In WWII, the USS Tang, fired its last torpedo at a Japanese ship in the Formosa (now Taiwan) Straits. The torpedo circled round and sank the Tang.
Could this be a similar incident?
If so, the sound of the torpedo exploding might have been detected.
Could a PLAN (Chinese Communist) submarine have sunk the Indonesian submarine?
Ummm...USN WWII torpedoes were defective for most of the war, a topic of hot debate about navy weapons development, procurement and indifference to warfighters.
I’m unfamiliar with the Tang incident, but the poor souls onboard Nanggala probably succumbed to something similar to that which took out Thresher. No conspiracy needed.
For what purpose?
These were wire-guided torpedoes. I think that’s a different animal than the old WW2 torpedoes that were kind of fire-and-forget. Maybe somebody can amplify on that point.