(AP) -- An astronaut who crashed his bicycle over the weekend won't be taking part in space shuttle Discovery's final voyage next month.
Astronaut Timothy Kopra suffered unspecified injuries in the accident Saturday, just 1 1/2 months before Discovery's planned liftoff. He is recuperating and on indefinite sick leave.
In a rare swap-out Wednesday, NASA removed Kopra from the crew and added veteran spaceman Stephen Bowen, who flew last May on the most recent shuttle flight. Bowen will take over Kopra's spacewalking duties during the 11-day flight; Kopra had been designated as the lead spacewalker and was to venture out twice to perform work on the International Space Station.
The shuttle flight has been on hold since November because of fuel tank cracks. Just last week, NASA said it had finally zeroed in on a cause for the potentially dangerous cracking. Shuttle repair work is continuing inside the Vehicle Assembly Building. Discovery's target launch date is Feb. 24.
This is the second time this month that NASA had had to deal with crew issues.
Last week, NASA named a backup commander for the final flight of Endeavour in April. The official commander, Mark Kelly, remains at the hospital bedside of his wife, Rep. Gabrielle Giffords, who was seriously wounded in a shooting in Tucson, Ariz. His identical twin brother, Scott, is flying on the space station right now as its skipper.
Shuttle crew replacements, at such a late date, are uncommon.
The most famous switch occurred 72 hours before Apollo 13 in 1970, after command module pilot Thomas "Ken" Mattingly was exposed to the German measles and yanked from the crew. The three men who flew to the moon on that mission almost didn't make it back alive. An oxygen tank ruptured en route, and it took all of the astronauts' effort and the ingenuity of Mission Control to safely return the crew to Earth.
To cut down on preflight injuries, NASA has a whole list of prohibited activities for astronauts assigned to space missions. Among the banned high-risk sports: skiing, parachuting and acrobatic flying. Bicycling is not on the list.
NASA has refused to elaborate on Kopra's injuries, citing medical privacy. The accident involved only Kopra's bicycle, said NASA spokesman James Hartsfield, and occurred in the Houston area.
In a statement, chief astronaut Peggy Whitson said Kopra expects a full recovery, but will not be ready to rocket into orbit by Feb. 24. If the mission is delayed significantly, it's possible he will be able to rejoin the crew, she noted. Kopra, 47, a retired Army colonel, spent two months on the space station in 2009.
Discovery originally was supposed to lift off at the beginning of November. The shuttle holds a load of supplies and spare parts for the space station, as well as the first humanoid robot bound for orbit.
Bowen, 46, a Navy captain, has flown twice in space and performed five spacewalks.
"That extensive experience, coupled with some adjustments to the spread of duties among the crew, will allow for all mission objectives to be accomplished as originally planned," Whitson said.
Bowen begins training this week with the five other crew members.
NASA is retiring its shuttle fleet this year. Only two - possibly three - missions remain.
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More information: NASA: http://www.nasa.gov/mission-pages/shuttle/main/index.html