NASA astronaut Peggy Whitson has painted a dramatic picture of her return journey to Earth from the International Space Station on 19 April, when her crew's Soyuz capsule took an unexpected trajectory that gave the astronauts a very rough ride.

During re-entry, the capsule switched to "ballistic re-entry mode". This set the craft on a much steeper, more direct trajectory to Earth than intended and it landed 475 kilometres away from the intended site.

Whitson described the ordeal today during press interviews at NASA's Johnson Space Center in Houston, Texas. For one "very long" minute, she said, the astronauts suffered forces of 8.2 times normal gravity - nearly double the force they'd expect on a normal descent.

"There's an old pilot saying - any landing you can walk away from is a good one," she said. "That probably applies here."

"They have no desire to kill their astronauts or cosmonauts any more than we do," she said.