What do astronaut candidates do?
Astronaut candidates, often called astronaut candidates or “ASCANs,” spend their time learning, testing, and proving they can operate safely in extreme environments.
Their work is a mix of scientific training, physical conditioning, technical study, and team-based problem solving that prepares them for spaceflight.
The role is more than glamorous simulations and launch-day excitement.
It is a long, disciplined process designed to turn highly skilled professionals into mission-ready crew members for the International Space Station, lunar missions, and future deep-space programs.
What the astronaut candidate phase is
The astronaut candidate phase is the period after selection when a person begins formal training before becoming eligible for assignment to a space mission.
In NASA, this status typically lasts for years and includes classroom work, simulations, survival training, robotics, spacewalk preparation, and station systems instruction.
Other agencies, including the European Space Agency, JAXA, CSA, and Roscosmos, have similar pipelines, though the specific training content varies.
Regardless of agency, astronaut candidates are expected to build technical competence, physical resilience, and strong judgment under pressure.
Core responsibilities of astronaut candidates
So, what do astronaut candidates do on a daily basis?
Their responsibilities usually fall into several major categories:
- Study spacecraft and station systems
- Practice emergency response procedures
- Train in simulators and mockups
- Develop robotics and rendezvous skills
- Complete survival and field exercises
- Maintain physical fitness and medical readiness
- Work in teams on mission scenarios and technical tasks
These tasks are not optional extras.
They are part of a structured program that builds the knowledge and habits needed for human spaceflight, where small mistakes can become serious safety risks.
Technical training and spacecraft systems
A large part of an astronaut candidate’s schedule involves learning how spacecraft, capsules, and space station systems operate.
This can include life support, communications, power, thermal control, propulsion, guidance, navigation, and docking systems.
Candidates study the hardware they may someday fly on, such as SpaceX Crew Dragon, Boeing Starliner, or other agency-specific vehicles.
They also learn how International Space Station modules function, including environmental controls, computer systems, robotics interfaces, and cargo handling procedures.
This technical training is essential because astronauts must be able to troubleshoot problems quickly.
In space, crews rely on understanding not just what a system does, but how it fails and what backup procedures exist.
Robotics, EVA, and mission operations training
Astronaut candidates often train on robotics and extravehicular activity, or EVA, which is the technical term for spacewalks.
Robotics training may involve operating the Canadarm2 or similar manipulators used to move cargo, capture visiting vehicles, or support station operations.
EVA preparation is especially demanding.
Candidates practice using spacesuit hardware, learning airlock procedures, handling tools, and moving safely in simulated microgravity environments.
They also rehearse emergency scenarios such as suit malfunctions or communication loss.
Mission operations training teaches candidates how space missions are planned and executed.
They learn to follow timelines, communicate with mission control, and respond to changing conditions without losing situational awareness.
Why physical fitness matters so much
Astronaut candidates do not spend all day in classrooms.
They must keep a high level of physical fitness to support long-duration missions, EVA work, and emergency readiness.
Training often includes cardiovascular exercise, strength work, flexibility, and medical monitoring.
Spaceflight affects the body in measurable ways, including bone density loss, muscle atrophy, fluid shifts, and balance changes.
Candidates need to understand these risks and develop the habits that help reduce them.
Good fitness also supports endurance in training environments such as underwater labs, desert survival exercises, and aircraft parabolic flights.
Medical readiness and human performance
Medical evaluations continue throughout the candidate phase.
Astronaut candidates must stay within agency health standards and learn how space medicine supports crew safety.
They may study nutrition, sleep management, stress control, and how the body responds to microgravity, radiation, and isolation.
Human performance is a serious focus because astronauts spend months in confined environments with limited resources.
The ability to remain calm, alert, and coordinated can affect mission success as much as technical expertise.
How astronaut candidates train for emergencies
Emergency training is one of the most important parts of the job.
Candidates practice fire response, cabin depressurization procedures, water survival, remote landing survival, and evacuation drills.
They may also complete wilderness survival training in environments such as forests, oceans, snow, or deserts depending on the agency.
The goal is simple: if a spacecraft landing goes wrong or a vehicle returns off-course, the crew must know how to survive until rescue arrives.
This is why astronaut candidates are trained to function in harsh, unfamiliar conditions with limited supplies.
Teamwork and communication are part of the job
Astronauts do not work alone, and astronaut candidates are evaluated on how well they collaborate.
Space missions depend on clear communication, trust, and the ability to accept feedback from instructors, engineers, flight surgeons, and fellow candidates.
Candidates often rotate through group tasks that reveal leadership style, problem-solving habits, and communication skills.
Agencies look for people who can remain precise, respectful, and effective under stress.
Technical talent matters, but mission teams also need emotional steadiness and reliability.
How long does the astronaut candidate phase last?
The candidate phase usually lasts about two years at NASA, though exact timing can vary based on the agency, training progress, and mission needs.
During this period, candidates are not yet fully assigned as flight crew, but they are expected to absorb a large volume of knowledge quickly.
By the end of training, a candidate should be able to support many spacecraft and station operations, respond to standard emergencies, and integrate smoothly into a flight team.
In practice, the phase is a filter for competence, consistency, and adaptability.
What makes astronaut candidates different from other trainees?
Many professionals train for specialized jobs, but astronaut candidates train for a workplace where there is no easy rescue, no spare crew waiting nearby, and no room for sloppy execution.
They must be able to shift from scientific research to engineering troubleshooting to physical survival tasks.
The role combines the expectations of a test pilot, engineer, scientist, operator, and expedition member.
That mix is what makes astronaut candidate training unusually broad and demanding.
Examples of what they may do in a typical week
A typical week can include classroom lessons, simulator sessions, fitness work, aircraft training, technical briefings, and field exercises.
A candidate might spend one day practicing robotics with a station mockup and another day learning how to use navigation tools for a survival scenario.
- Monday: spacecraft systems classroom instruction
- Tuesday: simulator drills and emergency response practice
- Wednesday: fitness, medical checks, and robotics training
- Thursday: EVA systems review and suit practice
- Friday: mission planning, team exercises, and technical assessments
This schedule is intensive because astronaut candidates must build a wide skill set in a relatively short period.
Every activity is connected to future mission readiness.
Why astronaut candidate training matters for future missions
As NASA’s Artemis program, commercial crew flights, and international mission partnerships expand, astronaut candidates need to be ready for more complex assignments.
Training now supports not only station operations but also lunar surface exploration and future Mars preparation.
That is why the question “what do astronaut candidates do” has a broad answer: they prepare to become the people who will live, work, and make decisions beyond Earth.
Their training is the bridge between selection and spaceflight, and every part of it is designed to reduce risk while building capability.