The Russian Navy's Project 677 Lada-class submarine (Russian: Лада) is a class designed by the Russian Rubin Design Bureau. The class is also referred to as the Petersburg (or Sankt Peterburg or Peterburg) class, after the lead ship. A program to develop a "fourth generation" diesel-electric submarine, it aimed to produce a highly improved version of the Project 636 Kilo class with much quieter, new combat systems, and possibly air-independent propulsion.