The Whisper Drive is a silent propulsion system for submarines invented by Wilhelm Schmeck. Schmeck planned to sell the plans to the drive to Cuban Naval intelligence however according to Conway Stern the Chinese would pay five times more. The drive itself is a clear homage to the "Caterpillar Drive" from The Hunt For the Red October, which allowed the submarine to operate silently.
In the Season 6 episode, "Three To Tango", it is revealed by Slater that the Whisper Drive Conway stole from Schmeck was a fake.