Astronauts spend most of their time conducting scientific experiments, maintaining the space station, exercising to protect their bodies, and communicating with Mission Control. Their average workday is 16 hours, and they’re on call around the clock. The job extends well beyond space itself, with roughly two years of training before a mission and six weeks of physical rehabilitation after landing.
A Typical Day on the Space Station
Every weekday on the International Space Station is planned in coordination with Mission Control on the ground. The morning starts with breakfast, personal hygiene, housecleaning, and checking the day’s schedule on a laptop. After that, crew members draw blood samples for analysis and hold a conference call with Mission Control to review what’s ahead.
Work fills the bulk of the day: running experiments, performing routine maintenance on station systems, and monitoring air quality and cabin pressure. The crew gathers for lunch together, gets a one-hour break afterward, then returns to work for the afternoon shift. At the end of the day, they clean up experiments, check systems one final time, eat dinner, and hold another planning call to prep for tomorrow. Free time comes just before bed. Astronauts get about eight hours of sleep before doing it all again.
Scientific Experiments
Research is the primary reason the space station exists. The microgravity environment lets scientists study biology, physics, and human health in ways that aren’t possible on Earth. Astronauts carry out experiments designed by researchers on the ground, acting as the hands and eyes for scientists who can’t be there.
The range of research is broad. Some experiments look at how space radiation damages DNA in human cells, which helps us understand cancer risk for future deep-space travelers. Others study embryonic development in near-weightlessness using mouse stem cells, or track how radiation affects reproductive cells in silkworm eggs across generations. Astronauts also serve as their own test subjects, providing blood draws, vision tests, and other health data that help NASA understand what long-duration spaceflight does to the human body.
Maintaining the Station
The ISS is a complex machine, and keeping it running is a significant part of the job. Astronauts relocate and install large equipment racks (some the size of a refrigerator), swap out life-support hardware, reconfigure modules after repairs, and handle everything from plumbing fixes to computer maintenance. On one typical day in 2022, three crew members spent hours moving the station’s oxygen generation system from one module to another, reconnecting cables, and then reinstalling the bathroom that had to be removed to clear a path for the transfer.
Some maintenance requires going outside. Spacewalks, formally called extravehicular activities, typically last six to eight hours. Astronauts have used them to replace gyroscopes, swap batteries, install new cameras and scientific instruments, and apply protective thermal blankets to the station’s exterior. During the final Hubble Space Telescope servicing mission, five spacewalks ranged from about six and a half to eight hours each, with tasks including installing a new wide-field camera and repairing instruments that had been offline for years.
Operating Robotic Systems
The station’s robotic arm, Canadarm2, is essential for jobs that would be difficult or dangerous to do by hand. Astronauts use it to capture incoming cargo spacecraft and guide them into docking position. The arm also moves large station components during assembly, repositions equipment on the exterior, and even carries astronauts themselves during spacewalks, serving as a mobile work platform. A smaller two-armed robot called Dextre handles more delicate tasks and can be operated by controllers on the ground or by crew members aboard the station.
Exercise and Physical Health
Without gravity pulling on their bones and muscles, astronauts lose both at an alarming rate. To fight this, every crew member exercises two hours per day on a treadmill, stationary bike, or resistance machine. This isn’t optional. It’s a medical requirement baked into the daily schedule, split between morning and afternoon sessions.
Diet plays a role in protecting their bodies too. The ISS menu provides roughly 50% of calories from carbohydrates, 17% from protein, and 31% from fat, similar to standard nutrition guidelines on Earth. But certain details matter more in space. NASA has reformulated about 90 packaged foods to cut daily sodium from 5,300 milligrams down to 3,000, because high sodium intake accelerates bone loss in microgravity. Adequate vitamin D and overall calorie intake also help slow bone deterioration. One recurring challenge: astronauts tend to eat less in space than they did on the ground, even though their energy needs are about the same or higher with intense daily exercise.
Communication and Education
Astronauts regularly connect with people on the ground beyond Mission Control. NASA schedules live video downlinks with schools, where students ask crew members questions about living and working in space. A program called ARISS (Amateur Radio on the International Space Station) lets students worldwide use ham radio technology to talk directly with the crew. These sessions serve as both public outreach and a way to inspire interest in science and engineering.
Training Before the Mission
Before ever reaching space, astronaut candidates go through roughly two years of intensive training. The curriculum covers space station systems, spacewalk skills, robotics operation, and Russian language (since crew members work alongside international partners and launch from multiple countries). Candidates must complete military water survival training and become SCUBA-certified, which prepares them for practicing spacewalks in NASA’s Neutral Buoyancy Laboratory, a massive underwater tank that simulates weightlessness.
They also train in altitude chambers to learn how the body responds to both high and low atmospheric pressures, and they experience brief periods of weightlessness aboard a modified jet that flies parabolic arcs, producing about 20 seconds of zero gravity at a time. Pilot astronauts maintain flying skills with at least 15 hours per month in T-38 jets; non-pilots fly a minimum of 4 hours. Practical skills get attention too: crew members practice meal preparation, trash management, camera operation, and equipment stowage using full-scale mockups of the station’s interior.
Recovery After Landing
The job doesn’t end when astronauts return to Earth. After months in microgravity, their bodies need time to readjust to gravity. Post-flight rehabilitation starts the very next day after landing and involves two hours of progressive physical training per day for six weeks. Balance is one of the first things to come back. Most astronauts regain their pre-flight baseline balance within 7 to 10 days, which is the milestone that lets them resume everyday activities like driving.