The Officer of the Deck, silently twisting around the periscope, begins to sense more than see the surface of the water above him as his billion dollar submarine glides up from the depths. The OOD hears only faintly the ships diving officer as he calls out each increment of depth change. The submarine begins to level. Straining for a glimpse of the horizon, the 000 suddenly hesitates — ever so slightly — in his circular walk. Although each member of the ship control party continues to carry out his particular task, there isn’t anyone in the room who did not notice the pause. Time stops.
“Emergency Deep, Emergency Deep!”
Control erupts. The first reaction is the snap of the scope handles as they are slammed to the vertical. The hydraulic control ring snaps loudly as the OOD hurries to lower the scope. All else is curtailed by the quick flow of orders and actions. The. helm rings up All Ahead Full and orders maneuvering to cavitate. The Diving Officer orders “full dive• on the fairwater planes, followed closely by “full dive” on the stern planes. The Chief of the Watch relays the OODs “Emergency Deep” orders over the ships general announcing system and immediately begins to flood the depth control tank. Sonar gains contact on a close aboard surface contact and reports that “sierra six shows no bearing drift.” The once barely perceptible beat of a distant merchant ship’s screws grows to a thundering sound — only to be drowned out by the sound of the submarine’s own propeller as it digs to move nearly seven thousand tons and one hundred people out of the path of the lumbering deep draft merchant vessel. As the submarine begins to pitch over and accelerate towards the relative safety of the deep, the sleeping are awakened and forced against the end of their bunks. Within seconds the captain arrives in control. Eyes not night adapted, he sees things only dimly. Although meeting with a cacophony of noise, he is able to recognize from sonar reports that the merchant ship, originally abeam to port with no noticeable bearing drift, is beginning to draw rapidly left. He immediately orders the rudder to left full and braces for a possible collision.
Of the many routine evolutions conducted by submarines, few are as hazardous as taking the ship to periscope depth. Submarines become extremely wlnerable when operating near the surface. The most crucial period of these near-surface operations is the transition from deep to shallow. During this time the submarine’s acoustic sensors, her ears during normal submerged steaming, are degraded. The physics of underwater sound and the near surface effect of solar heating and other factors combine to render sonar nearly useless.
It is during the ascent to periscope depth that the acquired skills and experience of the OOD stand as the first line of defense against collision and disaster. The OOD must carefully plan and execute this routine evolution. The submarine’s control party, sonar, and other operators, must act as a team to expertly guide the submarine through the usual acoustic layer. In the final analysis, however, it is one eye, pressed up against the scope, which warns of close aboard and potentially damaging surface contacts.
A commonly stated rule of thumb for the OOD has been “One in low, time to go. Four in high, time to fly.” That is to say, an average surface contact which subtends one division in low power or four divisions in high power through the scope should, under normal circumstances, be considered as an immediate threat to a submarine’s safety with emergency deep procedures, as described above, initiated. Simple mental analysis shows that this thumbrule acts to avoid surface ships within roughly four thousand yards. While certainly prudent, it may be too conservative.
Consider a recent fleet exercise involving the Constellation Carrier Battle Group and the USS LA JOLLA (SSN 701). During this eleven-day exercise, LA JOLLA was tasked with the role of orange SSN to work up the ASW defenses of the battle group. It was soon found that due to poor acoustic conditions in the operating areas, submarine operations well inside four thousand yards were frequently required to provide adequate training opportunities for elements of the battle group. Obviously this was a problem.In order to gain a more quantitative feel for the “emergency deep” scenario, a method was devised to test the submarine’s ability to move out of the way of a close aboard contact. With the area free of any surface traffic and own submarine at periscope depth, numerous emergency deeps were conducted under a varying set of initial conditions and control party actions. The intent was to find out how long it took the submarine to get below 120 feet and to measure the advance and transfer during the evolution. The results are shown in Figure (1) and summarized in Figure (2).
As the reader might imagine, these results were found to be very interesting. Under no set of reasonable initial conditions and operator actions did it take longer than 45 seconds for· the submarine to get below 120′. More surprising, in no case was advance of this 120 yard submarine greater than 250 yards. Taken to the extreme, it would appear that the doctrinal actions required for the “emergency deep” scenario would be effective for a deep draft merchant ship closing at thirty knots and at a range of 1000 yards.
While having little interest in proving the above results in practice, it is clear that armed with the results of the evolution conducted, the submarine’s CO will not feel quite as anxious as he may when operating in the inner zone of a battle group. This evolution had many other beneficial effects. It allowed all members of the submarine’s control party the opportunity to develop their skills in this demanding process. It provided invaluable training for the Junior Officers. It reaffirmed the value of proving a theory by means of a practice evolution. It proved that theory to operational reality is not just something our nuclear trained friends talk about. Without a doubt the results of this evolution allowed for a dramatic increase in the training provided the ASW elements of the Carrier Battle Group. Finally, and perhaps most importantly, it showed just how capable these magnificent LOS ANGELES class submarines are in getting our butts out of the fire in the most demanding of circumstances.
P. Kevin Peppe