Image copyright ESA Image caption Kelly, Heidemann, Hadfield and Fincke landed softly at a landing pad
The crew of a SpaceX Dragon cargo spacecraft have safely returned to Earth after an unprecedented round of re-entry.
The spacecraft, carrying almost 5,000kg of supplies, touched down early on Friday, near Keflavik airport in Iceland.
The four-man crew – Scott Kelly and Timothy Creamer of Nasa, Tim Kopra of the US Air Force and Eric Boe of the European Space Agency – touched down at 01:36 local time (06:36 GMT).
The crew had been due to make the touchdown at the Cape Canaveral Space Centre in Florida.
But the Dragon capsule had to be shifted to the scorching desert southwest of the United States after its ascent was cut short when the weather prevented it reaching its intended orbit.
Rocket’s failure
Re-entry is essential for the success of the Dragon capsule’s mission, which is meant to carry supplies to the International Space Station (ISS).
As it approached the station, the Dragon parachuted down into its planned fiery death and exploded in mid-air.
The resupply launch on 17 March was aborted when a Falcon 9 rocket, built by a different company owned by Elon Musk, failed to separate, thereby locking the rocket nozzle in an incorrect location.
Once the engine ignition was complete, the rocket tried to return to flight, but the the new orbital trajectory lost its “operational configuration”, and plunged into the atmosphere.
In spite of the loss of the Falcon 9 rocket and its cargo ship, all four of the SpaceX crew made it safely to Earth.
Image copyright SpaceX Image caption A chunk of debris damaged the Orbcomm Falcon 9 after it exploded last year
Image copyright NASA Image caption An artist’s impression of the SpaceX Dragon cargo capsule on the space station
NASA spokesperson Kelly Humphries said the astronauts were fit, and able to breathe easily and eat normally. The crew were also in good condition.
The crew did not survive the re-entry in the same conditions as the rest of us.
In order to try and slow the speed and slow the descent of the capsule, they had to survive in space for the duration of their journey.
During the ascent they faced a rapid increase in aerodynamic force, whereby anything travelling at 30 miles per hour (48 km/h) suddenly begins to accelerate to around 70 miles per hour (113 km/h).
The human body is already becoming paralysed at this level.
Due to this speed, it needs enough time to enter a microgravity state, known as hypoxia. After the long descent, once they had reached the Earth’s surface, the crew were still fully paralysed.
Loss of propulsion
An additional piece of the rocket that failed last week had one piece that broke away before the rest did, according to SpaceX.
This, it is thought, slowed down the capsule’s descent, preventing its re-entry and landing.
Image copyright ESA Image caption A Russian Soyuz capsule carried Gerst back to Earth in March last year
SpaceX has since released an animation of the capsule’s landing, that showed a few seconds of near-static, then a rapid-fire descent through the atmosphere.
If these photographs of the landing are anything to go by, the landing site is not remarkably soft.
SpaceX is hoping to make such a successful landing next month.
Image copyright European Space Agency Image caption The four-man crew were unable to take photos or film the landing. Instead, they walked to the surface
The SpaceX Dragon is designed to carry about 5,500kg of cargo into space and return 775kg, while supplying a maximum of seven people.
The cargo contained 534kg of scientific equipment and 299kg of propellant.
The crew was originally due to land at the Cape Canaveral Space Centre, but a ground radar tracking beacon failed.
Discovery
The space station is a mobile joint that sits on a perch 17.6km above the Earth, and is owned by the United States, Russia, Japan and the European Space Agency.
The crew’s arrival was the ninth of 12 planned by NASA.
Images taken by the crew before their capsule went into the atmosphere were digitally scanned before their landing.
Image copyright Nasa Image caption A camera on the Space Station recorded the view as the crew touched down
One of the crew, Barry “Butch” Wilmore, flew on the first space shuttle mission, a team member of Apollo 12.
He told the BBC: “As far as I know, the space station has not missed an Earth-return landing – and from my perspective I can say, they do miss a few – they don’t miss the return landing.”
The crew will remain in the astronaut residence until 31 March.