Psychological stability is considered among the most important criteria for choosing astronauts. Generally, this isn’t incredibly difficult given the types of backgrounds the candidates come from such as fighter pilot, engineers with doctoral degrees, CIA and FBI agents among others. These are careers that already generally either require stringent psychological evaluation or which are high stress such that psychological weakness would likely manifest at some point.
The Behavioral Health and Performance department at NASA is tasked with two functions in astronaut selection. They must determine who is suitable which is the opt-in function and who should be disqualified which is the opt-out function. The psychological selection process assesses these things separately. The first part of the evaluation involves an initial set of interviews. After this, applicants are evaluated to determine if they are suitable to become an astronaut. Factors assessed include such things as the ability to remain calm under pressure and the use of emotional regulation skills, problem-solving ability, how the applicant functions in a group, personality, resilience, adaptability, flexibility, social skills and emotional lability among other things.
After the suitability interviews candidates to determine if there are reasons to disqualify them. A candidate may be disqualified due to clinical psychopathology. There are some unique stressors, and challenges astronauts must cope with in space so any type of existing psychiatric problem will most likely disqualify them. Marital problems and family problems can also contribute to being disqualified.
In addition to these interviews, applicants participate in field exercises at the Johnson Space Center to simulate some of the unique challenges of living and working in space. The specifics of these trials are not disclosed to the public for security reasons.
Some of the assessment methods that are used to evaluate and select astronaut candidates include structured interviews, validated paper-and-pencil personality and cognitive measures, and situational judgment tests that mimic tasks performed in space. Again, the specifics of the subject matter and actual assessment methods used to measure psychological factors are not disclosed to prevent applicants from manipulating the selection process by “faking good.”