posted 01-25-2014 05:26 AM               

Last August, at a ceremony at the Johnson Space Center in Houston, NASA introduced its eight newest astronaut candidates. NASA Administrator Charles Bolden and center director Ellen Ochoa — both former astronauts — welcomed the new arrivals with rosy predictions for long, varied careers that would include flights to the International Space Station on a new American-made commercial spacecraft beginning in 2017, as well as missions beyond Earth orbit in the Orion Multi-Purpose Crew Vehicle.

The latest class is the smallest group NASA has chosen since 1969, and behind the high-fives and backslaps at their introduction lies a stark reality for every astronaut, rookie or veteran: Each year until 2017, there will be only four chances to fly...