subject: What Exactly Is A Ballast [print this page] Ballast is something heavy that is used to hold things down or keep them in place. It can be bags of sand, rocks, lead, and even water. Ballast is very important in ships. If a ship is too light, the wind and waves make it bob around like a cork. So when it is not fully loaded, ballast is placed in its bottom. Balloons use ballast to give the balloonist more control. The ballast is usually bags of sand or water hanging over the side of the balloon. When the balloonist wants to rise higher, he drops some ballast. Racing cars use ballast. The engine at the front is so heavy that weight must be carried at the rear to keep it down. Submarines use water as ballast. When a submarine is about to dive under water, the sailors let seawater enter special tanks. This makes the submarine heavier, and it sinks in the same way a floating bottle sinks when it is filled with water. The water is pumped out when the submarine is about to rise. This makes it lighter and able to float to the surface. Many ships that use oil as fuel (as most ships of the United States Navy and other navies do) are built so that sea water can be pumped into their oil tanks after the oil from those tanks has been used. During World War II, some destroyers that had empty oil tanks, and that were waiting to take on more fuel from oil tankers, sank while they were waiting, because they did not have enough ballast. Rock ballast is used to weight down the wooden crossties on railroad tracks. If they were not weighted, a heavy train clanking along the tracks at high speed, and swaying from side to side, could shift the ties and move the tracks.
