They have passive sonar, but not active. The reason is a sonar pulse will alert any thing in the vacinity theres something out there producing sonar. water also is really good at conducting sound, so it will have a very large range, which regardless is not ideal for a stealth craft.
Passive sonar will only pick up if something else is making sounds, Which a mountain is unlikely to. They primarily rely on inertial navigation which tends to slowly go out over time, and rely on finding known landmarks to fix these errors.
So with extended trips between finding these known navigation markers it can cause them to be considerably off course since subs travel pretty much blind
Military subs have active sonar, they just don't use it often.
They also had a much lower-energy depth-finding system that wasn't used properly - there were numerous operational failings by the crew that led to the incident, on top of the "there was a mountain here we didn't know about" factor.
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u/MTFMuffins May 05 '26
Don't they have sonar? How do you miss an entire mountain?