WASHINGTON -- Like a veteran NFL team, NASA's aging astronauts are piling up injuries -- raising concern that the National Aeronautics and Space Administration and its 61-member corps will have enough healthy astronauts available for rigorous six-month shifts aboard the International Space Station, according to a new report.
Most worrisome is a recently diagnosed -- and not fully understood -- eye problem found among some astronauts returning from space that can cause headaches and blurry vision.
"This condition has led to several members of the Astronaut Corps being medically disqualified from flying again until the condition improves," noted researchers for the National Academies in a report made public Wednesday.
The affliction, known as papilledema, involves swelling of the optic disk and can cause blurred vision, blind spots or -- in severe cases -- loss of vision. It was found in nearly half -- seven of 15 -- astronauts examined in one study by NASA.
This included "some lingering substantial effects on vision," and astronauts were "not always able to re-qualify for subsequent flights," according to the 102-page report, which provided no additional details.
NASA did not immediately respond to questions about these figures, but papilledema is believed to be a symptom of increased pressure on the brain caused by body fluids shifting in space -- although it's not yet known why it affects only some astronauts.
"It's a significant health concern, and it is one of the major issues NASA will have to contend with (moving forward)," said Dr. Jonathan Clark, a former NASA flight surgeon and an adviser with the National Space Biomedical Research Institute. Clark's astronaut-wife, Laurel, died in 2003 when space shuttle Columbia broke up over Texas as it was returning to Earth.
The study by the National Academies, the nation's top science advisers, was requested last year by the White House, which is trying to chart a new, post-shuttle path for NASA. A committee of 13 experts -- five of them former astronauts -- conducted the study.
Also worrisome for NASA's astronaut corps -- whose average age is nearly 48 -- are more-routine injuries caused by working in a spacesuit.
According to the National Academies report, the bulky suits have forced five crew members in the last 18 months to undergo shoulder surgery and led to 26 injuries to the elbow or shoulder that have required rehabilitation.
Former astronaut Leroy Chiao, who spent six months aboard the station, said he never felt the effects of papilledema but said astronauts long have complained about shoulder injuries -- an unintended consequence, he said, of a design change to the upper torso of the spacesuit in the 1990s that reduced the risk of leaks but reduced mobility -- leading to injuries.
"People were injuring themselves in suits," said Chiao, who said astronauts often pushed themselves too far. "Working in a spacesuit is physically demanding. There is no doubt about it."
Health was one of several reasons cited by the National Academies as to why NASA should consider increasing the size of its astronaut corps -- despite the retirement of the space shuttle this summer and the bleak prospect of NASA launching a new government-owned rocket before 2017, if then.
National Academies researchers, while not specifying a number, said NASA should go above its plans to keep the corps at 55 to 60 members through 2016 (down from a high of 149 in 2000). Nine astronauts currently are in training.
While the number of NASA astronauts required to staff the station is low -- four to six annually -- the report said many times that number were needed to help develop new spacecraft, work ground operations for other missions or be available as backup in case someone assigned to a station assignment can't do it.
"The thing we worry about is if we are not going to be able to fill one of our seats or one of our positions on the space station," said Joe Rothenberg, one of the report's co-chairs and a former NASA associate administrator. "It would be a national embarrassment."
Bone loss during spaceflight is another factor. Recovery can take as long as three years from a six-month shift aboard the station -- impacting how quickly astronauts can get back into rotation.
Still, an uncertain future for NASA and the station raises questions whether NASA needs a corps of 60 or more astronauts.
Because of recent mechanical trouble with the Russian Soyuz spacecraft -- the only way to transport crew to the station -- NASA and its partners may have to abandon the station this fall if Moscow can't fix the problem.
Then there's another, more Earth-bound concern: money.
While the astronaut office costs only tens of millions of dollars annually -- NASA won't say exactly how much -- the years ahead look increasingly tough with Congress looking to cut spending and the White House asking agencies to submit budgets 10 percent below current levels, a nearly $2 billion cut to NASA's current $18.5 billion funding level.
In a response to written questions, NASA spokesman Mike Curie wrote that the "report offers helpful advice about the appropriate size of our astronaut corps as we enter this exciting new era of space exploration and crew transport operations."