Expert: Paul Soderman - 5/19/2002

Question
Hello.  I am attempting to help my 6th grade daughter write a report on how a submarine works.  I have been searching on the Internet for a couple of days now, and I am lost.  I was not very good in school, expecially Science.  The sites that I have found that tell how a submarine works are Greek to me.  I can't even understand the wording.  I feel foolish.  I am not stupid, just scientifically challenged.  Could you please explain to me in the easiest way to understand how a submarine works?

Thanks.

Joanne

Answer
Hi Joanne
This is a little out of my area - I work with aircraft rather than submarines... but they are remarkably similar.  A submarine is an underwater vehicle that, when neutrally buoyant, can remain at depth.  That is to say - it's weight is equal to that of the water it displaces.  (Remember Archimedes ?)  It can change buoyancy by venting air and sinking or filling tanks with air to rise. It can also move upward or downward by changing the angle of fins when the rear propellers are pushing the boat forward.  As the boat descends, the water pressure increases and squeezes the boat. Go to deep, and the boat will be crushed.

In the old days, submarine motors ran on batteries when they had to be quiet and had to surface and run diesel engines to charge the batteries from time to time - a real disadvantage during war.  They also ran out of air in time.  Modern submarines run on nuclear power and can stay down as long as the crew can stand it I assume, although it seems like they would have to replenish their air supply in time (unless they can get oxygen from sea water). There is a whole science involved with submarine communication and detection of things around it - active and passive sonar, etc.

I might recommend a good book (also a movie):  Hunt for Red October by Tom Clancy or Das Boot (an unforgetable movie about a German submarine - not sure if it is a book).  Hope this helps.

Paul