https://en.wikipedia.org/wiki/The_Hunt_for_Red_October_(film)#Filming https://en.wikipedia.org/wiki/The_Hunt_for_Red_October_(film... The film caused a minor s

https://en.wikipedia.org/wiki/The_Hunt_for_Red_October_(film)#Filming https://en.wikipedia.org/wiki/The_Hunt_for_Red_October_(film... The film caused a minor sensation in the black projects submarine warfare technology community.[13][14] In one scene, where USS Dallas is chasing Red October through the submarine canyon, the crew can be heard calling out that they have various "milligal anomalies". This essentially revealed the use of gravimetry as a method of silent navigation in US submarines. Thought to be a billion dollar black project, the development of a full-tensor gravity gradiometer by Bell Aerospace was a classified technology at the time. It was thought to be deployed on only a few Ohio-class submarines after it was first developed in 1973.