Walter:

"THE SILENT WAR: THE COLD WAR BATLE BENEATH THE SEA" by John Pina Craven - cc2001.


The following is an excerpt of this book:

"When NAUTILUS' CO, CDR. Eugene P. Wilkinson and retired ADM. Andrew McKee, Chief designer for Electric Boat and I had completed our inspection of the hull we were in a state of shock. What we saw were ring stiffeners that had been torn away from the hull as though a giant hand had repeatedly twisted them until they failed with fatigue. We could put our hands between the hull and the stiffeners. McKee was in shock because that discovery implied that he had completely underestimated the forces between hull an stiffener. Wilkinson was in shock because he now realized that he had come closer to losing the NAUTILUS than he had ever thought, and I was in shock because I had studied the theory of enelastic buckling under the renowned Professor George Hausner at Cal Tech and I knew that McKee and Wilkinson were dead right. I had never before seen or imagined a structure so completely destroyed by stress and fatigue. It was well known that aircraft could fail from aeroelastic vibrations known as flutter, but it was assumed that the massive hull structures of submarines would not be affected by hydrodynamic forces produced by the sea as the submarine plows through the water. Something was happening to separate the ring stiffeners from the hull and as a result the collapse depth ---the level beneath the surface of the sea at which even the most powerful sub-marine hull will implode without warning as a result of the pressure of the water
around it --- was greatly reduced.

Our inspection disclosed, to our horror, that all the ballast tanks showed splits along their sides. If the ballast tanks leak, then water will flood the tanks
unless replacement air is continuously added. Otherwise the submarine sinks. For the NAUTILUS, already down by the bow, the splits in the tanks limited the size o the bubble that could be contained and caused a continuous drain of the air stored in the ballast tank air bottles. It was only a matter of hours before the onboard supply of air would be exhausted. The bottles that contained the precious air had broken loose from their attachments to the hull inside the ballast tanks and were dangling from the piping that carried the air from bottle to tank. In a few hours, or at most a few days, the air bottles would detach completely and then the frames would separate from the hull and the NAUTILUS and
her crew of 116 hands would be doomed. Thus three modes of failure were imminent: destruction of the pressure hull, loss of ability to hold ballast air, and the loss of air with which to blow ballast and provide the buoyancy to raise the submarine.

The next tests were conducted at shallow depth. All hands were relaxed when suddenly there was the sound of a violent explosion in one of the ballast tanks,
then in another---an intermittent series of powerful blasts in one or more of the
ballast tanks. The OOD quickly reduced speed and the blasts stopped. I must admit I was alarmed. The crew informed me that they had experienced them before
not knowing what they were. I had a sudden insight, recognizing this as a phenomenon know as "cavitation." Vapor (vacuum) was being generated by negative pressure in the ballast tanks that exceeded pressure of water at that depth. In
shallow water, or at atmospheric pressure, this negative pressure is about one atmosphere, or some fifteen psi. We were getting more than double that inside the tanks. I pointed out that the explosive sounds were produced by nothing more than great pockets of collapsing vapor. The vapor itself was pressure-relieving
and the collapse had merely reinitiated the pounding to which the ship was continuously exposed.

The mission done, a simple, straightforward, and still classified modification of the ballast tank openings in hand, the NAUTILUS headed back to port.

What was the fix? Install "bolt-on" grated, steel covers on all main ballast tank flood ports.

And have a pleasant day,

ROBERT M.