There are many common misconceptions related to weightlessness on the International Space Station. Some of these misconceptions include that there is no gravity in space, that there is no gravity in a vacuum, and that the ISS is too far away from the Earth to experience gravity. All of these misconceptions can be proven false through an understanding in centripetal forces. Satellites––including the ISS, the moon, and communication satellites––experience massive orbital velocity.
We can calculate the centripetal acceleration of the ISS. The ISS has an average altitude of 330 to 430 kilometers from the Earth's surface. This added to the 6,371 km radius of the Earth is an orbit where the radius is approximately 7000 km. The average velocity of the ISS is 7660 meters per second. Using the formula Ac=v^2/r, we can calculate that 7660^2/7000 results in a centripetal acceleration of 8,382 m/s^2.
We can also use the tangental velocity of the ISS to calculate how often the ISS completes one revolution around the Earth. If we assume that the radius of the ISS's path is approximately 7000km (or 7,000,000 meters), we can calculate that 14,000,000π results in a circumference of 48,982,300 meters. If the ISS is traveling at 7660 m/s, that means that it completes one orbit around the Earth every ~6395 seconds, or about every 90 to 100 minutes. This is very fast, however, we still have not determined the forces that act on the astronauts inside of the ISS.
The incredibly high orbital velocity of 7660 m/s at a radius of 7000 km is just enough so that the forces of gravity are counteracted. The ISS's tangental velocity of 7660 m/s while experiencing microgravity (about 90% of the gravity experienced on the Earth's surface) causes a downward acceleration of 8.8m/s^2. If we calculate the inverse sine of (-8.8/7660) the result is θ=0.065823º. This angle is so shallow that the ISS is able to fall towards the Earth continuously while it moves along the path of its orbit without getting closer to the Earth. Because we normally manipulate gravity as a downward force, we are not accustomed to the direction of gravity being towards the center point of the orbit rather than in a single downward direction. Because gravity "follows" the relative motion of the ISS, it maintains orbit.
Essentially, the Earth curves away from the ISS just enough so that the ISS maintains orbit. The force of gravity only minutely deviates the centripetal acceleration from the tangental acceleration. This minuscule angle is small enough that the curvature of the earth compensates so that the ISS can maintain orbit. This constant free fall around the Earth is what causes astronauts to experience weightlessness. The term "microgravity" is often used by astronauts to refer to this experience as gravity is still acting on the astronauts while they accelerate with the space station and experience weightlessness. This perpetual free fall state is made possible by the curvature of the Earth.
https://www.universetoday.com/95308/why-are-astronauts-weightless-in-space/
https://youtu.be/hYf6av21x5c
We can calculate the centripetal acceleration of the ISS. The ISS has an average altitude of 330 to 430 kilometers from the Earth's surface. This added to the 6,371 km radius of the Earth is an orbit where the radius is approximately 7000 km. The average velocity of the ISS is 7660 meters per second. Using the formula Ac=v^2/r, we can calculate that 7660^2/7000 results in a centripetal acceleration of 8,382 m/s^2.
We can also use the tangental velocity of the ISS to calculate how often the ISS completes one revolution around the Earth. If we assume that the radius of the ISS's path is approximately 7000km (or 7,000,000 meters), we can calculate that 14,000,000π results in a circumference of 48,982,300 meters. If the ISS is traveling at 7660 m/s, that means that it completes one orbit around the Earth every ~6395 seconds, or about every 90 to 100 minutes. This is very fast, however, we still have not determined the forces that act on the astronauts inside of the ISS.
The incredibly high orbital velocity of 7660 m/s at a radius of 7000 km is just enough so that the forces of gravity are counteracted. The ISS's tangental velocity of 7660 m/s while experiencing microgravity (about 90% of the gravity experienced on the Earth's surface) causes a downward acceleration of 8.8m/s^2. If we calculate the inverse sine of (-8.8/7660) the result is θ=0.065823º. This angle is so shallow that the ISS is able to fall towards the Earth continuously while it moves along the path of its orbit without getting closer to the Earth. Because we normally manipulate gravity as a downward force, we are not accustomed to the direction of gravity being towards the center point of the orbit rather than in a single downward direction. Because gravity "follows" the relative motion of the ISS, it maintains orbit.
Essentially, the Earth curves away from the ISS just enough so that the ISS maintains orbit. The force of gravity only minutely deviates the centripetal acceleration from the tangental acceleration. This minuscule angle is small enough that the curvature of the earth compensates so that the ISS can maintain orbit. This constant free fall around the Earth is what causes astronauts to experience weightlessness. The term "microgravity" is often used by astronauts to refer to this experience as gravity is still acting on the astronauts while they accelerate with the space station and experience weightlessness. This perpetual free fall state is made possible by the curvature of the Earth.
https://www.universetoday.com/95308/why-are-astronauts-weightless-in-space/
https://youtu.be/hYf6av21x5c
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