NASA needs to keep its astronaut training pipeline intact, and flying jets, concludes an expert panel report.

The National Research Council's "Preparing for the High Frontier⎯the Role and Training of NASA Astronauts in the Post-Space Shuttle Era," report calls for the space agency to stabilize the ranks of astronauts. Their numbers are down from about 150 in the mid-1990's to about 60 individuals now, with a number of space shuttle pilots retiring along with their vehicle just this year. NASA expects to see that number stabilize at or below that number, says the report, and hire 15 more astronauts over the next five years

"Since 2009, there has been considerable debate and disagreement between Congress and the White House about the future direction of the U.S. human spaceflight program. While there is currently no clear plan to send U.S. astronauts beyond low Earth orbit in the foreseeable future, it remains a possibility, particularly in light of NASA's recent announcement of the agency's intention to develop a Multi-Purpose Crew Vehicle for follow-on exploration of space," says the report.

For that reason, and because of uncertainties tied to staffing the International Space Station,the space agency's 25% margin for extra astronauts (which bumps minimum needed astronauts to a high of 61 in 2014) should be raised, says the study, chaired by former NASA officials Frederick Gregory of Lohfield Consulting and Joseph Rothenberg of SSC.

Space station training takes three years instead of one for a shuttle mission, adding to astronaut needs caused by retirements. Health concerns such as bone loss, shoulder injuries from spacesuits and (newly-documented) vision-damaging swelling of the eye that afflicted 7 of 15 long-duration station crew members, also add to worries over the astronaut corps.

Finally, the report calls for astronauts to keep training in T-38 jets, a hallmark of the program that hearkens back to its "Right Stuff" origins five decades ago: