Why are torpedoes considered can’t-miss weapons? It’s because of two attributes of modern torpedoes:
- Speed – Modern torpedoes have sprint speeds greater than ships have. Thus, it’s not possible to outrun one. It is possible to outlast one if the detection occurs early and the geometry-range is favorable but that’s unlikely unless the sub launches from the edge of the envelope.
- Guidance – Modern torpedoes have self-contained sonar sensors and wake homing guidance. Thus, unlike during WWII where simply turning parallel to the torpedo was generally sufficient to produce a miss, maneuvering to avoid a torpedo will be far less likely to succeed.
Or so the story goes …
The speed/range/geometry issue is straightforward but what about the guidance? Does it really work? As I said, there is no data to guide us (sorry, that was unintentional). Commentators attribute near magical, perfect performance to torpedo guidance systems but are they really that good? Consider …
Air-to-air missile guidance systems certainly aren’t perfect and, historically, have achieved something in the vicinity of 20% success rate in combat. Why would we think torpedo guidance systems are so much better?
Laser guided bombs are around 80% effective under perfect conditions and as low as 50% in scenarios with adverse weather or less than perfect release geometry. Why would we think torpedo guidance systems are so much better?
Surface-to-air AAW guided missiles have a historic success rate of 5%-20%. Why would we think torpedo guidance systems are so much better?
While none of those systems use the same sensors and guidance systems as a torpedo, making direct comparisons invalid, we can note that every guidance system tried has proven to be far less effective than advertised. There is no reason to believe that sonar and wake homing sensor/guidance systems have some kind of magic performance that no other guidance system has. It is far more likely that sonars and wake homing suffer from the same poor performance that every other system does.
While we have no direct body of data to work with, we do have a few related bits of evidence that we can draw inferences from.
The US Navy anti-torpedo torpedo weapon system was a failure in actual use conditions. The culprit was the sonar systems which produced so many false alarms as to render the system useless. That being the case, why would we think that a torpedo with it’s small on-board sonar won’t be subject to the same kinds of false signals?
During the Falklands conflict, the Royal Navy’s submarine Conqueror fired three 21 inch Mk 8 mod 4 torpedoes (conventional, non-guided). The sub carried modern Mk 24 Tigerfish homing torpedoes but doubted their reliability. NavWeaps website offers some insight:
… in a test performed in 1982 immediately after the Falklands War, two out of five Mod 1 [ed. Mk 24 Tigerfish] torpedoes fired at a target hulk failed to function because of bad batteries and none of the others even hit the target. This unreliability was well known in the Fleet, which is why ancient Mark 8 torpedoes were used to sink the Argentine cruiser General Belgrano. (1)
This finding introduces yet another source of torpedo failure: mechanical/electrical. Torpedoes are just like any other piece of machinery. They have a mechanical/electrical failure rate. We’ve seen Tomahawk missiles fail to launch or fail immediately upon launch. We’ve seen Standard missiles explode during launch (rocket motor failure). We’ve seen missiles drop off aircraft rails and never ignite. And so on. Why would we think torpedoes are mechanically/electrically any better?
All we have is circumstantial evidence but it’s pretty convincing. Torpedoes are nowhere near the inexorable killing machines that commentators make them out to be. The reality is that torpedoes will simply fail to acquire targets, miss targets, fail mechanically/electrically, suffer from false signals, and generally fail to hit their targets to a large degree. Throw in torpedo defenses such as acoustic decoys, Nixie-like tails, aggressive maneuvering by the target, etc. and the success rate of torpedoes will be even lower.
All of this analysis is not to say that torpedoes aren’t a serious threat. They are. A torpedo, if it can hit its target, is a powerful weapon.
The conclusion we should be taking from this is that while the torpedo threat is serious, it does not preclude surface ships from operating and surviving during war, despite the many claims to the contrary.
This also suggests that the Navy should be conducting extensive torpedo performance tests. Have a sub fire live torpedoes – with the warheads removed, of course – at ships and see what actually happens. Yes, we may get some dented hulls but the chance to gather actual performance data and develop real defensive tactics is priceless.
It’s peacetime. Now is the time to find out what works and what doesn’t.
(1)NavWeaps website, “Torpedoes of the United Kingdom/Britain”, Home / Weapons / Torpedoes / United Kingdom/Britain / Post-World War II,http://www.navweaps.com/Weapons/WTBR_PostWWII.php#prof