What Happens to Astronauts When They’re Stuck in Space?

Two astronauts got stuck in space after a Boeing spacecraft malfunctioned. Their mission was supposed to last just eight days—but will likely take at least ten months. Headline-worthy stories like these seem rare. However, they are relatively common. 

What happens in situations like this? Does the International Space Station (ISS) have enough supplies for unexpected guests? Will the astronauts be okay after unplanned, prolonged exposure to low Earth orbit (LEO)?

Astronauts Get Stuck in Space Surprisingly Often 

Sunita “Suni” Williams and Barry “Butch” Wilmore docked to the ISS on June 6, 2024. The 15-foot-wide, Boeing-made space capsule—the CST-100 Starliner—was supposed to take them to and from the space station. However, the National Aeronautics and Space Administration (NASA) was unconvinced.

See, the CST-100 Starliner had a problem—multiple problems, actually. NASA revealed there were four leaks in the service module helium manifolds just hours after the capsule’s June 6 docking with the ISS. On June 11, Josh Finch, a NASA spokesperson, revealed the space agency had detected an additional leak. 

Moreover, engineers discovered issues with the reaction control system thruster. It had shut down during the flight to the ISS. There was also an improperly closed oxidizer isolation valve in the service module. In September 2024, the CST-100 Starliner returned to Earth empty, leaving Williams and Wilmore stranded.

Other Times Astronauts Were Stuck in Space

Williams and Wilmore aren’t the first astronauts stuck in space. While their unexpectedly long time aboard the ISS has made headlines, others have spent even longer in LEO. In 2022, NASA astronaut Frank Rubio was stranded on the ISS for over one year after a Russian transport vessel’s leaking radiator delayed his return flight. 

These situations can happen for the strangest reasons. In 1991, the Soviet Union astronaut Sergei Krikalev docked at the Mir space station. Seven months into his mission, the Soviet Union collapsed. The newly independent country of Kazakhstan took control of the spacecraft launch and landing site, forcing Russia to negotiate to maintain its space program. 

Kazakhstan desperately needed funds to support the country’s fledgling economy, so it couldn’t justify spending money to bring Krikalev home. Ultimately, Krikalev spent ten months in space—double what was scheduled for his original mission. In short, these situations are not unheard of. However, that doesn’t mean there is nothing to worry about when they happen.

What Happens to the Astronauts Stuck in Space

When astronauts get stuck in space, their day-to-day routines remain relatively unchanged. They typically either continue their usual duties or lend a hand to others on board the space station. That said, their presence complicates logistics—they use more consumables, take up more space and exhaust more supplies. 

The crew aboard the ISS sources drinking water from the urine processor assembly, which uses vacuum distillation to recover water from urine. The consumables supply is replenished with periodic supply drops every three months.

One such resupply drop happened on November 23, 2024, when the uncrewed Progress 90 spacecraft docked to the ISS Poisk module. It carried several tons of supplies, including food and fuel. Unfortunately, the Roscosmos cosmonauts noticed a noxious smell and unidentifiable liquid droplets upon opening the hatch. 

In response, the cosmonauts closed the Poisk hatch, sealing it off from the rest of the station. While air scrubbers and contaminant sensors enabled them to proceed with cargo transfer on schedule, the incident added to supply woes. Several outlets raised concerns after Williams appeared “noticeably thinner” in a NASA image. 

Although Williams attempted to dispel the rumors, citing fluid shift as the cause for her change in appearance, a NASA employee directly involved in the mission said, “She’s now skin and bones” and that helping her “stabilize the weight loss and hopefully reverse it” is a priority. With extra people on board, every issue takes on more risk. 

Even though the fateful mission that left Williams and Wilmore stranded was supposed to last just eight days, they will be in LEO for at least nine months. Boeing was responsible for getting the astronauts stuck in space, so SpaceX is taking over. It will use the two open seats on the Crew-9 Dragon spacecraft to bring Williams and Wilmore home. 

The Effects of Short-Term Exposure to Low Earth Orbit

The physical, psychological and emotional changes induced by exposure to LEO appear relatively quickly—sometimes even during the initial ascent. 

Physical 

Studies show 92% of astronauts get headaches during spaceflight, compared to just 38% on Earth. Most were felt during the first week spent in LEO. Increased intracranial pressure brought on by microgravity-induced shifts in cerebrospinal fluid is thought to be the leading cause. 

Blood, lymphatic fluid, urine and stomach acid shift, too. In LEO, astronauts remain in a state of free fall, which causes congestion, confusion and headaches. For instance, space adaptation syndrome is nausea caused by an imbalance of the vestibular system.

Thanks to microgravity, muscle atrophy also sets in quickly. Astronauts no longer need to walk, lift objects or even support their own body weight. They must counteract this weightlessness-induced degradation to preserve their strength.

Mental 

The ISS is a series of cramped, interconnected hallways. Even though astronauts undergo rigorous testing, mentally adjusting to this new environment is challenging. However, most have a military, engineering, aerospace or special forces background, so they are well-prepared. 

Cognitive

In an extreme environment like space, a person’s psychological and cognitive well-being is as important as physical health. After all, they must be able to make logical split-second decisions and react calmly in emergencies. 

Soon after takeoff, confusion and disorientation set in due to conflicting signals from the central vestibular system and changes in the peripheral pressure receptors. Brain functioning and reasoning may be temporarily impaired.

The Effects of Prolonged Exposure to Low Earth Orbit 

Although leading engineers, scientists and medical professionals have developed countermeasures to keep astronauts healthy, the extreme environment still takes a toll. 

Physical 

In LEO, the planet’s gravitational field exerts roughly 88.9% of the gravity felt on Earth’s surface. However, since astronauts are in perpetual free fall—the ISS travels at a constant velocity of 27,600 kilometers per hour—they experience a sensation of weightlessness. 

Microgravity causes fluid shifts and changes muscle fiber composition, so the heart doesn’t have to work as hard to pump blood throughout the body. These changes in cardiovascular function reduce blood volume and weaken the heart. 

Another relatively common effect of prolonged exposure to LEO is neuro-ocular syndrome. Increased intracranial pressure is thought to cause fluid retention, double vision, farsightedness and globe flattening. In some cases, these symptoms have persisted for years postflight. 

Mental

Astronauts see cables, metal sheets and control panels day in and day out. The breathtaking views many associate with the ISS are from the cupola—a small observation module where they spend relatively little time. 

Being in space is exciting, but conducting a mission requires strict, continuous dedication. Over time, eating the same foods, seeing the same people and living in the same space can wear down a person’s mental health. 

Cognitive

One study explicitly designed for NASA shows there is no evidence of lasting cognitive impairment or neurodegenerative decline associated with prolonged LEO living. However, it suggests that processing speed, memory and decision-making are temporarily affected.

Troubles with sleep may amplify these temporary cognitive impairments. For those aboard the ISS, one day lasts just over one hour. The station completes a full orbit every 90 minutes, so they see up to 16 sunrises and sunsets every 24 hours. 

Moreover, the space station is always light and noisy. These changes disrupt the circadian rhythm, causing sleeplessness and fatigue. Astronauts stuck in space may become increasingly disoriented without adequate sleep. 

What NASA Does to Counteract These Adverse Effects 

The ISS has welcomed a constant rotation of astronauts since 2000, so NASA knows how to counteract the short and long-term effects of LEO exposure. For starters, they have a rigorous physical regimen, requiring two hours of exercise per day on machines that simulate gravity. This prevents muscle degradation. 

A balanced assortment of supplements and dehydrated foods help stave off physical and cognitive decline. Mental health is harder to preserve, but each crew member is rigorously trained to withstand emotions like anxiety, sadness and panic. The day is scheduled in five-minute increments, which helps crew members stay on task. 

Even as astronauts stuck in space miss family milestones, important events and holidays, they remain optimistic. For instance, despite missing his son’s high school graduation and an entire year of holidays, Rubio said he enjoyed his extra time in space. 

In a similar situation, Williams and Wilmore celebrated Thanksgiving in space with smoked turkey, mashed potatoes, apple cobbler, cranberry, green beans and mushrooms. While they hadn’t planned on staying on the ISS for that long, they found a fitting assortment of dehydrated foods to mark the occasion. 

Is There a Limit to How Long Astronauts Can Survive?

With interventions like supplements and exercise regimens, astronauts can spend months in LEO without experiencing permanent physical, mental or cognitive damage. Hypothetically, they could stay relatively healthy for years if they didn’t plan on returning to Earth. That said, the changes they undergo may be harbingers of permanent damage.

Will these limitations impact the future of space travel? Almost definitely. Out of LEO, adverse physical, mental and cognitive effects will amplify tenfold. There are also new issues crew members will have to contend with, including deep-space radiation. Prolonged exposure could cause circulatory issues, central nervous system damage and cancer.

Even a mission to Mars—which would last approximately two years at minimum—is daunting with our current understanding of how space affects the human body. With our current technology, limiting missions to six months on average is not feasible when traveling out of LEO. Of course, by the time deep space travel is possible, these problems will likely already be fixed.