Based on Density, a submarine can either float or sink. Another term that is used is Buoyancy. Found in between the inner and outer hulls, the Ballast tanks control the ship’s buoyancy. When a submarine is at the surface, its total density is less than the water it floats upon. Another way of describing it is that it has positive buoyancy. It will therefore float. This is because the ballast tanks are mostly full of air. If a submarine has negative buoyancy, its density is more than the density of the water around it. When the vents on the top of the ballast tanks are opened, the incoming seawater from the float ports forces the air out through the vents. Then the submarine starts to sink. When a submarine’s ballast tanks are filled with seawater, its exact depth can be controlled. You can do that by adjusting the ratio of air to water in the ballast tanks. A submarine can reach Neutral Buoyancy. That means that the density of the submarine is equal to the amount of water that it displaces and so it would neither rise nor sink. When the submarine is needed to rise, compressed air is blown into the ballast tanks to force the seawater out. Its density therefore decreases and gains Positive Buoyancy. It rises because without the seawater, the submarine’s density is less than the water that surrounds it. Source: Office of Naval Research: Science and Technology Focus

a. Ballast tank: The ballast tank is the tank that holds the air and/or water which is used to control the density of the submarine. b. Main Vent c. Inner Hull d. Outer Hull e. Flood ports: where the seawater can come into the ballast tanks. DIAGRAM 1: In diagram 1, the main vent of the submarine is closed so the water at the flood ports does not fill up the ballast tanks. [Floating]

DIAGRAM 2 The main vent opens and water is able to replace the air inside the tanks. Submerging DIAGRAM 3 When the submarine is Submerged, the main vent is closed and any adjustment to the ratio of air to water inside the ballast tanks can be made. DIAGRAM 4 When the submarine is needed to rise, compressed air fills the ballast tanks, forcing any water out so the density would decrease.

a. Medicine Bottle –w/ hole at b. Alka-seltzer and water (carbonated) c. Extra mass; pennies a. B water inside c Sub. Model type: Simple and easy

Step one Step two  Take a medicine bottle and poke a hole in it.  Note: Instructions will vary depending on the model that you want to make. This model is the simple and easy one.  Add more mass into the punctured medicine bottle. I used pennies. (approximately 12 pennies would do. Make sure that the medicine bottle is still able to float after you put on the lid.

Step three Step four  Open up the bottle and place a finger over the puncture and fill it up with water. Leave about 2 cm of air at the top.  Now add in the alka-seltzer. Then close the lid quickly. The mass of the water should get it to sink.  That should be self explanatory. You should be done with the submarine.

My submarine can work in 2 different ways. The first way is if you add a large amount of Alka-seltzer to the bottle. When you do that, the large amount kinetic energy would force itself out of the puncture that was made at the bottom of the bottle. The energy would push off the bottom of the surface, giving it a lift. Also when that happens, the water is being pushed out of the bottle. In turn, the mass that was keeping the total density greater than the density of the water, had escaped. Therefore, the bottle should float again because its density is less than the water. The second way is if you add a little bit of alka-seltzer, the escaping bubble would build up under the bottle up until the point that it would be enough to lift the bottle up to the top.

As you can see, there is a bubble forming at the bottom of the bottle. I used a clear container so I was able to take the pictures.

My home result is as followed:  Using the carbonated water (club soda) took the most time in getting it to float. The average time was around 15 minutes.  Using a lot of Alka-seltzer would give you the faster rising time. (I.e. 1 tablet.)  It gives you more force.  Using little amount of Alka-seltzer would take an average about 6 to 8 minutes to float.  The depth of the water that I tested was about 15 cm deep (sink)  I was only able to get it to sink and float once though.

One of the theories that I had thought about was to make it so that the bottle was able to have a release system. What I thought was that if the alka-seltzer was to run out when it reached the top, a hole at the cap would let in air so that the water at the puncture at the bottom would let in more water so that the submarine would sink again. At the top, there should be a piece of alka-seltzer taped to the lid. When the water level reaches there, the alka- seltzer should react, therefore giving of carbonation. Which would somehow help it rise up again. There was a problem with this though. During the first sink/float trial, the carbon escaped through the hole at the top, which was not as I had planned for it to. So I was unable to think of how to improve this idea.