This type of ship was first introduced in the early 1960s, and already there have been three generations of such ships, while the fourth generation is expected .
Olu hlobo lwenqanawa yaqala ukuvezwa ekuqaleni koo1960, kwaye sele kukho izizukulwana ezithathu zeti nqanawa, ngexa isizukulwane sesine silindelekile.