Sept. 22, 2006 -- The effects of weightlessness on the human body became evident today at a welcome-home event for the crew of Space Shuttle Atlantis.
Amid the festivities at Ellington Field, Houston, astronaut Heidemarie Stefanyshn-Piper fainted twice. Both times she appeared confused just before her legs began to buckle. NASA officials and fellow crew members quickly braced her fall and helped her to the ground.
Despite becoming a little red-faced, Stefanyshn-Piper remained in good spirits.
"Boy, if that's not a little embarrassing," she said, according to The Associate Press.
Stefanyshn-Piper is among the six-member Atlantis crew who returned Thursday after a 12-day stay in space to add a solar array to the International Space Station.
Experts say Stefanyshn-Piper's fainting spell is not unusual. Dr. Benjamin Levine, a professor of medicine at the University of Texas Southwestern Medical Center at Dallas, said the fainting is "nothing to be concerned about."
The heart of an average person on Earth pumps blood throughout the body. But when an astronaut is in space, Levine explained, the blood remains predominantly in their chest cavity. Because of this, he said, the heart tries to get rid of excess blood through urination.
"After about 48 hours in space, a quart of blood plasma is lost," he said.
Upon return to Earth, the heart is relatively empty and doesn't have enough blood in it to keep blood pressure up.
"From 25 to 66 percent of all astronauts cannot stand for 10 minutes following space flight of up to two weeks," said Levine.
Additionally, the 90 degree heat in Houston could have played a part in Stefanyshn-Piper's fainting spells.
While fainting may not be a cause for concern among astronauts, Clinton Rubin, a professor and chairman of the department of biomedical engineering at the State University of New York remains, remains cautious.
While the Atlantis mission is "truly spectacular," Rubin said, "the impact of spaceflight on human physiologic systems is poorly understood ... and it must be better understood before a real catastrophe occurs."