"We are working on the Kalina project, and the first vessel will have its keel laid after 2020," the source told RIA Novosti.
According to the source, anaerobic propulsion systems do not have enough capacity for the vessel’s engine yet.
"Such a system will be constructed in 2018. Accordingly, after this the boat’s keel will be laid. This will be after 2020," the source added.
Air-independent power plants offer significant advantages over diesel-electric submarines, which need to surface regularly to recharge batteries, and nuclear submarines, which must constantly run noisy pumps to cool their reactors.
The submarines, currently in use by several navies around the world, can stay submerged for weeks at a time.