Originally Posted by
Richard Dangle
Just to put a little more meat on what TS already posted...submarines are normally passive on patrol. An inert uncharted object is therefore undectable, so no concerns from that perspective.
If it was emitting any sort of noise, or was a charted feature, everything changes. Unlike on the tele prog "Vigil" (unmitigated 100% unwatchable, unforgivenly insane, infantile f******** horse manure) submarines do not surface under Bulk Carriers (or if they ever do someone is losing their command and getting Court Martialed).
Adding even more meat…
Passive sonar is the norm for U.S. subs during all operations (including surface ops). Active sonar is reserved for training and ice ops. However, passive sonar has its limitations; e.g., degrades with speed or poor environmental (acoustic) conditions.
The fact that there were injuries indicates the sub was operating with significant speed.
While subs can measure depth of water under the keel using a fathometer (a routine exception to passive ops), such measurement suffers from the same limitation as the older aircraft GPWS systems; i.e., it can only look down, not ahead. I suspect the SCS is well surveyed with very few uncharted bottom features.
Regarding the comment about surfacing under bulk carriers, large vessels can be extremely difficult to detect using passive sonar due to an effect called a bow null.
The San Francisco collision was due to navigating by incomplete charting data. Back in 1977, the USS Ray collided with the sea bottom due to gross navigational error while operating in the Med. Anyone remember Omega?