An astronaut from the space shuttle Atlantis collapsed twice at an event to celebrate the crew's safe return from an 11-day mission to resume construction of the International Space Station.
Heidemarie Stefanyshyn-Piper, who performed two spacewalks during the trip, appeared confused and had to be supported by her fellow crew members as she spoke to the crowd at Ellington Field airport in Houston, Texas.
The 43-year-old US Navy commander stood up again and carried on for 30 seconds before gripping the edge of the podium, at which Nasa officials led her away.
They attributed her collapse to the effects of spending so long in zero gravity, which causes an astronaut's blood volume to drop by between 10 and 14 per cent.
The six-strong Atlantis crew landed on Thursday after a successful mission in which they made three spacewalks and bolted a new section onto the International Space Station. The new section weighs 17.5 tons and features giant solar panels which will generate the station's electricity.
Mrs Stefanyshyn-Piper , the mission's cosmic electrician, became the eighth woman to walk in space.
She was allowed home after yesterday's event. Her husband Glenn said: "She's doing 100 per cent well. Basically, she's embarrassed."
Mrs Stefanyshyn-Piper, a mother of one, became an astronaut in 1996. The Atlantis mission was her first trip into space.