The space shuttles, which began flying in 1981 and are capable of hauling heavy payloads, are being phased out due to high operating costs and to free up money for new spacecraft that can travel beyond the International Space Station's orbit about 220 miles (355 km) above Earth.
In Pictures: NASA's Space Shuttle
The coming retirement of the space shuttle is imperiling thousands of jobs at the Kennedy Space Center in Florida, as well as jobs in Texas, Alabama and Utah, worrying local leaders who are concerned about the economic impact and promising to be an issue in November's congressional elections.
The U.S. space agency has two more flights remaining to complete the station, a $100 billion project of 16 nations that has been under construction since 1998. Congress, however, is considering new spending plans for NASA for the year beginning Oct. 1 that would add a third flight to the station next summer.
The Senate's draft bill also directs NASA to maintain the capability for additional shuttle flights in case the station needs a large piece of equipment that cannot be delivered on any other vehicles, a scenario the agency currently is not planning for, said shuttle program manager John Shannon.
"We'll see what comes out in the legislation. If it's signed, we'll start those studies," Shannon said in an interview.
The new round of layoffs follows previous cutbacks in October 2009 and June 2010 that sidelined 743 shuttle workers, Fluegel said. Additional layoffs are expected next year.
NASA had been planning a follow-on program to the shuttle called Constellation that would have returned astronauts to the moon. An independent review panel convened by the Obama administration determined Constellation was inadequately funded and the White House decided to ax the program, favoring instead commercial space efforts and technology initiatives for future deep-space human travel.
Bills pending in Congress maintain parts of the Constellation program, but eliminate the moon as the driving destination for future NASA missions.
The level of funding for commercial space ventures, which President Barack Obama proposed to total $6 billion over the next five years, remains controversial.