why ISS International space station is not falling down
A space station, like the International Space Station (ISS), remains in orbit around Earth due to a delicate balance between its forward velocity and the gravitational force pulling it toward Earth. This balance is maintained in the microgravity environment of space. Here's how it works:
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Orbital Velocity: When a spacecraft, like the ISS, is launched into space, it is given a high initial velocity. This velocity is known as orbital velocity. It is carefully calculated so that the spacecraft travels horizontally at a speed that counteracts the curvature of the Earth. This creates a continuous "falling" motion around the Earth.
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Gravitational Pull: While the ISS is in orbit, it is indeed affected by Earth's gravitational pull. However, because of its high velocity, the ISS falls around the Earth rather than directly toward it. In essence, it is constantly in free fall, but its forward motion prevents it from getting any closer to the surface.
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Microgravity Environment: The microgravity environment experienced by astronauts on the ISS is a result of the continuous free-fall motion. Objects inside the space station and the astronauts themselves are also in free fall, which creates the sensation of weightlessness.
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Low Air Resistance: At the altitudes where the ISS orbits, there is a thin atmosphere, but the air resistance is minimal compared to the velocity of the spacecraft. This allows the ISS to maintain its orbital velocity and continue orbiting without slowing down significantly.
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Orbit Adjustments: Over time, the ISS's orbit can be affected by factors like atmospheric drag and the gravitational influence of the Moon and the Sun. To counteract these effects and maintain its proper orbit, the ISS periodically performs orbit adjustments using onboard thrusters.
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Altitude Maintenance: The ISS orbits at an altitude of approximately 400 kilometers (about 250 miles). This altitude strikes a balance between being close enough to Earth to feel Earth's gravitational pull and being far enough away to have a longer orbital period.