Tac Talks: The importance of stealth in combatting a submarine threat
The reports of my death are greatly exaggerated.
- Mark Twain
Introduction
There have been many articles raised on the obsolescence of submarines within the future maritime battlespace. With the advent of unmanned underwater vehicles and increasingly sophisticated sensors, the difficult art of submarining will become increasingly challenging in several crucial respects. The idea that submarines could no longer safely remain submerged is a great aim point but we are not there yet, and we will not be there for some time yet.
The sheer mathematics of generating a search area from a known datum, in an ever-changing acoustic medium, can quickly become staggering. Assuming you had an idea of where a submarine was to within about six nautical miles, the immediate search area would be roughly the size of central Canberra (airport to zoo east-west; Parliament House to Dickson north-south). This represents a relative bull’s-eye in regards to sub-hunting (when you take into account the vast amount of water a submarine has to hide in).
If you weren’t so sure of where the submarine was (say you were only confident to twelve nautical miles your initial search area will be closer to the size of a big chunk of Sydney (Bondi Beach to Penrith, Castle Hill to Liverpool).
The success of dipping sonar deployment will largely depend on the size of the search area.
Submarines, particularly the conventional diesel our nearest neighbours have, are not all that big, usually about the size of a Manly Ferry. Couple that small size with the search areas outlined above; the appalling search environment the underwater battlespace can provide and you have a big problem. Add the inbuilt stealth of submarine design with the ability of the submariner to use the environment to advantage, and you can get a pretty good approximation of the difficulties of Anti-Submarine Warfare (ASW).
To say submarines are obsolete is presumptuous at this stage and a dangerous thought process. The submarine has been on the verge of extinction since world war two - RADAR, ASDIC the hedgehog all cost the U-Boat Flotillas dearly but the use of submarines persisted well into the Cold War and into the modern era. Technology has forced a change in tactics from a surface raider to continuous dived operations, yet many of the original principles of submarine warfare remain extant. The improved mastery of the above water battlespace has made periscope and mast exposure increasingly risky - however, the advent of Air Independent technology has decreased the potential for counter detection by traditional means.
U-243 under attack from allied Sunderland Flying Boat.
Although there have been great gains in Low-Frequency Active Sonar (LFAS), bistatic/multistatic sonars, Unmanned Underwater Systems (UUS) and Non-Acoustic Detection capabilities, there is nothing currently available that makes the ocean transparent. Whilst there is exciting and encouraging development in ASW technology, the advantage still lies with the submarine. Being a submariner is difficult; finding a submarine that doesn’t want to be found is harder.
Silence is a source of great strength.
- Lao Tzu
“Why is it important to have quiet ships?” Believe it or not, this is a question that keeps cropping up in my inbox. As a submariner, we live and die by self-noise. Our platforms are designed to be quiet and we take steps to maintain their stealth daily. Self-monitoring of own ship and chasing down (and rectifying) noise shorts is a regular occurrence. Data gathered from noise-monitoring does get fed back into the design process during modernisation and upgrades. Whilst I am surprised by this question,
HMAS Farncomb sails for a media day from the Port of Albany, taking onboard one civilian journalist, a Navy photographer and three Navy Cadets from TS Vancouver. Photographer: ABPH Lincoln Commane.
I understand why it keeps popping up. In an economic environment of restricted defence spending and increased public scrutiny, any spending needs to have a “hand-on-heart” specific operational requirement. The bang for the buck equation comes into every system on every platform and be able to be justified to the general public. It may be tempting to shift funds away from noise quietening and may look great on paper, but to expect improved sensors to mitigate the risk is fraught with danger.
As we look to fit our ships with more sophisticated sonars and sensors (and hopefully increase detection ranges), why do we need to worry about being a quiet platform? USN doctrine lists five key adverse effects of ship-generated noise:
- Decreases in own ship’s sonar detection range,
- Interferes with own ship’s narrowband processing capabilities,
- Increase counter detection range,
- Increases probability of being acquired by an acoustic homing torpedo, and
- Increase chances of own ship detonating an acoustic influence mine.
Arguably, as sensors and associated processing become more sophisticated, some of these effects may be mitigated somewhat. If we focus on the first two points with an eye on one of the future directions of research, Unmanned Underwater Systems, the importance of reducing self-noise becomes clear.
To put it in a simplified context, passive tracking is basically “listening” via sonar to the sounds in the ocean for man-made sounds associated with a target ship or submarine. If we transfer this to the land environment it’s like hunting for a specific animal in the jungle. The jungle (like the ocean) is not always quiet. There is environmental noise (wind, rain, running water), other animals that aren’t our prey and whatever noise we bring with us. If we are sneaking through (and hope to successfully track our prey) the jungle we would ideally like to creep around stealthily; not clomp around with camp gear rattling on our backpack. The principles are similar.
Petty Officer Electronics Technician Submariner Sara Clarke onboard HMAS Sheean alongside during a logistics visit of Beauty Point, Tasmania. Photographer: LSIS Nadav Harel.
Narrowband processing relies on monitoring of some specific frequencies which help identify our target submarine or ship from the other man-made contacts held on sonar. This is the prime method of classifying quiet contacts and is a difficult art form. Self-noise can create false narrowband contacts which need investigating and slow up the targeting process. If we couple a swarm of roaming unmanned sensors surrounding our future warship, these false contacts take up time, bandwidth and may confuse the tactical picture. If we are going to seriously develop unmanned capability and solve the associated underwater communications issues, we as a military need to start from a quiet baseline.
Point three will not change soon. Every sensor deployed, every transmission made and every piece of machinery run provides a counter detection opportunity. A good submariner will use every bit of noise generated to its advantage and use it for targeting. A quiet ship reduces the range of detection and in turn, reduces the effective time the submarine has to generate a firing solution and attack. Being a quiet platform makes the submariner’s job harder and may make the difference between being on the wrong end of a heavyweight torpedo and making it home safely. In task group operations, one loud ship will increase the risk to all platforms. Noise Monitoring needs to be a high priority at the task group level to be effective. Cutting back on the noise quietening budget for one platform will decrease the ASW efficacy of the entire task group.
The strength of a task group is only as good as its weakest (or loudest) unit.
The last two points should be reason enough to make every effort to make your ship quiet. Noise awareness is a state of mind and a team game. Similar to the task group scenario, one noise short onboard will give away the platform. There is no such thing as nearly quiet enough or eliminating most of the problem noise sources. You are either quiet or you are not. It is everyone’s responsibility to ensure correct stowage for the sea and to report any machinery/platform issues that need to be rectified. On a platform at sea, all crew members share the risks associated with putting the ship or submarine in harm’s way. The junior chef onboard can have just as much to lose as the captain when things go bad in a big way. Everyone is responsible for noise awareness.
Nothing strengthens authority so much as silence.
- Leonardo Da Vinci
In summary, noise awareness remains important today and will need to be a priority in the future. As we look to adopt unmanned support to vessels the command and control aspects will need to be considered. The amount of data these types of sensors will be phenomenal, it will require a way to be transmitted to the mother and we will short change the capability by cutting corners on noise quietening. I would argue that although it is costly to invest in noise quietening from the beginning of the design process, in the long run (and in maintaining a potent anti-submarine threat), it represents an essential investment. Eliminating noise shorts post-build could potentially be a far more costly exercise.
With the sheer number of sophisticated submarines in our region and the stakes involved, lowering the overall noise generated by future platforms needs to be high up on the shopping list.
