FIGURE S.1 NASA’s formula for determining minimum manifest requirements for staffing. SOURCE: NASA Astronaut Office, “Ensuring the Readiness of the Astronaut Corps: A White Paper,” NASA Johnson Space Center, Houston, Tex., March 25, 2011.

bers’ being medically disqualified from flying again until the condition improves. In the past, attrition rates for the Astronaut Corps were based on rates for both space shuttle and ISS missions. As NASA transitions to only long-duration ISS missions, it is difficult to predict attrition rates. After their first long-duration ISS mission, members of the Astronaut Corps might choose to leave the corps rather than fly another long-duration mission with its attendant stresses on family and home life.

The development of future spacecraft also involves programmatic uncertainties. NASA has traditionally assigned astronauts roles in the development of new vehicles to benefit from their insight regarding design and for reasons of safety and mission assurance. According to NASA, those roles need to be filled by members of the Astronaut Corps who will ultimately fly in the vehicles, not by management astronauts (former astronauts who are no longer eligible for flight assignment and who do not use NASA aircraft or other training facilities except as instructors, evaluators, mentors, or providers of expertise).3 However, as presented to the committee, NASA’s calculations for sizing the Astronaut Corps focused on preparing for planned missions and did not provide for filling those additional roles.

Viewed as a supply chain, astronaut selection and training are sensitive to critical shortfalls because of the long lead times and long recovery time between missions and because astronauts, trained for specific roles and missions, cannot be easily interchanged.

On the basis of its assessment of known and potential needs, the committee concluded that the currently projected minimum target size for the active Astronaut Corps poses a risk to the U.S. investment in human spaceflight capabilities; in particular, the committee notes that the planned Astronaut Corps, sized only to meet ISS crew requirements, would not have the flexibility to accommodate unexpected increases in attrition or commercial, exploration, and new mission development tasks. Because of various sources of uncertainty and because multiple factors are involved in the training of members of the Astronaut Corps and the operation of spacecraft in orbit, it is not possible to quantify the risk posed by tight margins or size or to provide a confidence level of risk. Nevertheless, the committee concluded that the Astronaut Corps is vital to the safe and successful operation of the ISS and that reducing its size too much can create shortages of key skills.

It currently takes 2 years to train a new astronaut in the full range of ISS skills and the fundamentals of spaceflight, aviation, and NASA programs. A newly hired astronaut is not given a technical assignment until about a year after being hired, and training continues. But that new hire will not generally be credible in representing NASA and the Astronaut Corps in, for example, commercial spaceflight, development of beyond-low-Earth-orbit (LEO) spacecraft, or supporting complex ISS operations or emergencies. (New astronauts are, however, highly skilled in their own fields from the outset and could provide immediate expertise in those fields, such as test-piloting, research, and engineering development.)

NASA would be able to respond to long-term programmatic commitments by hiring new classes oriented to them, but the most valuable personnel to retain are those with spaceflight experience and long experience in


3 Management astronauts can serve as instructors, evaluators, mentors, or providers of expertise and in most cases do not use “additional” training assets. These training assets are being used in the normal course of the event that the astronaut, or whoever would act in that role, is supporting. (In a very small number of cases, additional resources may be required for the astronaut instructor to keep current, but, again, this would be required of any instructor.)

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