Uploaded December 2022 | Updated September 2026, 1 week ago
How is International Space Station in orbit, when it is actually in a state of free fall.
The International Space Station, launched in 1998, orbits the Earth once every 90-93 minutes. The speed depends upon it's altitude at that time. It completes 15.5 orbits daily at a speed of 17,500 miles/28,000 kilometers per hour.
It is the largest modular space station in low Earth orbit, and a collaboration between five space agencies. It serves as a scientific research center in a microgravity environment to study astronomy, astrobiology, physics, meteorology and various other fields.
The ISS maintains an average altitude of 400 kilometers or 250 miles above the Earth. But, it is actually in a state of constant freefall. Just like any projectile fired into the air. This free fall gives the astronauts aboard, the feeling of weightlessness.
However, it has enough horizontal speed, that helps maintain it's trajectory and keeps it from falling. Being in low earth orbit, it faces a constant resistance from the thin atmosphere. This is unlike the geostationary satellites that are way above the atmospheric limit.
Due to the atmospheric drag, gravity and other factors, it's speed keeps decreasing. This causes a decrease in its altitude by almost 90 meters every day.
Solar flares also have an effect on the drag, as it can expand the outer atmosphere.
The decrease in speed and altitude is called orbital decay. The decay increases as the altitude decreases. The orbital decay is counteracted in multiple ways. The space station's main rockets can provide small boosts. The resupply vehicles that make regular trips to the space station also provide the required boost.
Without regular boosts, the space station can stay above 280 kilometers for around 700 days. Altitude below 280 kilometers is considered non-operational and will eventually result in the space station coming crashing down.
Major boosts are needed to dodge space debris. The ISS is fitted with advance warning systems for space debris. In case of a threat, the space station's thrusters are fired to change altitude and course.
The ISS was originally planned to stay in orbit for 15 years, and is long past its due date. It is now planned to be brought down in 2031.
How is International Space Station in orbit, when it is actually in a state of free fall.
The International Space Station, launched in 1998, orbits the Earth once every 90-93 minutes. The speed depends upon it's altitude at that time. It completes 15.5 orbits daily at a speed of 17,500 miles/28,000 kilometers per hour.
It is the largest modular space station in low Earth orbit, and a collaboration between five space agencies. It serves as a scientific research center in a microgravity environment to study astronomy, astrobiology, physics, meteorology and various other fields.
The ISS maintains an average altitude of 400 kilometers or 250 miles above the Earth. But, it is actually in a state of constant freefall. Just like any projectile fired into the air. This free fall gives the astronauts aboard, the feeling of weightlessness.
However, it has enough horizontal speed, that helps maintain it's trajectory and keeps it from falling. Being in low earth orbit, it faces a constant resistance from the thin atmosphere. This is unlike the geostationary satellites that are way above the atmospheric limit.
Due to the atmospheric drag, gravity and other factors, it's speed keeps decreasing. This causes a decrease in its altitude by almost 90 meters every day.
Solar flares also have an effect on the drag, as it can expand the outer atmosphere.
The decrease in speed and altitude is called orbital decay. The decay increases as the altitude decreases. The orbital decay is counteracted in multiple ways. The space station's main rockets can provide small boosts. The resupply vehicles that make regular trips to the space station also provide the required boost.
Without regular boosts, the space station can stay above 280 kilometers for around 700 days. Altitude below 280 kilometers is considered non-operational and will eventually result in the space station coming crashing down.
Major boosts are needed to dodge space debris. The ISS is fitted with advance warning systems for space debris. In case of a threat, the space station's thrusters are fired to change altitude and course.
The ISS was originally planned to stay in orbit for 15 years, and is long past its due date. It is now planned to be brought down in 2031.
