Around the World Submerged: The Voyage of the Triton

Rowlands agreed. “But we’ll have to go pretty deep, Captain, to quiet down them spinning wheels with all that power.”

He was right. The deeper you go, the less noise your propellers make, but the bigger they are and the faster they spin, the more noise they make. Triton’s propellers, eleven feet in diameter, turning far faster than any other submarine’s, could not avoid making noise at their present shallow depth. But, of course, no other submarine could go as fast on the surface as Triton; when we slowed down to comparable speeds or when we submerged, the chances were that our ship would be as quiet as the others—perhaps quieter.

It was nearly time to dive. I hurried forward. Lieutenant Tom Thamm, Triton’s Diving Officer, was already at his station with his number one diving crew. This entire group had trained together for several months at the submarine dive simulator at Electric Boat and at another, fancier, one in the Submarine Base; but, of course, this was the first opportunity for them actually to dive the ship.

They were, naturally, somewhat keyed up. The weights in a submarine must be so balanced that when she fills her main ballast tanks the ship will be in precisely neutral buoyancy. Otherwise, she would not be controllable. Naturally, as stores or torpedoes are put aboard, consumed, fired, or unloaded, there are changes in internal weights. These are compensated for by the bow and stern trimming tanks, and by two auxiliary tanks located amidships. These four tanks are known as “variable tanks,” because the amount of water they contain may be varied. This can be done without danger of rupture due to internal or external pressure. The “ballast tanks,” by contrast, are always open at the bottom, are empty for buoyancy when the ship is surfaced, and must be fully flooded to dive her. One of the trickiest problems in designing a submarine is to calculate the weights and the volumes so that, with all conceivable weights out of the ship, it is still possible to put enough water into the variable tanks to achieve neutral buoyancy. Conversely, she must be designed so that with maximum weight on board, enough water can be pumped out to restore her to neutral buoyancy. (Ballast tanks cannot be used for this, despite the misleading name, for they must always be fully flooded when submerged. Since they are never under any pressure differential, they are lightly constructed, unlike the extremely rugged variable tanks.)

As Diving Officer, Tom’s job was to work out the compensation under the load condition that existed at any given time, and to calculate exactly how much water was required in each variable tank to insure that when Triton’s main ballast tanks were flooded, the ship would be both in neutral buoyancy and balanced fore and aft. When the right amounts of water are thus in her variable tanks, the ship, in submarine parlance, is in “diving trim” or “compensated.”

“The ship is rigged for dive and compensated, Captain,” Tom reported.

A submarine cannot submerge until it is “rigged for dive,” by which is meant that all the proper equipment for diving is in correct position, either open or shut, in power or set for hand operation as designated, and that every compartment has been inspected, both by the crew members responsible for rigging it and by an officer detailed to check it. There have been cases when a submarine was lost, seriously damaged, or suffered loss of life because of an improper rig somewhere.

“How is your trim?” I asked.

“I’ve pumped it all in,” Thamm said. He added, “I guess we’ll find out how good the trim is as soon as we pull the plug.”

The indicator lights on the Ballast Control Panel showed that we were ready to dive, except that our main air inlet pipe and the bridge hatch were still open.

“Shut the induction, Tom,” I said.

At Thamm’s signaled order, Fitzjarrald, hovering over the Ballast Control Panel, moved the control toggle switch to the shut position.

I picked up the microphone controlling the speaker on the bridge, told Brodie to reduce speed and shift his watch to the conning tower. There was a “clink” of annunciators, a clatter of feet on ladder rungs, a thump as the bridge hatch slammed shut. The Ballast Control Panel indicated that the last important hull opening was now closed.

“All clear topside!” Brodie’s voice came from the conning tower, where, according to plan, he would be manning the periscope.

“Bleed air, Tom,” I said.

Thamm picked up a microphone in his turn. “Engine room, this is control. Bleed high-pressure air into the ship!”