Real Submarine Technology & History Q&A

[Buddahaid]

I want to get your thoughts about what I understand regarding the danger of high angle, high speed emergency blows. The risk involves after breaking surface, the possibility of sliding backwards instead of the bow dipping and the boat leveling off. If it were to slide back, the ballast tanks would take on a lot of sea, causing a heavy boat with a large angle. Thus leading to an uncontrolled dive and disaster. I think this was tested and the maneuver banned as to risky.

Buddahaid

[DaveyJ576]

Originally Posted by Mikeb213

Back then on Darter, I can't remember for sure but weren't the 688s using the BSY-1 suite at the time? Did they have anything like that retro fitted on to the diesel boats? Did they place a towed sonar array on board also?

The highly advanced and capable AN/BSY-1 integrated combat system premiered with the USS San Juan (SSN-751) in 1988. Earlier units of the Los Angeles class were equipped with the still potent BQQ-5 and 5E systems. None of these systems were retrofitted into diesel submarines. There were several reasons behind this.

1. The remaining combat capable diesel boats, Darter, Barbel, Blueback, and Bonefish were just not large enough to handle the new displays in their sonar rooms.

2. These new systems all used a large, spherical, bow mounted sonar array. All four boats had bow mounted torpedo tubes that made them incompatible with this array.

3. These systems used an enormous amount of power. None of the diesel boats could produce enough sustainable electricity to power the systems.

4. By 1988 the diesel boats were 30 years old and while still very useful, were not worth such a massive upgrade, even if it were feasible. Darter and Barbel were decommissioned in 1989, Blueback in '90, and Bonefish in '88.

Towed array systems, while very useful, were again not very compatible with the older submarines. The Submarine Towed Array Sonar System (STASS) was installed for a brief time on at least Darter and Barbel. It gave us some good data, but it was a pain in the butt operationally. It was a "clip-on" system that sat exposed on the after deck. It was coiled by hand around several stanchions and had to be deployed and retrieved by hand (what we called the "Armstrong Engineering Method" ) while on the surface. If the sea was too rough to send someone topside to retrieve it, we couldn't go into port. That delayed a liberty run to Hong Kong once and the crew was pretty pissed. We eventually beached the system and the Darter finished her service without it.

[DaveyJ576]

Originally Posted by Buddahaid

I want to get your thoughts about what I understand regarding the danger of high angle, high speed emergency blows. The risk involves after breaking surface, the possibility of sliding backwards instead of the bow dipping and the boat leveling off. If it were to slide back, the ballast tanks would take on a lot of sea, causing a heavy boat with a large angle. Thus leading to an uncontrolled dive and disaster. I think this was tested and the maneuver banned as to risky.

I am not sure were you are getting your information, but unfortunately none of it is correct.

Emergency blow systems were retrofitted to all USN submarines following the Thresher disaster in 1963. These systems are designed to rapidly surface a submarine in the event of flooding or other trouble. 3000 psi air is rapidly fed into the main ballast tanks, almost instantly emptying them (even down to test depth). This sends the boat up like a rocket with a large up angle.

A submarine is rarely, if ever, at a dead stop while submerged. It will always have at least some forward momentum. This momentum will cause it to continue to move forward after it breaks the surface, thus negating any possibility of sliding backwards. Even if it were at a dead stop, the act of conducting an emergency blow will give it some forward momentum.

Obviously, in order to conduct an emergency blow the main ballast tank vents have to be shut. This will trap the air inside of the tanks and prevent it from escaping. True, if the boat were at a 90 degree angle (i.e. vertical) and slid backwards into the sea it would lose a lot of the trapped air. But this never happens. As long as the crew has at least some control of the boat, they will control the angle using the stern planes and keep it to less than a 45 degree angle (usually only about a 30 degree angle at most). Combined with the aforementioned forward momentum this will keep enough air in the tanks to keep the boat on the surface.

See these links for what I am talking about:

http://www.navsource.org/archives/08/0876205.jpg

http://www.navsource.org/archives/08/0871912.jpg

Notice that in both photos the angle is fairly shallow, probably not more than 25 degrees. Also notice that the boat is really moving forward and will not slide backwards.

I will grant you that the situation that you described is theoretically possible, but it is extraordinarily unlikely to happen. Procedures and crew action alone preclude it from happening.

Emergency blows are a routine part of training for all USN submarine crews and are done on a regular basis. I personally participated in about 12 of them in the three years I was on the Darter. It is true that the maneuver is dangerous, mostly from collision at or near the surface. But with proper controls, those risks can be mitigated.

[Buddahaid]

OK. I got the story from Dad who worked at Mare Island and was on sea trials, and is in reference to the Gato, or similar types, rising at a very high angle and speed, allowing the open undersides of the ballast tanks to spill air. It may not involve an emergency blow, and unfortunately I don't have any details, but I understood it was testing how high an angle could be safely used. Thanks for the response.

Buddahaid

[DaveyJ576]

Originally Posted by Buddahaid

OK. I got the story from Dad who worked at Mare Island and was on sea trials, and is in reference to the Gato, or similar types, rising at a very high angle and speed, allowing the open undersides of the ballast tanks to spill air. It may not involve an emergency blow, and unfortunately I don't have any details, but I understood it was testing how high an angle could be safely used. Thanks for the response.

Buddahaid

Back in the 50's and 60's there was all sorts of testing going on to determine the maximum operating parameters of our boats. I don't doubt for a minute that the tests your dad described took place. However, keep in mind that these were tests and the boat was deliberately put in an out of control condition (this is extremely dangerous by the way). Anything approaching "normal" conditions would have the boat under control by the crew and the angle of the surfacing strictly regulated.

Check out the following photo of the USS Pickerel (SS-524) During an surfacing drill on 01 March 1952.

http://www.navsource.org/archives/08/0852403.jpg

This is not a true Emergency Surface as she did not have the system at the time. However, she started at 250 feet and flank speed. The planesmen were ordered to take a 60 degree up bubble. They lost control at 65 degrees and the boat hit 72 degrees (Holy Crap!!) just prior to breaking the surface. This is the unofficial record for an up angle on surfacing.

The only thing I would question about your account of the tests is about losing air out of the ballast tanks. With the vents shut, the air is going to be trapped inside the tanks. It will not spill out the bottom. Any remaining residual water will, but the air won't. The only time that would happen is if the boat was at a 90 degree angle or greater. Anything less than that and the air would remain trapped inside the tanks as the boat settled back into the water.

Take a look at the following video of a 688 doing an Emergency Blow:



Notice the angle of the boat and how far it settles back into the water afterward. Even still, it promptly pops back up to the surface.

[Buddahaid]

Yup that USS Pickerel shot is what I'm referring to.

Thanks again.
Buddahaid

[Mikeb213]

Hey Davey,
So can you really take a piece of string and tape it to either side of the hull in a sub, and as it goes down deep does the hull compress that much that it would make the string droop?

[Deamon]

Originally Posted by DaveyJ576

3000 psi air is rapidly fed into the main ballast tanks, almost instantly emptying them (even down to test depth).

I am wondering what almost instantly means here, do the ballast tanks get emptied faster than they get filled during crash dive ?

[Mikeb213]

Davey another question too, I just saw that the Dolphin was made into a museum, and that it can dive so deep that the dive info is still restricted. The only info they gave was that it was over 3000 feet. If you did an emergency blow that deep, is there a speed the sub reaches that it tops out at? I know when I used to play the game 688i if I was running deep and trying to evade a torpedo at the last few seconds before I got taken out I would try and do an Eblow and I would get a burst of speed that would put me over 45knots. Can't you damage the ship coming out of the water that fast on the slam down?

[DaveyJ576]

Originally Posted by Mikeb213

Hey Davey,
So can you really take a piece of string and tape it to either side of the hull in a sub, and as it goes down deep does the hull compress that much that it would make the string droop?

I can verify that it will actually do that. You can't visibly see the hull compress, but it surely does.

The doors going into the heads are non-watertight aluminum doors that sit inside of a frame, very similar to what you would find in any house. On the surface, the doors open and shut freely with a minimal amount of force. Once you go deep, the hull compresses enough to warp the door frame out of square and compress it against the door. You could open the door with one finger on the surface, but now it requires a pretty good tug with both hands.

You also have to be very careful when flushing the toilets. They are flushed with seawater and on the surface you get a nice flow into the bowl with just enough pressure to flush the contents. Down deep, you just barely crack the valve and you get a Niagara Falls flow that if you are not damn careful could flood the whole head!

[DaveyJ576]

Originally Posted by Deamon

I am wondering what almost instantly means here, do the ballast tanks get emptied faster than they get filled during crash dive ?

Perhaps it was a poor choice of words. I should have used "very rapidly" as opposed to "almost instantly".

On the Darter, an emergency blow would empty the tanks in about 2-3 seconds from 200 feet. I never did one from test depth, but it would take a little longer due to the much higher sea pressure. I would estimate probably 10-12 seconds. A normal surfacing blow of 1500 psi would empty the tanks in about 5 seconds from periscope depth (48 feet).

[DaveyJ576]

Originally Posted by Mikeb213

Davey another question too, I just saw that the Dolphin was made into a museum, and that it can dive so deep that the dive info is still restricted. The only info they gave was that it was over 3000 feet. If you did an emergency blow that deep, is there a speed the sub reaches that it tops out at? I know when I used to play the game 688i if I was running deep and trying to evade a torpedo at the last few seconds before I got taken out I would try and do an Eblow and I would get a burst of speed that would put me over 45knots. Can't you damage the ship coming out of the water that fast on the slam down?

Damaging a sub with excessive speed is definitely possible. A submarine is like an airplane in that respect. Go too fast and the aerodynamic (or hydrodynamic) forces will eventually exceed the ability of the structure to resist it and it will break apart. What that point is for a submarine I have no idea and I do not want to find out. The marine engineer who designed it would have to provide the answer.

As a point of reference, the Space Shuttle Challenger was not destroyed in an explosion. True, the External Tank exploded due to flame impingement from a O-ring leak-by from one of the Solid Rocket Boosters. But the Challenger herself was destroyed when the explosion forced it out of its normal flightpath. The aerodynamic loads exceeded their limits and she instantly broke up. What most people don't realize is that during the first two minutes of ascent, the space shuttle is operating at the very limits of structural strength. Only the slightest deviation from its programmed flightpath is necessary to cause it to break up.

[Mikeb213]

Davey, how would they control the speed of ascent on a eblow from very deep?

[DaveyJ576]

Originally Posted by Mikeb213

Davey, how would they control the speed of ascent on a eblow from very deep?

You will gain some speed on the way up, but not a lot. Even from test depth you might pick up only 5 knots or so. But if you had to reign in the speed you would simply back down on the propeller (properly called a screw).

[Mikeb213]

Dave,
What do they do to prepair a ship for becoming a museum? I have seen at least one that looked like it was ready to sail, and had working engiens. The Pampinito in San Francisco is a very good example. Can they still sail under there own power? Is it possible to still dive one of the subs? How about the aircraft carriers? Do they remove the engiens so it can't move? Could they be put back into service?