Image copyright NASA/Rad Sinyak Image caption The capsule was dropped from a military plane at more than 10km up

Nasa says the most difficult test yet of the parachute system for its Orion spacecraft has gone without a hitch.

The test version of the Orion capsule touched down safely in the Arizona desert after being dropped from a C-17 military aircraft at 10.6km (35,000ft).

The US space agency said Wednesday's test was the closest to simulating a real return to Earth.

Orion is designed to replace the shuttle as America's manned space transport system.

"We've put the parachutes through their paces in ground and airdrop testing in just about every conceivable way," said Orion's programme manager Mark Geyer.

"The series of tests has proven the system and will help ensure crew and mission safety for our astronauts in the future."

Image copyright NASA Image caption The capsule is being prepared for its first space test flight in December

Nasa is preparing Orion for its first trip to space in December, a two-hour, four-orbit flight that will send an unmanned version of the spacecraft more than 5,700km (3,600 miles) into space.

It will then be returned to Earth to test the performance of many of the craft's critical systems.

In the latest test, over the US Army's Yuma Proving Ground, engineers put additional stresses on the parachutes by allowing the test craft to "free fall" for 10 seconds, which increased the vehicle's speed and aerodynamic pressure.

After the free fall, Orion's parachutes deployed, pulling away the spacecraft's forward bay cover, which is critical to the rest of the system performing as required.

The test marked the last time the entire parachute sequence will be tested before Orion launches on its first space flight test, called EFT-1, later this year.