Do submarines normally run without using sonar so that they can remain undetected?
Submarines have active and passive sonar. Active sends out the loud pinging, and is very very detectable. I believe the use of active sonar is very rare.
Passive sonar simply listens to the sounds in the ocean, and sophisticated computers are used to identify and locate ships, subs, animals, and whathaveyou. There is no pinging involved. I can’t imagine why this would ever be turned off while at sea.
IANASS (submarine sailor), but there are two basic kinds of sonar used by submarines and other ships - active and passive.
Active sonar is basically a PING - that is, sending a sound wave into the water and listening for any returns. Pings are big problems for submarines as the wave can be detected much further off than it can generate reliable results. So pinging can give away your position to an enemy ship and not let you know its position.
Passive sonar is essentially just listening to what’s around you. Passive sonar can be from a sonar array in the hull, or a trailed array at the end of a cable streaming out the stern of the ship. (In movies, guys listening to a passive array would be looking at the green “waterfall” display with big headphones on.)
Passive sonar will give you freqeuncies of the noise in the surrounding water, plus a bearing. Based on the frequencies, a sonarman (or sonarperson) can determine what class of ship is around using the known engine plant frequencies. Blade rate can be determined from the noise, giving a speed. The bearing is used to determine position.
I’m sure a sailor will be along shortly to correct me and fill in the missing details.
Let me rephrase this.
Did the San Francisco run into something because submarines typically to not search the underwater terrain?
They use topographical maps of undersea terrain. The point of being a sub is that no one knows you’re there. If you normally operate with active sonar and all of its associated noise then you’ve defeated your purpose.
The area where the San Fancisco was operating has a number of underwater seamounts. The Navigator should have plotted a course to avoid them. They would not have been using, as has been said above, active sonar or other gear to check on them. The underwater terrain, e.g., these seamounts, is mapped and charted by other units from the Navy, USGS, or other agencies. Given these charts, and a good position fix, you shouldn’t need any active sonar to avoid grounding.
dasgupta pretty much hit the nail on the head with his sonar explanation. Underway, passive sonar is always in use and manned, without exception. Considerations such as the likelihood of counterdetection (and consequences of counterdetection) will determine the use of active sonar. As mentioned, active sonar is easily intercepted from a distance well in excess of the system’s useful range. (After all, each ping must travel to the target and the return must make it all the way back to the active platform.)
As Grey mentioned, we drive using nautical charts just as any other seagoing vessel would.
Probably. The reports are that the incident happened 350 miles south of Guam. In that region, there are a number of undersea ridges that rise up, several topped by islands or atolls. It is probably a good place to train for underwater maneuvers to avoid just this sort of problem. And, of course, when training, one always risks failing to accomplish one’s task.
(If you drag out a map of the Pacific and put a straightedge across Palau (to the west) and Truk (to the east), you will have a rough idea of where they were at the time.
There will be several boards of inquiry, and possibly an investigation by non-military authority on exactly why the San Francisco grounded. The area of operations was fairly familiar, well mapped, and often patrolled by similar submarines. Someone made a mistake, and several other someones failed to notice that mistake. Putting your submarine on the bottom is very hard on your equipment, but even harder on your career as a naval commander.
The big question for the civilian sector is not what caused this particular mistake, but whether such mistakes are as rare as we all wish they were, or if peacetime operations, and cost cutting operational norms have taken the edge off the finest submarine fleet in the world. You don’t have to hit the bottom to be doing things wrong, it just makes it a lot more obvious.
Tris
“For to win one hundred victories in one hundred battles is not the acme of skill. To subdue the enemy without fighting is the acme of skill.” ~ Sun-tzu ~
Regardless of the inquiry official results, several officers careers are now effectively over. Grounding your ship is a career killer.
While this is largely true, it is fortunately not always the case. For example, Admiral Chester Nimitz ran a boat aground as a young lad:
While rare, there are several examples of high ranking, prominent officers with “career ending” mistakes on their records. Good call with giving Nimitz a second chance, I’d say.