>>8588154The Screw on a US Submarine is classified because the design has to be such as for the screw to make as little noise as possible, not cavitate, etc while propelling the submarine.
Getting a decent photo of the screw means you can reverse engineer it, reproduce it, take it to test labs, and figure out what kind of sounds the screw will make (So you can have passive sonar look for it), and figure out how fast the screw can run without making much noise,
This can be used to determine how fast an Ohio class submarine can go while still being quiet. Which gives you things such as response times, range coverage, etc.
In short, it will tell you a LOT about a submarine you don't want people to know about.
Those who know the best screw shape, tend to be our allies, or generally stable. Those who don't, well, let's not give them a free gift you know what I mean?
It would be like giving Saddam detailed photos of the inside of a nuclear weapons construction facility.
