Why do submarines have to come to the surface?

Question

Apart from for air

Answer 1

Food!

Answer 2

They come to the surface if they need to scower the surrounding area through a periscope and they need to be near the surface to fire some types of torpedoes, and also to replenish supplies.

Answer 3

So they can hang their washing on the line.

Answer 4

Nukes don't. they stay submerged the whole of the patrol.

Older boats needed to to recharge batteries by running their diesel engines which can only be done on the surface.

Answer 5

Well their are now three types of Submarines you have to Consider

NUCLEAR, DIESEL, AIR INDEPENDENT PROPULSION (AIP)

NUCLEAR: Nuclear  Submarines can stay submerged indefinentley. The only real restriction is food supply, as long as their is food for the crew, or weapons if the boat shoots weapons. Typical Pressurized Water Reactors as used on Submarines have a core life of over 10 years, meaning they get re-fueled roughly every 10-15 years or longer!

DIESEL: Diesel Submarines come near the Surface Periscope Depth (PD) to run their Diesel Engine(s) to charge their Batteries, that are used for submarged operations. The diesel engines require vasts amount of air, more than is carried inside the boat, and also requires to discharge overboard the exhaust. This can be done submerged at PD, but not at deeper depths.

AIP: AIP Submarines have a way of producing energy while submerged to extend the amount of time they can remain submerged before having to come to PD to recharge batteries. I'm not going to get into the versions of AIP, since I do not know what is not classified. But AIP is not a constant use or long term feature eventually all of the stored energy will be used up. So the primary means for AIP submarines to charge their batteries is still the Diesel Engine, which has the same restrictions as a standard Diesel Submarine.

ALL SUBMARINE: They do however come to near the surface, called Periscope Depth (PD). We do this for various reasons, with the main being communications, to copy the messages we need to recieve and transmit ones we need if the situation permits. We also come to PD to ventilate the ship. We do make our own Oxygen (O2), and scrub CO and CO2, but ventilating helps ease wear on this equipment. We also may snorkel, or run our diesel engine for practice or an emergency. Lastley we may come to PD to put a sensor out of the water being the periscope itself, to see observe contacts and see what radio type signals are present.

Answer 6

Food,fuel

Answer 7

they don't have to for 6 months or so would you like to be in a container for that time i think not maybe the sub is solar power ha ha

Answer 8

No, they don't have to come up for air and can run submerged for 6 months.  They do have to come up for supplies like food and toilet paper.

Answer 9

The sub must surface (or cruise just below the surface using a snorkel) to run the diesel engines. Once the batteries are fully charged, the sub can head underwater. The batteries power electric motors driving the propellers. Battery operation is the only way a diesel sub can actually submerge. The limits of battery technology severely constrain the amount of time a diesel sub can stay underwater.

Answer 10

Since most submarines are nuclear powered nowadays they can stay down for months.  The only reasons to surface are for supplies, to use the periscope, to fire weapons (missiles and some torpedoes) and during emergencies.  I believe periscope depth and the depth most weapons are fired at is around 15 ft.

Answer 11

So the people inside can get out without getting wet  LOL

Answer 12

Most Nuclear submarines are designed to be completely submerged for at least 6 months at a time.  The only reason for them to surface is supplies.

Answer 13

All subs need to reprovision stuff like food, toilet paper and other perishables. The other problem is the crew can only stand it so long in that tin can. 3-4 months is the most crews stay submerged. It is do able to resupply while submerged by way of a small rescue sub or by direct docking but this is considered to costly and dangerous for no real gain. The other problem is to rearm requires you to surface as large hatches need to be opened to allow torpedoes and missiles to be loaded aboard.

Answer 14

So the people can get in and out more easily.

Answer 15

to let the thick seamen come ashore..

subs are self sufficent, the make their own drinking water and air is compressed... but they need to replace fresh food regularly... or we get tinned seamen... and thats too nasty to contemplate.

only old diesel boats need to snorkel... modern nuke subs can stay down for upto 3 months at a time. (or longer)

Answer 16

Nuclear powered submarines i.e SSBN that carry trident etc do not need to surface except for  resupplying, they can generate water and recycle air indefinatley, hunter killers SSN can also stay under indefinatley and like the SSBN only need to resupply, SSBN's normally hide deep in the ocean using thermal layers to hide under however if carrying out a missile launch they go shallow then dive.

Convential Diesel electric submarines  again if fitted with a snorkel dont actually need to surface they use an extended tube for supplying air for breathing and also while suing the diesel engines to rechage the batteries, while doing this they "purge" the atmosphere in the boat and they can also be fitted with CO2 scrubbers which can filter the air to allow ofr extended periods underwater

Answer 17

To re-fill with fuel