The International Space Station

Right now, this very second, there is a house flying over your head. It is not attached to anything. No pillars, no wires, no balloon holding it up. It is racing around the whole world with real people inside, eating breakfast, doing somersaults, and looking down at you.

It is called the International Space Station, and it is the biggest thing humans have ever built in space. Astronauts have lived aboard it every single day for more than twenty-five years. That means that for your entire life, there has never been one moment when every human being was on Earth. Someone has always been up there.

This book will tell you its secrets: why astronauts sleep strapped to walls, how yesterday's sweat becomes today's drinking water, why flames turn into tiny glowing balls, and how kids just like you have talked to astronauts using radios in their classrooms. Best of all, on a clear evening you can walk outside and see the station with your own eyes, gliding across the sky like a bright, silent star. Ready? Take a deep breath and hold on tight. We are going up.

How big is a house in the sky? Bigger than you might think. From one end to the other, the International Space Station stretches about 109 meters, which is longer than a football field, including the end zones. If it could land in a stadium, its edges would hang over the stands.

It weighs about 420,000 kilograms, roughly as much as 320 cars stacked together. Inside, there is more room to float around than in a six-bedroom house. It has two bathrooms, a gym, science labs from America, Russia, Europe, and Japan, and the best window seat in the universe: a dome called the Cupola with seven windows, where astronauts float and watch the whole Earth turn beneath their noses.

Outside, eight enormous solar panel wings catch sunlight and turn it into electricity. Spread out, those panels would nearly cover a whole acre, about the size of eight basketball courts. They slowly tilt and turn to face the Sun, like giant golden sunflowers. All that power runs the lights, the computers, the air machines, and yes, the coffee maker. Even in space, grown-ups really want their coffee.

The space station is not just big. It is astonishingly fast. It zooms along at about 28,000 kilometers per hour. That is nearly eight kilometers every single second. Blink, and it has traveled farther than you could walk in two hours. At that speed, you could fly from New York to London in about twelve minutes.

Why so fast? Here is the secret: the station is actually falling. Gravity pulls it toward Earth all the time, but it is moving sideways so quickly that as it falls, the round Earth curves away beneath it. So it falls and falls and never lands. Scientists call this an orbit. It is like being on the world's longest, gentlest roller-coaster drop, forever. That endless falling is exactly why astronauts float. They are not far from gravity. They are just falling with their house.

Going this fast, the station circles the entire planet once every ninety minutes or so. That means astronauts see about sixteen sunrises and sixteen sunsets every day. Imagine brushing your teeth at sunrise, and seeing another sunrise before lunch, and another, and another. Astronauts say they never, ever get tired of watching.

Here is something amazing: no single country built the space station. Fifteen countries did it together. The United States, Russia, Canada, Japan, and eleven countries in Europe all made pieces of it, in factories thousands of kilometers apart, on opposite sides of oceans.

The very first piece was a Russian module called Zarya, which means sunrise. It blasted off on a rocket in November 1998, all alone, an empty room circling the Earth and waiting for friends. Two weeks later, an American space shuttle carried up a module called Unity, and astronauts joined the two pieces together. A Russian room and an American room, bolted side by side, became the start of one shared home.

Think about how tricky that was. The pieces were built in different countries, by people speaking different languages, using different tools. Most of the parts never touched each other on Earth. They met for the very first time in space, moving at 28,000 kilometers per hour, and they had to fit perfectly on the first try. And they did. It was like mailing puzzle pieces from all over the world and having them click together in midair.

Building the station took more than ten years and more than forty rocket and space shuttle flights. Each flight carried up another piece: a laboratory, a sleeping area, a giant metal backbone called a truss, or a new set of solar wings. Piece by piece, the station grew like the biggest LEGO set ever imagined.

But here is the wild part: the whole construction site was moving the entire time. Astronaut builders in bulky white spacesuits floated outside, bolting pieces together while flying around the planet every ninety minutes. They used power tools with special grips, and every wrench and bolt had its own little leash, because a dropped tool in space does not fall down. It just floats away and becomes a tiny satellite.

Astronauts spent hundreds of hours spacewalking to connect cables, tighten bolts, and unfold the solar wings. Robotic arms lifted the heaviest pieces and held them steady, gentle as a crane operator threading a needle. When the main construction finished, humans had built something the size of a football field, in a place with no ground, no air, and no gravity to stand on. Builders on Earth are still jealous.

Here is a secret most grown-ups do not know: you can see the International Space Station with your naked eye. No telescope. No binoculars. Just you, looking up at the right moment.

The station is one of the brightest objects in the night sky, sometimes outshining every star and planet, because its huge solar panels reflect sunlight down to your eyeballs. The best time to look is just after sunset or just before sunrise, when your sky is dark but the station, way up high, is still catching the Sun. NASA runs a free service called Spot the Station that tells you exactly when it will pass over your town, down to the minute.

When it comes, here is how to know it is really the station: it looks like a bright star gliding steadily across the sky, taking a few minutes to cross from one side to the other. It does not blink. Airplanes blink; the station does not. It does not zigzag or make any sound at all. And here is the part that gives people goosebumps: there are humans inside that moving light. Wave at them. Seriously. Astronauts love knowing people are watching.

When bedtime comes on the space station, nobody lies down, because there is no down. Each astronaut has a tiny bedroom about the size of a phone booth, and inside it a sleeping bag is strapped to the wall. Astronauts zip themselves in, floating upright, and drift off to sleep standing up, lying sideways, or even attached to the ceiling. In space, every direction feels exactly the same.

There are funny surprises. With no gravity, astronauts' arms float up in front of them while they sleep, like sleepy zombies. Some astronauts wake up confused about where they are, because there is no mattress pressing on their back to remind them. And every bedroom needs a small fan blowing air, because without gravity, warm breath does not rise away from your face. A gentle breeze keeps fresh air moving all night.

Astronauts still keep Earth habits. They brush their teeth, though they swallow the toothpaste or spit into a towel. They read books, call their families, and set alarm clocks. And because the station sees sixteen sunrises a day, they shut their sleeping-cabin doors and pretend, just for eight hours, that night exists.

In space, water does not pour. It floats. If you squeeze water out of a pouch, it gathers itself into a wobbling, shimmering ball that drifts through the air like a tiny liquid planet. Astronauts love playing with water balls. They chase them with straws, catch them in their mouths, and sometimes gently place a floating ball of juice in front of a friend as a surprise snack.

Mealtime is full of clever tricks. Regular bread is banned, because crumbs would float everywhere and get into computers and noses. Instead, astronauts eat tortillas, which hold together nicely. Salt and pepper come as liquids in little bottles, because sprinkled grains would fly away. Most food arrives dried in pouches, and astronauts squirt hot water inside to bring it back to life: macaroni and cheese, scrambled eggs, shrimp cocktail, even brownies.

Dinner is the best part of the day. The crew gathers around a table they do not really need, since the food floats, and they clip their pouches down with velcro and clips. Then astronauts from different countries share their food: Russian soups, Japanese curry, American desserts. Somebody always makes a taco. Somebody always laughs.

Everybody asks astronauts the same question, so let us answer it: how do you go to the bathroom in space? Very, very carefully.

On Earth, gravity kindly pulls everything down into the toilet. In space, nothing falls, so the space toilet uses moving air instead. It works like a gentle vacuum cleaner, pulling everything safely away. For liquid waste, each astronaut uses a personal funnel attached to a hose. For solid waste, there is a small seat with an opening about the size of a dinner plate hole, and astronauts use foot restraints and handholds so they do not float away mid-mission. Yes, the toilet basically has a seatbelt.

In 2020, NASA sent up a brand-new toilet that cost twenty-three million dollars to develop. Why so expensive? Because it has to work perfectly in weightlessness, use hardly any power, fit in a tiny space, and never, ever leak. Engineers tested it again and again, and astronauts helped design it to be comfortable for everyone.

And here is the twist that makes every kid gasp: the liquid waste is not thrown away. It gets recycled into tomorrow's drinking water. Keep reading. We will get there.

Floating looks like fun, and it is. But it comes with a sneaky problem. On Earth, your bones and muscles work all day just holding you up against gravity. In space, they get a permanent vacation, and like anything that stops practicing, they start to weaken. Astronauts could lose bone strength every month if they did nothing.

So astronauts fight back with exercise, about two hours every single day. They run on a treadmill while wearing a harness with bungee cords that pull them down onto the track; without it, their first step would launch them across the room. That treadmill has a funny name: COLBERT. A comedian named Stephen Colbert asked his fans to vote for him when NASA held a naming contest, and he got the most votes, so NASA named the treadmill after him.

There is also a bicycle with no seat, because sitting is pointless when you float, and a machine called ARED that uses vacuum cylinders instead of weights. Astronauts can push and pull against it as if lifting hundreds of kilograms. Thanks to all that sweating, astronauts come home strong. And the sweat itself? The station collects it. Really. That story is coming.

Four hundred kilometers above Earth, there is a garden. It is small, about the size of a suitcase, and it is called Veggie. Inside, plants grow from little pillows of soil under glowing pink and purple lights, which mix red and blue light, the colors plants like best.

Growing plants in space is strange work. Water will not soak downward, roots have no down to grow toward, and seeds could float clean out of their pillows. But plants are clever. Their roots follow the water, and their leaves turn toward the light, and slowly they figure out how to be plants in space.

In 2015, astronauts grew red romaine lettuce and then did something no human had done before: they ate food grown in orbit. They dressed the leaves with a little oil and vinegar and declared it delicious. In 2016, an orange zinnia flower bloomed on the station, and astronaut Scott Kelly floated it up to the Cupola window and photographed it with the blue Earth behind it: the first flower to sightsee from space.

Why grow space salad? Because one day, astronauts traveling to Mars will be too far away for grocery deliveries. Gardens will ride along.

Now for the fact you will tell everyone at school tomorrow. On the space station, almost no water is ever wasted, because almost all of it gets used again and again. The sweat astronauts make while exercising, the moisture in every breath they exhale, even their pee: all of it goes into a machine that cleans it until it becomes fresh, pure drinking water.

Before you say ewww, hear this: the recycled water on the station is tested constantly and is cleaner than the tap water in many cities on Earth. The system spins, filters, and treats the water through many stages until nothing yucky is left. Astronauts joke that today's coffee becomes tomorrow's coffee. And they are completely right.

Why go to all this trouble? Because water is heavy, and launching heavy things on rockets is enormously expensive. Every liter recycled is a liter nobody has to launch. The station's newest equipment recovers about ninety-eight percent of the crew's water, which is close to a perfectly closed loop, like a tiny artificial Earth. That is exactly the point. Our whole planet recycles its water too. Astronauts are just doing it in a very small house, on purpose.

The space station is not just a home. It is the strangest laboratory ever built, because it has something no lab on Earth can offer: weightlessness that never turns off. Scientists call it microgravity, and it changes how almost everything behaves: water, fire, metal, plants, and human bodies.

Here is one example that might save lives. Scientists study tiny things called proteins, the little machines inside every living body. To understand a protein, researchers grow it into a crystal, then map the crystal's shape, the way you might study a building by looking at its blueprints. On Earth, gravity tugs on growing crystals and makes them small and jumbled. In space, without that tugging, protein crystals can grow larger and far more neatly.

Those better crystals help scientists see exactly how a protein is shaped, and that helps them design medicines that fit the protein like a key fits a lock. Research on station-grown crystals has helped scientists working on treatments for illnesses that affect millions of people. Think about that: an experiment floating in a lab above the clouds can end up inside a medicine bottle in your pharmacy. The crew calls it science in orbit, for everyone on Earth.

Light a candle on Earth and the flame stretches upward in that familiar teardrop shape. But the flame is not doing that by itself. Gravity is doing it. Hot air is lighter, so it rises, pulling the flame up into a point and feeding it fresh air from below.

Now light a flame in space, inside a special sealed experiment chamber, and something magical happens. With no gravity, hot air does not rise. So the flame does not stretch. It forms a small, calm, glowing ball, often burning blue, like a tiny sun you could hold in a jar. Astronauts and scientists have burned droplets of fuel in a station experiment rack designed just for studying fire safely.

Then researchers discovered something even stranger: some flames in space kept burning after they seemed to go out. Scientists call them cool flames, fires so faint and cool they are almost invisible, quietly burning in a way nobody had ever seen before. Studying them is not just for wonder. Understanding exactly how fuel burns helps engineers design cleaner engines, and helps keep future spacecraft safe. Sometimes the biggest discoveries come from asking the simplest question: what does a flame do when nothing tells it which way is up?

NASA once ran an experiment that sounds like a storybook. There were two astronauts, Scott and Mark Kelly, and they were identical twins, with matching genes. So scientists tried something clever: send one twin to space for nearly a year, keep the other on Earth, and compare them.

Scott Kelly lived on the space station for 340 days, one of the longest space missions an American astronaut has ever flown. While he floated far above, doctors studied his brother Mark down below. Same genes, different worlds. Any differences that showed up would teach scientists what living in space really does to a human body.

The results were fascinating. In weightlessness, Scott's spine relaxed and stretched, so he returned to Earth temporarily taller than his twin, about five centimeters taller, though he shrank back after landing. Scientists found that spaceflight changed how some of his genes switched on and off, and most of those changes settled back to normal once he came home. His eyes, bones, blood, and even the bacteria in his belly were studied.

Every discovery helps prepare astronauts for longer journeys, like a trip to Mars. And it all started with two brothers and one brilliant question.

Sometimes an astronaut opens a hatch and floats out into space itself, with nothing below their boots but four hundred kilometers of nothing and then the entire Earth. This is called a spacewalk, and it is the most demanding day of an astronaut's life.

The spacesuit is really a one-person spacecraft shaped like a person. It weighs over a hundred kilograms on Earth, and it carries its own air, water, power, and radio. It protects the astronaut from blazing sunlight and freezing shadow. Inside there is a drink bag with a straw, because spacewalks can last six or seven hours, and nobody can come inside for a water break.

Getting ready takes hours. Astronauts breathe pure oxygen first to prepare their bodies, then wriggle into the suit piece by piece while crewmates check every seal. Outside, they clip themselves to the station with steel tethers, and every tool gets its own tether too, because dropped things float away forever.

And remember those sixteen sunrises a day? Spacewalkers see them up close. Every forty-five minutes, day becomes night becomes day, while they calmly turn bolts with the whole glowing planet rolling beneath their feet. Astronauts say no window ever compares.

Astronauts work hard, but the station also knows how to celebrate. The most famous party of all was pizza night. In 2017, an astronaut named Paolo Nespoli mentioned how much he missed pizza, and when the next cargo spacecraft flew up from Earth, the space agencies had tucked in a surprise: complete pizza kits, with flatbread crusts, tomato sauce, cheese, and toppings.

The crew turned dinner into a floating pizza party. They spread sauce very carefully, since a blob of tomato sauce in weightlessness becomes a slow-motion flying saucer, stuck on their toppings, and spun their finished pizzas through the air like delicious frisbees before warming them up and gobbling them down. The photos and videos delighted people all over the world.

Cargo ships bring other treats too: fresh apples and oranges that smell wonderful after months of packaged food, ice cream when there is freezer space, holiday presents from families, and sometimes silly costumes. Astronauts have celebrated birthdays, played floating games, watched movies on a projector, and even brought musical instruments to orbit. A guitar lives on the station, and more than one astronaut has floated by a window at night, strumming quietly while the Earth turned below.

Outside the station lives one of the coolest robots ever built: a giant robotic arm from Canada called Canadarm2. It is about seventeen meters long, longer than a school bus, and strong enough to move pieces of the station as heavy as a loaded truck. Astronauts steer it from inside using hand controllers and video screens, like the world's most serious video game.

But here is the astonishing part: the arm can walk. Canadarm2 has a hand on each end, and either end can grab onto special sockets scattered across the outside of the station. So the arm lets go with one hand, flips end over end, and grabs the next socket, moving across the station like an inchworm the size of a telephone pole. It walks wherever the work is.

Canadarm2 helped build the station, piece by piece. Today it reaches out and gently catches visiting cargo spacecraft, plucking them out of space while both the ship and the station fly at 28,000 kilometers per hour. The arm even has a robot helper named Dextre, a two-armed handyman that can change batteries and fix parts outside, so astronauts can skip some spacewalks and stay cozy inside.

How do you practice spacewalking before you ever leave Earth? You go swimming. Near Houston, Texas, NASA built one of the largest indoor pools on the planet, the Neutral Buoyancy Laboratory. It is over sixty meters long, twelve meters deep, and holds more than twenty-three million liters of water. Resting on the bottom is something incredible: a life-size model of big sections of the space station.

Astronauts put on real training spacesuits and are lowered into the water by a crane. Divers carefully add weights and floats to each suit until the astronaut neither sinks nor rises. Floating like that feels wonderfully close to weightlessness, so astronauts can practice every bolt, every handrail, every careful movement of a spacewalk. For every single hour they will spend outside the station in space, astronauts train roughly seven hours underwater.

And that is only part of the training. Astronauts study Russian so they can work with their crewmates and fly in Russian spacecraft. They practice medicine, robotics, plumbing, and repairs, because in orbit, the crew is the fire brigade, the doctors, and the repair crew all at once. Astronauts say it is like earning ten jobs at the same time.

Here is something that might give you shivers: ordinary kids, sitting in ordinary classrooms, have talked with astronauts on the space station using radio. Not through a TV studio. Directly, their voices flying up through the sky.

It happens through a program called ARISS, which stands for Amateur Radio on the International Space Station. The station carries ham radio equipment, and astronauts love using it. Schools around the world apply for a contact, then spend months preparing, learning about radios, orbits, and space. On the big day, everyone gathers around the equipment and waits for the station to rise above their horizon.

Then comes the magic. The station is only overhead for about ten minutes before it flies onward, so the students line up and ask their questions fast: What does space smell like? Do you dream differently up there? What do you miss most? And an astronaut, floating in a laboratory four hundred kilometers up and rushing by at eight kilometers per second, answers each one by name. Thousands of these conversations have happened since the station's early days.

Somewhere, on some day, a kid asks a question, hears an astronaut answer, and quietly decides what they want to become.

Ask the people who run the space station what the most amazing thing about it is, and many will skip the rockets and robots and say: the teamwork. Fifteen countries have kept a shared house running in space for more than twenty-five years, without stopping, even during years when some of their governments argued down on Earth. Four hundred kilometers up, the crew keeps working together, because in space, you simply must.

Every day, mission control centers around the world take care of the station together: Houston in the United States, Moscow in Russia, Munich in Germany, Tsukuba in Japan, and Saint-Hubert in Canada, where the robot arm experts work. Teams hand duties around the planet like runners passing a baton, so someone is always watching over the crew while they sleep.

Aboard the station, American astronauts speak Russian, Russian cosmonauts speak English, and crewmates from Japan, Europe, Canada, and beyond share meals, jokes, and chores. They trust each other with their lives every single day. People sometimes say the space station is humanity's greatest engineering achievement. Maybe. But it might be an even greater achievement of friendship: proof, sailing over every border on Earth, sixteen times a day.

For its first years, the station was visited only by government spacecraft: space shuttles, Russian Soyuz capsules carrying crews, and sturdy robot cargo ships from Russia, Europe, and Japan. Then something new happened. Private companies started building spaceships too.

In 2012, a company called SpaceX flew its Dragon capsule to the station, the first privately built spacecraft ever to arrive there, loaded with supplies. In 2020, a new Dragon carried astronauts Bob Behnken and Doug Hurley to the station, the first crew ever launched to orbit by a private company. Their families gave the capsule a lucky mascot: a toy dinosaur that floated when they reached weightlessness. Boeing built a crew capsule too, called Starliner, and cargo ships named Cygnus keep the pantry full.

Docking is a masterpiece of precision. Both the station and the arriving ship are streaking along at 28,000 kilometers per hour, yet the capsule creeps in centimeter by centimeter, lining up perfectly until the latches click. It is like two race cars gently touching bumpers at full speed, done with computers, cameras, and years of practice.

Every arrival is a little holiday. The hatch opens, fresh supplies float in, and sometimes there are hugs, mail, and fruit.

On the second of November in the year 2000, a capsule docked with the young, half-built station, and three men floated inside: an American named Bill Shepherd and two Russians, Yuri Gidzenko and Sergei Krikalev. They turned on the lights, warmed up the equipment, and made the station a home. Ever since that day, it has never once been empty. Not for a day. Not for a minute.

Stop and think about what that means. If you are a kid reading this, then humans have been living in space for longer than you have been alive. Your whole life has happened while somebody was floating overhead.

Since then, hundreds of people from more than twenty countries have visited the station: pilots and scientists, doctors and engineers, teachers and, more recently, private travelers. Crews usually stay about six months, keeping the science running and the station healthy before handing the keys to the next crew.

And the science has poured out of it: thousands of experiments, dreamed up by researchers and students in over a hundred countries. Some experiments were designed by kids in school competitions and actually flew to orbit. The station belongs, in a way, to everyone who wonders.

Nothing this wonderful stays forever, and the International Space Station is getting older. The partner countries plan to keep it working until around 2030. After more than three decades of service, the grand old station will finally retire, its mission gloriously complete. But that is not an ending. It is a beginning.

Private companies are already designing new space stations to take its place, with names like Axiom Station, Starlab, Orbital Reef, and Haven. Some may have bigger windows, comfier rooms, and laboratories for even more kinds of science. The dream is that low Earth orbit becomes a busy neighborhood, with several outposts where scientists, and maybe someday ordinary travelers, live and work.

Meanwhile, space agencies are looking farther out. NASA and its partners, many of them the same friends who built the ISS, are working on Artemis missions to the Moon and a small station called Gateway to orbit it. Everything the ISS taught us, from recycling water to growing lettuce to keeping bones strong, becomes the instruction manual for those longer voyages, and someday for Mars.

The station's greatest legacy will not be its metal. It will be everything humans learned while living inside it.

Every astronaut who ever floated through the space station started out exactly like you: a kid on Earth, looking up. They asked endless questions. They read books about space, sometimes under the covers with a flashlight. They did not know all the answers. They just refused to stop wondering.

The space station's story is still being written, and the next chapters need people. Someone has to design the new stations and the ships that visit them. Someone has to grow the gardens that will feed travelers to Mars, write the computer code, study the medicines, fix the robots, and yes, float in the Cupola window watching hurricanes swirl and deserts glow. Why not you? Study what you love, ask big questions, take care of your body, learn to work with people who are different from you. That last one, as you now know, is the real rocket fuel.

Tonight, if the sky is clear, check when the station will pass over your town. Then go outside and watch for a bright, steady star sliding silently across the dark. Inside it, somebody is living the adventure. Wave at them.

And remember: one day, somebody up there might look down, and it might be you waving back.