The 28,000 km/h Ballet: How the ISS Stays Afloat in Space

India.com

2 days ago

International Space Station- File image
The International Space Station (ISS) travels around Earth at an incredibly fast speed of about 28,000 kilometers per hour. Because of this speed, it goes all the way around the planet in just about 90 minutes. This quick movement is what keeps the ISS in a stable path around Earth, called low Earth orbit. Here, the speed of the ISS and the pull of gravity work together perfectly, so the station doesn't fall back down to Earth.
Because the International Space Station (ISS) moves so fast, astronauts onboard get to see many sunrises and sunsets in a single day. In 24 hours, the ISS circles Earth about 16 times, so the crew sees the Sun rise and set roughly every 45 minutes. This fast speed isn't just by chance—it's based on the rules of how objects move in space, called orbital mechanics. Moving at this speed keeps the ISS in a steady path around Earth and helps save fuel, since fewer adjustments are needed to stay in orbit. How Orbital Speed Works
To stay in a steady orbit, the International Space Station (ISS) needs to keep a perfect balance between two forces—gravity pulling it toward Earth and its forward motion trying to carry it ahead. The ISS orbits about 400 kilometers (or 250 miles) above Earth, where there is very little air to slow it down, though a tiny bit of air resistance still exists. Even at this height, Earth's gravity still pulls strongly on the ISS. But because the station is moving forward so fast, it doesn't fall straight down. Instead, it keeps 'falling' around the planet in a curved path—this is what keeps it in orbit.
This idea can be best understood using Newton's first law of motion, which says that something moving will keep moving unless something else stops or changes it. The International Space Station (ISS) is moving very fast, and Earth's gravity is constantly pulling it toward the planet. But because it's moving forward at just the right speed, it doesn't fall straight down—it keeps going around Earth in a steady path.
This same rule also explains how other satellites stay in orbit and how the Moon keeps moving around Earth without falling. It's all about balancing forward motion with the pull of gravity. How Gravity Keeps Objects in Orbit
Gravity is very important in keeping the International Space Station (ISS) in its proper path around Earth. If the ISS were not moving, or moving too slowly, gravity would pull it down, and it would fall back to Earth. On the other hand, if it went too fast, it could fly away into space, escaping Earth's pull.
That's why the ISS travels at just the right speed—about 28,000 kilometers per hour. This perfect speed helps it stay in a steady orbit, where gravity pulls it toward Earth, but its forward motion keeps it from falling. It's like a perfect balance that keeps the station circling the planet safely.
To keep the space station at the right height above Earth, small adjustments are needed from time to time. Even though the ISS is very high up, there is still a tiny amount of air that slows it down a little. This causes the station to slowly lose height—a process called orbital decay.
To fix this, the ISS uses its engines to give a small push, called a 'reboost.' These reboosts help the station move back up to its proper height. Without these regular boosts, the ISS would keep dropping lower and eventually need help to stay in orbit. What Speed Feels Like for Astronauts on the ISS
Even though the International Space Station (ISS) is moving at a very high speed, astronauts inside don't feel like they're speeding through space. That's because they are in a microgravity environment, where everything—including the station and the people inside—is falling around Earth at the same speed.
Since the astronauts and the ISS are moving together at the same speed and direction, there's no feeling of speeding up or slowing down, like you would feel in a car or airplane. This is why astronauts feel weightless and don't notice the motion, even though they're flying around the planet at 28,000 kilometers per hour.
One way astronauts can sense that the space station is moving is by looking out of its windows. From there, they can see Earth's surface—continents, oceans, and clouds—rushing past beneath them. Because the ISS is moving so fast, any place they saw just an hour ago is already far behind.
This quick movement also means astronauts see the day turn into night—and back to day—many times in a single day. It gives them a special view of how Earth moves and what space travel really feels like. Saving Fuel and Making Orbit Corrections
Keeping the International Space Station (ISS) moving at high speed in space takes careful planning and constant monitoring. But unlike airplanes, which need their engines running all the time to fly through the air, the ISS doesn't need to keep using fuel to stay in motion.
Thanks to Newton's laws of motion, once the ISS is moving in space (where there's no air to slow it down), it keeps going on its own. It only needs small engine boosts now and then to make tiny changes, like correcting its path or adjusting its height. This helps save fuel while keeping the station in the right orbit.
To keep the ISS on the right path, small changes to its position are made using its own thrusters and with the help of visiting spacecraft. One example is Russia's Progress cargo ship, which can dock with the ISS and give it a gentle push to raise its orbit.
These controlled boosts help the station stay at the right height above Earth. This method uses fuel wisely and helps the ISS stay in space for a long time without needing too much energy. Difficulties of Docking While Moving at High Speed
When a spacecraft gets close to the International Space Station (ISS) to dock, it has to match the station's speed very accurately. If the speeds or directions are even slightly off, the docking might fail or, worse, cause a crash.
To prevent this, the approaching spacecraft slowly speeds up or slows down to move in the same way as the ISS. This careful matching of movement helps the two connect safely while both are flying through space at high speed.
Even though the International Space Station (ISS) moves at a speed of 28,000 km/h, it doesn't look that fast when another spacecraft gets close to it. That's because both are moving together at nearly the same speed. When it's time to dock, the spacecraft approaches the ISS very slowly—usually just a few centimeters per second. This slow and steady approach helps make sure the docking is safe. Modern navigation systems and automatic controls handle most of the work, but astronauts are always ready to step in and take control if needed. How High Speed Affects Scientific Research on the ISS
The fast movement of the ISS helps it stay in a steady orbit around Earth, which is perfect for doing science experiments in microgravity (near weightlessness). Scientists from different fields use this special environment to study things like how the human body works, how liquids behave, how materials react, and much more.
Because the ISS moves in a regular, repeating path, it's easier to run long-term experiments that would be hard to do on Earth, where gravity affects everything. This makes the space station a valuable lab for learning new things in space.
Biological experiments on the ISS help scientists understand how living in space affects the human body over weeks or even months. This shows how our bodies adjust to life without gravity.
In the same way, material science experiments also benefit, as they can test how different materials and parts behave in space, without the effects of Earth's gravity. Because the ISS moves at just the right speed, it stays in a steady orbit, giving scientists a stable place to run these important experiments without any breaks. Summary
The speed of the ISS shows us how objects can stay in a steady orbit around Earth in low space. This helps us understand the basic rules needed to keep space stations working properly.
As space agencies and private companies plan for new space stations, Moon missions, and even trips to other planets, the experience gained from running the ISS gives them valuable knowledge. What we've learned from the ISS will help guide and support these future space projects.
——- E.O.M
(Girish Linganna is an award-winning science communicator and a Defence, Aerospace & Geopolitical Analyst. He is the Managing Director of ADD Engineering Components India Pvt. Ltd., a subsidiary of ADD Engineering GmbH, Germany. Contact: [e-mail])