If you look at the NASA / CSA / ESA website for the astronaut selection process, it usually lists 3-5 different criteria for being eligible for getting qualified for astronaut candidacy. Most people don’t understand that this is an eligibility criterion for being considered, not a requirement for the candidacy.

Several books share knowledge on this topic, and there is no single way to become an astronaut and a space explorer. The path is hard and less taken or traveled, but it is full of adventure and excitement if you are up for it.

Astronaut requirements are pretty strict, and these are some in no particular order for different space agencies around the globe.

  • Possess a master’s or higher degree* in a STEM field, including engineering, biological science, physical science, computer science, medicine, or mathematics, from an accredited institution.
  • Have at least two years of related professional experience obtained after degree completion OR at least 1,000 hours pilot-in-command time on jet aircraft.
  • Be able to pass the NASA long-duration flight astronaut physical.
  • Be a citizen of that country or continent running the hiring process.

Astronauts are extremely fit; these are some physical requirements:

  • Age: 26 to 46-years-old
  • Eyesight: Distant visual acuity: 20/100 or better uncorrected, correctable to 20/20 each eye.
  • Blood pressure: 140/90 measured in a sitting position
  • Height between 62 and 75 inches (commander or pilot); between 58.5 and 76 inches (mission specialist). The minimum height was 4 feet, 10½; the maximum was 6 feet, 3 inches.
  • Weight should be between 50 and 95 kilograms (110 and 209 pounds)

  • Be able to swim three lengths of a 25-meter pool without stopping.
  • Tread water for 10 minutes wearing a flight suit
  • Have a VO2max (maximal oxygen uptake) of at least 32.9 ml/min/kg, ranging from 38.7 to 43.8 recommended.
  • Pass a sensorimotor assessment with detailed requirements ranging from sensory acuity to posture and gait.
  • Have hematological and immunological test results within the normal range for the general population.
  • Pass a battery of muscle strength tests.
  • All this is making sure that simple things in your body are not deviated from normal range like cholesterol, glucose/diabetes, BPM etc.

Besides the above, having a background in medicine, chemistry, plumbing, mechanic, scuba diving, or being an EMT can also help.

Below is an image that mentions some topic agencies ask you to be familiar with or have a decent understanding for being elected for interviewing. (CSA)

The interviewing process is arduous. The interviews usually last for an entire year, and if you cannot leave or sacrifice whatever you are doing in that time, you will not be able to continue. That means leaving your well paid stable job if you have to.

From what I am aware of the previous processes that were held, this is what it boils down to during the hiring process:

  • Application System Opens: 10,000-20,000+ applicants.
  • Qualified applicants shortlisted: ~6,000-7,000
  • Request for full applications: ~2,000
  • Initial Medial Screening.
  • First Interview: ~1,000
  • Medical Testing & Aptitude Testing – Phase 1: ~100
  • Aptitude Testing Phase 2: ~70
  • Medical Testing Phase 2: ~20.
  • Final Interview: ~15.
  • Press Announcement.
astronaut in space

Astronaut responsibilities are broken down in two sections:

Commander / Pilot:
Pilot astronauts serve as both Space Shuttle and International Space Station commanders and pilots. During the flight, the commander has onboard responsibility for the vehicle, crew, mission success, and flight safety. The pilot assists the commander in controlling and operating the vehicle. In addition, the pilot may assist in the deployment and retrieval of satellites utilizing the remote manipulator system in extravehicular activities and other payload operations.

Mission specialist: These astronauts work with the commander and the pilot and have overall responsibility for coordinating operations in the following areas: systems, crew activity planning, consumables usage, and experiment/payload operations. Mission specialists are trained in the details of the onboard systems, the operational characteristics, mission requirements/objectives/research, and supporting equipment/systems for each of the experiments conducted on their assigned missions. Mission specialists perform extravehicular activities (EVAs) or spacewalks, operate the remote manipulator system, and are responsible for payloads and specific experiment operations.

Besides all of the above, being an astronaut is more than filling up a checklist for a job interview or having a fancy resume:

It is about living by a code, having high ethics, morals, and principles towards life. It is about having a high moral character, being humble, kind, and most importantly possessing nobility and honor in everything you do.