Submarines Read the text and answer the questions.
A
submarine is a vessel designed to operate under water for lengthy periods. Because of water pressure, many have a double hull, each made of strengthened steel, that protects crew and equipment. The space between the inner and outer hull provides room for missile-launching tubes, fuel tanks and ballast tanks.
which is then pumped overboard. This prevents air becoming stale and allows nuclear submarines to stay underwater for months. If a vessel can’t surface for some reason, the crew can free themselves through escape hatches at the front or stern of the boat. A computer will tell the crew exactly where they are.
r o e t s Bo r e p ok u S
The periscope is the ‘eye’ of the submarine when it surfaces but is not used a great deal as its range is restricted. Below water, it uses passive sonar to listen for noises generated by other ships, possibly enemy ones. Its active sonar device sends out acoustic (sound) pulses which are measured when they reflect from the seabed, other ships, icebergs etc. and a global positioning system gives the exact location of the objects detected by the sonar device.
ew i ev Pr
Teac he r
To submerge, outside water is pumped into the ballast tanks.The submarine becomes heavier and dives using forward motion and the aid of winglike horizontal hydroplanes on either side of the conning tower and on the stern or bow of the vessel. These planes point down when diving and, in diesel-electric submarines, the diesel engines are shut down and electric motors take over. Smaller tanks are used to control depth. Later, compressed air expels water from the ballast tanks and the vessel rises with the hydroplanes pointing upwards. During wartime, submarines once surfaced at night to expel stale air accumulated inside the ship and take in fresh air. Now, modern vessels use a snorkel tube and a second tube removes the stale air. In nuclear submarines a special machine removes carbon dioxide (CO2) from the air,
For many years a military submarine’s principal attack weapon has been the torpedo, but many modern vessels are now also capable of launching long-distance missiles from the surface or even from an underwater position.
© R. I . C.Publ i cat i ons •f orr evi ew pur posesonl y•
w ww
m . u
1. What safety devices can be used in emergencies? 2. What is used to expel water out of the ballast tanks?
. te
3. Find words in the text that mean: rear, ships, gathered, precisely, position?
o c . che e r o t r s super
4. Why did wartime submarines usually surface at night?
5. What natural feature is a possible danger to submarines?
6. Why is CO2 removed from the air inside a submarine? 7. What do you think it would be like to be confined in a submarine underwater for days on end? R.I.C. Publications®
www.ricpublications.com.au
13
Comprehending our world