Torpedo junction
Des torpilles russes très efficaces : info ou intox ?
Dans le domaine de l’armement sous-marin, les scientifiques se sont longtemps heurtés à un problème : comment augmenter la vitesse des torpilles pour qu’elles aillent plus vite que leur cible, dans un milieu où les frottements sont importants ? Des chercheurs russes pourraient bien avoir trouvé la solution, mais s’agit-il d’une information sérieuse ou d’un leurre ?
When introduced 40 years ago, the Soviet Shkval (“Squall”) torpedo was hailed as an “aircraft-carrier killer” because its speed, more than 370kph (200 knots), was four times that of any American rival. The claim was premature. Problems with its design meant Shkval turned out to be less threatening than hoped (or, from a NATO point of view, less dangerous than feared), even though it is still made and deployed. But supercavitation, the principle upon which its speed depends, has continued
to intrigue torpedo designers. Now, noises coming out of the Soviet Union’s successor, Russia, are leading some in the West to worry that the country’s engineers have cracked it.
2. Bubbles of vapour (ie, cavities) form in water wherever there is low pressure, such as on the trailing edges of propeller blades. For engineers, this is usually a problem. In the case of propellers, the cavities erode the blades’ substance. Shkval’s designers, however, sought, by amplifying the phenomenon, to make use of it. They gave their weapon a blunt nose fitted with a flat disc that creates a circular trailing edge as the torpedo moves forward. They also gave it a rocket motor to accelerate it to a speed fast enough for that edge to create a cavity consisting of a single, giant bubble which envelopes the entire torpedo except for the steering fins.
3. The result is that most of the torpedo experiences no hydrodynamic drag, greatly enhancing its potential velocity. To take advantage of this it is propelled, when the booster rocket runs out of oomph, by a hy-
to seek, sought, sought chercher / to make, made, made use of se servir/profiter de / weapon arme, armement / blunt non aiguisé/ici, pointu (aussi, brut) / to be fitted with être équipé/muni de / flat plat, non pointu / as alors que; ici, quand / rocket (de) fusée / enough suffisamment / steering fin ailette de guidage/"directionnelle". 3. to experience ici, subir / drag force de résistance/ici, traînée / greatly grandement, considérablement, nettement / to enhance améliorer; ici, augmenter / velocity vitesse / to take, took, taken advantage of tirer profit de / to propel propulser, lancer / booster (rocket) fusée porteuse, lanceur / to run, ran, run out of manquer/être à court de / oomph "peps"; ici, carburant /
drojet—a motor fuelled by a material, such as magnesium, that will burn in water.
PROBLEMS
4. Shkval’s problems are threefold. First, it has a short range—around 15km compared with around 50km for America’s principal submarine-launched torpedo, the Mk 48. Second, the hydrojet is noisy, so opponents can hear the weapon coming. Third, it cannot track its target. Most torpedoes use sonar to home in on the ship they are intended to sink. Because Shkval travels inside a bubble, any sonar needs to be mounted on the cavitation disc, which is too small for the purpose. In addition, returning sonar pings would be drowned out by the hydrojet’s noise. As a consequence, Shkval’s only guidance is an autopilot which steers it towards the place where its target was located at the moment of launch, in the hope that the target has not moved.
5. These deficiencies have not stopped Western countries trying to build supercavitating torpedoes of their own. Diehl, a German firm, announced a programme for such a weapon, Barracuda, in 2004. In 2006 General Dynamics, a big American firm, was commissioned to look into the matter (though its brief did not include the word “torpedo”, referring only to an “undersea transport”) by the country’s Defence Advanced Research Projects Agency. Barracuda was never completed. General Dynamics’ project was shelved after a year. American naval research into supercavitation in general ended in 2012, though which particular problems proved insurmountable has never been revealed.
6. Russia, though, has not given up on the idea. In October 2016 plans emerged for a new supercavitating torpedo, Khishchnik (“Predator”). Few details have been released, except that the work is being carried out by Elektropribor, a design bureau specialising in highprecision systems for submarines. Combining a General Dynamics-style sonar with a better motor could, however, result in a weapon that the world’s navies would truly have to fear.
7. Such a motor is possible, according to Georgiy Savchenko of the Institute of Hydromechanics at Ukraine’s National Academy of Sciences. His supercavitation-research group estimates that with the right fuel (perhaps lithium, which packs more energy per kilogram than magnesium) a new torpedo could have ten times the range of Shkval. It would still be noisy, but, added to its speed, such a combination of range and tracking ability would make it hard to evade. Moreover, there is no theoretical reason why Khishchnik should not travel quite a lot faster than Shkval does. In laboratory tests, supercavitating projectiles have clocked more than 5,000kph.
KANYON DIABOLO
8. The supercavitating design being developed for Khishchnik might also feed into the Kanyon project, a giant nuclear-powered torpedo with a nuclear warhead that is intended to attack coastal targets. In what was either a deliberate leak or a piece of disinformation, this project was revealed to the world in 2015 during a televised meeting between Vladimir Putin, Russia’s president, and senior officers of the country’s armed forces. The camera, looking over one of these officers’ shoulders, gave a picture of plans for the putative device, annotated with helpful information such as “speed of travel—185kph”. The leaked design did not appear to use supercavitation—but if Kanyon is genuine, then thoughts of adding it cannot have escaped its designers. Even if Kanyon is smoke and mirrors, though, Khishchnik seems real enough. Perhaps, this time, aircraft-carrier skippers should be worried.