Why did US Navy WW2 torpedoes detonate at the end of their run?

score:35

Accepted answer

To prevent torpedoes from becoming a navigational hazard in the event of a miss the 1907 Hague Convention VIII had a section on mines.

Once a torpedo was out of fuel it was buoyant. Therefore any torpedo that missed its mark (which was a lot!) would become a random and deadly hazard to navigation. The easiest solution to this was to detonate the torps at the end of run when the fuel ran out.

In later models, they were built to automatically explode when the fuel was exhausted. US submarine commanders speak of hearing 'end-or-run' explosions which told them their torpedo had missed.

This may be designed as safety system, causing the torpedo to self-detonate after a certain radius.

Upvote:1

another reason beside safety issues: suppose a torpedo misses. Then it keeps floating, sinks in shallow water, or reaches land and is beached. If it does not go BOOM the enemy might recover it!

Even if there are no tech secrets, the enemy might learn about the state of your industry by checking the quality of components and assembly. Or deduce something about your logistics chain or unit positions by examining part numbers or markings.

It is interesting e.g., how the allies deduced the number of Panther tanks produced by analyzing sequential part numbers. Or how today South Koreans analyse the wreckage of North Korean missiles and subs.

Deny information to the enemy: if it is ours, and the enemy might get it, them GO BOOM! It will make harder for them to deduce information (albeit not impossible, as in the Korean example above)

For the same reason, if a damaged plane was forced to land where the enemy could get it, friendly planes would attack it (after making sure the pilot was not there)

Upvote:2

Kriegsmarine had two torpedoignitors with relevant devices:

  • Pistole 4c EDS (Pi4c EDS)
  • Pistole 4d SZE (Pi4d SZE)

EDS = Endstreckendetonierersicherung ("safety against end-of-run-detonation") SZE = Selbstzerstörungseinrichtung ("selfdestruction-device")

The Pi4c EDS was only used in Type Ke and Type Ke1 warheads with the passive acoustic seeeking G7e(TV) "Zaunkönig" and G7e(TXI) "Zaunkönig II" torpedoes (only used from submarines).

The Pi4d SZE was only used in Type Ke and Type Ke1 warheads with the G7e(TVa) torpedo - a specially adapted variant of the "Zaunkönig" for S-Boote (ie MTB's).

EDS would permit detonation of the warhead of a torpedo hitting the seabed after missing the target, to avoid giving away the presence of a submarine in the area. SZE was primary a device incorporated to prevent new and advanced technology falling into enemy hands (the S-boote operated close to coastlines in shallow waters with much higher risk of missing torpedoes ending up running ashore etc).

Sources: Various Kriegsmarine handbooks, including "Technische Dienstvorschrift Nr. 194 Torpedo-Kopf-Pistolen-Tabelle" (Kriegsmarine, 1944) and "Torpedo Zünder der Deutschen Marine von 1914 bis 1968 mit historischen Rückblick, Band 1" (Bundesmarine, ca 1970).

Upvote:22

The reason is simple: nobody wants an uncontrolled explosive device floating around. You yourself, or someone else, other then your enemy may later accidentally hit it. For the same reasons all anti-aircraft shells explode at the end of their trajectory: who knows what they may hit on the ground.

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