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Path of object dropped from ISS

  1. May 12, 2015 #1
    An astronaut on a revolving space station releases a wooden spoon out of the satellite, into empty space. Will the spoon fall toward earth ? What will happen next ?
  2. jcsd
  3. May 12, 2015 #2


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    If released at zero relative velocity, it will orbit earth, staying at a constant distance from the station. If given an impulse instead, it will take a different orbit, which may or may not hit Earth's surface (or cause it to enter the atmosphere and either rebound or burn depending on angle of entry I think). There should be some difference though if we take into account the tenuous atmosphere at the station's orbit which may slow down the spoon more (or less) than it does the station, but this would be a long term effect.
  4. May 12, 2015 #3
    I would say the distance will either decrease due to the gravity of the station and the tidal forces of Earth or it will increase due to the tidal forces of Earth, but I'm to lazy to calculate it.
  5. May 12, 2015 #4


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    What do you mean with "revolving"?

    An astronaut is released from the ISS every time the astronaut stops touching the walls. What happens next?
  6. May 12, 2015 #5


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    Well, tidal forces mean differential gravity. So if the spoon is released below the station it will be moving marginally too slow for a circular orbit, which should give it a slightly elliptical orbit with a periodic movement relative to the station I guess. But if released at the same height as the center of gravity of the station, this tidal force is just the difference required for it to orbit at a constant distance on the same path.
  7. May 12, 2015 #6


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    This is the correct answer. It's actually an important phenomenon. You can create a poor man's attitude control system for a satellite by just giving one axis a much larger moment of inertia than the other axes. Not a great attitude control system as you could easily see just by looking at what happens when the satellite moves, but you could keep one side generally pointed at the Earth. (Unless your gravity gradient boom flexes too much in response to temperature differentials and winds up flipping your satellite upside down, which has actually happened before.)
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