I would hope that based on this experience all US nuclear subs now have at least some emergency battery power for propulsion.
They did back then as well. They had Electrical issues and I’m assuming they couldn’t run their “EPM” .
We’ve changed quite a few things as a result though. SOP back then was to close the main steam stop valves during a Reactor scram. We leave them open now to be able to use the main engine if we need to. Not sure how long it would last, though! We also do “fast recovery start ups” on the reactor now which bring the reactor/steam plant back online quicker.
Oh and we have “Reactor fast insertions” now that are a controlled partial insertion of the control rods. They are faster to recover from than a full scram which lets the rods just drop to the bottom.
http://www.jag.navy.mil/library/investigations/USS%20THRESHER%20PT%202.pdf
Interesting link to some finding regarding the Thresher sinking.
As I understand it, and I’m not an expert, a modern diesel electric sub is quieter and thus more difficult to detect than a nuke. Especially when in restricted shallower waters, where they could perhaps lie on the bottom, and the current flow over the seabed tends to be noisier and to shield the sub noises.
Recall that a few years back a North Korean minisub apparently snuck up on and sunk a South Korean ship. And this was a warship in the midst of antisubmarine exercises.
I don’t know how good Iranian subs are, but I would guess that North Korean minisubs aren’t exactly cutting edge technology themselves.
Well, of course the flooding was uncontrolled, or the submarine would not have sunk. If the flooding had been controllable, the crew could have isolated or repaired the leak. (That being said, I suppose it is possible to argue that the flooding was in fact “controllable,” but that the leak was not able to be isolated or repaired until too much water had been taken on board to maintain depth control. However, it is my understanding that the flooding was never actually controlled and that the ship was actively taking on water until it imploded at crush depth.)
Cite from here:
As a fellow member of Uncle Sam’s Submarine Club, you should well know that no flooding in the engine room is “minor.” 
ETA: From the declassified report that you posted, the investigators’ opinion was that the flooding was in all probability from “an orifice between 2” and 5" in size in the engine room." At the depth that Thresher was operating, such flooding would in no sense be considered to be “minor.” Later on, though, they also state that the flooding casualty could have been due to various other causes, including a “minor hull fracture” (which I have not heard elsewhere).
BTW, note that all actual depths were redacted from the report.
This is all true, which were all complicating factors that ended up made it impossible for the ship to recover from the flooding casualty. No propulsion, plus no ability to blow the ballast tanks, plus the inability to control the flooding resulted in loss of the submarine.
Incidentally, a contributing factor for the flooding casualty in the first place was the hundreds of hull penetrations that was common in submarine designs up to that point. The loss of the *Thresher * was one of the precipitating factors that led to the implementation of the SUBSAFE program, which included a more robust emergency blow system, and fewer hull penetrations with quick-acting isolation valves, along with improved quality assurance procedures.
This is a true statement for the Thresher, but measures were taken in subsequent designs to prevent this from happening, including much shorter, larger diameter, less “tortuous” piping for the emergency blow system, as well as dehumidification of the compressed high pressure air in the air banks.
Yeah man, I had a gage line let loose at 150’ and it sounded like a freight train! Water in the people tank = BAD. BUT from what I read the flooding would have been “recoverable” IF they had been able to blow to surface OR had not lost propulsion.
“ETA: From the declassified report that you posted, the investigators’ opinion was that the flooding was in all probability from “an orifice between 2” and 5” in size in the engine room." At the depth that Thresher was operating, such flooding would in no sense be considered to be “minor.” Later on, though, they also state that the flooding casualty could have been due to various other causes, including a “minor hull fracture” (which I have not heard elsewhere)"
“Minor hull fracture” ? :eek: