-- Astronaut Hans Schlegel trained a year for a spacewalk to install a new section of the International Space Station. Instead, he'll watch from inside the station today as two colleagues do the job.
NASA officials declined to say why Schlegel, 56, was replaced by Stanley Love, 42. The other spacewalker is American Rex Walheim. Citing medical privacy rules, NASA's John Shannon would attribute the change only to a crew illness that wasn't life-threatening.
Shannon did hint at a potential culprit: space sickness, a form of motion sickness that has dogged astronauts since the first rockets carried humans to orbit. "It's a well-documented fact that some astronauts, post-launch … have symptoms of motion sickness," Shannon said Saturday when asked whether crews had ever fallen ill in space.
Schlegel, Love and five other men launched into space Thursday on shuttle Atlantis. The mission, scheduled to last 11 days, was extended by one day so Love could study his new task and may be extended by another day to allow more work time.
The assignment change means Schlegel, a German astronaut from the European Space Agency, will miss out on the main goal of today's spacewalk, installation of the station's new European laboratory. He's still assigned to a spacewalk Wednesday to replace a nitrogen tank on the station.
Claire Mattok, a spokeswoman for the European Space Agency, declined to say more about Schlegel's condition.
Today's spacewalk was scheduled for Sunday, the shuttle crew's second full day in space. On the second and third days after launch, many astronauts are still fighting nausea, disorientation and headaches that often start within an hour of reaching weightlessness.
Astronaut Al Drew said he started feeling queasy on his first trip last year less than a minute after getting to orbit. Recalling his experience two months after he returned to Earth, Drew said he stuffed a motion-sickness bag in his pocket and told himself, "I'm going to have to power through this."
Drew tried a nasal spray for his nausea, but "it was like pouring a teacup of water on a forest fire." Still, he got his work done and felt fine after two days, he said.
Others don't fight nausea but still cope with distracting symptoms. Astronaut Scott Kelly said that on the shuttle flight he commanded in August, he took medication to fight a headache and had vision troubles, though neither problem impaired his ability to do his work.
Space sickness can be such a problem, Kelly said, that commanders may have to get all the work done by "in some cases, a lot fewer" than the six to seven astronauts on a typical shuttle crew.
Most astronauts feel better, and recover more quickly, during their second or third trip to orbit. This is Schlegel's second flight. During his first, in 1993, he suffered from "a headache (like that) during a hangover," he told USA TODAY before Thursday's launch. "You are less capable. … It's a challenge." He wondered whether he would spring back faster on his second flight.
Medical experts can't predict who will get space sickness, nor do they know the exact cause. Potential suspects include the pooling of fluids in the head because of the lack of gravity and confusion of the inner ear, which helps with balance and spatial orientation.
Today, astronauts can take shots of anti-nausea medication, first given around 1990. Space sickness rarely requires major changes to a flight, but such changes aren't unknown. Astronaut Rusty Schweickart vomited so much in 1969 that his spacewalk was cut short.
Schweickart never flew in space again, one reason that astronauts are wary of confessing to being space sick. Another: notoriety.
" 'Why'd you get sick?' — you really don't want to have to answer that for the rest of your life," Kelly said.