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Why don't we ever see astronauts on space walks, or floating 'weightless' in the ISS, adjusting their orientation by rotating their arms like we do instinctively when about to lose our balance and fall backwards head over heels. Would it work? How about adjusting one's orientation by rotating a hand in a circle over one's head and/or moving a hand in a horizontal circle in front of one's chest and consequently one's body rotating the opposite way around a vertical axis? Or by twiddling one's thumbs for a very long time?

I'm thinking that conservation of angular momentum should make this work. It would be a great physics lesson to see it, if it worked.

Could a space ship be turned around by the crew running or walking in a circle inside it? How about by a crew member sitting on the outside of the ship and whirling a mass on a long string?

Qmechanic
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Matthew Christopher Bartsh
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1 Answers1

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We do not see astronauts in the ISS adjusting their orientation by rotating their arms , because it is much simpler to rotate themselves by pushing off the walls of the compartment, they are in. Rotating themselves, using just their body and arms is much more strenuous and hence not very efficient.

But it can be done, somewhat like how a cat rotates itself while falling using just the contortions of its body. You can see an astronaut demonstrating how he can rotate himself in space in this video https://youtu.be/VJcno_XL4RU?t=43

Even better example is this video as suggested by OP in comments https://youtu.be/7ZPVg3qD07g?t=127

Regarding if the spaceship can be turned around by its crew walking and running around, of course theoretically it can be done. But obviously, the scale and mass of the spaceship compared to that of a few humans makes it nearly impossible to do in practice.

silverrahul
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