Security Studies Program Seminar

Submarine Operations and ASW: A View from Both Sides of the Periscope

Commander Van Gurley
U.S. Navy
Military Fellow, SSP

April 7, 2004

The SSN fleet (nuclear powered attack subs) consists of 54 subs, with 19 more planned and 10 forward deployed. The SSBN fleet (nuclear armed submarines, or boomers) consists of 16 submarines with 10 more planned.

Although subs comprise 25% of naval ships, they only use 12-13% the Navy's manpower, meaning that they are cheap once built.

What roles do subs play today in the US military?

  1. Anti submarine warfare (ASW). This role is less pressing since the end of the Cold War, driving the decline in the amount of submarines.
  2. Intelligence, surveillance and reconnaissance (ISR). Stealth capability equips subs for this role. As does endurance — the ability to stay at sea as long as the crew can eat. The problems are maintaining communication and subs' limited ability to stand and fight. Subs are not well-suited to exchange blows. The idea is shoot first and kill; shoot and go.

The Los Angeles class is the mainstay of the fleet. The United States built 62 in the 1970s, now 51 are in service. They are manned by 127 crewmembers. They house 12 VLS missile tubes. Some say these subs cost a lot of money for not a lot of bang. The depth is 800 feet plus, the speed 20 knots plus. They have no fuel or weather problems.

The Sea Wolf was the follow-on class designed to fight Soviet subs. These have 8 torpedo tubes instead of four. They can travel with speed and quiet speed. Unfortunately they are very expensive, and only three were made.

The next class is the Virginia class, the new SSN program. One is complete, three others are underway. These subs are 360 feet long. They have more ISR capability than previous subs. The subs will be able to launch and take back unmanned craft. The subs give special operations forces a capability to get to shore.

The submariner's goal is to keep 54 SSN in the fleet. The Navy's goal is lower. One study called for 68, but that is not likely to happen.

The SSBN fleet consists of 18 Ohio-class subs built between 1981 and 1997. The crew for each includes 169 people. Each sub has 4 torpedo tubes. There are always six SSBNs at sea, although they are not always on alert. Four of the submarines are losing their nuclear weapons due to U.S. treaty obligations. The Navy came up with a plan to replace the nuclear weapons on these submarines with 154 tomahawk missiles, space for Navy Seal landing craft and mini-subs with launch capability.

In front the Ohio-class subs have sonar. Behind that is ballast tank which, by opening, causes the sub to submerge. Air is pumped in at the surface. The VLS tubes are behind the ballast tank. Behind that is the living space. Canned food is stored everywhere in this area. Behind the living space is the reactor. Behind the reactor is engineering space, and behind that are more ballast tanks.

Nuclear powered submarines are refueled only every 15 years. The reactor on the sub is controlled by four crewmembers. Diesel electric subs are different; they are more dependent on batteries.

The control and attack center is the key room. The periscopes are there. Every sub has two antennas, for radar and early warning. They have cameras with video and night vision. This room is where the controls are that keep the sub balanced and at depth.

There are two kinds of sonar, active and passive. Active sonar is older. You send out a signal and wait for a ping. That gives you instantaneous bearing and range. The problem is that it's fairly short range, and more importantly, it gives away your position. With active sonar you can hear out to ten miles, but you can be heard out to 20 miles.

Passive sonar is what the Navy generally uses today. Passive simply means listening to what your instruments can hear. Passive gives you bearing but not range, and it takes a long time to convert this to useable information. The temperature structure of the ocean dictates how sound moves through it. It puts bend on the sound. Submariners map out the temperature and velocity structure of the water to figure out where to hide.

The most dangerous thing subs do is go to periscope depth. It's easy to miss something directly above you. One reason to come up is to get a GPS fix. Another is to stick up the snorkel mast to get air in. But subs can generate oxygen; they can go months without ventilation if need be.

The Mark 48 torpedo is the mainstay torpedo. It carries a 640 pound warhead, which is small, with a fuse set to detonate on impact. Surface ships have torpedoes half this size. The Mark 48 is wire-guided, so you can see what the torpedo sees, and can steer if need be.

Anti submarine warfare (ASW) consists of the detection to engagement chain. From a submariner's standpoint the goal is to avoid speed and the need to use it, keep stealth, and maintain tactical control. Positioning is everything; the aim is pick your spot and get there, to maneuver into the right position to lay in wait. Then you shoot and move, probably hoping to reengage later from a different bearing.

Detection is difficult. It's hard to classify sounds. Localization is also difficult. Tracking is easy if you have steady contact, but with a lot of turning, this is difficult too. Engagement depends on knowing where the other guy is.

Because subs have to surface to communicate, they don't work well with others. The ability to communicate while deep is the naval Holy Grail.

From the perspective of the surface ship, detection is very difficult, so you set up a layered system. You husband resources. You want to avoid getting into an attrition battle. You use speed, maneuver, and deception (WWII tactics). Deception makes him commit, then you can get him. One way to do this is convoy operations, which make the sub commit. Another is a maritime shield — this requires more technology.

Rapporteur: Ben Friedman

back to seminar schedule, Spring 2004