Why do submarines launch without their propellers on?

Not to let others to estimate their unique "acoustic signature" by looking at the propellers design...

They don’t want satellites to photograph them.

*screws (Submarines do not use propellors)

Propellor is the secret sauce of a submarine. When you know the shape, you can predict their acoustic signature.

Because they are top secret.

They are secret.

Except.

Because they have "Caterpillar drive" like in the Hunt for the Red October.

That propulsion is old Stringray had it in 1964

people get so caught up in terminology they miss the engineering logic. install the expensive hardware last so you dont accidentally wreck it while sliding the thing into the sea

Because they need to sink first since it’s a submerged

Just put a false propeller.

水中で付けるの？

Because the propeller is large and delicate - leaving it off protects it from damage during the slide/float-out and makes handling easier. Final mounting, balancing and shaft alignment are often done after the hull is afloat and accessible for sea trials.

Because we can track them .

So they don't escape before you have trained them?

So you don’t see them.

プロペラは最重要機密だからです 撮影されたら困るのですよ

It means there are other subs in the area already.

they don’t actually need the propeller installed to launch. it can be fitted later once the submarine is in the water.

Ancient Chinese Secret

What do you mean without screws? 🤯 It's like a car without wheels - how does it even move?!

Because propeller shape,size and pitch are all classified to each country because everybody has their own design. That’s why whenever you see them above water and they are on they’re always covered up.

Wowsers