'Textbook' flight for Orion mission
A first step in the human journey to Mars has been taken with the Orion spacecraft completing a "textbook" maiden flight.
The four-hour, 24-minute, unmanned mission was the first since the Apollo Moon landings half a century ago to send a spacecraft built for astronauts into deep space.
Orion travelled more than 3,600 miles (5,794km) from Earth - 15 times the distance to the International Space Station.
After circling the Earth twice and passing through potentially destructive belts of radiation, the 16.5ft (5m) wide craft re-entered the atmosphere at 20,000mph and splashed down into the Pacific ocean.
Re-entry was a critical time for the mission, as temperatures on the spacecraft's heat shield rose to around 2,000C - twice as hot as molten lava.
But the entire mission went virtually without a hitch, the only problem occurring after splashdown when two of Orion's five airbags failed to inflate properly.
This did not affect the attitude or stability of the capsule in the water, however.
Mission commentator Rob Navias described Orion's journey as "textbook" and and "the most perfect flight you could ever imagine".
Orion bears a striking resemblance to the Apollo module which took Neil Armstrong to the Moon in 1969 but is larger and designed to carry a crew of four instead of three.
The American space agency Nasa hopes to see its spacecraft transport astronauts to Mars in the 2030s.
Prior to that, trips to the Moon and an asteroid are planned. But an original proposal to land a crew on the surface of the Moon for the first time in 42 years has been shelved, mainly because of cost.
Several major "milestones" - risky phases of the test flight mission - were passed by Orion with flying colours.
They included the launch itself from Cape Canaveral in Florida, rocket stage separations, re-entry, and parachute deployment.
Another critical test came as Orion flew through the Van Allen belts - bands of fast-moving high-energy particles trapped by the Earth's magnetic field.
Scientists wanted to see how well the spacecraft's protected computers could withstand radiation levels high enough to disable common devices such as mobile phones.
Orion was blasted into orbit by a triple-booster Delta IV rocket, the largest currently in service in the US.
A video camera on board the craft streamed stunning pictures of the two side boosters falling away and the curved edge of the Earth.
As it re-entered the Earth's atmosphere, a fifth of Orion's heat shield burned away. Two small holes had deliberately been drilled in two of the heat shield tiles to simulate micrometeorite damage, but as predicted this caused no problems.
On the way down a camera looking out of one of Orion's windows captured more dramatic pictures of the blue Earth spotted with clouds.
Eleven parachutes were deployed to slow the spacecraft down until it was travelling at just 20mph when it made a "bullseye" splashdown off the coast of Baja California, Mexico.
Astronaut Rex Waldheim, who flew the last space shuttle mission in 2011 and is helping to design Orion's interior systems, told Nasa TV: "The ultimate destination is Mars. Everybody wants to go to Mars.
"It's important to go there and establish a presence on another planet so we become a multi-planetary species."
He added: "Now we've turned the corner and Orion is flying, and it's a very exciting time."
The next Orion flight, Exploration Mission One (EM-1), will involve an unmanned trip around the Moon in 2017 or 2018.
For this mission, the spacecraft will be launched by Nasa's new Space Launch System (SLS) rocket which is now in final stages of development.
The SLS will be the most powerful rocket ever built and capable of producing 20% more thrust than the mighty Saturn V that sent astronauts to the moon.
The future of Orion becomes more uncertain after EM-1, but could embrace President Barack Obama's goal to fly a crewed spacecraft to an asteroid by the mid-2020s.
Plans for Exploration Mission Two (EM-2) in around 2021 involve an Orion crew spending three to four days in lunar orbit before returning home.
Depending on what is finally decided, they may also rendezvous with a small asteroid previously "captured" and placed in orbit around the Moon by a robot tug.
EM-2 will pave the way for further missions, possibly including a much longer trip to an asteroid, culminating in a manned space voyage to Mars.
Orion's launch had been postponed from yesterday when a rogue boat, gusting winds and sticky fuel valves forced controllers to scrub the take-off.
"There's your new spacecraft, America," Mission Control commentator Rob Navias said as the Orion capsule neared the water 270 miles (435 kilometres) off Mexico's Baja peninsula.
He said the journey was "the most perfect flight you could ever imagine".
The lead flight director, Mike Sarafin, was emotional as he signed off from Houston.
"We challenged our best and brightest to continue to lead in space," he said. "While this was an unmanned mission, we were all on board Orion."
The agency quickly reported positive results: Not only did the capsule arrive intact, all the parachutes deployed and onboard computers withstood the intense radiation of the Van Allen belts surrounding Earth.