Did Japan develop its own version of radio fuzes at the end of the war?

[msxyz]

I recently found in an obscure web page a reference to a workable radio fuze developed in Japan before the end of the war. I would post here the link, but following a crash and update of the browser, the cache is gone and I cannot find it again for the love of God!

Supposedly, this fuze didn't work in the same way as the allied one (radio waves reflected by target) but it was simply a remotely activated detonator (thus a radio receiver), that spared the artillery men the task of setting the fuze in advance before feeding the round to the gun; another advantage should have been that the shell could be made to explode closer to the target (how? Doubt a tracer could suffice). These experimental fuzes were said to be operationally employed only by the one-of-a-kind 155mm AA artillery outside of Tokio that was capable of bringing down with ease a B-29 even when flying at 30000'. The page went on to say that US soldiers recovered a whole cache of them but, after having judged them inferior to their own VTs, they destroyed them quickly in order not to share them with the Soviets.

Can anybody confirm that this story is true or is just some made up trash?

 

[special ed]

A radio receiver of the time would most likely have used vacuum tubes (valves to some) and I would be curious how they would stand being shot out of a cannon.

 

[Shinpachi]

Anti-impact metal cased vacuum tubes were developed by several Japanese electric makers like Tokyo Electric Co Ltd and NEC or Sumitomo for the navy by 1938. I don't hear that they were provided for such proximity fuse but RC missile like "Funryu".

Tokyo Electric aka Mazda tubes

Source: 真空管[全金属真空管]物語

 

[special ed]

Thank you. We could not learn these things without you.

 

[yosimitesam]

Another interesting Japanese development took place near the end of the war. They apparently developed a 'proximity fuse' for aerial bombs using a pulsing photo-electric device. The image below is a summary paragraph from the US Naval Technical Mission to Japan just after the war ended. The entire document is uploaded, also. I couldn't find any information on whether the US thought the idea worth pursuing.

 

[R Leonard]

The National Defense Research program looked at it.

Image 7 of Summary, photoelectric fuzes and miscellaneous projects.

 

[msxyz]

A radio receiver of the time would most likely have used vacuum tubes (valves to some) and I would be curious how they would stand being shot out of a cannon.

The same way the allies solved the problem with VT: through miniaturization (so that the inertia of the components was reduced to the point that they were capable of sustaining a strong acceleration without breaking) and developing ways to cushion them (wax, dielectric dense oil, etc...)

Anti-impact metal cased vacuum tubes were developed by several Japanese electric makers like Tokyo Electric Co Ltd and NEC or Sumitomo for the navy by 1938. I don't hear that they were provided for such proximity fuse but RC missile like "Funryu".

"Rugged" valves like that were developed in most countries before the war. They traded the external glass bulb with metal or hard ceramic. Metal case was also cheaper, but it was harder to create a lasting seal at the base (thermal expansion is a bitch when you have to mate two different materials). On the plus side, using a metal exterior, the anode of the valve could be the outer shell itself making easier to dissipate the heat.

However, valves like those in the picture may have survived the concussion of being inside a tank when hit by a shell, but not the extreme shock of being accelerated by a cannon.

 

[Peter Gunn]

Interesting stuff, I had seen/read rumblings about Japanese VT type fuzes over the years and admit I never really looked into it. Usually when I see a description like:

These experimental fuzes were said to be operationally employed only by the one-of-a-kind 155mm AA artillery outside of Tokio that was capable of bringing down with ease a B-29 even when flying at 30000'.

My BS meter shoots to the top, no reflection on you msxyz, I realize you were quoting another source, it's when those types of folks write stuff like that I figure it's bunk.

 

[msxyz]

My BS meter shoots to the top, no reflection on you msxyz, I realize you were quoting another source, it's when those types of folks write stuff like that I figure it's bunk.

To me, it was not the 155mm AA (it could have been a typo; small numbers of a 'Type 5 15cm' AA guns were deployed around Tokyo late in the war) but the fate of those fuzes that made me come here to ask for a confirmation. Even supposing the US troops destroyed them, a mention somewhere in the various reports should exist. Also a remotely detonated fuze doesn't seem really something you're desperately trying to hide from the Soviet Union (not to mention is should be quite easy to jam them once you learn the frequency).

 

[R Leonard]

From the NDRC report, page 18:

"There are, however, two major limitations to a simple passive photoelectric fuze: (1) since the sun is used as a source of energy, operational use is restricted to daytime, and (2) the sun is also a target in the sense that if the detector of the fuze "sees" the sun directly, malfunction of the fuze may occur.
These two limitations were recognized in the beginning and led to termination of the work only after more difficult designs (radio) had proved practicable for proximity operation.
An infrared fuze would not be subject to the first limitation above but would be affected by the second. For this reason, infrared designs based on rapid, sensitive detectors developed by Division 16, NDRC, were abandoned after brief consideration. The practicability of available radio fuzes was also a major factor in the abandonment."

As there are only so many ways to skin that cat, one might presume the Japanese faced the same problems.

 

[Shinpachi]

Another interesting Japanese development took place near the end of the war. They apparently developed a 'proximity fuse' for aerial bombs using a pulsing photo-electric device. The image below is a summary paragraph from the US Naval Technical Mission to Japan just after the war ended. The entire document is uploaded, also. I couldn't find any information on whether the US thought the idea worth pursuing.

View attachment 623688

Your data is very helpful to id parts of the Type 3 fuse. Thanks.

Source: twitter.com/hashtag/%E5%85%89%E9%9B%BB%E7%AE%A1

Source: 真空管 マツダUY-6301 3＋1 未使用 - ヤフオク!


XB767A

Source: 真空管[サイラトロン]物語

 

[yosimitesam]

From the NDRC report, page 18:

"There are, however, two major limitations to a simple passive photoelectric fuze: (1) since the sun is used as a source of energy, operational use is restricted to daytime, and (2) the sun is also a target in the sense that if the detector of the fuze "sees" the sun directly, malfunction of the fuze may occur.
These two limitations were recognized in the beginning and led to termination of the work only after more difficult designs (radio) had proved practicable for proximity operation.
An infrared fuze would not be subject to the first limitation above but would be affected by the second. For this reason, infrared designs based on rapid, sensitive detectors developed by Division 16, NDRC, were abandoned after brief consideration. The practicability of available radio fuzes was also a major factor in the abandonment."

As there are only so many ways to skin that cat, one might presume the Japanese faced the same problems.

The cleverness in the Japanese device, as I see it, was to use the pulsing light source and to drive this source in a simple (electronically speaking) manner with a perforated wheel and electric motor. The fuse required a much bigger battery than a 'receiver only' daylight device, but it eliminated the effect of the sun or an unfortunate reflection from something sunlit setting off the mechanism early. Of course, they had to develop a new thyratron tube and new circuitry, but once these things were done the fuse would work day and night and have a low early-activation rate. Of course, the fuse (from what I can tell from the poor photos) is much larger than a hypothetical receiver-only device, but this is not such a big problem with a 250kg or 800kg bomb as opposed to an anti-aircraft rocket or high-velocity shell. The device stands high on my 'simple and clever' scale of devices invented in that era.