Would you believe the first submarine was basically a rowboat with a roof?
It’s true!
It was built 400 years ago out of wood and leather, and could stay underwater for up to 3 hours!
Of course, submarines have changed a lot since then.
So here's a curious question...
How long can submarines stay underwater?
Well, it depends on how they are powered.
Let’s look at diesel-electric subs first. They have two separate power sources – diesel engines...
diesel engines
and batteries.
batteries
The batteries power the propellers when the sub is underwater, but when the batteries run out of power, the sub switches over to its engines for an energy source.
But there’s a catch.
The engines can't burn the diesel fuel unless there’s a supply of oxygen. So the submarine must first go to the surface.
The engines can now be used to keep the sub moving and at the same time, top up the power in the batteries.
Now, nuclear-powered submarines are different. They can stay down much longer – because nuclear fuel lasts a long time.
And unlike diesel engines, nuclear power doesn't need any oxygen. This means nuclear-powered subs could stay underwater for up to 25 years – except for one small detail – the sub only has room for a limited amount of food.
So, the crew has to go back to port every 3 to 6 months to restock the cupboards!
Let’s recap...
Diesel-electric subs resurface every few days to charge their batteries.
And nuclear-powered subs resurface every few months for food.
Otherwise they could stay underwater for up to 25 years!
Got it?
Great – another curious question answered!