Challenges of Living in Zero Gravity on the International Space Station

Updated on March 21, 2018
Glenn Stok profile image

Glenn Stok has a Master of Science degree and he enjoys studying, researching, and discussing fields of science, physics and philosophy.

Based on my interest with human survival without gravity, I've done a lot of research on how astronauts live in space. My college background and my Masters Degree in Computer Science give me the advantage of understanding and explaining the scientific endeavor of the International Space Station.

The work with the ISS has begun in 1998 and it’s continually being built with additional modules, external trusses, and solar arrays that are launched to the site by Russian Proton and Soyuz rockets, American Space Shuttles, and more recently by Elon Musk’s privately held SpaceX aerospace manufacturer.

Elon Musk has a goal of enabling the colonization of Mars, which is making this whole scenario even more fascinating.

International Space Station
International Space Station | Source

The International Space Station

The mission of the ISS is to conduct science experiments, research projects, and investigate life without the amenities of gravity or limitless life supporting necessities that we take for granted on Earth. The work being done may lead to knowledge of how to colonize the Moon and possibly Mars.

The ISS consists of 14 pressurized modules that have been added one by one. These modules contain science labs and living quarters.

The first module of the ISS was placed in low Earth Orbit in 1998. That’s an average altitude of about 248 miles (or 400 kilometers) above the Earth. It circles the Earth every 90 minutes.1

The ISS is constantly falling back to Earth. However, the magic of making it remain in orbit is the speed it moves, known as “orbital velocity”. This speed (close to 18,000 MPH) is required to cause any object to be perfectly balanced between gravitational pull and its forward thrust around the planet.

Orbital velocity is what causes the Moon to stay in orbit around the Earth and the Earth to stay in orbit around the Sun.

There are sometimes up to ten crewmembers inhabiting the ISS at one time. It truly is an international expedition, as they are from the United States, Russia, Japan, Canada and European Partners. The U.S. has been footing more than half the cost to build and maintain the mission ($100 Billion as of 2014).

Most countries refer to their crewmembers as astronauts. The Russians are known as cosmonauts.

Until recently they stayed on board only six months before returning to Earth because life in space takes a toll on the human body, as I’ll explain later. However, lately they stay is a full year to extend the experiment.

A trip to Mars takes two years, so this extended living arrangement on the ISS helps collect vital data about the impact on humans.

What Do Astronauts Need to Survive in Space?

Recycling Wastewater

Water is the most precious commodity, especially in a self-contained living environment where new supply is impossible to attain. Therefore, all wastewater needs to be collected and recycled. This includes perspiration as well as urine.

Perspiration is collected from sweaty cloths as well as removed from the air. A pleasing name has been made up for the water collected from perspiration: Humidity Concentrate.

Using distillation, about 85% of the water in urine is recovered. Overall, about 94% of all the wastewater from the astronauts is recycled.

Creating Breathable Oxygen

Oxygen is replenished by separating it from the water through electrolysis. I used to do that as an experiment in high school science class. We learned how water is chemically made up of two Hydrogen atoms for every single Oxygen atom. That’s why it has the chemical name H2O, which represents that configuration of molecules.

The method is simply done by inserting electrodes in the water with a DC current. The DC current splits the water molecules into its individual atoms. The negative electrode collects hydrogen gas and the positive electrode collects oxygen.

Besides oxygen, other atmospheric components such as nitrogen, carbon dioxide, hydrogen, methane, and humidity, are monitored and controlled by a device called the Major Constituent Analyzer.

Maintaining a Healthy Heart While Living in the Space Station

Astronauts lose muscle tone while in space due to the lack of gravity on the body. However, the heart is also a muscle and it will weaken to the point that it fails if a human spends too much time in space.

The solution is to exercise against the resistance of elastic ropes. Think of it as running on a treadmill with oversized rubber bands holding you to the mill. The same had to be done with exercising every part of the body.

The astronauts have to be diligent about this exercise routine. They need to exercise two and a half hours each day while in space.

What Is It Like In Space for Astronauts?

How Astronauts Have Personal Privacy

Each astronaut has his or her own personal quarters, known as a crew cabin. This is the only place where they have privacy. It contains a sleeping bag and personal effects. The crew cabins are small, just big enough for one person.

They also have a laptop to keep notes, write about their thoughts and feelings, and communicate with friends and family back home. WiFi is available on the ISS, so they can use email or Skype.

Personal Hygiene in Space

They do need to get haircuts occasionally. Female astronauts tend to leave their hair long. The men get haircuts with a buzz cutter that has a vacuum machine attached to it to capture the hair as it’s cut off. Otherwise, the hair would float away since there is no gravity.

The lack of gravity also rules out the ability to have running water. Water would just float around the space capsule. Therefore, they wash their hair with a no-rinse shampoo.

When brushing their teeth, they need to keep their lips closed. Otherwise, the saliva and toothpaste will just float out. Not a pretty sight.

How Astronauts Eat in Space

The lack of running water makes eating a very different task than you can imagine.

Food is dehydrated or freeze-dried, and stored in plastic packages. The astronauts squeeze water into the food packages before eating. Hot water is used to make hot meals. Freeze-dried fruit can be eaten dry.

Cooking in Space

How Astronauts Sleep in Space

As I mentioned earlier, each astronaut has his or her own crew quarters. They spend their alone time in there and when they sleep, they usually use sleeping bags so they don't float around.

The sleeping bags can be attached to a wall or upside down on the ceiling. Remember there really is no up or down in space, so they can sleep anywhere in their cabin.

They generally sleep eight hours for a good night’s rest to be ready for another busy day.

Inside Look at an Astronaut's Personal Crew Cabin

Keeping Health Records

They keep a record in the computer of what they eat so NASA can keep track of everything: How many calories, protein, how much salt they are getting, and so on.

When they lift weights they even have to keep track of how much weight and how many reps they did. The computers record their heart rate when they are working out. Everything needs to be kept track of with accuracy. By the way, lifting weights is not the same as on Earth. It’s done by pulling or pushing against resistance of springs or elastic bands.

There are no secrets in space. They even have to keep a record of when they use the toilets.

Exercising in Space

How Astronauts Go To the Bathroom in Space

Both urinating and bowel movements need to be handled in a completely different manner in a weightless situation. You wouldn’t want that stuff floating away from you.

A vacuum system is built into the special toilets. Astronaut Samantha Cristoforetti shows you how space toilets work in this next video.

How to Use a Space Toilet

How Astronauts Clean in Space

Living in such a cramped space, it’s important to keep a clean environment. Once a week they go around with a vacuum, but they also need to clean everything with a wet wipe that kills germs.

They use wet wipes to clean their eating utensils too—their forks, spoons, and trays.

The Difficulties of Life in Space

Space Junk

People don’t only pollute our land and oceans. We pollute space too.

A major concern is the existence of orbiting space junk that can be deadly if any of it strikes the ISS. This junk consists of over 100,000 pieces of discarded satellites and rockets—and increasing.

A solution that has been tested in labs is the use of two layers of shields around every part of the ISS that is important to the survival of the crew.

If small objects the size of a grain of sand that can’t be detected were to strike, the outer shield slows it down and causes it to dissipate, so that it’s too weak to penetrate the second shield.

Larger space junk is monitored by mission control. They are constantly making changes to the path of the ISS to avoid these larger pieces. They do this from the ground control so that the astronauts don’t even have to think about it.

The Cygnus Orbital Delivery Capsule

You can’t just go to the local grocery store or Home Depot when you need something.

The Cygnus Orbital Delivery Capsule is a space vehicle that is used to replenish needed items. It’s launched about every six weeks containing groceries, clothing, and new science experiments.

Once the Cygnus Capsule is within 10 meters of the ISS, they use a robotic arm to capture it and guide it to connect with the locking hatch. The astronauts can then open the hatch and enter the capsule to get all the new goodies.

Cygnus Orbital Delivery Capsule
Cygnus Orbital Delivery Capsule | Source

How Trash Is Handled on the ISS

We take it for granted, but trash accumulates among the astronauts just the same as out trash builds up in our homes. They deal with it the same way, filling garbage bags.

The bags also contain the dirty laundry since they can't wash anything. They wear things much longer for that reason, but then they dispose of it with the rest of the trash.

They store those garbage bags in the Cygnus Orbital Capsule. The Cygnus takes the trash with it when it leaves.

When Cygnus enters the Earths atmosphere it burns up, just as most meteorites do, and all the trash burns up with it.

The recent SpaceX Dragon Capsule, which also delivers supplies to the ISS, has the added advantage that it successfully returned 5,400 pounds of science equipment and other gear in March 2017.

Keeping Busy on the ISS

Scientific Lab Experiments Done on the ISS

Experiments are constantly being carried out on tests such as how crops will grow and how animals are bread in weightlessness. These experiments are being done in anticipation of journeys farther out someday.

Ants are studied to see how they handle weightlessness. They get confused as they fall and just float around.

Variations of vaccines are also tested to study how they develop in a weightless environment.

Keeping Things Cool on the ISS

Equipment and experiments that need temperature control are kept cool by a cooling pump that's attached outside the ISS.

If that fails, mission control can try to repair it remotely. In some cases that’s not possible and a couple of astronauts need to do a space walk to go out and fix it.

Space Walk to Fix the Cooling Pump

Astronauts need to wear a space suit that is a complete life support system to do a space walk. This includes the ability to hold waste if they need to relieve themselves.

When working outside the ISS, they have no sense of touch since they are literally floating in their space suits. They need to inch their way along, holding on while they work their way to the cooling pump to replace it with a spare.

At least carrying an 800-pound pump is easy since in space they are weightless, but they still have to be careful not to rub up on anything that might tear their space suit.

One thing they have no control over at all is the concern about micrometeoroids. These small particles can hit their space suit at any time and there is no way to avoid the possibility.

Astronaut Michael Fincke Busy with a Spacewalk Repair Mission
Astronaut Michael Fincke Busy with a Spacewalk Repair Mission | Source

Daily Life on the International Space Station

For a final review of almost everything I explained, you’ll find this video entertaining as NASA Flight Engineer Cady Coleman discusses daily life on the ISS.2


1. National Geographic Channel - Living on the ISS

2. Video from CBS News Program "The Talk" on January 18, 2011

Questions & Answers

    © 2017 Glenn Stok


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      • Glenn Stok profile imageAUTHOR

        Glenn Stok 

        3 years ago from Long Island, NY

        This morning on March 25th, 2017 American astronaut Shane Kimbrough and French astronaut Thomas Pesquet just completed the first of three scheduled space walks to prepare a second International Docking Adapter.

        The new docking ports will be used for SpaceX and Boeing commercial spacecraft to dock with the International Space Station.

      • Glenn Stok profile imageAUTHOR

        Glenn Stok 

        3 years ago from Long Island, NY

        Sure thing Mary. Without gravity the muscles atrophy and the bones deteriorate if they don't diligently keep up with those exercises.

      • Blond Logic profile image

        Mary Wickison 

        3 years ago from Brazil

        I loved this. A good cross section of videos about living and working on the ISS. Their keep fit routine is interesting and makes you realize just how important gravity is in relation to the pressure it puts on our bodies. Two hours of exercise just to maintain muscle and heart health.

      • Glenn Stok profile imageAUTHOR

        Glenn Stok 

        3 years ago from Long Island, NY

        Good question Dora. I wonder how much they value life when so much can go wrong, being that they are dependent on life-support all the time while in space.

      • MsDora profile image

        Dora Weithers 

        3 years ago from The Caribbean

        What a different kind of life! I wanted to scream "gross" at some of the facts you mentioned, but would not on realizing the purpose for these seeming inconveniences. I bet that the astronauts respect and value life ('normal' or otherwise) much more than the average person.

      • Glenn Stok profile imageAUTHOR

        Glenn Stok 

        3 years ago from Long Island, NY

        Thanks for that informative comment Melody. Stephen Hawking may have a desire to take that trip, but he needs constant attention of health aides to bath him and perform normal hygiene, so I don't think it's feasible. As for trust – Yes indeed. It takes a lot of trust that the other people working on the mission do things right. In 1986, all seven crew members of NASA’s Space Shuttle Challenger were killed when its rocket booster exploded 73 seconds after takeoff. The failed O-ring was not designed for the cold weather conditions during that launch. Anyone could have called off the mission if they were alert to do so. Trust? Yes. Who do you trust?

      • Bedbugabscond profile image

        Melody Collins 

        3 years ago from United States

        I have been following Elon Musk and his dream of taking us to Mars. Then I heard that Stephen Hawking may be taking a trip to space. I never gave what it might be like to live in space much thought until I realized the possibilities of space!

        After reading your informative article. I learned from your informative article that ISS was placed in low orbit around the earth when I was a late teen. I wouldn't have learned about it in school.

        It is amazing the amount of trust that astronauts must place in the technology they use!!

      • Glenn Stok profile imageAUTHOR

        Glenn Stok 

        3 years ago from Long Island, NY

        Yes Louise, With limited resources in space they have to recycle whatever possible. Imagine a trip to Mars that takes two years. Thats would required even more diligence.

      • heidithorne profile image

        Heidi Thorne 

        3 years ago from Chicago Area

        Thanks for the tip, Glenn! Will check it out.

      • Coffeequeeen profile image

        Louise Powles 

        3 years ago from Norfolk, England

        Yes, I learned a lot too. I didn't realise they collected perspiration and sweat too.

      • Glenn Stok profile imageAUTHOR

        Glenn Stok 

        3 years ago from Long Island, NY

        Heidi, you may want to check out "Galactic Unite" – a collaboration between Virgin Galactic and future civilian astronauts.

      • heidithorne profile image

        Heidi Thorne 

        3 years ago from Chicago Area

        In spite of the inconveniences, I so would love a tour on the ISS! Saving my dollars for a possible Virgin Galactic trip. :)

      • Glenn Stok profile imageAUTHOR

        Glenn Stok 

        3 years ago from Long Island, NY

        Thanks for being the first to read and comment CJ, and thanks for sharing.

      • lions44 profile image

        CJ Kelly 

        3 years ago from Auburn, WA

        Great job, Glenn. Very interesting and I learned a lot. Sharing everywhere.


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