This was the question that the students had to answer today using only their learned knowledge from their previous research.
Here are some of their answers:
“Submarines use ballast tanks and compressed air. They have a vent at the bottom. To sink, valves at the top open and let water come in through the vent at the bottom and fill the ballast tanks. To float, they open the valves to let compressed air in to force the water out of the ballast tanks.” By Chris.
“A submarine works by having some tanks full of compressed air. If a submarine wants to go down it opens some air vents which allow the air to escape and then it fills up with water which sinks the submarine. But if a submarine wants to return to the surface all it has to do is release the stored compressed air which will push all the water out leaving the tank to have air in it which will cause the submarine to float to the surface.” By Harry.
“A submarine contains ballast tanks in its hull that use compressed air to change the density of the sub. By opening a valve, water fills the ballast tanks with water, thus increasing its density, thus making the submarine sink. If a submarine wants to float, compressed air gets pushed into the tanks, thus pushing the water out making it float.” By Matt.
“A submarine uses ballast tanks filled with compressed air and when needed the air is released and takes on water which increases the density making it sink but when the water is pushed out the sub’s density is decreased making it float.” By Jordan.
It’s Really informative!!
when the rwants the submarine to sink or float all he does when he needs it to sink he opens the valider ve making the water to replace the vaccume which had air in it while the marine sinks becouse the weight has increased and vice versa
thanks alot
i have a question that what happens with that stored air when the submarine was not submerged???
does the air is allowed to let out or is it again stored in the compressed air can..??
and what if due to some technical fault the mechanism gets damaged and the compressed air is not able to come out….,,,will the submarine remain submerged or do they have a secondary mechanism to deal with this situation….?????
Hi Divyanshu,
Thanks for your message.
The stored air remains in tanks compressed so that it can be released as needed to expel the water (to create positive buoyancy). Once it is used from the tanks it can’t be put back in – so it only has a limited use. The submarine captain will need to make sure there is enough compressed air to submerge and float otherwise he will need to return to a base to refill the tanks. The compressed air doesn’t all get used in one go. It would be able to be used a lot of times. Some submarines may be able to draw in more air once it surfaces if it has the technology to compress the air into tanks. I’m not sure about this, though.
If there is a technical fault then there will be a problem. I’m sure they would have some backup systems to help in the event of this problem. They could also radio for help and get assistance from the other naval vessels.
Here is a website which may have some more information – http://science.howstuffworks.com/transport/engines-equipment/submarine1.htm
Mr Lindsay
can we control the amount of water that to be taken into the ballest tanks…?
so that we can control the depth that a submarine should go through…
Hi Guresh,
Thanks for posting a comment.
Submarines use the compressed air to control the amount of water in the ballast tanks which allows the submarine to sink and float. More water – it sinks. More air – it floats. The limit of depth is more about the pressure that the submarine can put up with.
Hope that helps.
Mr Lindsay
Wouldn’t compressed air also affect the bouyancy of the submarine while submerged. After all, air is air whether compressed or not, isn’t it?
Hi Ivan,
Thanks for visiting out blog and posting a comment!
My understanding is that the compressed air is used to expel the water which has flooded the ballast tanks. That would have a signficant effect on the density of the submarine, whereas the compressed air storage probably doesn’t have the same effect.
Hope that helps.
Mr L.
hi…i have a question…. we know that as we go deeper into the sea, the pressure all will start to rise…so what happens to the passenger?…are they affected by the pressure or they still feel the same pressure like us?
Hi Aiman
Thanks for your comment.
The hull of the sub creates a pressure container, so the outside pressure doesn’t affect the inside pressure. Thus, the interior of a submarine is at normal, surface air pressure. The only time that would change is if there’s a leak large enough to displace the air significantly, but if that happened, the submarine is going to be sinking.
Hope that helps.
Mr Lindsay.