it is about 110 meters long
A German type VII U-boat could stay submerged for about 24 hours before it had to resurface to replenish its air supply. This air supply could be extended somewhat by limiting activities of the crew while submerged. The type IX could stay submerged for 11 days. The snorkel in 1943 allowed German subs to stay submerged and refresh air. All other US/UK/Jap etc subs could stay down 2 days before having to vent for fresh air and recharge batteries.
The same nations that used them in WWII used them or had them in WWI. Which is a long list!
No. The submarine came about long before the helicopter.
It could take weeks, as mail would first travel by train, then steamship, then another train, before reaching its destination, and that's assuming the ship wasn't sunk by a German submarine.
A nuclear powered submarine can remain submerged for as long as it has fuel rods and supplies for the crew.
A submarine, theoretically, can go as long as the food for its sailors last. A submarine can make oxygen, distill water, remove CO2 and other pollutants, and provide almost anything needed to survive at sea and underwater for nearly an indefinite period of time. Modern nuclear-powered submarines' reactors will last without refueling for the life of the submarine - about 20 years. In 1960, the nuclear-powered submarine USS Triton circumnavigated the globe submerged.
24 hours
A submarine, theoretically, can go as long as the food for its sailors last. A submarine can make oxygen, distill water, remove CO2 and other pollutants, and provide almost anything needed to survive at sea and underwater for nearly an indefinite period of time. Modern nuclear-powered submarines' reactors will last without refueling for the life of the submarine - about 20 years. In 1960, the nuclear-powered submarine USS Triton circumnavigated the globe submerged.
it is about 110 meters long
yes, as long as it was being towed by a submarine.
A foot long submarine sandwich is 0.000189393939 miles long.
A German type VII U-boat could stay submerged for about 24 hours before it had to resurface to replenish its air supply. This air supply could be extended somewhat by limiting activities of the crew while submerged. The type IX could stay submerged for 11 days. The snorkel in 1943 allowed German subs to stay submerged and refresh air. All other US/UK/Jap etc subs could stay down 2 days before having to vent for fresh air and recharge batteries.
Modern submarines are powered by a nuclear reactor. Others are powered by diesel engines while they are on the surface and batteries while they are submerged. The older ones that were powered by diesel and batteries had their limitations. While they were on the surface running on diesel engines they left a trail of exhaust smoke which gave away their position. When they were submerged and running on batteries they could only last so long and then they had to come to the surface, run the diesel engines and recharge the batteries. The submarines that are run by nuclear power do not have to resurface for a very, very long time.
An average submarine is about 300 feet long.
WWII US Gato class subs could be built in 9 months.
No. The submarine came about long before the helicopter.