Western knowledge of nonnuclear-powered submarines—growing in capability and desirability among Third World nations—is limited. Some insight into diesel sub operations and tactics might help Western navies in potential future conflicts.
During the Gulf War, modem sensors showed a remarkable capability to detect and keep track of small mobile platforms. Published photos from the joint surveillance target attack radar system scopes, showing Iraqi vehicles fleeing Kuwait City, have been studied all over the world. The conclusion must be the same for any regional power: If you are facing even a major regional power, it is no longer possible to hide on the surface or in the air. The only hiding place left is below the surface.
Today, 21 so-called Third World countries operate a fleet of 110 submarines. The number has declined somewhat in the past five years because of the scrapping of older boats, but what the figures do not show is the increase in quality that has taken place at the same time. Many of the old conventional submarines have been replaced by modem, much more capable boats.
Our knowledge of modern nonnuclear-powered submarines is in many ways very limited. The two major Western navies don’t operate this type of boat any longer, and the number of conventional submarines operated by other Western navies is declining. To an old diesel boat commanding officer, it looks as if the Western navies could be facing a major problem in a future conflict.
Nonnuclear Subs & Littoral Warfare
The nonnuclear-powered submarine is much smaller than its nuclear counterpart, which gives it a smaller sonar target strength and magnetic signature, and its electrical propulsion means negligible radiated noise, except when the sub is snorkeling. But the size of the submarine also limits its capabilities. All electrical energy has to be created during snorkeling and stored in batteries, which limits the maximum speed and submerged time available. In addition, conventional boats normally cannot carry enough oxygen and carbon-dioxide cleaning to last for an entire patrol and must rely on snorkelings to freshen the internal atmosphere.
Compared to the nuclear submarine, the modem conventional submarine is manned with very few men. The crew limit is driven by the smaller size of the boat and the need to reduce the consumption of water, food, and oxygen—thereby increasing endurance and the time between snorkelings. Fewer men, however, also means a reduction in on-board repair capability, which ultimately reduces the endurance of the submarine.
Littoral warfare, by definition, will occur in the shallow water close to a coastline. The limited water depth will influence the use of not only sonars and sonar buoys but also other sensors such as those for magnetic anomaly detection. The weapons available to the antisubmarine warfare (ASW) force will be restricted by the depth, and their consumption will increase along with the number of false contacts caused by higher ambient sea noise, ray-path bendings and reflections, and bottom debris. In addition, in the shallow-water zone close to shore, fresh water from estuaries mixes with the ocean water, creating unpredictable layers with gradients not seen in the oceans.
While hunting for the nonnuclear-powered submarine, the ASW force also will face the threat of shore-based surface-to-air missiles, surface-to-surface missiles, mines, and fixed bottom installations.
In a conflict between a major and a minor sea power, the smaller country will have to adopt the mission of sea denial, with submarines operating off local key points or vital coastal areas. A daring naval command can chose to send the submarines father from the coast to catch some of the enemy’s vital shipping, such as carriers or supply and landing ships, but the endurance of the conventional submarine still is measured in weeks.
The nonnuclear submarine will prefer to operate alone. Its limited on-board electrical energy can be exhausted rapidly in high-speed dashes, while trying to keep station on surface ships. Even cooperation with other submarines is energy consuming, noisy, and dependent on communication. The only support will come from the radio broadcasts, supporting mine fields, and missile coverage from the shore, but the submarine will try to get the maximum benefit from these assets, especially while snorkeling.
A submarine operating in its own littoral waters has the home-field advantage. It knows where layers can be expected; it knows the ambient sea noise in the area; and it has a firm knowledge of the shallow patches, where trailing submarines have to give up the hunt.
While on patrol, the commanding officer of a conventional submarine always must be thinking of the battery and the amount of energy remaining. In the patrol area, speed seldom will exceed five knots, to limit energy consumption and radiated noise. Reluctant to operate with low battery, a submarine’s CO will take any opportunity to snorkel. It is better to do many, short snorkelings than a few longer ones. Following this policy, the submarine will never be caught low in stored energy, lacking the ability either to evade or to attack.
A small naval power probably will not be able to provide submarines with the same intelligence flow as a major naval power. The submarine will have to rely on its own sensors with a rather limited range. The hydroacoustic range and analysis capacity will be limited, so the submarine will support the acoustic picture when feasible with electronic surveillance and periscope observations. Compared to the nuclear submarine, then, the nonnuclear-powered boat will have to spend more time at periscope depth.
During an attack the submarine will try to remain undetected for as long as possible. The submarine commander will attempt to sneak within firing range without using undue speed or other maneuvering that might give away his position. When in doubt about being detected, the commander will try to avoid giving his opponent a clear classification. He will start his evasion only when he is certain that the enemy is in contact. Then he will execute a rapid series of speed, depth, and course changes, together with a launch of decoys. The submarine will try to clear the datum as quickly as possible, before the ASW force can get organized.
By that time the nearest escorts are set in the fire-control computer and the submarine’s torpedoes soon will be away. Even a bad firing solution will keep the escorts busy while the submarine evades. If no firing solution exists, the torpedo will be launched in a circular pattern close to the submarine datum. If the main body of ships don’t take evasive action away from the datum, the submarine then will do its best to get in a long shot against the target.
The submarine commander is an aggressive, mission-oriented person, who first will try to hit his main target. Only after being bypassed by the main body will he turn his full attention to the escorts. He knows the value of a modern escort and will prefer to bring it home instead of nothing. Suddenly, one or two escorts can become targets for the submarine.
After a successful attack the submarine will clear the datum. Even a burning datum gives an idea of the position of the submarine. One of the best ways for the submarine to get away is to go for swept water, where the ASW force will have a tendency not to look.
Countering the Threat
It is likely that the threat will be limited to a handful of conventional submarines. Because of the limited number of submarines and the lack of qualified exercise opposition, potential adversary naval commands probably will have limited experience with submarine control.
The submarines also will have suffered from a shortage of good training opportunities and limited training facilities ashore. A small number of submarines makes it very expensive to maintain a full set of spare parts and repair facilities. Sensor-accuracy check sites and noise ranges are expensive to operate and probably will have a limited capacity. For these reasons. Third World conventional submarines might be deployed at less than their full capabilities.
If you are going to fight nonnuclear-powered submarines, however, do not make it easy for them. A multiple threat is the worst one for this kind of submarine, because of its limited support from ashore and limited sensor and command capacity on board. Declarations of mine fields off the enemy coast also will hamper their submarine operations.
Try at all times to confuse your opponent with random patrolling, with sensor transmissions periodically reduced, in sector scan mode, or even switched off. Never forget to press your opponent. It is much more productive for a maritime patrol aircraft force to cover a large area with a low- detection probability than to search sporadically in some small area with a much higher detection probability. In the latter case, the submarine will go to ultra-quiet state or sit on the bottom and wait until your search is finished before returning to periscope depth to recharge its batteries. But if the aircraft periodically cover the entire area, the submarine will be forced to snorkel frequently for short periods to keep the battery at an acceptable level. For a boat with a small crew, this is extremely tiring and frustrating.
Prosecute all possible or probable contacts. If you had no luck the first time, return later to the area and make a new search. If there is a submarine in the area, it will have to return to periscope depth and snorkel sooner or later. This will be the time to surprise him.
Finally, the hunt for the conventional submarine is not an easy game. You will have to practice a lot before you master the art, so use any training opportunity you get.
Nonnuclear-powered submarines have become more capable—all kinds of signatures have been reduced and sensors and weapons have been improved—and this evolution will continue. The old Mk 8/Mod 4 torpedo, used by HMS Conqueror to sink the Argentine cruiser General Belgrano during the Falklands Conflict, is history. Firings with homing torpedoes in excess of five nautical miles are common today, and the range will more than double in the future.
The revolution of the nonnuclear-powered submarine may be just around the comer. The best propulsion solution may be yet to be found, but it is certain that the next generation of nonnuclear-powered submarines will be able to stay submerged longer, thereby limiting the probability of detection.
Commander Madsen is Commander, 5th Squadron (De), which consists of the Danish submarines and SEAL teams. He has commanded six submarines, a mine layer, and two fishery inspection ships. He attended the U.S. Naval Staff College in 1979.