Learn How Astronauts Work Outside The ISS Moving At 17,500 MPH


The International Space Station is orbiting the Earth at the speed of 17,500 mph, and astronauts have to take trips outside the station to perform Extravehicular Activities (EVA). How are they able to work outside the space station moving at such great speeds? If you want to see how hard it is, just imagine you fixing your car while it’s moving on the freeway at full speed.

NASA Astronaut Clayton C. Anderson emerging from the ISS airlock hatch, during a spacewalk in 2007.

When you are inside a vehicle, whether a car or a space station, you are moving with the same speed as that of your carrier. Your speed relative to the vehicle is zero. When an astronaut moves out of the ISS, they are also moving at 17,500 mph, and the relative motion is zero. As a precaution, the spacewalker is also tethered to the station, so they don’t get away. If you crawl out of your car and try to perform an activity on top of it, things will be much different from how they are in space. As opposed to the vacuum in space, there is very high wind resistance and gravity on earth. The wind will also be moving at a 70 mph speed relative to you.

NASA Astronaut Clayton C. Anderson re-entering the airlock at the completion of a spacewalk during STS-131.

Would jumping out of the ISS be the same as jumping out of a car moving at some 80 mph? When a cosmonaut jumps from the ISS, they would be moving relative to the station, and it would be similar to being left behind when you jump off of a car. The absence of gravity and wind resistance, however, makes the experience much different. The physics of outer space called “orbital mechanics” is much different from that on earth. As a standard practice, astronauts are always tethered to the station when they are out on an EVA, but if they were not, they would be left behind but meet the ISS again an orbit later.

An EVA might be similar to jumping out of the car, but in all practical scenarios, the consequences will be much different. After all, the earth is spinning at 1,000 mph, and we do not seem to have any problems.

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