The title refers to the idea of a submarine going silent so it can't be tracked by sonar. In early drafts of the screenplay, the hero wanted to do something sim

The title refers to the idea of a submarine going silent so it can't be tracked by sonar. In early drafts of the screenplay, the hero wanted to do something similar with the Valley Forge, so he painted the ship black and tried to hide, knowing that Earth would come looking for it. That idea was abandoned but the title remained.