Bill Hill, deputy associate administrator for Exploration Systems Development. 'In a few years we will be sending our astronauts to destinations humans have never experienced'
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