Nasa's Orion space capsule splashed down safely in the Pacific on Sunday, completing the Artemis 1 mission – a more than 25-day journey around the Moon with an eye to returning humans there in just a few years.

After racing through the Earth's atmosphere at a speed of 25,000 miles per hour, the uncrewed capsule floated down to the sea with the help of three large red and orange parachutes, as broadcast on Nasa TV.

"Nasa we had a picture perfect splashdown," said Melissa Jones, Nasa's landing and recovery director.

During the trip around Earth's orbiting satellite and back, Orion logged well over a million miles and went farther from Earth than any previous habitable spacecraft.

"For years, thousands of individuals have poured themselves into this mission, which is inspiring the world to work together to reach untouched cosmic shores," said Nasa Administrator Bill Nelson.

"Today is a huge win for Nasa, the United States, our international partners, and all of humanity," he added.

After touchdown, helicopters flew over the floating spacecraft, which showed no evidence of damage.

Orion will be recovered by a prepositioned US Navy ship off the coast of Mexico's Baja California after some initial tests are run.

As it re-entered the Earth's atmosphere, the gumdrop-shaped capsule had to withstand a temperature of 2,800 degrees Centigrade – about half that of the surface of the Sun.

The main goal of this mission was to test Orion's heat shield – for the day when it is humans and not test mannequins riding inside.

Achieving success in this mission was key for Nasa, which has invested tens of billions of dollars in the Artemis programme, which aims to take people back to the Moon and prepare an onward trip to Mars.

A first test of the capsule was carried out in 2014 but that time it stayed in Earth's orbit, coming back into the atmosphere at a slower speed of around 20,000 miles per hour. (AFP)