How the ISS Keeps Astronauts Safe for Months in Space

(Featured image courtesy NDTV)

Imagine living in a floating laboratory, 408 kilometres above Earth, where day and night change every 90 minutes, and gravity doesn’t exist. That’s life on the International Space Station (ISS). Built as a collaborative effort between NASA, ESA, Roscosmos, Kibo, and the Canadian Space Agency (CSA), the ISS has been home to astronauts for over two decades, helping researchers understand how humans can survive beyond Earth.

“The basic reason for having the space station is to understand the possibilities of human survival on the Moon and Mars,” explains Rachna Arora, a Physics Educator at Shiv Nadar School, Noida. “This also helps to explore how crops can be grown in space and how microgravity impacts human biology.”

Why were astronauts Butch Wilmore and Sunita Williams stuck in space?

Astronauts Butch Wilmore and Sunita Williams embarked on an eight-day mission aboard the Boeing Starliner (CST-100), a spacecraft designed for crew transport. However, their return was delayed due to a helium leak in the propulsion system, making re-entry unsafe. “Entering and leaving Earth is very risky, and this spacecraft faced a helium leakage, so it could not leave the ISS,” explains Rachna. Eventually, they returned via SpaceX’s Crew Dragon capsule, after spending nine unexpected months in space.

How did they sustain themselves?

Despite the extended stay, Wilmore and Williams had enough supplies to survive comfortably. “The ISS is equipped to sustain up to six astronauts, so they had enough food stored according to microgravity conditions,” says Rachna. “Their diet consists of specially packaged foods and nutrient-rich fluids to counteract the effects of space travel.”

Microgravity takes a toll on the human body. “The heart doesn’t need to push blood as hard, so it becomes slightly spherical,” explains Rachna. “Bone density reduces, and muscles weaken, which is why astronauts exercise rigorously.”

Upon returning, astronauts undergo medical tests to monitor the effects of prolonged space exposure. “Sunita Williams will need continuous monitoring, including chest X-rays multiple times a day, to assess radiation exposure,” Rachna adds. “Most of these changes, except minor genetic variations, can be reversed with proper medical care.”

How the ISS keeps astronauts safe?

Living in space poses unique challenges, but the ISS is designed with multiple safety measures:

1. Shielding against space radiation

• Protective materials: Layers of aluminium, Kevlar, and polyethylene absorb harmful radiation.
• Radiation monitoring: Astronauts wear dosimeters to track exposure, and certain areas of the ISS provide extra shielding.

2. Health & fitness in microgravity

• Daily exercise: Two hours of workouts, including treadmills and resistance training, help maintain muscle mass.
• Medical checkups: Astronauts undergo regular health monitoring, with telemedicine support from Earth.
• Nutrition & hydration: Carefully planned meals ensure essential nutrients, while water is recycled from sweat and breath.

3. Emergency preparedness

• Escape pods: SpaceX’s Crew Dragon or Russia’s Soyuz capsule serve as emergency exit vehicles.
• Fire & leak detection: Automated sensors detect smoke, fire, or cabin pressure drops.
• Meteorite protection: The station’s outer walls have Whipple Shields to absorb impacts from space debris.

4. Spacewalk safety (EVAs)

• Pressurised suits: Extravehicular Mobility Units (EMUs) protect against extreme temperatures and lack of oxygen.
• Tethers & safety gear: Astronauts are secured with tethers, and an emergency jetpack (SAFER) helps them return if they drift away.

5. Mental well-being

• Regular communication: Video calls with family and mission control keep astronauts connected.
• Mental health support: Training in stress management and access to psychologists help astronauts cope with isolation.

Who can become an astronaut?

Dreaming of space travel? Here’s what it takes to become an astronaut:

1. Educational background

• A master’s degree in STEM (Science, Technology, Engineering, Mathematics) from an accredited institution.
• Specialisations in aerospace engineering, physics, biology, or computer science.
• Alternatively, a medical degree or test pilot school training can qualify.

“All astronauts, from Rakesh Sharma to Sunita Williams, have a STEM background,” says Rachna. “They also need leadership skills and the ability to make quick decisions under pressure.”

2. Work experience

• At least two years of professional experience in a relevant field.
• Pilots must have 1,000+ hours as a jet aircraft pilot.
• Hands-on experience in research, engineering, or space technology is highly valued.

3. Physical & mental fitness

• Excellent physical health, with normal blood pressure and vision.
• Endurance training for microgravity conditions.
• Psychological resilience to handle isolation and high-pressure decision-making.

Many astronauts come from military backgrounds due to the rigorous training involved. “There are so many variables in space—from debris to solar flares. You must be prepared for anything,” Rachna adds.

While space travel is still reserved for a select few, ongoing research at the ISS is paving the way for future Moon and Mars missions. With advancements in technology, will living beyond Earth become a reality in our lifetime? Only time will tell.

Edited by Leila Badyari

Sources

How NASA's Starliner mission went from 10 days to 9 months: A timeline: by Space, Published on 18 March 2025.

What Is the International Space Station? (Grades 5-8): by NASA, Published on 30 October 2020.

Astronaut Requirements: by NASA, Published on 4 March 2020.