A new report published by the National Research Council recommends that NASA should "take steps" to maintain a highly trained astronaut corps - even as the United States enters an extended post-shuttle era.
According to the NRC, the corps should meet International Space Station (ISS) crew requirements, while accounting for unexpected attrition or demands of other missions.
Currently, NASA's plan for staffing the U.S. astronaut corps does not provide sufficient flexibility to reliably meet projected ISS mission needs.
"With the retirement of the shuttle program and the uncertainty during the transition to a fully operational ISS, it's even more important that the talent level, diversity, and capabilities of the astronaut office be sustained," explained Joe Rothenberg, co-chair of the committee that wrote the report and a former senior NASA official now with the SSC (previously known as the Swedish Space Corp).
"Making sure NASA maintains adequate training facilities is also essential to ensure a robust astronaut corps."
To be sure, the number of NASA astronauts was substantially reduced in recent years - from nearly 150 in 2000 to 61 astronauts in 2011. As expected, much of the decrease was attributed to the planned retirement of the space shuttle and the transition from building to operating the ISS.
Yet, the model NASA employs to predict minimum staffing requirements cannot fully account for uncertainties or contingencies, such as retirements and astronauts who may experience temporary or permanent medical disqualifications. Therefore, the space agency includes a management margin in calculating astronaut requirements - which the NRC wants increased to maintain a mission-ready fleet of trained professionals capable of safely operate the ISS.
"Viewed as a supply chain, astronaut selection and training is very sensitive to critical shortfalls; astronauts who are trained for specific roles and missions can't be easily interchanged," said committee co-chair Frederick Gregory, former commander of three shuttle missions who also served as NASA's deputy administrator.
While the retirement of the space shuttle program has reduced certain training requirements for NASA astronauts, operating the ISS imposed many complicated new ones that take years of training.
For example, astronauts must now be familiar not only with U.S. equipment aboard the ISS but also with European, Japanese, and Russian station modules and equipment. They must also be proficient at using space station software, conducting extravehicular activities, operating the space station's robotic arm, and numerous other tasks.
Finally, the report recommends that NASA retain its crew-related ground facilities in the post-shuttle era, including the astronaut corps' fleet of T-38N Talon two-seat training aircraft.
Emergency response in an aircraft environment has been shown to ready astronauts for anomalies in actual spaceflight, while also helping crew members develop the skills and ability to work together in fast-paced, physically stressful situations with potentially severe penalties for failure.
Astronauts flying in the back seat of the aircraft train to perform critical tasks such as communications, navigation, and emergency response in a demanding environment that cannot be effectively simulated by other means.