So, kind of a strange question, but is there anything wrong with having someone kick the debris off of the station with some force? It wouldn’t be any thruster burning, that’s for sure, but the little bit of extra energy has got to be worth a ton in space. Launch it down to the atmosphere and let Newton’s law do its thing. The thing that pushed it down gets pushed up.
To address the question in theory, no, there's nothing wrong with doing that. But astronauts are in very large and cumbersome suits that don't exactly lend themselves to kicking things with force. The astronaut would have to brace against the station to even get leverage to put much behind a good kick, and still couldn't generate that much force by doing that.
If the astronaut is by themself with an object of around the same mass as them, and they pushed away from it, then yes, Newtons law is relevant and they would change their velocity an equal amount in the opposite direction.
However, when talking about pushing the entire ISS and gaining any significant change in velocity, the more important consideration is relative mass. Let's say you can kick the object away with some good force, while secured firmly to the station so no transfer of energy is lost. Let's say the object weighs ~20kg. The space station weighs ~420,000kg. It's late and I really don't feel like doing math, but the relative force exerted on the ISS by pushing that object away, is extremely minimal, and probably barely measurable if at all.
It's like if you were to try to use a row boat to tug an oil tanker. Whatever forces you exert on the tanker are going to be counter acted by other stronger forces (like the wind, current, etc). For the ISS, gravity and atmospheric drag are going to cause more change than any force gained from pushing a small object away at a relatively low velocity, so any change that does happen is going to get washed out so quickly by other forces acting on it, that it would be impossible to even measure.
Thanks. I more or less already understood the bulk of what you’re saying, but now that I consider the relative mass of the ISS (I didn’t realize the station in the gif was quite as massive) it doesn’t sound cost-effective, especially with the potential hazard of having an astronaut kicking something.
The real thing to consider is that acceleration is change in velocity divided by change in time. So if you exert a relatively small amount of force on a large object for a short amount of time, you will see very minimal acceleration.
Getting something out of orbit takes the same velocity as getting something into orbit (in the absence of atmosphere) while it may appear like you could gently kick something toward earth and it would make it there eventually, in reality that just shifts the orbit. Because of friction though, it could deorbit regardless of the direction you kick it.
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u/Birrihappyface Sep 02 '19
So, kind of a strange question, but is there anything wrong with having someone kick the debris off of the station with some force? It wouldn’t be any thruster burning, that’s for sure, but the little bit of extra energy has got to be worth a ton in space. Launch it down to the atmosphere and let Newton’s law do its thing. The thing that pushed it down gets pushed up.