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'Interstellar' physics flub. * Spoiler Alert *?
This post contains movie spoilers. Don't read if you have not seen the movie.
The situation is, the circular 'mothership' Endurance has been damaged by a collision with another craft attempting to dock, and is set into a flat rotation on its (supposed) radial axis. In fact, a substantial portion of its circumference and mass has been lost. The remaining spacecraft attempts a 'spinning dock' by matching the axial rotation of the main craft.
In the film, the main ship is spinning precisely around its central axis, at which the docking bay is located. Without the balanced mass around its circumference this would not be possible. The moment of inertial would have been displaced away from the center due to the loss of part of the ship. If the ship was to go into a spin, the docking bay would follow a wildly eccentric spiral path. That does not even consider the possible precession that could occur due to the off-axis forces in the collision.
In order to dock, the passenger craft would not only have to match the rotation rate, which it does in the film, but it would have to somehow keep its docking bay aligned to the same eccentric spiral while consistently maintaining the exact same spin rate. No matter what kind of computer was in control, there is no way a ship of that mass would react quickly and precisely enough to accomplish that.
Am I incorrect?
Sorry, I'm confusing moment of inertia with center of mass, but the principle of my argument is the same. Neither object is likely to rotate around the center of its docking bay, unless the center of mass is precisely aligned at that axis.
3 Answers
- 6 years agoFavorite Answer
Alex - wrong. Gravity has nothing to do with the intrinsic property of mass that causes inertia present in all matter. Just because objects are in free fall, like everything in the International Space Station, it doesn't mean that refrigerator size objects are as easy to push around as a feather. Yes, you can start and stop them moving with the touch of one finger, but the refrigerator would take longer to start to move because of its greater mass.
In the same way, the docking sequence in Interstellar is ludicrous because the damaged Endurance ring is off-balance and there would be no on-axis docking port for Coop to line up with and then start rotating to match. It would look like a horribly out of balance washing machine tub.
- The Black HoleLv 67 years ago
The moment of inertia has nothing to do with gravity. If you place the axis of rotation on the outside of a wheel, then spin it on that axis, try following the center of the wheel. If the center of mass is not exactly aligned to the center of the docking port of the docking craft, you will get an eccentric wobble. Now try matching the eccentric wobble of one object with the eccentric wobble of another. Ridiculous.
- 7 years ago
yes you're incorrect, they are in space. no gravity meaning the docking station will just keep spinning and all the other ship has to do is match that spinning then attach
