sifian_ Posts

That is exactly what I'm saying.

Now... it's possible that we both understand the mechanics perfectly and what we should be arguing over is the submarine geometry. Let's assume that somehow the the exit chamber is formed exactly Takeshi's size/shape. If he exits the submarine and that space is fill with water, it will have almost no effect on the buoyancy of the submarine because the human body is damn near perfectly buoyant against water. This is exacerbated by the fact that the exit chamber will undoubtedly be of greater volume than the person exiting, thus you lose the buoyancy previously offered by the air surrounding Takeshi before he exited.

In order for the net buoyancy to increase, not only does his mass need to be removed from the submarine, but his volume needs to stay within the submarine. This is obviously impossible to achieve in one step, but the same effect can be realized by forcibly extracting the water taken in with a bilge pump.

More jargon that I typed out that's probably not necessary, but I hate to delete it after I typed it. I wanted to spoiler it, but it seems it won't let me nest spoiler tags.

You start with a bucket some depth underwater initially filled with air. This bucket is made out of a material heavier than water. Since the bucket is not sealed, it slowly takes on water and loses air.
This water is definitely considered ballast, and is little different than metal/stone/etc of equal mass. The main (trivial) difference is that 1kg water is very slightly lighter than the sum mass of (1kg stone + the air equivalent to the volume of 1kg water).

At some point once enough water has been taken on, the bucket will cease to be buoyant and will start sinking if it has not reached the surface before then. Thus it is definitely a race to see whether the bucket loses buoyancy or if the bucket surfaces first.

Alignment of the bucket shouldn't matter in this situation- I'm guessing you mention it because you are concerned that alignment will have an effect on the rate of water intake and air loss. This is a real factor, but not especially relevant to the concept in question.

Once the decompression chamber has been flooded, it is completely irrelevant whether or not the exterior door is closed. The whole concept of bouyancy is you are displacing a dense fluid with a volume that has a lesser AVERAGE mass than the fluid it is submerged in.

Yes you can consider that the exposed compression chamber is simply a reduction of the volume of the submarine. However, remember that density is mass/volume. Decreasing the volume while maintaining a constant mass means the average density is increase, and thus more likely to sink. In this case, the loss of one person's mass has a much smaller impact on the bouyancy of the submarine than the loss of the compression chamber's volume.

I'll illustrate this with a scenerio easily visualized. Imagine a 1ft cube of styrofoam encased in a form fitting watertight container. Embedded into this styrofoam is a steel ball 1 inch in diameter. The casing is made out of a very dense material, such that the whole assembly is perfectly neutrally buoyant.

Now remove the steel ball and slice the foam in half. Fill in that space with water. If it makes you feel better, poke a hole in the casing to simulate an open door. Do you think that the object will still float? It won't, because the volume of the light material is significantly reduced such that it can no longer displace enough water to lift the heavy casing.

This illustration is a worse case than the actual submarine, but it's only to express the concept. The actual numbers I listed earier should show that the submarine assembly is less buoyant after Takeshi leaves than before. As I keep saying- unmentioned manual bilge pump fills the plot hole.

You're just not balancing the equation before and afterwards. You're right, there are two chambers, the operational chamber and the decompression chamber.

1)The decompression chamber starts out filled with 1 cubic meter of air, which is slightly more than 1kg.
2)A person enters the decompression chamber from the operational chamber, closes the middle door and opens the outer door... 1kg worth of air and 60kg worth of human leave the submarine while 1000kg worth of water enter. You've now got the same volume object, but it's mass is over 900kg greater than before he jumped ship.
3) The submarine is unpowered, so the normal means of jettisoning the water taken in are likely non-operational. Hence, that's why I say there needs to be a manual bilge pump that tsugumi can operate yet isn't mentioned in the script.

I don't know if such things are standard in a sumbarine. On one hand, it seems like a sensible safety precaution... and on the other hand it's a non-trivial mass which I have no idea how effective it would be in an emergency situation.

First was the ending scene with Sora when Takeshi tells her the story of Pygmalian. The story seems out of place when I played the Tsugumi line initially, but it played out wonderfully in the end.
Second was the Tsugumi/Sara/Kid reunion.

I'm quite confident that the mass of water entering the water/airlock is substantially greater than the mass of one person leaving a submarine. I guess we can pretend there was a manual bilge pump that the writers neglected to mention.